Statistical Mechanics · Cross-listed from q-bio.PE
Spatial spread of infection: transitions between pulled and pushed fronts
Evgeniy Khain and Rohan Sukumar
We consider the spatial spread of epidemic into an unstable, healthy state. When the transmission rate depends on the fraction of infected, the propagating pulse of infection can be either a pulled front or a pushed front. We determined the phase space of parameters for the pulled and pushed regions both by numerically solving the spatial SIR partial differential equations and by a theoretical analysis of the front propagation phenomenon. We found both a continuous and a discontinuous transition between the pulled and pushed front solutions; in the latter transition, the front speed undergoes a jump as a certain parameter crosses the critical threshold. The behavior of the propagating pulses near the transitions has been analyzed and a good agreement between the theory and numerics has been observed. Finally, a bistable region where both pushed and pulled propagating pulses can be realized has been discovered.
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Quantum Physics
Can PCE solve the factorisation problem via optimisation?
Fernando Alonso, Colomán Samprón, Jacobo Veiga et al. (+1 more)
The ongoing progress in
quantum technologies has fueled a sustained exploration of their potential applications across various domains, particularly in computational problems that are considered intractable for classical systems. Among these problems, integer factorisation remains of special interest due to its relevance to widely used cryptographic schemes such as RSA. Among the different possibilities, one approach to factorisation is to convert the problem into a binary optimisation problem. However, current proposals usually need a large number of
qubits that make them unfeasible within the current hardware. In this work, we investigate a possible adaptation of the Pauli Correlation Encoding (PCE)
algorithm to the factorisation problem. Due to its compression capability, it can drastically reduce the number of needed
qubits. The proposed approach explores how the structure and dynamics of the PCE framework may be employed to encode and analyze candidate factor relations within a
quantum computational setting. Rather than presenting a replacement for established
quantum factorisation methods, this study aims to provide a preliminary examination of the feasibility and limitations of the proposed adaptation. We discuss the algorithmic design, its conceptual relationship with existing
quantum approaches, and the practical constraints associated with implementation on current or near-term
quantum hardware. Initial observations suggest that the method may offer an alternative perspective for studying factorisation within the broader context of
quantum computation, although no claim is made regarding computational advantage. These results are intended primarily as an exploratory contribution to ongoing research in
quantum algorithms and computational number theory.
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All authors Fernando Alonso, Colomán Samprón, Jacobo Veiga, Andrés Gómez
Geophysics
Post-FWI Injection of Learned Priors Using a Flow Matching Model
Hao Zhang and Tariq Alkhalifah
Full Waveform Inversion (FWI) is a powerful tool for subsurface velocity reconstruction but remains highly ill-posed, sensitive to acquisition limitations, often requiring some form of regularization to reduce artifacts and enhance resolution. While recent developments have shown that generative models can inject learned priors directly into the FWI optimization process, such approaches typically require additional, computationally expensive inversion iterations. In this study, we propose a post-FWI refinement strategy based on a Flow Matching (FM) generative model, which leverages learned geological priors without re-running FWI. The method guides the deterministic generative process using the FWI result, as well as well logs, if available. Synthetic and field data experiments demonstrate that we can inject well information and our geological expectations (prior) into the provided FWI result, and thus, we can effectively enhance its resolution and geological quality. In fact, the well prior even managed to alter the model depth to fit the well information, which is a form of correcting for depth misties.
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General Relativity and Quantum Cosmology
Wormhole Geometries in Extended Symmetric Teleparallel Gravity with $f(Q, T) = \alpha Q + \beta T + \gamma T^2$
Sara Rastgoo and Foad Parsaei
In this study, we study static and spherically-symmetric wormhole configurations within the recently proposed class of extended symmetric teleparallel gravities characterised by the functional form $f(Q,T)=\alpha Q+\beta T+\gamma T^{2}$, where $Q$ is the non-metricity scalar, $T$ is the trace of the energy-momentum tensor, and ($\alpha,\beta,\gamma$) are constant coupling parameters. By varying the action with respect to the metric, we derive the modified field equations and cast them in an effective Einstein-like form containing additional
geometric contributions that depend on $Q$ and $T$. We conclude that the $f(Q,T)=\alpha Q+\beta T+\gamma T^{2}$ framework offers a viable arena for constructing physically realistic wormholes without invoking severe energy condition violations, opening new pathways for connecting modified
gravity phenomenology with astrophysical signatures of non-trivial spacetime
topologies.
