High Energy Physics (Phenomenology)
Estimation of the cumulant $b_4$ and sextic self-coupling of the QCD axion at finite temperature and density
Xinguang Li and Zhao Zhang
The sixth-order cumulant $b_4$ of the QCD topological charge distribution and the
axion's sextic self-coupling at finite temperature $T$ and
baryon chemical potential $\mu$ are calculated within the two-
flavor quark-
meson (QM) model without and with the Polyakov-loop dynamics. The $b_4$ in the
vacuum falls within the range predicted by
lattice SU(3) pure-gauge simulations, and at large $T$ and/or $\mu$, it tends to a constant predicted by the dilute instanton gas approximation. Both $b_4$ and the
axion's sextic self-coupling diverge at the QCD critical point and flip sign across the phase transition. The convergence of the fourth- and sixth-order Taylor expansions of the free energy as a function of the $\theta$ parameter is investigated via comparison with the full potential at the mean-field level.
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Solar and Stellar Astrophysics
Planetary systems in the light of asteroseismology: metallicity threshold for the planetary systems and age-metallicity relation
M. Y{\i}ld{\i}z, A. Demirkol, S. Örtel et al. (+2 more)
We compiled data for 127 hosts (plus six candidates) and used them as constraints to construct interior models of the hosts using the {\small MESA} code. Two significant conclusions emerge from these models. First, except for a few
stars, the hosts'
metallicity ($Z_0$) is greater than 0.007. This suggests a possible suppression of the occurrence of
planets below $Z_0\approx0.007$. Second, it concerns how chemical
evolution unfolds in the
galactic disc. For a given $Z_0$ value, considering the oldest
stars, there is a linear relationship between $Z_0$ and age ($t_9$). This line is around $t_9=13.4$ Gyr at $Z_0=0$, a value consistent with the age of the
Galaxy. The linear relationship continues until around $t_9=6$ Gyr, and the maximum value of $Z_0$ remains constant between $t_9=2-6$ Gyr. We further modelled 12 hosts classified as red clump (RC)
stars in the literature, explicitly accounting for mass loss along the red
giant branch. These models highlight the critical role of mass-loss assumptions in determining the initial masses and ages of RC hosts, and their implications for the survival and
evolution of close-in
planets. Another key outcome of this study is the discovery of the relationship between $Z_0$ and the observed
metallicity ($Z_{\rm s}$) for the hosts. We obtain a useful expression for $Z_0$, the input parameter for the models, as a function of
stellar mass, radius, and $Z_{\rm s}$. This expression can be used to estimate $Z_0$ based on the reduced surface
metallicity due to microscopic
diffusion. We also derive an expression for planetary mass relative to the orbital semimajor axis and host mass. This expression may indicate a mass distribution near the inner disc where these
planets formed, except for hot-Jupiters.
Planet radii appear to depend on the
planet's mass and irradiation energy, as well as the orbital period.
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All authors M. Y{\i}ld{\i}z, A. Demirkol, S. Örtel, T. Çak{\i}r Alsaç, T. Daylan
Mesoscale and Nanoscale Physics
Morphology-Guided Deterministic Fabrication of Low-Noise High-Temperature Superconducting Quantum Interference Devices
Bingke Xiang, Wanjuan Tang, Shiqun Liu et al. (+9 more)
Reproducible bicrystal high-temperature superconducting
quantum interference devices remain limited by local variability along the grain boundaries that form the Josephson junctions. Here, we develop a site-selective fabrication workflow in which atomic force microscopy maps the intended junction region before lithography, quantifies an apparent grain-boundary width, rejects pore-rich segments, and writes a nearby registration mark for site-specific pattern
alignment. The apparent grain-boundary width provides a practical morphology metric, with narrower regions consistently yielding larger critical currents and characteristic voltages. Iterative optimization within this workflow further improves junction and device performance, reaching a
liquid-nitrogen-temperature field-noise level of 40 fT Hz^(-1/2). This strategy turns local grain-boundary heterogeneity from an uncontrolled source of variability into a basis for site-selective fabrication, providing a route towards scalable manufacturing of low-noise HTS SQUIDs with high uniformity.
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All authors Bingke Xiang, Wanjuan Tang, Shiqun Liu, Lingtong Hou, Geming Zhang, Yibo Wang, Ruonan Wang, Zhiqiang Cao, Jiaqi Wei, Xueshen Wang, Xueying Zhang, Xiaoyang Lin
Materials Science
Strain-stabilized altermagnetism and conductivity anisotropy in FeSb2
Masoumeh Davoudiniya, Alyssa M. Kennedy, Amy Y. Liu et al. (+1 more)
We show that FeSb2 experiences a transition from a conventional antiferromagnet to an altermagnet when tensile strain is applied. In the altermagnetic phase, the lifted Kramers degeneracy results in
spin splitting up to ~0.2eV near the
Fermi level even without
spin-orbit coupling. The transition to the altermagnetic phase is accompanied by a dramatic change in the
Fermi-surface geometry, which leads to a uniaxial conductivity anisotropy up to ~60%, much greater than those observed in typical
ferromagnetic metals. Using density-functional theory and Wannier interpolated
Fermi surfaces, we show that this magnetotransport behavior may function as an experimental indicator of the transition to the altermagnetic phase. These findings highlight FeSb2 as a versatile, strain-tunable platform for exploring and utilizing altermagnetic transport phenomena for spintronic devices.
