Papers

Quantum geometry governs a wide array of physical observables in topological quantum materials. In its ideal limit, quantum geometry yields exact bounds and analytical results for a growing class of observables. However, a comparable framework for the shift current remains elusive because it depends on geometric relations between multiple bands. In this work, we show that the shift current is proportional to the cyclotron shift, the displacement of the cyclotron center induced by Landau-level mixing. This mechanism yields a universal scaling law: the integrated weight and the peak magnitude scale as $l^{i+1-n}$ and $l^{2i+1-n}$ in the magnetic length or moiré period $l$, where $n$ is the momentum order of the symmetry-breaking perturbation and $\Delta E \propto l^{-i}$ is the level spacing. We verify the scaling law in exactly solvable chiral-$N$ Landau levels under a uniform magnetic field and in Schrödinger and Dirac moiré skyrmion crystals, which capture the flat Chern bands of twisted MoTe$_2$ and twisted bilayer graphene. For a Schrödinger flat band with a distorted skyrmion texture, the integrated weight grows linearly with the moiré period and the resonant peak grows cubically.

A quantum field-theoretical description of neutrino oscillations in matter in adiabatic approximation is developed. Estimates of the oscillation coherence lengths have been made for several solar neutrino production and detection processes. It has been shown that, within the framework of the developed approach, the results of solar neutrino detection experiments can be correctly described in terms of neutrino mass eigenstates without taking oscillations into account.

A common belief in Kondo physics is that a magnetic impurity can act as an efficient probe of key properties of its host bath. In altermagnets, however, this intuition fails in a symmetry-enforced way: the momentum-dependent spin splitting cancels in the local impurity spectrum, making a conventional single-impurity Kondo resonance essentially blind to the altermagnetic form factor. Here, we overcome this constraint by introducing Floquet symmetry conversion. We show that an in-plane AC field converts the hidden altermagnetic spin splitting into a locally detectable spin-dependent hybridization channel, which is further amplified by Kondo correlations into a novel altermagnetic Kondo effect. Remarkably, the Kondo splitting exhibits a nontrivial dependence on the field orientation and inherits the same crystalline form factor as the altermagnetic host, thereby serving as Kondo tomography of altermagnetic spin splitting. This field-controlled response further provides a natural route to symmetry-controlled Kondo logic gates. Our results establish a field-controllable altermagnetic Kondo effect, linking symmetry-resolved impurity spectroscopy to Kondo logic functionality.

This work presents a consistent formulation of body-force and heat-source terms within a double-distribution-function lattice Boltzmann framework for simulating compressible flows of generic fluids. The proposed approach extends a recently developed kinetic framework for non-ideal compressible fluid dynamics by incorporating external forcing and volumetric heating through shifted quasi-equilibrium states. The standard lattice Boltzmann discretization is applied with a second-order accurate integration along characteristics and product-form equilibria on nearest-neighbor lattices are employed, supplemented by necessary correction terms. This formulation ensures the consistent recovery of the Navier-Stokes-Fourier equations, including the Korteweg stress tensor, across arbitrary equations of state, while maintaining independently controllable thermodynamic and transport coefficients. The methodology is rigorously validated and applied for two different flow regimes, with ideal-gas compressible flows and non-ideal/multiphase compressible flows, respectively, where a broad hierarchy of benchmarks is employed, including non-classical shock tubes, thermal Couette flows, and force-driven Poiseuille and Womersley flows. The framework's ability to capture complex thermodynamic processes using forcing and heating is further demonstrated through Rayleigh and Fanno flows, Joule-Thomson effects, and throttling processes. Furthermore, the model is validated for multiphase phenomena, including interface consistency and liquid-vapor co-existence. The results demonstrate excellent agreement with analytical solutions and reference data, while spatio-temporal grid-refinement studies confirm the expected second-order accuracy of the scheme. This establishes the model as a robust and efficient foundation for simulating highly compressible flows of generic fluids in the presence of numerical and physical s...

