Atomic Physics
Surface-Induced Spectral Broadening during Efficient Two-Photon Excitation of Cold $^{133}\text{Cs}$ Atoms near an Optical Nanofiber
Yuan Jiang, Xiaodong Qi, Nicolás Vera Paz et al. (+5 more)
We report the experimental observation of the $^{\text{133}}$Cs 6S$_{\text{1/2}}$ to 6D$_{\text{5/2}}$ single-frequency two-
photon transition at low excitation power using an optical nanofiber embedded in a cold atom cloud. We investigate the 917 nm fluorescence spectra modified by the surface-induced interaction of the nanofiber, which exhibits a pronounced asymmetric broadening with a distinct red-shifted tail. We present a systematic theoretical description of the two-
photon transition process of atoms near a nanofiber surface, considering atomic angular momentum coupling, guided-mode decay rate, and surface-induced van der Waals interactions. Owing to the tight spatial confinement provided by the guided evanescent field, efficient nonlinear excitation is realized at excitation powers down to tens of microwatts, corresponding to a reduction of approximately four orders of magnitude relative to typical free-space implementations. Our work reveals the interplay among waveguide-modified radiative dynamics, surface-induced interactions, and the spatial distribution of atoms around the nanofiber, and provides insights into further studies on nonlinear optical transitions and surface-mediated atomic dynamics in waveguide
quantum electrodynamics systems.
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All authors Yuan Jiang, Xiaodong Qi, Nicolás Vera Paz, Yilin Chen, Tanbin Wu, Dianqiang Su, Pablo Solano, Yanting Zhao
Mathematical Physics · Cross-listed from math.AP
Kruskal-style algorithm for Boltzmann equation molecule reduction
Yvain Bruned and Valentin Clarisse
We are interested in the molecule reduction
algorithm used by Deng, Hani and Ma. This
algorithm allows them to establish a
rigidity theorem, which plays a central role in the long-time derivation of the Boltzmann equation using the hard-sphere dynamics. In the present article, we show that this
algorithm is a graph traversal
algorithm of Kruskal type, and we prove that it constructs a Kruskal spanning tree of the input molecule.
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Quantum Physics
Classical Verification of Quantum Computation with Quasilinear Resources, from Compiled Nonlocal Games
Finn Holler and Anand Natarajan
Computational self-testing gives a classical verifier command over the
quantum register of a single computationally bounded prover. We use this framework to construct the first argument system for BQP with quasilinear total resource requirements in the
circuit model. Our argument system is based on the learning with errors (LWE) assumption and requires total resources of $O(\mathrm{poly}(\lambda, \log g)\cdot g)$ for delegating a
circuit with $g$ gates, where $\lambda$ is the LWE security parameter. This is achieved by constructing a new computational self-test for certifying the prover's
quantum state and using it to dequantize the efficient verification protocol of Broadbent (ToC 2018). Specifically, this self-test enables the verifiable, random remote state preparation of tensor product states of the single-
qubit Clifford observables $\sigma_X, \sigma_Y, \sigma_Z, (\sigma_Y-\sigma_X)/\sqrt{2}$ and $(\sigma_Y+\sigma_X)/\sqrt{2}$, with constant robustness: the verification error is independent of the number of prepared
qubits. This approach was first proposed by Coladangelo et al. (ToC 2024) in the multi-prover setting. We replicate their result in the single-prover setting by applying the compiler proposed by Kalai et al. (STOC 2023)—which turns any nonlocal game into a single-prover argument system—to a modified version of their self-test.
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Nuclear Theory
Bayesian Constraints on Bosonic Dark Matter in Neutron Stars within a Covariant Density-Functional Equation-of-State Ensemble
Davood Rafiei Karkevandi, Alexander Ayriyan and Armen Sedrakian
We investigate
neutron stars admixed with repulsively self-interacting bosonic dark matter (DM) using current multi-messenger observations. The dark component is modeled as a complex scalar field coupled to baryonic matter only through
gravity, allowing dark-core and dark-
halo configurations. To quantify baryonic equation-of-state (EOS) uncertainties, we combine a three-dimensional scan over $(m_\chi,\lambda,F_\chi)$ with 27 DDME2-based covariant density-functional EOSs spanning $L_{\rm sym}=30,50,70$ MeV and $-600\le Q_{\rm sat}\le 1000$ MeV. The models are confronted in a
Bayesian framework with NICER mass–radius measurements from the Amsterdam and Maryland/Illinois analyses and the GW170817
tidal-deformability constraint. After
Bayesian evidence weighting over the EOS ensemble, the EOS-relevant dark-sector scale $\mu_\chi\equiv m_\chi/\lambda^{1/4}$ is localized around 250 MeV for both NICER data sets. In the $(m_\chi,\lambda)$ parameterization, the marginalized
boson-mass posterior peaks at $m_\chi\simeq300$–$330$ MeV, while $\lambda$ remains broadly distributed. Since the bosonic EOS depends on $m_\chi$ and $\lambda$ only through $\mu_\chi$, their separate marginals are conditional on the adopted independent priors. The inferred DM fraction is more data-set dependent, with posterior modes near 4% for Maryland/Illinois and 12% for Amsterdam. Bosonic DM also shifts the inferred $Q_{\rm sat}$ from negative toward intermediate and positive values, whereas the response of $L_{\rm sym}$ is weaker. This indicates a model-dependent trade-off between DM-induced compactification and the high-density stiffness of baryonic matter. These constraints remain conditional on the selected EOS family and the assumption of a common effective $F_\chi$ for all sources.
