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Physics

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Monday 24 August

Superconductivity

Nonequilibrium pulse dynamics and metastable latching in nonlinear kinetic inductance detectors

M. Rouble, C. Albert, P. Day et al. (+3 more)

Microwave kinetic inductance detectors are typically operated at high readout power to raise the detector signal above system noise. At sufficiently large readout power, the current-dependent kinetic inductance couples the detector response to its readout bias. Using a nonlinear resonator framework and time-domain circuit calculations, we show that the amplitude, shape, and relaxation time of the driven detector's response depend on both the absorbed energy and on the readout bias. Strongly driven bias points produce amplified, extended, and non-exponential pulse responses. Qualitative agreement between calculated and measured pulse responses indicates that these effects are dominated by the driven nonlinear resonator dynamics rather than by altered quasiparticle dynamics. Beyond resonance bifurcation, sufficiently large pulse events drive the resonator between stable branches, resulting in a metastable latched state which persists after the quasiparticle transient has decayed. The pulse energy required for branch switching is set by the readout bias, suggesting a mode of triggered detection with an in-situ tunable threshold. Although nonlinear operation requires calibration of the bias- and energy-dependent response, the enhanced pulse amplitude and duration, together with tunable latching and the ability to select these parameters via the readout operating state, are likely to be of interest for single-photon and rare-event experiments, especially those limited by amplifier or system noise.
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All authors M. Rouble, C. Albert, P. Day, M. Dobbs, H. G. Leduc, J. Montgomery

Mathematical Physics

On the Dirichlet-to-Neumann conformal invariant of bounded planar domains

Alexey Kokotov, Dmitrii Korikov and Marina Nenasheva

Using an analogue of the Mandelstam-Giddings-Wolpert diagrams, we introduce a new canonical representative of the conformal class of a bounded domain of arbitrary connectivity in $\mathbb{C}$ as a flat conical surface with geodesic boundary (a "truncated light-cone diagram", simply LC-diagram in the sequel). The space of diagrams carries natural coordinates. We derive variational formulas for the determinant of the Dirichlet Laplacian on a LC-diagram with respect to these coordinates. Then, passing to the Schottky double of the LC-diagram, making use of the Burghelea-Friedlander-Kappeler formula and the known variational formulas for determinants of Laplacians on the moduli space of holomorphic differentials, we compute the Dirichlet-to-Neumann (DN) conformal invariant $\frac{{\rm det}'\Lambda}{|\Gamma|}$ (here $\Lambda$ is the DN operator on the boundary, $\Gamma$, of a multiply connected domain and $|\Gamma|$ is the length of the boundary). The resulting formula (which uses the periods of the Schottky double of the domain only) provides an elementary counterpart to the formulas of Guillarmou and Guillopé who had expressed the DN invariant through the Ruelle and Selberg zeta-functions. Our formula agrees with the recent result of Wentworth on the asymptotics of the DN invariant as all but one boundary components shrink; we have used this result to fix the undetermined constant of integration in our formula. As a corollary, we derive an explicit formula for the determinant of the Dirichlet Laplacian in a multiply connected domain.
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Chemical Physics

Learning the Kohn-Sham map with neural operators for quasi-linear scaling density functional theory

Danish Khan, Maurice D. Hanisch, Nikolai Argatoff et al. (+3 more)

Kohn–Sham density functional theory (DFT) underpins electronic-structure simulations, but repeated orbital diagonalizations lead to cubic scaling, restricting quantum calculations to modest scales only. Eliminating these auxiliary orbitals while retaining Kohn–Sham accuracy is the central goal of orbital-free DFT, but both analytical and machine-learning methods have so far fallen short. Prior learning approaches either try to learn the variational kinetic-energy functionals, which are ill-conditioned, or directly predict the ground state, which extrapolate poorly to larger systems. Instead, we identify the Kohn–Sham map as the right learning target for orbital-free DFT. It maps a Kohn–Sham potential directly to the corresponding density and noninteracting kinetic energy, quantities otherwise obtained through an orbital diagonalization. Focusing on the density component in this work, a domain-invariant $\mathrm{SE}(3)$-equivariant Fourier neural operator learns to predict it from the potential as input on real-space grids, enabling stable quasi-linear scaling SCFs. Trained jointly on 8,504 molecules and solids, a single model generalizes to out-of-distribution organic molecules, insulators, and metals. For the first time, the same method converges SCFs across these systems without explicitly constructing Kohn–Sham orbitals, while reproducing densities, electronic spectra, and structural observables at Kohn–Sham DFT accuracy. Linear-scaling SCFs additionally allow converging magnesium dislocation densities containing up to 82,500 valence electrons on a single GPU.
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All authors Danish Khan, Maurice D. Hanisch, Nikolai Argatoff, Evan Xie, Sandeep Sharma, Anima Anandkumar

Computational Physics

Macroparticles with different weights relax to different temperatures in Particle-In-Cell simulations

Remi Lehe, Arianna Formenti, Justin R. Angus et al. (+1 more)

A distinctive feature of Particle-In-Cell (PIC) simulations is the use of macroparticles, each representing many physical particles. The associated macroparticle weight can vary from one species to another, or even from one macroparticle to another. Here we show that, when macroparticles have different weights, the plasma evolves toward an unphysical thermal equilibrium in which the temperatures are unequal: lower-weight macroparticles reach a higher temperature than physically expected, and higher-weight macroparticles a lower one. We show that this unphysical equilibrium is difficult to avoid, but that reaching it takes time, and that the associated timescale depends on the effective collisionality of the PIC algorithm. We derive an equation that predicts the full time evolution of the temperatures, in good agreement with PIC simulations, and use it to identify strategies to delay the establishment of this unphysical thermal equilibrium.
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All authors Remi Lehe, Arianna Formenti, Justin R. Angus, Jean-Luc Vay