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Materials Science
Elemental Germanium Phase-Change Memory
Till Zellweger, Marko Mladenović, Kevin Portner et al. (+7 more)
Phase-change
memory (PCM) is a mature technology for fast, scalable, non-volatile data storage, with applications spanning embedded
memory, as well as in-
memory and neuromorphic computing. PCM predominantly relies on chalcogenide
alloys, with $\mathrm{Ge_2Sb_2Te_5}$ (GST) as the industry standard. Yet in these
alloys, the individual Ge, Sb, and Te atoms redistribute upon cycling, causing
stochastic operation and ultimately device failure. To address this issue, elemental antimony was proposed as a PCM material, but it exhibits a metastable amorphous state that prevents reliable data retention. Moreover, tellurium and antimony can contaminate complementary metal-
oxide-
semiconductor (CMOS) production lines or act as unintended dopants, restricting manufacturing of PCM to dedicated fabs. Here we introduce elemental germanium (Ge) as a CMOS-native phase-change material that overcomes these fundamental limitations. In a vertical PCM
cell architecture, Ge enables sub-nanosecond crystallization (240 ps, 40 times faster than GST), non-volatile data storage with excellent thermal stability ($>$110 {\deg}C for 10 years vs. $\sim$87 {\deg}C for GST), and a resistance drift coefficient approximately 60% lower than in GST. These results establish pure Ge, a standard
semiconductor, as an alternative to chalcogenide phase-change materials, achieving superior performance in key metrics and enabling phase-change
memory to be fabricated in standard
semiconductor facilities.
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All authors Till Zellweger, Marko Mladenović, Kevin Portner, Christoph Weilenmann, Michael Stiefel, Hanglin He, Klemens Bauer, Luiz Felipe Aguinsky, Mathieu Luisier, Alexandros Emboras
Optics
Nonreciprocal subdiffraction imaging with staggered gyromagnetic photonic crystals
Rui Ding, Tianshu Zhang, Jiarui Yu et al. (+4 more)
Subdiffraction imaging serves as a novel technique to enhance the optical imaging resolution, where a backscattering-free approach remains so far unavailable. Here, we theoretically predict and experimentally demonstrate that the gyromagnetic photonic
crystals applied with staggered
magnetic fields support nonreciprocal light propagation beyond the diffraction limit. Broadband subdiffraction imaging was experimentally observed to span the frequency window traversing a pair of spectrally separated Dirac points, where near-flat equi-frequency contours (EFCs) emerged while experiencing an enforced shape transition. Our findings establish a practical paradigm for constructing backscattering-immune super-resolution imaging systems based on topological photonic
crystal platforms.
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All authors Rui Ding, Tianshu Zhang, Jiarui Yu, Namitha Nandakumar, Quanlong Yang, Mudi Wang, D.Y. Wang
Mathematical Physics · Cross-listed from math.AP
Continuous Data Assimilation for the 2D Navier-Stokes Equations from Partial Tangential Boundary Observations
Gianmarco Del Sarto and Buddhika Priyasad
We study continuous data assimilation for the two-dimensional Navier–Stokes equations on a smooth, bounded, connected domain with Navier-slip boundary conditions, using no interior observations. The available data consist only of finite-dimensional measurements of the tangential velocity on a non-empty relatively open subset $\Gamma\subset\partial\Omega$. We prove that sufficiently strong boundary feedback, constructed from sufficiently fine observations, generates a coercive spectral gap for the assimilation error. The limiting gap is identified with that of a mixed-boundary problem obtained by imposing a homogeneous Dirichlet condition on $\Gamma$, and is shown to be of order $\nu$. Combining this feedback-induced coercivity with an estimate of the non-linear error production in terms of the long-time averaged symmetric-gradient energy of the reference solution, we obtain a sufficient criterion for exponential synchronisation. We verify this criterion in the unforced case, for sufficiently small forcing when the unnudged Navier-slip form has an $\mathrm{L}^2$ spectral gap, for sufficiently large viscosity on domains without tangential rigid motions, and for sufficiently large viscosity in the presence of positive boundary friction. We also treat perfect slip on domains admitting tangential rigid motions, where synchronisation follows under a smallness condition on the non-rigid solenoidal component of the forcing.
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Physics and Society
Social learning drives underprioritization of collective challenges
Russ Yoon and Vicky Chuqiao Yang
Societies often struggle to prioritize important challenges in a timely manner, with substantial costs from delayed action on issues like
climate change and pandemic mitigation. A persistent puzzle is that broad concern on issues often fails to translate into collective priority. We argue that a key driver lies in how concern is formed across competing issue domains. Some issues depend heavily on social learning, where individuals infer importance from others, often because direct experience is limited. Others depend more on individual learning from firsthand experience. We develop a dynamic model in which two subgroups form issue-specific concerns through individual and social learning, and these concerns are aggregated into collective priority. The model yields three insights. First, with two issues of equal objective severity, the one that depends more on social learning tends to be underprioritized when both issues are severe. Second, gradual increases in severity delay reprioritization of the issue, with the delay growing as reliance on social learning increases. Third, this bias can be reduced by reducing social learning or by increasing intergroup learning beyond a critical threshold. These results offer a general mechanism for why severe problems can remain neglected in collective action despite widespread concern, and why intergroup interaction or experiential simulations may help align collective priorities with objective risks.
