Search

Cosmic strings are a common prediction in many grand unified theories and a promising source of stochastic gravitational waves (GWs) from the early Universe. In this paper, we point out that the GW signal from cosmic strings produced at a comparatively low energy scale, $v \lesssim 10^9 \textrm{GeV}$, exhibits several novel features that are not present in the case of high-scale cosmic strings. Our findings notably include (i) a sharp cutoff frequency $f_{\rm cut}$ in the GW spectrum from the fundamental oscillation mode on closed string loops and (ii) an oscillating pattern in the total GW spectrum from all oscillation modes whose local minima are located at integer multiples of $f_{\rm cut}$. These features reflect the fact that string loops produced in the early Universe fail to shrink to zero size because of GW emission within the age of the Universe, if their tension is low enough. In addition, they offer an exciting opportunity to directly probe the discrete spectrum of oscillation modes on closed string loops in GW observations. For strings produced at a scale $v \sim 10^9\textrm{GeV}$, the novel features in the GW spectrum are within the sensitivity reach of future experiments such as BBO and DECIGO., Comment: 16 pages, 4 figures

We present a simulation-based cosmological analysis using a combination of Gaussian and non-Gaussian statistics of the weak lensing mass (convergence) maps from the first three years (Y3) of the Dark Energy Survey (DES). We implement: 1) second and third moments; 2) wavelet phase harmonics; 3) the scattering transform. Our analysis is fully based on simulations, spans a space of seven $\nu w$CDM cosmological parameters, and forward models the most relevant sources of systematics inherent in the data: masks, noise variations, clustering of the sources, intrinsic alignments, and shear and redshift calibration. We implement a neural network compression of the summary statistics, and we estimate the parameter posteriors using a simulation-based inference approach. Including and combining different non-Gaussian statistics is a powerful tool that strongly improves constraints over Gaussian statistics (in our case, the second moments); in particular, the Figure of Merit $\textrm{FoM}(S_8, \Omega_{\textrm{m}})$ is improved by 70 percent ($\Lambda$CDM) and 90 percent ($w$CDM). When all the summary statistics are combined, we achieve a 2 percent constraint on the amplitude of fluctuations parameter $S_8 \equiv \sigma_8 (\Omega_{\textrm{m}}/0.3)^{0.5}$, obtaining $S_8 = 0.794 \pm 0.017$ ($\Lambda$CDM) and $S_8 = 0.817 \pm 0.021$ ($w$CDM). The constraints from different statistics are shown to be internally consistent (with a $p$-value>0.1 for all combinations of statistics examined). We compare our results to other weak lensing results from the DES Y3 data, finding good consistency; we also compare with results from external datasets, such as \planck{} constraints from the Cosmic Microwave Background, finding statistical agreement, with discrepancies no greater than $<2.2\sigma$., Comment: 24 pages, 13 figures, to be submitted to PRD. Comments welcome!

Empirical correlations connecting starlight to galaxy dynamics (e.g., the fundamental plane (FP) of elliptical/quiescent galaxies and the Tully--Fisher relation of spiral/star-forming galaxies) provide cosmology-independent distance estimation and are central to local Universe cosmology. In this work, we introduce the mass hyperplane (MH), which is the stellar-to-dynamical mass relation $(M_\star/M_\mathrm{dyn})$ recast as a linear distance indicator. Building on recent FP studies, we show that both star-forming and quiescent galaxies follow the same empirical MH, then use this to measure the peculiar velocities (PVs) for a sample of 2496 galaxies at $z<0.12$ from GAMA. The limiting precision of MH-derived distance/PV estimates is set by the intrinsic scatter in size, which we find to be $\approx$0.1~dex for both quiescent and star-forming galaxies (when modeled independently) and $\approx$0.11~dex when all galaxies are modeled together; showing that the MH is as good as the FP. To empirically validate our framework and distance/PV estimates, we compare the inferred distances to groups as derived using either quiescent or star-forming galaxies. A good agreement is obtained with no discernible bias or offset, having a scatter of $\approx$0.05~dex $\approx$12\% in distance. Further, we compare our PV measurements for the quiescent galaxies to the previous PV measurements of the galaxies in common between GAMA and the Sloan Digital Sky Survey (SDSS), which shows similarly good agreement. Finally, we provide comparisons of PV measurements made with the FP and the MH, then discuss possible improvements in the context of upcoming surveys such as the 4MOST Hemisphere Survey (4HS)., Comment: Accepted: 15th May 2024

We study a scenario in which the expansion of the early universe is driven by a hot hidden sector (HS) with an initial temperature $T'$ that is significantly higher than that of a visible sector (VS), $T' \gg T$. The latter is assumed to be made of Standard Model (SM) particles and our main focus is on the possibility that dark matter (DM) is part of the hot HS and that its abundance is set by secluded freeze-out. In particular, we study the subsequent evolution and fate of its companion particle after DM freeze-out. To be concrete, we work within a framework in which the DM is a Dirac fermion and its companion a massive dark photon. Coupling between the SM and HS is through kinetic mixing. We provide a comprehensive analytical and numerical analysis, including the subsequent process of thermalization of the two sectors. We use these results to explore the viable parameter space of both the DM matter particle and its companion. Assuming that the DM annihilation cross section is bounded by unitarity, the mass of the DM could be as large as $\sim 10^{11}$ GeV., Comment: 25 pages, 7 figures, revtex

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will image billions of astronomical objects in the wide-fast-deep primary survey and in a set of minisurveys including intensive observations of a group of deep drilling fields (DDFs). The DDFs are a critical piece of three key aspects of the LSST Dark Energy Science Collaboration (DESC) cosmological measurements: they provide a required calibration for photometric redshifts and weak gravitational lensing measurements and they directly contribute to cosmological constraints from the most distant type Ia supernovae. We present a set of cohesive DDF strategies fulfilling science requirements relevant to DESC and following the guidelines of the Survey Cadence Optimization Committee. We propose a method to estimate the observing strategy parameters and we perform simulations of the corresponding surveys. We define a set of metrics for each of the science case to assess the performance of the proposed observing strategies. We show that the most promising results are achieved with deep rolling surveys characterized by two sets of fields: ultradeep fields (z<1.1) observed at a high cadence with a large number of visits over a limited number of seasons; deep fields (z<0.7), observed with a cadence of ~3 nights for ten years. These encouraging results should be confirmed with realistic simulations using the LSST scheduler. A DDF budget of ~8.5% is required to design observing strategies satisfying all the cosmological requirements. A lower DDF budget lead to surveys that either do not fulfill photo-z/WL requirements or are not optimal for SNe Ia cosmology., Comment: 19 pages, 23 figures

