Cosmology and Nongalactic Astrophysics
Cooling, conduction, and compact objects: Gravothermal evolution of dissipative self-interacting dark matter halos
Ludwig D. Schmidt, Moritz S. Fischer and Mathias Garny
Many proposed self-interacting dark matter (SIDM) models yield radiative processes that can dissipate energy. Understanding their impact on astrophysical objects through simulations and comparing the results with observations may thus constrain SIDM models. We systematically investigated how dissipation alters the gravothermal
evolution of isolated SIDM
halos by independently varying dissipation and heat conduction and identified potential observational signatures. We present the first extension of the $N$-body formalism for frequent small-angle self-interactions to include effective dissipation. We compared all results for isolated
halos with a dissipative gravothermal fluid model to assess the validity and limitations of the latter. We find that dissipation qualitatively changes the gravothermal
evolution of SIDM
halos beyond simply accelerating collapse. Sufficiently strong central cooling can invert the usual role of heat conduction: the formation of an isothermal core is suppressed such that conduction remains directed inward throughout the
evolution. Outer
halo regions beyond the scale radius can cool efficiently rather than being heated by conduction, resulting in a larger region of mass infall and a less pronounced indentation between the core and the outer
halo in the final density profile. These effects depend strongly on the cooling rate but are comparatively insensitive to the angular dependence of the self-interaction cross section. We further show that weakly dissipative self-interactions can explain the properties of the recently observed strong lens perturber in JVAS B1938+666 with significantly shorter
evolution times or, equivalently, smaller cross sections compared to the elastic case. Our results open a new route to connecting
halo structure and recently reported compact objects to dark-sector microphysics.
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Cosmology and Nongalactic Astrophysics
Physics-guided discovery of dynamical dark-energy equations of state through iterative AI reasoning
Clecio R. Bom, Bernardo M. Fraga, Miguel A. Sabogal et al. (+3 more)
Phenomenological model building has traditionally relied on human
reasoning: equations are proposed from theoretical intuition, analogy, or empirical convenience, and only then tested against data. Here we show that this cycle can be recast as an iterative AI
reasoning process for dynamical dark energy. Our framework uses a large
language model to propose equations of state together with cosmological rationales, grounded by
retrieval from the dark-energy literature and refined through autonomous evaluation. Each candidate is embedded in a cosmological model, optimized against observations, and assessed using likelihood performance and theoretical consistency. An independent
language-model critic scores the physical motivation, novelty, clarity, stability and implementation validity of both the equation and its rationale, allowing subsequent proposals to evolve jointly in mathematical structure and physical
reasoning. Applied to cosmological data combinations including
supernovae,
baryon acoustic oscillations and Planck likelihoods, the framework identifies two parameterizations that, to the best of our knowledge, have not previously been explored and that are competitive with established forms. For Pantheon+
supernovae, DESI DR2
baryon acoustic oscillations and the full Planck 2018 temperature, polarization, and
lensing likelihoods, the best AI-selected model attains larger
Bayesian evidence than the traditional parameterizations considered here by more than one unit. These results show that AI-guided
reasoning can complement physical model building by proposing and evaluating interpretable phenomenological parameterizations for dynamical dark energy.
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All authors Clecio R. Bom, Bernardo M. Fraga, Miguel A. Sabogal, Armando Bernui, Phelipe Darc, Gustavo Schwarz
Strongly Correlated Electrons
Three-dimensional Foliated Fractional Quantum Hall Phases
Sahana Das, Navketan Batra, Andrea Kouta Dagnino et al. (+4 more)
Foliated topological orders in three dimensions are layered systems in which anyons are free to move within a layer but cannot hop between them. A simple model with such a phase is a stack of decoupled two-dimensional electron gases in a strong
magnetic field, each in the same fractional
quantum Hall state. By focusing on the case of filling $\nu=1/3$ of the lowest Landau level in each layer, we show that (i) the limit of decoupled Laughlin states is stable upon introducing interlayer interactions and (ii) the system can enter a spontaneously layer-trimerized foliated non-Abelian Fibonacci phase. We support our claims by numerical exact diagonalization of up to 10 layers as well as perturbative analytical calculations. Specifically, we show that the foliated Fibonacci phase exists in the 9-layer system with pseudopotential interactions within and between neighboring layers. We identify the phase via quasihole counting and by calculating the overlap with a model wave function which we derive from the associated conformal field theory. Our numerical results suggest the possibility of realizing these phases in layered van der Waals
crystals in strong
magnetic fields, as well as in multilayer
heterostructures.
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All authors Sahana Das, Navketan Batra, Andrea Kouta Dagnino, Dan Mao, Nicolas Regnault, Glenn Wagner, Titus Neupert
High Energy Physics (Phenomenology)
LeWRON: Agentic Analysis of Electroweak Phase Transitions
Isaac R. Wang
The electroweak phase transition (EWPT) is a central topic in particle physics and cosmology, connecting
collider phenomenology, baryogenesis, and gravitational-wave observatories. Its analysis requires a technically demanding, convention-sensitive, and model-dependent pipeline, from constructing the finite-temperature effective potential to tracking thermal histories, computing bubble nucleation rates, and predicting gravitational-wave spectra. We present LeWRON (Learning ElectroWeak phase tRansitiON), an agentic framework that orchestrates this pipeline starting from an input Lagrangian. LeWRON combines audited toolbox construction with an Explorer module that uses the generated model-specific code for further analysis, including scans and plots. Intermediate analytic outputs are checked by auditor
agents and stored as structured artifacts, enabling reproducible human inspection and downstream use through both a command-line interface and a public Python API. The framework supports a reproduction mode, which infers conventions from the literature and reproduces published results, and a discovery mode, which guides users through structured checkpoints for new models. We demonstrate LeWRON across representative beyond-the-Standard-Model scenarios and release the code on GitHub.
