Papers

The Ly$\alpha$ forest is a powerful probe of the intergalactic medium and small-scale matter distribution, but deriving absorber properties traditionally requires computationally expensive Voigt-profile fitting. We present a convolutional neural network (CNN) that identifies and characterizes H I Ly$\alpha$ absorbers directly from quasar spectra. The model is trained on synthetic spectra generated from the IllustrisTNG simulation and fitted with the VIPER Voigt-profile fitting code to provide training labels. The network simultaneously predicts absorber presence, column density ($N_{\rm HI}$), Doppler parameter ($b_{\rm HI}$), and line centroid. On simulated spectra, the CNN achieves an F1 score of $\sim$0.8, with mean absolute errors of $\sim$0.18 in $\log N_{\rm HI}$ and $\sim$0.10 in $\log b_{\rm HI}$. It accurately reproduces the H I column density distribution function (CDDF) and the $b_{\rm HI}$–$N_{\rm HI}$ relation, recovering CDDF slopes consistent with VIPER and a lower-envelope relation with an RMS difference of only 0.36 km s$^{-1}$. Applied to high-resolution UVES spectra, performance decreases to an F1 score of $\sim$0.5, with mean absolute errors of $\sim$0.34 in $\log N_{\rm HI}$ and $\sim$0.21 in $\log b_{\rm HI}$. Latent-space analysis reveals a significant domain shift between the simulated and observational spectra, contributing to the reduced performance. Nevertheless, the CNN preserves the observed CDDF and $b_{\rm HI}$–$N_{\rm HI}$ distributions, yielding CDDF slopes consistent with VIPER and a lower-envelope RMS difference of 2.96 km s$^{-1}$. Monte Carlo dropout is implemented during inference to quantify predictive uncertainties. Together with its computational efficiency, the method provides a scalable and uncertainty-aware framework for Ly$\alpha$ forest analysis in upcoming spectroscopic surveys.

Quantum information theory is built on entropic quantities; among them, the sandwiched Rényi relative entropy is a fundamental divergence with various applications, and its data processing inequality (DPI) under quantum channels is a cornerstone result. In this work, we present a Lean 4 library for quantum information, designed as a reusable formal infrastructure for theoretical analysis. As a central demonstration of the library, we formalize the DPI for the sandwiched Rényi relative entropy for positive semidefinite operators on finite-dimensional quantum systems. The library provides a basis-independent operator-theoretic framework for finite-dimensional quantum mechanics compatible with the standard mathematical library Mathlib, including reusable interfaces for finite-dimensional systems, states, channels, tensor products, partial traces, Choi operators, Kraus representations, and Stinespring representations. It also builds infrastructure for noncommutative trace inequalities, including operator monotonicity and convexity via the real continuous functional calculus, block-operator positivity, Hilbert-Schmidt operator spaces, Jensen's operator inequality, generalized perspectives, operator power means, and Lieb-Ando trace inequalities. On top of this framework, we formalize entropy-specific ingredients for the DPI: variational formulas for the sandwiched quasi-entropy via Young and reverse-Young inequalities, tensor-product compatibility of real powers, and Haar measures on unitary groups. Together, these components yield a Lean formalization of the DPI, give strong subadditivity as a corollary, and provide the last missing component needed to complete the Lean formalization of the generalized quantum Stein's lemma. More broadly, the development provides machine-checkable foundations for future formalized and AI-assisted research in quantum information theory.

