General Relativity and Quantum Cosmology
A rigid spherical shell enclosing a degenerate wormhole
Juri Dimaschko
A static configuration consisting of a rigid spherical shell enclosing a degenerate Schwarzschild Klinkhamer wormhole is investigated in general relativity. The shell is analyzed using the Israel junction conditions, while the total ADM mass is assumed to remain fixed. For an ordinary rigid shell in Schwarzschild spacetime, the proper mass is given by the Brown York relation. It is shown that replacing the flat interior by a degenerate
vacuum wormhole changes the junction conditions in such a way that the proper mass of the shell vanishes, whereas the ADM mass and the exterior Schwarzschild geometry remain unchanged. The resulting configuration is therefore entirely characterized by the wormhole geometry as the carrier of the gravitational field. The physical interpretation of this result is discussed, together with its relation to the previously established collapse dynamics of degenerate wormholes.
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General Relativity and Quantum Cosmology
Early- and late-time constraints on Wald-Gauss-Bonnet topological dark energy and implications for the $H_0$ and $S_8$ tensions
Stylianos A. Tsilioukas, Fotios K. Anagnostopoulos, Spyros Basilakos et al. (+2 more)
The persistent $H_0$ and $S_8$ tensions motivate the search for new dark-energy mechanisms capable of modifying the late-time expansion history while preserving the successful early-Universe predictions of $\Lambda$CDM scenario. Wald-Gauss-Bonnet (WGB) topological dark energy provides a physically motivated realization of this possibility, where the effective dark-energy sector emerges from
cosmic horizon thermodynamics and the black-hole formation and merger history. We present the first early- and late-Universe analysis of WGB cosmology, implementing the model as an effective fluid in a modified CLASS solver and constraining it against CMB data from Planck, ACT~DR6 and SPT-3G, DESI~DR2 BAO, and Pantheon+
supernovae. While late-time data alone are consistent with $\Lambda$CDM, the full
dataset prefers a non-zero WGB contribution, $\Cn=0.387^{+0.118}_{-0.072}$, corresponding to a $>3\sigma$ phantom-like deviation and an improved fit ($\Delta\chi^2=-10.3$). The preferred solution raises $H_0$ from $68.5$ to $69.8~\kmsmpc$, reducing the Hubble tension by $\sim1\sigma$, at the cost of a mild increase in $S_8$. The reconstructed cosmological observables show that WGB leaves the primary CMB almost unchanged while enhancing
lensing and small-scale clustering, revealing a characteristic $H_0$-$S_8$ trade-off. WGB dark energy therefore emerges as a physically motivated and observationally viable late-time mechanism for partially alleviating the Hubble tension without introducing new early-Universe physics.
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All authors Stylianos A. Tsilioukas, Fotios K. Anagnostopoulos, Spyros Basilakos, Andronikos Paliathanasis, Emmanuel N. Saridakis
Quantum Physics
Exact Conditional Momentum Moments for Nonlinear Homodyne Trajectories
Jacob Emerson
Simulation of nonlinear
stochastic master equations generally requires trajectory-level
evolution of large
Hilbert-space density
matrices, making strongly nonlinear continuously monitored systems computationally challenging. Here we identify an exactly solvable class centered on
polynomial Hamiltonians of commuting quadratures with linear damping and homodyne measurement of those same quadratures. For initial states with a Gaussian measured-quadrature marginal and
polynomial conditional-momentum sections, we derive an exact finite
stochastic representation through any fixed momentum order. The result extends to interacting multimode systems, arbitrary measurement efficiency, and finite thermal occupation. Its computational cost is linear in trajectory length and independent of
Hilbert-space dimension, requiring no Fock-space truncation, Gaussian approximation, or approximate moment closure. As an application, we derive an exact causal filter for monitored cubic-phase gates that uses the homodyne record to determine the variance-minimizing momentum displacement. Numerical simulations validate the representation against direct
stochastic-master-equation
evolution, demonstrate substantial speedups over converged Fock-space propagation, and show that this record-conditioned recentering can efficiently recover nonlinear squeezing otherwise lost through trajectory averaging.
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Astrophysics of Galaxies
The evolution of galaxy dust scaling relations in the COLIBRE simulations
Aswin P. Vijayan, James W. Trayford, Joop Schaye et al. (+11 more)
We present
dust scaling relations across
cosmic time ($0 \le z \le 15$) for
galaxies in the COLIBRE cosmological simulations. COLIBRE self-consistently tracks
dust production, growth, destruction, and grain size
evolution within a multiphase interstellar medium. Using volumes up to $(400\, {\rm cMpc})^3$ at three mass resolutions ($10^{5}-10^7$ M$_{\odot}$), we predict the
dust mass function,
cosmic dust mass density, and key
dust scaling relations (
dust-to-gas ratio,
dust-to-metal ratio, grain species fractions, and grain sizes) as functions of
galaxy metallicity,
stellar mass, and
dust mass. The model broadly reproduces most observed relations across
cosmic time, matching closest at the highest resolution. We find that silicates dominate the
dust mass ($\gtrsim 70\%$) at all epochs, and while large grains dominate in the early Universe ($z \ge 5$), their mass fraction declines to become comparable to small grains by $z=0$. At $z < 1$, the simulated
dust mass functions align well with observations, but the
cosmic dust mass density is systematically high by $\lesssim 0.3$ dex, while in agreement with observations at higher
redshifts. Additionally, the simulations underpredict the extreme
dust masses of bright sub-millimeter
galaxies at $z \ge 2$. We demonstrate that scaling relations are sensitive to numerical resolution only in the low-
redshift, low-mass regime; while their normalisation is influenced by gas-phase selection. These findings highlight both the predictive power and resolution-dependent limits of cosmological
dust models, providing essential insights to refine ISM physics.