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All authors Masoumeh Davoudiniya, Alyssa M. Kennedy, Amy Y. Liu, Gen Yin
Fluid Dynamics
Compressibility Driven Wake Transition and Hysteresis over Cargo Aircraft Aftbodies
Chitrarth Prasad, Rajesh Ranjan, Daniel J. Garmann et al. (+1 more)
Aft sections of military cargo aircraft employ flat surfaces at high upsweep angles to accommodate ramp doors, producing flow features that affect cargo-drop accuracy, paratrooper safety, and aerodynamic performance. Fundamental studies have primarily examined near incompressible flow over a canonical surrogate consisting of a freestream aligned cylinder with a planar, sharp edged upswept base. The flow exhibits peripheral separation, a horseshoe
vortex, and a counter-rotating streamwise
vortex pair that persists downstream. The present investigation delineates the effects of compressibility on the wake and examines how these effects depend on basal upsweep angle. Wall-resolved large-eddy simulations are performed at Mach numbers of $0.1$, $0.3$, and $0.5$ for upsweep angles of $32^\circ$ and $45^\circ$ at a nominal Reynolds number of $25{,}000$. For the $32^\circ$ afterbody, increasing Mach number enlarges the upstream recirculation region and delays
vortex-pair formation, while these effects diminish downstream. For the $45^\circ$ afterbody, similar recirculation-region growth triggers a bifurcation at Mach~0.5 from the
vortex-pair state to a broad separated turbulent wake. A descending-Mach sequence to 0.3 and 0.1 reveals hysteresis, with the separated-wake state persisting at lower Mach numbers and remaining robust to Reynolds-number variation. Thus, both states can occur at identical Mach and Reynolds numbers, with
topology and pressure loading governed by Mach number history.
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All authors Chitrarth Prasad, Rajesh Ranjan, Daniel J. Garmann, Datta V. Gaitonde
Quantum Physics
Geodesic Quantum $f$-Divergences
Ángela Capel and Pablo Costa Rico
We introduce the geodesic
quantum $f$-divergences $D_f^t$, $0\leq t\leq1$, obtained from the affine-invariant geodesic between the standard and maximal relative modular operators. They reduce to the classical $f$-divergence for commuting states. The logarithmic generator yields geodesic relative
entropies joining the Umegaki and Belavkin-Staszewski
entropies, while the power generators yield $(t,\alpha)$-Rényi divergences joining the Petz and
geometric families. Our first main result is data processing of $D_f^t$ for every finite operator-convex generator $f$ and every $t\in[0,1]$. In particular, this gives DPI for the geodesic relative
entropies and for the $(t,\alpha)$-Rényi divergences when $0<\alpha<1$ or $1<\alpha\leq2$. Our second main result identifies equality in the DPI: for invertible states, every equality-determining operator-convex generator has, at each nonmaximal parameter $0\leq t<1$, exactly the Petz sufficiency class; at $t=1$, this changes to the generally larger maximal, or BS, class, which also coincides with the equality class of the divergences associated with the quadratic generator for every $t$. Our third main result is the corresponding collapse of invertible geodesic
quantum Markov chains: for each of the three ordered conditional-mutual-information constructions, the $t$-
quantum Markov chains are precisely the
quantum Markov chains for $0\leq t<1$, whereas at $t=1$ they are the invertible BS
quantum Markov chains, a class that can be strictly larger. We also determine parameter-monotonicity regimes and the intersections with the $(\alpha,z)$ family. We prove strengthened data-processing and reconstruction estimates; we compare the three conditional orientations; we establish continuity bounds under positive lower-
eigenvalue assumptions together with complementary discontinuity results; and we give a capacity-per-unit-cost interpretation.
