Nuclear Theory
Effects of Strong Magnetic Fields on the Equation of State and Mass-Radius Structure of Hyperonic Neutron-Star Matter with Anomalous Magnetic Moments
W. German, T. Mello, J. P. W. Diener et al. (+1 more)
We investigate the effects of strong
magnetic fields on the equation of state (EoS) and
stellar structure of cold, charge-neutral, $\beta$-equilibrated hyperonic
neutron-
star matter within a relativistic mean-field (RMF) framework. The matter sector contains the full
baryon octet and
leptons, while charged particles are Landau quantized and all
baryons are coupled to the
magnetic field through their anomalous
magnetic moments (AMM). The calculation is performed with the RMF FSU2H hyperonic parameterization and compared for zero field, constant
magnetic fields, and density-dependent
magnetic-field profiles. We find that strong
magnetic fields modify the hyperonic composition through the competing effects of Landau quantization and AMM-induced
spin splitting. Landau quantization softens the magnetized hyperonic equation of state. The inclusion of AMM provides an additional
magnetic stiffening mechanism in hyperonic matter. The results for the inclusion of the AMM coupling and not are still consistent with observations of $2.00$-$2.02\,M_{\odot}$
neutron stars and small radii. The present work therefore provides a
benchmark for assessing the influence of AMM on the composition, magnetization, equation of state, and mass-radius structure of magnetized hyperonic
neutron-
star matter.
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All authors W. German, T. Mello, J. P. W. Diener, G. C. Hillhouse
High Energy Physics (Theory)
An Infinite Family of Non-Rational VOAs from Strongly Coupled 4d Higgsless SCFTs
Hongliang Jiang
We study an infinite family of strongly coupled four-dimensional $\mathcal N=2$ superconformal field theories (SCFTs) distinguished by a trivial
Higgs branch, known as the $(A_2,D_{3m+1})$ Argyre-Douglas theories. We propose that their associated vertex operator
algebras (VOAs) are the doublet
algebras $\mathcal A(4m+2)$, an infinite family of non-rational vertex operator superalgebras with a remarkably simple strong generating set of only three fields. We provide several highly nontrivial checks of this proposal. In particular, we reproduce the four-dimensional conformal anomalies $a$ and $c$ from the VOA and analytically prove the exact equality between the Schur index of the SCFT and the supercharacter of the VOA. A key ingredient is a diagonal-gauging realization of the $(A_2,D_{3m+1})$ theories in terms of two simpler building blocks, which makes the Schur-index computation tractable. Remarkably, we find that the resulting Schur index of the $(A_2,D_{3m+1})$ theory coincides with that of $\mathcal N=4$ $SU(2)$ Super-Yang-Mills theory, up to an overall prefactor and an appropriate identification of fugacities. We also discuss a generalization to the two-parameter family $(A_{2s},D_{(2s+1)m+1})$, whose members likewise have trivial
Higgs branches and admit diagonal-gauging realizations. A particularly interesting subfamily is $(A_{2s},D_{2s+2})$, for which the four-dimensional conformal anomalies coincide, $a=c$. As a byproduct, we also show that the doublet VOA $\mathcal A(4m+2)$ is not classically free for positive integer $m $, and we discuss its implications for the Schur and Macdonald indices. Our results reveal a systematic connection between Higgsless SCFTs, diagonal gauging, and strongly finite but non-rational vertex operator
algebras.
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Materials Science
Chemical pressure and vacancies in crystals under nonhydrostatic stress
Michiel Sprik
Inhomogeneous stress is a driving force for
diffusion of vacancies in
crystals. The other way around a non-uniform distribution of vacancies induces stress. The accepted theory of composition-stress coupling in
crystals is Larché-Cahn (LC) theory. Composition is defined in terms of the population of
lattice sites with a limit of one-particle per site. Coupling is modelled by adding a compositional strain term to the elastic strain in the constitutive relation for stress. An alternative mechanism, proposed here, is letting the site binding energy vary with spatial (deformed) density. This generates a chemical pressure adding to the elastic stress. The governing equations for this model are derived using non-
equilibrium continuum thermodynamic methods. The gradient of the chemical pressure has a dual function acting both as the drift force for migration and as an effective internal one body force in the Cauchy equation for the elastic stress. The practical evaluation presented in the paper is restricted to
equilibrium properties. We examine the effect of externally applied non-hydrostatic stress, either in the form of surface tractions or a one-body force density (gravitation). The model system is a one component
crystal with a fixed number of
lattice sites. The number of particles can be variable but is always smaller than the number of
lattice sites. The linear elastic response is modelled by the standard Lamé stress tensor. The results for systems deformed by surface tractions are in qualitative agreement with LC theory allowing for differences in the expression for the elastic
moduli. Deviations are more serious for the
crystal deformed by gravitation.
