715,868 results on '"Robert, J"'
Search Results
52. Social and Emotional Learning in U.S. Schools: Findings from CASEL's Nationwide Policy Scan and the American Teacher Panel and American School Leader Panel Surveys. Research Report. RR-A1822-2
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RAND Education and Labor, Collaborative for Academic, Social, and Emotional Learning (CASEL), Alexandra Skoog-Hoffman, Asher A. Miller, Rista C. Plate, Duncan C. Meyers, Andrew S. Tucker, Gabrielle Meyers, Melissa Kay Diliberti, Heather L. Schwartz, Megan Kuhfeld, Robert J. Jagers, Lakeisha Steele, and Justina Schlund
- Abstract
A large body of evidence indicates that well-implemented social and emotional learning (SEL) programs improve academic, social, and emotional outcomes for students and educators. Education policy has the potential to influence the high-quality implementation of SEL, from the school district, to the school, to the classroom. Before and during the coronavirus disease 2019 pandemic, U.S. states enacted supportive policies and conditions to promote SEL in schools. However, curricula that foster the development of social and emotional competences have been one of many controversies about the instructional content and instructional practices schools should use to teach students. Thus, legislators in nine states have proposed bills to prohibit or inhibit SEL instruction in kindergarten through grade 12 (K-12) schools. In this report, the authors investigate whether states' SEL policies (for and against) are associated with the implementation of SEL by K-12 schools, as reported by teachers and principals. In their approach, the authors merge the survey data they collected from educators with the results of the Collaborative for Academic, Social, and Emotional Learning's (CASEL's) nationwide scan of each state's and the District of Columbia's SEL-relevant policies and conditions. The authors also study whether SEL implementation is correlated with two teacher-reported indicators of positive student experience: supportive climate and student interest in learning. The authors' findings show whether state policymakers' SEL-related policies (including legislation and guidance) connect to schools' on-the-ground decisions and implementation, as reported by principals and teachers.
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- 2024
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53. Wrong Suffix: Gifted Education for Career Choice Should Focus on 'Gift'ing'' Rather than on Being 'Gift'ed''
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Robert J. Sternberg
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Gifted education should focus on gifting rather than on being gifted. That is, it should focus on what one offers from one's gifts, not just on what gifts a person has, one way or another, accumulated. Gifted individuals should consider choosing careers that are a good fit to them, that enable them to give back, and that give them a sense of meaning in their life. They should be ready to move on if their career choice proves to be mistaken, or no longer to be a fit. They should avoid temptations brought on by outside pressures to choose careers that may be much less than fulfilling. In the end, what matters most is one's passion and motivation for a career rather than grades, test scores, or external pressures.
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- 2024
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54. Landscape simplification leads to loss of plant–pollinator interaction diversity and flower visitation frequency despite buffering by abundant generalist pollinators
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Maurer, Corina, Martínez-Núñez, Carlos, Dominik, Christophe, Heuschele, Jonna, Liu, Yicong, Neumann, Peter, Paxton, Robert J., Pellissier, Loïc, Proesmans, Willem, Schweiger, Oliver, Szentgyörgyi, Hajnalka, Vanbergen, Adam, and Albrecht, Matthias
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- 2024
55. Signatures of polarized chiral spin disproportionation in rare earth nickelates
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Li, Jiarui, Green, Robert J., Domínguez, Claribel, Levitan, Abraham, Tseng, Yi, Catalano, Sara, Fowlie, Jennifer, Sutarto, Ronny, Rodolakis, Fanny, Korol, Lucas, McChesney, Jessica L., Freeland, John W., Van der Marel, Dirk, Gibert, Marta, and Comin, Riccardo
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
In rare earth nickelates (RENiO$_3$), electron-lattice coupling drives a concurrent metal-to-insulator and bond disproportionation phase transition whose microscopic origin has long been the subject of active debate. Of several proposed mechanisms, here we test the hypothesis that pairs of self-doped ligand holes spatially condense to provide local spin moments that are antiferromagnetically coupled to Ni spins. These singlet-like states provide a basis for long-range bond and spiral spin order. Using magnetic resonant X-ray scattering on NdNiO$_3$ thin films, we observe the chiral nature of the spin-disproportionated state, with spin spirals propagating along the crystallographic (101)$_\mathrm{ortho}$ direction. These spin spirals are found to preferentially couple to X-ray helicity, establishing the presence of a hitherto-unobserved macroscopic chirality. The presence of this chiral magnetic configuration suggests a potential multiferroic coupling between the noncollinear magnetic arrangement and improper ferroelectric behavior as observed in prior studies on NdNiO$_3$ (101)$_\mathrm{ortho}$ films and RENiO$_3$ single crystals. Experimentally constrained theoretical double-cluster calculations confirm the presence of an energetically stable spin-disproportionated state with Zhang-Rice singlet-like combinations of Ni and ligand moments., Comment: 6 pages, 4 figures
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- 2024
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56. The FLAMINGO Project: An assessment of the systematic errors in the predictions of models for galaxy cluster counts used to infer cosmological parameters
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Kugel, Roi, Schaye, Joop, Schaller, Matthieu, Moreno, Victor J. Forouhar, and McGibbon, Robert J.
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Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Galaxy cluster counts have historically been important for the measurement of cosmological parameters and upcoming surveys will greatly reduce the statistical errors. To exploit the potential of current and future cluster surveys, theoretical uncertainties on the predicted abundance must be smaller than the statistical errors. Models used to predict cluster counts typically combine a model for the dark matter only (DMO) halo mass function (HMF) with an observable - mass relation that is assumed to be a power-law with lognormal scatter. We use the FLAMINGO suite of cosmological hydrodynamical simulations to quantify the biases in the cluster counts and cosmological parameters resulting from the different ingredients of conventional models. For the observable mass proxy we focus on the Compton-Y parameter quantifying the thermal Sunyaev-Zel'dovich effect, which is expected to result in cluster samples that are relatively close to mass-selected samples. We construct three mock surveys based on existing (Planck and SPT) and upcoming (Simons Observatory) surveys. We ignore measurement uncertainties and compare the biases in the counts and inferred cosmological parameters to each survey's Poisson errors. We find that widely used models for the DMO HMF differ significantly from each other and from the DMO version of FLAMINGO, leading to significant biases for all three surveys. For upcoming surveys, dramatic improvements are needed for all additional model ingredients, i.e. the functional forms of the fits to the observable-mass scaling relation and the associated scatter, the priors on the scaling relation and the prior on baryonic effects associated with feedback processes on the HMF., Comment: 17 pages, 8 figures. Submitted to MNRAS
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- 2024
57. Large-Scale Multi-omic Biosequence Transformers for Modeling Peptide-Nucleotide Interactions
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Chen, Sully F., Steele, Robert J., Lemeneh, Beakal, Lad, Shivanand P., and Oermann, Eric
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Computer Science - Machine Learning ,Quantitative Biology - Biomolecules - Abstract
The transformer architecture has revolutionized bioinformatics and driven progress in the understanding and prediction of the properties of biomolecules. Almost all research on large-scale biosequence transformers has focused on one domain at a time (single-omic), usually nucleotides or peptides. These models have seen incredible success in downstream tasks in each domain and have achieved particularly noteworthy breakthroughs in sequences of peptides and structural modeling. However, these single-omic models are naturally incapable of modeling multi-omic tasks, one of the most biologically critical being nucleotide-peptide interactions. We present our work training the first multi-omic nucleotide-peptide foundation models. We show that these multi-omic models (MOMs) can learn joint representations between various single-omic distributions that are emergently consistent with the Central Dogma of molecular biology, despite only being trained on unlabeled biosequences. We further demonstrate that MOMs can be fine-tuned to achieve state-of-the-art results on peptide-nucleotide interaction tasks, namely predicting the change in Gibbs free energy ({\Delta}G) of the binding interaction between a given oligonucleotide and peptide, as well as the effect on this binding interaction due to mutations in the oligonucleotide sequence ({\Delta}{\Delta}G). Remarkably, we show that multi-omic biosequence transformers emergently learn useful structural information without any prior structural training, allowing us to predict which peptide residues are most involved in the peptide-nucleotide binding interaction. Lastly, we provide evidence that multi-omic biosequence models are non-inferior to foundation models trained on single-omics distributions, suggesting a more generalized or foundational approach to building these models., Comment: 27 pages, 5 figures
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- 2024
58. Benchmarking with Supernovae: A Performance Study of the FLASH Code
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Martin, Joshua, Feldman, Catherine, Siegmann, Eva, Curtis, Tony, Carlson, David, Coskun, Firat, Wood, Daniel, Gonzalez, Raul, Harrison, Robert J., and Calder, Alan C.