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All authors Aswin P. Vijayan, James W. Trayford, Joop Schaye, Sylvia Ploeckinger, Andrea Gebek, Nick Andreadis, Maarten Baes, Alejandro Benítez-Llambay, Evgenii Chaikin, Carlos S. Frenk, Filip Huško, Robert J. McGibbon, Alexander J. Richings, Matthieu Schaller
High Energy Astrophysical Phenomena
QuickGWecc: Fast Bayesian pipeline for searching eccentric binaries in pulsar timing array data
Lankeswar Dey, Bence Bécsy, Abhimanyu Susobhanan et al. (+1 more)
Recent
pulsar timing array (PTA) results have provided evidence for the presence of a nanohertz gravitational wave (GW) background, most likely originating from a population of supermassive black hole binaries (SMBHBs). The next major milestone is the detection of continuous GWs (CGWs) from an individual SMBHB and the identification of its electromagnetic counterpart. Typically, searches for CGWs in PTA data assume binaries in circular orbits. However, theoretical studies indicate that binaries emitting GWs in the PTA frequency band may retain significant eccentricity. In this paper, we present a fast and efficient
Bayesian pipeline to search for CGWs from individual SMBHBs in relativistic eccentric orbits in PTA
datasets. Our approach extends the QuickCW framework for circular binaries, in which model parameters are divided into projection and shape parameters. Computational efficiency is achieved by performing many updates of the projection parameters for a fixed set of shape parameters, an operation that is orders of magnitude faster than updating the shape parameters. We validate the pipeline through both detection and upper-limit analyses of simulated PTA
datasets. This framework makes the search for eccentric SMBHBs computationally feasible, even in the next-generation PTA
datasets with many more
pulsars.
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All authors Lankeswar Dey, Bence Bécsy, Abhimanyu Susobhanan, Maria Charisi
Cosmology and Nongalactic Astrophysics
$\Lambda$XCDM: a running vacuum strategy for crossing the phantom divide
Joan Solà Peracaula, Adrià Gómez-Valent and Alex González-Fuentes
Composite dynamical dark energy (DDE) has recently been explored as an efficient way to help cure cosmological tensions through the so-called $w$XCDM model (Gomez-Valent & Solà Peracaula 2024; 2025), a toy-model version of the $\Lambda$XCDM model (Grande et al., 2006). The latter is a composite running
vacuum model (RVM) that involves a DE component $X$ (`cosmon') of generic nature. We compute the effective equation of state of $\Lambda$XCDM and use state-of-the-art techniques to fit this model to two standard sets of cosmological data, one involving SNIa from Pantheon$+$ and the other SNIa from DES-Dovekie, in addition to BAO data from DESI DR2 and the CMB data from Planck PR4. We do not use large scale structure formation data for this analysis nor the SH0ES calibration of $H_0$. We find that $\Lambda$XCDM naturally performs the crossing of the phantom divide as observed by DESI near $z\simeq 0.4$ using the $w_0w_a$CDM parameterization, a feature well favored by existing model-agnostic analyzes of the same data (González-Fuentes & Gómez-Valent:2025; 2026). It turns out that the cosmon $X$ behaves as `phantom matter' (PM) near the present, which in contrast to usual phantom DE satisfies the strong energy condition (as ordinary matter) and furnishes positive pressure ($P_X>-\rho_X>0$) at the expense of negative energy density ($\rho_X<0$). $\Lambda$XCDM provides a better fit than $w_0w_a$CDM and, as a bonus, alleviates the
cosmic coincidence problem. Given that PM appears in stringy versions of the RVM (Mavromatos & Solà Peracaula 2021 a,b) , the $\Lambda$XCDM appears to be a composite DDE model with a good chance of explaining the crossing of the phantom divide from first principles, therefore providing theoretical support to the DESI observations inferred from generic parameterizations of the DE.
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Cosmology and Nongalactic Astrophysics
Probing Parity Violation with Weak Lensing Trispectrum
Sijin Chen, Zhengyangguang Gong and Jiamin Hou
We establish the weak gravitational
lensing convergence trispectrum as an independent probe of cosmological parity violation in the late-time Large-Scale Structure (LSS). To map three-dimensional
primordial symmetries into two-dimensional observables, we derive a generalized, compact projection formalism for the reduced angular trispectrum applicable to two classes of factorizable
primordial curvature trispectra considered in this work. Applying this framework, we compute the parity-odd signal and forecast the expected Signal-to-Noise Ratio (SNR) using two phenomenological parity-violating trispectrum templates. These two templates encode the initial conditions for the late-time weak
lensing observables. One template peaks at the squeezed limit, and the other template peaks at the collapsed limit. Our analysis evaluates idealized Dirac-delta source
redshift distributions alongside actual tomographic profiles from the Dark Energy Survey Year 3 (DES Y3) and forecasted profiles for the Legacy Survey of Space and Time Year 10 (LSST Y10). We map the
geometric sensitivity of these templates, providing physical intuition into how the resulting SNR is strongly modulated by the specific source
galaxy redshift distributions and the underlying geometry of the configurations. Furthermore, we rigorously test the validity of the Limber approximation for higher-order angular statistics, demonstrating the necessity of exact line-of-sight numerical integration to capture the parity-violating signal accurately. By demonstrating the theoretical detectability of parity-breaking signatures through weak
lensing, this work serves as a proof of principle, showing how upcoming weak
lensing surveys can be leveraged to probe the fundamental
symmetries of the early universe.