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Physics Education
Student responses to a modified Force Concept Inventory: The Newtonian Mechanics Quiz
Ashutosh Kumar Pathak, Mark A. J. Parker, Andrew J. A. James et al. (+2 more)
Even in the era of modern physics, understanding and applying Newton's classical Laws of Motion are key skills for physicists and form a core component of instructional programmes. Students arrive in the classroom with intuitive ideas about force and motion that are often misaligned with Newtonian thinking. Prior research has shown that these incorrect intuitive ideas are remarkably persistent, and can stay with students throughout their education and beyond. Reliable instruments, that can accurately evaluate student understanding of Newtonian mechanics, are required to track student progress and evaluate the efficacy of instructional programmes. The Force Concept Inventory (FCI), a conceptual quiz composed of multiple-choice questions, is a well-established instrument, developed to address these challenges. The FCI, and how students respond to its questions, has been widely investigated and discussed in the literature. Notably, research has shown that: correct responses to questions do not always correspond to correct application of Newtonian concepts; and the limited response options given for multiple-choice questions often do not capture the full range of student thinking. There is therefore a burgeoning need to develop new instruments that probe students' understanding at a deeper level, by interrogating conceptual understanding from multiple perspectives and incorporating different question formats that require students to construct and consider their responses. We introduce the Newtonian Mechanics Quiz (NMQ), a modified version of the FCI that incorporates follow-up questions in a variety of formats, each with different diagnostic functions. This article describes the development and validation of the NMQ instrument, and illustrates several novel analyses enabled by the student response
dataset that can offer deep insight into students' conceptual understanding of Newton's Laws.
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All authors Ashutosh Kumar Pathak, Mark A. J. Parker, Andrew J. A. James, Sally E. Jordan, Jonathan Nylk
Mesoscale and Nanoscale Physics
Rank-Selective Optical Tomography of Higher-Wave Altermagnetism
Meysam Bagheri Tagani, Carmine Autieri and Sahar Izadi Vishkayi
Identifying the spatial rank of higher-wave altermagnetic order optically is challenging because local electric-dipole response does not uniquely resolve distinct continuum harmonics. We show that finite
photon momentum turns one-
photon spin-resolved absorption into a rank-selective
tomography. For the planar $|m|=\ell$ sector of an even-parity $\ell$-wave component, a joint
Fourier projection in polarization and momentum angle isolates $\mathcal T_\ell\propto\eta_\ell q^{\ell-2}$, yielding the hierarchy $d:q^0$, $g:q^2$, and $i:q^4$; phase changes track rotations of the selected
magnetic harmonic. A Ward-consistent finite-$q$ microscopic calculation reproduces these powers without imposing them. Although discrete
crystal symmetry can generate lower-order local aliases, they are orthogonal to the selected momentum harmonic and cannot contaminate it below $q^{\ell-2}$. In MnTe, whose nonrelativistic parent order is three-dimensional $g$ wave while
spin–orbit coupling lowers the exact relativistic
spin-momentum-locking
symmetry, first-principles calculations show that more than $99.9\%$ of the
Fourier power of the Néel-projected $A$-region
spin-energy contrast remains in the parent $g$-wave-derived $m=3$ harmonic. Structured near fields place the required momentum window within experimental reach.
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Quantum Physics
Circuit-Level Loss Performance of RHG and Foliated Floquet Color Codes in a Compound Photon–Atom Quantum Architecture
Dana Ben Porath, Juval Bechar, Daniel Azses et al. (+1 more)
A central question for fault-tolerant
quantum computing is which
quantum error-correcting codes are best suited to a given hardware architecture. Here we compare the Raussendorf–Harrington–Goyal (RHG) code, the Foliated Floquet Color Code (FFCC), and the reduced FFCC in a compound
photon–atom architecture that directly generates measurement-based
quantum computation (MBQC) resources with near-deterministic
photon–atom CZ gates. RHG serves as a natural
benchmark, while the FFCC variants allow us to study whether reduced graph degree improves performance under an architecture-aware
circuit-level loss model with delayed heralding and correlated bond-loss propagation. We construct two generation schemes compatible with the compound hardware and evaluate
circuit-level thresholds under periodic boundary conditions. RHG achieves the highest
circuit-level threshold, 2.75%, and its threshold falls below that of reduced FFCC only for large excess loss on intermodule CZ connections. RHG also achieves the lowest logical error rate in most resource-matched comparisons, but some low-loss windows favor reduced FFCC. Overall, we show that when the hardware supports the native gates and connectivity required for MBQC, the benefits of lower graph degree must be weighed against each code's intrinsic IID loss tolerance, generation-scheme details, and hardware-aware resource overhead.
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All authors Dana Ben Porath, Juval Bechar, Daniel Azses, Yaron Jarach
High Energy Physics (Theory)
Localization and Abelianization of Strings on Group Manifolds: The Simply Connected Case
Yongchao Lü
We study the localization formula for the partition function of the Wess–Zumino–Witten (WZW) model on the
torus for compact, connected, and simply connected simple Lie groups. We identify a missing factor in the original localization treatment of Murthy and Witten and show that it agrees with the result obtained from the
Hamiltonian formulation. We trace its origin to the abelianization of the Wess–Zumino amplitude, which reduces to a flat Kalb–Ramond B–field holonomy in a Narain
lattice CFT associated with the maximal
torus. This establishes a direct relation between the localization result and the
lattice description of the corresponding abelian theory. We further analyze the point–particle limit of the
torus partition function, in which the WZW model reduces to
quantum mechanics on the group
manifold, and reproduce Frenkel's heat–kernel trace formula.
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Chaotic Dynamics
An active Lorentz gas: walking droplets in periodic media
Aleksi Majaniemi, Esko Toivonen, Rahil N. Valani et al. (+2 more)
The Lorentz gas is a paradigmatic model in dynamical systems theory for understanding the origin of nonequilibrium transport in terms of microscopic deterministic chaos. In the periodic setting, a point particle scatters elastically off disks arranged on a two-dimensional
lattice. Here we replace the disks by smooth potentials and the particle by the widely studied walking droplet, which propels itself on a vertically vibrating fluid. In the low-
memory limit, this droplet reduces to a particle with nonlinear active friction. We call this system an active Lorentz gas. Using extensive numerical simulations, we analyze how dissipation generated by the active deterministic dynamics alters the phase-space structure of the corresponding conservative Lorentz gas. We find that islands of stability collapse into attracting and repelling sets. To characterize these structures, we introduce an energy-variance filtering method that distinguishes localized periodic, quasi-ballistic periodic, and chaotic trajectories, enabling the construction of bifurcation diagrams in a non-conservative setting. We identify parameter regimes exhibiting strong bifurcation cascades, anomalous
diffusion, and significant phase-space contraction. Our results establish the active Lorentz gas as a rich framework for studying transport in dissipative dynamical systems and provide a bridge between active matter and classical models of chaotic transport, with potential implications for hydrodynamic
quantum analogs in periodic media.
