Fluid Dynamics
An experimental study on the heat transport in porous media convection
Jing Dong, Lu Zhang and Ke-Qing Xia
We investigate the heat transport in porous media convection over a wide Rayleigh–Darcy number range of $26.8\leq Ra\leq 2.62\times 10^5$, and a Darcy number range of $6.18\times10^{-7}\leq Da\leq 1.21\times 10^{-5}$. In the experiments, we employ 3D-printed
lattice structures as the solid porous
matrix and water as the working fluid. Quantitative analyses of the porous medium Nusselt number $Nu_m$ and local temperature statistics reveal that the present system undergoes a transition through five distinct regimes: I. Conduction, II. Convection, III. Oscillation, IV. Transition, V. Classical Rayleigh–Bénard convection. This transitional process bridges the gap between Rayleigh–Darcy-like behaviour and Rayleigh–Bénard-like behaviour in porous media convection. By varying the permeability of the
matrix, we further examine the role of the Darcy number $Da$, which turns out to have a profound impact on the transitional processes across different regimes. Flow field measurements reveal that the flow structures within Regime IV and Regime V evolve from several horizontally stacked convection rolls to a single-roll structure, and the pore-scale Reynolds number both exceeds unity in these two regimes. Finally, we report the corresponding phase diagram in the $Ra$-$Da$ space.
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High Energy Physics (Theory)
Spinning bulk-to-boundary correlators in the massless theories with Poincaré symmetry
Jiang Long, Yu-Xuan Wei and Xin-Hao Zhou
We classify the bulk-to-boundary correlators for general integer-
spin $s$ operators in a Poincaré-invariant theory by imposing suitable fall-off conditions near future/past null infinity. Any bulk-to-boundary correlator is a linear superposition of a set of basic tensor structures fixed by the little group \text{ISO}(2) of massless particles. We map the independent tensor structures to all possible non-crossing double-line diagrams. A further mapping of the double-line diagrams to circular diagrams shows that all independent tensor structures are tensor products of loop diagrams. By extrapolating the bulk-to-boundary correlators to boundary-to-boundary correlators, we find a rich structure for general
spin-$s$ operators. Furthermore, we show that the extrapolated operator lies in a type Ib
spin-$s$ multiplet representation of Carrollian conformal field theory (CCFT). This is a net representation that generated by the Wigner translation generators.
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Nuclear Theory
Equilibrium state of a Fermi system in the diffusion approximation of kinetic theory
Sergiy V. Lukyanov
A consistent transformation from momentum space to energy space is performed for the
diffusion equation within kinetic theory, with particle-number conservation explicitly preserved. Under the assumption of a constant single-particle level density, the equation reduces to a one-dimensional
diffusion equation in energy space with consistent kinetic coefficients. The equivalence of the definitions of the
equilibrium temperature in momentum space and in energy space is demonstrated. It is established that the inclusion of the energy dependence of the kinetic coefficients leads to an energy-dependent
equilibrium temperature and a modification of the distribution function. The obtained results may be used to analyze relaxation processes in atomic
nuclei and nonequilibrium dynamics of
Fermi systems.
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Nuclear Experiment
Emerging collectivity and phase transition in mass A$\approx$150 region. New information for Nd isotopes
W. Urban, T. Rząca-Urban, J. Wiśniewski et al. (+2 more)
Low and medium
spin excitations in $^{146,148,150,152}$Nd isotopes, populated in $\beta^-$ decay of corresponding Pr isotopes or in
prompt-$\gamma$ fission of $^{252}$Cf have been studied using Gammasphere array of Ge spectrometers. 159 new levels, including two new isomers, 305 new $\gamma$ transitions and 83 new
spin-parity assignments were added in the four studied
nuclei. The structure of excited levels in the studied Nd isotopes is discussed using phenomenological classifications and systematics and compared to calculations reported in other works. Particular
attention is paid to $0^+$ and $2^+$ excitations related to the emerging quadrupole collectivity and to the role of the 11/2$^-$[505]
neutron extruder in the process.