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Applied Physics
Photonuclear Neutron Production in OpenMC: Verification Against MCNPX, FLUKA, and a First-Collision Analytical Solution
Lorenzo Loi, Andrea Missaglia, Guy Stein et al. (+5 more)
The modelling of photonuclear reactions is increasingly important for applications involving high-energy
photon fields, including accelerator-driven
neutron sources, radiation shielding, medical physics, and fusion technologies. OpenMC photonuclear physics is currently available only in an unofficial development branch and requires independent verification before broader scientific use. This work verifies the OpenMC photonuclear implementation using six single-collision broomstick numerical
benchmarks with 2H, 9Be, and 238U targets, irradiated by monoenergetic 5 MeV and 15 MeV
photons and by a continuous 1-20 MeV LINAC-representative spectrum. OpenMC was compared with MCNPX under common ENDF7u photonuclear data, with FLUKA as an independent native-model reference, and with a first-collision analytical solution based on ENDF7u; calculations with the IAEA/PD-2019 library quantified
nuclear-data sensitivity. Energy-resolved, angular, and integrated photoneutron yields were compared. Under common ENDF7u data, OpenMC and MCNPX agreed to within a few tenths of a percent in integrated yield, consistent with the statistical uncertainty, and their energy and angular distributions agreed closely, apart from small kinematic differences in the light-nuclide cases. Replacing ENDF7u with IAEA/PD-2019 produced deviations of up to 13.9%, largest for continuous-source 9Be and monoenergetic 2H (11.3%). FLUKA differed from OpenMC-ENDF7u by up to 9% (monoenergetic) and 2.5% (continuous source) and predicted a markedly different angular distribution for 2H. These results verify that the OpenMC photonuclear implementation reliably reproduces MCNPX under a given
nuclear-data evaluation, while no single library or model is uniformly preferable from the present comparisons alone.
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All authors Lorenzo Loi, Andrea Missaglia, Guy Stein, Carolina Introini, David Breitenmoser, Shaun D. Clarke, Sara A. Pozzi, Antonio Cammi
Mathematical Physics · Cross-listed from math.RA
Iterate Wronskians over $\mathbb{R}^d$ as $N$-ary brackets on $\mathbb{R}[x^1,\ldots,x^d]$: the $N$-bonacci numbers bound the highest total degrees
Markuss G. Kenins and Arthemy V. Kiselev
For the
algebra $\mathbb{R}[x^1,\ldots,x^d]$ of
polynomials in $d\geqslant 1$ variables, regard the complete generalised Wronskian $W_d^k$ of differential order $k\geqslant 1$ over $\mathbb{R}^d$ as the $N=\tbinom{d+k}{d}$-ary Lie bracket. Take an $N$-tuple of
polynomials, calculate their Wronskian, and keep re-using the newly-created
polynomials to produce more of them. The problem is: how fast do their maximal total degrees grow with the number $n$ of iterations of the bracket? Here enter the $N$-bonacci numbers defined by the recurrence $F^{(N)}_n=F^{(N)}_{n-1}+\cdots+F^{(N)}_{n-N}\in \mathbb{N}$. We prove that for any choice of the initial arguments, the sequence of highest total degrees ${\mathsf{D}}^{(N)}_n \geqslant 0$ grows (if at all) asymptotically no faster than the $n$th $N$-bonacci number: $\lim_{n\to+\infty} ({\mathsf{D}}^{(N)}_n/F^{(N)}_n )<\infty$. We show that for $d=1$ and $k$ odd, the highest
polynomial degrees do attain the $N$-bonacci bound. Keywords: Differential
polynomial, $N$-ary Lie bracket, multivariate Wronskian determinant, Fibonacci numbers, $N$-bonacci numbers, asymptotic growth rate, growth of
polynomial degrees, Skolem–Pisot problem.
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Geophysics
Non-normal amplification in multitype Hawkes-ETAS models of earthquake triggering
Didier Sornette
Earthquake triggering is conventionally characterised by a scalar ETAS branching ratio. We develop a three-type Hawkes-ETAS model that resolves strike-slip, normal, and reverse/thrust earthquakes through a directed branching
matrix $N$. While the spectral radius $\rho(N)<1$ controls asymptotic stability, its eigenvector geometry controls finite-generation dynamics. Asymmetric cross-mechanism pathways can render $N$ non-normal, producing large transient and cumulative cascade responses in a strictly subcritical process. We motivate this geometry from receiver-fault availability, Coulomb stress projection, mechanism-dependent magnitude distributions, tectonic loading, and near-degenerate self-triggering. A physically reduced parametrisation separates diagonal self-triggering, a dominant tectonic driver column, and weaker secondary couplings. Numerical examples show that cascade amplification can increase strongly while the
eigenvalues remain fixed. Five tectonically informed scenario
matrices illustrate plausible geometries. The theory produces six falsifiable predictions for mechanism-resolved catalogues and identifies how scalar ETAS fits may absorb multitype amplification into an apparently elevated branching ratio.