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All authors Aleksi Majaniemi, Esko Toivonen, Rahil N. Valani, Rainer Klages, Esa Räsänen
High Energy Physics (Theory) · Cross-listed from math.AG
Membranes and Maps
Alessandro Giacchetto, Rahul Pandharipande and Yannik Schuler
In positive degree, equivariant Gromov-Witten invariants of Calabi-Yau fivefolds are expected to admit an interpretation in terms of M2-branes, while we
conjecture that constant maps are governed by the corresponding supergravity index. We make the first expectation precise by proposing a modular interpretation of M2-branes supported on several smooth curves meeting at an $n$-fold point. Together, the two pictures yield conjectural formulas for the Gromov-Witten invariants, which we translate into closed formulas for pointed and unpointed quintuple Hodge integrals. We show that these
conjectures imply a K-theoretic Gromov-Witten/Pairs correspondence for local curves in degree one and link the generating series of constant maps to Donaldson-Thomas theory of points. We also prove the
conjectures in two limits of the equivariant parameters. Along the way, we obtain new closed formulas for certain triple Hodge integrals.
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Instrumentation and Methods for Astrophysics
CHARA/SPICA: The six-telescope visible combiner and near-infrared fringe tracker for the CHARA Array
D. Mourard, P. Bério, C. Bailet et al. (+43 more)
The suite called
Stellar Parameters and Images with a Cophased Array (SPICA) has two interferometric instruments installed at the focus of the CHARA Array located at Mount Wilson, CA. SPICA is made of SPICA-VIS, a fiber-fed six-beam visible spectrograph with three spectral resolutions, and SPICA-FT, a six-beam near-infrared fringe tracker for the fast stabilization of the fringes. SPICA is opening access to imaging in the visible domain with an unprecedented angular resolution down to 0.2 milliarcseconds. It has been designed around a large survey of fundamental parameters of
stars over the Hertzsprung- Russell diagram, aiming at understanding the deviations from the standard empirical relations of
stellar physics as a function of activity: limb darkening, multiplicity, rotation, winds, and environments. SPICA makes use of the advanced technologies in electron multiplying detectors in the visible and electron- avalanche photodiode arrays in the near-infrared. It benefits from the newly commissioned adaptive optics on the one-meter
telescopes of the array. The modules of the visible instrument, SPICA-VIS, optimize the injection of light into single-mode fibers for spatial filtering before spectral dispersion in the image plane. The fringe tracker, SPICA-FT, performs group-delay and phase-delay tracking for six beams in the H band. SPICA-FT can use an all-in-one or ABCD encoding of the fringe signals. SPICA is operational on sky and is close to reaching the expected performance in low spectral resolution, in particular, for the Interferometric Survey of
Stellar Parameters (ISSP). More work is still needed to achieve the ultimate performance in terms of sensitivity and to allow operations with higher spectral resolutions.
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All authors D. Mourard, P. Bério, C. Bailet, A. Caci, J. Dejonghe, P. Geneslay, S. Lagarde, D. Lecron, A. Meilland, F. Morand, N. Nardetto, C. Pannetier, K. Perraut, S. Rousseau, D. Salabert, N. Ebrahimkutty, R.V. Ibañez Bustos, J. Jonák, R. Ligi, H. Nowacki, F. Patru, M. Vrard, L. Bourgés, G. Mella, N. Anugu, T. ten Brummelaar, C. Farrington, D. Gies, J. Jones, R. Koehler, K. Kubiak, C. Lanthermann, R. Ligon, G. Schaefer, N. Scott, N. Turner, J. Monnier, S. Kraus, J.B. Le Bouquin, T. Gardner, M. Gutierrez, N. Ibrahim, E. Aristidi, Y. Caujolle, C. Giordano, A. Ziad
Quantum Physics
Constructing and characterising anharmonic potentials in a harmonic oscillator
Clara Yun Fontaine, Mansi Somani, Kehui Yu et al. (+9 more)
Continuous-variable
quantum systems offer a natural platform for
quantum information processing and analogue
quantum simulation of real-world processes. Realising these applications, however, requires anharmonic potentials with programmable functional forms, which are challenging to engineer on demand. Here, in a superconducting harmonic oscillator coupled to a transmon
qubit, we construct programmable non-Gaussian phase gates $e^{-iV(\hat{X})}$, corresponding to the impulsive action of an anharmonic potential $V(\hat{X})$, and characterise them by reconstructing their corresponding force pointwise. Using bosonic
quantum signal processing, we compile target potentials into modular
circuits of
qubit rotations interleaved with a fixed conditional-displacement primitive. We first demonstrate a cubic phase gate whose cubic nature is jointly validated by the resulting non-Gaussian states and the force reconstructed pointwise from the gate's action on coherent probe states. We then construct a family of double-well potentials and use the reconstructed force to witness the double-well
topology and tunable asymmetry. Finally, we engineer an approximate Morse potential and obtain its force profile using position-compressed probes, which extend reliable reconstruction towards the steep repulsive wall. These results establish a programmable route to constructing the potential landscape of
quantum harmonic oscillators and a practical method for reconstructing its spatial structure, providing a building block for
quantum simulation of anharmonic dynamics.