Gamma-ray bursts (GRBs) have long been considered potential sources of ultra-high-energy cosmic rays (UHECRs; with energy $\gtrsim 10^{18} {\rm~eV}$). In this work, we propose a novel model generating MeV emission lines in GRB, which can constrain the properties of heavy nuclei that potentially exist in GRB jets. Specifically, we find that relativistic hydrogen-like high-atomic-number ions originating from the $\beta$ decay of unstable nuclei and/or the recombination entrained in the GRB jet can generate narrow MeV emission lines through the de-excitation of excited-electrons. This model can successfully explain the MeV emission line observed in the most luminous GRB ever recorded, GRB~221009A, with suitable parameters including a Lorentz factor $\gamma \sim 820-1700$ and a total mass of heavy nuclei $M_{\rm tot} \sim 10^{23} - 10^{26}$~g. Especially, the emission line broadening can be reasonably attributed to both the expansion of the jet shell and the thermal motion of nuclei, naturally resulting in a narrow width ($\sigma_{\rm line} / E_{\rm line} \lesssim 0.2$) consistent with the observation. Furthermore, we predict that different GRBs can exhibit lines in different bands with various evolving behaviors, which might be confirmed with further observations. Finally, our model provides indirect evidence that GRBs may be one of the sources of UHECRs., Comment: 13 pages, 4 figures; Accepted for publication in ApJL

We develop a C++ package of the STOchastic LAttice Simulation (STOLAS) of cosmic inflation. It performs the numerical lattice simulation in the application of the stochastic-$\delta N$ formalism. STOLAS can directly compute the three-dimensional map of the observable curvature perturbation without estimating its statistical properties. In its application to two toy models of inflation, chaotic inflation and Starobinsky's linear-potential inflation, we confirm that STOLAS is well-consistent with the standard perturbation theory. Furthermore, by introducing the importance sampling technique, we have success in numerically sampling the current abundance of primordial black holes in a non-perturbative way. The package is available at https://github.com/STOchasticLAtticeSimulation/STOLAS_dist., Comment: 31 pages, 10 figures

The origin of the "Changing-look" (CL) phenomenon in supermassive black holes (SMBHs) remains an open issue. This study aims to shed light on this phenomenon by focusing on a sample that encompasses all known repeating CL active galactic nuclei (AGNs). Through the identification of a characteristic time scale for the CL phenomenon, it was observed that larger SMBHs possess shorter characteristic timescales, while smaller SMBHs exhibit longer timescales. These findings reveal a significant contrast to the traditional AGN variability that has been adequately explained by the AGN's disk instability model. This stark discrepancy highlights a distinct origin of the CL phenomenon, distinguishing it from traditional AGN variability. By properly predicting the characteristic time scale and its dependence on SMBH mass, we propose that the CL phenomenon is likely a result of a variation in accretion rate caused by a sudden change in the supply of circumnuclear gas during the transition between active and passive SMBH fueling stages., Comment: 14 pages, 4 figures and 2 tables, accepted by ApJ

We investigate the interaction between the dark sectors from a dynamical systems perspective. A general setup for interacting dark energy models that incorporates both quintessence and phantom fields through a switch parameter, allowing an interaction in the dark sectors has been considered. In the first part of our analysis, we have not assumed any specific form of the interaction and in the second part, we invoked examples in general framework of the interaction. The potentials of the scalar field are classified into two broad classes of potentials: exponential and non-exponential. We identify the potential late-time attractors of the system which have a complete dark energy domination. From our analysis, it is evident there could be an interaction between the dark sector. The interaction, if any, weakens over time. We find for the quintessence field the transfer of energy from dark matter to dark energy can flip the direction and on the contrary, for the phantom field, it is only from dark matter to dark energy., Comment: 19 pages, 8 figures

It has recently been shown in Ref. [1] that the double-inflation scenario based on the Coleman-Weinberg potential can successfully generate primordial black holes (PBHs) with the inflationary predictions consistent with the Planck measurements. These PBHs can play the role of dark matter in our universe. In this paper, we propose the classically conformal minimal $B-L$ model as an ultra-violet (UV) completion of the scenario. In our model, the $B-L$ Higgs field is identified with the inflaton and the electroweak symmetry breaking is triggered by the radiative $B-L$ symmetry breaking with the Coleman-Weinberg potential. We show that this UV completion leads to a viable cosmological history after the double inflaton: the universe is reheated via inflaton decay into right-handed neutrinos whose mass is determined consistently by a relation between the number of e-folds and reheating temperature. Using the general parameterization for neutrino Dirac Yukawa couplings through the seesaw mechanism and the neutrino oscillation data, we also show that the observed baryon asymmetry of the universe is successfully reproduced by either resonant leptogenesis or non-thermal leptogenesis. Based on the scalar power spectrum shown in Ref. [1], we evaluate the scalar induced gravitational wave spectrum, which can be tested by various proposed gravitational wave observatories like BBO, DECIGO etc., Comment: 12 page with references, 2 Figures

We conduct a first comprehensive study of the Luminosity Function (LF) using a non-parametric approach. We use Gaussian Process to fit available luminosity data between redshifts $z \sim 2-8$. Our free-form LF in the non-parametric approach rules out the conventional Schechter function model to describe the luminosity-magnitude relation at redshifts $z=3$ and $4$. Hints of deviation from the Schechter function are also noticed at redshifts 2, 7 and 8 at lower statistical significance. Significant deviation starts for brighter ionizing sources at $M_{\rm UV} \lesssim -21$. The UV luminosity density data at different redshifts are then derived by integrating the LFs obtained from both methods with a truncation magnitude of $-17$. In our analysis, we also include the first 90 arcmin$^2$ JWST/NIRCam data at $z \sim 9-12$. Since at larger magnitudes, we do not find major deviations from the Schechter function, the integrated luminosity density differs marginally between the two methods. Finally, we obtain the history of reionization from a joint analysis of UV luminosity density data along with the ionization fraction data and Planck observation of Cosmic Microwave Background. The history of reionization is not affected by the deviation of LFs from Schechter function at lower magnitudes. We derive reionization optical depth to be $\tau_{\rm re}=0.0494^{+0.0007}_{-0.0006}$ and the duration between 10$\% $ and 90$\%$ completion of ionization process is found to be $\Delta z\sim 1.627^{+0.059}_{-0.071}$., Comment: 18 pages; 6 figures

The natural inflation model with a periodic cosine potential is ruled out by recent Planck 2018 data for the decay constant $f \lesssim 5.5~M_{\rm Pl}$. If the Planck data is combined with the BICEP Keck array and BAO data, the model is excluded (at $2$-$\sigma$) for all values of $f$. In this context, we revisit the model when the pseudoscalar inflation $\phi$ is coupled with a gauge field via a coupling of the form $\frac{\alpha}{f} \phi F \tilde{F}$, where $F (\tilde F)$ denotes the gauge field (dual) strength tensor, and $\alpha$ is the coupling constant. The back-reactions associated with the gauge field production during the later stages of inflation extend the duration of inflation. We numerically evaluate the dynamics of the fields while neglecting the effects due to the perturbations in the inflaton field. It allows us to determine the scalar and tensor power spectra leading to the calculations of observables at the Cosmic Microwave Background (CMB) scales. We find that the natural inflation model survives the test of the latest data only for a certain range of the coupling constant $\alpha$. Our analysis shows that the latest constraints coming from the scalar spectral index are more stringent than the ones arising from the non-gaussianities and the running of the scalar spectrum. This leads to lower and upper bounds on $\xi_*$, the parameter that controls the growth of the gauge field., Comment: 19 pages, 7 figures

