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2603.16855 2026-03-18 cond-mat.stat-mech

Lifting the fog - a case for non-reversible "lifted" Markov chains

Gabriele Tartero, Sora Shiratani, Werner Krauth

Comments 7 pages, 5 figures (please contact authors for supplementary material)

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英文摘要

Phase transitions appear all over science, and are familiar from everyday life, as water boiling, sugar melting into caramel or as nematic molecules turning smectic in liquid-crystal displays. The dynamics of phase transitions can be extremely slow, as for example when fog in winter does not lift, that is when the coarsening takes much time from many tiny water droplets to fewer but larger rain drops that feel the pull of gravity. The dynamics of phase transitions is relevant also for the performance of computer algorithms. In the ubiquitous Metropolis Monte Carlo algorithm, the mixing dynamics towards equilibrium leads towards the solution of a sampling problem. It is governed by the same reversibility and detailed-balance principles as the overdamped physical dynamics of fog. For the phase-separated Lennard-Jones system, we describe here how the coarsening dynamics of non-reversible "lifted" variants of the Metropolis algorithm proceeds on much faster time scales, with the microscopic non-reversibility translating into large-scale relative motion of droplets that is impossible under the Ostwald-ripening condition of reversibility. A density-displacement coupling moves droplets relative to each other through a lensing effect. Efficient implementations of the long-range Metropolis algorithm and its non-reversible lifting (event-chain Monte Carlo) allow us to show that, in consequence, the coarsening growth exponent is larger under lifting. For large system sizes, the computing problem is thus solved infinitely faster than before, with the outcome strictly unchanged with respect to the Metropolis algorithm. We also discuss the larger setting of our findings, namely that "lifted" non-reversible algorithms can be set up for generic reversible sampling methods, with applications going much beyond our example of lifting fog.

2603.16852 2026-03-18 astro-ph.CO gr-qc

Beyond $Λ$CDM with a Logistic RG-like Flow of the Low Redshift Cosmic Evolution

Shibendu Gupta Choudhury, Anjan A Sen

Comments 9 pages, 5 figures

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英文摘要

Recent cosmological observations show hints for possible deviations from the standard $Λ$CDM paradigm at late times. To study such deviation, we introduce a minimal phenomenological framework in which the total equation of state of the Universe, $w_{\rm T}(z)$, follows a logistic evolution motivated by a renormalization group like flow between cosmological fixed points. This approach directly reconstructs $w_{\rm T}(z)$ probed by background observables, without assuming a specific dark energy model. Using DESI-DR2 baryon acoustic oscillation measurements, DES-Dovekie latest supernova data, and CMB distance priors, we find that the logistic parametrization provides an improved fit compared to $Λ$CDM and remains competitive with standard dynamical dark energy models. The inferred expansion history exhibits noticeable deviations from $Λ$CDM at low redshifts, reflected in the reconstructed jerk parameter. While the statistical significance of these deviations is model-dependent, our results highlight the potential of flow-inspired parametrizations as a complementary and physically interpretable framework for probing late-time cosmic dynamics.

2603.16845 2026-03-18 quant-ph

Efficient Shadow Tomography of Thermal States

Chi-Fang Chen, András Gilyén

Comments 20 pages, 1 figure

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英文摘要

We present a general protocol for estimating $M$ observables from only $\mathcal{O}(\log (M)/\varepsilon^2)$ copies of a Gibbs state whose Hamiltonian is accessible. The protocol uses single-copy, nonadaptive measurements and uses a total Hamiltonian simulation time of $\widetilde{\mathcal{O}}(βM/\varepsilon^2)$; we show that the sample complexity is optimal in a black-box setting where exponential time Hamiltonian simulation is prohibited. The key idea is a new interpretation of quantum Gibbs samplers as \textit{detailed-balance measurement channels}: measurements that preserve the Gibbs state when outcomes are marginalized. Consequently, shadow tomography of thermal states admits a general efficient algorithm when the Hamiltonian is known, substantially lowering the readout cost in quantum thermal simulation.

2603.16842 2026-03-18 cs.LG cond-mat.dis-nn cond-mat.stat-mech cs.SY eess.SY physics.bio-ph

Stochastic Resetting Accelerates Policy Convergence in Reinforcement Learning

Jello Zhou, Vudtiwat Ngampruetikorn, David J. Schwab

Comments 18 pages, 17 figures

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英文摘要

Stochastic resetting, where a dynamical process is intermittently returned to a fixed reference state, has emerged as a powerful mechanism for optimizing first-passage properties. Existing theory largely treats static, non-learning processes. Here we ask how stochastic resetting interacts with reinforcement learning, where the underlying dynamics adapt through experience. In tabular grid environments, we find that resetting accelerates policy convergence even when it does not reduce the search time of a purely diffusive agent, indicating a novel mechanism beyond classical first-passage optimization. In a continuous control task with neural-network-based value approximation, we show that random resetting improves deep reinforcement learning when exploration is difficult and rewards are sparse. Unlike temporal discounting, resetting preserves the optimal policy while accelerating convergence by truncating long, uninformative trajectories to enhance value propagation. Our results establish stochastic resetting as a simple, tunable mechanism for accelerating learning, translating a canonical phenomenon of statistical mechanics into an optimization principle for reinforcement learning.