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Computer Science - Distributed, Parallel, and Cluster Computing ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
Astrophysical simulations are computation, memory, and thus energy intensive, thereby requiring new hardware advances for progress. Stony Brook University recently expanded its computing cluster "SeaWulf" with an addition of 94 new nodes featuring Intel Sapphire Rapids Xeon Max series CPUs. We present a performance and power efficiency study of this hardware performed with FLASH: a multi-scale, multi-physics, adaptive mesh-based software instrument. We extend this study to compare performance to that of Stony Brook's Ookami testbed which features ARM-based A64FX-700 processors, and SeaWulf's AMD EPYC Milan and Intel Skylake nodes. Our application is a stellar explosion known as a thermonuclear (Type Ia) supernova and for this 3D problem, FLASH includes operators for hydrodynamics, gravity, and nuclear burning, in addition to routines for the material equation of state. We perform a strong-scaling study with a 220 GB problem size to explore both single- and multi-node performance. Our study explores the performance of different MPI mappings and the distribution of processors across nodes. From these tests, we determined the optimal configuration to balance runtime and energy consumption for our application., Comment: Accepted to PEARC '24 (Practice and Experience in Advanced Research Computing)
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- 2024
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59. A nonlinear d'Alembert comparison theorem and causal differential calculus on metric measure spacetimes
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Beran, Tobias, Braun, Mathias, Calisti, Matteo, Gigli, Nicola, McCann, Robert J., Ohanyan, Argam, Rott, Felix, and Sämann, Clemens
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Mathematics - Differential Geometry ,General Relativity and Quantum Cosmology ,Mathematical Physics ,Mathematics - Metric Geometry ,51K10, 83C75 (Primary), 35J92, 35Q75, 49Q22, 53C21, 53C50 (Secondary) - Abstract
We introduce a variational first-order Sobolev calculus on metric measure spacetimes. The key object is the maximal weak subslope of an arbitrary causal function, which plays the role of the (Lorentzian) modulus of its differential. It is shown to satisfy certain chain and Leibniz rules, certify a locality property, and be compatible with its smooth analog. In this setup, we propose a quadraticity condition termed infinitesimal Minkowskianity, which singles out genuinely Lorentzian structures among Lorentz-Finsler spacetimes. Moreover, we establish a comparison theorem for a nonlinear yet elliptic $p$-d'Alembertian in a weak form under the timelike measure contraction property. As a particular case, this extends Eschenburg's classical estimate past the timelike cut locus., Comment: 132 pages. Comments welcome
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- 2024
60. Easy-Plane Alignment of Anisotropic Biofluid Crystals in a Magnetic Field: Implications for Rod Orientation
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Deissler, Robert J. and Brown, Robert
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Physics - Biological Physics - Abstract
We study the orientation in a uniform magnetic field of rod-like anisotropic biofluid crystals with an easy plane that makes an oblique angle with the crystal's c-axis. For a sufficiently strong field, these crystalline rods orient themselves such that the crystal's easy plane is parallel to the magnetic field, the rod's direction being defined as the direction of the crystal's c-axis. As the rod rotates about the crystal's hard axis there will therefore be a range of angles that the rod makes with the magnetic field. We detail this behavior by first providing illustrations of hemozoin crystals at various orientations. These illustrations clearly demonstrate that the orientation angle that the crystalline rod makes with respect to the magnetic field varies from about 30 deg to 150 deg. We also derive an analytical expression for the probability density function for the orientation angle. We find that the orientation angles are not uniformly distributed between the limits of 30 deg and 150 deg, but rather tend to cluster near these limits. This suggests experimental tests and addresses confusion about the rod orientation found in past literature. The relevance to other anisotropic biofluid crystals, such as those produced by gout, is also discussed., Comment: 12 pages, 6 figures
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- 2024
61. Teleparallel Geometry with Spherical Symmetry: The diagonal and proper frames
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Hoogen, Robert J. van den and Forance, Hudson X.
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General Relativity and Quantum Cosmology ,Mathematical Physics ,Mathematics - Differential Geometry - Abstract
We present the proper co-frame and its corresponding (diagonal) co-frame/spin connection pair for spherically symmetric geometries which can be used as an initial ansatz in any theory of teleparallel gravity. The Lorentz transformation facilitating the move from one co-frame to the other is also presented in factored form. The factored form also illustrates the nature of the two degrees of freedom found in the spin connection. The choice of coordinates in restricting the number of arbitrary functions is also presented. Beginning with a thorough presentation of teleparallel gravity using the metric affine gauge theory approach and concentrating on f(T) teleparallel gravity, we express the field equations in the diagonal co-frame. We argue that the choice of diagonal co-frame may be more advantageous over the proper co-frame choice. Finally, assuming one additional symmetry, we restrict ourselves to the Kantowski-Sachs tele-parallel geometries, and determine some solutions., Comment: 28 pages
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- 2024
62. Eliminating Surface Oxides of Superconducting Circuits with Noble Metal Encapsulation
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Chang, Ray D., Shumiya, Nana, McLellan, Russell A., Zhang, Yifan, Bland, Matthew P., Bahrami, Faranak, Mun, Junsik, Zhou, Chenyu, Kisslinger, Kim, Cheng, Guangming, Pakpour-Tabrizi, Alexander C., Yao, Nan, Zhu, Yimei, Liu, Mingzhao, Cava, Robert J., Gopalakrishnan, Sarang, Houck, Andrew A., and de Leon, Nathalie P.
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Condensed Matter - Superconductivity ,Condensed Matter - Materials Science ,Quantum Physics - Abstract
The lifetime of superconducting qubits is limited by dielectric loss, and a major source of dielectric loss is the native oxide present at the surface of the superconducting metal. Specifically, tantalum-based superconducting qubits have been demonstrated with record lifetimes, but a major source of loss is the presence of two-level systems (TLSs) in the surface tantalum oxide. Here, we demonstrate a strategy for avoiding oxide formation by encapsulating the tantalum with noble metals that do not form native oxide. By depositing a few nanometers of Au or AuPd alloy before breaking vacuum, we completely suppress tantalum oxide formation. Microwave loss measurements of superconducting resonators reveal that the noble metal is proximitized, with a superconducting gap over 80% of the bare tantalum at thicknesses where the oxide is fully suppressed. We find that losses in resonators fabricated by subtractive etching are dominated by oxides on the sidewalls, suggesting total surface encapsulation by additive fabrication as a promising strategy for eliminating surface oxide TLS loss in superconducting qubits.
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- 2024
63. Time-resolved pairing gap spectroscopy in a quantum simulator of fermionic superfluidity inside an optical cavity
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Young, Dylan J., Song, Eric Yilun, Chu, Anjun, Barberena, Diego, Niu, Zhijing, Schäfer, Vera M., Lewis-Swan, Robert J., Rey, Ana Maria, and Thompson, James K.
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Condensed Matter - Quantum Gases ,Physics - Atomic Physics ,Quantum Physics - Abstract
We use an ensemble of laser-cooled strontium atoms in a high-finesse cavity to cleanly emulate the technique of rf spectroscopy employed in studies of BEC-BCS physics in fermionic superfluids of degenerate cold gases. Here, we leverage the multilevel internal structure of the atoms to study the physics of Cooper pair breaking in this system. In doing so, we observe and distinguish the properties of two distinct many-body gaps, the BCS pairing gap and the spectral gap, using nondestructive readout techniques. The latter is found to depend on the populations of the internal atomic states, reflecting the chemical potential dependence predicted in fermionic superfluids. This work opens the path for more fully exploiting the rich internal structure of atoms in cavity QED emulators to study both analogous systems and also more exotic states yet to be realized., Comment: Main Text with Supplementary Material, 15 pages, 5 figures
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- 2024
64. Multi-Task Multi-Fidelity Learning of Properties for Energetic Materials
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Appleton, Robert J., Klinger, Daniel, Lee, Brian H., Taylor, Michael, Kim, Sohee, Blankenship, Samuel, Barnes, Brian C., Son, Steven F., and Strachan, Alejandro
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Computer Science - Machine Learning ,Condensed Matter - Materials Science - Abstract
Data science and artificial intelligence are playing an increasingly important role in the physical sciences. Unfortunately, in the field of energetic materials data scarcity limits the accuracy and even applicability of ML tools. To address data limitations, we compiled multi-modal data: both experimental and computational results for several properties. We find that multi-task neural networks can learn from multi-modal data and outperform single-task models trained for specific properties. As expected, the improvement is more significant for data-scarce properties. These models are trained using descriptors built from simple molecular information and can be readily applied for large-scale materials screening to explore multiple properties simultaneously. This approach is widely applicable to fields outside energetic materials., Comment: 16 pages, 4 figures, 2 tables
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- 2024
65. Deciphering Solar Magnetic Activity: Some (Unpopular) Thoughts On the Coupling of the Sun's 'Weather' and 'Climate'
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McIntosh, Scott W. and Leamon, Robert J.