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Instrumentation and Methods for Astrophysics
Characterization of a symmetric-facet dual-ruled grating for spatial heterodyne spectroscopy
Cole Meyer, Joanne Flores, Jason Corliss et al. (+1 more)
Dual-bandpass spatial heterodyne spectrometers (DB-SHS) enable simultaneous high-resolution measurements of widely separated passbands, providing powerful diagnostics of astrophysical and planetary environments. However, DB-SHS instruments require a single incident beam to span two adjacent diffraction gratings with distinct ruling densities and blaze angles, resulting in a large gap between ruled sections that reduces throughput. Dual-ruled gratings solve this problem by integrating multiple ruled panels onto a single substrate, minimizing the dead space between ruled sections. We present experimental validation of a first-generation symmetric-facet dual-ruled grating manufactured by Bach Research, mechanically ruled at $800$ and $\mathrm{2000\;gr\;mm^{-1}}$ with a $13.8^\circ$ blaze angle. Using a stabilized deuterium source alongside a Czerny-Turner monochromator, we measured diffraction efficiencies into the $m = 0, \pm1, \pm2$ orders from $200$ to $\mathrm{700\;nm}$. We compare these results with theoretical predictions from rigorous coupled-wave analysis (RCWA), inferring a facet asymmetry of $\lesssim1^\circ$ and $\sim70\%$ facet duty cycle indicative of minor manufacturing defects. This work demonstrates the viability of mechanically ruled, symmetric-facet, dual-ruled gratings and lays the foundation for laboratory validation of the first DB-SHS, ultimately enabling high-resolution spectroscopy of distinct spectral regions relevant to astrophysical and planetary remote sensing.
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All authors Cole Meyer, Joanne Flores, Jason Corliss, Walter Harris
High Energy Physics (Theory)
Calabi-Yau Orientifold Hypersurfaces and their F-theory Uplifts
Bjoern Hassfeld and Jakob Moritz
We present an
algorithm that constructs Calabi-Yau threefold orientifolds and their $F$-theory uplifts to elliptically-fibered Calabi-Yau fourfolds, embedded in toric varieties at codimension one and two respectively. The resulting Calabi-Yau fourfolds arise from triangulations of $6d$ reflexive polytopes – which our method constructs from orientifold data – and are smooth away from isolated terminal singularities. For many of our fourfolds, the construction of the mirror
manifold is immediate, enabling the computation of fourfold periods, and thus the seven-brane superpotential. We present multiple examples that demonstrate these capabilities. Our
algorithms work with $\mathtt{CYTools}$ and are available through a GitHub repository.
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Solar and Stellar Astrophysics
Steady-state Stellar Winds Driven by Recombination
Eritas Yang and Eliot Quataert
Hydrogen and helium recombination energy has been proposed as a potential driver of mass ejection in common-envelope
evolution and other eruptive
stellar phenomena. We investigate whether recombination can by itself launch a steady, transonic wind from near a
stellar surface. Using a tabulated equation of state, we explore steady-state, adiabatic wind solutions over a broad range of
stellar mass, density, and temperature. We classify a wind as recombination-driven only if the gas is gravitationally bound prior to recombination and if the released energy remains trapped until the flow becomes unbound. Only a small fraction of the solutions satisfy both conditions. In most cases, the gas is either already unbound without recombination or loses the released energy through radiative
diffusion while still bound. The subset of valid solutions require
outflow velocities $\gtrsim 10\,{\rm km\,s^{-1}}$ at $10\,R_\odot$, inconsistent with a wind launched from a hydrostatic
star. We conclude that recombination energy alone is unlikely to produce steady
stellar winds. It can, however, accelerate and unbind a pre-existing
outflow generated by processes such as binary orbital decay, producing mass-loss rates of $\sim \rm M_\odot\,yr^{-1}$.
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Superconductivity
Electrical magnetochiral anisotropy in Rashba superconductors
Joaquim Telles de Miranda, Maxim Khodas and Alex Levchenko
We theoretically investigate the role of higher-order Lifshitz invariants in nonreciprocal charge transport in two-dimensional noncentrosymmetric
superconductors with Rashba
spin-orbit coupling. In the superconducting state, these
symmetry-allowed terms give rise to critical-current nonreciprocity, while in the normal state near the superconducting transition they generate a pronounced magnetochiral anisotropy. Using
symmetry-constrained group-theoretical methods, we systematically construct the allowed Lifshitz invariants and derive the corresponding vector structure of the nonreciprocal current. To describe nonlinear transport in the fluctuation regime, we apply a generalized time-dependent Ginzburg-Landau theory that incorporates both the Aslamazov-Larkin contribution from fluctuation-induced Cooper pairs and the Maki-Thompson contribution associated with
quantum interference in the Cooper channel. We further analyze the effects of disorder scattering and dephasing on the resulting nonreciprocal response.