We develop a perturbative Green's function approach to gravitational lensing by weak gravitational potentials that need not be localized on a thin lens plane and that applies in both the wave optics and geometric optics regimes. We recast position-space integrals as Fourier, or momentum-space, integrals that appear in scattering amplitude calculations. The method gives the Born approximation directly in three dimensions and can be systematically extended to post-Born orders. For a Schwarzschild lens, we compute the leading Born term and new post-Born contributions arising from the order $\mathcal{O}(G^2)$ correction to the potential, keeping finite-distance corrections beyond the usual paraxial expansion. We show that these general-relativistic corrections are controlled by the parameter $GM\omega\,b/\chi_{\rm eff}$ in the small-angle regime, and are therefore negligible for standard weak-lensing configurations but become relevant in more extreme geometries (such as hierarchical triples with very small source–lens separations). We also discuss higher-order Newtonian corrections, their infrared sensitivity for a long-range potential, and the regulated form of the Newtonian potential given by the Yukawa potential. Finally, we formulate the corresponding calculation in an FLRW background, identifying the leading flat-space limit and estimating the size of curvature-induced corrections including tails. This method clarifies the regime of validity of the Born, large-distance, and paraxial approximations in gravitational-wave lensing and provides a framework for treating generic lensing potentials.

We provide a new formal extension of the BFSS matrix model by an additional 5-bracket. Maximal supersymmetry leads us to promote the BFSS 2-bracket structure constants to a dynamical field $H_{abc}$ governed by a Chern-Simons-like kinetic term. We first show that the full generic pseudo-action is invariant under maximal supersymmetry and that the associated supersymmetry algebra closes upon invoking a number of BPS-like quadratic constraints. We then present a special case based on the 5-Lie algebra $A_6$ that evades these additional constraints and allows for a Lagrangian description. These results hinge on a conspiracy of properties of the $SO(9)$ gamma matrices and the 2- and 5-brackets. Compellingly, the resulting model seems to realize some features expected of a theory containing M5-branes and opens up the possibility of further including higher brackets for the M6- and M9-branes.

The AInstein architecture introduced an unsupervised neural method for solving the Riemannian Einstein equations on arbitrary manifolds. This Physics Informed Neural Network approach (PINN) is extended here to Lorentzian signature, validated by recovering the maximally extended Schwarzschild geometry, and tested as novel search method for arbitrary black hole solutions. The topology is built into the architecture by treating $S^{2}$ globally through its standard embedding, such that the network learns an ambient metric on the manifold $\mathbb{R}^{2} \times \mathbb{R}^{3}$, where Penrose coordinates are chosen for $\mathbb{R}^2$ and the metric on $S^{2}$ is obtained by pullback. The architecture is first trained with the objective of recovering the Schwarzschild metric via losses encoding the vacuum Einstein equation, a quadratic Weyl scalar constraint, and the $SO(3)$ symmetry of the resultant metric; directly motivated by the Birkhoff–Jebsen theorem. Following this, the objective is generalised to use the Petrov speciality index, a horizon curvature anchor, and a trapped-surface constraint, to allow search for algebraically general Petrov type I solutions, finding potentially novel general-type Lorentzian Einstein metrics with a genuinely trapped interior.

Large charged black holes can create macroscopic, locally weakly curved regions in which moduli take values different from their asymptotic values. We study how robust this mechanism is once the scalar has a nontrivial potential. In four-dimensional Einstein-Maxwell-dilaton theory, the massless GHS solution provides a finite exterior throat in which the scalar and the gauge coupling vary logarithmically. We develop fixed-throat diagnostics for the competition between the black hole gauge source and a scalar potential, and compare them with back-reacted exterior evolutions when needed. The relevant criterion is not the mere presence of a potential, but how its force behaves along the scalar trajectory traced by the black hole throat. Quadratic stabilizing potentials erase the throat when the Compton wavelength becomes comparable to the horizon scale. Runaway, periodic, and barrier-type potentials instead exhibit distinct failure modes controlled by their slope, sign, oscillations, or barrier distance along the GHS trajectory. A quintessence-like scalar remains effectively massless on astrophysical black hole scales, leaving the throat essentially unobstructed. If the charge belongs to a hidden sector, and if the scalar also controls visible couplings or bulk propagation, such surviving altered-modulus regions could leave phenomenological imprints in near-horizon accretion or emission.