General Relativity and Quantum Cosmology

Cosmological Evolution of the Higgs Vacuum Expectation Value in Emergent Gravity

Nazim Ruzgar Guneri and Metin Arik

In a generally covariant theory whose Lagrangian density contains no derivatives of the metric, the spacetime geometry is fixed algebraically by the scalar fields, and the simplest quadratic potential is known to generate exponentially expanding, recollapsing and big-rip cosmologies. We extend this emergent-gravity Higgs cosmology by one new spacelike scalar field - the vacuum-expectation-value generating field - coupled to the Higgs particle through the Standard Model potential, so that the electroweak vacuum expectation value becomes a dynamical quantity evolving with cosmological time. We show that the broken-symmetry valley of the potential is an exact and stable solution of the full nonlinear system, on which the background is solved in closed form in terms of a single conserved charge. The charge feeds the Friedmann equation with a radiation-like component of purely geometric origin, diluting with the inverse fourth power of the scale factor although no radiation fluid is present; as a consequence the universe is born at a finite cosmological time in a radiation-dominated big bang, and for vanishing constant term in the potential the expansion history realizes a spontaneous radiation-to-dark-energy sequence. The sign of the Higgs kinetic term is not an assumption of the model: the requirement that the broken phase be the physical vacuum fixes it dynamically, and the stable choice reproduces the Standard Model relation between the Higgs mass, the self-coupling and the vacuum expectation value with no adjustable parameter. Oscillations about the valley describe a Higgs condensate which is frozen at early times, begins to oscillate through a misalignment mechanism, obeys a parameter-free adiabatic amplitude law, and backreacts on the expansion history as a definite renormalization of the background constants that feeds the radiation-like component.
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Mathematical Physics

Hartree–Fock coercivity for twisted bilayer graphene

Kevin D. Stubbs and Maciej Zworski

We study the minimisers of the Hartree–Fock functional for flat bands in the chiral model of twisted bilayer graphene introduced by Tarnopolsky, Kruchkov, and Vishwanath. Our model is a continuous version of the discrete model considered by Becker, Lin and Stubbs in previous works and the first result is a direct analogue of main theorems of those papers: at half filling of the flat band of multiplicity two, there are exactly two minimisers, obtained by occupying either one of the two sub-bands. (A more general version of this result, stressing its topological origins, was presented in Appendix A.8 of the Lecture Notes by Tao-Zworski.) The new contribution is the strict coercivity of the Hessian of the Hartree–Fock functional at the two minimisers. It is a consequence of the difference between the Chern numbers of the component bands and can be optimistically considered as a soft version of a “spectral gap”.
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General Relativity and Quantum Cosmology

Amplification of metric perturbations by extremal horizons

Samuel E. Gralla and Sepehr Salamat

Under normal circumstances, an observer falling into a black hole feels nothing special upon crossing the horizon. In this paper we find an intriguing exception: For most of the parameter range of the extremal Kerr-Newman (KN) spacetime, horizon co-rotating perturbations are enhanced near the horizon, such that an infalling observer experiences an anomalously large tidal deformation as they enter the black hole. Such perturbations arise when there is a persistent source outside the black hole that is either co-rotating itself or has discrete Fourier support at the associated frequencies $\omega=m\Omega_H$ (where $m$ is the azimuthal number and $\Omega_H$ is the horizon frequency). The enhancement is formally infinite at precise co-rotation, and we work with a nearly co-rotating mode to keep perturbation theory under control. The underlying physics is the emergence of discrete self-similarity in the extremal limit, with complex scaling weights of the form $-1/2\pm i\alpha$ for real $\alpha$. It is analogous to the black hole Meissner effect, except that the near-horizon field is enhanced rather than screened. We numerically calculate the scaling exponents for coupled gravitoelectromagnetic (GEM) perturbations of extremal KN black holes and show that the complex exponents arise in the parameter range $Q < Q_*$ with $Q_*\approx.93M$. These exponents also predict the decay and growth rates (Aretakis effect) of generic GEM perturbations of the KN spacetime, both on and off the horizon. The enhancement of co-rotating perturbations can be viewed as a driven Aretakis instability.
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Chemical Physics

Differential Learning for Robust Prediction of Thermal Stability with Application to Energetic Materials

Megan C. Davis, R. Seaton Ullberg, Jeremy N. Schroeder et al. (+5 more)

Predicting thermal stability during handling and storage is essential for the design of safe and reliable energetic materials. However, experimental measurements vary significantly across laboratories due to differences in protocols and analysis methods, making it difficult to train reliable predictive models. We address this challenge through differential learning. Rather than predicting absolute decomposition temperatures, we instead train message passing neural networks to predict relative differences between pairs of molecules. This approach reduces sensitivity to systematic experimental errors and achieves >85% accuracy in ranking compounds by thermal stability, outperforming conventional regression methods on the same heterogeneous dataset. To understand what drives these predictions, we compare neural network models with interpretable alternatives built from descriptors derived from ab initio calculations and cheminformatics software. This analysis identifies bond dissociation enthalpy as a key determinant of thermal stability rankings, providing further insight into the complex chemistry of thermal decomposition. The differential learning framework generalizes across model architectures, from graph neural networks to classical descriptor-based approaches. Our results demonstrate that learning relative properties rather than absolute values offers a practical solution for modeling noisy experimental data, with direct applications in materials design where thermal stability predictions inform safety protocols.
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All authors Megan C. Davis, R. Seaton Ullberg, Jeremy N. Schroeder, Andrew H. Salij, Marc J. Cawkwell, Christopher J. Snyder, Ivana Matanovic, Wilton J. M. Kort-Kamp

