High Energy Physics (Theory)
Bulk Criticality and Boundary Spectra in AdS from Matrix Product States
Faizan Bhat
We study interacting scalar
quantum field theories in anti-de Sitter (AdS) space using a tensor-network approach based on
matrix product states. We develop methods for extracting low-lying boundary spectra from global-AdS energy levels, probing bulk criticality through finite-size scaling in the AdS radius, and identifying conformal boundary conditions. Applying these methods to scalar $\phi^4$ theory in $\mathrm{AdS}_2$, we compute the lowest non-trivial $\mathbb{Z}_2$-odd and even boundary scaling dimensions non-perturbatively. We then locate the bulk $\mathbb{Z}_2$
symmetry-breaking transition and extract critical exponents and central charge consistent with the 2D Ising universality class. At the critical point, we determine the low-lying boundary spectrum and use it to identify the $\mathbb{Z}_2$-preserving free/ordinary Ising conformal boundary condition, thereby characterising both the bulk and boundary universality classes.
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High Energy Astrophysical Phenomena
The Gamma-ray Burst Jet Energy Distribution Suggests A Quasi-universal, Weakly Magnetized Jet Evolving Over Cosmic Time
Nicole M. Lloyd-Ronning, Fabio De Colle, Gal Birenbaum et al. (+2 more)
We present distributions of gamma-ray burst observed and inferred properties for those GRBs with
redshifts. We show that the isotropic energy distribution, which spans over four orders of magnitude, can be reproduced reasonably well under a simplistic assumption that every observed GRB originates from a quasi-universal jet with roughly the same decreasing power-law profile of energy as a function of angle, with a power-law index of $ 3 \lesssim \zeta \lesssim 4$. The spread in the observed distribution can be explained by the variation in observer viewing angle alone. Furthermore, this power-law jet structure provides an even better fit to both the isotropic energy and luminosity distributions if the isotropic energy normalization evolves as a function of
redshift in a manner that has been suggested by a range of previously published studies. The relatively steep power-law index of this jet is consistent with the structure predicted by simulations of weakly magnetized jets in collapsars, whereas simulations of hydrodynamic jets predict a structure shallower than what we find here. The predicted afterglow light curves within this model framework show steepening behavior at times commensurate with observed jet break times.
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All authors Nicole M. Lloyd-Ronning, Fabio De Colle, Gal Birenbaum, Omer Bromberg, Jarrett Johnson
Earth and Planetary Astrophysics
GEMS JWST: Hold on to your HATS(-6 b), a sub-solar metallicity giant planet with water, methane and ammonia in its atmosphere
Giannina Guzmán Caloca, Caleb I. Cañas, Nicole L. Wallack et al. (+16 more)
HATS-6 b is one of several recently discovered
Giant Exoplanets orbiting M-
dwarf Stars (GEMS) and is part of a JWST survey that aims to compare bulk and atmospheric properties of these rare
planets against their FGK
star counterparts. HATS-6 b is a warm ($\mathrm{T_{eq}}\sim700$ K), Saturn-mass ($M_p\sim0.3~\mathrm{M_J}$), Jupiter-radius ($R_p\sim1~\mathrm{R_J}$)
planet that transits its
star every $\sim$ 3 days. In this study, we present the transmission spectrum of HATS-6 b obtained with two transits using the PRISM mode of JWST Near Infrared Spectrograph (NIRSpec), spanning a wavelength range of $0.6-5.3$ um. Analyzing these JWST observations using an iterative approach between forward modeling and free chemistry
retrievals, we derive a low
metallicity ($\log\mathrm{[M/H]}=-1.99^{+0.2}_{-0.2}$) sub-
solar C/O ($\log\mathrm{[C/O]=-0.46^{+0.2}_{-0.2}}$) atmosphere, and find strong evidence for H$_2$O, CH$_4$, and NH$_3$ at volume mixing ratios (in $\log[X]$) of $-4.88_{-0.24}^{+0.25}$, $-5.38_{-0.19}^{+0.18}$, and $-6.03_{-0.19}^{+0.18}$, respectively. We consistently retrieve a significantly lower $\mathrm{T_{eq}}$ than predicted from the orbital configuration of HATS-6 b, which was impervious to any data reduction and
retrieval choices, suggesting a non-zero bond albedo. Our planetary interior models retrieve bulk
metallicities three orders of magnitude larger than our retrieved atmospheric
metallicity, also suggesting that the atmosphere is not well-mixed. We find an excess feature around 3 um, and expand on possible explanations for this, such as the presence of HCN or hydrocarbons like C$_2$H$_4$. Yet, due to the degeneracies present for hydrocarbon features in this wavelength region, we do not draw any conclusions about the excess feature and instead encourage further observations and follow-up of this intriguing target.