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Astrophysics - Solar and Stellar Astrophysics ,Physics - Space Physics - Abstract
The Sun exhibits episodic surges of magnetic activity across a range of temporal and spatial scales, the most prominent of which is the 11-ish year modulation of sunspot production. Beside the ~170 (min to max) decadal variation in sunspot production there is a less-explored quasi-annual variation in the range of 25-50 sunspots/year in magnitude. In addition, there is there is a slower, ~80 year period, 10-50 variation in the sunspot number, that is commonly referred to as the 'Gleissberg Cycle.' Using a suite of contemporary and historical observations we will illustrate these elements of our star's episodic behavior and present a hypothesis that may provide a consistent physical link between the observed 'climatic', 'decadal' and 'seasonal' magnetic variation of our star., Comment: 18 pages, 8 figures
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- 2024
66. Coulomb confinement in the Hamiltonian limit
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Dawid, Sebastian M., Smith, Wyatt A., Rodas, Arkaitz, Perry, Robert J., Fernández-Ramírez, César, Swanson, Eric S., and Szczepaniak, Adam P.
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High Energy Physics - Lattice ,Nuclear Theory - Abstract
The Gribov--Zwanziger scenario attributes the phenomenon of confinement to the instantaneous interaction term in the QCD Hamiltonian in the Coulomb gauge. For a static quark-antiquark pair, it leads to a potential energy that increases linearly with the distance between them. Lattice studies of the SU(2) Yang--Mills theory determined the corresponding (Coulomb) string tension for sources in the fundamental representation, $\sigma_{C}$, to be about three times larger than the Wilson loop string tension, $\sigma_F$. It is far above the Zwanziger variational bound, $\sigma_C \geq \sigma_F$. We argue that the value established in the literature is artificially inflated. We examine the lattice definition of the instantaneous potential, find the source of the string tension's enhancement, and perform its improved determination in SU(2) lattice gauge theory. We report our conservative estimate for the value of the Coulomb string tension as $\sigma_C/\sigma_F = 2.0 \pm 0.4$ and discuss its phenomenological implications., Comment: 13 pages, 6 figures
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- 2024
67. Dynamic factor analysis for sparse and irregular longitudinal data: an application to metabolite measurements in a COVID-19 study
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Cai, Jiachen, Goudie, Robert J. B., and Tom, Brian D. M.
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Statistics - Methodology ,Statistics - Computation - Abstract
It is of scientific interest to identify essential biomarkers in biological processes underlying diseases to facilitate precision medicine. Factor analysis (FA) has long been used to address this goal: by assuming latent biological pathways drive the activity of measurable biomarkers, a biomarker is more influential if its absolute factor loading is larger. Although correlation between biomarkers has been properly handled under this framework, correlation between latent pathways are often overlooked, as one classical assumption in FA is the independence between factors. However, this assumption may not be realistic in the context of pathways, as existing biological knowledge suggests that pathways interact with one another rather than functioning independently. Motivated by sparsely and irregularly collected longitudinal measurements of metabolites in a COVID-19 study of large sample size, we propose a dynamic factor analysis model that can account for the potential cross-correlations between pathways, through a multi-output Gaussian processes (MOGP) prior on the factor trajectories. To mitigate against overfitting caused by sparsity of longitudinal measurements, we introduce a roughness penalty upon MOGP hyperparameters and allow for non-zero mean functions. To estimate these hyperparameters, we develop a stochastic expectation maximization (StEM) algorithm that scales well to the large sample size. In our simulation studies, StEM leads across all sample sizes considered to a more accurate and stable estimate of the MOGP hyperparameters than a comparator algorithm used in previous research. Application to the motivating example identifies a kynurenine pathway that affects the clinical severity of patients with COVID-19. In particular, a novel biomarker taurine is discovered, which has been receiving increased attention clinically, yet its role was overlooked in a previous analysis.
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- 2024
68. Defects Enhance Stability in 12-fold Symmetric Soft-Matter Quasicrystals
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Ulugöl, Alptuğ, Hardeman, Robert J., Smallenburg, Frank, and Filion, Laura
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Condensed Matter - Soft Condensed Matter ,Condensed Matter - Materials Science ,Condensed Matter - Statistical Mechanics ,Physics - Computational Physics - Abstract
Quasicrystals are materials that exhibit long-range order without translational periodicity. In soft matter, the most commonly observed quasicrystal has 12-fold symmetry and consists of tilings made out of squares and triangles. Intriguingly, both in experiments and simulations, these tilings nearly always appear with many vacancy-related defects that are connected to an additional tile: a rhombus. In this letter, we explore the role of rhombus defects on the entropy of square-triangle 12-fold quasicrystals. We introduce a novel lattice-based Monte Carlo simulation method that uses open boundaries to allow the concentration of defects to fluctuate. Our simulations show that rhombus tiles significantly increase the configurational entropy of the quasicrystal phase, enhancing its stability. These findings highlight the critical role of defects in stabilizing soft-matter quasicrystals., Comment: 6 pages, 4 figures
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- 2024
69. Influence of disordered and anisotropic interactions on relaxation dynamics and propagation of correlations in tweezer arrays of Rydberg dipoles
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Mukherjee, Kaustav, Biedermann, Grant W., and Lewis-Swan, Robert J.
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Condensed Matter - Quantum Gases ,Condensed Matter - Disordered Systems and Neural Networks ,Quantum Physics - Abstract
We theoretically investigate the out-of-equilibrium dynamics of irregular one- and two-dimensional arrays of Rydberg dipoles featuring spatially anisotropic interactions. Starting from a collectively polarized initial state, we map out the dynamical phase diagram and identify a crossover between regimes of regular and anomalously slow relaxation of the initial collective order, that strongly depends on both the degree of interaction disorder and anisotropy. In addition, we find the regime of slow relaxation is characterized by a sub-ballistic propagation of correlations that remained confined to short distances even at long times. To explain our findings we develop an analytic model based on decoupled clusters of interacting dipoles that goes beyond prior theoretical works and enables us to identify multiple relaxation timescales. Our findings can be relevant for a wide variety of quantum science platforms naturally featuring disordered dipolar interactions, including polar molecules, frozen Rydberg gases and NV centers., Comment: 13 pages and 8 figures
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- 2024
70. On the Peril of Inferring Phytoplankton Properties from Remote-Sensing Observations
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Prochaska, J. Xavier and Frouin, Robert J.
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Physics - Atmospheric and Oceanic Physics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Since 1978, sensors on remote-sensing satellites have provided global, multi-band images at optical wavelengths to assess ocean color. In parallel, sophisticated radiative transfer models account for attenuation and emission by the Earth's atmosphere and ocean, thereby estimating the water-leaving radiance or and remote-sensing reflectance Rrs. From these Rrs measurements, estimates of the absorption and scattering by seawater are inferred. We emphasize an inherent, physical degeneracy in the radiative transfer equation that relates Rrs to the absorption and backscattering coefficients a and b_b, aka inherent optical properties (IOPs). Because Rrs depends solely on the ratio of b_b to a, meaning one cannot retrieve independent functions for the non-water IOPs, a_nw and b_bnw, without a priori knowledge. Moreover, water generally dominates scattering at blue wavelengths and absorption at red wavelengths, further limiting retrievals of IOPs in the presence of noise. We demonstrate that all previous and current multi-spectral satellite observations lack the statistical power to measure more than 3 parameters total to describe a_nw and b_bnw. Due to the ubiquitous exponential-like absorption by color dissolved organic matter at short wavelengths (l<500nm), multi-spectral Rrs do not permit the detection of phytoplankton absorption a_ph without very strict priors. Furthermore, such priors lead to biased and uncertain retrievals of a_ph. Hyperspectral observations may recover a 4th and possibly 5th parameter describing only one or two aspects of the complexity of a_ph. These results cast doubt on decades of literature on IOP retrievals, including estimates of phytoplankton growth and biomass. We further conclude that NASA/PACE will greatly enhance our ability to measure the phytoplankton biomass of Earth, but challenges remain in resolving the IOPs., Comment: submitted to Nature Communications; 30 pages, 20 figures (3 main)
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- 2024
71. Kov: Transferable and Naturalistic Black-Box LLM Attacks using Markov Decision Processes and Tree Search
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Moss, Robert J.
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Computer Science - Cryptography and Security ,Computer Science - Artificial Intelligence ,Computer Science - Computation and Language ,Computer Science - Machine Learning - Abstract
Eliciting harmful behavior from large language models (LLMs) is an important task to ensure the proper alignment and safety of the models. Often when training LLMs, ethical guidelines are followed yet alignment failures may still be uncovered through red teaming adversarial attacks. This work frames the red-teaming problem as a Markov decision process (MDP) and uses Monte Carlo tree search to find harmful behaviors of black-box, closed-source LLMs. We optimize token-level prompt suffixes towards targeted harmful behaviors on white-box LLMs and include a naturalistic loss term, log-perplexity, to generate more natural language attacks for better interpretability. The proposed algorithm, Kov, trains on white-box LLMs to optimize the adversarial attacks and periodically evaluates responses from the black-box LLM to guide the search towards more harmful black-box behaviors. In our preliminary study, results indicate that we can jailbreak black-box models, such as GPT-3.5, in only 10 queries, yet fail on GPT-4$-$which may indicate that newer models are more robust to token-level attacks. All work to reproduce these results is open sourced (https://github.com/sisl/Kov.jl).