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General Relativity and Quantum Cosmology
Jaume Gine
In this work, we explore the possibility that spacetime geometry may emerge from the
entanglement structure of an underlying
quantum-information network. We develop an exploratory framework, termed Fractal
Entanglement Quantum Gravity (FEQG), in which information-theoretic correlations provide a candidate pregeometric structure from which aspects of geometry,
quantum dynamics, and
gravity may arise. An information-based distance on the correlation graph is considered as a possible means of relating
quantum correlations to
geometric separation. The framework also investigates whether scale-dependent and fractal properties of the underlying structure could lead to dimensional flow, potentially approaching an effective dimension of two near the Planck scale. Within a scale-relativistic perspective, nondifferentiable trajectories and
stochastic descriptions are examined as possible ingredients in an effective
quantum dynamics; however, the emergence of the Schrödinger equation from the network structure remains to be established. Similarly, the relation between evolving correlations and gravitational dynamics is explored through candidate generalized field equations, while recovering Einstein
gravity in an appropriate macroscopic limit remains an open problem. Potential phenomenological consequences include dimensional reduction, modifications to gravitational potentials, and possible deviations from standard
quantum mechanics at ultrashort scales. These possibilities are not presented as established predictions, but as directions for further investigation. FEQG thus provides a research program for examining whether
quantum-information structure, fractal geometry, and gravitational phenomena can be connected within a common framework.
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Solar and Stellar Astrophysics
Long-Slit Spectroscopy Of Herbig-Haro Outflow System, Associated With IRAS 01166+6635
T.A. Movsessian, T. Yu. Magakian and A. V. Moiseev
We present long-slit spectroscopic observations of the
outflow associated with an infrared source IRAS 01166+6635, conducted with the 6-m
telescope of the Special Astrophysical Observatory using the SCORPIO-2 focal reducer. The structure of the flow as investigated in detail, its position-velocity diagrams are constructed. The electron densities of the several
knots in the
outflow were estimated, revealing a decrease in its density with increasing distance from the driving source.
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Cosmology and Nongalactic Astrophysics
Minimally modified gravity with Laplacian auxiliary constraints and an inflationary realization
Jakkrit Sangtawee, Antonio De Felice and Khamphee Karwan
We construct a minimally modified
gravity theory that propagates only two tensorial gravitational degrees of freedom around a spatially flat Friedmann–Lemaître–Robertson–Walker (FLRW) background and admits a predictive cosmological perturbation theory. We first show that, in the original four-constraint construction, the homogeneous values of the Lagrange multipliers are not fully determined and nevertheless enter the quadratic tensor action, thereby obstructing cosmological predictivity. We remove this ambiguity by coupling the auxiliary constraints to spatial
Laplacians of the multipliers. The multiplier sector then drops out of the homogeneous background equations while continuing to constrain the inhomogeneous scalar sector. The tensor dispersion relation generically contains both $k^{2}$ and $k^{4}$ contributions, whereas no propagating gravitational vector or scalar mode is present on the generic branch for which the constraint reduction is nondegenerate. We subsequently study a subclass whose gravitational
Hamiltonian density is proportional to the lapse and contains cubic momentum invariants. In this subclass the $k^{4}$ tensor term vanishes and the lapse can be absorbed into a time redefinition at the background level. After coupling a canonical inflaton, the only propagating scalar mode is the inflaton fluctuation, with unit sound speed. For a quadratic potential, departures from general relativity shift the scalar spectral index, while a tensor speed $c_{T}>1$ suppresses the tensor-to-scalar ratio according to $r=16\epsilon_{s}/c_{T}$. The parameter regions compatible with the observational bounds adopted in this work require a superluminal tensor speed; however, very large $c_{T}$ simultaneously reduces the tensor kinetic coefficient and may lower the perturbative cutoff, although determining the actual strong-coupling scale requires a nonlinear analysis.
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Materials Science
Soft-mode nonlinearities away from ferroelectric phase transition
Payel Shee, Ipek Efe, Jingwen Li et al. (+3 more)
The interplay between ionic and electronic subsystems dictates the behavior of structural phase transitions in polar dielectrics, a coupling mediated by soft optical
phonon modes. In incipient ferroelectrics such as SrTiO$_3$ (STO), strong local-field effects can drive the
lattice into a non-perturbative regime near the phase boundary. However, disentangling the distinct contributions of local fields from those of spontaneous macroscopic polarization remains an experimental challenge. Here, we isolate these mechanisms by probing paraelectric STO deep within its symmetric phase, where macroscopic spontaneous polarization is suppressed. Linear terahertz (THz) spectroscopy reveals that the soft mode exhibits a hybrid character, predominantly driven by electronic polarizability. Utilizing two-dimensional THz spectroscopy, we map the underlying nonlinear signals, demonstrating that the system persists in a perturbative regime characterized by robust local-field coherence. By implementing a microscopic model of coupled electronic and
lattice degrees of freedom mediated by local fields, we qualitatively reproduce these multidimensional coherent signatures. Our findings highlight that while local fields are necessary to initiate non-perturbative
lattice dynamics, they are insufficient on their own. This reveals that spontaneous polarization plays a deterministic role in dictating soft-mode nonlinearities in strongly correlated polar dielectrics.
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All authors Payel Shee, Ipek Efe, Jingwen Li, Kshitij V. Goyal, Morgan Trassin, Shovon Pal
Quantum Physics
Path integral approach to the truncated Wigner approximation of driven-dissipative spins
Viktoria Noel, Michael Fleischhauer and Igor Lesanovsky
Phase-space approaches such as the truncated Wigner approximation (TWA) provide an efficient semiclassical framework for performing approximate simulations of the dynamics of open
quantum many-body systems outside the reach of exact numerical methods but beyond the mean-field level. For bosonic systems, TWA is known to be equivalent to a Keldysh path-integral formulation truncated at second order in the so-called
quantum fluctuations. This semiclassical approach provides an alternative transparent route towards approximate
stochastic equations of motion, which can be efficiently solved. Here we establish the corresponding path-integral formulation for interacting open
spin-$1/2$ systems using the continuous $\mathrm{SU}(2)$ phase space. We show, in particular, that a consistent treatment of dissipation requires correctly mapping operator products onto the curved
spin phase space, leading to
stochastic equations that coincide with those obtained from the continuous TWA formulation and thus reproduce the exact dynamics of a single dissipative
spin. Our results provide a unified field-theoretic foundation for the TWA to dissipative
spin dynamics and offer a systematic starting point for extensions beyond the semiclassical approximation.