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High Energy Physics (Theory)
Bootstrapping Pion Form Factors at Large $N$
Jan Albert, Dilara Kosva and Leonardo Rastelli
We initiate a bootstrap study of pion form factors in large $N$ QCD. We consider the mixed system of the vector-current two-point function, the pion vector form factor, and the pion scattering amplitude in the
chiral limit. At large $N$ these observables are meromorphic, with spectral data constrained by unitarity, crossing
symmetry, and Regge boundedness. We obtain bounds of two kinds. The first are rigorous and universal: from analyticity, unitarity and the asymptotic Brodsky-Farrar scaling, we constrain low-energy form-factor coefficients. The second are more phenomenological, of the Shifman-Vainshtein-Zakharov type: feeding in the perturbative ultraviolet behavior at a finite scale lets us bound the pion decay constant, convert a large $N$
lattice measurement into a lower bound on the scale at which asymptotic freedom sets in, and constrain the pion charge radius. Combining these inputs, the space of allowed
chiral Lagrangians shrinks toward the region where large $N$ QCD is expected to sit. Our results illustrate how local gauge-invariant probes provide a canonical bridge between the hadronic bootstrap and the microscopic QCD Lagrangian.
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Soft Condensed Matter
Sequential replica exchange with solute tempering for atomistic modeling of supramolecular polymer structures
Hadi H. Arefi and Takeshi Yamamoto
Predicting detailed atomistic structures of self-assembling systems remains a challenge for all-atom molecular dynamics simulations. Replica exchange with solute tempering (REST) has been used to study those systems by accelerating all monomers in a global and uniform manner. While such a global approach can in principle predict any morphology of the system, it has computational drawbacks such as inefficient replica traversal due to order-disorder transitions and the growing number of replicas with system size. To address these issues, here we propose an alternative, stepwise construction approach to modeling supramolecular
polymers under the assumption of one-dimensional polymerization. Specifically, we generate
polymer structures by adding new monomers one by one to the system and applying REST to the new monomers to find their optimal binding positions based on an energy-based scoring function. The monomer addition and enhanced sampling are repeated sequentially until a
polymer of desired length is obtained. We test the above procedure using a model supramolecular
polymer in explicit solvent, and show that it can generate a
polymer structure with characteristic H-bonding patterns at reduced computational costs, while also improving the efficiency of replica traversal significantly. We thus expect that the sequential REST will be useful for modeling supramolecular
polymers, particularly for cases where global REST simulations are too demanding computationally.
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Statistical Mechanics
Spectra as a classical phenomenon, and the Einstein classical program
Andrea Carati, Luigi Galgani and Fabrizio Gangemi
According to Born (Atomic Physics, page 103), spectra are “
quantum phenomena, which from a classical standpoint are perfectly unintelligible”. However we illustrate results on classical calculations of infrared spectra of ionic
crystals (actually LiF) which show that the situation is much more complex. Indeed it turns out that: 1) At room temperature and at higher ones (up to 1060 K) the classical computations reproduce the experimental data, even better than the presently available
quantum ones do; 2) At lower temperatures (even at 7.5 K), the classical computations reproduce pretty well the data, if one accepts the idea advanced in 1916 by Nernst (the inventor of the third principle) that zero-point energy has room in classical physics too. It is eventually pointed out that the mentioned results might be regarded as a first step towards an implementation of the Einstein Classical Program, which aims at deducing
quantum physics (admittedly the correct theory) from a realistic theory. In fact, we are considering the Einstein classical program in the extreme version in which the realistic theory is just (essentially, see below) classical electrodynamics of matter in bulk, involving phase space orbits, solutions of Newton equations. An Appendix is devoted to illustrate the Nernst approach, which concerns also the relation between equipartition and Planck's law.
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High Energy Astrophysical Phenomena
Scintillation of the first-known pulsar planetary system
J. M. Yao, L. Zhang, A. Wolszczan et al. (+8 more)
We present a scintillation study of the first-known
pulsar planetary system, PSR~B1257+12, using the Five-hundred-meter Aperture Spherical
radio Telescope (FAST). A total of 31 observations with durations greater than or equal to 30 minutes were analyzed. For 14 longer observations (greater than or equal to 120 minutes), one-dimensional autocorrelation function analyses yielded the scintillation timescale, scintillation bandwidth, and frequency-drift rate for 12 epochs. Two observations show strong periodic modulation in the frequency-domain auto-correlation function, likely caused by astronomical-unit-scale structures along the propagation path, preventing reliable measurements of the scintillation timescale and bandwidth. In three observations, secondary spectra reveal simultaneous detections of inner, middle, and outer arcs. Analysis of the annual modulation of the inner-arc
curvature indicates isotropic scattering, with a screen distance of $233\pm28$~pc and transverse velocity $V_{\rm scr,\alpha}=-7.16\pm2.16$ km~s$^{-1}$, $V_{\rm scr,\delta}=-41.07\pm5.69$ km~s$^{-1}$. Delay-profile analysis for both the inner and outer arcs suggest spectral exponents consistent with, or smaller than, the Kolmogorov value. Under isotropic scattering, the screen–
pulsar distances are $354\pm22$~pc and $166\pm12$~pc for the middle and outer arcs. Combining the results from long-term timing analyses with our scintillation measurements, we find that the dispersion measure (DM) variations are primarily dominated by
plasma located further away from the
pulsar. The low DM-change rate of the outer arc and the absence of nearby scattering screens suggest that the immediate environment of the
pulsar may be relatively clean. Alternatively, scattering screens closer to the
pulsar may exist but remain undetected, requiring higher-sensitivity or longer-duration observations.