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Quantum Physics
Topologically Protected Learning from Exceptional Point Braiding: Toward Braid Programming
M.N. Jipdi, C. Avomo Mba, A. B. Moubissi et al. (+2 more)
We present a framework for topological learning based on exceptional point (EP) braiding in a non-Hermitian Bogoliubov-de Gennes
Hamiltonian. A closed algebraic equation for the EP super-surface is derived; through momentum quantisation in finite systems, it predicts the exact number and parameter positions of all EPs in real space, irrespective of system size. The EP
topology is characterised by two quantised invariants the state-swap fidelity and the normalised Berry phase which cannot both be zero for a topological EP. A complete topological map shows that all EPs lie within a specefic region. Adiabatic encirclements confirm robust state swapping and yield a universal set of braid gates, including Pauli-X, Pauli-Y, Pauli-Z, a Hadamard-like gate, the T-gate, and a SWAP operation, with the special case where a is 0, providing additional phase gates. Building on these generators, we reformulate learning as braid programming a discrete search over the braid group that replaces gradient descent on continuous weights with combinatorial optimisation. A proof-of-concept genetic search successfully discovers short braid words that reproduce the standard Hadamard gate and the H.Z gate with perfect fidelity. This paradigm offers inherent noise immunity, catastrophic-forgetting prevention through compositional concatenation, and guaranteed generalisation by mathematical construction, establishing EP braiding as a promising substrate for robust, interpretable, and topologically protected neuromorphic computation.
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All authors M.N. Jipdi, C. Avomo Mba, A. B. Moubissi, L.C. Fai, M.E. Ateuafack
Quantum Physics
Resource Analysis for Quantum Simulation of Spatially Varying Transport-Reaction Equations
Benjamin Jasperson, Krishna Garikipati and Siddhartha Srivastava
Spatially varying coefficients are the primary source of
circuit complexity in
quantum simulation of linear advection-
diffusion-reaction equations. This work presents a resource analysis of single-step
quantum propagators constructed using sparse FABLE block encodings,
Quantum Singular Value Transformation, and linear-combination-of-
unitaries. We derive theoretical estimates for
qubit count, gate complexity, and
circuit depth in terms of the spatial discretization, sparsity, and
polynomial degree, and compare these predictions with synthesized
quantum circuits for one- and two-dimensional variable-coefficient problems. The resulting analysis quantifies the cost of encoding realistic transport operators and provides practical resource estimates for near-term implementations.
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Applied Physics
On-chip nanoplasma for adaptive electromagnetic protection
Ruiqi Huang, Hanqing Liu, Kui Dang et al. (+12 more)
Over the past decade,
semiconductor diodes have served as the primary switching elements in adaptive electromagnetic (EM) protection, yet their performance has been compromised by parasitic effects and thermal accumulation, rendering them inadequate against the rapidly evolving landscape of high-power microwave (HPM) threats. Here we show that on-chip nanoplasma switches (NPMS), composed of gallium nitride electrodes on silicon carbide substrates, exhibit superior
radio frequency (RF) and thermal characteristics, positioning them as ideal field-driven switches in RF front-end protectors. By integrating NPMS into metasurfaces,
antennas and
circuit limiters, we achieve an adaptive response that ensures low-loss transmission for normal signals and high shielding against HPMs, while offering extended operating bandwidth and substantially higher tolerance than conventional solid-state devices. This robust, nanoscale structure has significant potential for protecting unmanned aerial vehicles, radars, satellites and other highly integrated platforms requiring strength and stability in EM environments. The findings of this study open up new routes to support EM safety of high-precision detection and imaging for next-generation RF front ends, with straightforward scalability to millimetre-wave and terahertz frequencies.
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All authors Ruiqi Huang, Hanqing Liu, Kui Dang, Yue Lang, Ruiyang Peng, Qihui Zhou, Qian Dong, Xiaocheng Ni, Yuan Xu, Jibin Liu, Yanlin Xu, Chenxi Liu, Song Zha, Jincheng Zhang, Peiguo Liu
Strongly Correlated Electrons
Topological Altermagnetic Insulators
Jasmin Bedow, Nitin Kaushal and Marcel Franz
We study the emergence of altermagnetic topological phases stabilized by Ising
spin-orbit coupling in a prototypical Lieb
lattice model of a correlated altermagnet. Treating the electron interactions within the Hartree-Fock and the exact diagonalization techniques, we establish the co-existence of a
quantum spin Hall effect with altermagnetic
spin order over a wide region of the parameter space for average electron densities of 2 and 4 per unit
cell. We explore how the
magnetic structure along edges influences the electronic behavior of the associated topological edge modes, demonstrating their robustness against inversion-
symmetry breaking terms.
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Quantum Physics
Longitudinal-Field-Driven Transition in a non-integrable Non-Hermitian Transverse-Field Ising Chain via RBMs
M.E. Ateuafack, M.R. Kamsap, J.T. Diffo et al. (+2 more)
We investigate the ground-state properties and
quantum critical behavior of a non-Hermitian transverse-field Ising chain subjected to longitudinal and complex transverse
magnetic fields. To address this interacting many-body problem, we employ real-valued neural
quantum states based on Restricted Boltzmann Machines (RBMs), optimized using Variational Monte Carlo (VMC) sampling. Spectral analysis of finite chains reveals exceptional points associated with spontaneous parity-time (PT)
symmetry breaking. A real-valued RBM framework is developed to reconstruct the ground-state eigenstates of the non-Hermitian
Hamiltonian.