Drift scan observations provide the broad sky coverage and instrumental stability needed to measure the Epoch of Reionization (EoR) 21-cm signal. In such observations, the telescope's pointing center (PC) moves continuously on the sky. The Tracking Tapered Gridded Estimator (TTGE) combines observations from different PC to estimate $P(k_{\perp}, k_{\parallel})$ the 21-cm power spectrum, centered on a tracking center (TC) which remains fixed on the sky. The tapering further restricts the sky response to a small angular region around TC, thereby mitigating wide-field foregrounds. Here we consider $154.2 \, {\rm MHz}$ ($z = 8.2$) Murchison Widefield Array (MWA) drift scan observations. The periodic pattern of flagged channels, present in MWA data, is known to introduce artefacts which pose a challenge for estimating $P(k_{\perp}, k_{\parallel})$. We demonstrate that the TTGE is able to recover $P(k_{\perp}, k_{\parallel})$ without any artefacts, and estimate $P(k)$ within $5 \%$ accuracy over a large $k$-range. We also present preliminary results for a single PC, combining 9 nights of observation $(17 \, {\rm min}$ total). We find that $P(k_{\perp}, k_{\parallel})$ exhibits streaks at a fixed interval of $k_{\parallel}=0.29 \, {\rm Mpc}^{-1}$, which matches $\Delta \nu_{\rm per}=1.28 \, {\rm MHz}$ that is the period of the flagged channels. The streaks are not as pronounced at larger $k_{\parallel}$, and in some cases they do not appear to extend across the entire $k_{\perp}$ range. The rectangular region $0.05 \leq k_{\perp} \leq 0.16 \, {\rm Mpc^{-1}}$ and $0.9 \leq k_{\parallel} \leq 4.6 \, {\rm Mpc^{-1}}$ is found to be relatively free of foreground contamination and artefacts, and we have used this to place the $2\sigma$ upper limit $\Delta^2(k) < (1.85 \times 10^4)^2\, {\rm mK^2}$ on the EoR 21-cm mean squared brightness temperature fluctuations at $k=1 \,{\rm Mpc}^{-1}$., Comment: 15 pages, 11 figures, accepted for publication in PASA

First stars play crucial roles in development of the universe, influencing events like cosmic reionization and the chemical enrichment. While first stars are conventionally thought to form at around $z \sim 20-30$ in the standard $\Lambda$ Cold Dark Matter ($\Lambda$CDM) cosmology, observational constraints on small-scale density fluctuations remain limited, possibly differing significantly from the scale-invariant fluctuations assumed in the $\Lambda$CDM model. Should this be the case, the formation of first stars could occur much earlier than typically predicted. In this study, we investigate the formation process of first stars in the extremely early epochs of $z \gtrsim 100$ in the post-recombination universe. At such early times, the effects of the warm cosmic microwave background (CMB) become significant. We calculate the collapse of primordial star-forming clouds using a one-zone thermo-chemical model that accounts for CMB influences on radiative heating, Compton cooling, and photodissociation reactions. We found that the impact of the CMB on the evolution is limited at $z \lesssim 100$, with the temperature evolution closely resembling the conventional model. However, within the range $100 \lesssim z \lesssim 400$, the formation of H$_2$ via the H$^-$ channel is impeded by H$^-$ photodetachment induced by the CMB, leading to higher temperatures compared to standard one. Consequently, first stars with masses exceeding $1000 ~\mathrm{M}_\odot$ can emerge at $z \gtrsim 100$. Furthermore, at $z \gtrsim 500$, the temperature evolution becomes nearly isothermal solely due to atomic cooling, as H$_2$ formation is entirely suppressed. In such cases, supermassive stars with masses around $\sim 10^5 ~\mathrm{M}_\odot$ are expected to form solely via atomic cooling. These findings emphasize the significant variation in the typical mass of the first stars depending on the epoch of formation.

We review a number of unimodular no-scale supergravity models with F-term SUSY breaking which support technically natural de Sitter vacua. A variant of these models develops a stage of inflection-point inflation which can be realized for subplanckian field values consistently with the observational data. For central value of the spectral index ns, the necessary tuning is of the order of 10^-6, the tensor-to-scalar ratio is tiny whereas the running of ns is around -3x10^-3. Our proposal is compatible with high-scale SUSY and the results of LHC on the Higgs boson mass., Comment: Prepared for the Proceedings of the Corfu Summer Institute 2023 -- Conference: C23-05-01

The detection of gravitational waves (GWs) has opened a new window to test the fundamental nature of gravity. We present constraints on the nonstandard propagation of GWs using the spectral siren method applied to binary black hole (BBH) mergers from the third Gravitational-Wave Transient Catalog (GWTC-3). The spectral siren method exploits the redshift distribution of BBHs to probe the cosmic expansion history and break degeneracies between cosmology and modified gravity effects. We focus on the friction term $\nu$ in the nonstandard GW propagation equation, which characterizes the running of the Planck mass. Assuming the standard $\Lambda$CDM cosmology, we find $\nu = 0.5^{+3.5}_{-2.6}$ (median and $90\%$ credible interval), improving upon previous constraints from the bright siren event GW170817 by an order of magnitude. This improvement is due to the higher redshifts of BBHs in GWTC-3, reaching up to $z \sim 1$. Our result suggests that the propagation of GWs is consistent with the predictions of general relativity, placing limits on modified gravity theories that predict a time-varying Planck mass. As the sensitivity of GW detectors improves, the spectral siren method will provide a powerful tool for testing gravity on cosmological scales and probing the physics of the early Universe., Comment: 7 pages, 1 figure

General relativity (GR) is the most successful theory of gravity, with great observational support at local scales. However, to keep GR valid at over cosmic scales, some phenomena (such as the flat galaxy rotation curves and the cosmic acceleration) require the assumption of exotic dark matter. The radial acceleration relation (RAR) indicates a tight correlation between dynamical mass and baryonic mass in galaxies and galaxy clusters. This suggests that the observations could be better explained by modified gravity theories without exotic matter. Modified Newtonian Dynamics (MOND) is an alternative theory for explaining some cases of flat galaxy rotation curves by using a new fundamental constant acceleration $a_0$, the so-called Milgromian parameter. However, this non-relativistic model is too rigid (with insufficient parameters) to fit the large diversity of observational phenomena. In contrast, a relativistic MOND-like gravity naturally emerges from the hyperconical model, which derives a fictitious acceleration compatible with observations. This study analyses the compatibility of the hyperconical model with respect to RAR observations of 10 galaxy clusters obtained from HIFLUGCS and 60 high-quality SPARC galaxy rotation curves. The results show that a general relation can be fitted to most cases with only one or two parameters, with an acceptable chi-square and $p$-value. These findings suggest a possible way to complete the proposed modification of GR on a cosmic scale., Comment: 18 pages, 5 figures, 1 table. Submitted to ApJL in this form

