High Energy Physics (Phenomenology)
The production of bottom-flavoured jets at the LHC through bottom-quark pair production at NNLO+PS
Rhorry Gauld, Alessandro Ratti, Marius Wiesemann et al. (+1 more)
We consider the dominant production mechanism of bottom-flavoured jets at the LHC, which proceeds through bottom-
quark pair production. We compute next-to-next-to- leading-order (NNLO) QCD corrections retaining full bottom-
quark mass effects and match them with a parton shower (NNLO+PS). Our predictions provide a realistic description of events with one and two bottom-flavoured jets at both the partonic and hadronic level. We compare different jet-flavour definitions and confirm that the dominant numerical differences between the jet
algorithms result from the treatment of jets that contain two bottom
quarks originating from $g\to b\bar b$ splittings. We compare our predictions, using the experimental bottom-flavour tagging prescription, with measurements by ATLAS, CMS, and LHCb at 7 and 13 TeV, finding good agreement for the distributions presented by ATLAS and CMS and a good description of the shapes of the LHCb data. We also discuss the impact of various physics effects on the considered distributions: power corrections in the bottom-
quark mass, the implications of symmetric/asymmetric jet-selection cuts, as well as contributions from multi-parton interactions.
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All authors Rhorry Gauld, Alessandro Ratti, Marius Wiesemann, Giulia Zanderighi
Computational Physics · Cross-listed from math.AP
A domain decomposition method for the directional contact angle hysteresis interval on doubly periodic rough surfaces
Zijie Lin, William M Feldman and Braxton Osting
We study wetting on a doubly periodic rough surface in three dimensions. Although the
liquid-vapor interface meets the solid at the local Young's angle, microscale roughness can cause the macroscopic apparent angle to differ substantially from this value. We formulate the directional contact angle hysteresis (CAH) interval in terms of apparent angles associated with pinned microscopic configurations. To approximate its receding and advancing endpoints, we evolve capillary mean
curvature flow (CMCF) toward extremal stationary states. Computing these states is difficult because the pinning that produces hysteresis is generated at the scale of the roughness, whereas the apparent angle is only meaningful at the macroscopic scale, so a single uniform grid must resolve both. We therefore introduce a two-scale alternating (TSA) method based on a Schwarz decomposition: a Merriman-Bence-Osher (MBO)
diffusion-generated scheme resolves the contact-line near region, while a linearized minimal-surface problem updates the far region. For an idealized reference iteration, we prove decay of an approximate interfacial energy. Numerical experiments on a representative doubly periodic surface show a strongly anisotropic CAH interval whose width varies by more than a factor of three with contact-line orientation and changes sharply near the diagonal directions. Because a stationary droplet must meet the solid at an apparent angle inside this interval, the computed anisotropy constrains which macroscopic wetted regions the surface can support; it is consistent with a square-like stationary droplet whose sides align with the diagonal directions.
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Cosmology and Nongalactic Astrophysics
On the cosmic previrialization
Shubhadip Bera and Michał J. Chodorowski
Non-linear gravitational
evolution affects the growth of density and velocity fluctuations, and leads to previrialization effects before virialized structures are formed. Therefore, understanding and quantifying the leading nonlinear corrections to the corresponding variances is crucial for describing the departure from linear structure formation. We calculate the first nonlinear correction to the variance of the
cosmic density and velocity fields. We analyze the 1-loop contributions associated with the second and third order perturbative kernels of both the density and velocity-divergence fields. The relevant forms of the third-order kernels $F_3(\vec{k},\vec{q},-\vec{q})$ for density, and $G_3(\vec{k},\vec{q},-\vec{q})$ for velocity divergence, are clearly non-symmetric under exchange of $\vec{k}$ with $\vec{q}$. However, the calculation of the variance involves a symmetric double integral of these variables, so in this particular case the kernels can be additionally symmetrized. We therefore explicitly symmetrize these kernels $F_3$ and $G_3$, and express them as functions of the two scalar variables: the cosine of the angle between the two wavevectors and a symmetric function of their magnitudes. This representation enables us to identify and isolate the terms which are divergent before performing the angular integration, and to show their cancellation between the second- and third-order terms. The divergent contribution from $P_{\delta 22}\,$ to the one-loop power spectrum cancels exactly that arising from $P_{\delta 13}$ . Angularly averaged divergence-free part of $F_3$ turns out to be remarkably close to a constant. We found that the corresponding coefficient of the leading-order correction is confined to a remarkably narrow interval of 4007/2205 to 4063/2205 $(\simeq 1.817 \leq C \leq 1.843)$, for any form of the linear power spectrum.
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Mathematical Physics
An additional possibilities of the standard method of inverting the Radon transform
D.S. Anikonov, S.G. Kazantsev and D.S. Konovalova
The problem of inverting the Radon integral transform in finite-dimensional Euclidean space is considered. The relevance of this topic for probing issues is indicated. It is noted that for the latter direction, it is natural to consider the integrand as discontinuous function. However, the available inversion formulas are only proven for differentiable functions. Therefore, the question of obtaining formulas for discontinuous functions arises. It is set that the required results can be obtained by some modification of available proofs for smooth functions.
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Strongly Correlated Electrons
What does "instant thermalization" in large-$q$ SYK models mean?