Benchmark comparisons with exact diagonalization demonstrate that the RBM approach accurately reproduces the ground-state energy, magnetization, and
spin-
spin correlations. Extending the analysis to larger system sizes, we identify a non-Hermitian
quantum phase transition characterized by PT-
symmetry breaking and the emergence of
magnetic order. Our results establish real-valued neural
quantum states as an efficient and scalable framework for investigating critical phenomena in interacting non-Hermitian
quantum systems.
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All authors M.E. Ateuafack, M.R. Kamsap, J.T. Diffo, L.C. Fai, M.N. Jipdi
Mathematical Physics
Quantized Bertrand models on two-dimensional spaces of constant curvature
Agnieszka Martens
Discussed are Bertrand systems on two-dimensional spaces of constant
curvature, i.e. sphere and pseudosphere (Lobachevsky space). These models often involve applying quantization techniques, such as those based on the Laplace-Beltrami operator, to the classical models and analyzing the resulting
quantum behavior.
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Strongly Correlated Electrons
Linear response functions from inhomogeneous dynamical mean-field theory
Don Rolih and Fabian B. Kugler
We present a method for calculating static
lattice susceptibilities with inhomogeneous dynamical mean-field theory. The method utilizes the response of the system to an external field and thereby circumvents two-particle vertex functions. We demonstrate the success of our approach for the
magnetic susceptibility of the square-
lattice Hubbard model using the numerical renormalization group as an
impurity solver and show that it compares well with the results obtained using the standard vertex approach. As it avoids vertex functions and is compatible with virtually any
impurity solver, our method is able to reach low temperatures that are hard to access with other methods.
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Quantum Physics
Experimental High-Dimensional Quantum Overlapping Tomography
Haifei Wang, Rui Qu, Zhengning Yang et al. (+7 more)
Large-scale
quantum systems have advanced rapidly via the exploration of more particles and higher dimensions, offering great potential for developing
quantum technologies. However, their characterization becomes prohibitive with increasing local dimensionality and particle number. Here we propose high-dimensional
quantum overlapping
tomography based on a graph-theoretic formulation, which allows one to efficiently reconstruct few-body marginals of multipartite high-dimensional
quantum systems. We experimentally realize it on a photonic four-party entangled state in a $4 \times 4 \times 2 \times 2$ system. Using measurements in mutually unbiased bases, we reconstruct all six two-body marginals with only 25 projective measurement settings, compared with 94 and 225 settings for independent
tomography of all two-body reduced states and full state
tomography, respectively. The reconstructed marginals reveal a layered
entanglement structure vital for high-dimensional
quantum networks. We further show that these marginals enable more noise-resilient certification of multipartite high-dimensional
entanglement than the fidelity-based criterion. Our work thus offers a scalable route for learning multidimensional
quantum systems.
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All authors Haifei Wang, Rui Qu, Zhengning Yang, Xiaodan Lyu, Haotao Zhu, Zitong Xu, Lianzhen Cao, Joel Yang, Otfried Gühne, Weibo Gao
General Relativity and Quantum Cosmology
Hawking Radiation and Second-Order Quantum Corrected Thermodynamics with Black Hole Remnant Formation in a Vaidya-Bonnor Black Hole Surrounded by Quintessence
Djedai Ayang Kamo, Saleh Mahamat, Ragil Brand Tsafack Ndongmo et al. (+3 more)
In this work, we investigate Hawking radiation and second order
quantum corrected thermodynamics of a Vaidya-Bonnor black hole surrounded by quintessence. Within the Hamilton-Jacobi tunneling formalism, analytical expressions for the event horizons, tunneling probability, and Hawking temperature are derived by treating the quintessence field as a perturbative contribution. The classical thermodynamic quantities, including
entropy, heat capacity, enthalpy, Helmholtz free energy, and Gibbs free energy, are then obtained and analyzed.
Quantum thermal fluctuations are incorporated through logarithmic and inverse-
entropy corrections to the Bekenstein-Hawking
entropy, leading to second-order corrected thermodynamic quantities. Their effects on thermal stability and phase transitions are examined in detail. Furthermore, analytical expressions for the
quantum-corrected remnant radius and remnant mass are derived, showing that the combined effects of quintessence and
quantum corrections can prevent complete black hole evaporation and lead to the formation of a stable remnant. Our results show that both quintessence and higher-order
quantum corrections enhance thermodynamdymic stability and significantly favor the formation of stable black hole remnants.
