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The time evolution of a quantum wave packet in the linear gravity potential is known as Quantum Bouncing Ball. The qBounce collaboration recently observed such a system by dropping wave packets of ultracold neutrons by a height of roughly 30 microns. In this article, space and momentum spectra as well as Wigner functions of the neutron wave functions in the gravitational field of the Earth are analyzed. We investigate the quantum states in the "preparation region", into which they transition after exiting a narrow double-mirror system and where we would expect to observe free fall and bounces in classical physics. For this, we start from the stationary solutions and eigenvalues of the Schrödinger equation in terms of Airy functions and their zeros. Subsequently, we examine space and momentum distributions as well as Wigner functions in phase space for pure and mixed quantum states. The possible influence of Yukawa-like forces for small distances of several micrometers from the mirror is included through first order perturbation calculations. Those allow us to study the resulting modifications of space and momentum distributions, and phase space functions. [ABSTRACT FROM AUTHOR]

Space debris is increasingly problematic and needs active removal, especially in low Earth orbits (LEO). Paying for the vast cost of the disposal of debris from the situation is still inevitable even though pivotal technical hurdles have been overcome with the growing maturity of capturing and deorbiting methods. To this end, a novel geomagnetic energy (GME) propellant approach is firstly proposed to propel a spinning tethered spacecraft for LEO debris deorbiting, without the use of expendable fuel and a large-length tether. In this method, the time-cumulative effect of the interacted torque of the spacecraft's electromagnet and geomagnetic field is used to accelerate the rotating system for GME storage, and the space momentum exchange from the angular momentum of system to the linear momentum of debris is introduced to deorbit the debris for GME release. Next, an on-orbit directional GME storage mechanism is built, and the corresponding two optimal strategies are put forward. Both theoretical and simulation results demonstrate that GME can be stored in the expected direction on any inclined LEO below 1000 km. Deorbiting kg-level debris can be accomplished within several orbital periods with the existing magnetorquer technology. Finally, proof-of-principle experiments of the GME effect are performed and elementarily validate the LEO GME utilization in space. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) Dirac states with linear dispersion have been observed in graphene and on the surface of topological insulators. 2D Dirac states discovered so far are exclusively pinned at high-symmetry points of the Brillouin zone, for example, surface Dirac states at Γ ¯ in topological insulators Bi2Se(Te)3 and Dirac cones at K and K ′ points in graphene. The low-energy dispersion of those Dirac states are isotropic due to the constraints of crystal symmetries. In this work, we report the observation of novel 2D Dirac states in antimony atomic layers with phosphorene structure. The Dirac states in the antimony films are located at generic momentum points. This unpinned nature enables versatile ways such as lattice strains to control the locations of the Dirac points in momentum space. In addition, dispersions around the unpinned Dirac points are highly anisotropic due to the reduced symmetry of generic momentum points. The exotic properties of unpinned Dirac states make antimony atomic layers a new type of 2D Dirac semimetals that are distinct from graphene. In graphene and on the surfaces of many topological insulators, the Dirac cones are pinned to high symmetry points in reciprocal space. Here, the authors report that the Dirac cones in atomically-thin Sb layers occur at generic reciprocal-space points which can be tuned by lattice strain. [ABSTRACT FROM AUTHOR]

The optimal momentum coupling between the ground-based laser impulse and space debris is studied. Considering the effects of diffraction, self-focusing and turbulence in the atmosphere, we derive the transcendental equation of the optimal coupling power of initial laser beams to achieve the optimal momentum coupling on the space debris and obtain the condition that the initial beam parameters (e.g., the initial beam width and the initial spatial coherence width) and atmospheric parameters (e.g., the atmospheric coherence length) should be satisfied. Thus, an effective design rule of the optimal laser–target momentum coupling is presented when a high-power laser beam propagates upward in the turbulent atmosphere. Moreover, an approximate method is proposed to derive the analytical formulae of the maximal beam power within a certain radius on the debris target and its corresponding maximal initial beam power. The results obtained in this paper is important for the application of the laser space-debris removal. [ABSTRACT FROM AUTHOR]

We propose worldsheet formulae for wavefunction coefficients of the massive non-linear sigma model (NLSM), scalar Dirac-Born-Infeld (DBI), and special Galileon (sGal) theories in de Sitter momentum space in terms of the recently proposed cosmological scattering equations constructed from conformal generators in the future boundary. The four-point integrands are assembled from simple building blocks and we identify a double copy prescription mapping the NLSM wavefunction coefficient to the DBI and sGal wavefunction coefficients, including mass deformations and curvature corrections. Finally, we compute the soft limits of these wavefunction coefficients and find that they can be written in terms of boundary conformal generators acting on contact diagrams. [ABSTRACT FROM AUTHOR]

We prove the existence of minimizers for the causal action in the class of negative definite measures on compact subsets of momentum space in the homogeneous setting under several side conditions (constraints). The method is to employ Prohorov's theorem. Given a minimizing sequence of negative definite measures, we show that, under suitable side conditions, a unitarily equivalent subsequence thereof is bounded. By restricting attention to compact subsets, from Prohorov's theorem we deduce the existence of minimizers in the class of negative definite measures. [ABSTRACT FROM AUTHOR]