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High Energy Physics (Theory)
Logarithmic gravity from a very slow roll limit of inflation
Jordan Cotler, Victor Ivo and Juan Maldacena
We study the inflationary no-boundary wavefunction in a “linear-roll limit,” in which $G_N \to 0$ while the Hubble scale $H$ and the slope of the inflaton potential are held fixed. Although bulk graviton fluctuations are suppressed in this limit,
quantum inflaton fluctuations remain finite. Because reheating occurs on a surface of fixed inflaton value, these fluctuations become fluctuations of the conformal factor of the reheating metric. The probability measure for these fluctuations simplifies drastically and becomes Gaussian, even for large fluctuations. The resulting log-correlated theory at superhorizon scales is a $d$-dimensional analog of Liouville
gravity without the exponential potential, which we call Logarithmic
Gravity. The quadratic and linear terms are determined by conformally covariant scattering data; in even dimensions we relate them to the critical GJMS operator and Branson $Q$-
curvature. From bulk unitarity, we argue that one-loop effects do not generate additional conformal-factor dependence in the physical probability measure, and we verify the cancellation explicitly in $2 + 1$ dimensions. For the no-boundary norm with a rolling inflaton, we show that the noncompact residual conformal
symmetries can be gauge fixed with a finite Faddeev-Popov determinant, so they do not force the sphere contribution to vanish. In addition, conditioning on the absence of
vacuum decay by bubble nucleation generates the Liouville exponential potential in the probability measure.
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High Energy Physics (Phenomenology)
Self-interacting $O(N)$ scalar dark matter multiplet in a Higgs-portal model with a light scalar mediator
U-Rae Kim, Jungil Lee and Soo-hyeon Nam
We investigate self-interacting dark matter in an $O(N)$-symmetric real scalar multiplet model with
Higgs-portal interactions involving the Standard Model
Higgs and a real singlet scalar. After spontaneous breaking of the singlet $\mathbb{Z}_2$
symmetry, the singlet scalar mixes with the SM
Higgs boson. We focus on the regime where the resulting light scalar serves as a mediator, leading to sizable and velocity-dependent self-interactions. We impose constraints from
Higgs measurements, rare $B$-
meson decays, the dark matter relic abundance,
spin-independent direct-detection searches, and scalar coupling perturbativity. We find viable parameter regions in which destructive interference between scalar-mediated scattering amplitudes suppresses the direct-detection cross section while allowing self-interactions relevant to
dwarf-
galaxy scales. Among these viable parameter regions, a subset also satisfies electroweak
vacuum stability up to the Planck scale. Finally, we show that future long-lived-particle searches can probe part of the viable parameter space, providing complementary tests of
Higgs-portal self-interacting dark matter with a light scalar mediator.
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Mesoscale and Nanoscale Physics
Interlayer Fermi Polarons in Bilayer MoTe$_2$
Ruihao Ni, Eugen Dizer, Maximilian Wolf et al. (+15 more)
Atomic
bilayers of transition metal dichalcogenides (TMDs) host
quantum phases governed by the layer degree of freedom, including
bilayer Wigner
crystals, fractional Chern
insulators, and
exciton condensates. These phases are probed primarily through
exciton spectroscopy, yet it remains poorly understood how
excitons and carriers interact to form
Fermi polarons in
bilayers, where both the
impurity and the
Fermi sea carry a layer pseudospin. Progress has been limited because most TMD
bilayers have momentum-indirect optical bandgaps, in which non-radiative decay and inhomogeneous broadening obscure the intrinsic spectra. Here, we show that
bilayer MoTe$_2$, unlike most TMD
bilayers, retains a direct optical bandgap, providing a clean platform for studying
bilayer Fermi-polaron physics. In a dual-gated device, an out-of-plane electric field continuously tunes the hybridization between intralayer and interlayer
excitons, forming layer-coherent
excitons. Upon electrostatic doping, the excitonic spectrum evolves into multiple polaron branches, controlled by both carrier doping and the out-of-plane electric field. Among these, we identify a polaron with no analog in monolayers, in which a layer-coherent
exciton is dressed by carriers in the opposite layer, and is quantitatively captured by our field-theoretic model. Our results establish that pseudospin structure in both the
impurity and the bath reshapes polaron formation, opening new avenues to many-body states such as Bose-Einstein condensates with interlayer coherence.