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All authors Clara Yun Fontaine, Mansi Somani, Kehui Yu, May Chee Loke, Jonathan Schwinger, Pak-Tik Fong, Ni-Ni Huang, Adrian Copetudo, Mustafa Bakr, Hoi-Kwan Lau, Tanjung Krisnanda, Yvonne Y. Gao
Mesoscale and Nanoscale Physics
Direct observation of flat bands in near-magic-angle twisted bilayer CVD graphene
Gianluigi Baiardi, Alex Boschi, Giulia Piccinini et al. (+13 more)
Advances in chemical vapor deposition (CVD) growth have driven
graphene crystal quality to unprecedented levels, yet it is still unknown whether this route can realize the fragile flat-band and correlated states of the magic-angle (MA) twisted
bilayer graphene (TBG). Here, we report on the experimental observation by room-temperature nano-angle-resolved photoemission spectroscopy (nano-ARPES) of flat bands in a TBG sample close to the MA, assembled via a grow-and-stack protocol based on low-pressure CVD of
graphene on copper. Our study indicates electronic bands fully comparable to those measured in exfoliation-based samples and determines the size of the largest near-MA domain to be compatible with electronic transport experiments, motivating further experiments on flat band physics in CVD-
graphene.
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All authors Gianluigi Baiardi, Alex Boschi, Giulia Piccinini, Vaidotas Mišeikis, Lorenzo Cavicchi, Aaron Bostwick, Chris Jozwiak, Eli Rotenberg, Kenji Watanabe, Takashi Taniguchi, Marco Polini, Fabio Beltram, Antonio Rossi, Stiven Forti, Sergio Pezzini, Camilla Coletti
Solar and Stellar Astrophysics
Multiplicity of Cool Stars and their Evolution
Matthew I. Swayne, Leen Decin, Theo Khouri et al. (+12 more)
Making up a sizeable portion of the
galactic census,
stellar multiples are experiencing a renaissance. Enabling the study of multiple strands of the study of cool
stars,
stellar multiples have been found and characterised in great numbers by the missions of the last decade, allowing the exploration of
stellar parameters and populations, observation of
stellar interactions, studies into
stellar formation and
evolution, and characterisation of circumbinary systems. This exciting explosion of science is only set to continue, with future missions set to offer even further insights into the topic. Within these proceedings we will summarise the presentations and discussions on cool
stellar multiplicity within our splinter sessions at the 23rd Cambridge Workshop on Cool
Stars,
Stellar Systems, and the Sun, as we examine the present state of the field and look to what the future may bring.
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All authors Matthew I. Swayne, Leen Decin, Theo Khouri, Ayush Moharana, Léa Planquart, John Southworth, Nikki J. Miller, José A. Caballero, Orsolo De Marco, Krzysztof G. Hełminiak, Swetlana Hubrig, Valentin D. Ivanov, Pierre Kervella, Thibault Merle, Dorota M. Skowron
Materials Science
Symmetry-based modal analysis of heat transport in molecular dynamics of quasi-1D systems
Yu-Jie Cen, Sandro Wieser, Georg K. H. Madsen et al. (+1 more)
Detailed analysis of thermal conductivity results obtained from molecular dynamics (MD) trajectories conventionally relies on knowledge of the harmonic vibrational modes of the system. This is the case in methods like Green-Kubo modal analysis (GKMA) and homogeneous nonequilibrium modal analysis (HNEMA). However, arbitrary mixing within degenerate
phonon subspaces makes individual modal contributions basis dependent and can obscure their
symmetry character. We propose an alternative for quasi-one-dimensional (quasi-1D) systems: we construct the modal basis for the decomposition of the thermal conductivity from line-group projection operators, so that every projected component carries well-defined
symmetry labels (including rotational information and parities) and the decomposition is unique at the level of irreducible representations (irreps). Applying the idea to a (10, 0)-(20, 0) WS2-MoS2 double-walled nanotube (DWNT) described by a neuroevolution potential (NEP), we find that at 300 K both HNEMA and GKMA yield statistically consistent total conductivities and allow the identification of several prominent
symmetry-adapted conduction channels. The GKMA pair
matrix shows that within-block and same-channel cross-k terms account for 75.6% of the total conductivity, while cross-channel correlations contribute 24.4%.
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All authors Yu-Jie Cen, Sandro Wieser, Georg K. H. Madsen, Jesús Carrete
High Energy Astrophysical Phenomena
Searching for optical pulsations from spider millisecond pulsars with the fast photometer SiFAP2
Christian Malacaria, Alessandro Papitto, Filippo Ambrosino et al. (+18 more)
Optical pulsations from millisecond
pulsars (MSPs) have recently been detected in a transitional MSP and an accreting MSP. Evidence for optical pulsations has also been found for a rotation-powered redback MSP. Observations suggest that optical pulsed emission is produced by different mechanisms depending on whether an
accretion disk is present in the system. We explored a sample of rotation-powered MSPs in close binaries (P$_{orb}<1\,$day; redbacks and black widows), searching for optical periodic signals with the $SiFAP2$ photometer mounted on the $Telescopio\,Nazionale\, Galileo$ (TNG). We performed pulsation searches using the epoch-folding method with the most up-to-date (
radio or gamma-ray) orbital solution for each system. These solutions were based either on previously published works or recent observations from Nançay, the
Giant Metrewave
Radio Telescope, the Parkes Observatory, and $Fermi$-LAT. We update or confirm
radio and gamma-ray ephemerides for five of the presented systems. No optical pulsations were detected with a significance exceeding a $3\sigma$ confidence level in any of our searches, despite achieving sensitivities close to the instrument's limit. This places correspondingly stringent upper limits on the systems' optical pulsed magnitude and conversion efficiency. Our upper limits are consistent with the pulsed optical luminosity of optical pulsations from the redback PSR J2339-0533. Compared to accreting and transitional MSPs, redback and black widow systems show much lower efficiency in converting their
spin-down power into pulsed optical emission. This supports the recent suggestion that the
accretion disk around the
neutron star plays a role in accelerating the particles responsible for producing bright optical pulsed emission.