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All authors Giannina Guzmán Caloca, Caleb I. Cañas, Nicole L. Wallack, Erin M. May, Shang-Min Tsai, Simon Müller, Ravit Helled, Shubham Kanodia, Jacob Lustig-Yaeger, Knicole D. Colón, Ian Czekala, Megan Delamer, Peter Gao, Te Han, Jessica Libby-Roberts, Suvrath Mahadevan, Anjali A. A. Piette, Gu{\dh}mundur Stefánsson, Kevin B. Stevenson
Astrophysics of Galaxies
A comprehensive cluster census of Orion. An application of the Significance Mode Analysis (SigMA) algorithm
Alena Rottensteiner, Sebastian Ratzenböck, João Alves et al. (+2 more)
Precise astrometric surveys and modern clustering
algorithms are working in step to transform our view of
star-forming regions. By revealing a much richer substructure than previously accessible, they pave the way for reconstructing
star formation histories by accurately resolving and age-dating individual sub-populations. The Orion
star-forming complex is the best-studied
stellar nursery in the
solar neighborhood and the nearest one currently forming massive
stars. Even so, a comprehensive characterization of its substructure, including a homogeneous age mapping and extinction analysis, is still incomplete. Here, we present the most complete census of
stellar populations across the Orion complex from the newest version of the SigMA
algorithm and outline our additions and improvements to the
algorithm that have extended its usage to distant (>300 pc) regions. We separate the Orion complex into 47 co-spatial and co-moving
stellar groups comprising 11,996 reliable members, with ages ranging from 1.5 to 25 Myr. To evaluate the statistical robustness of each group, we derive cluster persistence values and individual membership probabilities for each source from 10 independent clustering repetitions. Our group memberships agree well with the literature, but SigMA consistently finds a factor of ~2-3 more members. In particular, it resolves more very young populations, such as NGC 2024, RV Orionis, B30, NGC 1977, NGC 2068, and NGC 2071, than previous
algorithms. In addition to recovering 28 known clusters and three groups previously classified as substructures, we present 16 new co-eval substructure candidates of the Orion
star-forming complex. This work builds up a new high-resolution time-resolved picture of Orion. This spatio-temporal map allows us to relate its
stellar content to the surrounding ISM and paves the way for a detailed analysis of its
star formation history in the future.
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All authors Alena Rottensteiner, Sebastian Ratzenböck, João Alves, Stefan Meingast, Sebastian Hutschenreuter
Earth and Planetary Astrophysics
Causes of Hot Jupiter Inflation from Causal Discovery
Zehao Jin, Mohamad Ali-Dib, Yujia Zheng et al. (+3 more)
Hot Jupiters often have radii larger than predicted by standard cooling–contraction models, but it remains unclear which process supplies or preserves the extra internal heat. We analyze 328 short-period
giant planets with measured $M_p$, $R_p$, $P_{\rm orb}$, and host-
star $T_{\rm eff}$ using causal discovery, a statistical framework that asks which observed properties remain directly connected to
planet radius after the others are accounted for. As a check, the same pipeline recovers the expected mass–radius connection for a super-Earth control sample. For hot Jupiters, the preferred graph links $R_p$ directly to $P_{\rm orb}$ and $T_{\rm eff}$, but not to $M_p$. Since incident flux increases with $T_{\rm eff}$ and decreases with $P_{\rm orb}$ at fixed
stellar properties, this paired dependence is naturally interpreted as a population-level signature of irradiation-regulated inflation. Comparing the graph with analytic radius-excess scalings suggests a comparatively important role for Gold–Soter thermal tides, with kinetic/mechanical heating and ohmic dissipation potentially contributing alongside them. Purely period-controlled gravitational tides are disfavored as the sole explanation because they lack a leading dependence on
stellar temperature. Distinguishing thermal tides, kinetic/mechanical heating, ohmic dissipation, and mixed scenarios will require radius-excess measurements that control for incident flux, age, composition,
stellar properties, and selection effects. More broadly, this work shows how causal discovery can turn population-level
exoplanet data into physically interpretable tests of hot-Jupiter inflation. Causal discovery complements parametric
Bayesian population models by testing which observables retain direct conditional dependence on $R_p$ without imposing a specific radius relation, although the modest sample size limits the scope of the inferred graph.
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All authors Zehao Jin, Mohamad Ali-Dib, Yujia Zheng, Mario Pasquato, Benjamin L. Davis, Andrea V. Maccio
Cosmology and Nongalactic Astrophysics
Merging Galaxy Clusters and the Search for New Physics of Dark Matter: A Review
Rogério Monteiro-Oliveira
Merging
galaxy clusters represent one of the most powerful macroscopic laboratories in the Universe for searching for new physics within the dark sector. High-velocity
cosmic collisions inherently separate the dark matter and
stellar components from the highly collisional, X-ray-emitting intracluster gas. These massive systems provide an ideal environment to probe the fundamental nature of dark matter, specifically testing whether it behaves as a strictly collisionless particle or exhibits non-zero self-interactions. While pioneering systems like the Bullet Cluster historically demonstrated the macroscopic decoupling of dark and ordinary matter, the field has evolved into a sophisticated discipline driven by multi-disciplinary methodologies. This review synthesizes recent theoretical and empirical advances in interpreting post-collision dynamics. It examines how the synergy of combined approaches—integrating multi-wavelength observations from gravitational
lensing and X-ray mapping with high-fidelity N-body hydrodynamical simulations—allows the translation of macroscopic spatial observables into stringent constraints on microscopic particle properties. Through this synthesis, the work evaluates how leveraging heterogeneous merger ensembles can reliably advance the ongoing search for physics beyond the standard cosmological model.