Astrophysics of Galaxies

The Local Origin of a Host Dispersion Measure-Stellar Mass Relation in Fast Radio Bursts

Wasundara Athukoralalage, Liam Connor, Peter K. Blanchard et al. (+1 more)

The origin of fast radio bursts (FRBs) and the relationship to their host galaxy environments remain open questions. Using a sample of 37 FRBs with secure host associations at $z \lesssim 0.25$, and including dwarf, elliptical, and edge-on hosts, we examine the host dispersion measure ($\mathrm{DM_{host}}$) and its dependence on host stellar mass ($M_\star$). We find a statistically significant anti-correlation between the host dispersion measure and host stellar mass (the $\mathrm{DM_{host}}$-$M_\star$ relation; Pearson $r \approx -0.5$, $\log_{10} p \approx -2.8$) that extends across the full range of our sample, $\log_{10}(M_\star/M_\odot) \approx 8$-$11.4$. We find that the rest-frame Faraday rotation measure ($|\mathrm{RM}|_{\mathrm{host}}$) is largest in FRBs that reside in dwarf galaxies, but there is no evidence for a correlation across the full mass range. We show that the $\mathrm{DM_{host}}$-$M_\star$ trend does not arise from the galaxy-averaged interstellar medium (ISM) nor from the circumgalactic medium (CGM). Instead, we argue that the local ($\lesssim 100$ pc) environment is responsible. The spatial statistics of star formation and metallicity-dependent FRB progenitor channels plausibly lead to denser ionized environments in low-mass galaxies and less nearby gas in massive hosts.
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All authors Wasundara Athukoralalage, Liam Connor, Peter K. Blanchard, Edo Berger

Chemical Physics

Wide-Field Opto-Iontronic iSCAT Mapping of Interfacial Charging and Electrical Connectivity

Zhu Zhang and Sanli Faez

Spatial variations in electrical connectivity and interfacial ion accumulation can strongly influence electrochemical performance, yet these properties are difficult to visualize directly with conventional ensemble measurements. Here, we introduce potential-modulated opto-iontronic microscopy, an interferometric scattering microscopy (iSCAT) approach for wide-field imaging of electric-double-layer (EDL) dynamics at nanostructured electrodes. Sinusoidal potentials were applied to focused-ion-beam-fabricated indium tin oxide (ITO) nanoholes, and the optical response was extracted at the modulation frequency by Fourier demodulation. The optical modulation amplitude increased approximately linearly with modulation voltage above a low-voltage roll-off and decreased with increasing frequency, consistent with kinetically limited interfacial charging. We then mapped the potential-synchronized optical amplitude across patterned ITO electrodes. Electrically isolated blocks exhibited strongly suppressed modulation signals, whereas electrically connected and partially milled nanogrid structures showed pronounced responses. These results demonstrate label-free optical mapping of local charging dynamics and electrical connectivity at heterogeneous electrochemical interfaces using a commercially available iSCAT platform.
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General Relativity and Quantum Cosmology

Exploring a phantom Dirac-Born-Infeld regular black hole via particle emission, wave scattering and geodesics

N. Heidari, A. A. Araújo Filho, Iarley P. Lobo et al. (+1 more)

We examine particle creation, evaporation, scalar wave absorption and scattering, and geodesic motion in the asymptotically flat regular black hole supported by a phantom Dirac-Born-Infeld field. For massless bosonic and fermionic fields, the Bogoliubov transformations yield thermal spectra whose Hawking temperature decreases as the regular core becomes more prominent. Energy-conserving tunneling recovers the same temperature in the low-energy limit, whereas recoil and the DBI contribution introduce nonthermal corrections and suppress particle emission. In the high-frequency regime, the enlargement of the cross section does not compensate for the reduction in temperature, resulting in a lower luminosity and a longer evaporation time. A numerical partial wave analysis shows that the total scalar absorption increases with the regular core scale, approaches the horizon area at low frequencies, and oscillates around an enlarged geometric capture limit at high frequencies. The scattering phase shifts modify the multipolar amplitudes nonuniformly and displace the interference fringes toward larger angles. Furthermore, both null and timelike trajectories experience stronger deflection as the regular core contribution increases.
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All authors N. Heidari, A. A. Araújo Filho, Iarley P. Lobo, V. B. Bezerra

Mesoscale and Nanoscale Physics

Quantum encoding of structured light into in-plane topological spin textures

Pavel A. Vorobyev, Daichi Kurebayashi and Oleg A. Tretiakov

Structured light offers a powerful means of controlling light-matter interactions through multiple tunable optical degrees of freedom. Using micromagnetic simulations, we investigate the nucleation of asymmetric bimerons and antibimerons by pulsed Laguerre-Gaussian optical vortices in chiral ferromagnetic thin films with $C_{nv}$ and $D_{2d}$ symmetries, respectively. For optical vortices with orbital angular momentum (OAM) $|m|=1$, circularly polarized beams deterministically nucleate a single bimeron or antibimeron via the interplay of spin angular momentum, OAM, and magnetic chirality, whereas linearly polarized beams produce textures whose topological charge directly follows the OAM ($Q=m$). Optical vortices with OAM $|m|>1$ nucleate clusters and other configurations composed of multiple spin textures, whose morphology and topological charge depend sensitively on the optical quantum numbers and pulse parameters. These findings reveal a route to topology-selective writing through the encoding of optical quantum numbers into distinct in-plane topological magnetic states.
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Astrophysics of Galaxies