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All authors Christian Malacaria, Alessandro Papitto, Filippo Ambrosino, Caterina Ballocco, Riccardo La Placa, Giulia Illiano, Arianna Miraval Zanon, Luigi Stella, Marco Turchetta, James D. Turner, Clara Blanchard, Ignacio Cognard, Lucas Guillemot, Marta Burgay, Aleksandr Burtovoi, Andrea Sanna, Sergio Campana, Massimo Cecconi, Adriano Ghedina, Andrea Possenti, Diego Torres
Quantum Physics
A Recursive Module-Coupling Algorithm for Computing Low-Energy Eigenstates
Dihang Sun, Nannan Ma, Ching Hua Lee et al. (+2 more)
Finding the eigenstates of a many-body
Hamiltonian is a fundamental challenge in physics and computational science. Since the search space grows exponentially with system size, numerous classical and
quantum algorithms have been developed to address this problem. A practical strategy is to identify a physics-informed low-dimensional subspace that effectively accommodates the low-lying eigenstates, thereby reducing the computational complexity. In this paper, we propose a recursive module-coupling
algorithm, which iteratively treats a system as a composition of locally-coupled smaller modules, with low-energy subspace estimated successively according to the same recursive structure. Unlike the density
matrix renormalization group (DMRG) approach that optimizes a global
matrix product state through repeated local sweeps and obtains excited states sequentially, our
algorithm constructs a physically tailored variational basis from module eigenstates and obtains several low-energy states on an equal footing, leading to substantial speedups if targeting moderate accuracy. Our proposed method further leads naturally to a recursive
quantum variational
algorithm, providing a systematic and modular
circuit-construction framework compatible with contemporary gate-based
quantum architectures. At each recursive level, block encoders are trained to map logical basis states onto the retained physical subspace, within which a variational
circuit is subsequently optimized. Such a
quantum-
circuit implementation provides not only a
quantum multistate eigensolver, but also a systematic prescription for hierarchically constructing
quantum state-preparation
circuits. Classical simulations demonstrate the accuracy and efficiency of the proposed method, whereas experiments on IBM
quantum processors show that eigenstate preparation with reasonable fidelities is achievable even in the current NISQ era.
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All authors Dihang Sun, Nannan Ma, Ching Hua Lee, Tianqi Chen, Jiangbin Gong
High Energy Physics (Phenomenology)
Strictly solvable $d=4$ quantum field theory models with unitarity violation. Possible implications for baryon asymmetry of the Universe and dark matter
N.V.Krasnikov
In this paper we consider
quantum field theory with unitarity violation. We construct several $d = 4$ strictly solvable models with unitarity violation. As a possible application of the models with unitarity violation we construct two models explaining the observed
baryon asymmetry of the Universe and the dark matter existence. In considered models dark matter particles have nonzero
baryon number and the total
baryon number of the Universe being the sum of the
baryon number of the matter and dark matter is equal to zero. Dark matter paricles have mass $\sim 6~GeV$. Proposed models predict negligible cross sections of the dark matter with
nuclei and electrons. It means that underground experiments will fail to discover dark matter.
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General Relativity and Quantum Cosmology
The Analytical Solutions of Dyonic Black Holes in Einstein-Euler-Heisenberg Theory
Haoyuan Luo, Nan Cao, Xiao Yan Chew et al. (+3 more)
Recently, we constructed analytical purely electric and purely
magnetic black-hole solutions in Einstein–Euler–Heisenberg theory, while the corresponding dyonic solutions were obtained numerically \cite{Luo:2026srx}. Motivated by the recent analytical construction of a dyonic black hole at the special coupling locus $b=a/2$ \cite{Ahmed:2026ufj}, we revisit the general dyonic sector. We show that exact analytical dyonic black-hole solutions can be constructed for nonlinear couplings satisfying $2b>a$, without imposing the restriction $b=a/2$. The mass function is expressed in closed form in terms of the Lauricella hypergeometric function. In particular, our construction yields an exact dyonic solution for the Euler–Heisenberg coupling $b=7a/4$. The solution of Ref.~\cite{Ahmed:2026ufj} is recovered in the limiting case $2b\rightarrow a$.