It is assessed in detail both experimentally and theoretically how the interlayer coupling of transition metal dichalcogenides controls the electronic properties of the respective devices. Gated transition metal dichalcogenide structures show electrons and holes to either localize in individual monolayers, or delocalize beyond multiple layers--depending on the balance between spin-orbit interaction and interlayer hopping. This balance depends on the layer thickness, momentum space symmetry points, and applied gate fields. The design range of this balance, the effective Fermi levels, and all relevant effective masses is analyzed in great detail. A good quantitative agreement of predictions and measurements of the quantum confined Stark effect in gated MoS2 systems unveils intralayer excitons as the major source for the observed photoluminescence. [ABSTRACT FROM AUTHOR]

Shortly after Schrödinger’s wave mechanics in terms of complex wave functions was published, Madelung formulated this theory in terms of two real hydrodynamic-like equations. This version is also the formal basis of Bohmian mechanics, albeit with a different ontological interpretation. A point of criticism raised by Pauli against Bohmian mechanics is its missing symmetry between position and momentum that is present in classical phase space as well as in the quantum mechanical position and momentum representations. Both Madelung’s quantum hydrodynamics formulation and Bohmian mechanics are usually expressed only in position space. Recently, with the use of complex quantities, we were able to provide a hydrodynamic formulation also in momentum space. In this paper, we extend this formalism to include dissipative systems with broken time-reversal symmetry. In classical Hamiltonian mechanics and conventional quantum mechanics, closed systems with reversible time-evolution are usually considered. Extending the discussion to include open systems with dissipation, another form of symmetry is broken, that under time-reversal. There are different ways of describing such systems; for instance, Langevin and Fokker–Planck-type equations are commonly used in classical physics. We now investigate how these aspects can be incorporated into our complex hydrodynamic description and what modifications occur in the corresponding equations, not only in position, but particularly in momentum space.

This article discusses the recent discoveries and advancements in the field of hadron and nuclear physics. It highlights the exploration of exotic systems, such as multiquark hadrons and bound states of mesons and nuclei, which challenge traditional quark models. The article also mentions the discovery of tetraquarks and pentaquarks, as well as the recent discovery of a doubly charmed meson at the Large Hadron Collider beauty experiment. Additionally, the article explores the interactions of kaons with nuclear matter and the study of low energy interactions of anti-Kaon with light nuclei. Theoretical approaches, such as solving the Bethe-Salpeter or Lippmann Schwinger equations, are discussed, as well as the challenges of studying larger systems. The article concludes by emphasizing the ongoing surprises and extraordinary findings in the field of hadron-nuclear physics. [Extracted from the article]

We study the role of disorder in the vibration spectra of molecules and atoms in solids. This disorder may be described phenomenologically by a fractional generalization of ordinary quantum-mechanical oscillator problem. To be specific, this is accomplished by the introduction of a so-called fractional Laplacian (Riesz fractional derivative) to the Scrödinger equation with three-dimensional (3D) quadratic potential. To solve the obtained 3D spectral problem, we pass to the momentum space, where the problem simplifies greatly as fractional Laplacian becomes simply k μ , k is a modulus of the momentum vector and μ is Lévy index, characterizing the degree of disorder. In this case, μ → 0 corresponds to the strongest disorder, while μ → 2 to the weakest so that the case μ = 2 corresponds to "ordinary" (i.e. that without fractional derivatives) 3D quantum harmonic oscillator. Combining analytical (variational) and numerical methods, we have shown that in the fractional (disordered) 3D oscillator problem, the famous orbital momentum degeneracy is lifted so that its energy starts to depend on orbital quantum number l. These features can have a strong impact on the physical properties of many solids, ranging from multiferroics to oxide heterostructures, which, in turn, are usable in modern microelectronic devices. [ABSTRACT FROM AUTHOR]

China continued to gather momentum in space in 2021. With a record-breaking 55 orbital launches, the country made it again to the top of the list, ahead of the USA's 51 and Russia's 25 launches. However, nearly 90% of the Chinese launches were carried out by the state-owned Long March rocket family. In contrast, only about one-third of the US launches were made by government-funded rockets. National Science Review invited Ji Wu (吴季), an expert in space science, former director of the National Space Science Center (NSSC) of the Chinese Academy of Sciences and author of The Moon Summit, Lunar Hotel and Space Tourism, to talk about the internal and external driving forces behind the emerging private space sector in China, and government policies supporting its development since 2014. Wu also shared his insights into space tourism as a gateway to space for all, as well as his concerns for the orderly competition in the global market. [ABSTRACT FROM AUTHOR]

We analyze a variety of integration schemes for the momentum space functional renormalization group calculation with the goal of finding an optimized scheme. Using the square lattice t - t ′ Hubbard model as a testbed we define and benchmark the quality. Most notably we define an error estimate of the solution for the ordinary differential equation circumventing the issues introduced by the divergences at the end of the FRG flow. Using this measure to control for accuracy we find a threefold reduction in number of required integration steps achievable by choice of integrator. We herewith publish a set of recommended choices for the functional renormalization group, shown to decrease the computational cost for FRG calculations and representing a valuable basis for further investigations. [ABSTRACT FROM AUTHOR]