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- 2024
72. The Biot stress -- right stretch relation for the compressible Neo-Hooke-Ciarlet-Geymonat model and Rivlin's cube problem
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Ghiba, Ionel-Dumitrel, Gmeineder, Franz, Holthausen, Sebastian, Martin, Robert J., and Neff, Patrizio
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Mathematics - Analysis of PDEs ,Mathematical Physics - Abstract
The aim of the paper is to recall the importance of the study of invertibility and monotonicity of stress-strain relations for investigating the non-uniqueness and bifurcation of homogeneous solutions of the equilibrium problem of a hyperelastic cube subjected to equiaxial tensile forces. In other words, we reconsider a remarkable possibility in this nonlinear scenario: Does symmetric loading lead only to symmetric deformations or also to asymmetric deformations? If so, what can we say about monotonicity for these homogeneous solutions, a property which is less restrictive than the energetic stability criteria of homogeneous solutions for Rivlin's cube problem. For the Neo-Hooke type materials we establish what properties the volumetric function $h$ depending on ${\rm det}\, F$ must have to ensure the existence of a unique radial solution (i.e. the cube must continue to remain a cube) for any magnitude of radial stress acting on the cube. The function $h$ proposed by Ciarlet and Geymonat satisfies these conditions. However, discontinuous equilibrium trajectories may occur, characterized by abruptly appearing non-symmetric deformations with increasing load, and a cube can instantaneously become a parallelepiped. Up to the load value for which the bifurcation in the radial solution is realized local monotonicity holds true. However, after exceeding this value, monotonicity no longer occurs on homogeneous deformations which, in turn, preserve the cube shape.
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- 2024
73. Adaptic: A Shape Changing Prop with Haptic Retargeting
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Gonzalez, J. Felipe, McClelland, John C., Teather, Robert J., Figueroa, Pablo, and Girouard, Audrey
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Computer Science - Human-Computer Interaction - Abstract
We present Adaptic, a novel "hybrid" active/passive haptic device that can change shape to act as a proxy for a range of virtual objects in VR. We use Adaptic with haptic retargeting to redirect the user's hand to provide haptic feedback for several virtual objects in arm's reach using only a single prop. To evaluate the effectiveness of Adaptic with haptic retargeting, we conducted a within-subjects experiment employing a docking task to compare Adaptic to non-matching proxy objects (i.e., Styrofoam balls) and matching shape props. In our study, Adaptic sat on a desk in front of the user and changed shapes between grasps, to provide matching tactile feedback for various virtual objects placed in different virtual locations. Results indicate that the illusion was convincing: users felt they were manipulating several virtual objects in different virtual locations with a single Adaptic device. Docking performance (completion time and accuracy) with Adaptic was comparable to props without haptic retargeting., Comment: 10 Pages
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- 2024
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74. Uniform approximation of vectors using adaptive randomized information
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Kunsch, Robert J. and Wnuk, Marcin
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Mathematics - Numerical Analysis ,65C, 65D, 46, 60 - Abstract
We study approximation of the embedding $\ell_p^m \rightarrow \ell_{\infty}^m$, $1 \leq p \leq 2$, based on randomized adaptive algorithms that use arbitrary linear functionals as information on a problem instance. We show upper bounds for which the complexity $n$ exhibits only a $(\log\log m)$-dependence. Our results for $p=1$ lead to an example of a gap of order $n$ (up to logarithmic factors) for the error between best adaptive and non-adaptive Monte Carlo methods. This is the largest possible gap for linear problems.
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- 2024
75. Design and Predict Tetragonal van der Waals Layered Quantum Materials of MPd$_5$I$_2$ (M=Ga, In and 3d Transition Metals)
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Nepal, Niraj K., Slade, Tyler J., Blawat, Joanna M., Eaton, Andrew, Palmstrom, Johanna C., Ueland, Benjamin G., Kaminski, Adam, McQueeney, Robert J., McDonald, Ross D., Canfield, Paul C., and Wang, Lin-Lin
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Quantum materials with stacking van der Waals (vdW) layers that can host non-trivial band structure topology and magnetism have shown many interesting properties. Here using high-throughput density functional theory calculations, we design and predict tetragonal vdW-layered quantum materials in the MPd$_5$I$_2$ structure (M=Ga, In and 3d transition metals). Our study shows that besides the known AlPd$_5$I$_2$, the -MPd$_5$- structural motif of three-layer slabs separated by two I layers can host a variety of metal elements giving arise to topological interesting features and highly tunable magnetic properties in both bulk and single layer 2D structures. Among them, TiPd$_5$I$_2$ and InPd$_5$I$_2$ host a pair of Dirac points and a likely strong topological insulator state for the band manifolds just above and below the top valence band, respectively, with their single layers possibly hosting quantum spin Hall states. CrPd$_5$I$_2$ is a ferromagnet with a large out-of-plane magneto-anisotropy energy, desirable for rare-earth-free permanent magnets., Comment: 25 pages, 6 figures
- Published
- 2024
76. Practical Rely/Guarantee Verification of an Efficient Lock for seL4 on Multicore Architectures
- Author
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Colvin, Robert J., Hayes, Ian J., Heiner, Scott, Höfner, Peter, Meinicke, Larissa, and Su, Roger C.
- Subjects
Computer Science - Logic in Computer Science - Abstract
Developers of low-level systems code providing core functionality for operating systems and kernels must address hardware-level features of modern multicore architectures. A particular feature is pipelined "out-of-order execution" of the code as written, the effects of which are typically summarised as a "weak memory model" - a term which includes further complicating factors that may be introduced by compiler optimisations. In many cases, the nondeterminism inherent in weak memory models can be expressed as micro-parallelism, i.e., parallelism within threads and not just between them. Fortunately Jones' rely/guarantee reasoning provides a compositional method for shared-variable concurrency, whether that be in terms of communication between top-level threads or micro-parallelism within threads. In this paper we provide an in-depth verification of the lock algorithm used in the seL4 microkernel, using rely/guarantee to handle both interthread communication as well as micro-parallelism introduced by weak memory models.
- Published
- 2024
77. Evidence for Rapid Variability at High Energies in GRBs
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Aldrich, E. Casey and Nemiroff, Robert J.
- Subjects
Astrophysics - High Energy Astrophysical Phenomena - Abstract
Intrinsic variability was searched for in arrival times of six gamma-ray bursts (GRBs) at high energies -- between 30 MeV and 2 GeV -- detected by the Fermi satellite's Large Area Telescope (LAT). The GRBs were selected from the Fermi LAT catalog with preference for events with numerous photons, a strong initial pulse, and measured redshifts. Three long GRBs and three short GRBs were selected and tested. Two different variability-detection algorithms were deployed, one counting photons in pairs, and the other multiplying time gaps between photons. In both tests, a real GRB was compared to 1000 Monte-Carlo versions of itself smoothed over a wide range of different timescales. The minimum detected variability timescales for long bursts (GRB 080916C, GRB 090926A, GRB 131108A) was found to be (0.005, 10.0, 10.0) seconds for the photon pair test and (2.0, 20.0, 10.0) seconds for the time-gap multiplication test. Additionally, the minimum detected variability timescales for the short bursts (GRB 090510, GRB 140619B, GRB 160709A) was found to be (0.05, 0.01, 20.0) seconds for the photon pair test and (0.05, 0.01, 20.0) seconds for the gap multiplication test. Statistical uncertainties in these times are about a factor of 2. The durations of these variability timescales may be used to constrain the geometry, dynamics, speed, cosmological dispersion, Lorentz-invariance violations, weak equivalence principle violations, and GRB models., Comment: 9 pages, 4 figures, accepted to MNRAS
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- 2024
- Full Text
- View/download PDF
78. Revisiting gauge invariance and Reggeization of pion exchange
- Author
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Montana, Gloria, Winney, Daniel, Bibrzycki, Lukasz, Fernandez-Ramirez, Cesar, Foti, Giorgio, Hammoud, Nadine, Mathieu, Vincent, Perry, Robert J., Pilloni, Alessandro, Rodas, Arkaitz, Shastry, Vanamali, Smith, Wyatt A., and Szczepaniak, Adam P.