2603.16840 2026-03-18 cs.CV cond-mat.mtrl-sci

What DINO saw: ALiBi positional encoding reduces positional bias in Vision Transformers

Moritz Pawlowsky, Antonis Vamvakeros, Alexander Weiss, Anja Bielefeld, Samuel J. Cooper, Ronan Docherty

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Vision transformers (ViTs) - especially feature foundation models like DINOv2 - learn rich representations useful for many downstream tasks. However, architectural choices (such as positional encoding) can lead to these models displaying positional biases and artefacts independent of semantic content. This makes zero-shot adaption difficult in fields like material science, where images are often cross-sections of homogeneous microstructure (i.e. having no preferred direction). In this work, we investigate the positional bias in ViTs via linear probing, finding it present across a range of objectives and positional encodings, and subsequently reduce it by finetuning models to use ALiBi relative positional encoding. We demonstrate that these models retain desirable general semantics and their unbiased features can be used successfully in trainable segmentation of complex microscopy images.

2603.16830 2026-03-18 physics.comp-ph

Sub-cell Wave Reconstruction from Differentiated Riemann Variables

Steve Shkoller

Comments 28 pages, 6 figures

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英文摘要

We introduce a postprocessing procedure that recovers sub-cell wave geometry from a standard one-dimensional Euler shock-capturing computation using differentiated Riemann variables (DRVs) -- characteristic derivatives that separate the three wave families into distinct localized spikes. Filtered DRV surrogates detect the waves, plateau sampling extracts the local states, and a pressure-wave-function Newton closure completes the geometry. The entire pipeline adds less than $0.25\%$ to the cost of a baseline WENO--5/HLLC solve. For Sod, a severe-expansion problem, and the LeBlanc shock tube, wave locations are recovered to within roundoff or $O(10^{-4})$ and the contact is sharpened to one cell width; a pattern-agnostic extension handles all four Riemann configurations with errors at the $10^{-6}$--$10^{-8}$ level. Direct comparison with MUSCL--THINC--BVD and WENO-Z--THINC--BVD shows that neither reproduces the combination of sharp contacts, small contact-window internal-energy error, and elimination of the LeBlanc positive overshoot achieved by the DRV reconstruction.

2603.16828 2026-03-18 cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con

Majorana Crystal in Rhombohedral Graphene

Chiho Yoon, Fan Zhang

Comments 6 pages, 3 figures

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英文摘要

Recent experiments in rhombohedral graphene report an unusual superconducting phase emerging from a spin- and valley-polarized quarter-metal state. The prevailing interpretation invokes chiral topological superconductivity, but the role of the `Fulde-Ferrell' phase factor due to intra-valley pairing has remained largely unexplored. Here we show, via a gauge transformation, that this phase is equivalent to an ordinary chiral topological superconductor on the triangular lattice, while simultaneously forming an extraordinary Majorana crystal on the dual honeycomb lattice reminiscent of the Haldane model.

2603.16820 2026-03-18 cond-mat.soft

Thermo-Rheological Memory of $κ$-Carrageenan Fluid Gels Formed Under Flow

Julien Bauland, Tim J. Wooster, Peter Fischer, Jan Vermant

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英文摘要

Fluid gels are soft materials formed by shearing biopolymer solutions during the sol-gel transition. Their ability to yield and flow beyond a critical stress makes them attractive for designing versatile, biocompatible materials in food, health care and medical applications. Although it is well established that both microstructure and mechanical properties depend on the shear applied during gelation, a unified physical framework linking these features remains lacking. Here, using $κ$-carrageenan gels as a model system, we use a combination of rheology and confocal microscopy to tackle their shear-induced structuring in fluid gels. We identify a thermo-rheological memory in $κ$-carrageenan gels formed under flow and show that it arises from a competition between shear and interparticle adhesion, captured by an Adhesion number. The resulting microstructural evolution is reminiscent of the behavior of attractive particulate dispersions under simple shear flow, thereby bridging gels made of macromolecules and particulate gels. This framework provides a route to tune fluid gel properties without altering their composition.