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All authors Ruihao Ni, Eugen Dizer, Maximilian Wolf, Son T. Le, Sharadh Jois, Jeffrey J. Schwartz, Liuxin Gu, Rundong Ma, Suji Park, Beini Gao, Lifu Zhang, Houk Jang, Takashi Taniguchi, Kenji Watanabe, Aubrey T. Hanbicki, Adam L. Friedman, Richard Schmidt, You Zhou
Quantum Physics
A Tale of Two Walks: Kipnis, Marchioro and Presutti Meet Kac in a Quantum World
Qian Chen, Jingcheng Liu, Minglong Qin et al. (+4 more)
We reveal an unexpected connection between the parallel Kac's walk and the Kipnis-Marchioro-Presutti (KMP) process. The twirling channel induced by the parallel Kac's walk on the symmetric subspace is exactly encoded by a classical Markov chain on partitions, which lifts to a parallel KMP process on complete graphs. This correspondence reduces the analysis of the twirling channel to the mixing of the parallel KMP process. We prove that $O(\log d+\log(1/\varepsilon))$ repetitions suffice to approximate Haar twirling on the symmetric subspace of $(\mathbb C^d)^{\otimes t}$ to error $\varepsilon$, uniformly in the number of copies $t$. For the standard KMP process on general graphs, we prove a mixing-time analogue of Aldous's
conjecture: at fixed accuracy, the mixing time of the $t$-particle process is at most a constant times the single-particle mixing time multiplied by the logarithm of the number of vertices, uniformly in $t$. As an application, we improve the total variation mixing-time bound for coordinate hit-and-run on the $n$-dimensional standard simplex from $\widetilde O(n^3)$ (Kook and Vempala, 2026) to $\widetilde O(n)$, while removing the dependence on the initial distribution. Our main technical contribution is conditional product structure for both parallel and standard KMP processes. Conditioned on suitable auxiliary randomness, the labeled particles evolve independently. Combining this structure with an exact coupling yields mixing bounds uniform in the number of particles for both unlabeled KMP models. These bounds are sharp up to logarithmic factors and imply rapid convergence of the parallel Kac twirling channel on the symmetric subspace.
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All authors Qian Chen, Jingcheng Liu, Minglong Qin, Leonard Schulman, Fang Song, Penghui Yao, Mingnan Zhao
Astrophysics of Galaxies
Detecting HI Self-Absorption using Neural Networks
Eric G. M. Muller, Naomi M. McClure-Griffiths, Hiep Nguyen et al. (+5 more)
Cold atomic hydrogen plays a crucial role in the life cycle of interstellar gas. It serves as the intermediary phase in the condensation and cooling processes that bridge the warm diffuse gas in and around
galaxies, and the cold molecular gas that drives
star formation. HI self-absorption in the 21-cm emission line is the most direct observational tracer of cold HI gas that does not require a continuum background source, yet its systematic extraction remains a long-standing challenge. Existing methods of self-absorption identification rely on subjective by-eye inspection or modelling of the underlying emission, making repeatable, thorough, and large-scale applications difficult. We present a lightweight convolutional neural network designed to detect self-absorption features and infer their velocities via a post-hoc process, without assumptions about the underlying emission or the use of ancillary data. Trained on synthetic emission spectra, the neural network achieves 96.5 per cent accuracy, 96.0 per cent precision, and 97.0 per cent recall on held-out synthetic data. Applied to observed 21-cm emission data from the Riegel–Crutcher cloud and
giant molecular filament regions towards the
Galactic Plane, the network recovers the spatial distributions and velocities of known self-absorption structures when compared to previous analyses and ancillary 13CO emission data. Crucially, the neural network is computationally efficient, processing detections for ~15,000 spectra per second on a single consumer laptop GPU, enabling real-time cold HI detection at the data rates anticipated by next-generation facilities such as the Square Kilometre Array.
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All authors Eric G. M. Muller, Naomi M. McClure-Griffiths, Hiep Nguyen, Matthew J. Alger, Frances Buckland-Willis, J. R. Dawson, Min-Young Lee, Antoine Marchal
High Energy Astrophysical Phenomena
Science Using Single-Pulse Exploration with Combined Telescopes: II. Pulse profile evolution and single-pulse modulation
F. Jankowski, J.-M. Griessmeier, T. Roy et al. (+11 more)
Aims. We aim to illuminate how the
pulsars' integrated pulse profiles and single-pulse modulation evolve with
radio frequency, while separating intrinsic and propagation effects. Methods. We present integrated pulse profiles and phase-resolved modulation indices for 12
radio pulsars at up to five frequency bands. Our wideband
dataset was systematically acquired with the Nancay
Radio Observatory
telescopes and the uGMRT, covering the frequency range 10 MHz to 2.8 GHz, including NenuFAR, LOFAR FR606, uGMRT, and NRT observations. We carefully measured the pulse widths and scattering times using multi-component profile fitting. We employed a profile width scaling model to separate the profile
evolution into scattering and intrinsic contributions. We quantified the
pulsars' single-pulse variability across frequency. Results. We describe the pulse profile
evolution. Two
pulsars have scattering indices compatible with Kolmogorov
turbulence, while the majority have flatter scattering indices. This suggests complex scattering environments, dominated by localised
turbulence. Complex scattering behaviour is seen in some
pulsars, and most profiles are scattering-dominated below 200 MHz. The measured intrinsic power law indices are small, with absolute values between 0 and 0.3. Five
pulsars exhibit decreasing intrinsic widths, two or three
pulsars show flat behaviour, and four
pulsars have increasing profile widths with frequency. Accounting for biases, most
pulsar modulation parameters decrease with frequency, while three
pulsars show flat behaviour. Conclusions. The pulse width
evolution is explained by intrinsic
radio beam narrowing, the emergence of profile components, and the balance between the two. Our modulation analysis indicates that the single-pulse emission from most of our
pulsars becomes more erratic towards lower
radio frequencies, consistent with increasing amplitude modulation.