Tin monosulfide (SnS) is a layered IV-VI semiconductor with strong in-plane anisotropy and promising properties for optoelectronic and ferroic applications. However, obtaining large, continuous, and morphologically well-defined SnS crystals remains challenging. Here, we report the growth of large-area SnS crystals using chemical vapor deposition with separate elemental Sn and S precursors. By controlling the precursor temperatures, source positions, substrate temperature, carrier-gas flow, and hydrogen flow, we obtain SnS crystals with lateral dimensions approaching 350 micrometers. The optimized growth occurs with the Sn source at approximately 750 degrees C, the S source at approximately 230 degrees C, and the substrate maintained near 650-680 degrees C, using Ar/H2 flow rates of 120/10 sccm. X-ray diffraction shows a dominant SnS (111) reflection with no detectable secondary crystalline tin-sulfide phase within the measurement sensitivity. Raman spectroscopy reveals six characteristic SnS phonon modes at approximately 39.3, 48.8, 95.2, 165.0, 193.1, and 219.1 cm^-1. In particular, the low-frequency modes near 39 and 49 cm^-1 are clearly resolved with FWHM values of approximately 2.52 and 2.37 cm^-1, respectively. SEM and AFM measurements further show large continuous crystals and a relatively smooth nanoscale surface. Growth on mica produces more regular square and rectangular flakes, with lateral dimensions approaching 300 x 300 micrometers, while crystals grown on SiO2/Si are more frequently fractured or irregular at their edges. These results demonstrate a practical growth window for obtaining large-area SnS crystals suitable for further optical, electrical, and device studies.

The origin of ultra-high-energy cosmic rays (UHECRs) remains elusive, as proposed acceleration mechanisms are rarely connected directly to composition-sensitive air-shower observables. We establish such a connection for voltage-drop acceleration in near-horizon current sheets of magnetically arrested disks around supermassive black holes. Fragmentation is represented by a log-normal distribution of effective potential-sampling factors $\eta$, with $\mu_\eta=\langle\ln\eta\rangle$, $\sigma_\eta=[\mathrm{Var}(\ln\eta)]^{1/2}$, and median $\widetilde{\eta}=e^{\mu_\eta}$, while the energy gain scales with nuclear charge $Z$ and maximum potential $\mathcal{V}_{\max}$. We propagate the accelerated particles through Bethe–Heitler and adiabatic losses, proton photopion attenuation, and a mass-evolving photodisintegration cascade, and predict $\langle X_{\max}\rangle$ and $\sigma(X_{\max})$. We perform Bayesian fits to the Pierre Auger Observatory 2025 DNN measurements for two fixed injection templates and propagation distances of 10, 30, and 100 Mpc. An Auger-inspired, proton-poor injection reproduces both shower moments at 10 and 30 Mpc, with $\chi^2/\nu=0.33$ and $0.47$. At 30 Mpc, $\sigma_\eta=0.59^{+0.13}_{-0.10}$, corresponding to a multiplicative dispersion of approximately 1.8. The median sampling factor and maximum potential remain strongly degenerate, with $\widetilde{\eta}\mathcal{V}_{\max}$ more directly constrained. A metal-enriched injection containing $\sim53\%$ hydrogen gives $\chi^2$ larger by 17.9 and 25.9 at 10 and 30 Mpc. Both templates remain viable at 10 and 30 Mpc but fit poorly at 100 Mpc. Within the scenarios tested, the results favour a relatively proton-poor accelerated population and show that the shower-width evolution can constrain the stochastic structure of electric-field acceleration in nearby AGN.

The physics of convective boundary mixing involves concepts such as penetration and overshooting and has been mostly characterized for envelope and core convection. For the burning shells deep inside massive stars in their final stages, the convective boundary remains poorly understood. 1D stellar-evolution codes typically place a steep entropy gradient and the corresponding narrow \brunt{} ($N^2$) peak at a lower convective shell boundary. Based on high-resolution 3D hydrodynamic simulations of a $25 \rm{M_\odot}$ star 11 days before core collapse, we find that convection excites high-frequency internal gravity waves at the $N^2$ peak representing the C-shell convection bottom. These waves efficiently mix entropy and species and the $N^2$ peak erodes by ${\sim}40\%$ within hours, correspondingly reducing the entropy gradient. The wave-driven diffusion coefficient is $D\approx 5\text{--}6\times 10^{9} \rm{cm}^2 \rm{second}^{-1}$ at the $N^2$ peak in numerically converged simulations. Our simulations show that the dominant physics at this boundary is mixing due to internal gravity waves. Extrapolated with the time-dependent $D$ coefficient from the 3D simulations, the entropy step across the peak decreases by 40–85% within half a day, thereby reducing the density, temperature and entropy gradients that set the accretion-rate drop a stalled supernova shock encounters. This physics is not included in present-day 1D models and enters the structural parameters that predict explodability. Flattening the gradients days before collapse favors an O–C shell merger, which could reshape pre-collapse nucleosynthesis. Without this physics 1D models carry too sharp gradients that introduce previously unaccounted systematic errors into the explodability surveys, yield tables and chemical-evolution studies built on them.