The Evolution of Low-Ionization Electron Densities in Galaxies Across Cosmic Epochs

Mabel G. Stephenson, John Chisholm, Alberto Saldana-Lopez et al. (+12 more)

We investigate the low-ionization electron density in the interstellar medium of galaxies across $0$$<$$z$$<$$8$, derived with the [O II]$\lambda\lambda3727,3730$ and [S II]$\lambda\lambda6718,6733$ doublets, using both deep JWST NIRCam/grism and NIRSpec/MSA spectroscopy. Along with ancillary density samples from the literature at $0$$<$$z$$<$$6$, we assemble three samples containing a total of 703 galaxies spanning $3.7$$<$$z$$<$$7.8$ at $\langle z\rangle\sim5.6$; 691 galaxies in the luminosity-complete NIRCam/grism programs CONGRESS and FRESCO at $\langle z\rangle \sim4.3$ and $\langle z\rangle\sim5.3$, respectively, and 12 galaxies with high-resolution NIRSpec/MSA spectra from the GO 1871 and GLASS programs. We find median electron densities of $n_{\rm{e}}$[S II]$=$$463^{+281}_{-203}~{\rm{cm}}^{-3}$ for CONGRESS, $n_{\rm{e}}$[S II]$=$$301^{+388}_{-206}~{\rm{cm}}^{-3}$ for FRESCO, and $n_{\rm{e}}$[O II]$=$$202^{+145}_{-102}~{\rm{cm}}^{-3}$ for the NIRSpec/MSA sample. The median low-ionization $n_{\rm{e}}$ increases from $z= 0$ to $z=4$, in agreement with previous studies and those using JWST observations. However, beyond $z\sim4$ median $n_{\rm{e}}$ begins to deviate from a monotonically increasing evolution with $z$. We find a positive, but shallow, correlation between O$_{32}$ (a proxy for the ionization parameter) and $n_{\rm{e}}$, while also confirming a positive correlation between O$_{32}$ and $z$. We suggest that these trends are possibly due to an evolving ISM gas density and ionization structure, and propose a toy model where the gas clumping evolves with $z$ to explain the observed density and ionization variations.
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All authors Mabel G. Stephenson, John Chisholm, Alberto Saldana-Lopez, Jorryt Matthee, Alaina Henry, Rohan P. Naidu, Sophia R. Flury, Taylor A. Hutchison, Steven L. Finkelstein, Natalia G. Guseva, Yuri I. Izotov, Rui Marques-Chaves, Pascal A. Oesch, Naveen A. Reddy, Daniel Schaerer

Materials Science

Spectrally Programmable Spin-Polarized Photocurrents in WSe$_2$-NiPS$_3$ Magnetic van der Waals Heterostructures

Rajesh Kumar Yadav, Michal Poplinger, Adi Levi et al. (+6 more)

Efficient generation and control of spin-polarized currents in semiconductors remain central challenges for spin-based electronics, particularly due to impedance mismatch and the reliance on magnetic fields or ferromagnetic contacts. Here, we introduce a materials platform for spectrally programmable spin transport based on a van der Waals heterostructure combining the antiferromagnetic semiconductor NiPS$_3$ with WSe$_2$. In a p-n diode architecture, circularly polarized excitation produces pronounced photoconductive resonances with spin polarization reaching 80% near the Neel temperature and persisting at 30% at room temperature. Remarkably, selected spectral bands retain their polarization sign across the magnetic phase transition, evidencing robust, spectrally protected spin-polarized current generation. Polarization-resolved photogalvanic measurements reveal a dominant circular injection-current mechanism, confirming spin-polarized carrier transport. First-principles calculations show that an applied electric field induces interfacial hybridization and spin-layer locking, giving rise to localized symmetry breaking and enhanced optical absorption while preserving global time-reversal symmetry. These results establish spectral tuning of excitation as a new control knob for spin transport, enabling spin-current generation without magnetic fields or polarization switching. Our findings position magnetic van der Waals heterostructures as a versatile platform for opto-spintronic functionality and spectrally programmable spintronic devices.
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All authors Rajesh Kumar Yadav, Michal Poplinger, Adi Levi, Adi Harchol, Nirman Chakraborty, Thomas Brumme, Thomas Heine, Efrat Lifshitz, Doron Naveh

Superconductivity

Intertwined spin-charge stripe order and polar lattice distortion in La$_{3}$Ni$_{2}$O$_{7}$

Xiaoying Li, Wenqian Tu, Run Lv et al. (+4 more)