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High Energy Astrophysical Phenomena
General relativistic hydrodynamics of stellar tidal disruptions in Kerr spacetime: methods, validation, and first applications
Diego Calderón and Stephan Rosswog
The disruption of a
star by the
tidal field of a super-massive black hole may provide insights into dormant and otherwise hard-to-study
galactic nuclei. State-of-the-art numerical tools have not converged on the importance of the strong relativistic effects in the disruption of
stars by potentially spinning black holes. We present a specialised numerical tool to perform global hydrodynamic simulations of
stellar tidal disruptions in curved spacetimes. We quantify the role of impact strength and black hole
spin onto the
stellar structures and mass fallback rates. We adapted the code SPHINCS_BSSN to perform General Relativistic Smoothed-Particle Hydrodynamics (GRSPH) simulations of
stellar tidal disruptions in Kerr metric. We coupled the code with a Newtonian self-
gravity module, and we added the option to use an
entropy evolution formulation to handle numerically challenging situations. Besides describing the implementation and code validation, we present a set of 18 simulations of
parabolic tidal disruptions of
stellar polytropes to investigate the effect of impact strength and black hole
spin. We demonstrate that SPHINCS is capable of performing GRSPH simulations, reproducing
benchmark tests to machine precision. Our
stellar tidal disruption simulations show that the fallback rates agree with state-of-the-art modelling. Deep events result into structures where self-
gravity plays no role, the mass fallback rates peak at lower values, and rise-to-peak timescales decrease with impact strength. In these cases the black hole
spin affects noticeable these quantities increasing (decrease) both fallback rate peak and rise-to-peak timescale for prograde (retrograde)
spin. Last, fallback rates tend to decay with the characteristic $t^{-5/3}$ on long timescales. The results show that SPHINCS can simulate high-resolution
stellar tidal disruptions in Kerr metric at a reasonable computational time.
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High Energy Physics (Theory)
Pure gravity OPE density for genus-two handlebody in $\text{AdS}_3$
Saptaswa Ghosh and Sounak Pal
In this work, we compute the operator product expansion density for the genus-two handlebody by exploiting its duality with extremal conformal field theories arXiv:0710.2129. Using a Poincaré construction, we analytically determine the first- and second-order corrections in the pinching parameter to the genus-two OPE density through a direct inversion of the partition function. As a consistency check, we also compute the genus-one density within the same Poincaré framework and find perfect agreement with the result obtained from the lightcone bootstrap analysis arXiv: 1906.04184. It is known that, at genus one, the OPE density of extremal CFTs exhibits a negativity pathology for states lying just above the black-hole threshold. We show that this pathology continues to persist at genus two, despite the emergence of a nontrivial inversion kernel. In particular, the OPE density associated with states of both odd and even
spin $j_i$ remains negative within a very narrow band above the black-hole threshold. We further analyze the sharp transition from large positive to large negative values of the OPE density across a curve along which the density vanishes.
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High Energy Astrophysical Phenomena
Resolving Nearby Supermassive Black Holes with the Black Hole Explorer
Yuto Akiyama, Kazunori Akiyama, Dominic W. Pesce et al. (+12 more)
Recent Event Horizon
Telescope results have demonstrated unique and transformative science in gravitational physics and black hole astrophysics enabled by event-horizon-scale imaging of supermassive black holes (SMBHs). Nevertheless, the angular resolution of current ground-based very long baseline interferometry (VLBI) arrays limits such studies to only two sources, precluding systematic investigations of horizon-scale emission across a nearby SMBH population. The proposed Black Hole Explorer (BHEX), a millimeter/submillimeter space VLBI mission, would overcome this limitation by delivering substantially higher angular resolution. Here, we present a series of simulated observations to assess a population of nearby horizon-scale targets accessible with BHEX. Based on a recently developed SMBH number density model, we find that BHEX could infer black hole masses for ~70-90 sources from size measurements, constrain
magnetic field structures through linear polarization imaging for ~20-30 sources, and resolve black hole shadows for ~20-25 sources. Targeted observations of ~50 nearby SMBHs are expected to yield measurements for ~30 source sizes and ~10 shadows and linear-polarization patterns. These projections are supported by detailed imaging simulations of general relativistic magnetohydrodynamic (GRMHD) models for eleven nearby SMBHs. Together, our results highlight BHEX as a powerful facility for revealing the demographics of SMBH properties across diverse
accretion states,
radio loudness, host
galaxy environments, and viewing geometries.
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All authors Yuto Akiyama, Kazunori Akiyama, Dominic W. Pesce, Daniel C. M. Palumbo, Angelo Ricarte, Paul Tiede, Marvin N. Martinez, Hikaru Yoshida, Avery E. Broderick, Aya E. Higuchi, Sara Issaoun, Neil M Nagar, Kotaro Niinuma, Venkatessh Ramakrishnan, Xinyue Alice Zhang
High Energy Physics (Theory)
A geodesic distance interpretation of Lanczos coefficients
Le-Chen Qu
We study the spread complexity of the infinite-temperature thermofield double state in large-$N$ random
matrix theory and investigate the physical meaning of its Lanczos coefficients $b_n$. The leading density of states defines a family of orthogonal
polynomials whose recursion coefficients coincide with the Lanczos coefficients of the associated Krylov dynamics. Starting from the Coulomb-gas equation, we derive a pair of nonlinear relations for these coefficients, which we call the Lanczos equations. For normalizable one-cut ensembles, the Lanczos coefficients approach constants at large Krylov index, rendering the asymptotic Krylov chain translationally invariant and the late-time growth of spread complexity linear, with the growth rate given by the spectral average of the group velocity obtained from a Bloch-wave analysis. For an even potential, we further show that the difference between consecutive squared Lanczos coefficients, $b_{n+1}^2-b_n^2$, is the generating function for two-legged maps whose marked legs are separated by the exact geodesic distance $n$. Consequently, the spread complexity acceleration operator equals twice the geodesic generating operator. We illustrate these results in the quartic
matrix model, where the expansion in the quartic coupling counts tetravalent planar maps, and in the double-scaled Sachdev–Ye–Kitaev model, where the auxiliary
Hilbert space can be identified with the physical chord
Hilbert space.