The B-meson light-cone distribution amplitude is an important non- perturbative quantity arising in the factorization of the amplitudes for many exclusive decays of B mesons, such as B− → γℓ− ν ¯ . We reconsider the renormalization-group (RG) equation satisfied by this function and present its solution at next-to-leading order (NLO) in RG-improved perturbation theory in Laplace space and, for the first time, in momentum space and the so-called diagonal (or dual) space. Since the information needed to describe the B decay processes at leading order in ΛQCD/mb is most directly contained in the distribution amplitude in Laplace space evaluated near the origin, we propose a convenient parameterization of this object in terms of a small set of uncorrelated hadronic parameters. Using recent results on the three-loop anomalous dimension for heavy-light current operators, we derive an expression for the convolution integral appearing in the B− → γℓ− ν ¯ factorization formula that is explicitly scale independent, and we evaluate this formula at (approximate) NNLO. [ABSTRACT FROM AUTHOR]

The extraction of nonperturbative TMD physics is made challenging by prescriptions that shield the Landau pole, which entangle long- and short-distance contributions in momentum space. The use of different prescriptions then makes the comparison of fit results for underlying nonperturbative contributions not meaningful on their own. We propose a model-independent method to restrict momentum-space observables to the perturbative domain. This method is based on a set of integral functionals that act linearly on terms in the conventional position-space operator product expansion (OPE). Artifacts from the truncation of the integral can be systematically pushed to higher powers in ΛQCD/kT. We demonstrate that this method can be used to compute the cumulative integral of TMD PDFs over k T ≤ k T cut in terms of collinear PDFs, accounting for both radiative corrections and evolution effects. This yields a systematic way of correcting the naive picture where the TMD PDF integrates to a collinear PDF, and for unpolarized quark distributions we find that when renormalization scales are chosen near k T cut , such corrections are a percent-level effect. We also show that, when supplemented with experimental data and improved perturbative inputs, our integral functionals will enable model-independent limits to be put on the non-perturbative OPE contributions to the Collins-Soper kernel and intrinsic TMD distributions. [ABSTRACT FROM AUTHOR]

We study the four-gluon scattering amplitude in the high energy limit of QCD written in terms of its conformal expansion. We highlight the need to include both even and odd conformal spin contributions in order to map it to an iterative representation in rapidity and transverse momentum space which we have evaluated numerically. By Fourier expanding in a set of three azimuthal angles, we find a new form for the amplitude in terms of 4F3 hypergeometric functions. An alternative formulation is possible when connecting this Fourier expansion with Bessel kernels studied in analytic number theory. [ABSTRACT FROM AUTHOR]

After nearly sixty years since its introduction, the phenomenological bell-shape Perey–Buck spatial nonlocality in the optical model potential for nucleon–nucleus scattering has remained unaccounted for from a microscopic standpoint. In this article we provide a quantitative account for such nonlocality considering fully nonlocal optical potentials in momentum space. The framework is based on a momentum-space in-medium folding model, where infinite nuclear matter g matrices in Brueckner–Hartree–Fock approximation are folded to the target one-body mixed density. The study is based on chiral next-to-next-to-next-to-leading order (N3LO) as well as Argonne v 18 nucleon–nucleon bare interaction models. Applications focus on 40 Ca(p, p) scattering at beam energies in the range 11–200 MeV, resulting in the identification of a separable structure of the momentum-space optical potential of a form we coin as JvH, with a nonlocality form factor as one of its terms. The resulting nonlocaliy form factor features a bell-shape with nonlocality range β between 0.86 and 0.89 fm, for both proton and neutron beams at energies below 65 MeV. An analytic toy model is introduced to elucidate the underlying mechanism for the nonlocality in the optical model, providing an estimate of its range based on the Fermi motion of the target nucleons and the long-range part of the NN interaction. [ABSTRACT FROM AUTHOR]

Recently, optical bound states in continuum (BICs) incorporated with optical gain have been reported to exhibit lasing. Here, it is shown that each of the four BICs supported by C4v$_{4v}$ symmetric photonic crystal slab can be made to lase, allowing the control over the topological charge of the resulting laser beam. The type of each BIC and their topological charges are identified by imaging the far‐field polarization vortices of the lasing signal. Results are compared with experimentally obtained dispersions, finite element method simulations, and multipole decomposition method based on the microscopic polarization currents in the photonic crystal plane. A demonstration of multimode lasing of two non‐degenerate BICs with opposite topological charges is presented. The momentum space overlap of the BICs results in a unique polarization pattern. The study provides a generalizable example for engineering the topological properties of coherent light. [ABSTRACT FROM AUTHOR]

Momentum-space properties of the valence electron of potassium atom are studied for 4S ground and Rydberg S-states with principal quantum number n = 5 and 6 , using an analytical momentum space wave function in quantum-defect theory. Ground state results are compared with Hartree–Fock–Roothaan and hydrogenic theory. Rydberg state results are compared with hydrogenic theory. It is found that ground state results are in good agreement with Hartree–Fock–Roothaan values showing a small difference. This deviation is primarily due to electron correlation which is included in quantum-defect theory. In Rydberg states, deviation between the results of quantum-defect theory and hydrogenic theory reduces too much with the increase in principal quantum number than ground state primarily due to unimportant effect of electron correlation in Rydberg states. Rydberg state results indicate a trend to the similarity with hydrogen atom. Comparison of Compton profiles for the ground state of the valence electron of potassium atom is shown using quantum-defect theory (QDT), Hartree–Fock (HF) and hydrogenic (H) theory. Comparison of Compton profiles for Rydberg S-states with principal quantum number η = 5 & 6 of the valence electron of potassium atom are shown using quantum-defect theory(QDT), Hartree-Fock(HF) and hydrogenic(H) theory. [ABSTRACT FROM AUTHOR]