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All authors F. Jankowski, J.-M. Griessmeier, T. Roy, M. Surnis, G. Theureau, L. Bondonneau, P. Noe, J. Petri, L. Guillemot, I. Cognard, M. Serylak, I. Kravtsov, V. Zakharenko, O. Ulyanov
Quantum Physics
Universal quantum coding
Jacopo Rizzo, Ludovico Lami, Jens Eisert et al. (+1 more)
Entanglement distillation from noisy bipartite states and reliable
quantum communication over noisy channels are fundamental tasks in
quantum information theory, yet optimal coding schemes typically rely on prior knowledge of the underlying state or channel. Here, through Schur-Weyl duality, we establish a universal
quantum error-correction principle that removes this dependence entirely. We show that the irreducible permutation spaces arising from the local Schur-Weyl decomposition of many identical copies of an unknown bipartite mixed state form maximally entangled
quantum code spaces, with an error structure determined entirely by representation theory. Correcting these
symmetry-resolved errors yields universal protocols for
entanglement distillation and
quantum communication that achieve coherent-information rates with exponentially vanishing error and optimal second-order correction. The protocols are invariant under local
unitaries and allow both input marginals to be recovered exactly. At finite block length, their achievable rates are governed by an associated Schur-Weyl information spectrum, which we relate to Petz-Rényi conditional
entropies of the underlying state. The resulting sample complexity depends only on the relevant spectral ranks, rather than on the respective
Hilbert space dimensions. In particular, for $n$-
qubit states of $O(\operatorname{poly} n)$ global rank, we show that a Petz-Rényi conditional-
entropy promise suffices for optimal sample-efficient
entanglement distillation. Altogether, these results identify Schur-Weyl duality as a fundamental and general mechanism for optimal,
tomography-free universal
quantum coding, placing
entanglement distillation,
quantum error correction and
quantum communication within a unified representation-theoretic framework.
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All authors Jacopo Rizzo, Ludovico Lami, Jens Eisert, Lorenzo Leone
Physics and Society
Emergence in Network Systems is Bounded by Boundary-Crossing Paths
Johnny Jingze Li and Gabriel A. Silva
Emergence, features of a whole that no part shows alone, is central to complex systems but rarely measured so as to locate its source. Viewing a system structurally, as a network of interacting parts, we evaluate emergence as what observing the coupled whole reveals beyond, or erases from, the combined observations of the parts. For observations that build what they see route by route, we show that every emergent feature is produced by its own route across the interface between parts, a route that traces it to the components and interactions responsible. We show the number of all such boundary-crossing paths bounds the total emergence discrepancy, and equals the emergence of measures that count routes. The bound is computed locally around the interface, validated through network examples, and in a nervous system the routes show that interneurons relay most of the emergence. Our work associates emergence with path structure in the network system that can be anticipated, attributed, and engineered.
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Mesoscale and Nanoscale Physics
Rundong Ma, Konstantin Davydov, Liuxin Gu et al. (+9 more)
Interlayer
excitons in transition metal dichalcogenide (TMD)
heterostructures exhibit long lifetimes and long-range transport, making them promising for excitonic devices and
quantum many-body phases, such as Bose-Einstein condensates. Achieving these goals requires a precise understanding of
spin-allowed bright and nominally
spin-forbidden dark
excitons, because the lowest-energy
exciton species governs population, transport, and condensation. Despite substantial progress, unambiguously distinguishing singlet and triplet interlayer
excitons has been challenging, as moiré
excitons in these
heterostructures can mimic their optical signatures. Here, we report the direct spectroscopic identification of bright (singlet) and dark (triplet) interlayer
excitons in high-quality, dual-gated WSe$_2$/hBN/WSe$_2$ homobilayers. Electric-field-dependent photoluminescence and reflectance reveal two momentum-direct interlayer transitions with distinct
spin configurations. The interlayer dark
excitons obey selection rules that differ from those of bright
excitons. Strikingly, interlayer dark
excitons retain strong valley polarization, even with their ultralong lifetime exceeding microseconds. Finally, we demonstrate twist-angle control, wherein twist-induced electron-hole momentum mismatch modulates interlayer
exciton emission. These results provide critical insights into the electronic and excitonic structure of TMD
heterostructures, opening new avenues for excitonic many-body physics and optoelectronic devices.
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All authors Rundong Ma, Konstantin Davydov, Liuxin Gu, Lifu Zhang, Hassan Alnatah, Beini Gao, Ruihao Ni, Suji Park, Houk Jang, Takashi Taniguchi, Kenji Watanabe, You Zhou
High Energy Physics (Theory)
Diagrammatic construction of GKZ systems for polygonal functions
K.B. Alkalaev, Semyon Mandrygin and Y.M. Zalishchansky
We investigate the recently introduced polygonal hypergeometric functions [arXiv:2502.12127, arXiv:2507.01904], which are conjectured to evaluate multipoint parametric one-loop conformal integrals in arbitrary dimensions. These functions can be systematically constructed using a diagrammatic
algorithm that operates in terms of simple planar shapes. Given an $n$-point polygonal power series, we formulate the corresponding GKZ hypergeometric system, which admits an explicit diagrammatic interpretation. In particular, the transianic
matrix, which encodes all the relevant diagrammatic data, determines the corresponding toric
matrix along with a basis of the
lattice of relations, thereby singling out a finite subsystem of $n(n-3)/2$ toric equations. This finite subsystem consists of second- and third-order equations, whereas the full toric family also includes higher-order ones. We illustrate the general procedure with several prominent examples of polygonal functions, including the fourth Appell and the Srivastava–Daoust functions.