The low-temperature density-wave state of La$_3$Ni$_2$O$_7$ hosts pronounced spin-density-wave (SDW) order, while recent experiments further reveal charge redistribution and a concomitant lattice-symmetry lowering. However, the microscopic relationship among spin, charge, and lattice remains unclear. Using first-principles calculations, we investigate the pressure evolution of the electronic structure and static spin susceptibility of La$_3$Ni$_2$O$_7$, together with the energetics and lattice response of representative magnetic configurations. We trace the SDW instability to strong Fermi-surface nesting and find that the high-pressure spin response closely tracks $T_{\mathrm C}$, suggesting spin-fluctuation-mediated pairing. Among the candidate magnetic states considered, the spin-charge-stripe states emerge as energetically favored and dynamically stable, developing pronounced disproportionation of both the local Ni moments and the Ni–O bond lengths. Remarkably, the lowest-energy a-stripe state spontaneously relaxes into the experimentally proposed polar Am2m structure through a polar distortion along the b axis. These results establish a unified picture in which spin, charge, and lattice responses are strongly intertwined in the low-pressure density-wave state, while spin fluctuations remain a plausible ingredient of superconductivity under pressure.
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All authors Xiaoying Li, Wenqian Tu, Run Lv, Li'e Liu, Dingfu Shao, Yuping Sun, Wenjian Lu

Quantum Physics

CircLS: Compiling Lattice Surgery to Physical Circuits with Dynamic Allocation

John Yuehan Zhang

In fault-tolerant quantum computing, lattice surgery (LS) is one of the leading ways to realize logical operations, and the Pauli product measurement (PPM) is the basic instruction of LS-based computing. Compilers that work on the PPM sequence, however, stay at the logical level rather than the physical circuit level. This is because lowering PPMs from the logical level to physical circuits is complicated. CircLS is a full-stack lattice surgery compiler: it compiles a quantum program through its PPM sequence to a Stim circuit, lowering every PPM through linear-time stabilizer construction rules. On this basis, we develop a compiler that allocates data patches dynamically: each patch is allocated at its first use and freed at its last use, and the freed tiles can be reused as ancilla paths. Against the two baselines, CircLS reduces the allocated spacetime volume by 34% and 27% and the logical error rate (LER) by 40% and 48%, and it compiles programs that they cannot. CircLS is open source at https://github.com/John-YuehanZhang/CircLS
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Materials Science

Can Strain or Anion Interchange Make an Unstable Structure Stable? Energetics, Lattice Dynamics and Strain-Tunable Band Gaps of Lithium Chalcohalide Antiperovskites (Li$_{3}$$BA$) and their Anion Interchange Variants (Li$_{3}$$AB$)

Ismail A. Buliyaminu, Ehsan Gowdini, Phillip Duxbury et al. (+1 more)

Lithium chalcohalide antiperovskites are a promising, non-toxic alternative to lead halide perovskites, with potential as solid electrolytes for Li-ion batteries. we computationally investigate a relatively unexplored anion-interchange mechanism by which cubic Li$_{3}$$AB$ derivatives are obtained from the parent cubic antiperovskite Li$_{3}$$BA$ ($A$ = O, S, Se, Te, Po; $B$ = F, Cl, Br, I). The calculated relative energy landscape provides a useful guide for anion-site selectivity and its role in structural stability. The energetic stability results reveal that the smaller anion inside the octahedron stabilizes the structures. The lattice-dynamic calculations confirm that Li$_{3}$F$A$ ($A$ = Te, Po) and Li$_{3}$O$B$ ($B$ = Cl, Br, I), which are the most energetically stable compounds, are dynamically stable cubic phases without imaginary phonon modes. However, Li$_{3}$FS and Li$_{3}$FSe, while energetically stable, are dynamically unstable at equilibrium and become dynamically stable under triaxial compressive strain. In addition, we report the electronic structure and density of states (DOS) of all compounds, which show a substantial change in band gap upon anion interchange. The strain engineering of the lithium chalcohalide family illustrates how a few percent of the strain can tune the electronic band gap within the electrochemical stability window for solid battery applications. This study unveils essential characteristics of the anion site-interchange mechanism and provides a foundation for the understanding and design of lithium chalcohalide antiperovskites.
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All authors Ismail A. Buliyaminu, Ehsan Gowdini, Phillip Duxbury, Jose L. Mendoza-Cortes

Cosmology and Nongalactic Astrophysics

A New Probe of Dark Matter Subhalos: Stellar Aberration with TESS

Matthias Daniel, Xiao Xue, Kris Pardo et al. (+1 more)

Small-scale dark matter (DM) structure encodes key information about the particle nature of DM and therefore provides a sensitive test of competing models. Yet, it remains hidden from electromagnetic surveys and is instead inferred through its gravitational effects. Stellar aberration, the apparent shift in a light source's position induced by the observer's motion, offers a largely unexplored channel to access such signatures. DM subhalos can perturb the observer's motion, imprinting characteristic, spatially correlated shifts in stellar positions across the sky. We show that the Transiting Exoplanet Survey Satellite (TESS), with its long temporal baseline, wide sky coverage, and high-cadence observations, is well suited to search for these aberration signals. We derive Fisher-matrix-based sensitivity estimates for constant observer accelerations, forecasting a sensitivity down to $6.3\times 10^{-9}\,\mathrm{m/s^2}$ from the combined sample of TESS stars with magnitude $\mathrm{Tmag}\leq 10$. This sensitivity allows TESS to probe concentrated DM subhalos over a broad parameter space, from $\gtrsim 10^{-6}\,\mathrm{M_{\odot}}$ at AU-scale distances to $\gtrsim 10^{7}\,\mathrm{M_{\odot}}$ at $\mathcal{O}(10\,\mathrm{pc})$. TESS's sector-based observing strategy further provides intrinsic temporal resolution of potential DM-induced aberration signals. Moreover, we briefly discuss challenges for future data analysis, including the modeling of instrumental systematics and stellar astrometric foregrounds, such as parallax and proper motion. Our results establish stellar aberration as a novel probe of DM substructure, paving the way for dedicated searches in TESS and next-generation wide-field surveys.
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All authors Matthias Daniel, Xiao Xue, Kris Pardo, Laura Sagunski