2603.16811 2026-03-18 physics.optics physics.ao-ph

Correlations of the phase gradients of the light wave propagating in a turbulent medium in the regime of strong scintillations

V. A. Bogachev, I. V. Kolokolov, V. V. Lebedev, A. V. Nemtseva, F. A. Starikov

Comments arXiv admin note: substantial text overlap with arXiv:2601.08272

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英文摘要

We investigate analytically and numerically correlation functions of the phase of light waves that propagate through turbulent media. We examine the case of strong scintillations that occur at large values of the Rytov dispersion, $σ^2_R$. Then, it is possible to relate the pair correlation function of phase gradients to the known pair correlation function of the envelope dependent on the distance $r$ assuming Gaussianity of the envelope of the beam. Our direct numerical simulations show that the profile of the pair correlation function for phase gradients gradually approaches the theoretical expression as the value of $σ_R^2$ increases, if $r<r_0$ where $r_0$ is the Fried length. For larger $r$ the behavior of the computed correlation function is quite different because of destroying the Gaussianity.

2603.16807 2026-03-18 nlin.PS physics.optics

Impact of phase modulation on the dynamics of temporal localized structures in injected Kerr microcavities

Marc Hunkemöller, Thomas G. Seidel, Julien Javaloyes, Svetlana V. Gurevich

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英文摘要

We theoretically investigate how phase modulation alters the dynamics of temporal localized structures (TLSs) in vertically emitting Kerr micro-cavities under detuned optical injection operating in the normal dispersion regime. We show that the emergence of TLSs in general is governed by a synchronization between the imposed modulation and the intrinsic pulse dynamics. We perform a multi-parameter bifurcation analysis of the underlying delay-algebraic equation model in the uniform field limit and demonstrate that weakly nonlinear and dissipative Hermite-Gauss modes shape the dynamics of dark TLSs, leading to a complex hybrid bifurcation structure. Beyond the uniform field limit, both bright and dark modulated TLSs are shown to exist and to occupy distinct equilibrium positions within the cavity. An effective equation of motion for the TLS positions is derived, showing a good agreement with the full model.

2603.16804 2026-03-18 cond-mat.soft

Visualizing shear-induced structures in carbon black gels by tomo-rheoscopy

Julien Bauland, Stéphane G. Roux, Stefan Gstöhl, Christian M. Schlepütz, Michael Haist, Thibaut Divoux

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英文摘要

Suspensions of attractive particles form space-spanning networks that endow the suspension with solid-like behavior at rest. The microstructure of these colloidal gels depends sensitively on the shear history and on the path followed across the sol-gel transition, resulting in viscoelastic properties that can be tuned by shear. Here, we report in situ X-ray tomo-rheoscopy experiments on carbon black gels whose elastic properties exhibit a non-monotonic dependence on the shear intensity applied prior to flow cessation. By directly imaging the gel microstructure under a well-controlled rheological protocol, we reveal the emergence of pronounced structural heterogeneities extending from tens to hundreds of microns -- length scales far larger than those accessible by conventional scattering techniques such as Ultra-Small Angle X-ray Scattering. In particular, we show that only the low-shear reinforcement of elasticity correlates with a growing mesoscale correlation length, while high-shear strengthening occurs without detectable mesoscale reorganization. These observations demonstrate that flow memory in colloidal gels is not solely governed by local particle rearrangements, but is also encoded in a mesoscale structural organization extending up to 100 times the particle size. More broadly, this work highlights the power of X-ray tomo-rheoscopy to uncover large-scale structural signatures of flow history in soft materials, opening new perspectives to tailor their mechanical properties.

2603.16796 2026-03-18 astro-ph.GA

A Unified Origin of Faraday Rotation toward 3C 84: The Circumnuclear Ambient Medium within the Parsec-Scale Bondi Radius of the Host Galaxy NGC 1275

Minchul Kam, Jongho Park, Sascha Trippe, Do-Young Byun, Keiichi Asada, Hiroshi Nagai, Motoki Kino, Luis Ho, Andrew Fabian, Jeffrey Hodgson, Kunwoo Yi, Kenji Toma, Junghwan Oh, Taehyun Jung

Comments 45 pages, 22 figures, accepted for publication in ApJ

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We present multi-frequency polarimetric observations of 3C 84 obtained with the Korean VLBI Network at 43-141 GHz, the Very Long Baseline Array at 43 GHz, and the High Sensitivity Array at 8 GHz from 2015 to 2024. We find that the Faraday rotation measure (RM) decreases systematically with distance from the black hole over 1-8 pc, following a single power-law trend of RM proportional to r^{-2.7+/-0.2}. Notably, RM measurements from earlier studies across the same distance range follow the same relation. This consistency across epochs, frequencies, and independent datasets indicates a common and stable external Faraday screen. These results naturally identify the circumnuclear ambient medium within the parsec-scale Bondi radius of the host galaxy NGC 1275 as the origin of the Faraday rotation, thereby resolving a long-standing question about its physical origin. From the RM profile, we derive radial distributions of the electron density and magnetic-field strength in the circumnuclear ambient medium that are consistent with independent constraints. The derived density lies below that of the free-free absorption disk and, when extrapolated inward, remains below the density of the broad-line region. The magnetic-field strength gradually increases from 0.1-1.5 microgauss at the Bondi radius to milligauss-to-gauss levels toward the black hole, providing the first spatially resolved constraint on the magnetic-field strength at parsec-scale distances in an elliptical galaxy. Together, these results present a spatially resolved and physically consistent picture of the circumnuclear environment in NGC 1275.