We study the fine-structure constant dependence of the rates of some selected radiative capture reactions within the framework of so-called Halo Effective Field Theory in order to assess the adequacy of some assumptions made on the Coulomb penetrability. We find that this dependence deviates from that implied by a parameterization of the cross sections of this effect via a simple penetration factor. Some features of this fine-structure dependence are discussed, in particular its potential impact on the abundances of the light elements in primordial nucleosynthesis., Comment: 17 pages, 14 figures

Galaxy cluster masses help to constrain cosmological parameters through the halo mass function. To get rid of major biases in the mass measurement, we directly probe the cluster gravitational potentials by observing their gravitational lensing on the Cosmic Microwave Background (CMB). We measured the average mass of a 468-cluster sample using SPT-SZ and Planck/HFI PR2 sky maps and compared it with the masses provided in the SPT-SZ data set. We found an average mass ratio of $M_{\rm CMBlens}/M_{\rm SZ} = 0.98 \pm 0.19$ (stat.) $\pm 0.03$ (syst.) [arxiv:2402.18346], in agreement with SPT-SZ masses. We also showed that the CMB large scales are important for the reconstruction of the lensing potential of a cluster with a quadratic estimator., Comment: 4 pages, 2 figures, contribution to the 2024 Cosmology session of the 58th Rencontres de Moriond

A direct approach to studying the galaxy-halo connection is the analysis of observed groups and clusters of galaxies that trace the underlying dark matter halos, making identifying galaxy clusters and their associated brightest cluster galaxies (BCGs) crucial. We test and propose a robust density-based clustering algorithm that outperforms the traditional Friends-of-Friends (FoF) algorithm in the currently available galaxy group/cluster catalogs. Our new approach is a modified version of the Ordering Points To Identify the Clustering Structure (OPTICS) algorithm, which accounts for line-of-sight positional uncertainties due to redshift space distortions by incorporating a scaling factor, and is thereby referred to as sOPTICS. When tested on both a galaxy group catalog based on semi-analytic galaxy formation simulations and observational data, our algorithm demonstrated robustness to outliers and relative insensitivity to hyperparameter choices. In total, we compared the results of eight clustering algorithms. The proposed density-based clustering method, sOPTICS, outperforms FoF in accurately identifying giant galaxy clusters and their associated BCGs in various environments with higher purity and recovery rate, also successfully recovering 115 BCGs out of 118 reliable BCGs from a large galaxy sample.

We build an emulator based on the polynomial chaos expansion (PCE) technique to efficiently model the non-linear effects associated with the clustering of the $k$-essence dark energy in the effective field theory (EFT) framework. These effects can be described through a modification of Poisson's equation, denoted by the function $\mu(k,z)$, which in general depends on wavenumber $k$ and redshift $z$. To emulate this function, we perform $200$ high-resolution $N$-body simulations sampled from a seven-dimensional parameter space with the Latin hypercube method. These simulations are executed using the $\texttt{k-evolution}$ code on a fixed mesh, containing $1200^3$ dark matter particles within a box size of $400~\text{Mpc}/ h$. The emulation process has been carried out within $\texttt{UQLab}$, a $\texttt{MATLAB}$-based software specifically dedicated to emulation and uncertainty quantification tasks. Apart from its role in emulation, the PCE method also facilitates the measurement of Sobol indices, enabling us to assess the relative impact of each cosmological parameter on the $\mu$ function. Our results show that the PCE-based emulator efficiently and accurately reflects the behavior of the $k$-essence dark energy for the cosmological parameter space defined by $w_0 c_s^2 \text{CDM} +\sum m_{\nu}$. Compared against actual simulations, the emulator achieves sub-percent accuracy up to the wavenumber $k \approx 9.4 ~h \text{Mpc}^{-1} $ for redshifts $z \leq 3$. Our emulator provides an efficient and reliable tool for Markov chain Monte Carlo (MCMC) analysis, and its capability to closely mimic the properties of the $k$-essence dark energy makes it a crucial component in Bayesian parameter estimations. The code is publicly available at https://github.com/anourizo/k-emulator ., Comment: 21 pages, 16 figures, 4 tables

The fundamental constants at recombination can differ from their present-day values due to degeneracies in cosmological parameters, raising the possibility of yet-undiscovered physics coupled directly to the Standard Model. We study the cosmology of theories in which a new, hyperlight scalar field modulates the electron mass and fine-structure constant at early times. We find new degeneracies in cosmologies that pair early recombination with a new contribution to the matter density arising at late times, whose predictions can be simultaneously consistent with CMB and low-redshift distance measurements. Such "late dark matter" already exists in the Standard Model in the form of massive neutrinos, but is necessarily realized by the scalar responsible for shifting the early-time fundamental constants. After detailing the physical effects of varying constants and hyperlight scalar fields on cosmology, we find that variations of the electron mass and fine structure constant are constrained at the percent and permille level, respectively, and a hyperlight scalar in the mass range $10^{-32}~\mathrm{eV} \lesssim m_\phi \lesssim 10^{-28}~\mathrm{eV}$ can impact what variations are allowed while composing up to a percent of the present dark matter density. We comment on the potential for models with a varying electron mass to reconcile determinations of the Hubble constant from cosmological observations and distance-ladder methods, and we show that parameter inference varies significantly between recent baryon acoustic oscillation and type Ia supernova datasets., Comment: 50+18 pages, 19 figures

We assess the effectiveness of a non-parametric bias model in generating mock halo catalogues for modified gravity (MG) cosmologies, relying on the distribution of dark matter from either MG or $\Lambda$CDM. We aim to generate halo catalogues that effectively capture the distinct impact of MG, ensuring high accuracy in both two- and three-point statistics for comprehensive analysis of large-scale structures. As part of this study we aim at investigating the inclusion of MG into non-local bias to directly map the tracers onto $\Lambda$CDM fields, which would save many computational costs. We employ the bias assignment method (BAM) to model halo distribution statistics by leveraging seven high-resolution COLA simulations of MG cosmologies. Taking into account cosmic-web dependencies when learning the bias relations, we design two experiments to map the MG effects: one utilising the consistent MG density fields and the other employing the benchmark $\Lambda$CDM density field. BAM generates MG halo catalogues from both calibrations experiments excelling in summary statistics, achieving a $\sim 1\%$ accuracy in the power spectrum across a wide range of $k$-modes, with only minimal differences well below 10\% at modes subject to cosmic variance, particularly below $k<0.07$ $h$Mpc$^{-1}$. The reduced bispectrum remains consistent with the reference catalogues within 10\% for the studied configuration. Our results demonstrate that a non-linear and non-local bias description can model the effects of MG starting from a $\Lambda$CDM dark matter field., Comment: 15 pages, 10 figures, 2 tables