We report on a new beam current monitor system based on work originally done to develop timing planes for future collider detectors. In contrast to sensors based on wall currents or toroid inductance, we make use of electric field induced by the electromagnetic vector potential of the beam current as it passes near or through a transmission line (TL), arranged with its dominant TEM or TE10 fields aligned with the current, thus directly coupling to TL modes. For resonantly extracted proton pulses currently being commissioned at the Fermilab Delivery Ring, we utilized a TEM parallel-plate TL geometry, since the requirements included measuring the structure of the bunch over $\sim{}200~\rm{ns}$ time scales. We present the design and results of simulated and realized sensors now deployed at Fermilab for future use as pulse-to-pulse proton intensity monitors at the Mu2e experiment. In addition, inspired by this and prior work, we investigate the use of broadband mm-wave dual-ridge waveguides as a means of measuring substructure of nanosecond bunches down to the tens of picosecond level for future use at the Long Baseline Neutrino Facility (LBNF).

We extend geometric parallel transport from states and degenerate eigenspaces to observable algebras defining generalized quantum subsystems. At fixed block structure, unitary invariance fixes a unique connection, recovering Berry–Wilczek–Zee transport on bands. On positive-dimensional strata, its holonomy is the special-unitary part of the normalizer: all inner logical gates and equal-type sector permutations are attainable. Given a compatible gapped Hamiltonian and access to the required paths, inner gates can be implemented adiabatically by isospectral control of a band refinement.

Particle shower simulation is a major computational cost in high-energy physics. Monte Carlo methods such as Geant4 are accurate but expensive, while most machine learning surrogates are tied to specific detector geometries and require retraining for each design change. We study cross-geometry transfer learning with CaloClouds II, a generative model that produces point clouds rather than voxels and can project onto arbitrary detector readouts. We pre-train on photon showers in the International Large Detector (ILD) and adapt to electron showers in the cylindrical CaloChallenge Dataset 3. With only 100 target showers, fine-tuning reduces the geometric mean Wasserstein distance to Geant4 by about 51% over training from scratch. Bias-only fine-tuning (BitFit) stays within 5% of full fine-tuning while updating only 17% of the diffusion network parameters. We also examine model collapse in CaloClouds II by retraining its normalising flow and diffusion model on its own generated showers across successive generations.

A general physics-based model for the distribution of shear stress and surface pressure is developed for laminar flow over spheres. Although integral coefficients have been studied extensively for spheres, they do not capture the local surface distributions that govern phenomena such as heat transfer, phase change, and mass loss in multiphase and particle-laden flows. The model depends on the flow regime of the sphere ($Re_\infty$, $M_\infty$, $Kn_\infty$), local gas properties ($\gamma$, $\omega$, $Pr$), and surface conditions ($T_w/T_0$, $\sigma_t$, $\sigma_n$). The formulation incorporates boundary-layer scaling, flow separation, shock-wave physics, velocity-slip effects, and high-speed rarefaction, while recovering the known asymptotic behavior in the creeping-flow, hypersonic, and free-molecular limits. The proposed model is validated in the continuum and rarefied regimes using CFD and DSMC simulations from literature. In the continuum regime, it is compared with CFD simulations of flow over a sphere in air under subsonic, supersonic, and hypersonic conditions with varying surface temperatures. The model captures the CFD distributions very well over a wide range of $Re_\infty$, $M_\infty$, and $T_w/T_0$. In the rarefied regime, it is compared with DSMC simulations of flow over a sphere in a monatomic gas under subsonic and supersonic conditions with fully diffuse and partial surface accommodation. It shows good agreement with the simulated shear stress and surface pressure distributions over a wide range of $M_\infty$ and $Kn_\infty$, while accurately capturing the effects of surface accommodation around spherical bodies.