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Quantum Physics · Cross-listed from math.CO
A Spectral Proof of the Hypergraph Moore Bound
Alexander Schmidhuber and Matthew B. Hastings
A nonempty subfamily of a $k$-uniform hypergraph is an even cover if every vertex lies in an even number of its hyperedges; for $k=2$ these are edge-disjoint unions of cycles, so the minimum size of an even cover is the natural hypergraph analogue of girth. We prove Feige's 2008
conjecture on the hypergraph Moore bound: there are absolute constants $A$ and $C$ (independent of $k$) such that for every $k\ge3$ and every $1\le\ell\le n$, any $k$-uniform hypergraph on $n$ vertices with more than $C\,n^{k/2}/\ell^{k/2-1}$ hyperedges contains an even cover of size at most $A\,\ell\log(en/\ell)$. Our proof is based on sharp spectral bounds for Kikuchi
matrices, which we expect to be of independent interest; we apply them to the refutation of random constraint satisfaction problems in a companion paper.
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Materials Science
The interplay of crystal-field transitions and exchange spin dynamics in a ferrimagnet
Arpita Dutta, Pratyay Mukherjee, Ritwik Mondal et al. (+1 more)
Rare-earth iron garnets offer an ideal platform for exploring the interplay of low-energy excitations and the complex temperature-dependent magnetization dynamics. In these systems, exchange coupling between rare-earth and iron sublattices generates high-frequency collective
spin excitations. In addition, the robust
spin-orbit coupling of localized 4$f$ electrons triggers the
crystal-electric-field (CEF) transitions at THz frequencies. Despite extensive research into the garnet
spin dynamics, the interplay between CEF excitations and exchange modes has remained largely unmapped. Using temperature-dependent THz time-domain spectroscopy, we demonstrate a hybridization between the Yb-ion CEF excitation and the Yb-Fe exchange mode in Gd$_{3/2}$Yb$_{1/2}$BiFe$_{5}$O$_{12}$. This coupling is characterized by a significant redistribution of spectral and temporal weights as the material approaches its magnetization compensation temperature. Notably, the Yb-Fe exchange mode exhibits an anomalous
redshift upon cooling – a reversal of the conventional blue shift typically driven by increased exchange coupling. We trace this phenomenon to a modification of Yb-Fe exchange anisotropy, driven by the interplay of the Fe exchange field and Yb CEF excitations. These findings highlight the critical role of CEF-mediated exchange coupling in shaping low-energy
spin dynamics, positioning rare-earth garnets as a cornerstone for future THz spintronic technologies.
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All authors Arpita Dutta, Pratyay Mukherjee, Ritwik Mondal, Shovon Pal
Cosmology and Nongalactic Astrophysics
Weighted Webs: Morphology-Informed Marked Fields
Mikel Martin Barandiaran, Jessica A. Cowell, David Alonso et al. (+2 more)
The morphology of the
cosmic web formed by the late-time matter distribution encodes cosmological information beyond that contained in standard two-point statistics. Marked power spectra provide a computationally efficient framework to access this higher-order information, by studying the two-point statistics of the density field “marked” (i.e. weighted) by a function of its local environmental density. In this work we explore the potential of marks that are sensitive to the morphology of this local environment, rather than simply its density. We study a broad range of such marks, considering mark functions based on the smoothed density,
tidal shear amplitude, local degree of isotropy and filamentarity, Gaussian transformations of these quantities and a local fractal dimension
estimator. We quantify the merit of different marks in terms of their constraints on key cosmological parameters, including the matter abundance $\Omega_m$, the amplitude of fluctuations $\sigma_8$, and the mass of
neutrinos $M_\nu$. We have found that density-dependent marks continue to provide the largest improvements over the standard power spectrum, while morphology-based marks yield more modest improvements on their own. Nevertheless, combining density- and morphology-based marks consistently enhances cosmological constraints beyond what either class achieves separately, demonstrating that they probe complementary aspects of the underlying matter distribution. These results provide a systematic assessment of morphology-based marked statistics and explore which
geometric properties of the
cosmic web contribute most effectively to cosmological parameter inference. They also establish a physically motivated framework for future investigations of optimal marks and their perturbative connection to higher-order correlation functions.
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All authors Mikel Martin Barandiaran, Jessica A. Cowell, David Alonso, Javier Carrón Duque, Juan García-Bellido
High Energy Physics (Phenomenology)
Sukanta Dutta, Purnath Unnikrishnan and Yashasvi
We investigate charged
lepton-
flavor violation (LFV) induced by dimension-six four-
lepton operators within the Standard Model effective field theory(SMEFT) at a proposed high-energy
muon collider. We study the processes $\mu^{+}\mu^{-}\to e^{\pm}\tau^{\mp}$, $\mu^{+}\mu^{-}\to e^{\pm}\mu^{\mp}$, and $\mu^{+}\mu^{-}\to \mu^{\pm}\tau^{\mp}$ at $\sqrt{s}=3$, $10$, and $14$~TeV, incorporating beam polarization and hadronic $\tau$ reconstruction. Using an optimal-observable analysis of the angular distributions, we perform a global fit to the relevant set of four-
lepton operators. Projected sensitivities reach $C/\Lambda^{2}\sim(0.5-1.2) \times10^{-4}\,\mathrm{TeV}^{-2}$, depending on the
flavor and
chiral structure of the operator, exceeding current limits by up to an order of magnitude. A combined analysis of multiple center-of-mass energies and beam polarizations significantly improves the resolution of correlations among the Wilson coefficients. These results highlight the strong sensitivity of a future multi-TeV
muon collider to charged LFV four-
lepton interactions, establishing it as a powerful probe of the SMEFT parameter space.