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All authors J. M. Yao, L. Zhang, A. Wolszczan, William A. Coles, D. Li, Richard N. Manchester, N. Wang, C. H. Niu, P. Wang, F. F. Kou, J. P. Yuan
High Energy Physics (Phenomenology)
Emergent Gauge Symmetries in Particle Physics and Cosmology
Steven D. Bass
Where do gauge
symmetries come from? These lectures develop the idea that the Standard Model might be emergent, with its gauge
symmetries dissolving in some phase transition deep in the ultraviolet. The (meta-)stability of the
Higgs vacuum may be pointing to some new critical phenomena at very high energy scales, with the
Higgs connecting physics at LHC laboratory energies to that in the deep ultraviolet. In the emergence scenario, the dark energy scale comes out similar to the size of light Majorana
neutrino masses. These two quantities appear at the same order in a low energy expansion in inverse powers of the scale of emergence, about $10^{16}$ GeV. Dark matter candidates include
axions and
phonon like excitations of degrees of freedom above the scale of emergence. Possible tests of these ideas involve
neutrinos as well as gravitational-waves-related signals from the early Universe, which are sensitive to physics at very high energy scales.
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General Physics
Cosmic Structure Formation in a Viable Power-Law f(R) Gravity Model: Growth Dynamics, Stability, and Observational Signatures
Murli Manohar Verma
We investigate the
evolution of
cosmic structures in the power-law modified
gravity model $f(R)=R+R^{1+\delta}/R_c^\delta$, where the dimensionless parameter $\delta$ characterizes deviations from General Relativity. The background cosmological dynamics and the
evolution of linear matter density perturbations are studied within the framework of metric $f(R)$
gravity. The modified perturbation equation is derived by introducing an effective gravitational coupling associated with the additional scalar degree of freedom, and the
evolution of the growth factor, logarithmic growth rate, growth index, and the observable quantity $f\sigma_8(z)$ are investigated. The results show that the
curvature correction enhances the growth of matter perturbations while remaining compatible with the observed late-time accelerated expansion for suitable values of the model parameter. The theoretical viability of the model is established through the ghost-free condition, Dolgov–Kawasaki stability criterion, positive scalaron mass, stable de Sitter solution, and chameleon screening mechanism. Comparison with representative viable $f(R)$
gravity models shows that the present theory achieves a consistent cosmological
evolution with a single deviation parameter. The predicted modifications in the growth of structures and the effective gravitational coupling provide observable signatures that can be tested by forthcoming large-scale structure and weak-
lensing surveys, providing a means to test
curvature-induced modifications of
gravity.
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Instrumentation and Detectors
The Silicon Tracking System of the E16 experiment at J-PARC: construction, installation and commissioning in beam test experiments
Dairon Rodríguez Garcés, Rento Yamada, Kazuya Aoki et al. (+37 more)
The J-PARC E16 experiment aims to search for signatures of
chiral symmetry restoration. It studies in-medium modifications of vector
mesons that decay via the dielectron channel. The measurements use a high-intensity 30 GeV
proton beam with C and Cu targets at rates up to 10 MHz. To achieve this, the experiment upgrades its tracking, by introducing innermost detector modules constructed with the same technology and procedures as the modules of the Silicon Tracking System (STS) of the Compressed Baryonic Matter (CBM) experiment at Facility for Antiproton and Ion Research (FAIR). A total of 15 modules were assembled, tested, characterized and then installed in the E16 detector setup. The detector was commissioned in a beam test experiment at Tsukuba, where the detector modules could be exposed to a 3 GeV electron beam. In preparation for the beam test the modules were characterized and calibrated, and performance studies were accomplished to assess the quality of the setup. During beamtime, three modules were operated and illuminated in two planes by the electron beam. This paper presents the results of the construction, characterization, commissioning, and operation of the E16-STS modules in beam test experiments.
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All authors Dairon Rodríguez Garcés, Rento Yamada, Kazuya Aoki, Lady Maryann Collazo Sánchez, David Emschermann, Hideto En'yo, Jürgen Eschke, Ulrich Frankenfeld, David Gutiérrez Menéndez, Johann M. Heuser, Masaya Ichikawa, Ralf Kapell, Irakli Keshelashvili, Jörg Lehnert, Tomoki Murakami, Shunnosuke Nagafusa, Wataru Nakai, Satomi Nakasuga, Megumi Naruki, Frederike Nickels, Shuta Ochiai, Kyoichiro Ozawa, Darío Alberto Ramírez Zaldívar, Adrian Rodríguez Rodríguez, Katia Santos Marrero, Christian Joachim Schmidt, Hans Rudolf Schmidt, Kerstin Schuenemann, Patryk Semeniuk, Mehulkumar Shiroya, Carmen Simons, Sindhu Subramanya, Oleksandr Suddia, Tomonori Takahashi, Maksym Teklishyn, Alberica Toia, Oleg Vasylyev, Robert Visinka, Yorito Yamaguchi, Wojciech Zabolotny
Quantum Physics
Ben Blain, Giampiero Marchegiani, Luigi Amico et al. (+1 more)
Superconducting
qubits are artificial atoms whose spectra and interactions can be engineered through appropriate
circuit design, a versatility that can be exploited for
quantum simulation. We theoretically investigate a linear array of capacitively coupled transmons, effectively described by a Bose-Hubbard
Hamiltonian with attractive interaction. We revisit the discrete-
soliton nature of the lowest-energy band of the spectrum, and identify spatially localized
quantum solitons. The solitonic character of these states is revealed through their time
evolution, which displays a
quantum interference pattern, or
quantum walk, highlighting their composite nature. We discuss protocols for preparing spatially localized
quantum solitons that are compatible with current state-of-the-art tunable-transmon
circuits. Our results demonstrate that superconducting
circuits provide a promising and experimentally accessible platform for the investigation of
quantum soliton physics.