Due to the exponential growth in the number of terms, computing $\alpha'$-corrections to string theory's low-energy effective actions is a challenging matter. In order to fix all the couplings, one has usually to deal with a large number of string scattering amplitudes. This difficulty can be overcome by exploiting T-duality, which severely constrains the allowed structure of the effective action. It is then convenient to work in a formulation where T-duality is a manifest symmetry. Building on a series of previous works by some of the authors, we present a refined version of an elegant and effective procedure that allows to obtain all the higher-derivative corrections of the NS-NS sector of sting theories at order $\alpha'$ and $\alpha'^2$, up to an overall coefficient. We dub this approach $\alpha'$-bootstrap, since it is based only on consistency conditions and avoids the direct computation of scattering amplitudes. The procedure relies on an infinite dimensional algebraic structure that we present in full detail, and it is conjectured to work at all orders. Although, at the moment, it still misses the $\zeta$-like corrections starting at order $\alpha'^3$, the ease with which it can be generalized is promising for future developments in this direction.

We investigate biases in parameter estimation for damped oscillations motivated by applications to black-hole spectroscopy in gravitational-wave physics. Focusing on the simplest model of a single-mode damped sinusoid with a fixed start time in white noise, we show that, at finite signal-to-noise ratio \rho, the damping time is biased toward larger values without being suppressed by the quality factor for two reasons. One is the gradient of the prior, through which the damping time is affected by the typically decreasing prior on the amplitude. The other is a higher-order finite-\rho correction to the likelihood geometry. These biases arise even if the model and analysis are appropriate. Moreover, they could be exaggerated in naive joint inferences from catalog events. Quantitatively, if estimates from multiple events with \rho=10 are combined without due care, the catalog-level black-hole spectroscopy could report false violation of the Kerr hypothesis with >~100 events. We also propose simple strategies to mitigate these biases at the level of individual events.

In this paper we will examine if nonlocal quantum field theory will suffer from the fermion doubling pathology. We find that for a nonlocal Dirac theory, that no additional fermion species are introduced. This is provided that the form factor is nonvanishing at every point. The proof follows from the invertibility of the entire-function operator, which implies that the nonlocal Dirac operator has exactly the same kernel and finite-momentum zero set as the original local Dirac operator. We will distinguish this result from the standard Nielsen-Ninomiya theorem, which applies local lattice fermions on a compact Brillouin zone. We provide a general criterion for fermion doubling, a test for genuine and false doubling, and then a test procedure for mathematical and physical fermion doubling. We then will go on to distinguish this result from finite derivative truncations, which can introduce spurious polynomial zeros. We then conclude that fermion doubling is absent in the full continuum nonlocal theory.

Photometric observations of space debris objects brighter than magnitudes 6.0, 7.0 and 8.0 are characterized. Those magnitudes pertain to different levels of interference with astronomy as defined by the International Astronomical Union. The densities of debris objects per square degree of sky and brighter than the magnitudes listed above are only 6, 13 and 24 parts per million, respectively. Furthermore, only about 1.4%, 2.5% and 3.8% of the 12,173 debris objects cataloged by NORAD exceed those magnitudes for even a small fraction of the time. So, debris trails have a minor impact on astronomical images and visual sightings are few. Characteristics of debris resulting from selected spacecraft collisions and rocket explosions are also quantified. This study is based on 13 million observations recorded by the MMT9 observatory.

Within the tight binding framework of graphenes {\pi} electron nearest neighbors, the Tan Bo model parametrizes transition energies t(dr) based on bond lengths and angles via the Mobius transformation combined with exponential decay. Comparisons between isotropic , geometrically anisotropic , and Slater Koster scales reveal that B = 0 is equivalent to the SK scheme, with L(B) reaching its optimum at Bopt = 0. The Hermitian assembly maintains the Dirac cone at the K point.The Tan Bo geometry dependent transition model and non Hermitian TB assembly scheme developed in this study provide a reproducible single particle benchmark and parameterization reference for future non Hermitian chemical calculations incorporating electron correlation effects in graphene systems.