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Mesoscale and Nanoscale Physics
Wayne M. Witzel, Jesse J. Lutz, Matthew D. Grace et al. (+3 more)
The dynamics of a
nuclear spin bath generates
magnetic noise that is a key contributor to the decoherence of electron
spin qubits in electrostatically-defined
quantum dots. In this paper, we extend the cluster correlation expansion (CCE) technique, which has proven useful for predicting solid-state
qubit coherence times across various settings but is limited to shorter time scales, to incorporate
stochastic treatments of cluster dynamics in order to efficiently predict slow drifting Overhauser fields over longer time scales. This approach combines
quantum evolution with classical rate
matrices to enable simulation across a wide range of temporal regimes required to simulate, for example, the long-time convergence of the ergodic $T_2^*$ from Ramsey experiments. Our methodology is validated against experimental data from various silicon
spin qubit systems, demonstrating a strong agreement between simulation and measurement of Ramsey experiments presented in the form of $T_2^*$ versus averaging time, autocorrelation functions, as well as power spectral densities. Furthermore, we demonstrate significant back-action effects through modeling and experiment; specifically, the dynamics of the
nuclear spin bath depends upon the electron
spin occupation schedule. Finally, our modeling quantitatively predicts the benefits from compensating for the slow drift of Overhauser fields in
qubit operations. Our findings indicate that compensating for an Overhauser rotation measured $\Delta t$ in the past results in an effective $T_2^*$, which we denote $\tilde{T}_2^*(\Delta t)$ for clarity, under certain scenarios of interest, can be one or two orders of magnitude larger than the ergodic $T_2^*$ if the Overhauser rotation is re-characterized every 100 milliseconds; that is, $\tilde{T}_2^*(\Delta t = 100~{\rm ms})$ can be $10$ to $100$ times larger than $T_2^*$.
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All authors Wayne M. Witzel, Jesse J. Lutz, Matthew D. Grace, Natalie D. Foster, Ryan M. Jock, Dwight R. Luhman
Materials Science
Extracting Atomic Environments for Machine Learning Interatomic Potentials
Jared C. Stimac, Fei Zhou, Kyle Bushick et al. (+4 more)
In order to appropriately capture large-scale material features and emergent phenomena via atomistic simulations, such as Molecular Dynamics (MD), the system scale can range up to hundreds of millions of atoms. However, the force-field models that drive those simulations are generally trained with Density Functional Theory (DFT) reference data, limited to relatively small configurations on the order of 100s or 1000s of atoms. To compute DFT forces on atoms in regions of interest, for example for active-learning or on-the-fly training of interatomic potentials, one needs to extract a small set of atoms from the larger simulation box, and typically work with periodic boundary conditions for DFT. However, methods to select the shape and size of this extracted set of atoms, as well as to generate a potentially necessary passivating envelope, have not been systematically analyzed. In this work, we
benchmark several techniques, including a generative
diffusion-based artificial intelligence (AI) approach, for extracting atomic environments from large, bulk configurations and
embedding them into smaller configurations suitable for DFT calculations with periodic boundary conditions. We test with a diverse set of material systems, which includes amorphous $\mathrm{SiO_2}$, Ta with screw dislocations, and molten C. We demonstrated a notably simple procedure, a method we refer to as deletions, yields superior performance over an array of alternative extraction methods.
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All authors Jared C. Stimac, Fei Zhou, Kyle Bushick, Bo Lei, Sebastien Hamel, Amit Samanta, Vincenzo Lordi
Solar and Stellar Astrophysics
Automated Solar Radio Burst Detection Using Deep Learning on Augmented e-Callisto Data
Vincenzo Timmel, André Csillaghy and Christian Monstein
Solar radio bursts are signatures of energetic events associated with
solar flares and coronal mass ejections and can interfere with terrestrial and space-based communication systems. Real-time automatic burst monitoring enables early warnings tens of minutes to hours before associated particles reach Earth and provides the basis for long-term statistical studies. The e-Callisto network is a worldwide system of
solar radio spectrometers providing continuous observations, with its instruments collectively covering frequencies from approximately 20 MHz to 1 GHz. Burst detection and labeling currently rely largely on human experts, limiting scalability and real-time applicability due to hardware heterogeneity and low signal-to-noise ratios.
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High Energy Physics (Theory)
Krylov-Space Memory Cores
Mohsen Alishahiha and Mohammad Javad Vasli
We introduce Krylov-space
memory cores as stationary, depth-resolved structures that reveal how anomalous initial-state
memory is organized inside the Krylov space of otherwise thermalizing nonintegrable systems. The stationary occupation profile identifies where late-time probability is concentrated along the Krylov chain, while complementary diagnostics of residual equilibration fluctuations, deviation from the Gibbs reference, and long-time Krylov-current fluctuations determine the physical character of that region. Across weak thermalization, confinement-induced anomalous dynamics, and many-body scarring, anomalous initial states develop compact low-depth
memory cores that carry appreciable residual fluctuations, Gibbs mismatch, and persistent current-fluctuation activity. These cores are often embedded within substantially broader stationary occupation
halos. The reference states considered, by contrast, do not exhibit a comparable combination of signal strength and spatial compactness. An auxiliary integrable comparison further shows that compact Krylov
memory is state selective rather than a generic consequence of integrability. Krylov-space
memory cores therefore provide a stationary framework for identifying where structured
quantum memory resides and how it remains dynamically encoded.