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All authors Ben Blain, Giampiero Marchegiani, Luigi Amico, Gianluigi Catelani
Cosmology and Nongalactic Astrophysics
Constraints on Cosmic Strings from the Curl-Mode CMB Lensing Power Spectrum measured by ACT DR6
A. I. Lonappan, K. Ramesh, T. Namikawa et al. (+2 more)
A network of
cosmic strings is one of the few well-motivated cosmological sources of vector and tensor metric perturbations on the largest observable scales. Such perturbations imprint a characteristic curl component in the deflection angle of
cosmic microwave background (CMB)
photons that, unlike the scalar
lensing potential, vanishes for adiabatic density fluctuations at linear order. We exploit the curl-mode
lensing reconstruction released as part of the Atacama Cosmology
Telescope (ACT) Data Release~6 (DR6), based on five seasons of temperature and polarization data covering $9400~\mathrm{deg}^2$ of sky, to set new constraints on the dimensionless string tension $G\mu$ and the inter-commutation (reconnection) probability $P$. Modelling the string-induced curl power spectrum within the velocity-dependent one-scale framework, we obtain a $2\sigma$ upper bound on the combination $G\mu P^{-1}\le 3.5\times 10^{-5}$ in the small-$P$ regime, and $G\mu \le 5.0\times 10^{-5}$ at $2\sigma$ assuming the canonical Nambu-Goto value $P=1$. Combining the ACT DR6 curl bandpowers with the Planck 2013 curl-mode reconstruction, which extends down to $L_{\rm min}=2$, tightens these bounds to $G\mu P^{-1}\le 3.2\times 10^{-5}$ and $G\mu\le 4.3\times 10^{-5}$ ($2\sigma$). These represent the tightest constraints on
cosmic strings derived from the curl-mode CMB
lensing power spectrum to date. Using the ACT data alone, compared to the ACT 2008-season analysis, the ACT DR6 constraint on $G\mu P^{-1}$ is nearly an order of magnitude tighter.
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All authors A. I. Lonappan, K. Ramesh, T. Namikawa, F. J. Qu, B. Keating
Solar and Stellar Astrophysics
Fine-scale downflows above flare ribbons captured by Solar Orbiter/EUI
Zheng Sun, Alexander G.M. Pietrow, Malcolm K. Druett et al. (+8 more)
In
solar flares,
flare ribbons map chromospheric footpoints where
flare energy deposition occurs. These locations are associated with field aligned energy transport from the corona that results from energy liberated during
magnetic reconnection. Recent chromospheric observations in the H$\alpha$ and H$\beta$ bands have revealed fine-scale downflow structures above
flare ribbons, referred to as riblets. In this study, we identify similar downflow structures in the extreme-ultraviolet (EUV) wavelength using high-resolution observations from
Solar Orbiter/EUI. These fine-scale downflows appear as downward-propagating, bright, and thread-like structures. They exhibit typical velocities of $\sim100~\mathrm{km\ s^{-1}}$, lifetimes of $\sim15$~s, and lengths of $\sim1.6$~Mm. Based on their morphological and dynamical properties, we interpret these observed downflows as the EUV counterparts of the riblets that have previously been reported from chromospheric observations. This study presents EUV imaging of $\sim 10^6$~K downflows above
flare ribbons. We interpret these downflows as a result of (1) the energisation and subsequent compression of pre-existing chromospheric fibrils due to particle beams or (2) adiabatic or shock-driven compression induced by the downward-propagating
plasma from the corona. These fine-scale EUV riblets provide a new diagnostic tool for probing the dynamics of
magnetic reconnection as well as energy transport and deposition during
solar flares.
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All authors Zheng Sun, Alexander G.M. Pietrow, Malcolm K. Druett, Hui Tian, Julián D. Alvarado-Gómez, Song Tan, Alexander Warmuth, Jiasheng Wang, Yuhang Gao, Zhenyong Hou, Alexandros Stork
Statistical Mechanics
Topological spectral form factor reveals emergent non-Hermitian single-particle $\mathcal{PT}$ transitions from many-body quantum chaos
Daniel Harkin, Chun Y. Leung and Amos Chan
In
equilibrium, topological defect insertions in
quantum and classical partition functions provide non-perturbative probes of phase transitions beyond local observables. In non-
equilibrium physics, the spectral form factor provides a minimal probe of universal
quantum dynamics and is a product of two partition functions at imaginary inverse temperature. We define the topological spectral form factor (TopSFF) by inserting topological defects acting non-trivially on the doubled partition functions, producing mismatched spacetime world-sheet
topologies. For the minimal $\mathbb{Z}_2$ spatially extended defect, implemented by the global swap operator, we derive an exact mapping of the TopSFF of a generic $(1+1)$D many-body chaotic system to an emergent $(3+1)$D non-Hermitian single-particle problem describing a temporal domain wall (tDW). We show analytically that the effective tDW dynamics undergoes a $\mathcal{PT}$
symmetry breaking transition at finite interaction strength $\epsilon_{\mathrm{EP}}$: below $\epsilon_{\mathrm{EP}}$, the leading modes are polarized into Gaussian or non-Gaussian tDW sectors and the TopSFF varies monotonically and exponentially with system size; above $\epsilon_{\mathrm{EP}}$, the tDW sectors hybridize and the TopSFF oscillates with system size; at the exceptional point $\epsilon_{\mathrm{EP}}$, Jordan non-diagonality produces a linear-in-system-size enhancement. For minimal temporally extended topological defects associated with global swap or time translation, we derive exact universal TopSFF free-energy scaling forms. We verify these signatures numerically in independent models.