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All authors W. Urban, T. Rząca-Urban, J. Wiśniewski, A.G. Smith, J.P. Greene
Quantum Physics
Reliability of asymptotic work extraction
Kaito Watanabe, Bartosz Regula, Marco Tomamichel et al. (+1 more)
Extracting work from
quantum states is a fundamental task in
quantum thermodynamics. Previous studies have primarily focused on determining the best achievable rate of work extraction, and remarkably, this characterization appeared to remain unchanged regardless of the choice of allowed processes: whether one considers the operationally motivated class of energy-conserving thermal operations, or the axiomatic class of Gibbs-preserving operations, the optimal extractable work is given by the Helmholtz free energy. Here, we challenge this perspective, showing that a more refined analysis of the asymptotic performance of work extraction reveals significant differences in the performance for the two different classes of free operations. Precisely, we focus on the trade-off between the extraction rate and its reliability, characterized by the optimal asymptotic speed at which the extraction error can be suppressed. We establish that the reliability of Gibbs-preserving operations and of thermal operations are respectively characterized by the Petz and the sandwiched Rényi relative
entropies, demonstrating that the former in general strictly outperforms the latter, and providing new interpretations of several information-theoretic divergences. Our analysis reveals that operational constraints such as energy conservation impose stronger limitations on the achievable precision of
quantum tasks than can be inferred from their asymptotic rates, thereby questioning the use of Gibbs-preserving operations as a mathematically convenient substitute for the physically realizable thermal processes.
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All authors Kaito Watanabe, Bartosz Regula, Marco Tomamichel, Ryuji Takagi
Quantum Physics
Quantum enhanced rare event discovery and sampling
Naixu Guo, Po-Wei Huang, Qisheng Wang et al. (+4 more)
Financial crashes, cascading failures in infrastructure, and critical errors in AI systems are frequently triggered by events that occur with extremely small probability. Efficiently discovering and sampling events with probability below a threshold is therefore of critical interest. Yet this task is highly non-trivial using existing classical or
quantum methods. Being rare, such events require an immense sampling overhead to collect sufficient data samples. Moreover, because the rare events are not known in advance, they cannot be flagged for amplification using standard techniques. Here, we introduce a
quantum algorithm for rare-event discovery and sampling without first learning which events are rare. The
algorithm achieves the optimal
quantum scaling with the rarity threshold. We further demonstrate that this can achieve a quadratic speedup for heavy-tailed systems whose tail has nonvanishing total mass, and translates into a robust
polynomial speedup for stationary
stochastic processes, with the exponent determined by its
entropy-rate structure.
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All authors Naixu Guo, Po-Wei Huang, Qisheng Wang, Jayne Thompson, Patrick Rebentrost, Mile Gu, Chengran Yang
Fluid Dynamics
Wall Shear Stress Reconstruction from Concentration: Differentiable Physics and Physics-Informed Neural Networks
Mahmoud Elhadidy, Siva Viknesh, Roshan M. D'Souza et al. (+1 more)
Wall shear stress (WSS) governs near-wall transport dynamics and is a key hemodynamic indicator in cardiovascular flows, yet remains difficult to infer accurately due to the need for precise computation of near-wall velocity gradients. Passive scalar fields, such as concentration or temperature, are advected by the same underlying velocity field and have the potential to uncover hidden flow physics metrics such as WSS. In this work, we demonstrate such reconstruction from spatially limited passive scalar observations using two fundamentally different inverse frameworks: a differentiable physics framework based on discrete adjoint, PDE-constrained optimization, which enforces the governing equations as hard constraints, and physics-informed neural networks (PINNs), which treat them as soft constraints.
Benchmark problems include a 2D canonical backward-facing step (2D-BFS) and a 3D patient-specific stenotic coronary artery. For the 2D-BFS case, evaluated under three measurement scenarios (near-wall, far-field, and combined), PINN achieves high accuracy when near-wall data are available but fails when restricted to far-field measurements, whereas the differentiable physics approach recovers accurate WSS across all scenarios. In the 3D patient-specific case, the differentiable physics framework outperforms PINNs, yielding accurate WSS reconstruction. These results establish that measurement location and inverse formulation jointly determine reconstruction fidelity in scalar-based near-wall flow inference. The proposed framework opens a path toward estimation of near-wall hemodynamics from scalar transport data, with broader applicability to fluid flow problems where passive scalars can be observed.