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High Energy Astrophysical Phenomena
Probing the $\gamma$-ray emission region and the connection to jet ejections in NRAO 150 with VLBI
L. C. Debbrecht, G. F. Paraschos, E. Ros et al. (+7 more)
Relativistic jets launched by active
galactic nuclei are fundamental for understanding the physics of accreting supermassive black holes and their immediate environments, yet the origin of these jets remains an open question. NRAO 150 is a blazar with a complex relativistic jet morphology that evolves on short timescales due to strong projection effects, enabling detailed kinematic analysis. In this study, we utilise data by the Very Long Baseline Array and the European VLBI Network from 2010 until 2019 at 43 GHz, to understand the formation and launching processes of the jet in NRAO 150. We study the $\gamma$-ray and
radio light-curves, together with total intensity and linear polarisation information to probe the connection between flaring events, $\gamma$-ray emission, and the ejection of new jet features. Furthermore, we investigate the
magnetic field configuration in the innermost jet region, as captured in polarised light, to gain insights about its configuration before, during, and after a $\gamma$-ray
flare. Our results indicate a close temporal link between the $\gamma$-ray flaring activity and the ejection of new VLBI jet components, suggesting that the high-energy emission is produced downstream of the VLBI core. The combined kinematic and polarimetric evidence further points to a toroidal
magnetic field in the inner jet, highlighting the key role of
magnetic fields in governing both jet dynamics and high-energy emission in NRAO 150.
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All authors L. C. Debbrecht, G. F. Paraschos, E. Ros, I. Agudo, T. P. Krichbaum, H. Müller, S. G. Jorstad, A. P. Marscher, M. A. Gurwell, J. A. Zensus
Quantum Gases
Hydrodynamization in 1D Bose gases at nonzero temperature
Jeff Leiberton and Marcos Rigol
Hydrodynamization refers to the remarkably rapid process in relativistic heavy-ion collisions by which hydrodynamic descriptions become applicable. Following the observation of analogous behavior in ultracold one-dimensional (1D) Bose gases, hydrodynamization has been conjectured to be a universal dynamical phenomenon in
quantum systems following high-energy quenches. Theoretical studies in this cold-atom setting have so far been restricted to quenches from ground states. Here we study how nonzero temperatures affect hydrodynamization. Specifically, using a homogeneous 1D gas of hard-core
bosons, we explore how the initial temperature affects the timescales associated with hydrodynamization and prethermalization following a Bragg-pulse quench. We find that while the hydrodynamization coherence time remains unchanged, increasing temperature shortens both the damping time of the hydrodynamization oscillations and the prethermalization time. We argue that this is mainly the result of the broadening of the initial rapidity distribution, and introduce a nonzero-temperature dephasing time defined in terms of the extent of the rapidity distribution.
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High Energy Astrophysical Phenomena
A JWST/MIRI Study of Dust in a Sample of Normal Type IIP Core Collapse Supernovae
Bhagya M. Subrayan, David J. Sand, Olivia Culbert et al. (+24 more)
Core collapse
supernovae (CCSNe) are invoked as major
dust producers in the early Universe, yet the amount of
dust they form, the timescale over which it grows, and the physical conditions that regulate the yield remain uncertain. We present a detailed JWST/MIRI mid-infrared (MIR) imaging census of 11 nearby Type IIP CCSNe spanning $\sim$1-7 yr after explosion, investigating
dust emission across the different phases of their
evolution. The spectral energy distributions show a coherent
evolution from hot ($\sim$1500 K), 5-8 $\mu$m emission at $\sim$400 d to prominent 10 and 18 $\mu$m emission features at later epochs ($\sim$600-2500 d). The cool
dust temperatures range from $\sim120$ to $250$ K and
dust masses from $\sim10^{-4}$ to $10^{-2} M_{\odot}$. The current sample shows no statistically significant correlation between measured
dust mass and peak luminosity, plateau duration, or explosion energy. SNe with early high ionization features, indicative of confined CSM, are often among the
dust-rich objects in the sample. The measured 1-7 yr
dust yields are insufficient to account for
dust in typical $z > 6$
galaxies, but support a role for CCSNe as producers of seed
dust for subsequent grain growth.
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All authors Bhagya M. Subrayan, David J. Sand, Olivia Culbert, Jennifer E. Andrews, Jeniveve Pearson, Griffin Hosseinzadeh, Saurabh W. Jha, Stefano Valenti, K. Azalee Bostroem, Conor L. Ransome, Aravind P. Ravi, Aysha Aamer, Moira Andrews, Emma R. Beasor, Collin Christy, Yize Dong, Noah Franz, Emily Hoang, Brian Hsu, Jacob Jencson, Lindsey A. Kwok, M. J. Lundquist, Darshana Mehta, Nicolas Meza Retamal, Manisha Shrestha, Nathan Smith, Sergiy Vasylyev
Astrophysics of Galaxies
A Critical Eddington Ratio for X-Shaped Radio Galaxies
David Garofalo
We derive a quantitative condition for the formation of X-shaped
radio galaxies by evaluating the competition between black hole
spin evolution and the radiative fading of relic
plasma within our previously proposed framework. The simultaneous visibility of two jet axes requires that the timescale for
spin evolution across zero, t_trans, be shorter than the fading timescale of relic
radio emission, t_fade. We estimate the transition timescale as t_trans about 5 million /lambda yr, where lambda is the Eddington ratio, and derive a visibility timescale t_fade about equal to 5-20 Myr based on the
evolution of the synchrotron break frequency for typical lobe
magnetic fields and
redshifts. This leads to a critical Eddington ratio lambda_crit in the range 0.3-1, above which systems can exhibit X-shaped morphologies. We show that this threshold naturally produces an environmental dependence, as radiatively efficient
accretion is more readily sustained in low-density environments, while feedback in rich clusters tends to drive systems toward radiatively inefficient states with a larger fraction of systems having lambda much less than lambda_crit, suppressing XRG formation. We further demonstrate that the observed low fraction of X-shaped
radio galaxies (about 1-5%) arises from the limited overlap window combined with
geometric and detectability effects. These results provide a quantitative and testable extension of our previous model, linking X-shaped morphology to
accretion rate and environmental conditions through a simple timescale criterion.