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Quantum Physics
Floquet framework for driven polar quantum systems
Viktor Novičenko, Piotr Gładysz, Karolina Słowik et al. (+1 more)
We present an analytical and numerical Floquet treatment of a driven polar two-level
quantum system characterized by both longitudinal and transverse coupling to a periodic field. Analytically, we derive a dressed-frame effective
Hamiltonian up to first order in the inverse driving frequency, incorporating the longitudinal coupling nonperturbatively. This yields closed expressions for the effective transverse coupling strength and the effective detuning, both of which are modified by the presence of the longitudinal interaction. In the nonpolar limit, these expressions recover the usual near-resonant Rabi coupling and the Bloch-Siegert shift. As a second main result, we develop a numerical flow-equation framework that yields a time-independent effective
Hamiltonian across a broad range of transverse and longitudinal coupling strengths. This dual framework is relevant for a variety of platforms, including driven polar
quantum systems, optical
lattices, superconducting
circuits, and solids subject to surface acoustic waves.
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All authors Viktor Novičenko, Piotr Gładysz, Karolina Słowik, Egidijus Anisimovas
Instrumentation and Methods for Astrophysics
The Chandra-Gaia Catalog of Counterparts: Resolving ambiguous Gaia matches to X-ray sources in the Chandra Source Catalog using Machine Learning
V. Samuel Pérez-Díaz, Vinay L. Kashyap, Joshua D. Ingram et al. (+6 more)
We present a framework to cross-match sources from the Chandra Source Catalog (CSC v2.1) with optical sources from
Gaia Data Release 3. Unlike purely spatial approaches, we use source properties such as magnitudes, colors, and distances to identify true counterparts, detect chance coincidences, and resolve ambiguities when multiple plausible candidates exist. We define a training set of high-confidence matches using NWAY, a
Bayesian cross-matching framework that accounts for positional errors and source densities. We train a gradient-boosted classifier (LightGBM) on a variety of features from both catalogs. Of the ~$254$k unique X-ray sources, we find counterparts for ~$113$k sources, of which plausible multiple counterparts are found for ~$7$k. We find no counterparts for ~$20$k sources for which separation-based cross-matching does find a match, and attribute half of these to chance coincidences. We validate the pipeline on the Chandra Orion Ultradeep Project (COUP), where the machine-learning matches reproduce 95% of NWAY cross-matches without using any positional information. We release a catalog of the ~$113$k Chandra-
Gaia counterparts, together with ~$7$k alternative matches and ~$20$k ambiguous NWAY associations, supporting future population studies of sources detectable by both Chandra and
Gaia. We discuss limitations and provide a generalization of the framework that is applicable in other cross-matching scenarios.
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All authors V. Samuel Pérez-Díaz, Vinay L. Kashyap, Joshua D. Ingram, David Fouhey, Juan Rafael Martínez-Galarza, Pavlos Protopapas, Jeremy J. Drake, Dong-Woo Kim, Cecilia Garraffo
Mathematical Physics · Cross-listed from math.AP
Rigorous analysis for the Dirac system on the quarter-plane
Hassan Babaei, Jerry L. Bona and Andreas Chatziafratis
Considered and analyzed below are fully non-homogeneous initial-boundary-value problems for the celebrated Dirac system, formulated on the spatial half-line. Analytical solution formulae are derived formally via suitable implementation of the well-known Fokas' unified transform methodology, and rigorously verified a posteriori. The latter substantial task relies on complex-analytic tools and careful interpretation of the obtained integral representations. These valid solutions are then used for investigating qualitative properties. These include boundary behavior near the axes of the domain as well as long-range asymptotics and long-time (eventual) periodicity. Notably, smoothness of the solution, both within and upto the boundary of the domain, depends heavily on certain compatibility conditions between initial, boundary and forcing data. Further results pertaining to solution's regularity and uniqueness are thence established based on the qualitative theory. The closed-form expressions reported here are also useful in the study of non-linear counterparts.
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High Energy Physics (Theory)
Spectral Functions of Lorentzian Quantum Gravity
Gabriel Assant, Daniel F. Litim and Manuel Reichert
We compute spectral functions of graviton modes in Lorentzian
quantum gravity, interpolating between classical general relativity and an asymptotically safe ultraviolet fixed point. Using functional renormalisation adapted for theories in Lorentzian signature, and enhanced by new
symmetry conditions to account for underlying Ward identities, we derive and solve flow equations directly for the Källén-Lehmann representation of propagators. Consistent results are found for several sets of renormalisation conditions yielding normalisable spectral functions for the graviton and the scalar graviton mode, in agreement with effective theory in the infrared. We further calculate the full
quantum effective action to quadratic order in
curvature, extract graviton-induced form factors, and discuss implications for unitarity of
quantum gravity.
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High Energy Astrophysical Phenomena
GRMHD and GRRT Simulations of Black Hole Accretion: Flares, Precession, and Complex Spacetimes
Hong-Xuan Jiang
This dissertation studies the electromagnetic signatures of accreting supermassive black holes using general relativistic magnetohydrodynamic simulations and covariant radiative-transfer calculations. It develops a unified numerical framework for modeling black-hole
accretion, jet launching, flaring activity, and multi-band variability in Kerr, non-Kerr, and binary black-hole spacetimes. For isolated Kerr black holes, I investigate how
magnetic-field geometry affects
accretion dynamics and transient emission. Multi-loop
magnetic configurations naturally produce reconnection events and flux-rope structures that can power near-infrared
flares from Sagittarius A*, while the evolving optical depth of expanding
plasma explains delayed millimeter emission. I also show that in tilted magnetically arrested disks,
magnetic torques can drive retrograde disk and jet precession. The dissertation then applies the same framework to more complex spacetimes. Simulations of
accretion onto regular loop-
quantum black holes show that
quantum-
gravity corrections can modify
photon-ring size, polarization structure, and jet power, leading to observational constraints from Event Horizon
Telescope data. Finally, simulations of supermassive binary black holes in time-dependent spacetimes reveal how gravitational self-
lensing, shock activity, and
spin-orbit coupling shape multi-wavelength light curves and jet precession. Together, these results connect relativistic
plasma dynamics with current and future observations of black-hole systems.