Alexander Osterkorn and Jan C. Louw
Motivated by the Planckian thermalization rate $\Gamma \sim T$ observed in the two-body interacting SYK model, we study thermalization in the $q/2$-body case. Previous studies of such systems have established the notion of instantaneous thermalization to leading order in $1/q$. It was conjectured that the thermalization may still be Planckian but with a divergent rate $\Gamma \sim T q$, explaining the “instantaneous” part. For an analytically and numerically tractable system, we calculate the effective temperatures after a quench at time $t = 0$ and indeed find a Planckian rate, albeit with the unexpected decaying behavior $\Gamma \sim T q^{-1} $. This is contrasted with the behavior of the causal Green's function $\mathcal{G}(t_1, t_2)$, which instantly acquires a thermal form in the two-time plane block $t_1, t_2 > 0$. The resulting picture is that instant thermalization is a meaningful concept only for this block, while the off-diagonal blocks $t_1 \cdot t_2 < 0$ are inherently non-thermal at any $q$. Since the effective temperature is obtained from correlations spanning all blocks, it inherits a finite rate set by the off-diagonal. We illustrate this directly by studying the non-thermal correlations' time dependence.
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Medical Physics
The Magnetic-Resonance-Based, Omni-Directional Hydrophone
Nathan Thyberg, Davi Cavinatto, Katia Oler et al. (+3 more)
This study aims to improve the directional sensitivity of
magnetic resonance hydrophone (MRH) methods and allow for detection and quantification of waves traveling at any angle relative to the MRI bore-axis. Doing so may better integrate MRH technology into transcranial focused ultrasound neuromodulation therapies. Existing MRH implementations only encode acoustic waves propagating along the MRI bore-axis, precluding use with wide aperture transducers or temporal skull windows. This study expands the MRH technique into a MR-based Omni-directional Hydrophone (MRbOH) that can quantify the magnitude pressure and phase of waves propagating at any angle. The MRbOH method formulates a system of equations around uniquely sensitized images that, when solved, introduce sensitivity to oblique acoustic waves. The method was tested experimentally in a gel phantom that was insonated at $0^o$, $45^o$, and $90^o$ relative to the MRI bore-axis. The method reconstructed pressure maps at all three angles of propagation, including features such as peak pressure, partial reflections, and beamwidth. The MRbOH method measured an average beamwidth of 16.2 mm while the hydrophone measured a beamwidth of 14.5 mm. Average hydrophone-measured pressure within a region of interest was 416.19 $\boldsymbol{\pm}$ 78.07 kPa. Average MRbOH measured pressure in the same region at $0^o$, $45^o$, and $90^o$, respectively, were: 285.5 $\boldsymbol{\pm}$ 49.5 kPa, 193.13 $\boldsymbol{\pm}$ 43.55 kPa, 194.7 $\boldsymbol{\pm}$ 47.38 kPa. In addition, the study presents and experimentally verifies a statistical noise model that predicted the mean with $R^2 = 0.85$, and standard deviation with $R^2 = 0.83$.
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All authors Nathan Thyberg, Davi Cavinatto, Katia Oler, Elijah Oxborrow, Hyrum Mangum, Steven P. Allen
Earth and Planetary Astrophysics
Uncovering temperate worlds: an updated look at the K2-3 system with ESPRESSO
Avidaan Srivastava, Emma Pimentel, Amélie Gressier et al. (+24 more)
The K2-3 system is one of the most unique planetary systems as it features three transiting sub-Neptunes in decreasing order of radii, spanning the radius valley. In addition to that, the two outer
planets are temperate in nature making this system a perfect laboratory for investigating the nature and formation of small potentially habitable worlds. We present new radial velocity data obtained during the ESPRESSO-GTO programme to add to the archival HARPS, HARPS-N and HIRES data for a total time span of 8 years. This combined
dataset significantly improves the masses of the K2-3
planets. We analyse the spectroscopic data with the line-by-line
algorithm. We coupled this timeseries with a multi-dimensional Gaussian process framework to disentangle the 40.5-days
stellar rotation from the Keplerian signals. We tested models using two activity indicators to ensure the retrieved semi-amplitudes of the
planets are not biased by the choice of activity indicator. The multi-dimensional Gaussian process framework, with either activity indicator, yields the following masses: Mb=6.61+/-0.47Me; Mc=2.23+/-0.68Me; Md=2.12+/-1.27Me. Compared to previous works, our detection significance of K2-3b has increased by a factor of two, the mass of K2-3c has slightly decreased and we now have a marginal detection for K2-3d. The positions of the
planets in the mass-radius diagram suggest either a H/He-rich or volatile-rich composition for both K2-3b and c, while the nature of K2-3d is ambiguous. A forward atmospheric model suggests that a single visit with JWST can distinguish between a H/He-rich atmosphere from a water-world scenario. This
dataset exemplifies the capability of ESPRESSO to detect sub-metre-per-second radial velocity signals for the detection of temperate
exoplanets.