We present a geometric derivation of Liénard–Wiechert fields in flat-space and AdS, emphasizing the origin of antipodal matching. In flat-space, the field of a uniformly moving charge is rewritten in coordinates centered on the source timelike geodesic. In this frame the charge is at rest and the solution is Coulombic, so the matching of the leading data at null infinity arises from describing a static field in a non-centered frame. We extend this construction to global AdS, where uniform motion is replaced by motion along a timelike geodesic. Starting from the static Coulomb solution at the center, we reconstruct the field of a freely moving charge in arbitrary global coordinates using embedding-space invariants. The resulting closed-form field obeys exact antipodal covariance in the bulk, and its boundary null-fringe limit reproduces the usual flat-space antipodal matching relation. We also describe an image-charge interpretation: the flat-space Coulomb field is represented after conformal compactification by an image singularity at spatial infinity, while the AdS Coulomb seed may be viewed as a charge together with an opposite image charge in a reflected copy. Together, these perspectives give a unified picture of Coulombic Liénard–Wiechert fields, antipodal matching, and the AdS-to-flat-space limit.

Time-domain surveys generate many transient candidates, making Real-Bogus classification a critical step in automated discovery pipelines. Reliable labels are costly, while community labels can be noisy and survey-dependent. We aim to develop a Real-Bogus classification framework that can be trained without human-labeled data using injected transients and bogus-dominated survey data, remains robust under strong class contamination, and provides calibrated uncertainty quantification. We combine simulated transient injections with a contaminated survey class and train a dual-network model using asymmetric co-teaching for classes with different label-noise levels. We evaluate performance on a benchmark subset and analyze the learned representation with latent-space visualization tools. For uncertainty quantification (UQ), we compare MC dropout and deep ensembles and propose a low-cost hybrid strategy that exploits the dual-network setting to improve calibration. We extend the evaluation to the light-curve domain to assess recovery of light-curve classes. The method achieves strong Real-Bogus performance on the labeled subset and remains stable under severe class contamination. It recovers transient light-curve classes with high fidelity, while single-source identification is limited by ambiguity in light-curve-derived labels. Our hybrid UQ approach achieves competitive calibration relative to more expensive ensemble baselines. Latent-space analyses indicate that uncertainty aligns with the decision boundary and reveal subclasses within the bogus population. Our results show that injection-driven, weakly supervised training can enable scalable and consistent Real-Bogus classification without human-labeled training data while providing calibrated uncertainties. The method is suited for transfer to forthcoming surveys by re-running the injection-based training pipeline.

Quantum LDPC memories can encode many logical qubits, but that alone does not make them usable: applications need to know where the logical operators are supported, how they are labeled, and how conjugate $X/Z$ partners pair. For hypergraph-product codes this information follows from row reduction over $\mathbb{F}_2$. For Abelian lifted-product codes, which include prominent high-rate constructions, it does not: the entries of the defining seed matrices live in a group algebra rather than a field, so pivots need not be invertible and row reduction can fail. To address this problem, we introduce logical spectroscopy. For an odd-order Abelian lift group, the Chinese remainder theorem splits the group algebra into finite fields, one for each Frobenius orbit of characters; we call these orbits packets. Packet by packet, we solve ordinary finite-field linear algebra, lift the answers back to the physical code with the associated packet projectors, and pair $X$ and $Z$ logicals between reciprocal packets by trace duality. The result is a complete conjugate logical basis for a finite Abelian lifted product code that is addressable: every logical coordinate carries canonical packet and Künneth-summand labels, deterministic within-block indices, a conjugate partner, and an explicit binary representative. The code's own translation symmetry then acts on these coordinates in closed form. We apply the construction to examples with up to 5000 physical qubits, including high-rate examples whose distance-witness is reported explicitly. We further extend the decomposition to even-order lifts. Logical spectroscopy thus equips Abelian lifted products with an explicit logical coordinate system and an algebraic toolkit for high-rate code search.