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General Relativity and Quantum Cosmology
Polytropic wormholes
Remo Garattini, Emmanuel N. Saridakis and Athanasios G. Tzikas
Traversable wormholes in general relativity require non-standard matter sources, making the identification of physically motivated equations of state particularly important. We investigate wormholes supported by a polytropic equation of state, considering homogeneous and inhomogeneous configurations within a unified framework. We derive the corresponding solutions and analyze the effects of the polytropic parameters on the geometry and energy conditions. In the homogeneous case, the polytropic construction yields a consistent wormhole interior whose geometry and matter content are governed by the constant polytropic parameters. For the inhomogeneous case, we obtain a general analytical expression showing that the geometry is completely determined by the radial polytropic coefficient $\omega(r)$. For positive $\omega(r)$, the requirement for physically meaningful solutions naturally restricts the polytropic exponent to odd integer values. Using a power-law profile, we construct explicit classes of solutions exhibiting distinct parameter regimes and finite radial support. Interestingly enough, for an exponent $\alpha=2\gamma-3$, a generalized absurdly benign traversable wormhole-like configuration emerges naturally. Although the
flare-out condition implies null-energy-condition violation at the throat, the inhomogeneous framework allows its radial distribution to be controlled. Our results establish a systematic connection between polytropic matter and wormhole geometry, providing a flexible framework for constructing compact wormholes with localized exotic matter.
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Computational Physics · Cross-listed from math.NA
Meshfree Snow Modelling using a Modified Cam-Clay Approach
Erik Schlesinger, Chaitanya Sanghavi, Jörg Kuhnert et al. (+2 more)
Snow is a complex geomaterial whose macroscopic response is governed by density, temperature, and the
topology of its evolving microstructure. Its mechanical behavior spans elastic, plastic, viscous, and failure dominated regimes, imposing significant challenges for numerical methods, which intends to simulate large deformations, evolving free surfaces, and complex boundary interactions. This work presents the first integration of a Modified Cam-Clay constitutive formulation for snow into a purely meshfree strong-form collocation framework based on the Generalized Finite Difference Method. The main methodological contribution is a numerical coupling that combines a global implicit mixed formulation for pressure and velocity with a constitutive return-mapping
algorithm. The hydrostatic pressure contribution is obtained from a Poisson equation and subsequently corrected through the Modified Cam-Clay return-mapping procedure, while the deviatoric response is treated semi-implicitly using a numerical viscosity formulation. This partitioned treatment of the volumetric and deviatoric stress contributions enables stable simulations with comparatively large time steps while producing smooth spatial pressure fields. As a result, forces on complex boundary geometries can be evaluated accurately. Numerical results of this coupling illustrate the algorithmic stability of the framework, the effective imposition of boundary conditions, and the suitability of local spatial refinement. The feasibility of applying the framework to vehicle-snow interaction through rigid-body coupling is also illustrated. The presented formulation provides a robust basis for future simulations of dynamic snow loading on vehicle structures.
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All authors Erik Schlesinger, Chaitanya Sanghavi, Jörg Kuhnert, Carsten Schilde, Pratik Suchde
Instrumentation and Methods for Astrophysics
TomoSphero: Fast Differentiable Projector for Planetary and Solar Tomography on Spherical Grids
Evan Widloski and Lara Waldrop
Computational
tomography is a tool for determining the internal structure of objects from a set of projections, typically taken along some regular path. In recent years, methods and GPU-accelerated libraries have emerged that allow for fast reconstruction from projections along more complicated paths. Most of these libraries rely on a Cartesian discretization of the object, which is not appropriate for all scenarios. We present TomoSphero, a differentiable tomographic projector over spherical grids which are often used in planetary and
solar tomography. TomoSphero is designed to be used as a building block in reconstruction
algorithms and includes common projection types such as cone-beam and parallel-beam, but is flexible enough to accommodate arbitrary projections. TomoSphero is implemented in PyTorch which allows for fast projection computation on GPUs, easy access to modern machine learning optimizers, and automatic differentiation for rapid prototyping of parametric models.
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Mathematical Physics · Cross-listed from math.DG
Inhomogeneous Einstein metrics on complex projective spaces
Gonzalo Cao-Labora and Alberto Rodríguez-Vázquez
The only Einstein metrics currently known on complex projective spaces are homogeneous: the Fubini-Study metric, arising via the
Hopf fibration; and, in odd complex dimensions, Ziller's metric, obtained as a canonical variation along the twistor fibration over the quaternionic projective space. In 1965, Berger proved that the Fubini-Study metric is the unique Kähler-Einstein metric on the complex projective space, and posed the question of whether other Einstein metrics exist. We construct the first inhomogeneous Einstein metrics on complex projective spaces of complex dimension $n$ for $3\leq n \leq 7$, answering Berger's question affirmatively for the complex even dimensional cases $n=4$ and $n=6$.