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High Energy Physics (Experiment)
Overview of the HL-LHC CMS outer tracker upgrade and lessons learned from 2S module production
F. Zhang
For operation at the High-Luminosity LHC, the CMS collaboration is developing a significantly enhanced silicon detector system with improved radiation hardness, higher granularity, and extended coverage up to a pseudorapidity of $|\eta|\approx$ 4. The Outer Tracker will be equipped with two types of modules (2S and PS) that will provide tracking information to the L1 trigger of the HL-LHC CMS detector, by rejecting signals from particles below a certain transverse momentum threshold. Hence, these modules must be assembled with high precision and have to pass strict requirements. In this note, an overview of 2S module production is presented, as well as representative examples of problems and experience acquired during module assembly and performance tests.
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High Energy Physics (Phenomenology)
The new LHCb beauty-strange state as the bottom partner of the $D_{s0}^*(2317)$: a LQCD constrained coupled-channel chiral analysis
Miguel Albaladejo, Pablo Encarnación, Albert Feijoo et al. (+1 more)
The LHCb Collaboration has observed a narrow state in the $\bar{B}_s^0\pi^0$ spectrum, about 74 MeV below the $B^-K^+$ threshold, which is the natural candidate for the bottom partner of the $D_{s0}^*(2317)$. Such a state had been predicted as a $\bar{B}K$ bound state by unitarized heavy-
meson chiral perturbation theory with
lattice-QCD input. We analyze the LHCb spectrum with these coupled-channel amplitudes, including isospin breaking through the physical
meson masses, $\pi^0$-$\eta$ mixing, and $m_u\neq m_d$ in the
chiral amplitudes, thereby allowing the $\bar{B}_{s0}^*$ to decay through its only open strong channel, $\bar{B}_s^0\pi^0$. With the parameters fixed by
lattice QCD and no experimental input from the LHCb measurement, the predicted state lies within 1.1-1.7 standard deviations of the observed peak. Adjusting a single parameter, the spectrum is described as well as with the zero-width limit of the LHCb analysis. The new state thus emerges naturally from these amplitudes, with a large $\bar{B}K$ component and an isospin-violating width of tens of keV, and its $J^P=1^+$ heavy-
quark spin partner is predicted with a precision comparable to that of the measured mass.
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All authors Miguel Albaladejo, Pablo Encarnación, Albert Feijoo, Juan M. Nieves
Mathematical Physics
Simon Becker and Izak Oltman
For Bernoulli bond percolation on every regular tree of degree at least three, we prove that infinite clusters appear strictly before absolutely continuous spectrum. Throughout an explicit supercritical interval, the adjacency operator of every open cluster almost surely has no absolutely continuous component. Together with Bordenave's
theorem, this gives $p_c<p_{ac}<1$.
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Strongly Correlated Electrons
Variational Monte Carlo for the Hubbard model
Luca F. Tocchio
In these lecture notes, we introduce the variational Monte Carlo method for the Hubbard model. First, we briefly introduce the single-orbital Hubbard model and its multi-orbital extension, focusing only on electronic models. Then, we introduce the general scheme under which variational Monte Carlo works and we present the variational wave functions that can properly describe superconductive and
magnetic states in single-orbital and multi-orbital Hubbard models. We also detail how to perform Monte Carlo calculations for the given wave functions. We also describe how to optimize a variational wave function with the
stochastic reconfiguration method. Finally, we present a few results for correlation functions that can be computed in variational Monte Carlo, to determine, for instance, the presence of charge or
spin order and superconductivity.
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Quantum Physics
Joscelyn van der Veen and Daniel F. V. James
Pulsed light is represented by density
matrices whose correlation functions have different properties of stationarity and coherence. We show that these density
matrices yield equivalent measurement results after accounting for finite detection times. This in turn reveals a physical meaning to the length of a quantization cavity and explains the origin of the physical spectrum for pulsed light. By generalizing the density
matrices for pulsed Gaussian states of light, we can describe pulsed light of varying statistics in the same basis and relate the photocount rate to the pulse spectrum.
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Quantum Physics
Improved estimate of local Markovianity for quantum Gibbs states
Tai Hsuan Yang
We establish improved locally Markovian properties of
quantum Gibbs states at every fixed positive temperature. For finite-range interactions of bounded interaction degree, the conditional mutual information (CMI) decays exponentially with separation, with a prefactor exponential in the boundary size of only one of the two regions and independent of the size of the other region and the total system. This improves the exponential volume dependence of the local Markov bounds established by Chen and Rouzé \cite{Chen2025}. For exponentially and stretched-exponentially decaying interactions, we obtain stretched-exponential CMI decay with a boundary-dependent prefactor. For power-law interactions, we prove inverse-logarithmic or algebraic decay with
polynomial region-size dependence. Our proof is static, in contrast to the dynamical approach of Chen and Rouzé. We compare the Gibbs state with a product state obtained by removing boundary interactions, reducing the CMI bound to a relative-
entropy loss that we control using locality estimates.