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Engineering optical emission from two-dimensional, transition metal dichalcogenides, such as tungsten disulfide (WS2), has implications in creating and understanding nanophotonic sources. One of the challenges in controlling the optical emission from two-dimensional materials is to achieve narrow angular spread using simple photonic geometry. In this article, we study how the photoluminescence of a monolayer WS2 can be controlled when coupled to a film coupled microsphere dielectric antenna. Specifically, by employing Fourier plane microscopy and spectroscopic techniques, we quantify the wavevector distribution in the momentum space. As a result, we show the beaming of the WS2 photoluminescence with angular divergence as low as θ 1 / 2 = 4.6°. Furthermore, the experimental measurements have been supported by three-dimensional numerical simulations. We envisage that the discussed results can be generalized to a variety of two-dimensional materials and can be harnessed for on-chip nonlinear and quantum technology. [ABSTRACT FROM AUTHOR]

We report an observation of Weyl fermions in momentum space in an itinerant ferromagnet SrRuO3 single crystal via inelastic optical spectroscopy. A clear magnetic resonance around 200 GHz is observed in the Brillouin light scattering spectra, which corresponds to the ferromagnetic resonance at the Γ point. The spin-wave gap shows non-monotonous temperature dependence distinct from the bulk magnetization. The observed peculiar temperature evolution in the spin-wave gap scales with that of the anomalous Hall conductivity, which is a hallmark of Weyl fermions near the Fermi energy. [ABSTRACT FROM AUTHOR]

The neutrino dynamics in hot and dense magnetized matter, which corresponds with protoneutron star envelopes in the core collapse supernova explosions, is considered. The kinetic equation for a neutrino phase space distribution function is obtained, taking into account inelastic scattering by nuclear particles. The transfer component in a momentum space using transport properties is studied. The energy transfer coefficient is shown to change from positive to negative values when the neutrino energy exceeds four times the matter temperature. In the vicinity of a neutrino sphere, such effects are illustrated to lead to the energy strengthening in the neutrino spectra. As this paper demonstrates, such a property is favorable for the possibility of observing supernova neutrino fluxes using Large Volume Neutrino Telescopes. [ABSTRACT FROM AUTHOR]

The eigenvalue of Eq. (34) is HT ht , and the degeneracies are formed when I d i SB I x i sb = I d i SB I y i sb = 0. In other words, to get a non-zero Berry phase, HT ht should consist of complex numbers having one or more non-zero imaginary components. If HT ht consists of only real numbers, I i SB I n i sb becomes zero. A state HT ht satisfying the time-dependent Schrödinger equation is considered. Possessing this I i SB 2 sb term corresponds to the HT ht -symmetry breaking in three-dimensional space and is a necessary condition for the existence of Weyl points [[7]]. [Extracted from the article]

The concept of valley originates from two degenerate but nonequivalent energy bands at the local minimum in the conduction band or local maximum in the valence band. Manipulating the valley states for information storage and processing develops a brand-new electronicsâ€"valleytronics. Broken inversion symmetry is a necessary condition to produce pure valley currents. The polycrystalline two-dimensional materials (graphene, silicene, monolayer group-VI transition metal dichalcogenides, etc) with pristine grains stitched together by disordered grain boundaries (GBs) are the natural inversion-symmetry-broken systems and the candidates in the field of valleytronics. Different from their pristine forms, the Dirac valleys on both sides of GBs are mismatched in the momentum space and induce peculiar valley transport properties across the GBs. In this review, we systematically demonstrate the fundamental properties of valley degree of freedom across mostly studied and experimentally feasible polycrystalline structureâ€"the line defect, and the manipulation strategies with electrical, magnetic and mechanical methods to realize the valley polarization. We also introduce an effective numerical method, the non-equilibrium Green’s function technique, to tackle the valley transport issues in the line defect systems. The present challenges and the perspective on the further investigations of the line defect in valleytronics are also summarized. [ABSTRACT FROM AUTHOR]

It was shown by Kirzhnits and Chechen, following an earlier paper by Mead, that the minimum length scale l is constrained by the Mössbauer effect, which leads to the result cm, assuming the Snyder discrete space–time and conventional nuclides. Here, we note, firstly, that some recently discussed nuclides, for example , have much narrower natural line widths, which, if excited by synchrotron radiation, could potentially decrease the limiting value to cm in future experiments. The Snyder space–time and the superstring theory are both locally Lorentz invariant, and give rise to the same form of generalized indeterminacy principle, if we set , where is the Regge slope parameter, which is thus also constrained by the Mössbauer effect. For the heterotic superstring, in particular, cm, apparently beyond experimental reach. A hadron string theory at energy ~250 MeV, however, would be ruled out, since then cm. We emphasize that these results all presuppose a de Sitter momentum space, for the alternative anti-de Sitter momentum space implies no minimum length scale, and therefore seems unphysical. [ABSTRACT FROM AUTHOR]