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All authors Djedai Ayang Kamo, Saleh Mahamat, Ragil Brand Tsafack Ndongmo, Kamiko Kouemeni Jean Rodrigue, Thomas Bouetou Bouetou, Timoleon Crepin Kofane
Mesoscale and Nanoscale Physics
The Hodge structure of Berry-phase transport: topology, geometry, and noise
Zhi-Wei Wang and Samuel L. Braunstein
We show that the Hodge-de Rham decomposition of the Berry
curvature organises the transport of a Bloch band and its fluctuations within a single
geometric structure. Splitting the
curvature into $L^2$-orthogonal harmonic, exact, and co-exact sectors yields a dictionary for both moments of the current. In the mean response the harmonic sector carries the topological anomalous-
Hall conductivity, the exact sector the
Fermi-surface geometry and the antisymmetric Berry-
curvature dipole of polar metals, and, in three dimensions, the co-exact sector the
chiral anomaly, quantised by the Weyl-node charges. In the fluctuations, described by a particle-conserving
stochastic Boltzmann equation constrained by the fluctuation-dissipation
theorem (FDT), the harmonic sector is silent, so topological transport is noiseless, while the field-driven noise is sourced by the
geometric sectors (solely the exact sector in two dimensions); current-noise spectroscopy therefore separates global band
topology from local band geometry. We prove that the harmonic null-space protection is dimension-independent, and we settle the remaining sector: the co-exact (monopole) sector carries no conservation law and, under the thermal sampling measure, mixes with the exact sector at $\mathcal{O}(1)$, so it furnishes no clean noise observable. The separation the noise provides is therefore two-way,
topology versus geometry, in both two and three dimensions.
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Astrophysics of Galaxies
The Low-Mass Baryon Cycle in QUEST Dwarf Galaxies I: Sample definition and first results
Ava Polzin, Hsiao-Wen Chen, Zhijie Qu et al. (+3 more)
We introduce the QUEST
Dwarfs program, which connects low-mass
galaxies'
stellar populations, interstellar medium, and circumgalactic medium in a large and coherently analyzed sample using a combination of optical spectroscopy, broadband imaging, and FUV absorption spectra of bright background sources .We present initial results from the first-release sample, comprising 14
galaxies with
stellar mass $M_\mathrm{star} \leq 10^9 M_\odot$ at $z\approx0.001-0.017$, each with at least one CGM absorption probe at projected distances $d_\mathrm{proj}\lesssim 100$ kpc. This representative sample triples the number of available probes within 1/3 of the
halo radius of
dwarf galaxies outside of the Local Group. We find that the total silicon column density declines much more rapidly with projected distance than Hi, implying that chemically enriched cool gas is preferentially concentrated in the inner CGM, while the increasing ionization fraction of hydrogen with radius likely enhances this contrast. Accounting for unobserved silicon in higher ionization stages, we infer total metal masses of $\log M_Z/M_\odot\approx4.8$ and $6.5$ in the cool CGM within $0.3 R_\mathrm{vir}$ for
dwarfs with median $\log M_\mathrm{star}/M_\odot=7.6$ and 8.6, respectively. These reservoirs correspond to $\approx3$% and $\approx16$% of the total metals produced over the
galaxies' lifetimes. More massive
galaxies also exhibit systematically stronger metal absorption, suggesting that projected distance governs the radial decline of metal absorption while
stellar mass sets the normalization of the CGM metal profile. Individual ions reveal a multiphase structure, with low-ionization species concentrated in the inner
halo and higher-ionization species extending farther. The full QUEST
Dwarfs survey will provide the statistical power needed to isolate the dominant drivers of CGM enrichment in low-mass
halos.
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All authors Ava Polzin, Hsiao-Wen Chen, Zhijie Qu, Erin Boettcher, Allison Strom, Tsang Keung Chan
Chemical Physics
Gas-generating reactive flows in bicontinuous catalyst support structures
J.M.P. Beunen and J. Harting
A major challenge in the field of heterogeneous catalysis is selecting an optimal catalyst support structure. Commercially available structures can be easily manufactured at scale, but their
stochastic nature makes their chemical and transport properties suboptimal. This is particularly relevant for gas-generation reactions, where non-uniformity of a porous structure leads to bubble trapping. Such trapping impedes the flow of reactants to catalyst sites, leading to conversion inefficiencies. Previous experimental work demonstrated that spinodally-derived architectures, in particular bicontinuous interfacially jammed emulsion gels (bijels), can alleviate these issues and deliver superior performance. However, to the best of our knowledge, numerical studies to optimize the operating conditions for such a morphology have not been performed yet. In this work, we aim to close this gap using color-gradient
lattice Boltzmann simulations of reactive flows with a novel central moments collision operator. We develop an analytical model to predict catalyst performance based on our simulation data. Our findings show that this type of morphology can achieve very high conversion efficiencies. Moreover, we demonstrate that its catalyst performance can be optimized using superhydrophilic surface coatings.