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Superconductivity
Reversible field-free superconducting diode effect controlled by an antiferromagnet
Filip Krizek, Kamil Olejník, Tobias Edwinson et al. (+19 more)
The
semiconductor diode, which allows current to flow preferentially in one direction, is a fundamental building block of numerous modern electronic
circuits. Its superconducting analogue—the superconducting diode effect—enables directional dissipationless current flow and may provide similar functionality in future superconducting
quantum circuits. Realization of such a nonreciprocal supercurrent requires broken time-reversal
symmetry. At zero applied field, this has been typically associated either with intrinsic unconventional superconductivity or extrinsic
spin-split electronic states induced by
magnetic proximity. Here we demonstrate a field-free superconducting diode effect in conventional superconducting Al proximitized by collinear
antiferromagnetic CuMnAs, whose electronic structure breaks time-reversal
symmetry without generating
spin splitting. By tuning the proximity effect through an insulating AlAs interlayer and correlating the reversal of the diode polarity with the reversal of the remanent Néel state, we establish that the antiferromagnet controls the superconducting diode effect. Our results show that neither
spin-split bands nor net magnetization is required for a magnetically controlled field-free superconducting diode effect, extending superconducting nonreciprocity to a broader class of collinear compensated magnets.
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All authors Filip Krizek, Kamil Olejník, Tobias Edwinson, August Jacobi, Athira Suresh, Andrej Farkaš, Jan Kraus, Vít Novák, Christoph Müller, Vojtěch Pařízek, Niclas Heinsdorf, Peter Wadley, Oliver Amin, Kevin Edmonds, Tomas Jungwirth, Libor Šmejkal, Anna Birk Hellenes, Sumit Ghosh, Michal Mazur, Dominik Kriegner, Lucas Casparis, Saulius Vaitiekėnas
Quantum Physics
Rapid Mixing of Parallel Kac's Walk: From Spheres to Stiefel Manifolds
Qian Chen, Minglong Qin, Fang Song et al. (+2 more)
Kac's walk is a classical local random walk whose action on a single real unit vector in dimension $d$ mixes in total variation in $\Theta(d\log d)$ sequential steps~\cite{PS17}. Lu, Qin, Song, Yao, and Zhao introduced a parallel version of Kac's walk that mixes a single
quantum state in $O(\log d)$ rounds~\cite{LQSY+26}. After discretizing the randomness and replacing it by suitable pseudorandom primitives, this parallel walk gives rise to pseudorandom state scramblers, and was subsequently shown to yield pseudorandom
unitaries~\cite{LQSY+25}. We study what happens when the parallel Kac's walk acts simultaneously on $k$ orthonormal
quantum states. We prove that, for any $1\leq k < d$, after $O\!\left((k+\log d)\log(d/\varepsilon)\right)$ steps, the joint distribution of the $k$ output states is $\varepsilon$-close, in both Wasserstein and total variation distance, to that obtained by applying a common Haar-random
unitary to the same inputs. This generalizes the dispersing property of the parallel Kac's walk from a single
quantum state to multiple orthonormal
quantum states. Equivalently, viewing an ordered collection of $k$ orthonormal states as a point on the complex Stiefel
manifold $V_{d,k}=\{X\in\mathbb C^{d\times k}:X^\dagger X=I_k\}$, we show that the parallel Kac's walk mixes rapidly on $V_{d,k}$, with both Wasserstein and total variation mixing times bounded by $O\!\left((k+\log d)\log(d/\varepsilon)\right)$. This extends the Wasserstein mixing result of Pillai, Smith, and Vaikuntanathan for the standard Kac's walk on real Stiefel
manifolds~\cite{PSV26}.
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All authors Qian Chen, Minglong Qin, Fang Song, Penghui Yao, Mingnan Zhao
High Energy Physics (Phenomenology)
Two Feynman integral families for vector boson fusion at NNLO QCD
Linus Götzfried and Andreas von Manteuffel
We consider a planar and a non-planar two-loop Feynman integral family arising in non-factorisable
quantum chromodynamics corrections to
Higgs-
boson production via vector
boson fusion. We construct basis integrals which fulfil canonical differential equations with respect to seven variables for the external kinematics and an internal mass. One of the integral families involves nested square roots. We present strategies for deriving canonical master integrals, $\mathrm{d}\log$ forms and analytic continuation for such cases. Including also families with crossed massless legs, we express the $\varepsilon$-expanded integrals in terms of an algebraically independent function basis. For their evaluation, we employ numerical integration of the differential equations.
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Earth and Planetary Astrophysics
Radiation Hydrodynamics of Self-gravitating Protoplanetary Disks II. Accretion, Migration, Spin, and Internal Structure of GI Fragments
Yang Ni, Hongping Deng and Xue-Ning Bai
In the first paper of this series, we showed that gravitational instability (GI) in protoplanetary disks can produce fragments of planetary rather than brown-
dwarf mass, leaving the subsequent
evolution and ultimate fates of such fragments an open question. Here, we follow every bound object in a global three-dimensional radiation hydrodynamic simulation of a fragmenting $0.196\,M_\odot$ disk around a $1\,M_\odot$
star: seven surviving fragments, one disrupted clump, and one merged clump, followed for $1.2$\,kyr. The fragments form at $1.4$–$3.0\,M_\mathrm{J}$, consistent with the normalized initial-mass distribution of Paper~I. Mass growth follows a single Hill-limited scaling $\propto \Sigma \Omega R_\mathrm{H}^2$, regulated by the delivery of gas into draining feeding zones, while the latest-forming fragments experience supply starvation. Migration is bidirectional and governed by gravitational interactions with both the disk and neighboring clumps.