High Energy Physics (Phenomenology)

Topics in the phenomenology of axions: the cases of cosmic strings and superradiance

Antonios Kyriazis

Originally proposed as a solution to the strong CP problem and later understood to be a good dark matter candidates, axions have appeared in a variety of beyond-the-standard-model theories and are imbued with rich phenomelogical consequences. In this dissertation, we will examine two of these consequences: the emission of axions from cosmic strings and the superradiant mechanism in black hole physics. The spontaneous symmetry breaking of a global symmetry in the early universe can give rise to a network of cosmic strings, which emit ultra light, axion-like particles that can contribute to the dark matter density. We will discuss how the associated density fluctuations of these particles can be computed from first principles by treating them as a collection of plane waves. We will then calculate the density power spectrum and compare it to well-established cosmological observables, as well as to observables from future surveys, to derive constraints on the mass of the particles and the symmetry breaking scale. These light axion-like particles can also form a gravitational atom around a spinning black hole through the superradiance process. Considering the black hole to be part of a binary system, the tidal potential of the companion periodically perturbs the gravitational atom such that an atomic transition occurs between two of its energy states. Gravitational waves are emitted by the cloud during this transition. We will derive the analytical formulae of both the strain waveform and frequency spectrum of the signal and identify the systems that would be the most promising for detecting it in future, space-based gravitational wave observatories.
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High Energy Physics (Phenomenology)

Photon and gluon gravitational form factors of proton in QCD

Z. Asmaee and K. Azizi

The energy momentum tensor allows us to probe the internal gravitational structure of the proton. The corresponding gravitational form factors contain information about its different contributions. In this work, we investigate the photon and gluon gravitational form factors of the proton within the QCD sum rule approach. Four independent gravitational form factors are computed in the range $0<Q^2<2\ \mathrm{GeV}^2$. The mass and scalar radii of the photon and gluon sectors are obtained in the forward limit. We find that the gluon mass radius is smaller than the photon mass radius. These results may be useful for future lattice QCD calculations and phenomenological studies.
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Mathematical Physics · Cross-listed from math.NA

Computing statistical Euler limits of the Navier–Stokes equations in three dimensions

Johannes L. Grafen, Tobias Rohner and Stephan Simonis

We develop a Monte Carlo lattice Boltzmann method to compute statistical solutions to the three-dimensional incompressible Navier–Stokes and Euler equations. Entropic space-time adaptive relaxation of the higher order kinetic moments yields stable numerical solutions with decreasing viscosity. We provide a convergence analysis that is conditional on four explicitly stated assumptions regarding the discrete dynamics. Under diffusive scaling, the laws of the discrete ensemble converge along a subsequence to a limit satisfying the Foias–Temam Liouville formulation of the Navier–Stokes equations. Consequently, provided the structure function scaling holds uniformly, the vanishing viscosity limit of these measures satisfies the multi-point statistical Euler hierarchy of Fjordholm, Mishra, and Weber. The limit measures inherit the known weak-strong uniqueness principle on the interval of existence of a strong Euler solution. Under explicit scaling assumptions, a Kuznetsov-type argument yields a fractional 1-Wasserstein convergence rate. We present three-dimensional computations of time-dependent statistical solutions along the inviscid limit of the incompressible Navier–Stokes equations together with convergence measurements in the Wasserstein metric. Numerical experiments on a randomized Taylor–Green vortex with 24-dimensional initial uncertainty recover Kolmogorov's K41 scaling for energy spectra and structure functions, exhibit the failure of pathwise strong convergence, and yield Wasserstein convergence rates of about $0.5$ at the onset of turbulence. Finally, error measurements with respect to spectral hyperviscosity computations indicate that the computed limit measure is independent of the numerical regularization.
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High Energy Physics (Theory)

A simple construction of Heat Kernels and conformal anomalies via Fedosov deformation quantization

Thomas Basile and Evgeny Skvortsov

We propose a new approach to the systematic computation of the heat-kernel expansion and, in particular, of conformal anomalies, based on Fedosov deformation quantization. The approach is fully covariant, applies to differential operators of arbitrary order, is amenable to efficient implementation, and yields closed-form expressions. As applications, we compute conformal anomalies in four, six, and eight dimensions, the last being a new result.
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High Energy Physics (Experiment)

Exploring ESS$\nu$SB Near Water Cherenkov Detector Designs Through Graph Neural Network Flavour Identification