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All authors Avidaan Srivastava, Emma Pimentel, Amélie Gressier, René Doyon, Melissa J. Hobson, Alessandro Sozzetti, Mario Damasso, Yann Alibert, Susana C. C. Barros, François Bouchy, Amadeo Castro-González, Olivier D. S. Demangeon, Xavier Dumusque, Jonay I. González Hernández, Baptiste Lavie, Jorge Lillo-Box, Christophe Lovis, Giuseppina Micela, Enric Palle, Francesco Pepe, Rafael Rebolo, José Rodrigues, Nuno C. Santos, Sérgio G. Sousa, Alejandro Suárez Mascareño, Stéphane Udry, María R. Zapatero-Osorio
Soft Condensed Matter
Electric field effects on electrolytes near rough dielectric surfaces by GPU-accelerated code
Isaac Smith, Nicholas Pogharian, Francisco J. Solis et al. (+2 more)
Dielectric interfaces are ubiquitous in manufactured and natural systems, such as iontronic devices, supercapacitors, and living
cells. These, often rough, dielectric surfaces host ionic charge distributions that depend on the surface geometry and the electric fields present. In this work, we study the effect of electric fields on such ionic charge distributions. We demonstrate, by molecular dynamics (MD) and perturbative analytic calculations, that the pattern of alternating regions of ionic charge density created by a sinusoidal interface can be modified and reversed by applying an electric field. We determine the strength of the critical electric field required to cancel the effect of dielectric interface-driven modulation in ion density and develop an analytic expression for that field for small amplitude sinusoidal variations in surface height. We show that ion concentrations near a surface with height given by a sum of
Fourier modes can be found by adding the contributions from the concentration modulation due to each mode, allowing the possibility to predict ion distributions near rough surfaces. We updated and validated a LAMMPS package for MD simulation of polarizable surfaces, the DIELECTRIC package, by implementing a new version that achieves a 2.4-24 times speed increase by GPU parallelization on our test system and adds the capability to simulate an applied electric field on simple and complex electrolytes near dielectric interfaces with arbitrary roughness.
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All authors Isaac Smith, Nicholas Pogharian, Francisco J. Solis, Trung Dac Nguyen, Monica Olvera de la Cruz
Quantum Physics
QiT: Quantum-Inspired Transformer for Visual Recognition Task
Badri N. Patro and Vijay Agneeswaran
Quantum machine learning offers a compelling representational perspective: angle-encoded states inhabit
Hilbert spaces in which periodic similarities and interactions can be expressed naturally. Realizing this perspective for visual recognition remains difficult, however, because present
quantum neural networks are constrained by limited
qubit counts, costly
circuit simulation and measurement, noise, and unstable optimization on noisy intermediate-scale
quantum devices. We investigate whether useful structural ideas from
quantum models can instead be realized as scalable classical
Transformer operations. We introduce QiT, a
Quantum-inspired
Transformer for
vision tasks with three components: (i) angle-inspired encoding that maps image
tokens to learned trigonometric
Hilbert-space features analogous to
quantum rotation-based state encoding; (ii) self-
attention over these periodic features, inducing a classical cosine kernel approximated to
quantum fidelity kernels; and (iii) gated multiplicative emulation, a trainable classical surrogate for interaction terms found in variational
circuits. All components are differentiable tensor operations, so QiT claims neither
quantum computation nor
quantum speedup and retains the $\mathcal{O}(N^2D)$
attention complexity of a standard
Vision Transformer. Across image-classification
benchmarks, QiT is competitive with a matched classical
Transformer while avoiding the severe runtime cost observed for a small simulated
quantum Transformer. QiT-B reaches 78.3% ImageNet-1K top-1 accuracy with 45.7M parameters and 11.5 GFLOPs. These results position QiT as a scalable baseline for isolating and evaluating
quantum-motivated inductive biases in visual recognition.
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Quantum Physics
Superconducting levitation and control of a high-reflectivity micromirror
Philipp Koller, Jannek J. Hansen, David Walcher et al. (+9 more)
We introduce a method to suspend an optical micromirror, with a total mass of \SI{30}{\micro\gram}, using superconducting
magnetic levitation. The micromirror is formed on a silicon membrane, coated with a high-reflectivity dielectric stack and attached to superconducting microspheres. The object is stably levitated inside a
magnetic quadrupole field at cryogenic temperatures.
Magnetic feedback on the transverse motion is used to stabilize the position of the levitator within the trapping field, allowing to measure the axial displacement of the levitator using optical interferometry. The system reaches a sensitivity of order \SI{100}{\pico\metre/\sqrt{\hertz}} near the axial trap frequency of \SI{167}{Hz}. This approach enables free-standing mirrors with minimal dissipation and tunable oscillation frequencies, offering a platform for precision sensing and
quantum cavity optomechanics in the microgram regime.