The classical and continuum limit of a quantum gravitational setting could lead, at mesoscopic regimes, to a very different notion of geometry with respect to the pseudo-Riemannian one of special and general relativity. A possible way to characterize this modified spacetime notion is by a momentum-dependent metric, in such a way that particles with different energies could probe different spacetimes. Indeed, doubly special relativity theories, deforming the special relativistic kinematics while maintaining a relativity principle, have been understood within a geometrical context, by considering a curved momentum space. The extension of these momentum spaces to curved spacetimes and its possible phenomenological implications have been recently investigated. Following this line of research, we address here the first two laws of black holes thermodynamics in the context of a cotangent bundle metric, depending on both momentum and spacetime coordinates, compatible with the relativistic deformed kinematics of doubly special relativity. [ABSTRACT FROM AUTHOR]

The cuprate superconductors are characterised by numerous ordering tendencies, with the electronically nematic order being the most distinct form of order. Here the intertwinement of the electronic nematicity with superconductivity in cuprate superconductors is studied based on the kinetic-energy-driven superconductivity. It is shown that the optimised T c takes a dome-like shape with the weak and strong strength regions on each side of the optimal strength of the electronic nematicity, where the optimised T c reaches its maximum. This dome-like shape nematic-order strength dependence of T c thus indicates that the electronic nematicity enhances superconductivity. Moreover, this nematic order induces the anisotropy of the electron Fermi surface, where although the original electron Fermi surface contour with the four-fold rotation symmetry is broken up into that with a residual twofold rotation symmetry, this electron Fermi surface contour with the twofold rotation symmetry still is truncated to form the disconnected Fermi arcs with the most spectral weight that locates at around the tips of the Fermi arcs. Concomitantly, these tips of the Fermi arcs connected by the scattering wave vectors q i construct an octet scattering model, however, the partial scattering wave vectors and their respective symmetry-corresponding partners occur with unequal amplitudes, leading to these electronically ordered states being broken both rotation and translation symmetries. As a natural consequence, the electronic structure is inequivalent between the k x and k y directions in momentum space. These anisotropic features of the electronic structure are also confirmed via the result of the autocorrelation of the single-particle excitation spectra, where the breaking of the rotation symmetry is verified by the inequivalence on the average of the electronic structure at the two Bragg scattering sites. The theory also indicates that the order parameter of the electronic nematicity achieves its maximum in the characteristic energy and then decreases rapidly as the energy moves away from the characteristic energy. [ABSTRACT FROM AUTHOR]

We calculate the analytical and numerical values of the position space Shannon entropy, momentum space Shannon entropy, and total Shannon entropy, S ρ , S γ , and S T , respectively, of free and trapped Rydberg hydrogen-like atoms. The influence of atomic number Z, the principal quantum number n, and energy E on the Shannon entropy of the Rydberg atoms are illustrated. The scaling properties of Shannon entropy with energy of states E and the principal quantum number n have been reported for the first time to the best of our knowledge. Our work explains how Shannon entropy indicates localization-delocalization of the wavefunction. The total Shannon entropy as a measure of the number of nodes in the trapped Rydberg atom's wavefunction is also discussed. We show why an uncertainty relation based on Shannon entropy is superior to Heisenberg uncertainty for Rydberg atoms. [ABSTRACT FROM AUTHOR]

In two dimensions, an s‐wave superconductor in the presence of Rashba spin−orbit coupling possesses distinct topologically nontrivial ground‐state phases controlled by Zeeman splitting and band filling. These phases can be characterized in terms of spin textures in momentum space. Although the spin texture becomes topologically trivial at finite temperatures, thermodynamic signatures that are directly related to the topological phase transitions of the ground state are identified. In particular, relative maxima in the entropy as a function of the magnetic field in the vicinity of topological phase transitions emerge and are attributed to a sign change in the derivative of the magnetization with respect to temperature. [ABSTRACT FROM AUTHOR]

We present a basis of dimension-eight Green's functions involving Standard Model (SM) bosonic fields, consisting of 86 new operators. Rather than using algebraic identities and integration by parts, we prove the independence of these interactions in momentum space, including discussion on evanescent bosonic operators. Our results pave the way for renormalising the SM effective field theory (SMEFT), as well as for performing matching of ultraviolet models onto the SMEFT, to higher order. To demonstrate the potential of our construction, we have implemented our basis in matchmakereft and used it to integrate out a heavy singlet scalar and a heavy quadruplet scalar up to one loop. We provide the corresponding dimension-eight Wilson coefficients. Likewise, we show how our results can be easily used to simplify cumbersome redundant Lagrangians arising, for example, from integrating out heavy fields using the path-integral approach to matching. [ABSTRACT FROM AUTHOR]

In this study, a singularity-free trajectory generation algorithm of the roof-type control moment gyro (CMG) system consisting of four CMGs is proposed. Under the condition that the total angular momentum is conserved at zero, by selecting the initial gimbal angles according to the direction of the angular momentum by the roof-type CMG system, the singularity is avoided in total angular momentum space, over the wide range of the magnitude of the initial gimbal angle except near the Z-axis. The effectiveness of the algorithm is confirmed by numerical calculations, and a PD-like control using the gimbal trajectory is proposed, which is also verified by numerical simulations. [ABSTRACT FROM AUTHOR]