J. Aguilar, M. Anastasopoulos, D. Barčot et al. (+100 more)

The ESS$\nu$SB experiment aims to measure CP violation in the leptonic sector with high precision, necessitating robust reconstruction of neutrino events in the water Cherenkov (WC) detectors. In this work, we investigate the flavour identification potential of the proposed near WC detector using graph neural network (GNN)-based classification, with a focus on variations of key detector design parameters. In particular, we study whether a smaller and/or less instrumented detector can achieve the required classification performance. Using detailed Monte Carlo simulations of charged-current (CC) neutrino interactions, we train GNN classifiers to distinguish electron and muon neutrino CC events. We find that GNN-based classification remains accurate even for detector configurations with volumes up to a factor of eight smaller than the nominal design, with only moderate degradation in classification efficiency at fixed background rejection. The resulting loss in efficiency can largely be compensated by increased exposure time. Furthermore, we demonstrate that reduced photomultiplier tube (PMT) coverage in the nominal detector has a limited impact on classification performance, provided that coverage is maintained in regions of highest signal yield, in particular near the forward end-cap.
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All authors J. Aguilar, M. Anastasopoulos, D. Barčot, E. Baussan, A.K. Bhattacharyya, A. Bignami, M. Blennow, M. Bogomilov, B. Bolling, E. Bouquerel, F. Bramati, A. Branca, G. Brunetti, A. Burgman, I. Bustinduy, C.J. Carlile, J. Cederkall, T. W. Choi, S. Choubey, P. Christiansen, I. Christodoulou, E. Cristaldo Morales, P. Cupiał, D. D'Ago, H. Danared, J. P. A. M. de André, M. Dracos, I. Efthymiopoulos, T. Ekelöf, M. Eshraqi, G. Fanourakis, A. Farricker, E. Fasoula, T. Fukuda, S. Gago, N. Gazis, Th. Geralis, M. Ghosh, A. Giarnetti, G. Gokbulut, C. Hagner, L. Halić, S. G. Hernández, J. Hiegel, M. Hooft, K. E. Iversen, N. Jachowicz, M. Jakkapu, M. Jensen, I. Karakoulias, E. Kasimi, A. Kayis Topaksu, B. Kliček, K. Kordas, B. Kovač, A. Leisos, A. Longhin, M. López, C. Maiano, S. Marangoni, J. García-Marcos, C. Marrelli, D. Meloni, M. Mezzetto, N. Milas, J.L. Muñoz, K. Niewczas, M. Oglakci, T. Ohlsson, M. Olvegård, A. Opanasenko, M. Pari, J. Park, D. Patrzalek, G. Petkov, Ch. Petridou, P. Poussot, A Psallidas, F. Pupilli, M. L. Reguera, D. Saiang, E. Salehi, D. Sampsonidis, A. Scanu, C. Schwab, F. Sordo, G. Stavropoulos, M. Stipčević, R. Tarkeshian, F. Terranova, T. Tolba, M. Topp-Mugglestone, E. Trachanas, R. Tsenov, A. Tsirigotis, S. E. Tzamarias, M. Vanderpoorten, G. Vankova-Kirilova, N. Vassilopoulos, S. Vihonen, J. Wurtz, V. Zeter, O. Zormpa

High Energy Physics (Theory)

General Construction of Time-Dependent Integrable Chiral Field Theories

Pradip Kattel

We develop a general procedure for constructing time-dependent integrable chiral field theories from autonomous unitary difference-form $S$-matrices satisfying the Yang-Baxter equation. Spectral parameters are transported along the free right- and left-moving characteristics, defining a map from physical spacetime to spectral space on which the two-body scattering data are evaluated. Requiring spatially homogeneous right-left scattering forces the characteristic map to be affine. The inverse Cayley transform then determines the local contact interaction, while evaluation along the affine spectral trajectory fixes its time dependence. Thus, the nonautonomous interaction is determined by the autonomous scattering data together with chiral kinematics and spatial homogeneity, rather than being introduced independently. The Yang–Baxter equation supplies the factorized many-body transport, and on a spatial circle periodicity leads to quantum Knizhnik–Zamolodchikov (qKZ) equations whose compatibility defines a flat discrete transport in spectral space. Pulling the corresponding spectral-space amplitudes back to physical coordinates gives the time-dependent many-body wavefunctions. Rational $SU(N)$, trigonometric $U_q(\widehat{\mathfrak{sl}}_2)$, and rational $O(N)$ scattering illustrate how the same mechanism generates distinct nonautonomous interactions. The resulting framework gives a geometric route from autonomous factorized scattering data to time-dependent integrable field theories.
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Optics

Classification of Non-Hermitian Flat Bands

Chang-geun Oh and Jun-Won Rhim

Exact flat bands provide a versatile setting for correlated and topological phenomena, yet their properties are controlled not only by their dispersion but also by the structure of their Bloch projectors. Here, we establish a projector-based classification of non-Hermitian flat bands. In contrast to Hermitian flat bands, non-Hermiticity introduces a biorthogonal projector whose left-right pairing permits a distinct norm-pole singularity. We identify four classes: analytic NH-A, continuous but nonanalytic NH-C, bounded but discontinuous NH-D, and pole-singular NH-E. We show that continuity of the biorthogonal projector preserves the locking of the right, left, and biorthogonal Chern numbers, $C_R=C_L=C_{\rm bi}$, thereby realizing non-Hermitian critical topological flat bands. Once continuity is lost, this locking can break down; in particular, a mismatch $C_R\neq C_L$ can occur in the NH-E class. Finally, we show that this Chern number mismatch ensures to produce an anomalous enhancement of resonant cross-orbital transfer. Our results establish biorthogonal projector regularity as the organizing principle linking compact localized states, topology, and driven response in non-Hermitian flat bands.
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Atomic Physics

Multi-hour stable trapping and threshold steady state of non-laser-coolable ions with ultracold atoms in a hybrid trap