We report forward random-circuit sampling (RCS) on the 120-qubit Nighthawk r2 superconducting processor (ibm_phoenix) with square-lattice connectivity, using 61 qubits, native CZ gates, and the standard cloud execution stack with no benchmark-specific calibration. Two independent fidelity estimators—mirror benchmarking and three- and four-patch cross-entropy benchmarking (XEB)—agree with each other at every measured depth, the mirror from 4 to 40 cycles and the patched estimators from 20 to 40 cycles, across more than two orders of magnitude of fidelity decay, and exceed the first-generation Nighthawk r1 device by more than an order of magnitude at fixed depth. The 36-cycle circuits sit at the depth where tensor-network contraction cost saturates at system size: a contraction-cost estimator validated against the published Sycamore and Zuchongzhi networks places the single-amplitude cost at $\sim$$10^{22}$ complex operations. At $F_{\mathrm{XEB}}(36)=2.3\times10^{-3}$ under favorable memory assumptions this implies $1.2\times10^{27}$ machine operations within the bounded-fidelity rejection-sampling model — more than a century of runtime on the Frontier supercomputer — to collect a $10^{6}$-sample ensemble, which takes only 19\,s on Nighthawk r2. To our knowledge, this is the first demonstration of quantum advantage for a vanilla random-circuit sampling on a commercially and broadly accessible quantum processor that most non-expert quantum computer users can easily replicate.

We present the first 3D radiation hydrodynamical simulation of the outer envelope of a blue supergiant. These near Eddington limited massive stars in the Hertzsprung gap exhibit substantial photometric variability and have spectroscopic line widths indicating unexplained macroturbulent velocity fields. Our Athena++ simulations find that the convection associated with the opacity peak from iron directly extends to the photosphere, as found in previous 3D simulations of massive main sequence stars. Unlike 1D stellar models, this single convecting region imprints a velocity field that is consistent with spectroscopic models of macroturbulence. In addition, the convection in the outermost layer leads to such large density variations that the exiting radiation varies on large ($\lesssim 10 \% $) amplitudes and short ($\sim$ days) timescales. This leads to stochastic low frequency (SLF) photometric variability, with amplitudes and power spectra broadly consistent with observations.

We study the Bayesian monitoring of a single particle diffusing along a line, while an observer tracks it continuously using noisy measurements at each spatial point. The average Shannon entropy $\overline{S(t)}$ associated with the posterior distribution of the particle's position quantifies the uncertainty that remains after conditioning on the sequence of measurements. We map the problem to the calculation of the moments of the partition functions of directed polymers in $1 + 1$ dimensions. For a constant monitoring rate, the entropy remains bounded for any finite measurement intensity and can be quantified using exact results from the Kardar-Parisi-Zhang equation, providing both the saturation value and the asymptotic behavior for long times. For a monitoring intensity that decreases according to a power law $\sim t^{-\alpha}$, two distinct asymptotic regimes emerge: $\overline{S(t)} \simeq \tfrac12 \ln t$ for $\alpha > 1/2$ and $\overline{S(t)} \simeq \alpha \ln t$ for $0 < \alpha < 1/2$. Both results are obtained using the replica method, which maps the problem onto an attractive Lieb-Liniger Hamiltonian with a time-dependent coupling: the two regimes can be understood from a perturbative expansion around free diffusion and around the attractive Lieb-Liniger ground state, respectively. We discuss the limiting case $\alpha = 1/2$ and compare the predictions with simulations of discrete Gaussian and log-gamma polymer models.