2603.16795 2026-03-18 quant-ph cs.IT math.IT

Boosted linear-optical measurements on single-rail qubits with unentangled ancillas

Aqil Sajjad, Isack Padilla, Saikat Guha

Comments 20 pages, 3 figures

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英文摘要

Any quantum state of the radiation field, sliced in small non-overlapping space-time bins is a collection of single-rail qubits, each spanning the vacuum and single-photon Fock state of a mode. Quantum logic on these qubits would enable arbitrary measurements on information-bearing light, but is hard due to the lack of strong nonlinearities. With unentangled ancilla single-rail qubits, an $8$-port interferometer and photon detection, we show any single-rail qubit measurement in the $XY$ Bloch plane is realizable with success probability $147/256$, which beats the prior-known $1/2$ limit.

2603.16784 2026-03-18 quant-ph cond-mat.stat-mech

Quantum signal processing in Hilbert space fragmented systems

Naoya Egawa, Kaoru Mizuta, Joji Nasu

Comments 10 pages, 5 figures

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英文摘要

Quantum signal processing (QSP), originally developed for composite pulse sequences in nuclear magnetic resonance systems, has recently attracted attention as a unified framework for quantum algorithms. A pioneering study applied QSP to nonequilibrium control in integrable many-body systems, enabling the realization of nonequilibrium dynamics with greater flexibility than Floquet engineering. However, extending QSP to nonintegrable systems faces fundamental obstacles arising from the limited number of conserved quantities and thermalization. In this work, we propose a protocol that leverages QSP in systems exhibiting Hilbert space fragmentation (HSF). Specifically, we consider a pair-hopping model with four-fold periodic potentials that exhibits an HSF structure, thereby providing integrable and nonintegrable sectors within a single system. We analytically show that nonequilibrium dynamics can be flexibly designed through QSP engineered by these potentials in the integrable sectors. In contrast, we numerically identify signatures of thermalization in the nonintegrable sectors. Remarkably, by inserting domain walls, we achieve parallel control of multiple quantum dynamics within a single system. This approach sheds light on the control of nonequilibrium dynamics from the perspective of quantum computation by extending the scope of QSP to nonintegrable systems.

2603.16782 2026-03-18 cond-mat.mes-hall

Magnetism Induced by Periodically Driven Non-Magnetic Impurities on Surfaces with Spin-Orbit Coupling

Malen Etxeberria-Etxaniz, Andrés Arnau, Asier Eiguren

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We investigate the response of the Rashba spin-orbit system to a time-periodic scalar potential, in order to determine whether an induced magnetization exists. We approach this by employing the Floquet-Green function method within the Keldysh formalism, computing the non-equilibrium steady state of the system. We find that, even in the absence of an external magnetic field, the system evolves into a state with an oscillating magnetization density that is remarkably rich in structure. We provide a detailed physical interpretation of the results by performing a Fourier decomposition in non-local momentum-space, which helps to uncover the physical origin of the induced magnetic field in terms of Fermi surface spin polarization and the system's dynamical character.

2603.16778 2026-03-18 cond-mat.soft cond-mat.stat-mech

Optimal multi-parameter control of trapped active matter

Luke K. Davis

Comments 16 pages, 12 figures

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The realization of efficient micro-machines built from active matter requires precise thermodynamic control far from equilibrium. Despite theoretical progress, the focus on single-parameter driving, coupled with strict theoretical assumptions, limits efforts to capture modern multi-parameter control experiments. Here, guided by careful theoretical considerations, we develop a transparent computational framework based on exact-gradient descent via automatic differentiation. We derive optimal protocols for a wide range of multi-parameter problems -- involving trap stiffness, trap center, and particle activity -- to minimize the thermodynamic work or heat. We demonstrate that smoothed, experimentally plausible protocols -- obtained by assigning kinetic costs to the controls -- achieve near-optimal efficiencies comparable to discontinuous ``bang-bang'' solutions. By exploring both open- and closed-loop control, we find the dynamical coupling between parameters leads to genuinely new strategies, including symmetry breaking in optimal activity cycles and non-monotonic trap stiffness controls. Further, we identify regimes where initial measurement and multi-parameter flexibility combine to improve efficiency. Finally, we reveal that the naive simultaneous execution of independently optimized controls incurs only slightly more work than the full multi-parameter solutions. Taken together, our work elucidates the non-equilibrium physics of multi-parameter control and provides robust, scalable strategies for controlling active matter.