- Subjects
High Energy Physics - Phenomenology ,Nuclear Theory - Abstract
The Reggeized pion is expected to provide the main contribution to the forward cross section in light meson photoproduction reactions with charge exchange at high energies. We discuss the Reggeization of pion exchange in charged pion photoproduction with an emphasis on consistency with current conservation. We show that the gauge-invariant amplitude for the exchange of a particle with generic even spin $J\geq 2$ in the $t$-channel is analytic at $J=0$, and that it can be interpreted in terms of the nucleon electric current. This enables us to reconcile the dynamics in the $s$- and $u$-channel, which involves also nucleon exchanges, with the amplitude expressed in terms of $t$-channel partial waves, as required by Regge theory., Comment: 16 pages, 4 figures
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- 2024
79. Effect of Austerity Measures on Infant Mortality: Evidence from Greece
- Author
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Kolesar, Robert J. and Spruk, Rok
- Subjects
Economics - General Economics ,Statistics - Applications - Abstract
This study examines the effect of fiscal austerity measures on infant mortality in Greece. Austerity measures were initiated by the tripartite committee and implemented between 2010 and 2017 to counteract deep fiscal deficit and large public debt. By comparing Greece with a plausible donor pool of OECD and Mediterranean member states in the period 1991-2020, we estimate a series of missing counterfactual scenarios to evaluate the infant mortality effects of large-scale reduction in spending on health care. A series of hybrid synthetic control and difference-in-differences estimates indicate a unique and pervasive increase in infant mortality after the implementation of austerity measures. Compared to a plausible OECD and Mediterranean counterfactual scenario, pro-cyclical austerity measures are associated with derailed and permanently increased infant mortality up to the present day. Our estimates suggest that compared to a plausible counterfactual scenario, the cumulative infant mortality cost of austerity policies exceeds 10,000 infant deaths or slightly less than 850 deaths for each year of the austerity policies. Notably, mortality increases are concentrated among boys. The estimated impacts survive a battery of rigorous robustness and placebo tests.
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- 2024
80. Anisotropic magnetic interactions in a candidate Kitaev spin liquid close to a metal-insulator transition
- Author
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Ma, Zeyu, Ni, Danrui, Kaib, David A. S., MacFarquharson, Kylie, Pearce, John S., Cava, Robert J., Valenti, Roser, Coldea, Radu, and Coldea, Amalia I.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
In the Kitaev honeycomb model, spins coupled by strongly-frustrated anisotropic interactions do not order at low temperature but instead form a quantum spin liquid with spin fractionalization into Majorana fermions and static fluxes. The realization of such a model in crystalline materials could lead to major breakthroughs in understanding entangled quantum states, however achieving this in practice is a very challenging task. The recently synthesized honeycomb material RuI$_3$ shows no long-range magnetic order down to the lowest probed temperatures and has been theoretically proposed as a quantum spin liquid candidate material on the verge of an insulator to metal transition. Here we report a comprehensive study of the magnetic anisotropy in un-twinned single crystals via torque magnetometry and detect clear signatures of strongly anisotropic and frustrated magnetic interactions. We attribute the development of sawtooth and six-fold torque signal to strongly anisotropic, bond-dependent magnetic interactions by comparing to theoretical calculations. As a function of magnetic field strength at low temperatures, torque shows an unusual non-parabolic dependence suggestive of a proximity to a field-induced transition. Thus, RuI$_3$, without signatures of long-range magnetic order, displays key hallmarks of an exciting new candidate for extended Kitaev magnetism with enhanced quantum fluctuations., Comment: 8 pages, 4 figures
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- 2024
81. The Discovery and Evolution of a Possible New Epoch of Cometary Activity by the Centaur (2060) Chiron
- Author
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Dobson, Matthew M., Schwamb, Megan E., Fitzsimmons, Alan, Schambeau, Charles, Beck, Aren, Denneau, Larry, Erasmus, Nicolas, Heinze, A. N., Shingles, Luke J., Siverd, Robert J., Smith, Ken W., Tonry, John L., Weiland, Henry, Young, David. R., Kelley, Michael S. P., Lister, Tim, Bernardinelli, Pedro H., Ferrais, Marin, Jehin, Emmanuel, Fedorets, Grigori, Benecchi, Susan D., Verbiscer, Anne J., Murtagh, Joseph, Duffard, Rene, Gomez, Edward, Chatelain, Joey, and Greenstreet, Sarah
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Astrophysics - Earth and Planetary Astrophysics - Abstract
Centaurs are small Solar System objects on chaotic orbits in the giant planet region, forming an evolutionary continuum with the Kuiper belt objects and Jupiter-family comets. Some Centaurs are known to exhibit cometary activity, though unlike comets this activity tends not to correlate with heliocentric distance and the mechanism behind it is currently poorly understood. We utilize serendipitous observations from the Asteroid Terrestrial-impact Last Alert System (ATLAS), Zwicky Transient Facility (ZTF), Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), Dark Energy Survey (DES), and Gaia in addition to targeted follow-up observations from the Las Cumbres Observatory, TRAnsiting Planets and PlanetesImals Small Telescope South (TRAPPIST-South), and Gemini North telescope to analyze an unexpected brightening exhibited by the known active Centaur (2060) Chiron in 2021. This is highly indicative of a cometary outburst. As of 2023 February, Chiron has still not returned to its pre-brightening magnitude. We find Chiron's rotational lightcurve, phase curve effects, and possible high-albedo surface features to be unlikely causes of this observed brightening. We consider the most likely cause to be an epoch of either new or increased cometary activity, though we cannot rule out a possible contribution from Chiron's reported ring system, such as a collision of as-yet unseen satellites shepherding the rings. We find no evidence for coma in our Gemini or TRAPPIST-South observations, though this does not preclude the possibility that Chiron is exhibiting a coma that is too faint for observation or constrained to the immediate vicinity of the nucleus., Comment: 39 pages, 14 figures, 14 tables. Has been accepted for publication in PSJ
- Published
- 2024
- Full Text
- View/download PDF
82. The VLT/ERIS vortex coronagraph: design, pointing control, and on-sky performance
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de Xivry, Gilles Orban, Absil, Olivier, De Rosa, Robert J., Bonse, Markus J., Dannert, Felix, Hayoz, Jean, Grani, Paolo, Puglisi, Alfio, Baruffolo, Andrea, Salasnich, Bernardo, Davies, Ric, Glauser, Adrian M., Huby, Elsa, Kenworthy, Matthew, Quanz, Sascha P., Taylor, William, and Zins, Gérard
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The Enhanced Resolution Imager and Spectrograph (ERIS) is the new near-infrared instrument at the VLT-UT4. ERIS replaces and extends the observational capabilities formerly provided by SINFONI and NACO: integral field spectroscopy at 1 - 2.5 $\mu$m, imaging at 1 - 5 $\mu$m with several options for high-contrast imaging, and long-slit spectroscopy. In particular, a vortex coronagraph is now available for high contrast observations at L and M band. It is implemented using annular groove (or vortex) phase masks (one for each of the L and M bands) in a focal plane, and a Lyot stop in a downstream pupil plane. The vortex coronagraph has a discovery space starting already at $\sim$1$\lambda/D$, and works well in broadbands. However, to reach its optimal performance, it is critical to correct for slow pointing errors onto the vortex phase mask, which mandates a dedicated pointing control strategy. To do so, a control loop based on the QACITS algorithm has been developed and commissioned for ERIS. Good pointing stability is now regularly achieved with errors between 0.01 and 0.02 $\lambda/D$ and a correction rate of 0.2 Hz. In this contribution, we first review the design of the ERIS vortex coronagraph. We then detail the implementation of the QACITS algorithm describing the entire observing sequence, including the calibration steps, the initial centering, and the stabilization during the observing template. We then discuss performance based on commissioning data in terms of pointing accuracy and stability. Finally, we present post-processed contrast curves obtained during commissioning and compare them with NACO vortex data, showing a significant improvement of about 1 mag at all separations., Comment: 15 pages, 13 figures, paper presented at SPIE Astronomical Telescopes + Instrumentation 2024
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- 2024
83. Examining partial ergodicity as a predictor of star formation departures from the galactic main sequence in isolated galaxies
- Author
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Smith, Fraser M. and Thacker, Robert J.
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
Lacking the ability to follow individual galaxies on cosmological timescales, our understanding of individual galaxy evolution is broadly inferred from population trends and behaviours. In its most prohibitive form, this approach assumes that galactic star formation properties exhibit ergodicity, so that individual galaxy evolution can be statistically inferred via ensemble behaviours. The validity of this assumption is tested through the use of observationally motivated simulations of isolated galaxies. The suite of simulated galaxies is statistically constructed to match observed galaxy properties by using kernel density estimation to create structural parameter distributions, augmented by theoretical relationships where necessary. We also test the impact of different physical processes, such as stellar winds or the presence of halo substructure on the star formation behaviour. We consider the subtleties involved in constraining ergodic properties, such as the distinction between stationarity imposed by stellar wind feedback and truly ergodic behaviour. However, without sufficient variability in star formation properties, individual galaxies are unable to explore the full parameter space. While, as expected, full ergodicity appears to be ruled out, we find reasonable evidence for partial ergodicity, where averaging over mass-selected subsets of galaxies more broadly resembles time averages, where the average largest deviation across physical scenarios is 0.20 dex. As far as we are aware, this the first time partial ergodicity has been considered in an astronomical context, and provides a promising statistical concept. Despite morphological changes introduced by close encounters with dark matter substructure, subhaloes are not found to significantly increase deviations from ergodic assumptions., Comment: 11 pages, 11 figures, 3 tables. Accepted for publication in MNRAS
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- 2024
84. Emergence of cellular nematic order is a conserved feature of gastrulation in animal embryos
- Author
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Li, Xin, Huebner, Robert J., Williams, Margot L. K., Sawyer, Jessica, Peifer, Mark, Wallingford, John B., and Thirumalai, D.