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Mesoscale and Nanoscale Physics
Exclusion Statistics as a Thermodynamic Resource in Quantum Heat Engines
Sampurna Karmakar, Aziz Hasan and Sourin Das
The maximum power extractable from a
quantum thermoelectric heat engine operating with free
fermion carriers is bounded by the universal Whitney limit, $P_{\text{fermion}}^{\max} \simeq 0.0321\pi^2 k_B^2(T_L-T_R)^2/h$. We demonstrate that this bound is not fundamental to
quantum heat engines but is instead an artifact of fermionic statistics. Within the nonlinear Landauer-Büttiker framework, a bosonic working medium yields a strictly enhanced universal maximum power, $P_{\text{boson}}^{\max} = (\ln 2)^2\, k_B^2(T_L-T_R)^2/h$, exceeding the fermionic limit by a factor of $(\ln 2)^2/(0.0321\pi^2) \approx 1.52$. We propose
magnon transport through a
ferromagnetic spin chain as an experimentally viable bosonic realization. Incorporating Haldane fractional exclusion statistics with parameter $g$ provides a continuous interpolation between the bosonic ($g = 0$) and fermionic ($g = 1$) limits, revealing a monotonic enhancement of maximum power for $g < 1$ at reduced bias cost. These results establish
quantum statistical exclusion as a previously unrecognized and independently tunable thermodynamic resource, opening performance regimes inaccessible to conventional carrier-engineering approaches.
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Instrumentation and Detectors
Design and Commissioning of a Deuterium-Tritium Gas Delivery System for Muon Catalyzed Fusion in a Diamond Anvil Cell
Elena Koukina, Cody Fagan, Christopher Robert Shmayda et al. (+46 more)
We report the design, commissioning, and operation of deuterium-deuterium (DD) and deuterium-tritium (DT) gas delivery systems developed to load a diamond anvil
cell (DAC) beam target for
muon-catalyzed fusion (muCF). The DAC approach enables DT fuel to be compressed to GPa pressures at more than twice the
liquid density and heated from cryogenic temperatures through 500 K, opening access to a substantially expanded parameter range for muCF kinetics and yield measurements. In this approach, DT is cryo-condensed to a
liquid in a minichamber and then compressed in the DAC using a helium-driven pneumatic membrane, achieving high pressures in a millimeter-scale DT sample volume. A DD gas delivery system was designed and used to validate the experimental apparatus, measure the gas quantities needed for filling, develop operational experience, and collect kinetics and yield data with DD targets. The DT gas delivery system adds tritium-specific capabilities for inventory minimization, secondary containment, and activity monitoring. The DT system integrates depleted uranium storage beds and a
liquid helium cryogenic condenser used for pressure building and cryopumping. High-purity delivery is provided by a rapid-response palladium permeator. The system is housed in a helium-atmosphere glovebox held at negative pressure with continuous cleanup. We present the process and instrumentation design, a failure modes and effects analysis (FMEA), and data from the experiment's in situ Raman spectrometer, which provides direct confirmation of target loading and composition through the optically clear diamond anvils. The 2024 and 2025 DT campaigns achieved repeatable target fills and operation with no measurable tritium releases to the stack, demonstrating safe, high-purity DT loading at novel density-temperature conditions for muCF studies.
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All authors Elena Koukina, Cody Fagan, Christopher Robert Shmayda, Jonathan D Kalow, Demetrious M Harrington, George Harris, Kaylee McCormack, Munin Mundt, Kevin Lau, Dominik Zajac, Michael W. Koch, Sofia Varner, Alexander Golossanov, Stephen Bull, Robert Buxbaum, Walter Stadolnik, Joseph A Allen, Jose Betances, Nicholas Brennan, Rachel M Chaney, William Reuel Cutler, Jonathan Davies, Chad Forrest, Parth Gandhi, John Thomas Hinchen, Carol Johnstone, Katy Kem, Musheera Khandaker, Mandy Kiburg, Isaac Kiniti, Aaron D Knaian, Linda Knaian, Nate James Lewkowicz MacFadden, Daniel Mayer, Patrick C McDaniel, Evan D Niner, Karl Payne, Claude Petitjean, Robert Ridgway, Matt Russell, Anuj Sampat, Jeffrey Simon, Ira Spool, Ana Tejeda, Aldo Antognini, Kevin Lynch, Seth Newburg, Walter T Shmayda, Ara N Knaian
Atmospheric and Oceanic Physics
Optimal scenario design for climate emulation
Christopher B. Womack, Shahine Bouabid, Andrei Sokolov et al. (+4 more)
As deep learning for physical systems continues to grow in popularity, efforts to improve generalizability have primarily focused on designing architectures that embed physical constraints. However, for machine-learning surrogate
climate models (emulators), we show that the low structural diversity in existing scenarios commonly used to generate training data places a ceiling on predictive skill. Here, we examine whether training
datasets themselves can be optimized to improve generalization. We introduce a method to create
datasets that produce emulators capable of generalizing to new, structurally different scenarios absent from the training data. We use a differentiable Simple
Climate Model (SCM) to calculate the sensitivity of emulator loss to perturbations in the training data, iteratively updating the training data to maximize emulator skill. For an SCM, training on one scenario optimized in this fashion outperforms an emulator trained on six standard ScenarioMIP pathways. We achieve this higher predictive skill despite training on a smaller
dataset, finding that our emulator successfully isolates distinct physical behaviors of different
climate forcing
agents (e.g., greenhouse gases vs. aerosols) without single-forcing runs. We then demonstrate that scenarios optimized using an SCM, when used to drive an intermediate-complexity
climate model, produce a training
dataset that yields a more skillful emulator than training on ScenarioMIP outputs. Our results suggest that, in the compute-constrained environment of running full-scale
climate models, generating a small number of dynamically rich scenarios provides greater marginal value for emulation and characterizing system responses than expanding the suite of traditional emissions pathways.