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Materials Science
ALKEMIE Agent: an autonomous platform for computational materials design
Hongfu Huang, Yuzhe Li, Ao Xu et al. (+14 more)
Despite the powerful multi-scale modeling methods and high-throughput infrastructures established in the materials community, real material computation workflows remain fragmented and heavily manual, requiring researchers to constantly bridge software tools, data analysis, and intermediate decisions. This growing gap between methodological capability and practical execution highlights the need for a new kind of autonomous computational framework, one that can coordinate tools, knowledge, and workflows in a more unified and adaptive way. Here, we introduce ALKEMIE
Agent, an agentic platform in which
retrieval-augmented generation, a materials-computation knowledge base, registered skills, database-supported provenance, AI-assisted structure modeling, bounded task execution, tool-calling iteration, and error-diagnostic assistance are integrated within a traceable control loop. The capabilities of ALKEMIE
Agent are demonstrated through applications including materials recommendation, structure modeling,
phonon calculations, machine-learned interatomic potential training, LAMMPS simulations, Ab Initio Monte Carlo (AIMC) sampling, and active-learning-based materials screening. Finally, we outline the future directions and challenges for the development of agentic platforms for computational materials design.
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All authors Hongfu Huang, Yuzhe Li, Ao Xu, Bo Liu, Changrui Wang, Kan Tang, Ning Yang, Shengxian Liu, Hanyu Liu, Pengpeng Zhang, Linggang Zhu, Fengkai Liu, Yichen Lu, Tong Zhao, Naihua Miao, Jian Zhou, Zhimei Sun
Optics
Burst-Driven Collective Ultrafast Interactions for Confined Optical Absorption
Burak Aray{\i}t, Seydi Yavaş, Mehmet Burçin Ünlü et al. (+1 more)
Ultrafast bursts, groups of closely spaced femtosecond pulses, can drive light-matter interactions that are not possible with single-pulse excitations. This occurs when earlier pulses create a transient effect that nonlinearly alters the interaction of later pulses, provided that the inter-pulse spacing is shorter than the relaxation time of the transient. A long-standing trade-off in optical excitation is between multiphoton absorption, which provides strong spatial confinement but low energy-transfer efficiency, and linear absorption, which is efficient but offers limited spatial localization. Here, we show that a burst of ultrafast pulses can collectively build up a population of free carriers in
semiconductor nanoparticles via multiphoton absorption. The free carriers absorb linearly and strongly, and dissipate rapidly once the burst ends. The result is a more efficient absorption process that is strongly gated spatially and temporally by multiphoton absorption and burst duration, respectively. We develop an analytical model that couples carrier generation with Auger and surface recombination, yielding a piecewise-exact description of the carrier dynamics and an intuitive scaling relation for the collective energy-deposition enhancement. A signature consequence of collective absorption is its dependence on one extra power of the light intensity, effectively raising the order of an m-
photon process to m+1 without requiring higher intensities for the individual pulses. While we focus on nonlinear photoacoustic imaging as a potential application, we anticipate diverse applications, including nonlinear fluorescence microscopy.
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All authors Burak Aray{\i}t, Seydi Yavaş, Mehmet Burçin Ünlü, Fatih Ömer Ilday
Optics
Infrared light scattering and emission from epsilon near-zero hyperbolic phonon-polaritons in two-dimensional crystals
Flavio Henrique Feres, Martin Bearzatto, Adrien Debacq et al. (+24 more)
This work presents the near-field super-scattering and the near-field thermal emission from 2D
hyperbolic crystals as general optical phenomena that link near-field nanophotonics to far-field photonics.
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All authors Flavio Henrique Feres, Martin Bearzatto, Adrien Debacq, Gergely Nemeth, Rafael A. Mayer, Yuri B. Marcal, Marcus V. de Paiva, Maximilian Obst, Felix Kaps, Jakob Wetzel, Osama Hatem, Wenjun Zhou, Ran Jing, Heng Whang, Adrian Cernescu, Stephan Winnerl, J. Michael Klopf, Mengkun Liu, Ferenc Borondics, Ingrid D. Barcelos, Raul O. Freitas, Ana I. F. Tresguerres-Mata, Yannick De Wilde, Lukas M. Eng, Michaël Lobet, Susanne C. Kehr, Francisco C. B. Maia
Materials Science
Design of altermagnetism in oxide superlattices exploiting interface effects and quantum confinement
Subhadeep Bandyopadhyay and Rossitza Pentcheva
The discovery of altermagnetism has initiated intensive research and opened new avenues for
spin- tronic and transport applications. While current efforts are mostly focused on bulk materials which are typically insulating, here we propose design strategies to achieve a combination of altermag- netism and
metallicity in
oxide superlattices by exploiting
symmetry breaking, electrostatic doping and confinement. While bulk SrCrO3 does not exhibit altermagnetism due to compensating effects between adjacent layers our density functional theory calculations with a Hubbard U parameter re- veal, that a single SrCrO3 layer confined in a (SrCrO3)1/(SrTiO3)1(001) superlattice (SL) exhibits a sizable non-relativistic