- Subjects
Condensed Matter - Soft Condensed Matter ,Physics - Biological Physics ,Quantitative Biology - Tissues and Organs - Abstract
Cells undergo dramatic changes in morphology during embryogenesis, yet how these changes affect the formation of ordered tissues remains elusive. Here we find that the emergence of a nematic liquid crystal phase occurs in cells during gastrulation in the development of embryos of fish, frogs, and fruit flies. Moreover, the spatial correlations in all three organisms are long-ranged and follow a similar power-law decay (y~$x^{-\alpha}$ ) with $\alpha$ less than unity for the nematic order parameter, suggesting a common underlying physical mechanism unifies events in these distantly related species. All three species exhibit similar propagation of the nematic phase, reminiscent of nucleation and growth phenomena. Finally, we use a theoretical model along with disruptions of cell adhesion and cell specification to characterize the minimal features required for formation of the nematic phase. Our results provide a framework for understanding a potentially universal features of metazoan embryogenesis and shed light on the advent of ordered structures during animal development., Comment: Main text: 29 pages, 6 figures. SI: 9 figures and 1 table
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- 2024
85. Far from Perfect: Quantum Error Correction with (Hyperinvariant) Evenbly Codes
- Author
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Steinberg, Matthew, Fan, Junyu, Harris, Robert J., Elkouss, David, Feld, Sebastian, and Jahn, Alexander
- Subjects
Quantum Physics ,High Energy Physics - Theory - Abstract
We introduce a new class of qubit codes that we call Evenbly codes, building on a previous proposal of hyperinvariant tensor networks. Its tensor network description consists of local, non-perfect tensors describing CSS codes interspersed with Hadamard gates, placed on a hyperbolic $\{p,q\}$ geometry with even $q\geq 4$, yielding an infinitely large class of subsystem codes. We construct an example for a $\{5,4\}$ manifold and describe strategies of logical gauge fixing that lead to different rates $k/n$ and distances $d$, which we calculate analytically, finding distances which range from $d=2$ to $d \sim n^{2/3}$ in the ungauged case. Investigating threshold performance under erasure, depolarizing, and pure Pauli noise channels, we find that the code exhibits a depolarizing noise threshold of about $19.1\%$ in the code-capacity model and $50\%$ for pure Pauli and erasure channels under suitable gauges. We also test a constant-rate version with $k/n = 0.125$, finding excellent error resilience (about $40\%$) under the erasure channel. Recovery rates for these and other settings are studied both under an optimal decoder as well as a more efficient but non-optimal greedy decoder. We also consider generalizations beyond the CSS tensor construction, compute error rates and thresholds for other hyperbolic geometries, and discuss the relationship to holographic bulk/boundary dualities. Our work indicates that Evenbly codes may show promise for practical quantum computing applications., Comment: 22 pages, 13 figures
- Published
- 2024
86. Quantum Control of an Oscillator with a Kerr-cat Qubit
- Author
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Ding, Andy Z., Brock, Benjamin L., Eickbusch, Alec, Koottandavida, Akshay, Frattini, Nicholas E., Cortinas, Rodrigo G., Joshi, Vidul R., de Graaf, Stijn J., Chapman, Benjamin J., Ganjam, Suhas, Frunzio, Luigi, Schoelkopf, Robert J., and Devoret, Michel H.
- Subjects
Quantum Physics - Abstract
Bosonic codes offer a hardware-efficient strategy for quantum error correction by redundantly encoding quantum information in the large Hilbert space of a harmonic oscillator. However, experimental realizations of these codes are often limited by ancilla errors propagating to the encoded logical qubit during syndrome measurements. The Kerr-cat qubit has been proposed as an ancilla for these codes due to its theoretically-exponential noise bias, which would enable fault-tolerant error syndrome measurements, but the coupling required to perform these syndrome measurements has not yet been demonstrated. In this work, we experimentally realize driven parametric coupling of a Kerr-cat qubit to a high-quality-factor microwave cavity and demonstrate a gate set enabling universal quantum control of the cavity. We measure the decoherence of the cavity in the presence of the Kerr-cat and discover excess dephasing due to heating of the Kerr-cat to excited states. By engineering frequency-selective dissipation to counteract this heating, we are able to eliminate this dephasing, thereby demonstrating a high on-off ratio of control. Our results pave the way toward using the Kerr-cat to fault-tolerantly measure error syndromes of bosonic codes.
- Published
- 2024
87. Resilience of Snowball Earth to Stochastic Events
- Author
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Chaverot, Guillaume, Zorzi, Andrea, Ding, Xuesong, Itcovitz, Jonathan, Fan, Bowen, Bhatnagar, Siddharth, Ji, Aoshuang, Graham, Robert J., and Mittal, Tushar
- Subjects
Astrophysics - Earth and Planetary Astrophysics ,Physics - Geophysics - Abstract
Earth went through at least two periods of global glaciation (i.e., ``Snowball Earth'' states) during the Neoproterozoic, the shortest of which (the Marinoan) may not have lasted sufficiently long for its termination to be explained by the gradual volcanic build-up of greenhouse gases in the atmosphere. Large asteroid impacts and supervolcanic eruptions have been suggested as stochastic geological events that could cause a sudden end to global glaciation via a runaway melting process. Here, we employ an energy balance climate model to simulate the evolution of Snowball Earth's surface temperature after such events. We find that even a large impactor (diameters of $d \sim 100\,\mathrm{km}$) and the supervolcanic Toba eruption ($74\,\mathrm{kyr}$ ago), are insufficient to terminate a Snowball state unless background CO$_2$ has already been driven to high levels by long-term outgassing. We suggest, according to our modeling framework, that Earth's Snowball states would have been resilient to termination by stochastic events., Comment: Accepted for publication in Geophysical Research Letters (GRL)
- Published
- 2024
88. The Simons Observatory: Dark Characterization of the Large Aperture Telescope
- Author
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Haridas, Saianeesh K., Ahmed, Zeeshan, Bhandarkar, Tanay, Devlin, Mark, Dicker, Simon, Duff, Shannon M., Dutcher, Daniel, Harrington, Kathleen, Henderson, Shawn W., Hubmayr, Johannes, Johnson, Bradley R., Kofman, Anna, Manduca, Alex, Niemack, Michael D., Randall, Michael J., Satterthwaite, Thomas P., Orlowski-Scherer, John, Schmitt, Benjamin L., Sierra, Carlos, Silva-Feaver, Max, Thornton, Robert J., Wang, Yuhan, and Zheng, Kaiwen
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The Simons Observatory (SO) is a cosmic microwave background experiment composed of three 0.42 m Small Aperture Telescopes (SATs) and one 6 m Large Aperture Telescope (LAT) in the Atacama Desert of Chile. The Large Aperture Telescope Receiver (LATR) was integrated into the LAT in August 2023; however, because mirrors were not yet installed, the LATR optical chain was capped at the 4K stage. In this dark configuration we are able to characterize many elements of the instrument without contributions from atmospheric noise. Here we show this noise is below the required upper limit and its features are well described with a simple noise model. Maps produced using this noise model have properties that are in good agreement with the white noise levels of our dark data. Additionally, we show that our nominal scan strategy has a minimal effect on the noise when compared to the noise when the telescope is stationary
- Published
- 2024
- Full Text
- View/download PDF
89. A foundational framework for the mesoscale modeling of dynamic elastomers and gels
- Author
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Wagner, Robert J. and Silberstein, Meredith N.
- Subjects
Condensed Matter - Soft Condensed Matter ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Statistical Mechanics - Abstract
Discrete mesoscale network models, in which explicitly modeled polymer chains are replaced by implicit pairwise potentials, are capable of predicting the macroscale mechanical response of polymeric materials such as elastomers and gels, while offering greater insight into microstructural phenomena than constitutive theory or macroscale experiments alone. However, whether such mesoscale models accurately represent the molecular structures of polymer networks requires investigation during their development, particularly in the case of dynamic polymers that restructure in time. We here introduce and compare the topological and mechanical predictions of an idealized, reduced-order mesoscale approach in which only tethered dynamic bonding sites and crosslinks in a polymer's backbone are explicitly modeled, to those of molecular theory and a Kremer-Grest, coarse-grained molecular dynamics approach. We find that for short chain networks at intermediate polymer packing fractions, undergoing relatively slow loading rates, the mesoscale approach reasonably reproduces the chain conformations, bond kinetic rates, and ensemble stress responses predicted by molecular theory and the bead-spring model. Further, it does so with a 90% reduction in computational cost. These savings grant the mesoscale model access to larger spatiotemporal domains than conventional molecular dynamics, enabling simulation of large deformations as well as durations approaching experimental timescales (e.g., those utilized in DMA). While the model investigated is for monodisperse polymer networks in theta-solvent, without entanglement, charge interactions, long-range dynamic bond interactions, or other confounding physical effects, this work highlights the utility of these models and lays a foundational groundwork for the incorporation of such phenomena moving forward.