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General Relativity and Quantum Cosmology
Causal Green function decomposition for quantum black hole seismology
Xi-Li Zhang and Jing Ren
The growing sensitivity of gravitational-wave detectors enables increasingly precise tests of black hole (BH) ringdown spectroscopy. BH quasinormal modes (QNMs) are, however, spectrally unstable: small near-horizon modifications can produce a drastically different QNM spectrum, while causality requires the
prompt ringdown to remain BH-like until the reflected signal returns.
Quantum BHs with substantial interior reflection provide a natural setting for this tension, yet the relation between their time-domain waveform and different QNM spectra still lacks a consistent picture. In this work, we systematically examine the time-domain Green function for
quantum BHs, considering sources located outside and inside the light-ring potential barrier. By decomposing the Green function into causally distinct components and choosing the corresponding inverse-Laplace contours consistently, we clarify how the response is built from different sets of QNMs. We find that the
quantum BH QNM reconstruction always faithfully describes the signal once the curved spacetime is probed, but its practical efficiency depends strongly on the evolutionary stage. Before interior reflection becomes relevant, we prove that this basis is formally equivalent to the BH QNM and tail expansions, with convergence properties sensitive to source location. At late times, the long-lived modes provide an efficient basis. Time-domain simulations confirm these results, providing a unified causal framework for BH spectroscopy and
quantum BH seismology.
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Cosmology and Nongalactic Astrophysics
Anisotropic Secondary Bias of Dark Matter Haloes in a $\Lambda$CDM Universe
Qinglin Ma and Cheng Li
Secondary bias is the dependence of
halo clustering on properties beyond
halo mass. Using the $z=0$ TNG300-1-Dark simulation, we study anisotropic secondary bias (ASB): the variation of secondary bias with direction relative to the
halo major axis. We first use ordinary, orientation-averaged secondary bias (OSB) as a baseline to compare three environmental manifestations:
halo-environment
alignment, outer matter anisotropy, and
tidal anisotropy. Matching
tidal anisotropy suppresses much of the OSB, whereas matching
halo-environment
alignment or outer matter anisotropy does not. ASB behaves differently. It is weak for formation time, concentration, and triaxiality, but strong for both
spin definitions and minor-to-major axis ratio; slowly rotating and more elongated
haloes are more strongly aligned with filamentary structure. Matching
halo-environment
alignment substantially reduces the
spin- and shape-dependent ASB signals, whereas matching
tidal anisotropy or the outer matter axis ratio leaves them largely intact.
Halo definition has little impact on ASB, yet strongly affects low-mass
spin bias: including unbound particles can move dense-environment
haloes with low bound-particle
spin into the high all-particle-
spin sample. These results clarify which clustering signals are associated with
halo-environment
alignment, matter anisotropy, or
tidal anisotropy, and which are sensitive to
halo definition.
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Materials Science
Singular geometry and eigenframe topology in local rank-2 tensor observables
I. C. J. Yap, B. Doerschel, S. Q. Jin et al. (+6 more)
Many observables are symmetric second-rank tensors, reported through magnitude-ordered principal values and axes. This chart folds tensor space: the parameters develop cusps and exchange labels where the tensor is smooth. It also hides a global effect: an arrow carried along a principal axis around a loop encircling a degeneracy can return reversed, defining a binary return parity, invariant under smooth deformations of the loop avoiding degeneracy. For tensor fields, this structure is long established, but the parameters are coordinates of the domain on which the field is defined, and the degeneracies are a feature of that particular field. Here we show that the electric field gradient (EFG) carries the same structure in a control space: a traceless observable at a single probe site, steered through its five-dimensional tensor space by
symmetry-adapted strain, with the encircling loop applied rather than found. First-principles calculations reveal an isolated degeneracy with nontrivial parity in rutile TiO$_2$, point- or line-like degeneracies in SnO$_2$ depending on the control slice, and access to all five EFG components in cubic MgO. Thus, return parity becomes accessible for a local observable, and strain-tuned, orientation-resolved hyperfine spectroscopy offers a route to reconstruct it.
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All authors I. C. J. Yap, B. Doerschel, S. Q. Jin, T. T. Dang, P. M. Scott, H. C. Hofsaess, D. C. Lupascu, A. Krawczuk, J. H. Schell
Instrumentation and Methods for Astrophysics
The IMF package: a toolkit implementing mass functions and statistical tools to analyze them
Theo Richardson, Adam Ginsburg and Sergey Koposov
Mass functions are used in all areas of astrophysics. The
stellar initial mass function (IMF), in particular, plays a central role in modeling
stellar populations in
galaxies. However, few dedicated tools for working directly with the IMF and its precursor functions are widely available. We present the $\texttt{imf}$ package, a Python library integrated into the wider scientific Python ecosystem that implements common and variant forms of mass functions, especially the IMF and its pre- and protostellar equivalents, as probability distribution functions based on SciPy's statistics architecture. This package enables the performance of operations such as sampling and integration on a wide array of highly customizable mass functions. $\texttt{imf}$ is publicly available on the Python package index $\texttt{pypi}$ under the project name $\texttt{initial_mass_function}$.