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Biological Physics
Plasma-activated water and phenolic compounds: A potent combined strategy against yeast resilience
Bernard Gitura Kimani, Ramin Mehrabifard, Oleksandr Galmiz et al. (+1 more)
Effective fungal control is essential to prevent spoilage, contamination, and infections in food, healthcare, and industrial environments. This study explores the antifungal activity of
plasma-activated water (PAW), generated by transient spark (TS) electrical discharge, combined with natural phenolic bioactive compounds against the planktonic growth, biofilm formation, and surface adhesion of the yeasts Saccharomyces cerevisiae and Wickerhamomyces anomalus. The phenolic compounds were tested at concentrations of 1 or 2 mg/mL for planktonic growth after determining their minimum inhibitory concentrations. Biofilms were grown on sterile microscope slides for 48 h, stained with acridine orange or calcofluor, and examined using fluorescence microscopy. PAW was used immediately after the
plasma treatment of tap water to prepare PAW-phenolic solutions. The combinations of PAW with cinnamic acid and vanillin demonstrated the strongest antiyeast activity against planktonic growth, biofilm formation, and surface adhesion. Biofilms exposed to the PAW-phenolic combinations were notably fragmented, and the residual
cells exhibited structural damage. Complete inhibition of biofilm formation was observed when 500 microg/mL cinnamic acid was combined with PAW. These findings demonstrate the potential of combining PAW with selected phenolic compounds as an effective and sustainable strategy for controlling fungal growth.
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All authors Bernard Gitura Kimani, Ramin Mehrabifard, Oleksandr Galmiz, Zdenko Machala
Strongly Correlated Electrons
Differentiable Inverse Design of Two-Body Interactions for the Moore-Read State
Yi Yang, Xin Wan and Zi-Xiang Hu
Designing interactions that stabilize target
quantum states is a central challenge in strongly correlated physics. For fractional
quantum Hall states, identifying suitable two-body interactions remains difficult even when a target wave function is known. Here we implement a differentiable inverse-design approach that combines automatic differentiation with exact diagonalization to optimize two-body interactions, using the Moore–Read Pfaffian state as a
benchmark. The optimized ground states achieve overlaps exceeding 99% with the target for systems containing up to 12 electrons. Excitation and
entanglement spectra provide complementary finite-size diagnostics. A common exponential pseudopotential profile retains an overlap of 91.1% at 14 electrons without further optimization, supporting its transferability beyond the optimization sizes. These results demonstrate the approach on a non-Abelian
quantum Hall benchmark and motivate its application to other numerically accessible trial states for which suitable approximate parent
Hamiltonians remain unknown.
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High Energy Physics (Phenomenology)
T-odd transverse momentum dependent gluon distributions for tensor polarized deuteron in a spectator model
Xiupeng Xie and Zhun Lu
We present a model calculation of the T-odd transverse momentum dependent distribution functions (TMDs) for
gluons inside a tensor polarized deuteron. The model is built on the assumption that an on-shell deuteron can emit a time-like off-shell
gluon, with the residual system treated as a single on-shell spectator particle. The spectator mass is described via a spectral function, which allows it to take real values over a continuous range. The final-state interaction required to generate nonvanishing T-odd functions are implemented via single-
gluon exchange between the spectator and the outgoing parton. We derive analytical expressions for six T-odd
gluon TMDs, and present numerical results characterizing their dependence on the longitudinal momentum fraction $x$ and the transverse momentum $\bm{k}_T$.
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High Energy Astrophysical Phenomena
Dust Without Na I D Trace: The Case of Highly Attenuated Type Ib SN 2024vjc
Javier Silva-Farfán, Keiichi Maeda, Andrea Pastorello et al. (+19 more)
Understanding
dust attenuation toward extragalactic transients is critical for recovering their intrinsic properties and probing the local environments of distant
galaxies. A popular diagnostic is the Na I D absorption equivalent width widely applied to extragalactic transients. In this paper, we present early-time optical and near-infrared observations of the Type Ib
supernova (SN) SN 2024vjc, followed for $\sim$130 days post-explosion. SN~2024vjc exhibits only weak Na~I~D absorption, indicating only a modest host attenuation with $E (B-V)_{\rm host} \sim 0.18$ mag; if this argument were applied, SN~2024vjc would be a peculiar, faint, and red SN Ib while showing the light-curve shape and spectral
evolution broadly consistent with those of canonical SNe Ib. We show that this is not the case; SN-based diagnostics (intrinsic color templates, color-curve
evolution, and spectral dereddening) together with the Balmer decrement indicate substantial attenuation, $E(B-V) \sim 0.45$ $-$ $0.8$\,mag. The weak Na I D absorption may result from photoionization of neutral sodium by the intense radiation field of a young H$_{2}$ region at the explosion site; this scenario is directly supported by the detection of narrow H$_{\alpha}$, [N$_{2}$], and H$_{\beta}$ emission lines and a blue continuum excess in late-time spectroscopy. SN~2024vjc represents a clear counterexample to the commonly assumption that weak or absent Na I D absorption implies negligible host-
galaxy attenuation, and highlights the importance of employing multiple, independent attenuation diagnostics.