We present a comprehensive, homogenised catalogue of $32{,}552{,}876$ stellar sources with full 6D phase-space information, spanning Galactocentric distances from the inner galaxy ($\gtrsim 5$\,kpc) to the outer halo ($\sim\!250$\,kpc). By cross-matching Gaia DR3 astrometry with spectrophotometric distances and line-of-sight velocities from 14 surveys (including desi, sdss-boss, apogee, lamost, galah, and ges), we achieve median fractional distance uncertainties of $\approx2.7\%$ for $d_{\rm helio}\le15$\,kpc, and $\approx29\%$ for $15<d_{\rm helio}\le250$\,kpc. The catalogue-wide median fractional radial velocity uncertainty is $\approx8.31\%$. Gaia-anchored zero-point corrections and statistical normalisation suppress both random and systematic errors. Furthermore, we derive spectrophotometric parallaxes from joint photometric and spectroscopic data. Overlapping survey data is aggregated to replace unreliable values and supplement absent velocities, improving completeness and internal consistency. This multi-survey synthesis is externally validated against globular clusters, dwarf galaxies, and stellar streams, yielding precise kinematics. Notably, the sample features $517{,}123$ halo stars extending well beyond the Gaia parallax limit ($\gtrsim\!10$\,kpc). These predominantly faint ($G > 17$) and metal-poor ($[\mathrm{Fe/H}] < -1$) tracers, including RR~Lyrae, blue horizontal-branch, and K~giant stars, constitute the largest well-calibrated sample of outer-halo tracers to date. This unique dataset is ideal for multi-component mass modelling, galactic archaeology, and dark matter searches across the Milky Way.

Neutron stars endowed with purely poloidal or purely toroidal magnetic fields are known to be unstable, and settle into mixed poloidal-toroidal configurations. The end state of these instabilities is still poorly understood. It is unclear whether this state is unique or whether the dynamically stable configuration has memory of the initial conditions. In this work, we perform long-term, fully general relativistic magnetohydrodynamic simulations of equilibrium configurations of slowly rotating neutron stars endowed with self-consistent mixed poloidal and toroidal magnetic fields. Our initial configurations differ in their initial magnetization and magnetic field geometry. We evolve the initial equilibria for tens of Alfvén timescales until well after any instabilities have saturated. Employing an array of diagnostic tools from visualizations to the structure of the plasma four-current and a vector spherical harmonic decomposition of the settled magnetic fields, we characterize the structure of the dynamically stable, settled magnetic equilibria. We find that the settled configurations are not unique. Instead, they exhibit diverse multipolar structures, with higher-order modes contributing substantially. Our findings demonstrate that there is memory of the magnetic-field initial conditions, and that there is no unique dynamically stable magnetic-field geometry for neutron stars. Nevertheless, we find that the angle-averaged radial profile of the magnetic field toroidal to poloidal amplitude in the bulk of the settled configurations exhibits some degree of universality with typical values of order \(20\)–\(40\%\).

Most stars form in massive stellar clusters, where intense far-ultraviolet (FUV) radiation from OB stars can accelerate the dispersal of protoplanetary disks through external photoevaporation. Quantifying the impact of this process on disk evolution remains challenging, particularly in distant and crowded star-forming regions. We investigate the low-mass stellar population in the highly irradiated center of Trumpler 14 and examine how the local FUV radiation field influences circumstellar disk evolution. We extracted stellar spectra from VLT/MUSE observations using an enhanced background-optimized extraction method, carefully corrected for instrumental response as a function of wavelength and finally derived the stellar parameters with the SAPSAL deep-learning framework. We combined these results with a probabilistic estimate of the local FUV field and near-infrared photometry to identify disk-bearing stars. We identify 310 bona fide cluster members with an age of $0.66^{+0.73}_{-0.35}$ Myr and local radiation fields spanning $\log(FUV)\simeq4.2-6.0\ G_{\mathrm{0}}$. The fraction of stars exhibiting near-infrared excess decreases from 30% at the lowest FUV fluxes to under 5% at $\log(FUV)\gtrsim5.6 \ G_{\mathrm{0}}$, while no significant correlation is found between our simplified estimate of the optical veiling and the local FUV field. The pronounced decline in the disk fraction with ambient FUV flux provides strong evidence for external photoevaporation rapidly dispersing circumstellar disks in the core of Trumpler 14. Our results confirm previous disk dispersal estimates and extend to higher values of the FUV field strength.