• Effects of injector spacing and momentum flux ratio on combustion instability in a model chamber with single and two injectors are investigated. • Combustion stabilization is consistently more effective under fuel-rich conditions. • Increasing the momentum flux ratio intensifies combustion instability regardless of the fuel condition. • For fuel-lean conditions, a rapid transition in combustion stability is observed, with the specific transition point varying depending on the injector spacing. This study investigates the effects of injector spacing and momentum flux ratio on combustion instability in a model chamber with single and two injectors, both experimentally and numerically. For the experiments, injectors similar to those used in actual rocket engines were installed in a laboratory-constructed model chamber. Numerical simulations were conducted using ANSYS Fluent, employing a detailed combustion model to complement the experimental data. Flow conditions were categorized as fuel-lean and fuel-rich based on the fuel mass flow rate. The injector spacing varied from 15 to 45 mm, and the momentum flux ratio was adjusted from 6.4 to 139.8 by manipulating the fuel and oxidizer flow rates. Both experimental and numerical results consistently revealed distinct trends in combustion instability for lean and rich conditions, influenced by injector spacing and momentum flux ratio. Combustion stabilization was consistently more effective under fuel-rich conditions. Increasing the momentum flux ratio intensified combustion instability regardless of the fuel condition. For fuel-lean conditions, a rapid transition in combustion stability was observed, with the specific transition point varying depending on the injector spacing. Considering the trade-off between instability and injector number density, a spacing of 30 mm between injectors is recommended. Additionally, for both single and two injectors with various spacings under both lean and rich conditions, combustion stability was generally better when the momentum flux ratio was less than 48.8. These findings provide valuable insights into the control and management of combustion instability, aiding in the design of rocket engine combustors. [ABSTRACT FROM AUTHOR]

This work presents two extensions of our self-consistent polarization model for treating non-valence excess electron systems. The first extension is the implementation of analytical gradients, and the second extension is the implementation of a mixed real space plus momentum space approach combined with fast Fourier transforms to reduce the computational time compared to a purely real space discrete variable representation approach. The performance of the new algorithms is assessed in calculations of the excess electron states of various size water clusters and of the non-valence correlation-bound anion of the C240 fullerene. [ABSTRACT FROM AUTHOR]

This paper introduces a systematic algorithm for deriving a new unitary representation of the Lorentz algebra (s o (1 , 3)) and an irreducible unitary representation of the extended (anti) de-Sitter algebra (s o (2 , 4)) on L 2 (R 3 , 1 r). This representation is equivalent to a representation on L 2 (R 3) , and the corresponding similarity transformation is identified. An explicit representation in terms of differential operators is given, and it is shown that the inner product is Lorentz invariant. Ensuring Lorentz covariance demands a modification of the Heisenberg algebra, recognized as a phase space algebra at the interface of gravitational and quantum realms (IGQR), which we consider subordinate to Lorentz covariance. It is also demonstrated that time evolution can be cast in a manifestly covariant form. Each mass sector of the Hilbert space carries a representation of the Lorentz algebra, and the (anti) de-Sitter algebra on each mass sector contracts to the Poincare algebra in the flat configuration and momentum space limits. Finally, we show that three-dimensional fuzzy space also carries a unitary representation of these algebras, algebraically equivalent to the L 2 (R 3 , 1 r) representation but not necessarily equivalent as representations. Several outstanding issues are identified for future exploration. • Unearthed novel Lorentz algebra representation in L 2 (R 3). • Explored quantum mechanics implications of new representation. • Challenged century-old views on time introduction for covariance. • Revealed natural emergence in 3D fuzzy space in non-commutative quantum mechanics. [ABSTRACT FROM AUTHOR]

The communication and observation spacecraft generally consists of the spacecraft body, the composite connecting beams, the working payload and the CMG/momentum wheel for integrated attitude-vibration control. When such complex space structure operates in near-Earth orbit, the sudden change in thermal load may cause a solar flux shock to the structure, which is likely to excite the flutter motion of the structure. The flutter mechanism of a rigid-flexible coupled composite space structure configured with the momentum wheel is investigated. In this study, the heat conduction equation of the composite beam appendage is derived. Then, the dynamic equations of the system influenced by the momentum wheel and composite material parameters are obtained based on the Kane's equations. Using the Routh–Hurwitz stability criterion, the stability boundaries of the flexible appendage are obtained for different composite material parameters, different operating conditions of the momentum wheel, and different attitude angular velocities. Finally, the flutter behavior is analyzed based on the dynamic response of the flexible structure and the flutter stability boundaries are verified. [ABSTRACT FROM AUTHOR]

We show that in the presence of the Snyder algebra the notion of translation in momentum space is modified to a formula similar to the relativistic addition of velocities. These results confirm the strict connection between Snyder algebra and the Lorentz group. [ABSTRACT FROM AUTHOR]

We perform hysteresis-loop measurement and domain imaging for (1 1 ¯ 00) -oriented D019-Mn3+xSn1-x (− 0.11 ≤ x ≤ 0.14) thin films using the magneto-optical Kerr effect (MOKE) and compare it with the anomalous Hall effect (AHE) measurement. We obtain a large Kerr rotation angle of 10 mdeg, comparable with bulk single-crystal Mn3Sn. The composition x dependence of AHE and MOKE shows a similar trend, suggesting the same origin, i.e., the non-vanishing Berry curvature in the momentum space. Magnetic domain observation at the saturated state shows that x dependence of AHE and MOKE is explained by the amount of the reversible area that crucially depends on the crystalline structure of the film. Furthermore, in-depth observation of the reversal process reveals that the reversal starts with nucleation of sub-micrometer-scale domains dispersed in the film, followed by domain expansion, where the domain wall preferentially propagates along the [ 11 2 ¯ 0 ] direction. Our study provides a basic understanding of the spatial evolution of the reversal of the chiral-spin structure in non-collinear antiferromagnetic thin films. [ABSTRACT FROM AUTHOR]