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Mathematical Physics · Cross-listed from math.CA
On the relations between several notions of symmetry for the second order linear differential equation
David Blázquez-Sanz and Santiago Alexis Aguirre Agudelo
There are several non-equivalent notions of infinitesimal
symmetry in the literature of second order linear differential equations: Lie point
symmetries, vertical (gauge)
symmetries, operator
symmetries, infinitesimal contact
symmetries, and Lie–Bäcklund operators. We construct an explicit correspondence among the first three, We then describe the Lie
algebra $\mathcal L_\Omega(\mathbb U)$ of infinitesimal contact transformations of the contact system $\Omega=\langle dy-y'\,dx\rangle$, with coefficients in a differential field $\U$ of functions of $x$ and $y$. We obtain a canonical decomposition $\mathcal L_\Omega(\mathbb U)=\prod_{k\ge0}\mathcal L_\Omega^k\mathbb U$ into $\mathbb C$-vector spaces, each parametrized by $\mathbb U$ (by $\mathbb U\oplus\mathbb U$ for $k=0$), and we compute the algebraic differential formulae for the Lie bracket in these coordinates. Applied to the
symmetry problem, we prove that a contact vector field with generating function $W$ is a
symmetry of if and only if $A^{2}W=aW+b\,AW$, where $A$ is the vector field in the jet space corresponding to the equation; equivalently, if and only if $W=F_1(u_1,u_2)\phi_1+F_2(u_1,u_2)\phi_2$ for arbitrary functions $F_1,F_2$ of the two first integrals of $A$ and a basis $\phi_1,\phi_2$ of solutions. The
symmetry algebra is always parametrized by two arbitrary functions of two variables. It also shows that the decomposition of $\Lom(\U)$ never captures the whole
symmetry algebra: for $a\neq0$ the graded part reduces to the point
symmetries, while for $y''=0$ it is an infinite dimensional but still proper subspace, and in neither case is it a Lie subalgebra. Finally we make precise the transformation law $W\mapsto\mu^{-1}(W\circ\varphi)$ for characteristics under a contact transformation with conformal factor $\mu$, which governs the transport of evolutionary representatives.
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Statistical Mechanics
Giant Thermal Amplification via Engineered Dissipation in a Sierpinski-Gasket Aharonov-Bohm Interferometer
Shubhra Shubhadarshini Mallick, Salil Bedkihal, Mattias Fitzpatrick et al. (+1 more)
We propose a three-terminal thermal amplifier based on a Sierpinski-gasket Aharonov-Bohm interferometer, where the third (base) terminal is realized as a floating Buttiker probe that acts as an engineered dissipative reservoir, exchanging energy with the conductor while carrying no net charge current. Using the nonequilibrium Green's function formalism, we demonstrate that the interplay of
quantum coherence and engineered dissipation gives rise to
giant,
magnetic-flux-controlled thermal amplification, whereas purely coherent transport exhibits little or no amplification. We show that the amplification originates from a flux-induced cancellation of the energy-resolved thermal response of the base terminal, causing its differential heat current to vanish while finite heat currents continue to flow through the emitter and collector terminals. As a result, the thermal gain diverges without requiring resonant transmission. This interference-driven cancellation gives rise to an emergent thermal transparency, closely analogous to electromagnetically induced transparency in optical systems, where destructive
quantum interference suppresses the thermal response of the base reservoir while maintaining finite heat transport through the remaining terminals. Our results establish the interplay of engineered dissipation and
quantum interference as a powerful mechanism for controlling heat flow and realizing high-performance thermal amplifiers in mesoscopic conductors.
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All authors Shubhra Shubhadarshini Mallick, Salil Bedkihal, Mattias Fitzpatrick, Malay Bandyopadhyay
High Energy Physics (Phenomenology)
Truncation of the Radial Ladder in Heavy Quarkonia
Wen-Xuan Zhang, Si-Qiang Luo and Xiang Liu
A fundamental open question in
hadron spectroscopy is whether the radial excitation ladder of quarkonia truncates at a finite level—a possibility that would challenge the conventional
quark-antiquark bound-state picture and offer decisive clues to the nonperturbative strong interaction. Taking advantage of the newly observed high-mass hadronic states, we address this issue by solving a screened Godfrey–Isgur
Hamiltonian for charmonium and bottomonium using the Gaussian expansion method. The calculated spectra saturate at $4.74\,\mathrm{GeV}$ ($c\bar{c}$) and $11.67\,\mathrm{GeV}$ ($b\bar{b}$), while root-mean-square radii grow to $\sim10\,\mathrm{fm}$—an order of magnitude above the confinement scale—where adjacent mass gaps drop below $10\,\mathrm{MeV}$. Combining a threshold-based mass-gap criterion, defined by the onset of mass–radius decoupling, with additional diagnostics, we locate the operational upper radial limits at $n\approx8$–$10$ for charmonium and $n\approx12$–$13$ for bottomonium. Beyond these limits, the conventional $q\bar{q}$ description ceases to apply. This work provides the first quantitative determination of these upper limits, and the proposed criterion is directly testable with forthcoming high-statistics data from BESIII, Belle II, and LHCb.