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All authors Philipp Koller, Jannek J. Hansen, David Walcher, Tomáš Plichta, Rémi Claessen, Martin Žemlička, Philip Schmidt, Rhys G. Povey, Stefan Minniberger, Stefan Putz, Markus Aspelmeyer, Michael Trupke
Quantum Physics
Exact damping-basis continued fractions for few-atom lasers: collective correlations beyond second-order cumulant closure
Stephan Hartmann
We combine the Briegel–Englert damping basis of a lossy cavity mode with the permutation-invariant Liouville basis of \(N\) identical, incoherently pumped two-level emitters. The resulting Liouvillian is exactly block tridiagonal in a single radial field index, with atomic blocks of dimension \(\binom{N+3}{3}\). The stationary state follows from a
matrix continued fraction whose asymptotic closure is a linear
matrix equation that we prove to be uniquely solvable throughout the dissipative regime \(A>0\), and the same construction in the coherence-one sector yields the emission spectrum. The method is validated against direct diagonalization, weak-pump perturbation theory, and closed-system spectra, reaches \(N=16\) in tens of seconds in the few-quanta regime, and has a quantified precision limit at large
photon number. We use it to derive an exact two-atom
photon-balance identity that isolates the cavity-induced pair coherence and relates it to a singlet–triplet population difference; to establish an exact pump-order hierarchy of connected correlations for a zero-temperature cavity and a parity property of the minimal collective-
spin sector; and to
benchmark the second-order cumulant closure used in few-emitter
laser theory, which we find to be semi-quantitative for the
photon number but to predict the wrong sign of the inter-emitter coherence above inversion. In a good-cavity regime the exact solution shows near-Poissonian statistics and strong line narrowing for two and three emitters.
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High Energy Astrophysical Phenomena
The Hidden Evolution of Gamma-Ray Burst Jets Revealed by Gravitational Waves
Gerardo Urrutia, Fabio De Colle, Agnieszka Janiuk et al. (+2 more)
Gamma-ray burst (GRB) jets can propagate through massive
stars, where the high opacity of the
stellar envelope traps electromagnetic radiation and limits observations of the jet at early times. Gravitational waves (GWs), in contrast, can escape these dense environments and provide direct information of the jet dynamics. Previous studies have shown that GRB jets can emit GWs at low frequencies, while high-frequency emission may arise from jet-driven cocoons. However, the cocoon contribution typically requires energies much larger than those inferred from observations and produces
stochastic fluctuations that can resemble noise. In this work, we show that high-frequency GW signals, can instead be generated by variability in the central engine. We consider jet models with different luminosity histories. We find that the GW emission depends on both the central engine history and the interaction of the jet with the
stellar envelope. Rapid luminosity fluctuations are progressively suppressed as the jet propagates through the
star, while the GW signal preserves information about the early jet
evolution. Jets powered by strongly variable engines produce a GW signal peaking at tens of Hz, whereas smoothly varying engines are dominated by low-frequency emission. For a source at 36 Mpc, comparable to the distance of the closest GRB observed to date, the high-frequency signal from our most energetic variable models can reach amplitudes detectable by current ground-based interferometers. Our results suggest that the detection or non-detection of GWs from nearby GRBs and Type Ic broad-lined SNe could help constrain the mechanisms operating in the central engine.
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All authors Gerardo Urrutia, Fabio De Colle, Agnieszka Janiuk, Claudia Moreno, Enrico Ramirez-Ruiz
General Relativity and Quantum Cosmology
Extremal curves of Perlick's proper time in Weyl geometry
E. Rodrigues, F. Dahia, I. P. Lobo et al. (+1 more)
We investigate the extremization of Perlick's proper time in non-integrable Weyl geometry. We derive the corresponding generalized Euler–Lagrange equations and show that the resulting extremals do not, in general, coincide with the autoparallels of the Weyl connection, their difference being governed by the Weyl length
curvature and vanishing in the integrable case. A distinctive feature of the extremal equation is its nonlocal character: in the Weyl proper-time parametrization, the acceleration depends explicitly on the remaining proper time to the endpoint of the variational interval. We illustrate this behavior for a weak constant Weyl field and show that a local Lorentz-force dynamics emerges in a double-scaling limit in which the Weyl field vanishes and the terminal proper time diverges while their product remains finite. These results uncover a nontrivial relation between proper-time extremization, Weyl non-integrability, and local force dynamics.
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All authors E. Rodrigues, F. Dahia, I. P. Lobo, C. Romero
Nuclear Experiment
Constraining the $f_0(980)$ Structure and Formation Dynamics via Anisotropy-Response Scaling
Roy A. Lacey
A species-resolved anisotropy-response scaling framework is used to investigate the structure and formation dynamics of the $f_0(980)$ in relativistic
nuclear collisions. Published measurements in high-multiplicity p+Pb collisions at $\sqrt{s_{NN}}=8.16$~TeV exhibit broad scaling closure under a single-
meson response construction, with a small effective final-state response, $\zeta_{f_0}\simeq0.04$, whereas a symmetric ${\rm K\bar K}$ constituent-response construction gives substantially poorer closure. An explicitly molecular ${\rm K\bar K}$ calculation also exhibits single-
meson-like scaling but gives a substantially larger effective final-state response, $\zeta_{f_0}\simeq0.16$. Thus, single-
meson scaling alone is not a unique structural discriminator. The combined response construction and $\zeta_{f_0}$ constraints characterize the measured $f_0(980)$ by a single-
meson-like anisotropy response with weak final-state sensitivity, distinctly different from the molecular
benchmark. These results establish anisotropy-response scaling as a new experimental probe of $f_0(980)$ formation dynamics and motivate systematic tests across collision systems and beam energies.