Repeated evaluation of the single-particle Green's function (GF) across parameter space is a recurring bottleneck in many-body methods, limiting the resolution at which phase boundaries may be probed and the frequency resolution of computed spectra. We introduce MOR+EC, a framework that constructs reusable reduced-order models for computing single-particle Green's functions by combining eigenvector continuation (EC) for parameter space exploration and model order reduction (MOR) for extrapolation in frequency space. Contrary to conventional parameterized MOR, we construct these reduced-order models with a parameter-independent resolvent, further reducing the number of required full-space evaluations. Benchmarking against exact diagonalization as the impurity solver for our example case of DMFT calculations for single- and two-band models, MOR+EC reproduces the DMFT-converged impurity GF to an average relative error below $10^{-3}$, with a median wall-time speedup of $9.5$-$92\times$. This accuracy and efficiency together resolve a fine-grained scan of the impurity occupation as doping is tuned and produce a high-resolution phase diagram of an orbital-selective Mott transition. The reduced-order model also reproduces real- and imaginary-frequency spectra at no additional cost in full-space evaluations. This framework applies broadly to GF-based methods requiring repeated parametric evaluation and high resolution of the frequency axis.

Key properties of a large sparse operator can often be determined by only a small, spectrally localized subset of its eigenmodes. In lattice QCD with Wilson fermions, the sign of the fermion determinant is determined by the parity of the number of eigenvalues lying on the negative real axis of the non-Hermitian Wilson-Dirac operator. Determination of this signature can be challenging, particularly in parameter regimes where near-zero modes can lead to exceptional configurations. We present a contour-integral-based spectral projection method to count the negative-real eigenvalues of the non-Hermitian Wilson-Dirac operator $D$ that determine the sign of its determinant. The spectral projection is supplemented by an adapted deflation-accelerated solver for shifted linear systems and singular-value exclusions to reliably set spectral bounds and contour boundaries. We demonstrate the robustness of the method through systematic convergence tests, including variations of the contour size, and show its ability to resolve eigenvalues close to the negative real axis. Beyond fermion determinant sign evaluation, the approach provides a systematic means of isolating physically relevant eigenvalues embedded in dense complex spectra, with potential applications to non-Hermitian quantum systems, stability analyses, and large-scale eigenvalue problems.

We construct a holographic open quantum system by coupling two CFTs through a double trace deformation and tracing out the bath degrees of freedom within the Schwinger-Keldysh formalism. This procedure yields an effective description of the nonunitary reduced dynamics of the remaining sector, whose linear response is encoded in its retarded Green's function. Working perturbatively in the double trace coupling, we derive closed form expressions for the quasinormal modes of several coupled geometries involving pure AdS and rotating or nonrotating BTZ black holes, considering both possible system/bath assignments. For the nonrotating configurations previously investigated in arXiv:2509.14312, our analytic expressions agree with the numerical results, while our treatment extends the analysis to configurations involving rotating BTZ black holes. Finally, moving beyond perturbation theory, we derive a relation between dissipation and transmission in the general AdS-BTZ setup.

The hunt for a material realization of quantum spin ice has motivated more than two decades of experimental effort. The candidate materials inevitably contain crystal imperfections, such as magnetic vacancies, whose effects are often disregarded. Here, we show that experimentally relevant levels of dilution can qualitatively reshape the low-energy behavior, as nearby vacancies generate quantum fluctuations that are absent in the clean system. Already at dilution levels as low as two percent, well below those reported in cerium-based pyrochlores, these vacancy-induced processes connect percolating clusters of spins and dominate over the conventional quantum-spin-ice dynamics. We therefore argue that magnetic vacancies in current experiments can strongly contaminate, and potentially completely obscure, the sought-after signatures of quantum spin ice. We support these conclusions using large-scale, unbiased quantum Monte Carlo simulations and exact diagonalization.

The Riemannian geometry of optical transition dipoles has become a useful picture for understanding linear and nonlinear optical response. Here we argue that the interacting quantum geometry of optical transitions possesses a rich structure and can be naturally delineated into two types: localized and delocalized particle-hole excitations. The former possess uniform quantum geometry with flat (vanishing) Hermitian curvature; the latter possess non-uniform quantum geometry with non-vanishing Hermitian curvature. As a striking example, we find that uniform quantum geometry can be produced by electron-hole interactions: even when composed from extended Bloch states in the particle and hole bands, we find excitons have uniform and flat quantum geometry. By developing a many-body length gauge formulation of nonlinear response, we find this uniform and flat excitonic quantum geometry zeros its third-order circular photoconductivity in non-magnetic materials in stark contrast to its non-interacting counterparts. Similarly, the zero Hermitian curvature of localized optical transitions locks their Hall response to that of the ground state. This demonstrates the rich landscape of many-body optical response controlled by an interacting quantum geometry.