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Soft Condensed Matter
Size matters more than packing in bimodal colloidal gel compositions
Robert A. Campbell, Ziye Zhuang, Ali Mohraz et al. (+1 more)
Colloidal gels are frequently modeled as monodisperse particle networks, although practical formulations commonly contain particles with multiple characteristic sizes. Here, we use large-scale, hydrodynamically resolved simulations of colloidal depletion gels to isolate the effects of particle size and local packing in bimodal systems with a small-to-large size ratio of 1:2. Increasing the large-particle fraction introduces new heterotypic angular motifs and substantially increases the fraction of bonds participating in tetrahedral structures, with a maximum at intermediate composition. However, these additional rigid motifs do not reorganize into larger or more highly connected tetrahedral aggregates. The mean coordination and characteristic aggregate size remain nearly composition independent. By contrast, the void and cluster-size distributions coarsen systematically as the large-particle fraction increases. These mesoscale distributions largely collapse when normalized by a composition-dependent particle length scale, indicating that changes in composition primarily rescale gel architecture rather than producing distinct rigid-network
topologies. An elastic modulus estimated using Cauchy-Born theory similarly follows this effective length scale more closely than the abundance of local tetrahedral motifs. These results show that, for moderate size disparity, particle size controls the structural scale and predicted mechanical response of bimodal colloidal gels more strongly than enhanced local packing.
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All authors Robert A. Campbell, Ziye Zhuang, Ali Mohraz, Safa Jamali
Physics and Society · Cross-listed from cs.GT
The New Mathematics of Democracy
Bailey Flanigan and Ismar Volic
This article surveys emerging directions in the mathematics of democracy. It uses three case studies — voting theory, participatory budgeting, and deliberative democracy — to highlight how contemporary challenges motivate rigorous mathematical research that incorporates real-world data, institutional constraints, and implementation feasibility. Within each case, we highlight active and promising research frontiers, evidence of real-world impact, practical applications, and opportunities for getting involved.
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Fluid Dynamics
Volume-preserving Lagrangian averaging using polar factorization
Abhijeet Minz, Lois E. Baker and Jacques Vanneste
The generalised Lagrangian mean (GLM) theory of Andrews & McIntyre provides a powerful framework to study the interactions between waves and flows. A drawback of this theory is that the Lagrangian mean velocity is divergent even for incompressible fluids because the mean flow map, which sends the Lagrangian labels of fluid parcels to their mean positions, does not preserve volume. This results, for instance, in
vortices shrinking under Lagrangian averaging. We overcome this drawback by revising the definition of the mean flow map, choosing it as the volume-preserving map closest to the "bare" GLM mean map. A standard result of optimal-transport theory then shows that the new mean map is the volume-preserving factor in the polar factorization of the GLM mean map. We develop and implement a numerical method for the computation of the corresponding Lagrangian mean fields from simulation data. The implementation builds on recently developed
algorithms for the on-the-fly computation of Lagrangian means using the exponential and Butterworth filters. We demonstrate the value of volume-preserving Lagrangian averaging in simulations of the two-dimensional incompressible and shallow-water models. We compare the Lagrangian-mean fields obtained with and without the volume-preservation constraint.
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Quantum Physics · Cross-listed from cs.CC
Classical Adversarial Fault-Tolerance and PCPs
Anurag Anshu, Nikolas P. Breuckmann, Louis Golowich et al. (+2 more)
We show how to compile an arbitrary classical
circuit into a fault-tolerant
circuit, which performs the desired computation even when an almost-linear number of bits are adversarially chosen and corrupted in each timestep. Using a variant of this fault-tolerance scheme that only detects (rather than corrects) corruptions, we give a new construction of probabilistically checkable proofs (PCPs) for NP with polylogarithmic query complexity. This PCP construction from fault-tolerance presents a promising candidate for quantization by the work of Anshu, Breuckmann, and Nguyen (STOC'24), who provided a roadmap for constructing
quantum PCPs via fault-tolerance.
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All authors Anurag Anshu, Nikolas P. Breuckmann, Louis Golowich, Quynh T. Nguyen, Umesh Vazirani
Quantum Physics
Fault-Tolerant Quantum Computation with Adversarial Errors
Nikolas P. Breuckmann, Louis Golowich and Umesh Vazirani
We prove a fault-tolerance
theorem for
quantum computation against
adversarial noise. For every
quantum circuit on $\bar{N}$ logical qudits of depth $\bar{T}$, we construct a fault-tolerant
circuit on $N=\text{poly}(\bar{N})$ physical qudits of depth $\bar{T}\cdot\bar{N}^{o(1)}$, which is robust against an adversary who may arbitrarily choose and corrupt an almost-linear number $N^{1-o(1)}$ of physical qudits at each time step. This robustness significantly improves upon prior fault-tolerance
theorems, which assumed corruptions were either local and
stochastic, or else only act on a polynomially vanishing fraction of qudits. Our fault-tolerance scheme addresses a key bottleneck towards constructing
quantum PCPs via the
circuit-to-
Hamiltonian mapping of Anshu, Breuckmann, and Nguyen (STOC'24). More fundamentally, our result demonstrates that fault-tolerant
quantum computation remains possible under noise models that are global, worst-case, and non-Markovian over the full duration of the computation, directly countering concerns that correlated noise could fundamentally undermine
quantum fault tolerance. Our construction is based on a new family of subsystem product codes we develop, which have large dimension and distance along with low-weight parity-checks, and which support transversal non-Clifford gates. We show how to perform single-shot fault-tolerant error correction on these codes using a Floquet-like procedure based on the local testability of classical tensor codes. We then obtain a universal fault-tolerance scheme using repeated code switching in a hypercubic qudit architecture. Finally, we recursively compose our scheme with itself to reduce an initially exponential qudit dimension down to a constant.