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- 2024
90. Structural Constraint Integration in Generative Model for Discovery of Quantum Material Candidates
- Author
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Okabe, Ryotaro, Cheng, Mouyang, Chotrattanapituk, Abhijatmedhi, Hung, Nguyen Tuan, Fu, Xiang, Han, Bowen, Wang, Yao, Xie, Weiwei, Cava, Robert J., Jaakkola, Tommi S., Cheng, Yongqiang, and Li, Mingda
- Subjects
Condensed Matter - Materials Science ,Computer Science - Machine Learning - Abstract
Billions of organic molecules are known, but only a tiny fraction of the functional inorganic materials have been discovered, a particularly relevant problem to the community searching for new quantum materials. Recent advancements in machine-learning-based generative models, particularly diffusion models, show great promise for generating new, stable materials. However, integrating geometric patterns into materials generation remains a challenge. Here, we introduce Structural Constraint Integration in the GENerative model (SCIGEN). Our approach can modify any trained generative diffusion model by strategic masking of the denoised structure with a diffused constrained structure prior to each diffusion step to steer the generation toward constrained outputs. Furthermore, we mathematically prove that SCIGEN effectively performs conditional sampling from the original distribution, which is crucial for generating stable constrained materials. We generate eight million compounds using Archimedean lattices as prototype constraints, with over 10% surviving a multi-staged stability pre-screening. High-throughput density functional theory (DFT) on 26,000 survived compounds shows that over 50% passed structural optimization at the DFT level. Since the properties of quantum materials are closely related to geometric patterns, our results indicate that SCIGEN provides a general framework for generating quantum materials candidates., Comment: 512 pages total, 4 main figures + 218 supplementary figures
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- 2024
91. Time-bin entangled Bell state generation and tomography on thin-film lithium niobate
- Author
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Finco, Giovanni, Miserocchi, Filippo, Maeder, Andreas, Kellner, Jost, Sabatti, Alessandra, Chapman, Robert J., and Grange, Rachel
- Subjects
Quantum Physics ,Physics - Optics - Abstract
Optical quantum communication technologies are making the prospect of unconditionally secure and efficient information transfer a reality. The possibility of generating and reliably detecting quantum states of light, with the further need of increasing the private data-rate is where most research efforts are focusing. The physical concept of entanglement is a solution guaranteeing the highest degree of security in device-independent schemes, yet its implementation and preservation over long communication links is hard to achieve. Lithium niobate-on-insulator has emerged as a revolutionising platform for high-speed classical telecommunication and is equally suited for quantum information applications owing to the large second-order nonlinearities that can efficiently produce entangled photon pairs. In this work, we generate maximally entangled quantum states in the time-bin basis using lithium niobate-on-insulator photonics at the fibre optics telecommunication wavelength, and reconstruct the density matrix by quantum tomography on a single photonic integrated circuit. We use on-chip periodically-poled lithium niobate as source of entangled qubits with a brightness of 242 MHz/mW and perform quantum tomography with a fidelity of 91.9+-1.0 %. Our results, combined with the established large electro-optic bandwidth of lithium niobate, showcase the platform as perfect candidate to realise fibre-coupled, high-speed time-bin quantum communication modules that exploit entanglement to achieve information security.
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- 2024
92. Continuous-time quantum optimisation without the adiabatic principle
- Author
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Banks, Robert J., Raftis, Georgios S., Browne, Dan E., and Warburton, P. A.
- Subjects
Quantum Physics - Abstract
Continuous-time quantum algorithms for combinatorial optimisation problems, such as quantum annealing, have previously been motivated by the adiabatic principle. A number of continuous-time approaches exploit dynamics, however, and therefore are no longer physically motivated by the adiabatic principle. In this work we take Planck's principle as the underlying physical motivation for continuous-time quantum algorithms. Planck's principle states that the energy of an isolated system cannot decrease as the result of a cyclic process. We use this principle to justify monotonic schedules in quantum annealing which are not adiabatic. This approach also highlights the limitations of reverse quantum annealing in an isolated system., Comment: 15 + 12 pages, 16 + 26 figures
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- 2024
93. Canonical heights, periods and the Hurwitz zeta function
- Author
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Andreasson, Rolf and Berman, Robert J.
- Subjects
Mathematics - Number Theory ,Mathematics - Algebraic Geometry ,Mathematics - Differential Geometry - Abstract
Let (X,D) be a projective log pair over the ring of integers of a number field such that the log canonical line bundle K_(X,D) or its dual -K_(X,D) is relatively ample. We introduce a canonical height of K_(X,D) (and -K(X,D)) which is finite precisely when the complexifications of K_(X,D) (and -K(X,D)) are K-semistable. When the complexifications are K-polystable, the canonical height is the height of K_(X,D) (and -K(X,D)) wrt any volume-normalized K\"ahler-Einstein metric on the complexifications of K_(X,D) (and -K(X,D)) The canonical height is shown to have a number of useful variational properties. Moreover, it may be expressed as a limit of periods on the N-fold products of the complexifications of X, as N tends to infinity. In particular, using this limit formula, the canonical height for the arithmetic log surfaces (P_1,D) over the integers, where D has at most three components, is computed explicitly in terms of the Hurwitz zeta function and its derivative at s=-1. Combining this explicit formula with previous height formulas for quaternionic Shimura curves yields a procedure for extracting information about the canonical integral models of some Shimura curves, such as wild ramification. Furthermore, explicit formulas for the canonical height of twisted Fermat curves are obtained, implying explicit Parshin type bounds for the Arakelov metric., Comment: 61 pages
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- 2024
94. Neutron Yield of Thermo Scientific P385 D-T Neutron Generator vs. Current and Voltage
- Author
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Jeon, Jihye, Goldston, Robert J., and Gilson, Erik P.
- Subjects
Physics - Instrumentation and Detectors - Abstract
The Thermo Scientific P385 Neutron Generator is a compact neutron source, producing 14 MeV neutrons through the deuterium-tritium (DT) fusion reaction. For practical use, it is important to measure and preferably understand the dependence of the neutron production rate on the accelerator current and voltage. In this study, we evaluated neutron production with a neutron spectrometer (BTI N-Probe), a He-3 detector surrounded by HDPE shells (Nested Neutron Spectrometer, NNS), and two ZnS fast neutron scintillators (EJ-410) for both P385 A3082 and A3083 sealed tubes. We also predicted the neutron yield using the TRIM code, which calculates the trajectory and the energy loss of deuterons and tritons within the target. Experimental and theoretical results showed a linear dependence on beam current and a $\sim$3.5 power law dependence on the operating voltage. A series of NNS measurements, neutron spectrum from N-Probe and MCNP calculation showed that the A3083 and A3082 tubes provide a maximum neutron yield of $\sim 8.2 \times 10^8$ n/s and $\sim 4.5 \times 10^8$ n/s, respectively. We showed that tritium decay was not a significant contributor to this difference., Comment: 5 pages, 5 figures, 2 tables
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- 2024
95. A mid-circuit erasure check on a dual-rail cavity qubit using the joint-photon number-splitting regime of circuit QED
- Author
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de Graaf, Stijn J., Xue, Sophia H., Chapman, Benjamin J., Teoh, James D., Tsunoda, Takahiro, Winkel, Patrick, Garmon, John W. O., Chang, Kathleen M., Frunzio, Luigi, Puri, Shruti, and Schoelkopf, Robert J.
- Subjects
Quantum Physics - Abstract
Quantum control of a linear oscillator using a static dispersive coupling to a nonlinear ancilla underpins a wide variety of experiments in circuit QED. Extending this control to more than one oscillator while minimizing the required connectivity to the ancilla would enable hardware-efficient multi-mode entanglement and measurements. We show that the spectrum of an ancilla statically coupled to a single mode can be made to depend on the joint photon number in two modes by applying a strong parametric beamsplitter coupling between them. This `joint-photon number-splitting' regime extends single-oscillator techniques to two-oscillator control, which we use to realize a hardware-efficient erasure check for a dual-rail qubit encoded in two superconducting cavities. By leveraging the beamsplitter coupling already required for single-qubit gates, this scheme permits minimal connectivity between circuit elements. Furthermore, the flexibility to choose the pulse shape allows us to limit the susceptibility to different error channels. We use this scheme to detect leakage errors with a missed erasure fraction of $(9.0 \pm 0.5)\times10^{-4}$, while incurring an erasure rate of $2.92 \pm 0.01\%$ and a Pauli error rate of $0.31 \pm 0.01\%$, both of which are dominated by cavity errors., Comment: Updated references
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- 2024
96. QCD constraints on isospin-dense matter and the nuclear equation of state
- Author
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Abbott, Ryan, Detmold, William, Illa, Marc, Parreño, Assumpta, Perry, Robert J., Romero-López, Fernando, Shanahan, Phiala E., and Wagman, Michael L.