spin splitting (NRSS) up to 350 meV with bulk d-wave nature due to the coexistence of orbital ordering and octahedral rotations (OORs). Since this system is insulating, we extend to SrCrO3/LaCrO3(001) SLs. In the (SrCrO3)4/(LaCrO3)4(001) SL the combination of a polar discontinuity at the interface and stronger OORs promotes metallic d-wave altermagnetism. The NRSS of up to 120 meV is contributed by the interfacial Cr d bands at the
Fermi level with indications for a
spin-selective
Fermi surface nesting. These findings establish
oxide superlattices as a promising platform to realize and explore altermagnetism for
quantum transport and spintronic functionalities
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Quantum Physics
Machine Learning Approaches to Decoding Topological Quantum Codes
Changwon Lee, Tak Hur, Jeongwoo Jae et al. (+1 more)
Decoding is an essential component of
quantum error correction (QEC), translating stabilizer measurement outcomes into corrective actions that suppress logical errors and preserve logical
quantum information. Building fault-tolerant architectures requires increasing the code distance, which in turn places growing demands on decoding accuracy, scalability, and practical deployability. While a wide range of decoding
algorithms have been proposed and demonstrated, achieving reliable, scalable, and real-time decoding remains a significant challenge. Machine-learning (ML) approaches are particularly well suited to this setting, as
quantum error decoding is fundamentally a problem of processing large volumes of classical data with complex spatiotemporal correlations. This chapter surveys ML-based methods for
quantum error decoding, with a focus on topological codes and an emphasis on architectural principles, practical performance, and real-time considerations. We first frame decoding as a learning problem and outline key paradigms, including discriminative, generative, and reinforcement-learning formulations. We then introduce the neural network building blocks that underpin most contemporary neural decoders and discuss how these components can be integrated to balance expressivity, scalability, and latency. Building on this architectural perspective, we review recent progress and
benchmarks in neural decoding for
memory experiments, and discuss real-time decoding, open challenges, and future directions toward scalable fault-tolerant
quantum computing.
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All authors Changwon Lee, Tak Hur, Jeongwoo Jae, Daniel K. Park
Nuclear Theory
Renormalization Group Analysis of Pairing Instabilities in Nuclear Fermi Liquids
Yang Xiao, Yixin Guo and Youngman Kim
A
nuclear Fermi liquid exhibits competing pairing instabilities in different
spin, isospin, and orbital channels. In a
Fermi-surface renormalization group (RG) treatment, the channel that develops a pole first is determined not only by its tree-level attraction but also by its one-loop RG coefficient. We illustrate this mechanism in a minimal $S/P$-wave model. A spherical
Fermi surface establishes the reference competition between the lowest even- and odd-parity interactions. Axial deformation changes the relevant
Fermi-surface integrals and lifts the degeneracy between longitudinal and transverse $P$-wave components. In isospin-asymmetric matter,
neutron–
proton Fermi-momentum splitting restricts the simultaneous low-energy contribution of the two species and can terminate the $np$ running at finite threshold scales. Our calculations are intended as controlled one-loop RG illustrations rather than as quantitative
nuclear-matter calculations. We show how the
Fermi-surface geometry and composition can change the ordering of competing pairing instabilities.
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High Energy Physics (Theory)
Bootstrapping bilinear relations of discrete Painlevé systems from 5d gauge theories
Minsung Kim and Xin Wang
We study tau-functions of
elliptic and $ q $-Painlevé equations through their correspondence with 5d $ \mathcal{N}=1 $ supersymmetric field theories. Defining tau-functions associated with 5d field theories in terms of partition functions on the $ \Omega $-background, we propose a bootstrap method that determines their bilinear relations from the effective prepotential and the perturbative contributions, together with the global
symmetry of the theory. Applying the method to 5d $ \mathrm{SU}(2) $ gauge theories coupled to $ N_f \leq 8 $ fundamental hypermultiplets, we obtain the bilinear relations of the
elliptic and $ q $-Painlevé equations. This method can be applied to general 5d supersymmetric field theories beyond $ \mathrm{SU}(2) $ gauge theories.
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Quantum Physics
Designing Quantum Error Correcting Codes to fit decoders via Reinforcement Learning
Omer S. Sella, Robert Pinsler and Thomas Heinis
We present a reinforcement learning (RL) approach to the co-design of stabilizer sets of
Quantum Error Correcting Codes (QECCs) and decoders. We show how to produce a generative model that produces Bivariate Bicycle (BB) codes based on the choice of decoder. Specifically, we fix a decoder architecture and use Proximal Policy Optimisation (PPO) to train an
agent over BB codes to maximise decoder performance under a depolarising channel noise model.