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All authors Javier Silva-Farfán, Keiichi Maeda, Andrea Pastorello, Hanindyo Kuncarayakti, Takashi Nagao, Giorgio Valerin, Andrea Reguitti, Dino Pierluigi Fugazza, Giuliano Pignata, Jesper Sollerman, Chris Ashall, Tomás E. Müller-Bravo, Joseph P. Anderson, Claudia P. Gutiérrez, Priscila J. Pessi, Erkki Kankare, Niko Pyykkinen, Mariusz Gromadzki, Ting-Wan Chen, Thomas M. Reynolds, Irene Salmaso, Avishay Gal-Yam
Quantum Physics
Fixed points in de Finetti hierarchies
Gereon Kossmann and Julius A. Zeiss
De Finetti
theorems convert permutation
symmetry into approximate mixtures of product states and thereby justify a wide range of reductions in classical and
quantum statistics. In this work we study de Finetti hierarchies in which the feasible states are additionally constrained to be fixed points of
quantum channels, a condition that subsumes invariance under arbitrary compact
symmetry groups. Combining the mean-ergodic
theorem with the structure theory of conditional expectations, we prove a tight bound on the
entanglement-assisted classical capacity of the dual of a conditional expectation, block-wise distortion bounds for informationally complete measurements adapted to fixed point
algebras, and an exact type-based refinement of the chain rule for permutation-invariant states. From these tools we derive several de Finetti
theorems: a double-sided extension
theorem with $O\left(\sqrt{\log n}/n\right)$ convergence, an interpolation
theorem whose dimension dependence is governed solely by the block structure of the fixed point
algebras and which recovers the dimension-independent classical behavior for maximal
tori, and a Bose-symmetric variant. Exploiting Schur-Weyl duality and Gelfand-Tsetlin bases, we further show that the rounding scheme producing certifiably good separable inner approximations for (constrained) separability problems can be implemented in time
polynomial in $1/\epsilon$ for fixed local dimensions, complementing the known efficient outer hierarchies. Applications to bilinear optimization under
symmetries and to approximate
quantum error correction are discussed.
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Applied Physics
Variable Emissivity Modeling for Sustainable Lunar Surface Habitats
S. Keller, S. Stewart, S. Taylor et al. (+1 more)
Lunar habitats will be one of the first platforms to enable long-term human presence beyond Low Earth Orbit. These structures act as a stepping stone for exploring our
solar system while simultaneously enabling lunar resource utilization, low-energy cryopreservation, and various other applications. These habitats must be designed to withstand the extreme thermal variation of the lunar surface caused by the changing orientation with respect to the Sun and Earth. White paints and multi-layered insulation are conventionally used to minimize
solar heating, yet this approach is static and results in a structure that requires internal heating to survive lunar night. An adaptive approach to control absorbed and emitted radiation allows for highly efficient daytime cooling and improved nighttime heat retention. Louvers and shutters have been employed to switch between high- and low-emissivity states; however, this approach relies on ensuring moving parts are resilient to
dust contamination. Alternatively, variable emissivity materials are a solid-state solution with no moving parts. The emissivity of these materials can be switched passively based on surface temperature, or actively as a result of applied voltage. Despite their potential to reduce power consumption and increase thermal stability, variable emissivity materials have yet to be explored on the lunar surface. We first present a finite element modeling approach to predict the thermal performance of simplified habitats in realistic lunar environments. We then demonstrate the benefit of variable emissivity materials for thermal stability and lunar night survival by comparing them to traditional constant emissivity coatings. By using variable emissivity materials, we envision near-constant temperature lunar habitats with significantly reduced internal heating requirements.
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All authors S. Keller, S. Stewart, S. Taylor, O. Ilic
Quantum Physics
Qutrit-Based Neural Quantum Kernels for Classification Tasks
Camila Cristiano-Romero, Pablo Rodriguez-Grasa and Mikel Sanz
Neural
quantum kernels (NQKs) construct
quantum kernels by pretraining a
quantum neural network (QNN) and subsequently reusing the trained
circuit as a task-adapted
embedding. Extending this framework to qudits, with local
unitaries in $\mathrm{SU}(d)$, provides a natural route to richer data
embeddings through the increased local degrees of freedom and a direct interface for multiclass classification via intrinsically multi-level
quantum systems. In this work, focusing on qutrits ($d=3$), we extend NQKs to the qudit setting and perform a systematic study of key design choices, including the number of encoded features, the number of qutrits, the kernel construction (1-to-$n$ and $n$-to-$n$), and the parameterization of $\mathrm{SU}(3)$
unitaries. Across binary and three-class tasks on four
benchmark datasets, qutrit NQKs improve over the corresponding QNN baselines in nearly all settings considered and can benefit from scaling both the feature budget and the system size, although the magnitude of these gains may saturate, is
dataset-dependent, and depends on the chosen parameterization. In particular, an ablation over $\mathrm{SU}(3)$ parameterizations shows that the
unitary representation can substantially impact both optimization behaviour and classifier performance. These findings highlight the potential of qudit-based
quantum models not only as a straightforward generalization of
qubit-based architectures, but also as a promising means to better exploit complex data structures in
quantum machine learning.