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All authors Haoyuan Luo, Nan Cao, Xiao Yan Chew, Kok-Geng Lim, Chao Chen, Dong-han Yeom
Astrophysics of Galaxies
Inside-out growth and the kiloparsec-scale star formation main sequence for low-surface-brightness disk galaxies in MaNGA
Bing-qing Zhang, Ze-hao Zhong, Yi-nan Zhu et al. (+1 more)
Low surface brightness
galaxies (LSBGs) are very faint objects in the universe whose formation and
evolution have long remained an unresolved problem. We selected a late-type, face-on, and disk-dominated
galaxy sample from the MaNGA survey, composed of 38 LSBGs and 216 high surface brightness
galaxies (HSBGs) by adopting a central surface brightness threshold $\mu_{0}(g) = {\rm 22.0\ mag\ arcsec^{-2}}$. Based on maps derived from pipe3D products of
star-forming areas in
galaxies, we investigated the global and resolved
star formation main sequence (SFMS and rSFMS) and radial profiles of the
stellar mass density ($\mathrm{\Sigma_{*}}$),
star formation rate density ($\mathrm{\Sigma_{SFR}}$), and specific
star formation rate ($\mathrm{\Sigma_{sSFR}}$). The radial profiles of $\mathrm{\Sigma_{*}}$ and $\mathrm{\Sigma_{SFR}}$ present negative gradients, while those of $\mathrm{\Sigma_{sSFR}}$ present positive gradients. Compared to HSBGs, the LSBGs show similar, flatter, and steeper slopes in $\mathrm{\Sigma_{*}}$, $\mathrm{\Sigma_{SFR}}$, and $\mathrm{\Sigma_{sSFR}}$ gradients, respectively. The very flat $\mathrm{\Sigma_{SFR}}$ gradients of LSBGs, whose slopes range from -0.1 to -0.2, indicates uniform
star formation throughout the whole
galaxy, and the positive $\mathrm{\Sigma_{sSFR}}$ gradients reflects their “inside-out” growth. Our LSBGs and HSBGs follow the same global and resolved SFMS as the full sample, and $\mu_{0}$ shows no influence on both SFMS and rSFMS. For our full sample and two subsamples (HSBGs and LSBGs), the slopes of global SFMS and rSFMS are consistent, which indicates that the SFMS still hold on a kiloparsec scale and the
star formation activities are regulated by local events. The treatment of different excitation sources in
galaxies affects the slope of the SFMS and rSFMS, and using
star-forming areas only is more advisable.
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All authors Bing-qing Zhang, Ze-hao Zhong, Yi-nan Zhu, Hong Wu
Biological Physics · Cross-listed from q-bio.CB
3D hybrid cellular Potts model with a discrete deformable fiber network: modeling cell contraction and extracellular matrix remodeling
Koen A.E. Keijzer and Roeland M.H. Merks
The extracellular
matrix (ECM) is a fibrous and dynamic network that plays a critical role in development, homeostasis, and disease.
Cells both respond to and remodel the ECM, engaging in a mechanical reciprocity that shapes tissues. To study these interactions, computational models have been developed that simulate either ECM mechanics or
cell behavior. The Cellular Potts Model (CPM) is a flexible
cell-based framework that has been extended to many biological processes, including coupling to a discrete deformable fiber network. So far, however, this extension has only been applied in two dimensions, even though a three-dimensional setting is biologically more relevant. Here, we present a 3D hybrid framework that couples the CPM with a discrete and deformable representation of the ECM. This model enables explicit simulation of
cell-induced ECM remodeling, including fiber reorientation and
matrix densification. By incorporating contractile forces through static adhesion points, the model captures how ECM elasticity and fiber stiffness influences
cell shape. The simulations show that ECM stiffness, controlled by fiber crosslinking, resists contraction and reaches
equilibrium, while crosslink density modulates fiber
alignment and local
matrix accumulation. This framework provides a versatile platform for studying
cell-ECM mechanics and supports future studies of multicellular behavior in realistic 3D environments.
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Optics
Static and breathing dynamics of optical bullets in nonlinear GRIN fibers
Sonali Maity, Tiyas Das, Anuj P. Lara et al. (+2 more)
We explore the properties of spatiotemporal
solitons within nonlinear graded-index (GRIN) optical fibers, specifically addressing their formation, stability, and breathing dynamics. We solve the (3+1)-dimensional nonlinear Schrödinger equation employing a semi-analytical variational approach, which leads to a set of reduced coupled ordinary differential equations describing the bistable bullet dynamics. The stability of these states is assessed using the Vakhitov-Kolokolov criterion and linear stability analysis within the Kantorovich optimization framework. The breathing dynamics of the optical bullets are investigated adopting the potential formalism, revealing an oscillatory behavior and self-imaging dynamics in GRIN fibers. The analytical results demonstrate strong agreement with full numerical simulations, validating the robustness of our theoretical model. Our research enhances the understanding of stabilizing self-repeated 3D optical structures, which is beneficial for the development of advanced photonic technologies.
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All authors Sonali Maity, Tiyas Das, Anuj P. Lara, Ashis Paul, Samudra Roy
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Percolation Dynamics in Optimization: Variance Cascades and Nested Symmetry
Sai Niranjan Ramachandran and Suvrit Sra
We study the dynamics of
Stochastic Gradient Descent (SGD), which is known to steer deep neural networks toward invariant sets that correspond to simpler subnetworks. How this steering unfolds over time remains poorly understood. We answer this by modeling the
stochastic gradient flow (SGF) as a percolation process, in which nested architectural
symmetries force subnetworks to merge in discrete blocks rather than by single-edge attachment. These structural transitions register as variance spikes in a macroscopic order parameter echoing physical phase transitions. We further state sufficient conditions under which the trapping argument carries over to Adam and AdamW under heavy-tailed gradient noise and measure them on a trained
Transformer.