We analyse the fourth data release of the Kilo Degree Survey (KiDS-1000) and extract cosmological parameter constraints based on the cosmic shear peak count statistics. Peaks are identified in aperture mass maps in which the filter is maximally sensitive to angular scales in the range 2-4arcmin, probing deep into the non-linear regime of structure formation. We interpret our results with a simulation-based inference pipeline, sampling over a broad $w$CDM prior volume and marginalising over uncertainties on shape calibration, photometric redshift distribution, intrinsic alignment and baryonic feedback. Our measurements constrain the structure growth parameter and the amplitude of the non-linear intrinsic alignment model to $\Sigma_8 \equiv \sigma_8\left[\Omega_{\rm m}/0.3\right]^{0.60}=0.765^{+0.030}_{-0.030}$ and $A_{\rm IA}= 0.71^{+0.42}_{-0.42}$, respectively, in agreement with previous KiDS-1000 results based on two-point shear statistics. These results are robust against modelling of the non-linear physics, different scale cuts and selections of tomographic bins. The posterior is also consistent with that from the Dark Energy Survey Year-1 peak count analysis presented in Harnois-D\'eraps et al (2021), and hence we jointly analyse both surveys. We obtain $\Sigma_8^{\rm joint} \equiv \sigma_8\left[\Omega_{\rm m}/0.3\right]^{0.57}=0.759^{+0.020}_{-0.017}$, in agreement with the Planck $w$CDM results. The shear-CMB tension on this parameter increases to $3.1\sigma$ when forcing $w=-1.0$, and to $4.1\sigma$ if comparing instead with $S_{8,\Lambda{\rm CDM}}^{\rm joint} = 0.736^{+0.016}_{-0.018}$, one of the tightest constraints to date on this quantity. (abridged), Comment: 25 pages, 20 figures. comments welcome

We investigate a novel scenario involving asymmetric keV-range dark matter (DM) in the form of right-handed (sterile) neutrinos. Based on the Fermi-Dirac distribution, we demonstrate that asymmetric fermionic DM forms a Fermi degenerate gas, making it potentially colder than symmetric fermionic DM. This setup simultaneously accounts for the Universe's baryon asymmetry through tiny Yukawa interactions with Standard Model leptons and the Higgs field, and the homochirality of amino acids via decay into circularly polarized photons. This scenario can be investigated through soft X-ray searches conducted by current and upcoming space missions. The helical X-rays is a smoking-gun signal of our scenario. Additionally, we propose a new mechanism to suppress DM thermal production by introducing a light modulus, which may also benefit cosmology involving generic right-handed neutrinos with large mixing., Comment: 22pages, 3figures, comments are welcome

The cosmic microwave background (CMB) anisotropies are a powerful probe of the early universe, and have largely contributed to establishing the current standard cosmological model. To extract the information encoded in those tiny variations, one must first compress the raw, time-domain data collected by a telescope into maps of the sky at the observed frequencies, in a procedure known as map-making. I provide a general introduction to this problem, and highlight a few specificities of the MAPPRAISER implementation., Comment: Contribution to the 2024 Cosmology session of the 58th Rencontres de Moriond; 4 pages, 1 figure

Cosmic shear is a key probe of modern cosmology. Amongst its challenges are shape noise and intrinsic alignments, both due to our ignorance of the unlensed shape of the source galaxies. I argue here that Einstein rings may be used as standard shape to measure the external shear along their line of sight. In the Euclid era, this new observable is expected to be a competitive and complementary probe of the large-scale structure of the Universe., Comment: 4 pages, 2 figures, contribution to the 2024 Cosmology session of the 58th Rencontres de Moriond

We investigate the potential of gravitational-wave background searches to constrain cosmic histories characterised by a stiff equation of state, preceded by a period of matter domination. Such a scenario leads to a characteristic peak in the primordial gravitational-wave spectrum originating from cosmological inflation. Assuming instant transitions between distinct epochs, which allows an analytical treatment of the gravitational-wave spectrum, we perform a Bayesian inference analysis to derive constraints from the first three observing runs of the LIGO-Virgo-KAGRA Collaboration. Additionally, we consider a smooth transition, employing an axion-like particle physics model, and highlight the difference with the instant transition approximation. We then forecast detection prospects for such a cosmic history through future gravitational-wave experiments., Comment: 18 pages, 9 figures

We study a primordial black hole (PBH) formation model based on the framework of the inhomogeneous Affleck-Dine (AD) mechanism, which can explain the seeds of supermassive black holes (SMBHs). This model, however, predicts strong clustering of SMBHs that is inconsistent with the observation of angular correlation of quasars. In this paper, we propose a modified model that can significantly reduce the PBH clustering on large scales by considering a time-dependent Hubble-induced mass during inflation. The quasar angular correlation is suppressed by the large Hubble-induced mass in the early stage of inflation while the small Hubble-induced mass in the late stage leads to the AD field fluctuations large enough for PBH formation as in the original model. As a result, the modified scenario can successfully explain the seeds of SMBHs., Comment: 26 pages, 7 figures

We investigate claims of an anomalously large amplitude of the dipole in the distribution of quasars on the sky. Two main issues indicate that the systematic uncertainties in the derived quasar-density dipole are underestimated. Firstly, the spatial distribution of the quasars is not a pure dipole, possessing low-order multipoles of comparable size to the dipole. These multipoles are unexpected and presumably caused by unknown systematic effects; we cannot be confident that the dipole amplitude is not also affected by the same systematics until the origin of these fluctuations is understood. Secondly, the 50 percent sky cut associated with the quasar catalogue strongly couples the multipoles, meaning that the power estimate at ell=1 contains significant contributions from ell>1. In particular, the dominant quadrupole mode in the Galactic mask strongly couples the dipole with the octupole, leading to a large uncertainty in the dipole amplitude. Together these issues mean that the dipole in the quasar catalogue has an uncertainty large enough that consistency with the cosmic microwave background (CMB) dipole cannot be ruled out. More generally, current data sets are insufficiently clean to robustly measure the quasar dipole and future studies will require samples that are larger (preferably covering more of the sky) and free of systematic effects to make strong claims regarding their consistency with the CMB dipole., Comment: 19 pages, 9 figures