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Quantum Physics
Mitigation of Measurement-Induced State Transitions via a Fast-Load and Fast-Clear Readout
Wei-En Lin, Li-Chieh Hsiao, Chen-Hsun Ma et al. (+8 more)
High-fidelity and rapid
qubit readout is essential for superconducting
quantum processors, typically realized through the
quantum non-demolition (QND) dispersive interaction within a
qubit-resonator architecture. However, the achievable readout speed and fidelity are fundamentally limited by measurement-induced state transitions (MIST). For a transmon
qubit, MIST is highly sensitive to the offset charge $n_g$ due to the charge dispersion of its higher-lying energy levels. In this work, we systematically investigate $n_g$-dependent MIST dynamics governed by the diabaticity and
symmetry of pulse shaping within a charge-sensitive transmon architecture. We engineer fast-load and fast-clear pulses that effectively suppress resonator
photon overshoots, thereby demonstrating a highly practical strategy to mitigate MIST without requiring complex waveforms or real-time feedback. Utilizing active gate-voltage control and rapid feedback, the measurement-induced transition probability is precisely mapped against $n_g$ and the steady-state resonator
photon number, exhibiting strong agreement with numerical Floquet branch analysis. Ultimately, we evaluate the $n_g$-averaged total error probabilities for both readout and post-readout stages, verifying that a straightforward three-step pulse scheme consistently minimizes overall readout errors. Within the framework of large-scale superconducting
quantum processors, this practical, hardware-free approach inherently offers a better trade-off between the readout signal-to-noise ratio and QND preservation.
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All authors Wei-En Lin, Li-Chieh Hsiao, Chen-Hsun Ma, Erh-Hsiang Yeh, Wei-Lun Peng, Hsi-Sheng Goan, Cen-Shawn Wu, Yueh-Nan Chen, Yung-Fu Chen, Chung-Ting Ke, Chii-Dong Chen
Computational Physics
Tunable mesoscopic numerical model for bacterial biofilms
J. Martin-Roca, B. Wu-Zhang, J. Oller et al. (+2 more)
We present a tunable mesoscale model to provide a basis for future rheological calculations of of bacterial biofilms, explicitly incorporating reversible crosslinking within the extracellular polymeric substance (EPS)
matrix. Using a Dissipative Particle Dynamics framework combined with a Gillespie-inspired
algorithm, bonds between
polymers and bacteria dynamically form and break, capturing the intrinsically evolving nature of the network. We show that biofilm structure is governed by a competition between
polymer-
polymer and
polymer-bacteria crosslinks, controlled by binding energy, linker availability, and bond stiffness and provide a minimal model that helps to understand the competition between both species.
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All authors J. Martin-Roca, B. Wu-Zhang, J. Oller, J. Ramirez, C. Valeriani
Fluid Dynamics · Cross-listed from math.NA
No Free Lunch in Flow Surrogates under Time-Varying Boundary Conditions: A Two-Regime Study
Georg Winkler and Martin Stoll
We test whether an architecture that succeeds on a simple flow regime also succeeds on a richer one, with each trained separately on each regime. We explore two transient flows under time-varying boundary conditions: the three-dimensional slurry film in chemical-mechanical planarisation (CMP), central to
semiconductor manufacturing, and the two-dimensional Kármán
vortex street (KVS). Eight surrogate models on one shared pipeline differ in whether they learn the full field or a latent representation, and in whether they predict in one shot or step by step. No single architecture wins both regimes. On the film, a one-shot full-field model reconstructs the cumulative wall shear stress to 2.7% relative error. On the wake, a latent autoregressive DeepONet retains 90% of the shedding power that direct and one-shot models damp to almost zero. The treatment of time decides the outcome. The self-sustained wake calls for autoregressive feedback and the boundary-driven film for a direct map. Pointwise RMSE hides the damped oscillation on the wake, compresses the sixfold lead on the film's process target, and picks the damped model under wake extrapolation. The evaluation scores five physical questions. Trained surrogates answer queries 10^3 to 10^4 times faster than the finite-element solver and pay off from the first query beyond the training set on the film and from the third on the wake. Neither the winning architecture nor its validation holds across regimes. The choice of surrogate should follow the dynamical character of the target flow, and its validation should resolve the failure modes.
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General Relativity and Quantum Cosmology
Upper bounds on the force function in spatially regular self-gravitating matter configurations
Shahar Hod
We use the non-linearly coupled Einstein-matter field equations to prove four
theorems that bound from above the dimensionless force function ${\cal F}=4\pi r^2\cdot p(r)$ in spatially regular curved spacetimes of spherically symmetric self-gravitating matter configurations [here $p(r)$ is the radially-dependent pressure inside the spatially regular matter configurations]. In particular, for generic (not necessarily isotropic) matter configurations it is proved that: (i) ${\cal F}\leq 2$ for matter fields that satisfy the dominant energy condition, and (ii) ${\cal F}\leq 1$ for matter fields with a non-positive energy-momentum trace. In addition, for self-gravitating isotropic matter configurations we derive the stronger upper bounds: (iii) ${\cal F}\leq 1$ for matter fields that satisfy the dominant energy condition, and (iv) ${\cal F}\leq 1/2$ for matter fields with a non-positive energy-momentum trace. Our analytically derived results are in accord with the spirit of the maximum force
conjecture in general relativity.