2603.16775 2026-03-18 quant-ph cond-mat.quant-gas

How compactness curbs entanglement growth in bosonic systems

Stefan Aimet, Philipp Schmoll, Jens Eisert, Jörg Schmiedmayer, Spyros Sotiriadis

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Zero modes, understood here as degrees of freedom with vanishing confining frequency, play a central role in the nonequilibrium dynamics of bosonic systems. In Gaussian models, however, they lead to an unbounded, logarithmic growth of entanglement entropy. We show that this divergence is not an intrinsic property of zero modes themselves, but arises specifically for non-compact zero modes. Their non-compact configuration space allows unbounded spreading in position space, while their continuous spectra enable indefinite dephasing in momentum space. By contrast, compact zero modes in compact bosonic systems behave fundamentally differently: Spreading and dephasing are eventually halted, so that compactness caps the entanglement entropy at a finite value, making its dynamical role most transparent in the presence of a zero mode. We demonstrate this mechanism in a minimal setting by comparing two coupled harmonic oscillators with two coupled quantum rotors. We then show that the same physics persists in many-body systems by contrasting an N-site compact rotor chain with the non-compact harmonic chain. Finally, we relate these insights to ultra-cold-atom realizations of compact quantum field theories. In particular, we clarify when a compact free-boson (Tomonaga-Luttinger liquid) description is required and when the commonly used non-compact massless Klein-Gordon model breaks down. Even when the initial state is accurately captured by a non-compact Gaussian description, compactness ultimately governs the late-time quench dynamics, curbing entanglement growth rather than allowing a dynamical divergence.

2603.16762 2026-03-18 quant-ph cond-mat.stat-mech math-ph math.MP

An asymmetry lower bound on fermionic non-Gaussianity

Filiberto Ares, Michele Mazzoni, Sara Murciano, Dávid Szász-Schagrin, Pasquale Calabrese, Lorenzo Piroli

Comments 14 pages, 1 figure

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Fermionic Gaussian states are a fundamental tool in many-body physics, faithfully representing non-interacting quantum systems and allowing for efficient numerical simulations. Given a many-body wave function, it is therefore interesting to ask how much it differs from that of a Gaussian state, as quantified by the notion of non-Gaussianity. In this work, we relate measures of non-Gaussianity with the Shannon entropy of the particle-number distribution, coinciding with the particle-number asymmetry for pure states. We derive a lower bound on the relative entropy of non-Gaussianity in terms of the exponential of the Shannon entropy, and study numerically its tightness for large system sizes. Our bound is non-trivial for large values of the asymmetry and relies on the concentration of the particle-number distribution of (mixed) fermionic Gaussian states. Since the Shannon entropy of the particle-number distribution is often efficient to compute or experimentally measure, our results can be viewed as a practical way to lower bound non-Gaussianity, highlighting a non-trivial interplay with particle-number asymmetry.

2603.15695 2026-03-18 physics.flu-dyn

Non-inertial hydrodynamics of manipulating particle transport

Partha Kumar Das

Comments PhD thesis

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Inspired by numerous lab on a chip, biomedical and bioengineering applications such as cell sorting, focusing, trapping, and filtering of particles, manipulation of micron sized particle trajectories has been of significant interest in the context of microfluidics. Systematic deflection of microparticles away from their initial streamlines is a central objective in microfluidic particle manipulation. In many widely used microfluidic platforms including deterministic lateral displacement (DLD) devices, density matched, force free particles suspended in low Reynolds number flows encounter arrays of obstacles that potentially breaks the flow symmetry and alter their trajectories. Despite the prevalence of these devices, the physical mechanism responsible for particle deflection from encountering obstacle wall in strictly non inertial flows (Stokes flows) remains incompletely understood and is often attributed to short range contact interactions rather than hydrodynamic effects.

2603.13684 2026-03-18 hep-th

On the Gauge-Invariant Fermion

Kang-Sin Choi

Comments 4 pages; v2: clarifications

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We show that the Dirac dressing of the fermion is equivalent to a shift of the gauge parameter. For every gauge, the gauge-dependent part is projected out of physical observables. After renormalization, the physical mass is the same for every dressing. The non-locality, compositeness and path dependence associated with the dressing are therefore not physical obstructions.

2603.08261 2026-03-18 physics.flu-dyn physics.geo-ph

Magnetoconvection in a spherical shell: Equatorial symmetry during the transition from the weak- to the strong-field regime

Luke J. Gostelow, Robert J. Teed

Comments 30 pages, 20 figures

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At small but supercritical Rayleigh numbers, simulations of dynamos in spherical shells often separate into two broad regimes characterised either by their relative magnetic field strength (weak/strong) or by their dominant force balance (VAC/MAC). These regimes can tend smoothly from one to the other but can also be bistable, a phenomenon which occurs particularly at large $\Pm$. We show that in either case the transition correlates with a breaking of equatorial symmetry. Nonlinear simulations of the geodynamo cannot be performed at accurate parameters and hence it is important to ensure that the correct (strong-field) branch is tracked as a distinguished limit is tracked towards a correct parameterisation from the simulations that we can perform. In order to understand the transition to strong-field dynamos, and better understand the mechanisms that occur in both branches, we report on a series of magnetoconvection simulations (that is, with the magnetic field fixed at the outer boundary) with which we bridge the gap between the strong- and weak-field regimes, and show that symmetry-breaking is triggered by the sudden growth of the magnetic field and in turn supports the dynamo in the strong-field regime.