I construct the Type-IIB axion–dilaton wormhole partition function from charge-sector data. In a chosen axion charge, equivalently form-field flux sector, the long-distance saddle calculation supplies a two-end operator term with coefficient matrix \(C^{ij}_\nu\). The labels \(i,j\) label end-insertion operators; the labels \(A,B\) label parent universes. Reduction data \(b\) convert this matrix into scalar coefficients \(W_\nu[b]\). The wormhole partition function in the theta variable is \(Z_{\rm wh}(\theta;b)=\sum_\nu W_\nu[b]\e^{i\nu\theta}\). I analyze properties and constraints this coefficients satisfy: discrete-symmetry covariance, phase, absolute bounds, moment positivity, Cauchy–Schwarz inequalities for the unreduced coefficient matrix, complex-\(\theta\) domains, charge-lattice tails, and the dilute Bessel/Skellam limit. The \(\theta\)-dependence of the wormhole partition function is the Fourier transform of the charge-sector scalar coefficients.

We develop a Hartree-Fock numerical method for computing the band structure of a two-dimensional Wigner crystal in an electron gas at zero temperature. The ground state is assumed to be fully spin-polarized. Single-particle excitation spectra are evaluated in spin-conserving channel. As an application, we use the developed code to compute the static dielectric function epsilon(q,0) of a Wigner-crystal state formed in a two-dimensional transition-metal dichalcogenide, specifically monolayer WSe2. The dielectric response is obtained from the Hartree-Fock band structure and eigenfunctions through a static Lindhard-type polarizability. The method provides a theoretical tool for investigating screening, band-structure reconstruction, and interaction effects in low-density two-dimensional systems, with possible relevance for future experimental studies.

Quantum photonic technologies greatly benefit from quantum light emitters with high brightness, indistinguishability, and reliable polarization characteristics. Achieving optimal performance relies on the accurate localization of emitters and their deterministic integration into tailored photonic structures with nanometer-scale accuracy. Although marker-based photoluminescence imaging techniques can achieve statistical fitting uncertainties below 10 nm, the ultimate integration yield is often limited by uncorrected systematic distortions in custom cryo-optical setups that compromise metrological accuracy. Here, we present an in situ calibration protocol that uses lithographically defined gold nanodisk arrays as references to calibrate optical distortions with a Zernike vector-field model. On held-out validation patterns beyond the calibration dataset, this correction reduces the residual systematic bias to 5.3 nm with a 2D scatter of 24.6 nm across the analyzed field of view. Furthermore, we demonstrate that applying this correction to the deterministic fabrication of circular mesa structures around semiconductor quantum dots reduces the variance in emission polarization by 49%, indicating improved registration accuracy. This calibration strategy offers a practical route to high-yield deterministic integration of quantum emitters into scalable quantum photonic circuits.

The LISA-Taiji dual detector network improves millihertz SGWB sensitivity through cross correlation measurements. Solar wind plasma, however, can generate plasma noise correlated between detectors and bias SGWB cross correlation estimates. We use high time resolution electron density data from Wind/SWE, estimate the solar wind electron density fluctuation spectrum with the Lomb-Scargle method, and propagate the resulting plasma noise to the TDI A/E channels of the LISA-Taiji network. By including finite arm propagation, Taylor frozen flow spatial correlations, and the network overlap reduction response, we compute the SGWB parameter bias induced by interdetector plasma noise. Although the single detector plasma residual is below the reference noise, the component correlated between detectors can enter the SGWB cross correlation estimator directly. Under dual detector scale coverage, the plasma induced parameter bias for a power law SGWB can reach $12.73\%$ of the corresponding Fisher parameter uncertainty. For M2/M3 cosmic string spectra, the bias in $\ln G\mu$ can reach $19.26\%$ of the corresponding Fisher parameter uncertainty for the network configurations, observing times, and frequency bands considered here. These results show that the impact of solar wind plasma noise cannot be assessed from the single detector residual noise level alone. In LISA-Taiji SGWB searches, the interdetector correlated component of this noise can directly affect parameter estimation.