A Brillouin zone is the unit for the momentum space of a crystal. It is topologically a torus, and distinguishing whether a set of wave functions over the Brillouin torus can be smoothly deformed to another leads to the classification of various topological states of matter. Here, we show that under Z 2 gauge fields, i.e., hopping amplitudes with phases ±1, the fundamental domain of momentum space can assume the topology of a Klein bottle. This drastic change of the Brillouin zone theory is due to the projective symmetry algebra enforced by the gauge field. Remarkably, the non-orientability of the Brillouin Klein bottle corresponds to the topological classification by a Z 2 invariant, in contrast to the Chern number valued in Z for the usual Brillouin torus. The result is a novel Klein bottle insulator featuring topological modes at two edges related by a nonlocal twist, radically distinct from all previous topological insulators. Our prediction can be readily achieved in various artificial crystals, and the discovery opens a new direction to explore topological physics by gauge-field-modified fundamental structures of physics. Topological states are exploited based on crystalline symmetry, but under artificial gauge fields, symmetries may satisfy projective algebras, which remains less studied. Here, the authors reveal that projective symmetry algebra leads to momentum-space nonsymmorphic symmetry, resulting in new topological states over a momentum-space Klein bottle. [ABSTRACT FROM AUTHOR]

Ultrashort laser pulses have been utilized to dynamically drive phase transitions in correlated quantum materials. Of particular interest is whether phases not achievable in thermal equilibrium can be induced in complex oxides with intricately coupled lattice, electron and spin degrees of freedom. Here, we tracked atomic motions in LaMnO3 following photoexcitation with MeV ultrafast electron diffraction (MeV-UED) technique. We found that the light excited state exhibits numerous signatures different from thermal equilibrium ones, including nearly conserved Bragg intensities, strongly suppressed La cation and oxygen anion displacements, and the long-range lattice orthorhombicity evolution. Furthermore, using first-principles calculations, we predict that the ferromagnetic ordering and conductivity are both enhanced upon laser excitation due to the reduction of the lattice orthorhombicity. This work benefits from recent advance in fabrication of membrane films with high epitaxial quality and in MeV-UED with large momentum space access and high temporal resolution. [ABSTRACT FROM AUTHOR]

A flat band structure in momentum space is considered key for the realization of novel phenomena. A topological flat band, also known as a drumhead state, is an ideal platform to drive new exotic topological quantum phases. Using angle-resolved photoemission spectroscopy experiments, we reveal the emergence of a highly localized surface state in a topological semimetal BaAl 4 and provide its full energy and momentum space topology. We find that the observed surface state is localized in momentum, inside a square-shaped bulk Dirac nodal loop, and in energy, leading to a flat band and a peak in the density of state. These results imply this class of materials as an experimental realization of drumhead surface states and provide an important reference for future studies of the fundamental physics of correlated quantum effects in topological materials. [ABSTRACT FROM AUTHOR]

The functional renormalization group (FRG), an established computational method for quantum many-body phenomena, has been subject to a diversification in topical applications, analytic approximations and numerical implementations. Despite significant efforts to accomplish a coherent standard through benchmarks and the reproduction of previous results, no systematic and comprehensive comparison has been provided until now. While this has not prevented the publication of relevant scientific results we argue that established mutual agreement across realizations will strengthen confidence in the method. To this end, we report explicit implementational details and numerical data reproduced thrice independently up to machine accuracy. To substantiate the reproducibility of our calculations, we scrutinize pillar FRG results reported in the literature, and discuss our calculations of these reference systems. We mean to entice other groups to reproduce and establish this set of benchmark FRG results thus propagating the joint effort of the FRG community to engage in a shared knowledge repository as a reference standard for FRG implementations [ABSTRACT FROM AUTHOR]

We construct the deformed ladder operators in the presence of a minimal length to study the one- and two-mode squeezed harmonic oscillator. The generalized Hamiltonian of the system is expressed in terms of a deformed algebra. The realizations of this algebra allow us to convert the purely quantum mechanical problem of the model into a differential equation. By means of the Nikiforov–Uvarov method, the energy eigenvalues are obtained and the corresponding wave functions, in the momentum space, are expressed in terms of hypergeometric functions. Our study shows that the domain of existence of the energy levels is extended and this extension is due to the deformation parameter. [ABSTRACT FROM AUTHOR]

We discuss in depth the interpretation of the quantum states of the model of a triaxial rotor coupled to an odd-particle (PTR). The limitations caused by the discreteness and finiteness of the angular momentum Hilbert space are discussed in detail. We introduce the spin coherent state representation, which directly extracts the classical features from the quantum states. For the triaxial rotor model, the relation to the classical motion of the angular momentum vector is analysed in detail. Two-dimensional plots of the probability distributions of the spin coherent states are used to generalize the classification of the collective excitations of the PTR as transverse and longitudinal wobbling modes based on their topologies. The transition from the transverse to the longitudinal regime with increasing angular momentum is analysed for the first time in full detail, which reveals the appearance of a flip mode in the transition region and that the small-amplitude approximation predicts a too early break-down of the transverse wobbling regime. The relation between the transverse-longitudinal classification and alternative terminology from the literature is clarified. [ABSTRACT FROM AUTHOR]