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All authors Christopher B. Womack, Shahine Bouabid, Andrei Sokolov, Popat Salunke, Glenn Flierl, Sebastian D. Eastham, Noelle E. Selin
General Physics
An ideal Fermi gas under uniform gravity
Pattarapon Tanalikhit and Wittaya Kanchanapusakit
We consider an ideal
Fermi gas in a container subject to a uniform gravitational field at absolute zero temperature. Under a semiclassical approximation, we examine the density profile of the particles and derive an expression for the chemical potential. A critical value of the chemical potential separates the weak- and strong-
gravity regimes, and the kinetic and potential energies of the
Fermi gas are determined in both regimes.
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High Energy Physics (Experiment)
Probing Long-Lived Particle Production in Muon Decays at the SNS with a Highly Capable Hydrocarbon Detector
M. Andriamirado, A. B. Balantekin, C. D. Bass et al. (+43 more)
The Spallation
Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) is a prolific
muon producer, making it an ideal location for studying dark sector particles produced in
muon decays at rest. In this paper, we explore sub-GeV dark particle detection possibilities in a tons-scale, highly capable hydrocarbon scintillator ($HC^2$) detector at the SNS. We consider a search for $e^+e^-$ final states produced by decays of long-lived, $O(10-100)$ MeV
axion-like particles and heavy neutral
leptons. The $HC^2$ technology space, exemplified by the PROSPECT and Mobile Antineutrino Demonstrator detectors, offers strong rejection capabilities for the
cosmic ray backgrounds that would normally dominate this search. By benchmarking on-surface
cosmic ray signatures with data from PROSPECT at ORNL, we generate robust predictions for a multi-year SNS deployment of a range of $HC^2$ detector implementations. Results indicate the potential for order-of-magnitude improvements in sensitivity to
axion-like particles and heavy neutral
leptons in the 10-100 MeV mass regime compared to current global limits. We also comment on the
neutrino detection possibilities of a $HC^2$ deployment at the SNS.
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All authors M. Andriamirado, A. B. Balantekin, C. D. Bass, O. Benevides Rodrigues, E. P. Bernard, N. S. Bowden, C. D. Bryan, R. Carr, T. Classen, A. J. Conant, N. Craft, G. Deichert, A. Erickson, M. D. Fuller, A. Galindo-Uribarri, S. Ghosh, S. Gokhale, C. Grant, S. Hans, A. B. Hansell, T. E. Haugen, K. M. Heeger, A. Irani, J. Koblanski, C. E. Lane, B. R. Littlejohn, A. Lozano Sanchez, F. Machado, J. Maricic, M. P. Mendenhall, A. M. Meyer, R. Milincic, P. E. Mueller, H. P. Mumm, R. Neilson, J. R. Newby, D. Norcini, N. Patel, C. Roca, R. Rosero, D. Venegas-Vargas, J. Wilhelmi, M. Yeh, X. Zhang, M. Hostert, S. Urrea
Solar and Stellar Astrophysics
A New Methodology for Classifying Eclipsing Binaries with Kepler Data and Deep Learning
Mousam Mondal, Patricia Cruz, Hugh R. A. Jones et al. (+2 more)
We present a new method for the automated classification of eclipsing binaries, into contact, detached, and semi-detached types using Kepler data. Phase-folded light curves are generated and chi-square vs. box size plots are constructed by comparing flux values to the median flux, revealing distinct class patterns. These patterns were first modelled using a
polynomial damped sinusoidal function, whose period served as classification feature, achieving an overall accuracy of 86.5 percent. To capture more features and enhance accuracy, we trained a convolutional neural network, which improved the total accuracy to 90 percent, including 47 percent for the challenging semi-detached systems. However, several binaries displayed irregular chi-square signatures. To mitigate this, we incorporated simulated light curves generated with the PHOEBE modelling code, achieving 99 per cent accuracy in distinguishing contact and detached binaries. The resulting chi-square morphologies show a strong correlation with orbital period, and a subset of systems exhibit quarterly variability in their light curves and chi-square trends. We designate these as Temporally Varying systems. By measuring the normalized spread of the chi-square period across quarters, we define a statistical threshold that separates these systems from stable binaries. We reported four Temporally Varying systems not previously noted in the literature with
magnetic activity that requires further investigation. Furthermore, cooler
stars, namely late-F, G, K, and M types, display systematically higher variability than hotter
stars. Cross-matching with catalogues of magnetically active
stars indicates that
stellar flares and starspots are the most likely causes of this enhanced variability.
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All authors Mousam Mondal, Patricia Cruz, Hugh R. A. Jones, M. C. Gálvez-Ortiz, John F. Aguilar