Accretion supplies most of the fragments'
spin, which aligns with their orbits and provides roughly a tenth of the support against
gravity. The interiors are
entropy-stratified, largely convectively stable, and accumulate mass far faster than they can radiatively cool: compression is quasi-adiabatic, and central
entropies near $12\,k_\mathrm{B}$ per
baryon favor hot-start initial conditions for fragments that evolve into gas
giants. Integrating the measured growth law against the measured gas budget, we predict that the disk produces gas
giants, brown
dwarfs, and a possible low-mass
stellar companion, while one scattered fragment may become a free-floating
planet: the outcome of disk fragmentation is determined not merely at birth, but by the subsequent mass supply and dynamics.
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Fluid Dynamics
Toward Principled Generative Data Assimilation of Turbulent Flows from Sparse Observations
Baris Turan, Zhuoran Liu and Heng Xiao
Turbulent flows are highly chaotic, which makes their instantaneous states difficult to predict. Data assimilation aims to reduce this predictive uncertainty by synthesizing the predictions of a physical solver with partial observations of the system. Traditional data assimilation methods such as ensemble and variational approaches can incur substantial computational cost through evaluations of high-fidelity solvers and, for variational methods, adjoint calculations. Recently, generative
diffusion models have been explored in the solution of inverse problems in fluid mechanics, demonstrating their potential for data assimilation. However, existing
diffusion-based methods often use free parameters instead of the prescribed observation-error covariance to control the balance between the prior and likelihood, departing from the
Bayesian formulation of data assimilation. We propose a framework for principled generative data assimilation in which observations are assimilated in the clean-state space and the prescribed observation-error covariance enters explicitly through an ensemble Kalman update. In the Lorenz-63 system, the proposed method yields a lower trajectory error and equation residual than the other
diffusion-based posterior sampling methods considered, although its ensemble underestimates the posterior uncertainty. In two-dimensional Rayleigh-Bénard convection, the generated fields recover the statistics of the direct numerical simulation reference at large scales, with deviations confined to the smaller scales. These results suggest that the framework can produce physically plausible turbulent flow fields, indicating its potential for more challenging turbulent flow applications.
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Earth and Planetary Astrophysics
Improved Constraints on the Surface of LHS 3844 b from its Mid-Infrared Spectrum
Kimberly Paragas, Heather A. Knutson, Renyu Hu et al. (+4 more)
The thermal emission spectra of terrestrial
exoplanets provide a window into their surface compositions and corresponding geological processes. Close-in, rocky
planets orbiting M
dwarfs are ideal targets for these studies, as observations have shown that most have little to no atmosphere. LHS 3844 b is an ultra-short period super-Earth orbiting a nearby M
dwarf, and is the most favorable target that does not have a dayside magma ocean. We present an updated JWST MIRI/LRS emission spectrum ($5-12$ $\mu$m) of this
planet, derived from eight new and three archival eclipse observations. We combine these visits to obtain the highest SNR emission spectrum for any rocky
exoplanet thus far, with a median SNR of 29 across 12 wavelength bins. Our data are sensitive to the predicted Si-O stretching feature (the strongest mid-infrared silicate feature) for a wide range of common materials and the transparency feature, which is relatively insensitive to composition and constrains the grain size and porosity of surface materials. We find that LHS 3844 b's emission spectrum resembles a blackbody shortward of 10 $\mu$m disfavoring the presence of a transparency feature, and identify a tentative feature ($1.9-3.5\sigma$) between $10-12$ $\mu$m. If this feature is astrophysical and not instrumental in nature, it can be matched by a fayalite (the iron end-member of olivine) surface, but might also be consistent with other candidate
planet-forming materials like spinel or silicon carbide. We discuss possible biases introduced by the wavelength-dependent instrumental ramp, and outline several strategies to mitigate this effect in future observations of LHS 3844~b that would establish the surface composition of this rocky
exoplanet.
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All authors Kimberly Paragas, Heather A. Knutson, Renyu Hu, Bethany L. Ehlmann, Aishwarya R. Iyer, Sebastian Zieba, Laura Kreidberg
Strongly Correlated Electrons
Strong-to-Weak Spontaneous Symmetry Breaking of Dephased Fermions
Abhijat Sarma
Strong-to-weak spontaneous
symmetry breaking (SWSSB) is a novel phase transition in mixed states associated with the loss of global charge information. In this work we study
fermions with $U(1)$
symmetry under infinite density dephasing and derive the SWSSB properties of the resulting mixed states. Our central observation is that at infinite dephasing every Renyi correlator is exactly the
spin-
spin correlator of a compact XY model, whose Boltzmann weight is the squared full-counting-statistics generating function of a classical ensemble built from the parent state. For the Renyi-2 correlator it is the full counting statistics of the parent state itself. We complement the infinite dephasing mapping with a novel diagrammatic expansion for the Renyi-1 correlator, applicable to any diagonal mixed state, which computes the couplings of the Renyi-1 XY model. We also study a replica field theory for even Renyi index quantities, applicable at finite dephasing. Our analysis indicates that fully dephased metals display long-range SWSSB in $d\geq 2$, as confirmed numerically and experimentally in $d=2$, and quasi-long-range SWSSB in $d=1$. For insulating parent states both an SWSSB and a trivial phase are possible at infinite dephasing depending on UV details. Long-range SWSSB in $d\geq 3$, or quasi-long-range SWSSB in $d=2$, survives above a nonuniversal, Renyi-index-dependent threshold and is lost when the parent state is deep in the insulating phase, with the exception of
quantum Hall insulators which generically have quasi-long-range SWSSB. For even Renyi indices we also determine the stability of the SWSSB phase away from infinite dephasing and derive the universality class of the SWSSB transition.