Broad absorption line quasars (BALs) exhibit blueshifted absorption relative to a number of their prominent broad emission features. These absorption features can contribute to quasar redshift errors and add absorption to the Lyman-alpha (LyA) forest that is unrelated to large-scale structure. We present a detailed analysis of the impact of BALs on the Baryon Acoustic Oscillation (BAO) results with the LyA forest from the first year of data from the Dark Energy Spectroscopic Instrument (DESI). The baseline strategy for the first year analysis is to mask all pixels associated with all BAL absorption features that fall within the wavelength region used to measure the forest. We explore a range of alternate masking strategies and demonstrate that these changes have minimal impact on the BAO measurements with both DESI data and synthetic data. This includes when we mask the BAL features associated with emission lines outside of the forest region to minimize their contribution to redshift errors. We identify differences in the properties of BALs in the synthetic datasets relative to the observational data, as well as use the synthetic observations to characterize the completeness of the BAL identification algorithm, and demonstrate that incompleteness and differences in the BALs between real and synthetic data also do not impact the BAO results for the LyA forest., Comment: 32 pages, 8 figures, submitted to JCAP

Strong AGN heating provides an alternative means for the disruption of cluster cool cores (CCs) to cluster mergers. In this work we present a systematic Chandra study of a sample of 108 nearby ($z<0.1$) galaxy clusters, to investigate the effect of AGN heating on CCs. About 40% of clusters with small offsets between the BCG and the X-ray centre ($\le50$ kpc) have small CCs. For comparison, 14 of 17 clusters with large offsets have small CCs, which suggests that mergers or sloshing can be efficient in reducing the CC size. Relaxed, small CC clusters generally have weak radio AGNs ($P_{1.4\rm GHz}<10^{23}$ W Hz$^{-1}$), and they show a lack of systems hosting a radio AGN with intermediate radio power ($2\times10^{23}

The minimal coupling of massless fermions to gravity does not allow for their gravitational production solely based on the expansion of the Universe. We argue that this changes in presence of realistic and potentially detectable stochastic gravitational wave backgrounds. We compute the resulting energy density of Weyl fermions at 1-loop using in--in formalism. If the initially massless fermions eventually acquire mass, this mechanism can explain the dark matter abundance in the Universe. Remarkably, it may be more efficient than conventional gravitational production of superheavy fermions., Comment: 6 pages, 2 figures

JWST observations have the potential to provide unprecedented constraints on the history of reionization and the sources responsible for the ionizing photons due to the detection of large populations of faint galaxies at $z\gg6$. Modelling reionization requires knowing both the number of ionizing photons that are produced by galaxies and the fraction of those photons that escape into the intergalactic medium. Observational estimates of these values generally rely on spectroscopy for which large samples with well-defined selection functions remain limited. To overcome this challenge, we present an implicit likelihood inference (ILI) pipeline trained on mock photometry to predict the escaped ionizing luminosity of individual galaxies ($\dot{n}_{\rm ion}$) based on photometric magnitudes and redshifts. Compared to traditional SED-fitting methods, the new ILI pipeline is consistently more accurate and significantly faster. We deploy the method on a sample of 4,559 high-redshift galaxies from the JADES Deep survey, finding a gentle redshift evolution of $\log_{10}(\dot{n}_{\rm ion}) = (0.08\pm0.01)z + (51.60\pm0.06)$, with late-time values for $\dot{N}_{\rm ion}$ consistent with theoretical models and observations. We measure the evolution of the volume-averaged ionized fraction and optical depth to find that observed populations of star-forming galaxies are capable of driving reionization to completion at $z\sim 5.3$ without the need for AGN or other exotic sources. The $20\%$ of UV-brightest galaxies ($M_{\rm UV}<-18.5$) in our sample can reionize only $\sim30\%$ of the survey volume, demonstrating that faint LyC emitters are crucial for reionization., Comment: 17 pages, 11 figures, 2 tables, submitted to MNRAS

A bouncing Universe avoids the big-bang singularity. Using the time-like and null Raychaudhhuri equations, we explore whether the bounce near the big-bang, within a broad spectrum of modified theories of gravity, allows for cosmologically relevant power-law solutions under reasonable physical conditions. Our study shows that certain modified theories of gravity, such as Stelle gravity, do not demonstrate singularity resolution under any reasonable conditions, while others including $f(R)$ gravity and Brans-Dicke theory can demonstrate singularity resolution under suitable conditions. For these theories, we show that the accelerating solution is slightly favoured over ekypyrosis.

In this work, we demonstrate the constraining power of the tomographic weak lensing convergence PDF for StageIV-like source galaxy redshift bins and shape noise. We focus on scales of $10$ to $20$ arcmin in the mildly nonlinear regime, where the convergence PDF and its changes with cosmological parameters can be predicted theoretically. We model the impact of reconstructing the convergence from the shear field using the well-known Kaiser-Squires formalism. We cross-validate the predicted and the measured convergence PDF derived from convergence maps reconstructed using simulated shear catalogues. Employing a Fisher forecast, we determine the constraining power for $(\Omega_{m},S_{8},w_{0})$. We find that adding a 5-bin tomography improves the $\kappa-$PDF constraints by a factor of $\{3.8,1.3,1.6\}$ for $(\Omega_{m}, S_{8},w_{0})$ respectively. Additionally, we perform a joint analysis with the shear two-point correlation functions, finding an enhancement of around a factor of $1.5$ on all parameters with respect to the two-point statistics alone. These improved constraints come from disentangling $\Omega_{\rm m}$ from $w_0$ by extracting non-Gaussian information, in particular, including the PDF skewness at different redshift bins. We also study the effect of varying the number of parameters to forecast, in particular we add $h$, finding that the convergence PDF maintains its constraining power while the precision from two-point correlations degrades by a factor of $\{1.7,1.4,1.8\}$ for $\{\Omega_{\rm m},S_8,w_0\}$, respectively., Comment: 23 pages, 21 figures

When energy is not conserved, imprints of new physics on observable cosmology might not follow the rules of local effective actions. By capturing dissipative and diffusive effects, open effective field theories account for the possibly non-Hamiltonian evolution of cosmological inhomogeneities interacting with an unspecified environment. In this proceeding, we briefly discuss recent progress made towards their implementation in primordial cosmology. Our approach recovers the usual effective field theory of inflation in a certain limit and extends it to account for local dissipation and noises. Non-Gaussianities are generated that peak in the equilateral configuration for large dissipation and in the folded configurations for small dissipation. The construction provides an embedding for local dissipative models of inflation and a framework to study quantum information aspects of the inflationary models., Comment: 8 pages, 2 figures, contribution to the 2024 Cosmology session of the 58th Rencontres de Moriond, based on arXiv:2404.15416

The IceCube neutrino telescope has detected a diffuse flux of high-energy astrophysical neutrinos, but the sources of this flux have largely remained elusive. Using the 10-year IceCube public dataset, we search for correlations between neutrino events and tracers of large-scale structure (LSS). We conduct a combined cross-correlation analysis using several wide-area galaxy catalogs spanning a redshift range of z = 0.1 to z ~ 2.5 as well as maps of the cosmic infrared background. We do not detect a definitive signal, but find tantalizing hints of a potential positive correlation between neutrinos and the tracers of LSS. We additionally construct a simple model to interpret galaxy-neutrino cross-correlations in terms of the redshift distribution of neutrino sources. We put upper limits on the clustering amplitude of neutrinos based on the measured cross-correlations with galaxies and forecast the improvements on these constraints that can be obtained using future detectors. We show that, in the future, neutrino-galaxy cross-correlations should be a powerful probe to constrain properties of neutrino source populations., Comment: 15 pages. To be submitted to PRD