2603.02106 2026-03-18 quant-ph

Obstacles to Continuous Quantum Error Correction via Parity Measurements

Anton Halaski, Christiane P. Koch

Comments Changed Fig. 5, rewrote Sec. IV A, added references, minor adjustments

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Time-continuous quantum error correction, necessary to protect quantum information under time-dependent Hamiltonians, relies on weak continuous syndrome measurements. Implementing these measurements requires a continuous coupling among at least two qubits and a meter, a demanding requirement. We show that, under continuous operation, common parity-measurement protocols in the circuit quantum electrodynamics platform corrupt the logical information. The failure arises from approximating the three-body interaction by a sum of two-body couplings to the meter, which prevents simultaneous suppression of measurement backaction on the logical and error subspaces. We argue that the same mechanism applies more generally beyond the circuit quantum electrodynamics setting. Taken together, our results impose a practical limitation on continuous stabilizer quantum error correction and point to the viable alternatives -- architectures that realize native three-body interactions, or erasure-based encodings in which the error subspace need not be protected.

2603.01979 2026-03-18 astro-ph.SR

Core-envelope coupling of gravito-inertial waves in pre-main-sequence solar-type stars

Sylvain N. Breton, Camilla Pezzotti, Stéphane Mathis, Lisa Bugnet, Maria Pia Di Mauro, Johannes Joergensen, Konstanze Zwintz, Antonino F. Lanza

Comments 11 pages, 7 figures. Accepted for publication in A&A

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Journal ref
A&A 707, L16 (2026)
英文摘要

After the recent detection of solar equatorial Rossby waves, a renewed interest has been brought to the study of gravito-inertial waves propagating in the convective envelope of solar-type stars. In particular, the ability that some of these envelope gravito-inertial modes have to couple with the ones trapped in the radiative interior might open new windows to probe the deep-layer dynamics of solar-type stars. The possibility for such a coupling to occur is particularly favoured in pre-main sequence (PMS) solar-type stars. Indeed, due to the contraction of the protostellar object, they are able to reach large rotation frequencies before nuclear reactions are ignited and magnetic braking becomes the driving mechanism for their rotational evolution. In this work, we therefore study the coupling between the envelope inertial waves and the radiative interior g modes in PMS stars, focusing on the case of prograde dipolar modes. We consider the case of 0.5 Msun and 1 Msun PMS models, each with three different scenarios of rotational evolution. We show that, for stars that have formed with a sufficient amount of angular momentum, this coupling can occur in frequency ranges that are accessible to space-borne photometry, creating inertial dips in the period spacing pattern. With an asymptotic analysis we characterise the shape of these inertial dips to show that they depend on rotation and on the stiffness of the convective-radiative interface.

2602.22468 2026-03-18 astro-ph.EP astro-ph.IM astro-ph.SR

PICASO 4.0: Clouds and Photochemistry in Climate Models of Brown Dwarfs and Exoplanets

James Mang, Natasha E. Batalha, Caroline V. Morley, Nicholas F. Wogan, Sagnick Mukherjee, Channon Visscher, Mark S. Marley, Jonathan J. Fortney, Katy L. Chubb, Peter Gao, Isaac Malsky

Comments Published in ApJ. Code available here: https://github.com/natashabatalha/picaso along with documentation here: https://natashabatalha.github.io/picaso/

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We present a major update to the open-source atmospheric modeling package \texttt{PICASO}, designed for simulating the thermal structure and spectra of hydrogen-rich atmospheres of brown dwarfs and exoplanets. This release, \texttt{PICASO 4.0}, expands upon the existing radiative-convective equilibrium model framework by incorporating several new capabilities. Key additions include the integration of \texttt{Virga} for self-consistent cloud modeling, new flexible treatments for rainout and cold trapping of volatile species, and support for photochemistry. We also introduce a parameterized energy injection scheme to simulate additional external or internal heating processes. These features are motivated by lessons from recent JWST observations that reveal the prevalence of non-equilibrium chemistry and clouds. We benchmark the new functionalities against previously published results in the literature, including the Sonora Diamondback grid, energy injected atmospheres, patchy cloud models, and other photochemical models of WASP-39b. \texttt{PICASO} continues to be actively developed as an open-source package aimed at enabling reproducible, community-driven atmospheric modeling of all substellar objects.