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Quantum Physics
Implementation of quantum gates by Floquet analysis of kicked quantum system
Andrea De Luca, Carola Ciaramelletti and Simone Paganelli
Precise control of multi-
qubit architectures remains a critical bottleneck in superconducting
quantum processors. In this work, we investigate the synthesis of high-fidelity
quantum operations and state transfer protocols within an extended superconducting linear chain, scaling from three to seven sites. Using Floquet theory, we model the periodic drive as a train of delta-like pulses, mapping the
quantum control problem onto quasi-energy resonance conditions. Combining the Baker-Campbell-Hausdorff expansion with Floquet spectral decomposition, we analytically identify optimal driving parameters, refined via the Covariance
Matrix Adaptation
Evolution Strategy (CMA-ES). In the three-
qubit architecture, this enables high-fidelity synthesis of the iSWAP gate. Extending to a seven-site chain, we implement periodic trains of finite-width Gaussian pulses to activate distinct double-excitation transport channels with ultra-short gate durations t_gate (~170 ns). This achieves a clear scale separation from energy-relaxation times (T1) typical of fixed-frequency transmon devices with tunable couplers, such as IBM
Quantum hardware. Finally, we
benchmark stability under realistic imperfections, revealing a heightened sensitivity to static parameter disorder at the sub-percent level (eta ~ 10^-3) driven by spectral crowding, and discuss how closed-loop
topologies could mitigate this constraint. This framework bridges time-periodic control theory and practical
quantum gate engineering.
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High Energy Physics (Theory)
Surprises of Klein paradox
T. R. Ahmadov, E. T. Akhmedov and V. I. Lapushkin
We consider second quantized $1+1$ dimensional Dirac
fermions with mass $m$ in background electric fields. This theory mimics the following situations. We consider two parallel capacitors with opposite directions of the electric field $E$ in them. The potential energy difference in one of them is equal to $V_0 > 2m$ and in the other to $V+V_0$, with $0<V<2m$. According to general physical understanding of the Schwinger effect, each capacitor separately will create pairs and there will be oppositely directed currents, which will not be equal to each other. The total current will not vanish. In this paper we show that this is too naive an observation: the limiting expectation value of the current operator, as $t\to +\infty$, is actually zero, if the above form of the potential with $0<V<2m$ is instantaneously turned on. The non-vanishing current is obtained only if $V>2m$. We also consider the same theory in the presence of the infinite wall and a deep well $V_0>2m$. We show that in such a potential the limiting expectation value of the current is zero in the Gaussian approximation. We discuss the relation of these observations to the Schwinger effet and to the decay of supercritical
nuclei.
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Materials Science
Magneto-Structural Coupling Enables Cryogenic Cation Redistribution in a Spinel Oxide
Yifeng Han, Yixing Zhao, Yunbo Ou et al. (+11 more)
Ionic transport in
oxides is generally frozen at cryogenic temperatures, where thermal energy lies far below typical cation-migration barriers.
Neutron powder diffraction reveals progressive Fe/Mg redistribution between tetrahedral (A) and octahedral (B) sites in the spinel Mg0.5Fe0.5TiFeO4 upon cooling from 200 K to 5 K. A-site Fe occupancy increases toward near completion at 5 K within Rietveld resolution, while Ti remains on the B site. This exchange coincides with complex
magnetic correlations rather than a classical thermally activated window. Low-temperature magnetostrictive volume changes indicate strong
spin-
lattice coupling, but do not identify magnetostriction as the sole thermodynamic driver. Room-temperature high-pressure X-ray diffraction produces the opposite occupancy trend, showing that volume contraction alone cannot explain the cryogenic site exchange. These results point to magneto-structural free-energy minimization as a plausible mechanism for unlocking cryogenic cation mobility in a correlated spinel
oxide.
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All authors Yifeng Han, Yixing Zhao, Yunbo Ou, Feiran Shen, Lunhua He, Ligang Xu, Mingxue Tang, Jared Matteucci, Zexiao Zhang, Xiaoli Ma, Xiaohui Yu, Zheng Deng, Man-Rong Li, Alexandra Navrotsky
Quantum Physics
DMRG using Belief Propagation
Hendrik Kühne and Christian B. Mendl
Tensor networks have attracted much
attention as a powerful tool for modeling
quantum many-body systems. Their contraction is a significant challenge, however, especially in highly connected networks, as
memory requirements become prohibitive and the optimal contraction order is increasingly hard to find. The belief propagation (BP)
algorithm has emerged as an alternative to exact contraction. Being formulated in a graph-agnostic way, it offers great flexibility, but its accuracy suffers in the presence of loops. In this work, we combine BP with the DMRG
algorithm to solve ground-state problems, thereby extending DMRG to higher dimensions and arbitrary
lattices. We demonstrate the viability of BP-DMRG on the transverse-field Ising model on a $2\times 2$ hexagonal
lattice, finding that it produces states with a fidelity between $0.9$ and $0.99$ to the true ground state, and energy estimates with a relative error between $10^{-2}$ and $10^{-3}$. Additionally, BP-DMRG can find ground states on randomly generated
lattices, with fidelity improving as the transverse field increases. We conclude with a discussion of the limitations we encounter when using belief propagation, highlighting that the TFI tensor network operators lead to larger errors during BP iterations in BP-DMRG.
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Soft Condensed Matter
Collective Cell Fluidity Controls Active Prestress Transmission in Cell-Extracellular-Matrix Tissues
Liyang Wang, J. M. Schwarz and Tao Zhang
Tissues are active composites in which multicellular collectives and extracellular
matrices mechanically reorganize one another. We develop a three-dimensional micromechanical model that couples deformable, rearranging
cell clusters to a disordered network of semiflexible fibers through a dynamic, force-generating interface.