Probing magnetic fields in high-redshift galactic systems is crucial to investigate galactic dynamics and evolution. Utilizing the rotation measure of the background quasars, we have developed a radial profile of the magnetic field in a typical high-$z$ galaxy. We have compiled a catalog of 59 confirmed quasar sightlines, having one intervening Mg \rom{2} absorber in the redshift range $0.372\leq z_{\text{abs}} \leq 0.8$. The presence of the foreground galaxy is ensured by comparing the photometric and spectroscopic redshifts within $3 \sigma_{z-\text{photo}}$ and visual checks. These quasar line-of-sights (LoS) pass through various impact parameters (D) up to $160$ kpc, covering the circumgalactic medium of a typical Milky-Way type galaxy. Utilizing the residual rotation measure (RRM) of these sightlines, we estimated the excess in RRM dispersion, $\sigma_{\text{ex}}^{\text{RRM}}$. We found that the sightlines having impact parameters $\text{D} \leq 50$ kpc and $\text{D} > 50$ kpc, $\sigma_{\text{ex}}^{\text{RRM}}$ show significant difference from $24.86 \pm 3.08$ rad m$^{-2}$ to $16.34 \pm 1.88$ rad m$^{-2}$ respectively. The profile of $\sigma_{\text{ex}}^{\text{RRM}}$ with D exhibits a decreasing trend. We translated $\sigma_{\text{ex}}^{\text{RRM}}$ to average LoS magnetic field strength, $\langle B_{\|}\rangle$ by considering a typical electron column density. Consequently, the anti-correlation is sustained, resulting in a decreasing magnetic field profile. This suggests a clear indication of varying magnetic field from the disk to the circumgalactic medium. This work provides a methodology that, when applied to ongoing and future radio polarisation surveys such as LOFAR and SKA, promises to significantly enhance our understanding of magnetic field mapping in galactic systems., Comment: 10 pages, 8 figures

In this talk, based on arXiv:2301.11345, arXiv:2305.16388, arXiv:2311.12694, we discuss the production of primordial gravitational waves (GW) sourced by graviton bremsstrahlung during inflationary reheating. For reheating, we consider inflaton decays and annihilations into pairs of bosons or fermions, assuming an inflaton $\phi$ that oscillates around a generic monomial potential $V(\phi) \propto \phi^n$. The GW spectrum exhibits distinct features depending on the underlying reheating dynamics, which is controlled by the inflaton potential and the type of coupling between the inflaton and the matter fields. We show that the produced stochastic GW background could be probed in next-generation GW detectors, especially at high frequencies. We further highlight the potential of bremsstrahlung-induced GW to probe the underlying dynamics of reheating., Comment: 6 pages, 4 figures. Contribution to the 2024 Electroweak session of the 58th Rencontres de Moriond. Based on Refs. arXiv:2301.11345, arXiv:2305.16388 and arXiv:2311.12694

Stars that evaporate from their star cluster by the energy equipartition process end up either in a leading or a trailing tidal tail. In Newtonian gravitation and for open star clusters in the Solar vicinity, the tidal threshold, or prah, for escape is symmetrical, such that the leading and trailing tails are equally populated. The data by six independent teams that applied the convergent point method to map out the tidal tails of four open clusters (the Hyades, the Praesepe, Coma Berenices and COIN-Gaia13) using Gaia DR2 and DR3 are here applied to test for the expected symmetry. All tidal tails contain more stars in the leading tail. The combined confidence amounts to an 8 sigma falsification of the prah symmetry. The same test using Milgromian dynamics leads to consistency with the data. More effort needs to be exerted on this matter, but the data indicate with high confidence that the tidal prah of an open star cluster is asymmetrical with the corresponding confidence that Newtonian gravitation is falsified. Open star clusters depopulate more rapidly in Milgromian than in Newtonian dynamics and the COIN-Gaia13 cluster is here found to be nearly completely dissolved. In view of these results, the wide-binary star test and the Keplerian Galactic rotation curve finding are briefly discussed., Comment: 22 pages, 14 figures, 1 table, LaTeX, ApJ, in press

Multiple fields can become dynamical during the inflationary epoch. We consider an example where a light field acquires isocurvature fluctuations during inflation and contributes to the dark matter abundance at late times. Interactions between the light field and the adiabatic sector contribute to mixed adiabatic-isocurvature non-Gaussianity (NG). We show the resulting form of NG has a different kinematic dependence than the 'local shape' commonly considered, and highlight the parameter space where a dedicated search is expected to significantly improve the current $\textit{Planck}$ sensitivity. We interpret our results in the context of the QCD axion and illustrate how the proposed NG searches can improve upon the existing searches for isocurvature power spectrum and bispectrum., Comment: 17 pages, 4 figures

We analytically calculate the spectrum of stochastic gravitational waves (GWs) emitted by expanding string loops on domain walls in the scenario where domain walls decay by nucleation of string loops. By introducing macroscopic parameters characterizing the nucleation of the loops, the stochastic GW spectrum is derived in a way that is independent of the details of particle physics models. In contrast to GWs emitted from bubble collisions of the false vacuum decay, the string loops do radiate GWs even when they are perfectly circular before their collisions, resulting in that more and more contribution to the spectrum comes from the smaller and smaller loops compared to the typical size of the collided loops. Consequently, the spectrum is linearly proportional to the frequency at the high-frequency region, which is peculiar to this GW source. Furthermore, the results are compared with the recent nano-Hertz pulsar timing array signal, as well as the projected sensitivity curves of future gravitational wave observatories., Comment: 32 pages, 8 figures

We show that by jointly fitting cosmic microwave background (CMB) and astrophysical data - a compilation of UV luminosity data from the Hubble Frontier Field and neutral hydrogen data from distant sources-, we can infer on the shape of the evolution of the ionized hydrogen fraction with redshift in addition to constraining the average optical depth $\tau$.For this purpose, we introduce here a novel extended model that includes hydrogen ionization histories which are monotonic with redshift, but allow for an asymmetry as indicated from our previous works on a free reconstruction of reionization. By using our baseline data combination, we obtain $\tau=0.0542^{+0.0017}_{-0.0028}$, consistent with our previous works and tighter than the one inferred by Planck 2018 data because of the combination of CMB with astrophysical data. We find that the symmetric hypothesis within our parametrization is disfavoured at 4 $\sigma$.We test our findings by using alternative likelihoods for CMB polarization at low multipoles, i.e. based on the 2020 reprocessing of Planck HFI data or on the joint analysis of WMAP and Planck LFI data, obtaining consistent results that disfavour the symmetric hypothesis of the reionization history at high statistical significant level.These results will be further tested by more precise astrophysical data such as from JWST and Euclid deep fields., Comment: 13 pages, 9 figures