In this paper, we investigate a possible time variation of the gravitational constant (G) using a non-parametric approach. Our main cosmological probe is the gas mass fraction of galaxy clusters measured from X-ray observations. We also account for the effect of a varying $G$ on the intrinsic luminosity of type Ia supernovae (SNe Ia) through the Chandrasekhar mass-luminosity relation. We consider a specific phenomenological scenario, motivated by some scalar-tensor and screened modified-gravity frameworks, in which the standardized luminosity of SNe Ia decreases with increasing Chandrasekhar mass. Using gas mass fraction measurements jointly with luminosity distances from the Pantheon+ compilation, we reconstruct the evolution of G through Gaussian Processes. Our results indicate that a constant gravitational coupling remains broadly consistent with the data, although mild low-redshift departures are allowed.

Coherent control of energy transport in a non-equilibrium steady-state (NESS) in a reaction-center-connected donor-acceptor pair is proposed. The pigments are considered to be continuously interacting with incoherent radiation and a phonon bath while being driven by phase-controlled coherent fields. Coherent excitation of the donor-acceptor pair is shown to induce interference between excitation pathways, resulting in phase dependent modulation of the flux. As a consequence one can enhance or suppress energy transfer via interference, e.g. an optical energy switch. The persistence of such interference enables coherent control at a NESS in dissipative regime suggests an extension of the operational scope of quantum control from traditional transient domain with low dissiaption to noisy environment NESS at room temperature.

Supernova cosmology relies on accurate measurement of the absolute magnitudes of Type Ia supernovae. Observation in the visible incurs significant systematic uncertainties in these measurements due to their high degree of interstellar dust extinction. Observing in the near-infrared (750-2500 nm) mitigates this issue by decreasing attenuation, decreasing dispersion, and increasing supernova observation distances. However, ground-based observations in the near-infrared suffer from sky background caused by atmospheric OH emission lines. Advancements in photonic ring resonator filter devices make it feasible to suppress these lines. In this paper, we evaluate the performance of a prototype photonic ring resonator device developed for use in the lower H-band (1480-1620 nm). Specifically, we characterize the progression of suppressed wavelengths into the upper H-band (1620-1800 nm) enabling the suppression of emission lines over a broader wavelength range.

Characterizing a quantum state through the lens of quantum resources provides an information-theoretic perspective on many-body systems. While quantum entanglement serves as the paradigmatic example of a quantum resource, recent studies have shown that quantum magic, a resource for universal quantum computation, captures aspects of many-body states complementary to those described by entanglement. For instance, in spin systems, conformal field theory (CFT) analysis of the stabilizer Rényi entropy has revealed universal features of nonstabilizerness qualitatively distinct from entanglement. In bosonic and fermionic systems, however, a comparable formulation for their computational resource, non-Gaussianity, has yet to be established. In this work, we introduce a unified measure, the magic Rényi entropy (MRE), to quantify computational resources in spins, bosons, and fermions on an equal footing. We show that the MRE is a resource monotone under stabilizer and Gaussian protocols involving measurements and feedforward operations. The MRE reveals common universal aspects of nonstabilizerness and non-Gaussianity in critical many-body states. In particular, our CFT analysis shows that the universal contribution to the MRE appears as the size-independent term determined by the Affleck-Ludwig boundary entropy. We find that non-Gaussianity can continuously renormalize this universal contribution or drive a boundary transition through bulk-induced boundary renormalization-group flows. As a concrete example, we present a CFT analysis of non-Gaussianity in interacting spinless fermions described by the Tomonaga-Luttinger liquid, showing boundary transitions at the Luttinger parameters $K=1/3$ and $K=3$. Our field-theoretical predictions are confirmed by numerical calculations. These results provide a unified field-theoretical understanding of many-body magic across spins, bosons, and fermions.