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All authors Mahmoud Elhadidy, Siva Viknesh, Roshan M. D'Souza, Amirhossein Arzani
High Energy Astrophysical Phenomena
A micronova burst in the intermediate polar IGR J17014-4306
Alexandre S. Oliveira, D. C. Souza, G. J. M. Luna et al. (+1 more)
We report the detection of a short optical burst in TESS data of IGR J17014-4306, the eclipsing intermediate polar with the longest known orbital period. The burst lasts 1.56 d and shows multiple peaks, reaching $(9.3 \pm 0.2) \times 10^{33}$ erg s$^{-1}$, and releases a total energy of $(3.25 \pm 0.01) \times 10^{38}$ erg. The burst parameters are consistent with those of a micronova eruption, currently understood as a thermonuclear runaway in the magnetically-confined
accretion column. From its energy, we infer a burned column mass of $\sim 1.6 \times 10^{-11}$ M$_\odot$, which implies a recurrence time of $\sim 20$ d. Our search for similar events in long-term
Gaia, ASAS-SN, and AAVSO light curves reveals 16 possible fast brightenings over $\sim 11$ yr, suggesting that micronova events may be frequent in IGR J17014-4306. Timing analysis of the TESS data shows that the white-
dwarf spin period remains stable before and after the burst. During the burst, however, the power spectrum becomes more complex and exhibits multiple peaks. The classification of IGR J17014-4306 as a micronova brings the total number of confirmed systems to eight. Its extreme orbital period and eclipsing nature make it an ideal test-bed for further studies of magnetically confined thermonuclear burning on white
dwarfs.
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All authors Alexandre S. Oliveira, D. C. Souza, G. J. M. Luna, C. V. Rodrigues
Mesoscale and Nanoscale Physics
Kauser Zulfiqar, Martin Lang, Samuel J. R. Holt et al. (+3 more)
We investigate the excitation modes of confined synthetic-
antiferromagnetic (SAF) skyrmions using micromagnetic
eigenvalue and ringdown simulations. Starting from a single skyrmion in a
ferromagnetic layer, where the lowest-frequency modes are a gyrotropic and a breathing mode, we study how
antiferromagnetic interlayer coupling modifies the dynamics in SAF
bilayers. We consider several geometries: single SAF skyrmions in square and rectangular confinement, unequal layer thicknesses, and strips containing multiple skyrmions. The
antiferromagnetic coupling strongly modifies the low-frequency dynamics. The square geometry exhibits two nearly degenerate gyrotropic modes, where in each both layers have the same rotation sense. In rectangular geometries, we instead find nearly linear SAF skyrmion translation emerging from opposite gyration sense in the two layers. These translational modes become the characteristic low-frequency excitations of SAF skyrmion chains. For skyrmion chains, we identify collective translational and breathing modes with standing-wave-like spatial profiles. Beyond
ferromagnetic-like breathing modes, the SAF geometry supports breathing oscillations in which the two layers oscillate out of phase. We further demonstrate signal propagation along extended SAF skyrmion chains with propagation velocities comparable to
ferromagnetic skyrmion chains. These results provide a systematic description of the collective dynamics of SAF skyrmions arising from the interplay of
geometric confinement, intralayer, and interlayer coupling.
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All authors Kauser Zulfiqar, Martin Lang, Samuel J. R. Holt, Swapneel Amit Pathak, Florian Bruckner, Hans Fangohr
Biological Physics · Cross-listed from cs.LG
Reactive Flux Matching: Mechanism Discovery and Adaptive Sampling of Rare Events
Rishal Aggarwal, David Ryan Koes, Nicholas M. Boffi et al. (+1 more)
Path sampling methods generate ensembles of reactive trajectories connecting metastable states, but extracting mechanistic insight from these data remains nontrivial. We introduce Flux Matching, a framework that learns two complementary objects directly from reactive trajectory data: a current velocity $u(z)$, whose streamlines trace the dominant reaction pathways, and a scalar potential $h(z)$, obtained from a weighted Helmholtz-Hodge decomposition of the reactive current, that serves as a data-driven reaction coordinate. Both minimize quadratic functionals over the reactive path ensemble, analogous to the flow matching loss in generative modeling, and require no knowledge of the underlying dynamics or stationary distribution. Unlike committor-based methods, $u$ and $h$ remain well-defined under projection onto non-Markovian collective variables, and their level sets in turn provide adaptive interfaces for improved sampling with enhanced sampling methods. Flux Matching is validated through the generation of current velocity trajectories and rate constant calculations on molecular systems.