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High Energy Physics (Theory)
Stability and Chaotic Dynamics in a Nonlinearly Confined ghost-sector Hamiltonian
Zahra Molaee and Soleyman Fatholahzadeh
We investigate the nonlinear dynamics of a
Hamiltonian system containing a ghost degree of freedom coupled to a canonical sector through nonlinear interactions. The model consists of one positive-energy and one negative-energy mode, augmented by quartic and sextic nonlinearities that regularize the large-amplitude behavior of the system. Unlike conventional ghost models, which typically exhibit runaway trajectories due to the indefinite nature of the kinetic energy, the present
Hamiltonian possesses a confining nonlinear structure that renders the accessible energy surfaces compact for finite total energy. We derive the equations of motion and analyze the
geometric properties of the
Hamiltonian flow. Particular
attention is devoted to the interplay between local ghost-induced instability and global nonlinear confinement. We show that the sextic contribution dominates the asymptotic dynamics and prevents escape to infinity despite the presence of a negative-energy sector. As a consequence, the model provides a controlled framework for studying bounded dynamics in ghost-coupled systems. The phase-space structure is investigated through numerical integration, Poincaré surfaces of section, and Lyapunov analysis. Depending on the interaction strength and nonlinear couplings, the system exhibits a transition from regular quasi-periodic motion to chaotic dynamics characterized by positive maximal Lyapunov exponents. Remarkably, chaotic trajectories remain confined within compact regions of phase space, yielding a realization of bounded chaotic motion in a ghost-containing
Hamiltonian system. These results provide a concrete example of how nonlinear self-interactions can regularize ghost dynamics at the classical level and indicate a useful prototype for studying stability, confinement, and chaos in nonstandard
Hamiltonian theories.
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Astrophysics of Galaxies
Jeans criterion in hydrostatic stratified media
Mahmood Roshan and Asiyeh Habibi
The classical Jeans stability criterion neglects spatial gradients in background physical quantities such as density and pressure. Here, we revisit the Jeans analysis for a non-rotating fluid in hydrostatic
equilibrium, explicitly accounting for these gradients and deriving a modified dispersion relation governing perturbation propagation. Using physical arguments, we show why the Jeans swindle is not required to derive the Jeans criterion for perturbations that are small compared to the size of the host system. We use linear perturbation analysis alongside an averaging procedure to study the behavior of the local Eulerian perturbations in a hydrostatic medium, showing that background gradients enter the dispersion relation in a highly non-trivial manner, precluding the derivation of a general gravitational stability criterion applicable to an arbitrary hydrostatic system. We demonstrate that, in the local short-wavelength limit, the standard Jeans criterion remains valid despite the presence of nonzero background gradients, and that all local perturbations in a hydrostatic system are stable against local gravitational collapse. We conclude that it is not possible to derive a general local gravitational stability criterion valid for an arbitrary hydrostatic background; however, in the local short-wavelength limit, the standard Jeans criterion remains valid.
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Strongly Correlated Electrons
Pair-Density Wave from Doping an Altermagnetic Mott Insulator
Shuai A. Chen, Qianqian Chen, Guangyu Yu et al. (+1 more)
Pair-density-wave (PDW) superconductivity is a state in which the superconducting order parameter modulates at a finite wavevector. Using large-scale density
matrix renormalization group, we study the doped altermagnetic Mott
insulator in the checkerboard $t$-$J$ model, where altermagnetic exchange anisotropy is encoded microscopically through anisotropic
ferromagnetic next-nearest-neighbor exchange. By mapping the ground-state phase diagram as a function of doping and altermagnetic anisotropy, mainly on six-leg cylinders, we identify a transition from a uniform $d$-wave superconducting regime with charge modulation to a PDW regime coexisting with stripe order. In the PDW regime, we report an unconventional wave-vector locking $\mathbf Q_{\mathrm{PDW}}\approx 2\mathbf Q_{\mathrm{Stripe}}$ along the cylinder direction, in contrast to the conventional relation. Pair correlations reveal a two-scale structure, consisting of short-distance local $d$-wave pairing and long-distance finite-momentum PDW correlations. A
symmetry-based Ginzburg–Landau analysis is presented for the observed locking. Our results identify altermagnetism as a strong-coupling, microscopically grounded route to finite-momentum superconductivity in doped Mott
insulators.