We revisit the old problem of analytically continuing QFTs to fractional dimension $d\in\mathbb C$. We observe that common theories like QCD and QED have branch cuts in the complex $d$ plane. In particular, many operators in their low-energy CFT have OPEs and scaling dimensions that jump as a function of $d$.

We investigated the magnetotransport properties of single-crystals of tetragonal van der Waals compound EuNi$_2$As$_2$, that orders antiferromagnetically below 14.6 K in an incommensurate helical structure. Metamagnetic transitions are revealed by the magnetization measured in the magnetic field applied transverse to the axis of the helix, and are clearly reflected in the magnetoresistance. Overall, the magnetoresistance is small, but shows complex changes with the temperature, the strength, and the angle of the applied magnetic field. In magnetically ordered state, magnetoresistance shows prominent anomalies related to the metamagnetic transitions. For temperatures above the Néel point the negative magnetoresistance can be modeled very well with de Gennes-Friedel mechanism of the spin-disorder-scattering reduction. Hall resistivity data indicate hole-dominated multi-band conductivity in antiferromagnetic state and single-band one above the Néel temperature, with carrier concentrations of the order of 10$^{22}$cm$^{-3}$. This metallic character of the compound seems to obscure the plausible topological contribution to the Hall resistivity. Our ab-initio calculations of electronic band structure showed that the electronic structure changes very strongly upon magnetic ordering, but the density of states at the Fermi level differs by a factor smaller than two, in agreement with experimental Hall resistivity data. Meaningful changes in the density of states, magnetic moments, and screening length of Eu-4$f$ orbitals are discussed in terms of the effects of Hubbard corrections.

The IceCube and ANTARES collaborations have recently reported evidence for high-energy neutrinos associated with the Galactic plane and the Galactic Ridge, offering a new pathway to search for dark matter (DM). Deep inelastic scattering of cosmic rays with sub-GeV DM in the Galactic halo produces a distinctive neutrino signature from meson decays. Using detailed Galactic cosmic-ray maps and ANTARES observations, we derive 99% C.L. upper limits on the DM-nucleon cross section that extend down to keV-scale masses. These results establish Galactic neutrino telescopes as a powerful, complementary probe of light DM, with substantial improvements expected from upcoming IceCube-Gen2 and KM3NeT observations.

In this study, within the framework of f(R,T) modified gravity, we investigate the influence of coupling parameter, magnetic field and anisotropy parameter on the neutron star structure. This work employs an accurate equation of state (EoS), derived from realistic microscopic calculations based on the AV18 nucleon-nucleon potential, to compute the structure of this compact object. Here, determination of Schwarzschild radius, compactness, gravitational surface redshift and Kretschmann scalar within the f(R, T) gravity, confirms that our theoretical results are consistent with the observational constraints. While established physical EoSs within the framework of Einstein gravity have successfully characterized a broad range of compact objects, they remain inadequate in explaining certain massive objects residing within the mass gap (2.5 to 5 Msun). We show that some compact objects residing in the mass gap interpreted as candidates of neutron stars within the framework of f(R, T) gravity. Finally, we compare our results with the observational data from LIGO/Virgo/KAGRA and NICER, setting the parameters of the f(R, T) theory and anisotropy to successfully reproduce the masses and radii of the GW170817, PSR J0952-0607 and PSR J0740+6620 and the masses of the secondary components of GW190814 and GW200210-092254.