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Solar and Stellar Astrophysics
Understanding the Travel-time Asymmetry of Acoustic Waves in Sunspots With Time-distance Helioseismology
Haiyu Li, Tobías Felipe, Elena Khomenko et al. (+3 more)
Mapping the subsurface structure and flow field of sunspots has been a challenging task for helioseismology. In this work, we investigate the propagation of acoustic waves in a sunspot in NOAA active region 11312 using time-distance helioseismology. Travel times of waves traveling into and out of the sunspot are measured as functions of travel distance and azimuthal angle relative to the local radial direction. The same time-distance analysis is also applied to a simulated data based on a magnetohydrostatic (MHS) model of sunspot, and forward modeling of travel times is performed using ray tracing based on both the MHS sunspot model and a magnetohydrodynamic (MHD) simulation. We find that both ingoing (traveling from the quiet area into the sunspot) and outgoing waves (traveling from the sunspot into the quiet area) have shorter travel times than in the quiet Sun, with travel-time reductions of up to 40 s. The magnitude of the mean time shift is largest for waves traveling along the radial direction at small travel distances. A clear asymmetry is detected between ingoing and outgoing waves: outgoing waves generally exhibit shorter travel times. This asymmetry is strongest for radial direction and small travel distances, with differences exceeding 1 min for 3.5 mHz and 4.5 mHz waves. From the results of both observations and models, our analysis indicates that the overall reduction in travel time could be primarily caused by the combined effects of Wilson depression,
magnetic field, and wave-speed perturbations, while the ingoing-outgoing asymmetry could be partly attributable to subsurface flows. Although the forward-modeling results reproduce several qualitative features of the observations, quantitative discrepancies remain, highlighting limitations of current sunspot models and ray-theoretical approximations.
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All authors Haiyu Li, Tobías Felipe, Elena Khomenko, Hui Tian, Paul Rajaguru, Yuhang Gao
Mesoscale and Nanoscale Physics
Element-Specific Visualization of Layer-Parity and Twist-Dependent Magnetism in CrSBr
Aalok Tiwari, Shubhada Patil, Ravi Kumar Bandapelli et al. (+16 more)
Van der Waals (vdW) based antiferromagnets (AFMs) are an ideal platform for probing and understanding thickness- and twist-angle-dependent emergent
spin phenomena. However, element-specific nanoscale characterization of the
spin structure in atomically thin vdW-based AFMs systems and layer-parity effects remain elusive, making them crucial for both fundamental insight into low-dimensional magnetism and the rational design of spintronic devices based on these materials. Here, we utilize X-ray
magnetic circular and linear dichroisms paired with photoemission electron microscopy to resolve the
magnetic order in atomically thin CrSBr. Our comprehensive measurements reveal CrSBr
magnetic structure at the nanoscale and its dependence on the layer number, surface encapsulation, temperature, and applied field. Moreover, in the orthogonally twisted
bilayer configuration, obtained by twisting two CrSBr
ferromagnetic monolayers by 90$^\circ$, the
magnetic easy axis fundamentally differs from the individual monolayers, unlocking a new pathway for moiré magnetism.
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All authors Aalok Tiwari, Shubhada Patil, Ravi Kumar Bandapelli, Alevtina Smekhova, Abhishek Kumar, Wenhao Liu, I-Hsuan Kao, Zhenhong Cui, Raghvendra Posti, Brandon Tran, Zixin Zhai, Priti Yadav, Sandy Adhitia Ekahana, Alexander X. Gray, Bing Lv, Vivekanand Shukla, Florian Kronast, Simranjeet Singh, Jyoti Katoch
Instrumentation and Methods for Astrophysics
Advancing X-Ray Camera Front-End Electronics Architecture through the AXIS-TAP Technology Platform
Jill Juneau, Declan O'Neill, Peter Orel et al. (+19 more)
Advancing time-domain soft X-ray astronomy demands focal plane readout electronics capable of high-speed digitization with low noise while maintaining spectral fidelity across multiple detector channels. The Advanced X-ray Imaging Satellite (AXIS), a NASA Probe-class mission concept, provided the driving requirements and heritage for developing a generalized high-speed (>=5 fps) camera Front-End Electronics (FEE) architecture applicable to future soft X-ray missions. The FEE architecture defines a modular, dual-box redundant configuration to operate a focal plane of four 16-channel CCDs, with functional partitioning for power distribution, thermal management, mechanism control, and image data acquisition and transmission to the spacecraft. To validate the core signal chain architecture, particularly the analog-to-digital conversion, FPGA-based processing, and Ethernet data transmission, a dedicated technology demonstrator, AXIS-TAP (ADC Testing and Acquisition Platform), has been designed and is currently in fabrication. AXIS-TAP employs commercial equivalents of radiation-tolerant components (FPGA, ADCs, Ethernet PHY) and interfaces directly with the STA Archon benchtop readout system, enabling simultaneous image acquisition from both systems to validate that the flight-like architecture achieves equivalent or superior noise performance. This paper presents the FEE architectural framework, the AXIS-TAP demonstrator design, and the design principles that enable scalability to future soft X-ray missions with similar detector requirements. Performance validation results will be reported upon completion of AXIS-TAP system integration and testing.
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All authors Jill Juneau, Declan O'Neill, Peter Orel, Eric Miller, Sven Herrmann, Gregory Prigozhin, Robert Goeke, Elio Angile, Mark Bautz, Steven Allen, Tanmoy Chattopadhyay, Kevan Donlon, Michelle Gabutti, Catherine E Grant, Beverly LaMarr, Christopher Leitz, Glenn Morri, Abigail Y. Pan, Tonya Peshel, Artem Poliszczuk, Haley Stueber, Keith Warner