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All authors Shuai A. Chen, Qianqian Chen, Guangyu Yu, Zheng Zhu
Optics
Carrier-Envelope Phase Control of Orbital Angular Momentum in Solid-State High-Harmonic Generation
Camilo Granados, Rajaram Shrestha, Bikash Kumar Das et al. (+5 more)
High-order harmonic generation (HHG) driven by optical
vortices is a powerful route to produce structured light in different spectral regions. The nonlinear process transfers orbital angular momentum (OAM) from the driving field to the emitted harmonics according to the scaling law $l_q = q\times l$, a consequence of the rotational invariance and angular momentum conservation. Here, we show that, in the regime of few-cycle pulses, the topological charge (TC) of the harmonic radiation detected within a finite spectral window is no longer fixed by this scaling law alone, but is governed by the interplay between broken
crystal inversion
symmetry and carrier-envelope phase (CEP)-sensitive sub-cycle electron dynamics. By driving HHG in a ZnO
crystal with few-cycle ($\approx 1.5$ cycles)
vortex beams centered at 3.2~$\mu$m, we observed that the measured TC becomes strongly CEP-dependent, switching between adjacent integer values, but only when the inversion
symmetry is broken and the harmonic emission is CEP-sensitive. The TC switching vanishes when either condition is removed. Numerical analysis reveals that the TC switching originates from a CEP-controlled redistribution of spectral weight among spectrally overlapping harmonic orders, which changes the dominant OAM channel within the detection window. These results identify the CEP as a degree of freedom for tailoring the topological structure of high-harmonic radiation, pointing toward waveform-controlled structured attosecond light sources.
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All authors Camilo Granados, Rajaram Shrestha, Bikash Kumar Das, Debobrata Rajak, Eric Cormier, Bálint Kiss, Carmelo Rosales-Guzman, Wenlong Gao
Instrumentation and Methods for Astrophysics
Breakthrough Listen's Automated Commensal Technosignature Survey with MeerKAT
Daniel J. Czech, David H.E. MacMahon, Ian Heywood et al. (+20 more)
The search for extraterrestrial intelligence (SETI) is an ongoing effort to detect technosignatures, evidence of technologically capable life beyond Earth. Conducting a comprehensive SETI programme requires a large amount of
telescope time, which must be balanced with the science goals of a given observatory. Fortunately, many modern
radio telescopes offer commensal access to the data they produce, allowing multiple scientific programmes to operate in parallel. The MeerKAT
radio telescope in South Africa provides commensal access to a range of components, from each
antenna's digitiser to the main channeliser (F-engine), via multicast Ethernet groups. Here, we describe the Breakthrough Listen user-supplied equipment (BLUSE) system at MeerKAT, which leverages multicast Ethernet to conduct an autonomous commensal technosignature survey, processing the full available bandwidth from all
antennas. Its primary mode of operation is to upchannelise the incoming F-engine data to ~1Hz resolution, synthesize coherent beams on objects of interest, and search the resultant data for technosignatures. Since 2022, BLUSE has autonomously processed data from coherent beams synthesized on more than 1.2 million individual pointings, including repeat visits. BLUSE demonstrates how commensal technosignature surveys on
radio telescope arrays offer a rapid and cost-effective way to increase the rate at which technosignature surveys can be conducted. This article describes the architecture of BLUSE, provides experimental evidence validating its features and performance, and quantifies its observing progress over the past few years. We also discuss the technical
evolution of BLUSE, examine challenges faced and addressed, and consider avenues for future research and development.
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All authors Daniel J. Czech, David H.E. MacMahon, Ian Heywood, Chenoa D. Tremblay, Matt Lebofsky, Kevin Lacker, Cherry Ng, Dave Horn, Sarah Buchner, Brian Lacki, Alex Andersson, Joe S. Bright, Steve Croft, Dave R. DeBoer, Jamie Drew, Vishal Gajjar, Peter Ma, Alex W. Pollak, Danny Price, Mark Ruzindana, Andrew P.V. Siemion, S. Pete Worden, Fernando Camilo
Cosmology and Nongalactic Astrophysics
Scalar-induced gravitational waves from inflation with symmetry breaking
Chong-Bin Chen, Jia-Xi Feng, Fu-Wen Shu et al. (+1 more)
We investigate scalar-induced gravitational waves (SIGWs) in an inflationary model with
symmetry breaking, in which charged scalar fields are coupled to an isotropic triplet of Abelian gauge fields through a kinetic function. Such SIGWs can be enhanced to a detectable level when the mixing between the inflaton and gauge-field perturbations is sufficiently large. We find that the longitudinal mode and the charge-dependent mixing between perturbations become relevant only when the gauge-field excitation occurs sufficiently late during inflation. In this regime, the corresponding SIGWs are shifted to ultra-high frequencies, typically can around the GHz band. We show that the parameters characterizing the effects of the longitudinal mode and charge-dependent mixing affect the signal in qualitatively different ways. This provides characteristic signatures for distinguishing the neutral case from the charged one through the frequency profile of the
stochastic gravitational-wave background.
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All authors Chong-Bin Chen, Jia-Xi Feng, Fu-Wen Shu, Linjie Song
Quantum Physics
Neural Network Learning of One-Bit Protocols for Qubit Measurement Simulation
Josep Escrig, Mani Zartab, Giulio Gasbarri et al. (+3 more)
Communication complexity provides a natural framework for quantifying the classical resources required to reproduce
quantum statistics. In the
qubit prepare-and-measure scenario, two classical bits have been shown to be necessary and sufficient to simulate arbitrary
qubit states and arbi- trary
quantum measurements exactly. However, this result does not exclude the possibility that restricted families of measurements may admit accurate 1-bit classical approximations. We use a neural network procedure to demonstrate that a single bit can achieve high average accuracy for specific measurement families. A performance analysis of our neural network reveals that symmet- ric measurements with uniformly weighted elements, such as those forming regular polyhedra, are particularly amenable to this restricted communication. By analyzing the patterns learned by the neural network, we derive an analytical protocol that is extremely accurate for finite information- ally complete symmetric configurations and becomes exact in the limit of a continuous isotropic measurement.