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Physics and Society
Why Some Strikes Last Longer: The Resilience Paradox of Partially Functional Institutions
Nuno Crokidakis
Labor strikes do not necessarily lead to complete institutional disruption, particularly when non-striking sectors maintain part of normal activities. We propose a minimal dynamical model to investigate how such residual activity affects the persistence of labor conflicts. The model couples strike participation, institutional response, and overall functionality through two competing mechanisms: a direct suppressive effect of residual activity on strike participation and an indirect effect arising from the reduced institutional pressure to resolve the conflict. Analytical calculations reveal a counterintuitive regime in which increasing residual activity increases, rather than decreases, stationary strike participation. We characterize this behavior through a strike-response susceptibility and derive an exact compensation threshold separating the conventional regime from a resilience-paradox regime. At the threshold, the two mechanisms exactly balance, making stationary strike participation independent of residual activity. Numerical results confirm the analytical predictions and illustrate the underlying mechanism. Our results show that institutional resilience can have an unintended dynamical consequence: by absorbing part of the disruption generated by a strike, continued operation may reduce the urgency of institutional response and thereby favor conflict persistence. This provides a simple example of how individually stabilizing processes can collectively generate counterintuitive outcomes in complex social systems.
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Astrophysics of Galaxies
JADES: Dynamical Measurements of Dark Matter Halo Masses at $z \approx 7$ Using Galaxy Pairs
Zihao Wu, Daniel J. Eisenstein, Benjamin D. Johnson et al. (+13 more)
We present dynamical measurements of dark matter
halo masses at $z\approx7$ using
galaxy pairs.
Galaxy pairs in the early Universe are usually in their first infall, before substantial orbital
evolution or phase mixing. Their relative velocities closely trace the
halo mass, especially when the pair separation is near the
halo virial radius. In the TNG100 simulation, we find that dynamical mass
estimators can recover
halo masses with an intrinsic scatter of $\sim$0.2 dex. We apply this method to 10 pair systems at z=6-8 with [O III] spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES). We infer the
stellar-to-
halo mass relation while marginalizing over projection effects, measurement uncertainties, and intrinsic scatter. We find a mean
halo mass of $\log\,(M_{200}/M_\odot)=11.06\pm0.21$ at $\log\,(M_{*}/M_\odot)=9$. These
galaxies do not appear to inhabit unusually massive
halos. Our results instead indicate a high
stellar-to-
halo mass ratio, corresponding to an integrated
star formation efficiency of $5^{+3}_{-2}\%$, about twice the TNG100 prediction, although the current statistical significance is limited. Future observations with larger samples will tighten these constraints and directly examine whether enhanced
star formation efficiency drives the overabundance of luminous
galaxies at
cosmic dawn.
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All authors Zihao Wu, Daniel J. Eisenstein, Benjamin D. Johnson, Lars Hernquist, Sandro Tacchella, Brant E. Robertson, Santiago Arribas, Andrew J. Bunker, Qiao Duan, Jakob M. Helton, Zhiyuan Ji, Dávid Puskás, Pierluigi Rinaldi, Fengwu Sun, Hannah Übler, Yongda Zhu
Plasma Physics
Pellet-Size Scaling of Quasi-Steady-State Plasma Performance in Wendelstein 7-X
Keisuke Fujii, Edgardo Villalobos Granados, Maryam Huck et al. (+11 more)
A continuous cryogenic-pellet injector has been used to realize long-pulse high-performance
plasmas in Wendelstein 7-X (W7-X). A hydrogen ice pellet deposits particles directly in the confined region. If the particles are deposited sufficiently far inside the
plasma, they produce a density gradient that suppresses ion-temperature-gradient
turbulence and improves
plasma confinement. However, after multiple pellets have been injected and the
plasma density and temperature have increased, the
plasma performance begins to saturate. In this work, we analyze multiple pellet-injection experiments conducted in 2024 and 2025, during which the injected pellet sizes varied unintentionally. This analysis reveals a positive correlation between pellet size and the quasi-steady-state stored energy of W7-X
plasmas. Although this pellet-size dependence can be understood qualitatively from pellet-ablation physics, the measured deposition position differs quantitatively from the neutral-gas-shielding (NGS) model prediction. This discrepancy suggests significant inward transport of the pellet cloud. The trend identified here suggests that injection of even larger pellets could further improve
plasma performance.
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All authors Keisuke Fujii, Edgardo Villalobos Granados, Maryam Huck, Jürgen Baldzuhn, Naoki Tamura, Steven Meitner, Larry Baylor, Golo Fuchert, Kai Jakob Brunner, Jens Knauer, Ekkehard Pasch, Jannik Wagner, Bart Lomanowski, W7-X Team
Mathematical Physics
Monodromy Eigenvectors for Difference Equations with Root-of-Unity Step
Vitaly Tarasov and Alexander Varchenko
A qKZ-type discrete flat connection with multiplicative step $p$ has monodromy operators when $p$ is a root of unity. The monodromy operators are commuting endomorphisms of the connection. We construct their eigensections and
eigenvalues. The construction is based on the presentation of the discrete flat connection as a discrete Gauss-Manin connection.