- Subjects
High Energy Physics - Lattice ,Nuclear Theory - Abstract
Understanding the behavior of dense hadronic matter is a central goal in nuclear physics as it governs the nature and dynamics of astrophysical objects such as supernovae and neutron stars. Because of the non-perturbative nature of quantum chromodynamics (QCD), little is known rigorously about hadronic matter in these extreme conditions. Here, lattice QCD calculations are used to compute thermodynamic quantities and the equation of state of QCD over a wide range of isospin chemical potentials. Agreement is seen with chiral perturbation theory predictions when the chemical potential is small. Comparison to perturbative QCD calculations at large chemical potential allows for an estimate of the gap in the superconducting phase, and this quantity is seen to agree with perturbative determinations. Since the partition function for an isospin chemical potential, $\mu_I$, bounds the partition function for a baryon chemical potential $\mu_B=3\mu_I/2$, these calculations also provide rigorous non-perturbative QCD bounds on the symmetric nuclear matter equation of state over a wide range of baryon densities for the first time., Comment: 17 pages, 14 figures, updated with supplementary material
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- 2024
97. AuriDESI: Mock Catalogues for the DESI Milky Way Survey
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Kizhuprakkat, Namitha, Cooper, Andrew P., Riley, Alexander H., Koposov, Sergey E., Aguilar, Jessica Nicole, Ahlen, Steven, Prieto, Carlos Allende, Brooks, David, Claybaugh, Todd, Dawson, Kyle, de la Macorra, Axel, Doel, Peter, Forero-Romero, Jaime E., Frenk, Carlos, Gaztañaga, Enrique, Gnedin, Oleg Y., Grand, Robert J. J., Gontcho, Satya Gontcho A, Honscheid, Klaus, Kehoe, Robert, Landriau, Martin, Manera, Marc, Meisner, Aaron, Miquel, Ramon, Nie, Jundan, Prada, Francisco, Rezaie, Mehdi, Rossi, Graziano, Sanchez, Eusebio, Schubnell, Michael, Seo, Hee-Jong, Tarlé, Gregory, Valluri, Monica, and Zhou, Zhimin
- Subjects
Astrophysics - Astrophysics of Galaxies - Abstract
The Dark Energy Spectroscopic Instrument Milky Way Survey (DESI MWS) will explore the assembly history of the Milky Way by characterising remnants of ancient dwarf galaxy accretion events and improving constraints on the distribution of dark matter in the outer halo. We present mock catalogues that reproduce the selection criteria of MWS and the format of the final MWS data set. These catalogues can be used to test methods for quantifying the properties of stellar halo substructure and reconstructing the Milky Way's accretion history with the MWS data, including the effects of halo-to-halo variance. The mock catalogues are based on a phase-space kernel expansion technique applied to star particles in the Auriga suite of six high-resolution $\Lambda$CDM magneto-hydrodynamic zoom-in simulations. They include photometric properties (and associated errors) used in DESI target selection and the outputs of the MWS spectral analysis pipeline (radial velocity, metallicity, surface gravity, and temperature). They also include information from the underlying simulation, such as the total gravitational potential and information on the progenitors of accreted halo stars. We discuss how the subset of halo stars observable by MWS in these simulations corresponds to their true content and properties. These mock Milky Ways have rich accretion histories, resulting in a large number of substructures that span the whole stellar halo out to large distances and have substantial overlap in the space of orbital energy and angular momentum., Comment: Accepted for publication in MNRAS, 31 pages, 27 figues, 7 tables. The mock catalogues are available at https://data.desi.lbl.gov/public/papers/mws/auridesi/v1
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- 2024
- Full Text
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98. Studying $\pi^+\pi^-$ photoproduction beyond Pomeron exchange
- Author
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Bibrzycki, Łukasz, Hammoud, Nadine, Mathieu, Vincent, Perry, Robert J., Akridge, Alex, Fernández-Ramírez, César, Montaña, Gloria, Pilloni, Alessandro, Rodas, Arkaitz, Shastry, Vanamali, Smith, Wyatt A., Winney, Daniel, and Szczepaniak, Adam P.
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High Energy Physics - Phenomenology ,High Energy Physics - Experiment - Abstract
Forward photoproduction of $\pi^+\pi^-$ pairs with invariant mass of the order of $m_\rho\sim 770$ MeV is traditionally understood to be produced via Pomeron exchange. Based on a detailed analysis of the CLAS photoproduction data, it is shown that the dynamics of two-pion photoproduction for $|t|\gtrsim 0.5$ GeV$^2$ cannot be explained by Pomeron exchange alone. This motivates the development of a new theoretical model of two-pion photoproduction which incorporates both two-pion and pion-nucleon resonant contributions. After fitting free parameters, the model provides an excellent description of the low moments of the angular distribution measured at CLAS, and enables an assessment of the relative contributions of particular production mechanisms and an interpretation of the various features of the data in terms of these mechanisms., Comment: 30 pages, 21 figures
- Published
- 2024
99. Self-attention-based non-linear basis transformations for compact latent space modelling of dynamic optical fibre transmission matrices
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Zheng, Yijie, Kilpatrick, Robert J., Phillips, David B., and Gordon, George S. D.
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Computer Science - Machine Learning - Abstract
Multimode optical fibres are hair-thin strands of glass that efficiently transport light. They promise next-generation medical endoscopes that provide unprecedented sub-cellular image resolution deep inside the body. However, confining light to such fibres means that images are inherently scrambled in transit. Conventionally, this scrambling has been compensated by pre-calibrating how a specific fibre scrambles light and solving a stationary linear matrix equation that represents a physical model of the fibre. However, as the technology develops towards real-world deployment, the unscrambling process must account for dynamic changes in the matrix representing the fibre's effect on light, due to factors such as movement and temperature shifts, and non-linearities resulting from the inaccessibility of the fibre tip when inside the body. Such complex, dynamic and nonlinear behaviour is well-suited to approximation by neural networks, but most leading image reconstruction networks rely on convolutional layers, which assume strong correlations between adjacent pixels, a strong inductive bias that is inappropriate for fibre matrices which may be expressed in a range of arbitrary coordinate representations with long-range correlations. We introduce a new concept that uses self-attention layers to dynamically transform the coordinate representations of varying fibre matrices to a basis that admits compact, low-dimensional representations suitable for further processing. We demonstrate the effectiveness of this approach on diverse fibre matrix datasets. We show our models significantly improve the sparsity of fibre bases in their transformed bases with a participation ratio, p, as a measure of sparsity, of between 0.01 and 0.11. Further, we show that these transformed representations admit reconstruction of the original matrices with < 10% reconstruction error, demonstrating the invertibility.
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- 2024
100. scores: A Python package for verifying and evaluating models and predictions with xarray
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Leeuwenburg, Tennessee, Loveday, Nicholas, Ebert, Elizabeth E., Cook, Harrison, Khanarmuei, Mohammadreza, Taggart, Robert J., Ramanathan, Nikeeth, Carroll, Maree, Chong, Stephanie, Griffiths, Aidan, and Sharples, John
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Physics - Atmospheric and Oceanic Physics ,Statistics - Applications - Abstract
`scores` is a Python package containing mathematical functions for the verification, evaluation and optimisation of forecasts, predictions or models. It supports labelled n-dimensional (multidimensional) data, which is used in many scientific fields and in machine learning. At present, `scores` primarily supports the geoscience communities; in particular, the meteorological, climatological and oceanographic communities. `scores` not only includes common scores (e.g., Mean Absolute Error), it also includes novel scores not commonly found elsewhere (e.g., FIxed Risk Multicategorical (FIRM) score, Flip-Flop Index), complex scores (e.g., threshold-weighted continuous ranked probability score), and statistical tests (such as the Diebold Mariano test). It also contains isotonic regression which is becoming an increasingly important tool in forecast verification and can be used to generate stable reliability diagrams. Additionally, it provides pre-processing tools for preparing data for scores in a variety of formats including cumulative distribution functions (CDF). At the time of writing, `scores` includes over 50 metrics, statistical techniques and data processing tools. All of the scores and statistical techniques in this package have undergone a thorough scientific and software review. Every score has a companion Jupyter Notebook tutorial that demonstrates its use in practice. `scores` supports `xarray` datatypes, allowing it to work with Earth system data in a range of formats including NetCDF4, HDF5, Zarr and GRIB among others. `scores` uses Dask for scaling and performance. Support for `pandas` is being introduced. The `scores` software repository can be found at https://github.com/nci/scores/, Comment: Minor revisions to text and table. Updated title. 6 pages, 1 table. Software repository at https://github.com/nci/scores/
- Published
- 2024
- Full Text
- View/download PDF
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