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All authors Josep Escrig, Mani Zartab, Giulio Gasbarri, Estel Ferrer, Ramon Muñoz-Tapia, Gael Sentís
General Relativity and Quantum Cosmology
Two-Horizon Sector Thermodynamics as a Diagnostic for the Bi-Hair Organization of NUT Charge
Di Wu, Robert B. Mann and Shuang-Qing Wu
After decades without a fully self-consistent thermodynamic formulation, recent proposals for Lorentzian Taub-NUT spacetime have yielded several inequivalent descriptions, each satisfying its own first law and Smarr relation, leaving unresolved which formulation is physically preferred. In this Letter we introduce a two-horizon diagnostic whose sector temperatures are fixed by harmonic mean relations before the thermodynamic variables are chosen. For uncharged Taub-NUT, the sum sector closes with the mass and NUT charge, whereas, within the restricted homogeneous class examined here, the difference sector requires the thermodynamic secondary hair $J_n=mn$. This result supports a bi-hair thermodynamic organization of the NUT parameter through $N=n$ and $J_n=mn$. Furthermore, this two-horizon framework offers a new route toward addressing similar thermodynamic nonuniqueness in other two-horizon systems when the first law and Smarr relation alone do not identify a physically preferred formulation.
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High Energy Physics (Phenomenology)
Mass and Decay Properties of Toponium Using SUSY QM Factorization Method
Bhavishya Tepan, Manan Shah and P C Vinodkumar
The Supersymmetric
quantum mechanics (SUSY QM) factorization method is applied to study the Cornell potential in the context of toponium $(t\bar{t})$, the heaviest quarkonium system. The method is successfully applied to determine the mass, binding energy, and
spin-dependent hyperfine splitting, giving pseudoscalar $(\eta_t)$ and vector $(\Theta_t)$ state masses of 344.114 GeV and 344.141 GeV, respectively. The decay properties of both the pseudoscalar and vector states are also investigated through their respective decay widths, highlighting the crucial role of the bound-state wavefunction. Among the decay channels, the di-gluonic $(\eta_t\rightarrow gg)$ mode is found to be dominant, with an estimated decay width of 2.57 MeV. In addition, the spatial characteristics of toponium are examined by evaluating the mean radius, root-mean-square (RMS) radius, and most probable radius, all of which are found to lie within the range of $0.015\text{--}0.025\,\mathrm{fm}$.
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Quantum Physics
Optimal Dynamic Cooling of Multiple Qubits
Mattia Reda, Massimiliano Sacchi, Chiara Macchiavello et al. (+1 more)
We solve the closed-system problem of cooling $M$
qubits, selected from $N$ identical thermal
qubits, to the lowest common local temperature allowed by unitarity. The optimal protocol consists of two conceptually distinct steps. First, a passive rearrangement assigns the largest
eigenvalues of the initial state to target sectors of lowest Hamming weight, thereby minimizing the total target energy. Second, a target-only complex-Hadamard transformation within each fixed-Hamming-weight subspace equalizes the one-
qubit target marginals without changing any target-sector probability or the total energy. Consequently, imposing a common local temperature costs neither cooling depth nor additional work: the constrained optimum coincides with the unconstrained passive minimum for every $N>M$ and every initial temperature. The complex-Hadamard correction may nevertheless be costly at the
circuit level. We therefore derive an exact arithmetic criterion for when the same optimum can be attained by a temperature-independent computational-basis permutation alone, and exhaustively classify the resulting finite-size islands of feasibility for $M+2\leq N\leq 128$. At isolated temperatures, further optimal permutations can arise through numerical cancellations between different thermal
eigenvalue shells. These alternative realizations may reduce implementation complexity, but they cannot improve the cooling curve already attained by the universal protocol. We also derive the exact cooling curve, prove that at least two ancillary
qubits are necessary and sufficient for nontrivial cooling, and show that joint many-target cooling can strictly outperform parallel single-target strategies.
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All authors Mattia Reda, Massimiliano Sacchi, Chiara Macchiavello, Giacomo Guarnieri
Mathematical Physics · Cross-listed from math.PR
Non-equilibrium fluctuations of a two-species exclusion process with slow boundary
Ziying Chen and Yong Li
We study the non-
equilibrium density fluctuations of a one-dimensional two-species symmetric simple exclusion process in contact with critical slow boundary reservoirs. The boundary rates are of order $1/n$, which leads to Robin boundary conditions at the macroscopic level. We prove that the coupled fluctuation field associated with the empirical densities of two species converges to a generalized Ornstein-Uhlenbeck process. The limiting process is characterized by a linear martingale problem whose coefficients reflect the combined effects of bulk
diffusion, species conversion, and the boundary reservoirs.
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