We explore an idea put forward many years ago by Zeldovich and Novikov concerning the existence of compact objects endowed with arbitrarily small mass. The energy-density of such objects, which we call ``Ghost stars'', is negative in some regions of the fluid distribution, producing a vanishing total mass. Thus, the interior is matched on the boundary surface to Minkowski space-time. Some exact analytical solutions are exhibited and their properties are analyzed. Observational data that could confirm or dismiss the existence of this kind of stellar object is commented., Comment: 19 pages Latex. Invited contribution published in Symmetry (SI: The Nuclear Physics of Neutron Stars)

Gravitational wave (GW) detection is of paramount importance in fundamental physics and GW astronomy, yet it presents formidable challenges. One significant challenge is the removal of noise transient artifacts known as ``glitches," which greatly impact the search and identification of GWs. Recent research has achieved remarkable results in data denoising, often using effective modeling methods to remove glitches. However, for glitches from uncertain or unknown sources, current methods cannot completely eliminate them from the GW signal. In this work, we leverage the inherent robustness of machine learning to obtain reliable posterior parameter distributions directly from GW data contaminated by glitches. Our network model provides reasonable and rapid parameter inference even in the presence of glitches, without needing to remove them. We also investigate various factors affecting the rationality of parameter inference in our normalizing flow network, including glitch and GW parameters. The results demonstrate that the normalizing flow can reasonably infer the source parameters of GWs even with unknown contamination. We find that the nature of the glitch itself is the only factor that can affect the rationality of the inferred results. With improvements to our model, we anticipate accelerating the localization of electromagnetic counterparts and providing priors for more accurate deglitching, thereby speeding up subsequent data processing procedures., Comment: 13 pages, 9 figures

Cosmological observations allow to measure the abundance of light relics produced in the early Universe. Most studies focus on the thermal freeze-out scenario, yet light relics produced by freeze-in are generic for models in which new light degrees of freedom do not couple strongly enough to the Standard Model (SM) plasma to allow for full thermalization in the early Universe. In ultraviolet (UV) freeze-in scenarios, rates for light relic production associated with non-renormalizable interactions typical of beyond the SM (BSM) models grow with temperature more quickly than the Hubble rate. Thus, relatively small couplings to the SM can be probed by current and next-generation cosmic microwave background (CMB) experiments. We investigate several representative benchmark BSM models, such as axion-like particles from Primakoff production, massless dark photons and light right-handed neutrinos. We calculate contributions to the effective number of neutrino species, $\Delta N_{\rm eff}$, in corners of parameter space not previously considered and discuss the sensitivity of CMB experiments compared to other probes. In contrast to freeze-out scenarios, $\Delta N_{\rm eff}$ from UV freeze-in is more dependent on both the specific BSM physics model and the reheating temperature. Depending on the details of the BSM scenario, we find that the sensitivity of next-generation CMB experiments can complement or surpass the current astrophysical, laboratory or collider constraints on the couplings of the SM to the light relic., Comment: 26 pages, 14 figures

We simulated spin-spin interactions of $N$-bodies in linearized General Relativity (GR) and linearized Massive Gravity of the Fierz-Pauli type (mGR). It was noted earlier that there is a discrete difference between the spin-spin interaction potential in GR and mGR for a $2$-body system, akin to the van Dam-Veltman-Zakharov discontinuity in the static Newton's potential. Specifically, at large distances, GR favors anti-parallel spin orientation with total spin pointing along the interaction axis, while mGR favors parallel spin orientation with total spin perpendicular to the axis between the sources. For an $N$-body system, a simulation in mGR hitherto has not been done and one would like to know the total spin of the system in both theories. Here we remedy this. In the simulations of GR, we observed that the total spin tends to decrease from a random initial configuration, while for mGR with a large distance, the total spin increases., Comment: 11 pages, 6 figures

Merging galaxy clusters often host spectacular diffuse radio synchrotron sources. These sources can be explained by a non-thermal pool of relativistic electrons accelerated by shocks and turbulence in the intracluster medium. The origin of the pool and details of the cosmic ray transport and acceleration mechanisms in clusters are still open questions. Due to the often extremely steep spectral indices of diffuse radio emission, it is best studied at low frequencies. However, the lowest frequency window available to ground-based telescopes (10-30 MHz) has remained largely unexplored, as radio frequency interference and calibration problems related to the ionosphere become severe. Here, we present LOFAR observations from 16 to 168 MHz targeting the famous cluster Abell 2256. In the deepest-ever images at decametre wavelengths, we detect and resolve the radio halo, radio shock and various steep spectrum sources. We measure standard single power-law behaviour for the radio halo and radio shock spectra and find significant spectral index and curvature fluctuations across the radio halo, indicating an inhomogeneous emitting volume. In contrast to the straight power-law spectra of the large-scale diffuse sources, the various AGN-related sources often show extreme steepening towards higher frequencies and flattening towards low frequencies. We also discover a new fossil plasma source with a steep spectrum between 23 and 144 MHz, with $\alpha=-1.9\pm 0.1$. Finally, by comparing radio and gamma-ray observations, we rule out purely hadronic models for the radio halo origin in Abell 2256, unless the magnetic field strength in the cluster is exceptionally high, which is unsupportable by energetic arguments and inconsistent with the knowledge of other cluster magnetic fields., Comment: Accepted for publication in Astronomy & Astrophysics

Thanks to the successful performance of the James Webb Space Telescope, our understanding of the epoch of reionization of the Universe has been advanced. The ultraviolet luminosity functions (UV LFs) of galaxies span a wide range of redshift, not only revealing the connection between galaxies and dark matter (DM) halos but also providing the information during reionization. In this work, we develop a model connecting galaxy counts and apparent magnitude based on UV LFs, which incorporates redshift-dependent star formation efficiency (SFE) and corrections for dust attenuation. By synthesizing some observations across the redshift range $4\le z \le 10$ from various galaxy surveys, we discern the evolving SFE with increasing redshift and DM halo mass through model fitting. Subsequent analyses indicate that the Thomson scattering optical depth was $\tau_{\rm e} = 0.052^{+0.003}_{-0.002}$ and the epoch of reionization started (ended) at $z=20.58^{+6.25}_{-6.75}$ ($z=5.38^{+0.65}_{-0.70}$) which is insensitive to the choice of the truncated magnitude of the UV LFs. Incorporating additional dataset and some reasonable constraints, the amplitude of matter perturbation is found to be $\sigma_8=0.79\pm0.05$, which is consistent with the standard $\Lambda$CDM model. Future galaxy surveys and the dynamical simulations of galaxy evolution will break the degeneracy between SFE and cosmological parameters, improving the accuracy and the precision of the UV LF model further., Comment: 15 pages, 9 figures and 3 tables