For a certain translationally invariant tight-binding model of 3D Weyl semimetals, we establish a bulk–edge correspondence as an equality of two relative homology classes, based on an idea of Mathai and Thiang: [ 14 ] and [ 15 ] From spectral information on the edge Hamiltonian, we construct a relative homology class on the surface momentum space. This class agrees with the image under the surface projection of a homology class on the bulk momentum space relative to the Weyl points, constructed from the bulk Hamiltonian. Furthermore, the relative homology class on the surface momentum space can be represented by homology cycles whose images constitute Fermi arcs, the loci where the edge Hamiltonian admits a zero spectrum. [ABSTRACT FROM AUTHOR]

[Display omitted] The complete band representations (BRs) have been constructed in the work of topological quantum chemistry. Each BR is expressed by either a localized orbital at a Wyckoff site in real space, or by a set of irreducible representations in momentum space. In this work, we define unconventional materials with a common feature of the mismatch between average electronic centers and atomic positions. They can be effectively diagnosed as whose occupied bands can be expressed as a sum of elementary BRs (eBRs), but not a sum of atomic-orbital-induced BRs (aBRs). The existence of an essential BR at an empty site is described by nonzero real-space invariants (RSIs). The "valence" states can be derived by the aBR decomposition, and unconventional materials are supposed to have an uncompensated total "valence" state. The high-throughput screening for unconventional materials has been performed through the first-principles calculations. We have discovered 423 unconventional compounds, including thermoelectronic materials, higher-order topological insulators, electrides, hydrogen storage materials, hydrogen evolution reaction electrocatalysts, electrodes, and superconductors. The diversity of these interesting properties and applications would be widely studied in the future. [ABSTRACT FROM AUTHOR]

Nonequilibrium quantum dynamics of many-body systems is the frontier of condensed matter physics; recent advances in various time-resolved spectroscopic techniques continue to reveal rich phenomena. Angle-resolved photoemission spectroscopy (ARPES) as one powerful technique can resolve electronic energy, momentum, and spin along the time axis after excitation. However, dynamics of spin textures in momentum space remains mostly unexplored. Here, we demonstrate theoretically that the photoexcited surface state of genuine or magnetically doped topological insulators shows intriguing topological spin textures (i.e., tornado-like patterns) in the spin-resolved ARPES. We systematically reveal its origin as a unique nonequilibrium photoinduced topological winding phenomenon. As all intrinsic and extrinsic topological helicity factors of both material and light are embedded in a robust and delicate manner, the tornado patterns not only allow a remarkable tomography of such important system information, but also enable various unique dichroic topological switchings of the momentum-space spin texture. These results open a direction of nonequilibrium topological spin states in quantum materials. [ABSTRACT FROM AUTHOR]

After a brief outline of general aspects of conformal field theories in coordinate space, in a first part we review the solution of the conformal constraints of three- and four-point functions in momentum space in dimensions d ≥ 2 , in the form of conformal Ward identities (CWIs). We center our discussion on the analysis of correlators containing stress–energy tensors (T) , conserved currents (J) , and scalar operators (O). For scalar four-point functions, we briefly discuss our method for determining the dual conformal solutions of such equations, identified only by the CWIs, and related to the conformal Yangian symmetry, introduced by us in previous work. In correlation functions with T tensors, evaluated around a flat spacetime, the conformal anomaly is characterized by the (non-local) exchange of massless poles in specific form factors, a signature that has been investigated both in free field theory and non-perturbatively, by solving the conformal constraints. We discuss the anomaly effective action, and illustrate the derivation of the CWIs directly from its path integral definition and its Weyl symmetry, which is alternative to the standard operatorial approach used in conformal field theories in flat space. For two- and three-point functions, we elaborate on the matching of these types of correlators to free-field theories. Perturbative realizations of CFTs at one-loop provide the simplest expressions of the general solutions identified by the CWIs, for generic operators T , J , and scalars of specific scaling dimensions, by an appropriate choice of their field content. In a technical appendix we offer details on the reconstruction of the T T O and T T T correlators in the approach of Bzowski, McFadden and Skenderis, and specifically on the secondary Ward identities of the method, in order to establish a complete match with the perturbative description. [ABSTRACT FROM AUTHOR]

Topological semimetals with symmetry-protected band crossings have emerged as a rich landscape to explore intriguing electronic phenomena. Nonsymmorphic symmetries in particular have been shown to play an important role in protecting the crossings along a line (rather than a point) in momentum space. Here we report experimental and theoretical evidence for Dirac nodal line crossings along the Brillouin zone boundaries in PtPb4, arising from the nonsymmorphic symmetry of its crystal structure. Interestingly, while the nodal lines would remain gapless in the absence of spin–orbit coupling (SOC), the SOC, in this case, plays a detrimental role to topology by lifting the band degeneracy everywhere except at a set of isolated points. Nevertheless, the nodal line is observed to have a bandwidth much smaller than that found in density functional theory (DFT). Our findings reveal PtPb4 to be a material system with narrow crossings approximately protected by nonsymmorphic crystalline symmetries. [ABSTRACT FROM AUTHOR]