We study the conservative and dissipative forces on a Newtonian binary interacting with a nonrelativistic ultralight scalar medium. We derive integral expressions for the instantaneous force and the orbit-averaged energy flux generated by wake perturbations of a general background field. For a homogeneous coherent background, the conservative force suffers from a well-known infrared divergence. We trace this divergence to the failure of perturbation theory about a constant scalar state and identify the gravitational Bohr scale at which the homogeneous approximation breaks down. In the long-wavelength regime, the leading dissipation into the medium is quadrupolar, and we obtain an explicit expression for the leading energy flux from an eccentric binary. In the short-wavelength regime, we identify a local ”hard” region in momentum space that produces a universal Coulomb logarithm, while the nonlogarithmic contribution remains orbit dependent. We then promote the background to a stochastic ensemble with a general velocity distribution. Three independent length scales, together with a derived geometric-mean scale, produce eight distinct scale hierarchies, for which we characterize the ensemble-mean response. Finally, we derive the two-point correlation function of the orbit-averaged energy flux and evaluate it in ”coherent-response” regimes. Wave interference produces order-unity density fluctuations, so the flux in an individual realization can differ substantially from its ensemble mean.

We assess the potential for the NASA Explorer SPHEREx mission in adding to the Milky Way census of Wolf-Rayet (WR) stars by extracting 0.75–5micron spectrophotometry of 30 candidate WR stars previously identified using Gaia XP spectra. We confirm an additional Galactic 13 WR (8 WN and 5 WC) stars, identify 3 probable [WC]-type central stars of Planetary Nebulae, plus 2 He emission line sources. SPHEREx has the potential to detect additional relatively isolated WR stars on the far size of the Milky Way by combining Machine Learning techniques with a judicious choice of candidate selection criteria. Indeed SPHEREx is sufficiently sensitive to identify bright Magellanic Cloud Wolf-Rayet stars.

In this paper, we study color kinematics duality and related double-copy and BCJ structures in the cosmological Grassmannian framework. The simplicity of these correlators in this framework makes it possible to test the double copy construction beyond flat space. We show that the four-point gluon correlator admits a representation whose kinematic numerators satisfy an algebraically exact Jacobi identity, $n_s$ + $n_t$ + $n_u$ = 0. Replacing color factors with kinematic numerators gives a graviton correlator that reproduces the correct factorization residues and flat-space limit, which matches with the BCFW result up to terms regular in all exchange channels. In addition, we construct a differential bi-adjoint scalar matrix whose null vector gives rise to a differential BCJ relation among color-ordered gluon correlators. We further explore an s-copy construction for general integer-spin correlators and show that for odd spin the corresponding numerators satisfy a Jacobi identity. Finally, we develop a differential representation for scalar four-point correlators with gluon exchange. These results establish algebraic and differential aspects of graviton and gluon correlators in curved spacetime.

The cancellation of renormalon ambiguities in the operator product expansion is usually formulated as a matching between perturbative Borel ambiguities and prescription dependence in non-perturbative condensates. We give this cancellation a contour realization in the two-dimensional Gross–Neveu model at large $N$. The exact order-$1/N$ fermion self-energy in the massive vacuum is a finite real integral; ambiguities arise only after its large-momentum behavior is decomposed into products of perturbative Wilson coefficients and the matrix elements of the associated operators. A reduced integral isolates the leading renormalon and reveals a two-dimensional contour geometry in which the perturbative series is generated at the boundary corner where the exchanged momentum reaches the external hard scale, while its Stokes discontinuity is controlled by a distinct boundary critical point at zero exchanged momentum. After renormalizing the ultraviolet divergences of the condensate scale integral, we derive its compensating lateral ambiguity without fixing it by matching to the perturbative sector, distinguish the renormalon saddle from the apparent IR Landau pole, and obtain the reduced contour variables from the large-$N$ auxiliary-field path integral. The renormalon saddle is a boundary critical point of this reduced mode-space integral. The perturbative Wilson coefficient and the renormalized condensate thus define complementary relative cycles of the same reduced integrand whose complex tails cancel, reconstructing the original real integration cycle.