Satyabrata Baidya and Sourav Dutta

We report multi-hour stable trapping and steady state of non-laser-coolable Cs$^{+}$ ions in a linear Paul trap, achieved via resonant charge-exchange (RCE) cooling with a precisely centered ultracold Cs cloud. Without cold atoms, all ions are lost within 3 minutes. With centered cold atoms, RCE cooling establishes a stable population of ions for 6 hours with no measurable decay – more than two orders of magnitude longer hold times compared to prior hybrid atom-ion systems. We observe a threshold behavior in the steady-state number of ions ($N_{s}$): initial ion loadings above $N_{s}$ ions converge downward to $N_{s}$ ions and remain constant thereafter; initial loadings below $N_{s}$ ions show no measurable decay. The dynamics is governed by a competition between ion-ion rf heating and ion-atom collisional cooling. The prolonged, simultaneous ion-atom trapping suggests an upper bound on the three-body recombination-induced Cs$_{2}^{+}$ formation rate constant: $k_{3} << 1.4 \times 10^{-25} cm^{6} s^{-1}$. This remarkable realization of long-lived steady state overcomes a critical limitation of prior hybrid atom-ion systems and enables extended studies of ultracold ion-neutral chemistry, rare inelastic collisions, and sympathetic cooling routes for complex molecular ions.
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Statistical Mechanics

Entropy Production Bounds the Accuracy of Computation in Markov Networks

Songela W. Chen and David T. Limmer

Biological and artificial networks compute by transforming time-dependent inputs into functional outputs. Because the internal state of a stochastic network relaxes on finite timescales, its output generally lags behind a changing environment, producing computational errors. We show that for reversible continuous-time Markov networks the error admits a universal thermodynamic bound. Decomposing the total error into representation and lag contributions, we derive an inequality relating the lag error to the entropy production rate and a memory time equal to the integrated equilibrium autocorrelation of the output observable. The bound implies that accurate dynamical computation requires either substantial dissipation or long-lived memory encoded in slowly relaxing modes. We demonstrate these principles in artificial Markov networks and in models of biochemical information processing. Our results establish a thermodynamic limit on information processing in stochastic networks and provide a quantitative framework for understanding the energetic costs of biological computation.
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Statistical Mechanics

Weak irreducibility as a spectral criterion for phase coexistence

Onofre Rojas

Conventional finite-size theories describe first-order coexistence through free-energy competition and interfacial tunneling, but the distinct spectral roles of sector balance and inter-sector connectivity are not usually explicit. We show that pseudo-transitions and thermodynamic phase coexistence are governed by two spectral coordinates: sector imbalance locates balance, while connectivity determines whether that balance remains avoided. At balance, finite connectivity produces a unique dominant state with equal spectral weights in the symmetrized two-sector representation. For short-range systems with positive interface tension, interfacial costs suppress the connectivity exponentially, close the coexistence splitting, and asymptotically restore reducibility. Thus, genuine phase coexistence emerges as the singular limit of finite-size avoided coexistence, whereas one-dimensional pseudo-transitions retain finite connectivity. In a decorated bilayer Ising model, the coexistence gap at independently est
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High Energy Physics (Theory)

Bell-CHSH Violation for a Massless Majorana Field in a Double Cone from Modular Localization

S.P. Sorella

We investigate Bell-CHSH correlations for a chiral massless Majorana field localized in a double cone. The conformal modular flow of the associated light-ray interval is converted into translations by a rapidity-like coordinate, and the one-particle scalar product is derived in modular momentum space. Particular attention is paid to the fact that this scalar product carries a Fermi-Dirac weight. Requiring the modular conjugation to be antiunitary with respect to that weighted scalar product fixes the Fourier-space realization of the modular objects. The resulting Tomita-Takesaki operator and its adjoint generate Alice and twisted-dual Bob directions for which all four crossed CAR orthogonality relations follow automatically from modular localization. The Bell problem then reduces to a simple one-function functional. For a Gaussian modular-momentum profile $h_\sigma(k)=\exp[-k^2/(2\sigma^2)]$ the Bell parameter is larger than the classical bound for a broad range of widths and approaches the Tsirelson value analytically, \[ \lim_{\sigma\to 0^+}{\it B}(\sigma)=2\sqrt2 \] Thus near-maximal Bell violation is obtained from an explicit sequence of smooth rapidly decreasing profiles concentrated around zero modular momentum, corresponding to the modular spectral value $\lambda=1$.
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High Energy Physics (Phenomenology)

S-matrix informed neural networks for amplitude analysis

Wyatt A. Smith, Arkaitz Rodas, Marius D. Thomas et al. (+5 more)

Reconstructing scattering amplitudes from finite, noisy, and mutually inconsistent measurements is an ill-posed inverse problem common to many reactions relevant to particle physics. We introduce S-matrix informed neural networks (SINNs), and demonstrate their ability to learn scattering amplitudes directly from data while respecting first principles. We further develop a novel data selection procedure, which uses the response of constrained neural network ensembles to identify a set of experiments compatible with first principles, and with each other. We apply this framework to $\pi\pi$ scattering, producing reusable amplitudes and correlated uncertainties without relying on a fixed functional form. We validate our results against residual model dependencies and training biases through closure tests and ablations. We find negligible impact of model architecture on our results. Our workflow unifies physics-constrained representation learning, data selection, and uncertainty quantification. Our strategy is transferable to other scattering processes, and other constrained physics problems limited by inconsistent data.
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All authors Wyatt A. Smith, Arkaitz Rodas, Marius D. Thomas, César Fernández-Ramírez, Giorgio Foti, Lin Qiu, Adam P. Szczepaniak, Alessandro Pilloni