Cell clusters are represented as solid-like or fluid-like vertex-model spheroids and coupled to the
matrix by passive or contractile linkers renewed as the cluster boundary reorganizes. Matched intact, voided, and passive-linker controls separate cavity formation, interfacial tethering, and active loading. At small strain, passive tethering provides modest reinforcement, whereas active contraction prestresses and strongly stiffens the
matrix. Solid-like clusters preserve coherent force transmission and exhibit an excess modulus scaling approximately as $|\sigma|^{1.4}$ across changes in activity, cluster size, and cluster number. Fluid-like clusters undergo greater interfacial renewal, producing weaker and nonmonotonic coupling between prestress and stiffness. Increasing cluster number produces collective stiffening when prestressed regions become connected through sufficiently persistent interfaces. At large strain, both solid-like and fluid-like systems approach the corresponding voided-network response as the residual fiber backbone becomes mechanically dominant. Thus,
cell-generated prestress controls macroscopic stiffness only together with the organization and persistence of its transmission across the
cell-
matrix interface.
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High Energy Physics (Phenomenology)
Recoil Geometry Unmasks Gluon Saturation in Forward $Z^0$ Production
Wanchen Li, Ding Yu Shao, Shu-Yi Wei et al. (+1 more)
Gluon saturation produces characteristic transverse-momentum broadening in
nuclei, but QCD radiation largely washes out this signature. We show that fiducial
recoil subtraction turns detector acceptance into a transverse-momentum projector that unmasks the broadening in forward $Z^0$ production. Subtracting the hadronic
recoil measured in a chosen rapidity interval from the
boson transverse momentum defines a residual momentum. At leading power, the radiative
recoil in this interval cancels, while the residual momentum retains sensitivity to the small-$x$
nuclear field. Combining a CGC description of the small-$x$ target with soft-collinear effective theory (SCET) resummation for finite rapidity coverage, we find that a
benchmark rapidity coverage $|\eta^{\rm lab}|<2.5$ lowers the effective hard scale from $M_Z\simeq 91.2$ GeV to about $7.5~\mathrm{GeV}$ of the Sudakov
evolution. Increasing the saturation scale broadens the residual-momentum distribution and weakens
recoil alignment, whereas wider coverage makes the
proton–
nucleus separation clearer in both observables. Detector geometry thus provides tunable control over perturbative
recoil, enabling a probe of nonlinear small-$x$ QCD.
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All authors Wanchen Li, Ding Yu Shao, Shu-Yi Wei, Jian Zhou
Statistical Mechanics
Effect of reactive targets on diffusive transport with intermittent restarts
Samali Ghosh, Suvam Pal, Dibakar Ghosh et al. (+1 more)
We study search processes in a complex environment using the strategy of
stochastic resetting. A common occurrence in these environments is targets with finite reactivity.
Stochastic resetting has emerged as a powerful mechanism for optimizing search processes by curtailing long, unproductive excursions inherent to diffusive dynamics. Most theoretical studies, however, assume perfectly absorbing targets – an idealization that overlooks the finite reactivity commonly encountered in realistic chemical and biological systems. In this work, we investigate the interplay between
stochastic resetting and finite-target reactivity in reaction -
diffusion processes. Considering a one-dimensional system with multiple reactive targets, we demonstrated that the target reactivity modifies the optimization landscape. We uncover distinct regimes in which resetting enhances transport efficiency towards specific targets based on their chemical kinetics. As a consequence, the optimal resetting rate becomes intrinsically reactivity dependent. Our results identify target reactivity as a crucial control parameter governing
stochastic transport and provide insights into reaction-
diffusion processes in complex media.
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All authors Samali Ghosh, Suvam Pal, Dibakar Ghosh, P. S. Pal
Statistical Mechanics
Nonequilibrium corrections to conserved Ising criticality in scalar active matter: Ward identities, spectrum, and long crossovers
Piotr Zdybel
We identify the slowest-decaying nonequilibrium perturbations near the three-dimensional conserved Ising critical point and determine their impact on finite-size observables. We study two classes of perturbations: a field-dependent noise-to-mobility ratio $\Theta(\phi)=D(\phi)/M(\phi)$ and the gradient activity of Active Model B+. Starting from the Martin-Siggia-Rose-Janssen-De Dominicis action, we compute the linearized flow using the functional renormalization group. The transport sector is block triangular, with leading odd
eigenvalue $y_{\Theta_1}=-\Delta_\phi$, where $\Delta_\phi=(d-2+\eta)/2$. In the gradient sector, removing the detailed-balance direction leaves two genuinely nonequilibrium modes, chemical and current-like. Two smooth regulators give $y_{\Theta_1}\simeq-0.52$, $y_J\simeq-0.56$, and $y_{\rm ch}\simeq-0.89$. A translation Ward identity expresses the current operator as the divergence of the stress tensor. Together with conservation and Itô causality, this forbids chemical operators from generating the current mode, making the nonequilibrium stability
matrix triangular; an independent two-loop calculation in $d=4-\varepsilon$ finds no additional current contact counterterm. Within the FRG truncation, $y_J-y_{\Theta_1}=-\eta$; beyond it, this relation requires the absence of an additional contact anomaly. Using the 3D Ising value $\eta=0.0362978(20)$ [Kos et al., 2016] gives $y_{\Theta_1}\simeq-0.5181$ and $y_J\simeq-0.5544$. Because these exponents nearly coincide, single-power fits yield amplitude-dependent apparent exponents and crossover lengths may exceed accessible system sizes. We derive the resulting finite-size scaling rules: odd block observables respond linearly to activity, while even observables receive only quadratic corrections.
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