When spatial sections of spacetime are topologically nontrivial, the symmetry arguments usually used to choose the Bunch-Davies vacuum are no longer guaranteed to apply. We study this problem for a scalar field on de Sitter spacetime with toroidal spatial sections. The Hadamard conditions, which ensure the same short-distance structure as in flat space, are local and naturally insensitive to the compactification. By contrast, we find that the infrared sector is affected by the toroidal identifications that break global de Sitter invariance, thereby removing the usual argument for discarding zero-mode contributions. We treat the remaining zero-mode freedom as an effective topology-induced source and analyze its effects on an inflationary de Sitter expansion within a semiclassical setting. We show that, for a massless scalar, the zero-mode sector can contain a contribution to the stress-energy tensor with equation of state $P=-\rho$, behaving as a cosmological constant. Thus, the source driving an early-Universe de Sitter phase need not be determined solely by local terms in the action, but can also depend on the infrared structure of the quantum state. Nontrivial topology, as a concrete realization of de Sitter symmetry violation, turns the otherwise-unfixed infrared freedom in vacuum selection to a contribution directly relevant to the semiclassical expansion. This contribution could potentially be applicable to the current accelerated expansion of the Universe.

Pair-density-wave (PDW) superconductors admit half-quantum vortices that can bind Majorana zero modes, but whether such defects are energetically stabilized in microscopic models remains unclear. We address this question in a spinless honeycomb-lattice model with a PDW phase. Microscopic Hartree-Fock calculations determine the superfluid stiffness $\rho$ and PDW relative-phase stiffness $\kappa$, and show that $\kappa/\rho$ approaches unity near the continuous PDW–Dirac-semimetal transition, strongly reducing the long-wavelength cost of vortex fractionalization. Combining this with microscopically extracted Ginzburg–Landau couplings, we show that vortex-core energetics favor fractionalization, producing a strongly enhanced splitting scale and a field-driven full-vortex–to–half-vortex lattice transition. We determine the resulting two-flavor half-vortex lattice structure and construct the associated Majorana lattice. Majorana hybridization produces geometry- and flux-dependent bands with Dirac nodes and zero-energy Fermi lines. Together, these results establish a microscopic route from PDW superconductivity to field-induced half-vortex and Majorana lattices.

We prove that the regularized, stabilized sandwiched Rényi divergence of finite-dimensional quantum channels converges to their regularized relative entropy as the Rényi order tends to one. The key tool is the channel hockey-stick divergence: Gour's Stinespring approximation bound and a Schatten norm estimate amplify an asymptotic bound below one into exponential decay at higher threshold rates. For channel pairs with finite max-relative entropy, known operational connections then give exponential strong converses for parallel and adaptive discrimination, a sharp zero–one testing law, and the subchannel asymptotic equipartition property.

We study non-stabilizerness (magic) in the ground state of $(2+1)$-dimensional $\mathrm{SU}(2)$ Hamiltonian lattice gauge theory with matter, formulated in the dressed-site basis in the hardcore-gluon truncation and restricted to the zero baryon-number sector. Using matrix product states, we compute three facets of magic: the second-order stabilizer Rényi entropy (SRE) $M_2$, its non-local component $M_2^{\rm NL}$, and a lower bound in terms of the anti-flatness $F$ of the entanglement spectrum. We also prove a stronger form of the sandwich relation: $-\log_2(1-4F)\le M_2^{\rm NL}\le M_2$; the lower bound rests on a stronger inequality that we obtain for arbitrary Schmidt bases and rank, thus resolving the open problem of finding the maximal lower bound. We emphasize a structural distinction that makes the non-local quantities the physically preferred diagnostics: whereas the full SRE depends on the (non-unique) encoding of the gauge-invariant local Hilbert space into qubits, both the non-local magic and the anti-flatness are invariant under site-local re-encodings and are therefore intrinsic to the state and bipartition. By varying the gauge coupling on lattices up to $6\times 6$ with bond dimension up to $128$, we find that the non-local magic furnishes a sharper and more bond-dimension-friendly probe of the gauge-matter delocalization crossover compared to the full SRE or the gauge-invariant entanglement entropy, retaining a clear signal at bond dimensions well below those needed to converge the ground state itself.