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Disordered Systems and Neural Networks
Spectral Edge Rigidity of Quantum Chaotic States
Joaquim Telles de Miranda and Tobias Micklitz
We determine the distribution of fidelity susceptibility for chaotic eigenstates at the spectral edge of Gaussian random-
matrix ensembles. Previous work showed that, in the
unitary class, the characteristic susceptibility scale of edge states grows as $D^{1/3}$, rather than proportionally to $D$ as in the spectral bulk, reflecting Airy-edge level
rigidity. Extending a determinant-based framework introduced for bulk states, we derive the universal edge distributions for both the orthogonal and
unitary ensembles. The two
symmetry classes share the scaling variable $g/D^{1/3}$ and exhibit a
symmetry-dependent cubic suppression of small susceptibilities, while their algebraic large-$g$ tails reflect the corresponding
symmetry-dependent level repulsion. Although eigenvector statistics retain their random-
matrix form throughout the spectrum, edge
rigidity makes low-lying chaotic states parametrically less sensitive to generic perturbations than bulk states. Our results establish universal,
symmetry-dependent spectral-edge fidelity-susceptibility statistics in systems whose chaotic dynamics extends down to the ground state.
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High Energy Astrophysical Phenomena
The first comprehensive spectral and timing study of the ultra-compact X-ray binary 4U 1812-12 with NICER and NuSTAR
Swarnendu Jana, Aditya S. Mondal, Aru Beri et al. (+1 more)
The source 4U 1812-12 is a persistent, weakly variable low-mass X-ray binary containing a
neutron star. The source was observed by NICER between 2019 and 2021 and, more recently, by NuSTAR in 2025. During the NICER and NuSTAR observations, the source was detected in a hard spectral state with a bolometric luminosity of $\sim 1.90\times 10^{36}$ ergs s$^{-1}$. Its $3-70$ keV NuSTAR spectrum is characterized by a soft thermal emission from the disc, a hard Comptonized emission from the corona, and its reflection from the
accretion disc. The NuSTAR energy spectrum exhibits the clear presence of disc reflection features, fitted using a self-consistent relativistic reflection model relxill. Our reflection modeling indicates a moderately ionized
accretion disc (log\:$\xi\sim2.72$) extending close to the
neutron star surface ($R_{in}\lesssim 1.72\:R_{ISCO}$), and viewed through a small inclination angle ($i\sim 25$ degrees). Assuming that the
magnetic field ($B$) truncates the disc, we found $B\lesssim 2.54\times 10^{8}$ G, comparable to the typical values observed for NS LMXBs. The $1.0-9.5$ keV NICER spectra are also characterized by a soft thermal component and a dominant hard Comptonized component. During NICER observations, the disc temperature exhibits a small variation within $\sim 0.69-0.84$ keV. In contrast, the power law
photon index, $\Gamma$, exhibits a large variation of $\sim 0.8-1.5$, implying a substantial change in the Comptonized emission. Moreover, NICER timing analysis reveals broadband aperiodic variability with significant QPO-like features at $0.379\pm 0.008$ Hz and $0.724\pm 0.025$ Hz, having fractional rms amplitudes of $2.9\pm 0.6\%$ and $4.1\pm 0.5\%$, respectively.
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All authors Swarnendu Jana, Aditya S. Mondal, Aru Beri, Gulab C. Dewangan
Quantum Physics
Global Minimax Readout of a Qubit Direction
Abbas Taherpour, Amirhossein Taherpour and Tamer Khattab
We determine the exact worst-direction Fisher-information cost of using a parameter-independent readout to estimate an unknown
qubit direction at known Bloch-vector length $\eta$. Every fixed-local architecture, including recorded classical randomization, heterogeneous single-copy measurements, and arbitrary outcome spaces, reduces exactly to a zero-barycenter probability measure on the Bloch ball. For every full-rank
qubit and every trace-balanced spectral Fisher loss, the resulting minimax problem is rigid: the unique optimal aggregate design is the
spin-coherent Haar positive-operator-valued measure (POVM). For $N$ copies, inverse-Fisher $A$ loss has the exact value $2/[Nf(\eta)]$, where $ f(\eta)= \frac{2\eta-(1-\eta^2)\log[(1+\eta)/(1-\eta)]}{4\eta}$. This uniqueness has an immediate finite-readout consequence. No finite-support measurement attains the unrestricted mixed-state optimum, while at the smallest globally regular support the tetrahedral symmetric informationally complete (SIC) measurement is uniquely $A$- and $D$-minimax, with exact worst-direction values. Relaxing the fixed-readout constraint separates the asymptotic resources: one-way local operations and classical communication (LOCC), unrestricted LOCC, and separable measurements have $A$-loss coefficient $4/\eta^2$, whereas collective measurements attain $2(1+\eta)/\eta^2$. We further classify the
rigidity conditions for unequal contrasts and show that Haar uniqueness survives at the nonregular pure-state endpoint.
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Quantum Physics
Classical-limit formula for matrix elements between bound states of distinct one-dimensional potentials
K. Beloy
A classical-limit formula is derived for
matrix elements between bound states of distinct one-dimensional potentials. We leave open the physical interpretation of the potentials, but generally envision them to be Born-Oppenheimer-type potentials with the position variable $x$ identifying with a slowly evolving degree of freedom of the system. For instance, $x$ could represent the internuclear separation in a diatomic molecule, with the potentials being potential energy curves for different electronic states. In this scenario, the
matrix elements could be, e.g., conventional Franck-Condon factors. To test the derived formula, we assume functional forms for the potentials and operator that afford analytical solutions for the
matrix elements. As the classical limit is approached, the computed
matrix elements exhibit a clear tendency towards the classical-limit formula, providing strong validation for the formula. In future work, we anticipate using the formula to model inhomogeneous excitation spectra of atoms in one-dimensional optical
lattices, with an eye towards improved optical
lattice clock performance.
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