2602.18209 2026-03-18 astro-ph.GA

The GUAPOS project -- VII: Physical structure and molecular environment of the G31.41+0.31 HII region

R. Cesaroni, M. T. Beltrán, V. M. Rivilla, Á. Sánchez-Monge, L. Colzi, F. Fontani, Á. López-Gallifa, A. Lorenzani, C. Mininni

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Journal ref
A&A 707, A327 (2026)
英文摘要

Ionised regions around OB-type stars are formed at an early stage of their evolution and are important to investigate the formation process of these objects. However, so far only few observations of their physical structure and interaction with the parental molecular cloud have been made. The high resolution and sensitivity of new instruments such as ALMA and the upgraded VLA allow us to fill this gap in our knowledge. We investigate the well known core-halo ultracompact HII region G31.41+0.31 and the surrounding molecular clump with the aim to determine the density and temperature of both the ionised and neutral gas, and possibly obtain a 3D picture of their spacial distribution. We take advantage of the full-band frequency coverage at 3 mm obtained with ALMA for the GUAPOS project to image the emission of a plethora of hydrogen recombination lines towards the G31.41+0.31 HII region as well as several molecular transitions which are tracers of medium-density ($\sim$$10^4$--$10^6$ cm$^{-3}$) gas. The line data are complemented by continuum measurements obtained with the VLA at 1 cm and 7 mm. By fitting these lines also using a model that takes into account non-LTE effects we can investigate the density and temperature structure and the velocity field of the region. Our findings, based on a model fit accounting for non-LTE effects, indicate that the electron temperature of the HII region is mostly spanning a range between 5000 and 6000 K, while the density varies between 2500 and 7500 cm$^{-3}$. All in all, the distribution of these parameters as well as the corresponding velocity field hint at a cometary shaped HII region expanding away from the observer to the NW. The molecular gas appears to be still infalling towards the peak of the UC HII region, and its density and temperature are consistent with pressure confinement of the ionised gas to the SE.

2602.14604 2026-03-18 astro-ph.SR astro-ph.EP astro-ph.GA

Infrared spectra of methane-containing ice mixtures for JWST data analyses

Varvara Karteyeva, Ruslan Nakibov, Igor Petrashkevich, Mikhail Medvedev, Anton Vasyunin

Comments 9 pages, 4 figures, 2 tables, accepted to Astronomy&Astrophysics

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Journal ref
A&A 707, A293 (2026)
英文摘要

Context. Solid methane (CH$_4$) is an important molecule in interstellar and planetary environments, serving as a precursor to complex organic compounds, and it is a potential biosignature in exoplanetary studies. Despite its significance, laboratory data on the low temperature phase of methane below 10 K remain limited. Aims. We obtained spectra of methane in binary mixtures at 10 K and compared them to the spectra obtained at 6.7 K. These temperatures correspond to phases II and II* of pure methane and are representative of dark molecular clouds and protostars in early stages. We also tested whether the data we obtained can be applied to interpret JWST data. Methods. Laboratory reference spectra were obtained with the ISEAge setup via Fourier transform infrared spectroscopy in transmission mode. A weighted $χ^2$ minimization was used for the fitting. Results. We present infrared spectra with corresponding band strengths of pure methane and binary mixtures with methane: CH$_4$:H$_2$O, CH$_4$:CO$_2$, CH$_4$:CH$_3$OH, and CH$_4$:NH$_3$ at 6.7 K and 10 K. They show an increase of 20% in mixtures compared to the commonly used 10 K band strength value of pure methane. We also tested whether the spectra can be used on open JWST data by probing the spatial distribution of methane in B335. We also present additional experiments concerning the phase transition of methane between phase II* and phase II. Conclusions. Our results reveal distinct spectral features for methane in non-H$_2$O environments that enable a more accurate interpretation of JWST observations. The dataset of spectra is publicly available on Zenodo and can be used for fitting JWST data.