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Materials Science
A Multipolar Approach to Sliding Ferroelectricity
Matthew Dykes
Traditional theoretical treatments of ferroelectricity do not straightforwardly extend to sliding ferroelectrics, which are increasingly-studied layered materials where a switchable electrical polarization is controlled by two-dimensional relative motion of the stacked layers. Therefore, in-depth analyses of the underlying processes which dictate their polarization behavior remain challenging. In this paper, we present a comprehensive approach for identifying the
symmetry-adapted microscopic parameters which are responsible for driving the emergence of this polarization. First, we outline our approach, which appeals to group theory arguments and the distortion of Wannier orbital densities to connect macroscopic
symmetries to the microscopic electronic distortions which dictate the appearance of ferroelectricity. Then, we illustrate this process by using density functional theory to apply our strategy to honeycomb
bilayer systems, including hexagonal boron nitride. In this way, we find that combinations of dipole-like and quadrupole-like distortions of lone pair electron orbitals control electronic reorganization, and by extension, ferroelectricity in such systems.
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High Energy Physics (Experiment)
Similarity Pairing with Energy Mover's Distance for Self-Supervised Pre-Training at the LHC
Ho Fung Tsoi and Dylan Rankin
Many self-supervised methods for training foundation models at the Large
Hadron Collider (LHC) rely on data augmentations to encourage the model to embed events into a representation space invariant to certain physical or detector
symmetries. A common challenge arises from the large freedom in choosing a proper set of augmentations on which downstream performance depends. The implementation of augmentations involves either modifying existing events, potentially breaking the event fidelity, or simulating more event variants, which is computationally intensive. In this work, we present a data-driven method of pairing events by their similarity via the energy mover's distance (EMD), which measures how similar two events are in terms of the work required to transform one into the other. With this approach, distinct events are sampled and matched by their similarity to serve as views for learning invariance, keeping the physics content of each event intact without handcrafted distortions. We demonstrate this augmentation-free pairing method by pre-training on QCD jets via self-
distillation and show that it can yield semantic jet
embeddings with downstream discrimination power comparable to or better than an augmentation-based baseline.
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Solar and Stellar Astrophysics
Two Kepler red-giant eclipsing binaries as lower red-giant branch benchmarks for asteroseismic scaling relations. Dynamical masses and radii from JKTEBOP and PHOEBE-2 modeling
A. Hedlund, P. Gaulme, J. Jackiewicz et al. (+2 more)
Space-based photometry has detected
solar-like oscillations in thousands of
stars, whose global seismic parameters yield
stellar properties via the asteroseismic scaling relations. Because these relations systematically overestimate red-
giant masses and radii empirical calibration is required. Double-lined eclipsing binaries hosting oscillating red
giants provide precise dynamical masses and radii without external calibration, making them ideal
benchmarks. We present KIC 8129189 and KIC 10920813, two Kepler eclipsing binaries containing less-evolved oscillating red
giants, as new
benchmarks that extend the calibration sample toward smaller radii. We measured radial velocities from high-resolution spectra, extracted global asteroseismic parameters from Kepler light curves, and modeled the binaries with JKTEBOP and PHOEBE-2 using both full light curves and selected eclipse sets, adopting
benchmark masses and radii from the envelope of tested model/data configurations. We then fit correction factors $f_{\Delta\nu}$ and $f_{\nu_{max}}$ to the underlying $\Delta\nu$-density and $\nu_{max}$-surface-
gravity relations. We obtain $M_{RG}=1.413 \pm 0.037 M_\odot$ and $R_{RG}=4.296 \pm 0.061 R_\odot$ for KIC 8129189, and $M_{RG}=1.383 \pm 0.022 M_\odot$ and $R_{RG}=5.914 \pm 0.043 R_\odot$ for KIC 10920813. The adopted 15-
star calibration gives $f_{\Delta\nu}=0.9777 \pm 0.0048$ and $f_{\nu_{max}}=1.024 \pm 0.008$, corresponding to $C_M=0.850 \pm 0.020$ and $C_R=0.9333 \pm 0.0090$. Neither correction factor depends significantly on radius, nor does $f_{\nu_{max}}$ depend on
metallicity; model-based $f_{\Delta\nu}$ values are systematically lower than the dynamically derived ones. Both systems agree with the correction from previous
benchmarks, showing that continued expansion of the eclipsing-binary sample is essential for testing the scaling relations across evolutionary stage.
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All authors A. Hedlund, P. Gaulme, J. Jackiewicz, T. Appourchaux, E. Guenther
Computational Physics
Machine learning kinetics from molecular dynamics data
Jonathan Weare and Aaron R. Dinner
Most molecular transitions occur on time scales far beyond direct molecular dynamics simulations. The committor, the probability that a configuration reaches a product state before a reactant state, is a central kinetic statistic, providing a mechanism-independent reaction coordinate and a foundation for transition path theory and the calculation of rates. This review surveys modern approaches for estimating the committor and related kinetic statistics from molecular simulations, with an emphasis on self-supervised methods that learn solutions of their defining dynamical equations rather than relying on labeled shooting data. We develop a common operator viewpoint connecting generator-based partial differential equations, variational principles, Markov state models, dynamical Galerkin approximation, and neural networks. Empirical and theoretical evidence points to the efficiency of these methods. We provide theoretical and practical guidance for realizing their full potential in applications, including strategies for treating non-Markovian effects and for sampling. We conclude by identifying opportunities for further research, including connections to reinforcement learning and generative modeling.