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Plasma Physics
Hybrid kinetic-MHD simulation on the formation of runaway electron current plateau during a current quench process
Weimin Fu and Ping Zhu
Runaway electron (RE) generation is of great concern for high-current tokamak operations. A full-f particle-in-
cell (PIC) model for RE dynamics has been developed and coupled with the 3D nonlinear extended magnetohydrodynamic (MHD) model implemented in the NIMROD code. Our model accounts for RE generation using analytical source terms and advances the RE motion along guiding-center (GC) orbits. The model was employed to simulate the formation of RE current plateau during a disruption, in which the
plasma current becomes dominated by the RE current. The model agrees well with several RE codes based on fluid models when the RE GC drifts are ignored. For highly relativistic REs, the grad-$B$ and
curvature drifts can play a significant role in the RE generation and motion due to the increase in the safety factor profile during the current quench process.
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Mathematical Physics · Cross-listed from math.SP
Spectral determinants of flat metrics on the bielliptic genus-two locus
Victor Kalvin
We obtain a closed explicit formula for the spectral determinant of flat conical metrics on the bielliptic genus-two locus. The metrics are generated by holomorphic one-forms with two simple zeros. For a symmetric reference metric, an exact Klein-four spectral identity reduces the spectral determinant to scalar determinants on spheres and
tori; the singular anomaly formula then yields the general case. The resulting formula involves an elementary binary sextic in the coefficients of the one-form and two explicit hypergeometric areas of four-cone metrics on a quotient sphere. We apply this formula to the separating, one-node nonseparating, and simultaneous two-node degenerations of the curve and obtain complete asymptotics of the spectral determinant in all cases. The one-node degeneration has two distinct metric limits, according to whether the limiting one-form is holomorphic or meromorphic. Comparison of the cylindrical cases with the Bismut–Bost asymptotics determines the corresponding constants explicitly; in the separating case it also evaluates the relative determinant appearing in the Müller–Müller formula. As a by-product, the separating asymptotics evaluate the multiplicative constants left undetermined in earlier general conical and variational determinant formulas.
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Superconductivity
Superconducting Hydride Mg2RhH6 Experimentally Achieved at Lower Pressure
Linjing Wu, Zelong Wang, Guiqi Liu et al. (+18 more)
Although tremendous progress has been made in recent years in the field of polyhydride
superconductors, the realization of high critical temperature superconductivity still relies on formidable high pressures. Searching for superconducting hydrides at lower pressures is of particular importance. Here we report the first experimental synthesis of the Mg2RhH6, which achieves superconductivity under a significantly reduced pressure of 30 GPa. The synthesis of Mg2RhH6 proceeds via a two step process (1) preparation of the Mg2RhH5 precursor containing hydrogen atoms stabilized by covalent bonds, followed by (2) hydrogen supplementation resulting in the filling of electrons into anti bonding orbitals above 30 GPa, which was accompanied by the structural transition from RhH5 square pyramid to RhH6 octahedron. Superconductivity is achieved at 30 GPa with a Tc of 24 K, which is further enhanced to 29 K at 53 GPa, evidenced by a sharp drop of resistivity to zero and characteristic suppression of Tc under applied
magnetic fields. Our experiments prove the Mg2RhH6
superconductor to be thermodynamically stable above 30 GPa, making it the first case exhibiting a Tc of approximately 30 K at a readily accessible pressure. This study pioneers a highly promising pathway for the rational design and discovery of high temperature
superconductors within
phonon mediated BCS framework.
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All authors Linjing Wu, Zelong Wang, Guiqi Liu, Jun Zhang, Yanfeng Ge, Yuanhao Su, Runteng Chen, Hongyu Liu, Wenmin Li, Sijia Zhang, Jingcheng Zhu, Jianfa Zhao, Zheng Deng, Shaomin Feng, Jing Song, Qingqing Liu, Xiang Li, Haozhe Liu, Panpan Kong, Xiancheng Wang, Changqing Jin
General Relativity and Quantum Cosmology
Horizon singularity, energy conditions and shadows in time-dependent and spherically symmetric spacetime
Shin'ichi Nojiri, Sergei D. Odintsov, Diego Sáez-Chillón Gómez et al. (+1 more)
Some dynamical spacetime solutions that describe ultra-compact objects are analysed. We show that by turning a static spacetime that describes a one-way wormhole into a dynamical time-dependent one, a singularity might arise in general. Several well-known wormhole solutions are studied, which are shown to become singular when promoted to a time-dependent wormhole. However, we show that one can construct a dynamical wormhole free of singularities. The corresponding Lagrangian that holds such dynamical spacetimes is also reconstructed, based on a two-scalar-field model free of ghosts. Energy conditions are also analysed, which might remain satisfied for a dynamical -singular- wormhole. Finally, the
evolution of the optical appearance of such dynamical objects is simulated and compared to static solutions. Some interesting features emerge that point to a way to measure the time
evolution of dynamical objects by looking at the
photon ring structure around the object.
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All authors Shin'ichi Nojiri, Sergei D. Odintsov, Diego Sáez-Chillón Gómez, Álvaro Salazar Cuadros