2602.10070 2026-03-18 astro-ph.SR

Gaia white dwarfs with infrared excess I. The 100 pc catalogue

R. Murillo-Ojeda, F. M. Jiménez-Esteban, A. Rebassa-Mansergas, S. Torres

Comments Accepted in A&A

详情
Journal ref
A&A 707, A268 (2026)
英文摘要

The presence of infrared excess flux observed in white dwarfs (WDs) is related to the existence of debris disks or substellar companions. These systems provide important clues in the study of extrasolar planetary material and binary evolution. However, fully characterising their properties requires a statistically significant, complete sample. This work aims to identify a complete sample of WDs with infrared excess emission within 100 pc of the Sun. We built the spectral energy distributions (SEDs) of the WDs using synthetic photometry in 56 optical filters of the J-PAS system, generated from Gaia Data Release 3 low-resolution spectra and complemented with the latest infrared photometry available at the Virtual Observatory (VO). VOSA was used to fit the SEDs with different atmospheric WD models depending on the source spectral type. We visually checked optical and infrared images to identify contaminated photometry. We built a catalogue of 456 infrared excess WDs, of which 292 are robust identifications, and 164 are candidates. 351 ($\sim$75%) are new identifications. This implies a fraction of infrared excess WDs between 5.9$\pm$0.3% and 9.2$\pm$0.4%, higher than previous works, but in agreement with some more recent estimates. Furthermore, for the sample of infrared excess WDs, the fraction of sources with non-hydrogen atmosphere increases with the Gaia GBP-GRP colour, contrary to the general WD population. However, this result should be interpreted with caution. Additionally, a thorough comparison of our catalogue with those of previous studies was performed. The sample of WDs with infrared excess emission within 100 pc presented in this work is the largest, most complete and reliable to date. Due to their proximity, they are ideal targets for follow-up studies aimed at characterising circumstellar disks, substellar companions, and the composition of accreted planetary material.

2602.09886 2026-03-18 astro-ph.HE

In-flight calibration of the INTEGRAL/IBIS Compton mode: Application to the Crab Nebula polarization

Tristan Bouchet, Philippe Laurent, Floriane Cangemi, Jérôme Rodriguez

Comments 15 pages, 19 figures. Accepted for publication in A&A

详情
Journal ref
A&A 707, A340 (2026)
英文摘要

The INTEGRAL satellite explored the gamma-ray sky since its launch on October 17, 2002, and until the end of its scientific operation on February 28, 2025. A large fraction of the available data is still largely untouched, due to the complexity of analysis. We describe the latest in-flight calibration of the Compton mode of the INTEGRAL/IBIS telescope, taking into account more than twenty years of data. The spectroscopy and polarization of the standard candle that is the Crab Nebula is analyzed in detail. We operate the IBIS telescope as a Coded mask Compton telescope, using the Crab Nebula to refine the calibration, as is usually done for high-energy instruments. We have determined the spectroscopic and polarimetric properties of the IBIS Compton mode and their evolution along the entire duration of the mission. In addition, the long-term evolution of the Crab Nebula's polarization has been successfully measured and compared with other high-energy experiments. We could estimate the energy dependence of the Crab Nebula polarization in four bands between 200 keV and 1 MeV. In particular, the detection of polarized emissions strictly above 400 keV makes it the highest energy measurement ever performed for the Crab Nebula. A Python library was also made publicly available to analyze processed data.

2602.09308 2026-03-18 astro-ph.GA

Selecting Post-Starburst Galaxies Based on Star Formation History

Sara Starecheski, K. Decker French, Vicente Villanueva, Sebastion F. Sanchez, Tony Wong, Margaret E. Verrico, Alex Green, Akshat Tripathi, Keaton Donaghue

Comments Accepted for publication in ApJ

详情
英文摘要

Post-StarBurst (PSB) galaxies are galaxies that have undergone a large burst of star formation followed by rapid quenching. Understanding their properties as a population can help us better understand how galaxies evolve to quiescence. This project aims to use Star Formation History (SFH) measurements from the Integral Field Spectroscopy (IFS) surveys MaNGA, CALIFA, and AMUSING++ processed with the Pipe3D analysis pipeline in order to select PSB galaxies as well as PSB regions in galaxies. Most PSB selection methods use cutoffs determined by spectral features, but in this work we introduce a new PSB selection method based directly on the property we are most interested in; inferred SFHs. IFS data allows us to probe a galaxy's star formation on a spatially resolved scale, enabling us to examine the size, shape, and location of PSB regions within a galaxy. We select 107 PSB galaxies, only 7 of which are among known PSBs selected by other methods. Unlike traditional PSB selection methods, our approach is not biased against Active Galactic Nuclei (AGN). Despite this, we still find no evidence for a significant Seyfert 2 PSB population, suggesting that strong AGN activity is uncommon throughout the PSB phase. Our spatially-resolved SFH selection identifies a wide range of galaxies, including globally quiescent elliptical galaxies with centrally-concentrated PSB spaxels, galaxies with ring-like PSB spaxels and a preference for inside-out age gradients (contrary to what has previously been observed in the literature), and galaxies with widespread PSB regions that have significant star formation elsewhere in the galaxy.

2602.09272 2026-03-18 quant-ph

The Quantum Many-Worlds Interpretation, Simply Told

Brian C. Odom

详情
英文摘要

The many-worlds interpretation (MWI) of quantum mechanics poses a simple question. What would reality look like if everything evolved in time according to the same quantum equations? There is an attractive consistency to treating microscopic objects, measuring devices, and observers all on the same footing, but do the predictions match our observations? Here, we build a model for a bolometer detector making a which-path measurement in an atom interferometer. We discuss the MWI claim that, while both measurement outcomes occur in each experimental iteration, an observer will experience only one outcome or the other, with a probability consistent with experiment. Finally, we discuss how MWI does not have action at a distance. This article is written to be accessible to anyone with an undergraduate course in quantum mechanics.