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Fluid Dynamics
Beyond capillarity: extended interfacial energy transfer in bubble-laden turbulence
Andrea Montessori
Capillary forces are commonly regarded as an energetically closed channel in multiphase
turbulence, redistributing kinetic energy across scales without net gain or loss. Here we show that this picture breaks down in bubble-laden
turbulence when short-range near-contact interactions are active. A spectral analysis of the kinetic-energy budget reveals that the cumulative capillary power does not vanish at statistical stationarity, but instead retains a finite negative residual. This apparent imbalance is exactly compensated by the work of short-range repulsive forces, which is negligible at large and intermediate scales and becomes positive only at small scales. Near-contact interactions therefore open a distinct small-scale pathway in the interfacial energy transfer, rather than acting as a mere regularization of unresolved thin films. The proper scale-by-scale description is thus an extended interfacial transfer, combining capillary and near-contact work, rather than a purely capillary one.
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Accelerator Physics
First Cobotic-Assisted String Assembly of PIP-II SSR2 Cavities at Fermilab
M. Parise, T. Aiazzi and C. Narug
Achieving robotic-assisted string assembly has been a longstanding objective in superconducting cavity pro-duction to improve precision, repeatability, and through-put while reducing operator-dependent variability. At Fermilab, robotic systems have been successfully deployed for the installation of individual components on SSR2 cavities inside a cleanroom environment. The single-cavity installations validated the feasibility of robotic techniques and provided confidence to extend automation to the assembly of a full prototype cavity string. Leveraging lessons learned from earlier operations, the robotic system was adapted for the string assembly. This work describes the robotic-assisted assembly process in detail, including
alignment strategies for coupler flanges, torque control for bellows connections, and mitigation of particulate generation in cleanroom conditions. Performance metrics of the cryomodule are presented, together with an analysis of improvements needed for robotic assembly. The effort also represents a broader R&D initiative at Fermilab to the long-term goal of scalable SRF cryomodule production.
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Solar and Stellar Astrophysics
The Solar Neighborhood LVI: The RMSTAR Catalog of the Nearest 3352 M Dwarf Systems and 305 of their Wide Companions
Madison R. LeBlanc, Tim M. Johns, Todd J. Henry et al. (+8 more)
We present the RMSTAR (RECONS M
STAR) catalog, a 25 pc volume-limited and effectively volume-complete sample of the nearest 3352 M
dwarf systems and their 305 wide
stellar and 9 brown
dwarf companions. RMSTAR has been created using only results from
Gaia Data Releases 3 (GDR3) and 2 (GDR2), Hipparcos, and ground-based discoveries of M
dwarf systems that are not available in the space-based results. The wide companions are identified using only results from GDR3 and GDR2, and have separations $\rho\ge0.''46$. There are 291 primaries with
stellar companions, yielding a multiplicity rate of 8.68$\pm$0.49% for these widely separated systems, with a rate of 6.86$\pm$0.44% for projected separations $s\geq30$ au, where the sample of
stellar companions is complete except perhaps for a few fringe cases. It is shown that the rate of
stellar companions increases from the search limit of 30,000 au down to separations of 30 au, with a large set of companions to be characterized at closer separations in future work. We determine luminosity and mass functions for all
stellar red
dwarfs and their wide secondaries, finding that the luminosity function displays a classic turnover at $M_G\sim11$, whereas the mass function is described by an exponential function that rises from 0.60 M$_{\odot}$ to the end of the
stellar main sequence at 0.075 M$_{\odot}$. We assess the large population of close, unresolved companions to M
dwarfs by analyzing several
Gaia parameters, identifying 1089 (30%) individual sources as having at least one of these elevated unresolved companion indication parameters.
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All authors Madison R. LeBlanc, Tim M. Johns, Todd J. Henry, Kenneth J. Slatten, Jennifer G. Winters, Wei-Chun Jao, Aman Kar, Michele L. Silverstein, Eliot Halley Vrijmoet, Casey Rush, Andrew A. Couperus
General Relativity and Quantum Cosmology
Scalar quasinormal and quasibound states of weakly magnetized Ernst–Schwarzschild spacetime: a confluent-Heun Wronskian approach
Danilo S. Ferreira and Luis B. Castro
We study the quasinormal-mode and quasibound-state spectra of a massless scalar field in weakly magnetized Ernst–Schwarzschild spacetime. In the separated $O(B_0^2)$ regime, the Klein–Gordon equation reduces to a radial confluent-Heun equation. We construct an endpoint-selected spectral Wronskian directly from the canonical confluent-Heun recurrence and its regular-to-irregular connection limit. Quasinormal modes and quasibound states are then obtained as zeros of the same analytic spectral function on the radiative and bound sheets, respectively, providing a unified treatment of the two spectral sectors within the separated weak-field problem. The resulting QNM and QBS frequencies agree with independent weak-field Ernst and massive-Schwarzschild
benchmarks available in the literature. We further show, for representative cases, that the frequencies selected by the local Heun-series termination relation examined here do not satisfy the endpoint-selected quasibound-state condition. The construction therefore provides a direct horizon-to-infinity spectral condition for both radiative and bound states within the weak-field Ernst problem.