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General Relativity and Quantum Cosmology
Orbital stability, relativistic precession, and QPO constraints for constant-curvature black holes in $f(R)$ gravity
Kourosh Nozari, Sara Saghafi, Khadijeh Salahshour et al. (+1 more)
We analyze circular-orbit stability, epicyclic resonances, relativistic precession, and quasi-periodic-oscillation (QPO) constraints in the constant-
curvature vacuum sector of metric $f(R)$
gravity. The Schwarzschild–(anti-)de~Sitter and Kerr–(anti-)de~Sitter backgrounds are characterized by
curvature $R_0$ satisfying the algebraic trace equation. We derive stationary-coordinate-time orbital and epicyclic frequencies and determine stable timelike circular-orbit domains. Positive
curvature confines stable motion between innermost and outermost stable circular orbits, which merge at a critical
curvature, and permits two resonance radii for suitable frequency ratios. Negative
curvature allows stable motion to arbitrarily large radii, with $\Omega_\theta/\Omega_r\rightarrow1/2$, compared with unity in the asymptotically flat limit. We determine the $3{:}2$, $2{:}1$, and $3{:}1$ resonance branches and signed nodal precession, recovering the Lense–Thirring limit. We also evaluate angular-momentum-weighted rigid-flow precession and viscous
alignment, with the outermost stable orbit bounding positive-
curvature flows. A
Bayesian Markov chain Monte Carlo analysis combining the simultaneous GRO J1655–40 QPO triplet with an independent dynamical-mass measurement yields $R_0M^2=-5.57^{+12.94}_{-16.15}\times10^{-4}$ at $68\%$ credibility, conditional on the geodesic relativistic-precession prescription and adopted time normalization. Kerr remains allowed, with negligible fit improvement from nonzero
curvature. Doubling the mass uncertainty broadens the
curvature interval by approximately $2.1$; removing the mass likelihood reveals an extended, prior-dependent degeneracy. This is therefore a joint QPO and dynamical-mass constraint, with no significant evidence for departure from Kerr.
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All authors Kourosh Nozari, Sara Saghafi, Khadijeh Salahshour, Moisés Bravo-Gaete
Earth and Planetary Astrophysics
Constraining exoplanet population parameters with Kepler and simulation-based inference
Chloé Padois, Friedrich Anders and Daniel del Ser
In the context of the rapidly growing field of
galactic exoplanet population studies, we present an
exoplanet simulator capable of generating synthetic populations for millions of
stars in a few seconds (Padois et al., 2025). Our framework combines observed
exoplanet detections with the latest planetary formation models, incorporating dependencies between host
star properties and
planet occurrence rates, orbital period distributions, and other key demographic features. However, many model parameters remain uncertain and model-dependent. To constrain some of the most critical ones, we couple our simulator with simulation-based inference (SBI): we define a set of 44 free parameters describing the population of different
planet types (occurrence rates, mass-period distribution, mass-radius relation, etc.), run millions of simulations sampling from broad prior distributions, simulate their detectability by Kepler, and train a machine-learning
algorithm to learn the relationships between input parameters and the resulting "observed" synthetic populations. The best-fit parameters are then inferred by comparing model outputs to real observations, for which we adopt the Kepler confirmed
planet catalogue as our reference
dataset, since it provides the largest homogeneous sample from a single facility. We present preliminary results for the
planet occurrence rate as a function of
stellar mass and
metallicity, across different
planet types, along with constraints on several key simulation parameters such as the orbital period distribution and the inclination dispersion within planetary systems. These refined parameters enable us to refine our yield predictions for upcoming
exoplanet detection missions, including PLATO, Roman, and HAYDN.
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Physics and Society
Multiscale Reconstruction of Weighted Networks from Coarse-Grained Data
Mattia Marzi, Frank P. Pijpers and Diego Garlaschelli
Network reconstruction from partial information is usually performed at the same resolution level at which constraints are observable. This becomes problematic when only coarse-grained information is available, while the relevant process occurs at a finer scale. Here we employ the multiscale model of weighted networks introduced in a companion paper and turn it into a probabilistic framework for reconstructing weighted networks across arbitrary aggregation levels. The model is built to preserve its functional form under coarse-graining, so that global parameters calibrated on an observable aggregate layer can be transferred to finer layers without refitting. We test the method on two empirical systems with different aggregation mechanisms. In the International Trade Network, countries are aggregated into geographic macro-regions and the observed coarse-grained layer is used to infer the underlying country-level network. In the Dutch production network, sectoral flows are reconstructed across the hierarchical industrial classification, using coarser sectoral layers to infer finer ones. In both geographical and sectoral settings, we
benchmark our genuinely multiscale reconstruction method against a state-of-the-art weighted reconstruction model calibrated directly at the target resolution, and therefore using additional information available at the same (finer) scale at which performance is evaluated. Remarkably, despite this informational disadvantage, our method recovers the fine-scale binary structure with high accuracy, improving precision, specificity, accuracy and maximum degree-error diagnostics, while remaining nearly equivalent in sensitivity.
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