We investigate the impact of modified gravity on the stochastic gravitational-wave background (SGWB) generated by a cosmological population of unresolved binary black hole mergers. We consider two complementary classes of beyond-General Relativity (GR) effects: waveform-generation modifications described within the parametrized post-Einsteinian (ppE) framework and cosmological propagation effects associated with a modified gravitational-wave luminosity distance. Astrophysical uncertainties in the binary black hole population are consistently incorporated using a Power-Law plus Peak mass model combined with a Madau–Dickinson merger-rate evolution. Using SGWB forecasts for Advanced LIGO, the Einstein Telescope (ET), and Cosmic Explorer (CE), we perform injection-recovery analyses jointly varying modified-gravity and astrophysical population parameters. We show that frequency-dependent ppE corrections produce characteristic distortions in the SGWB spectral shape and can be meaningfully constrained by third-generation detectors, particularly CE. In contrast, modified propagation effects mainly induce smooth amplitude rescalings and exhibit stronger degeneracies with astrophysical uncertainties. Our results demonstrate that future SGWB observations will provide a complementary probe of gravitational physics across cosmic history and may open new avenues for testing deviations from GR beyond individually resolved compact-binary events.

We report a fully analytical description of zero-temperature itinerant ferromagnetism in repulsive SU(N) Fermi gases with arbitrary mass imbalance among components. Using perturbation theory in the gas parameter x = kFa0, with kF the Fermi momentum and a0 the s-wave scattering length, we derive the second-order energy for arbitrary spin polarization and arbitrary mass ratio. Our main result is a closed analytic expression for the beyond-mean-field correction in mixtures with unequal masses. This analytical result extends the theory of dilute Fermi gases beyond the mass-balanced case and provides a compact equation of state for multicomponent mixtures. We show that mass imbalance breaks the paramagnetic symmetry already in the non-interacting limit, favors the occu pation of heavier components, and lowers the interaction strength required to reach a fully polarized state. For S = 1/2, the system evolves continuously from a mass-induced partially polarized state to full ferromagnetism. For larger spins, distinct mass distributions generate qualitatively differ ent polarization paths, including smooth and discontinuous sequences. Our results identify mass imbalance as a powerful control tool for magnetic ordering in ultracold Fermi mixtures.

In this work, we present the procedure to find series representations of tree-level cosmological correlators using the Kontorovich-Lebedev-Fourier (KLF) space formalism. This framework allows us to trade the in-in nested time integrals for frequency integrals over rational propagators and vertex functions, which encode interactions among quantum fields on a de Sitter background. Because these functions are the key objects to understand in order to perform a diagrammatic computation, we derive their relevant analytic properties by using both their integral representation and series representation in terms of Lauricella functions. For a vertex involving any number of fields, we obtain the location of singularities, the corresponding residues and the large-frequency asymptotic behaviour. Gathering these properties at each frequency integration allows us to compute a tree-level correlator directly, without relying on the differential equations it satisfies. To illustrate this procedure, we provide a complete treatment of the double-exchange diagram. The computation naturally distinguishes the different physical contributions, whether to the background or to the cosmological collider signal. The newly derived result is expressed at most in terms of a double series over hypergeometric functions, which simplifies the analytical expression of the correlator.

The cosmic star formation rate density (CSFRD) has declined sharply toward the present day, but the roles of the atomic and molecular gas reservoirs remain uncertain. We measure the cosmic HI density, $\Omega_{\mathrm{HI}}$, over $0<z<0.41$ by combining HI spectra from the Five-hundred-meter Aperture Spherical Telescope with optical spectroscopy from the Dark Energy Spectroscopic Instrument for $\sim2.5$ million galaxies across $\sim12,000\,{\rm deg}^2$. We measure a raw decrease in $\Omega_{\mathrm{HI}}$ by a factor of $1.35\pm0.10$ over the past 4.5 Gyr. Even after applying the conservative systematic corrections from our forward model, the inferred decline is only $1.12\pm0.10$ – still far weaker than the CSFRD decline (a factor of 2.46). The molecular gas density, in contrast, is known to evolve more closely with star formation. At fixed stellar mass, the average HI gas fraction evolves by less than 0.2 dex, showing that the weak evolution is present across the galaxy population. These quantitative differences rule out rapid depletion of galaxy HI as the primary driver of the late-time CSFRD decline, and provide a stringent benchmark for models of gas accretion, phase conversion and star-formation regulation.