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High Energy Physics (Experiment)
Self-Supervised Learning for Robust Resonance Mass Regression in Cascade Decays
Ho Fung Tsoi, Alex Yang, Luis Felipe Gutierrez Zagazeta et al. (+2 more)
Reconstructing the mass of a heavy resonance from its decay products with missing energy is one of the central tasks that directly determine the sensitivity in new physics searches at
collider experiments. Supervised learning approaches to this problem often struggle to generalize well due to the presence of various systematic uncertainties and distribution shifts. Exhausting all possible variations in the labeled data can be very compute-intensive, while a failure of the model to generalize can corrupt the reconstructed resonance widths that are critical in peak-hunting analyses. In this work, following the foundation model paradigm, we use a self-supervised approach to pre-train a
transformer encoder with VICReg to learn an
embedding invariant to various corruptions, then fine-tune it for mass regression on a heavy resonance with masses ranging from 2.5 to 6.5 TeV and a SUSY-like cascade decay into an eleven-body final state. We show that the pre-trained model reconstructs sharper resonance peaks and has a more stable performance under various realistic corruptions, compared to a supervised model of the same architecture trained on the same augmented data from scratch.
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All authors Ho Fung Tsoi, Alex Yang, Luis Felipe Gutierrez Zagazeta, Shion Chen, Dylan Rankin
Lattice Field Theory
Testing strong isospin breaking effects in QCD thermodynamics
D. A. Clarke and B. B. Brandt
Most modern
lattice QCD calculations take the masses of the light
quarks to be degenerate, setting $m_u=m_d$, a choice that, while not physical, increases computational efficiency and lowers the complexity of simulations and analysis. For many observables, the systematic error associated with this simplification is expected to be negligible, as $\Delta m_{ud}=m_d-m_u$ is significantly below the QCD scale. So far
lattice studies have examined the role of strong isospin breaking (SIB) in
hadron mass splittings, but SIB effects in thermodynamic observables have only been studied in terms of the crossover temperature with unphysically heavy
quarks. Motivated by the recent observation of an unexpectedly large ratio between the abundances of charged versus neutral kaons in heavy-ion collision experiments, we investigate the effects of SIB in QCD thermodynamics by computing observables for three non-degenerate
flavors ($N_f=1+1+1$) with physical
quark masses using dynamical improved staggered
fermions. In particular, we investigate the difference between the $u$- and $d$-
quark condensates and extract the pseudocritical temperature, the equation of state, and conserved-charge fluctuations, comparing results to standard $N_f=2+1$ simulations.
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High Energy Physics (Theory)
Fixed Points, Floquet Entanglement Asymmetry, and Quantum Mpemba Effects
Jayashish Das, Filiberto Ares and Arnab Kundu
We investigate the dynamics of
entanglement asymmetry in periodically driven two-dimensional conformal field theories with a global U$(1)$
symmetry, using a dynamical-system description based on iterated conformal maps, in particular Möbius maps. Starting from a
symmetry-breaking excited state prepared by a local operator insertion, we show that a broad range of nonequilibrium phenomena, including local
symmetry restoration, the
quantum Mpemba effect, and its inverse, admit a simple
geometric description in terms of the invariant data of the conformal map. We explicitly demonstrate this using Möbius maps, for which the invariant structure is described by the conjugacy classes. In particular, the dynamics of
entanglement asymmetry is determined by the relative positions of the state-preparing operator insertion, the subsystem, and the fixed points, yielding distinct patterns of growth, decay, oscillation, and saturation. We further argue that this
geometric picture extends to general holomorphic maps, establishing the conformal-map dynamics as a natural framework for organizing the phenomenology of
entanglement asymmetry in periodically driven two-dimensional conformal field theories.
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High Energy Astrophysical Phenomena
Uncovering New Ionized Winds and Relativistic Hot Outflows in MCG-6-30-15 with Chandra HETG and a Bayesian Framework
Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds et al. (+1 more)
Active
Galactic Nuclei (AGN) feedback plays a key role in
galaxy evolution. Highly ionized
outflows, detected in X-ray absorption, are a promising candidate for
quasar-mode feedback. We present a new
Bayesian analysis of 0.65 Ms of Chandra High Energy Transmission Gratings (HETG) observations of MCG-6-30-15 from 2000 and 2004. Our approach detects new wind components, improving estimates of
outflow demographics and impact. These include a hot ultra-fast
outflow (UFO; 0.08c), recently confirmed by XRISM but seen in HETG for the first time, which has the power to potentially influence its host
galaxy. We also detect the first potentially collisionally ionized absorbers in this source, a physical process typically not considered in previous analyses, but potentially important for wind impact and demographics. The warm absorber complex is resolved in unprecedented detail, uncovering evidence of a correlation between
outflow velocity and ionization, constraining its geometry. We also confirm the presence of
dust in the wind, clearly distinguishing it from the cold ISM components, which may impact wind acceleration. Our work highlights the power of applying new methods to deep, legacy HETG
datasets, and the limitations of current atomic databases when considering OIV, V, and VI K-shell transitions. Furthermore, our work establishes a baseline for decade-scale
outflow variability for new observations with XRISM and NewAthena in the future.
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All authors Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds, Lia Corrales