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All authors Rishal Aggarwal, David Ryan Koes, Nicholas M. Boffi, Eric Vanden-Eijnden
Statistical Mechanics · Cross-listed from q-bio.NC
Early psychosis shows deviations in scaling behaviour within a critical regime
Irem Topal, Paola Moreno Ancalmo, Guillermo Montaña-Valverde et al. (+2 more)
Accumulating evidence suggests that large-scale
brain activity exhibits scale-invariant dynamics consistent with operation in a near-critical regime. Such dynamics have been associated with long-range correlations, efficient information processing, and the emergence of collective organization. While altered criticality-related measures have been reported in psychiatric disorders, previous findings remain fragmented across observables and modalities, making it unclear whether different scaling measures capture a common alteration of large-scale
brain dynamics. Here, we investigated scaling properties in resting-state fMRI data from 77 human participants (27 female and 50 male), comprising individuals with early psychosis and healthy controls. We combined a phenomenological renormalization group (PRG) framework with power spectral density (PSD) and detrended fluctuation analysis (DFA) to characterize collective dynamics across scales. In healthy controls, resting-state activity exhibited nontrivial scaling behavior consistent with critical-like organization. Early psychosis participants showed non-trivial scaling behavior, but with systematic shifts in scaling exponents across multiple observables. These findings indicate a reorganization of collective dynamics in early psychosis, with spatial and temporal scaling properties showing distinct alterations that may reflect different changes in proximity to criticality. More broadly, our results suggest that combining coarse-graining approaches with temporal scaling analyses provides a principled framework for studying large-scale
brain dynamics in psychiatric disorders.
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All authors Irem Topal, Paola Moreno Ancalmo, Guillermo Montaña-Valverde, Philipp Homan, Wolfram Hinzen
Materials Science
Optical Signature of Moiré Superlattices Formed by Twisted SrTiO$_3$ Membranes
T. A. M. Ragib Shahriar, Fumikazu Murakami, Xing He et al. (+11 more)
Moiré superlattices formed at the interfaces of mismatched
lattices have attracted significant interest over the past decade due to their large tunability of band parameters and interactions among electrons,
spins, and
lattices. Superlattices made from twisted perovskite
oxides may have strong structure and potential modulation, but evidence of such modulation over macroscopic areas, particularly at large twisting angles, has not been clearly demonstrated so far. Here, we fabricated millimeter-scale twisted
oxide bilayers at $36^\circ$ angle, close to the simple coincidence site
lattice condition $\Sigma5$, from freestanding SrTiO$_3$ membranes. We discovered new low-frequency vibrational modes whose Raman activity, according to molecular dynamics simulations, is greatly enhanced by an asymmetric, twisted interface between the SrO and TiO$_2$ layers. Such an interface is energetically favorable from first-principles calculations and is corroborated by the observation of strong second harmonic generation from the interface comparable to that from the SrTiO$_3$ surface throughout the
bilayer region. The results are consistent with interlayer coupling enhanced by high-temperature annealing and confirmed by cross-sectional scanning transmission electron microscopy imaging. Our work sheds light on the structural behavior of twisted
oxides and provides directions for tuning their phononic and nonlinear optical properties in future studies.
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All authors T. A. M. Ragib Shahriar, Fumikazu Murakami, Xing He, Konnor Koons, Xinyan Li, Bumseop Kim, Shihan Qin, Varun Harbola, Jochen Mannhart, Yimo Han, Ruijuan Xu, Shengxi Huang, Andrew Rappe, Hanyu Zhu
Quantum Physics
Shan Jiang and Pan Peng
Triangles capture higher-order structures in graphs and are fundamental to applications such as clustering and network analysis. To enable efficient use of such structures at scale, we study the problem of triangle cut sparsification, which aims to reduce the graph size while approximately preserving triangle counts across every cut. We investigate
quantum algorithms for this problem, using triangle listing as our main technical ingredient. In particular, we present a
quantum algorithm for triangle listing that, for a graph with $n$ vertices, $m$ edges, and $t$ triangles, runs in time $T_{\mathrm{q\text{-}list}} =$ $\widetilde{O}\bigl(\min(n^{5/4}t^{7/12} + n^{7/6}t^{7/9}, m + m^{3/4}t^{1/2},$ $n^{3/2}t^{1/2})\bigr)$, improving upon the best known classical bounds over a broad range of parameters. Our
algorithm is based on a heavy-light vertex partition and an extension of triangle detection via
quantum walks and Grover search. Leveraging this result, we design a
quantum algorithm for constructing $\varepsilon$-triangle cut sparsifiers of size $\widetilde{O}(n/\varepsilon^2)$ in time $\widetilde{O}(T_{\mathrm{q\text{-}list}} + \sqrt{mn}/\varepsilon)$. Finally, we demonstrate applications to clustering
algorithms based on triangle-related measures and prove a lower bound of $\Omega(n/\varepsilon^2)$ on the size of any $\varepsilon$-triangle cut sparsifiers.
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High Energy Physics (Phenomenology)
Diffusion of multiple conserved charges from entropy production
Samapan Bhadury, Arpan Das, Sandeep Chatterjee et al. (+1 more)
We derive dissipative relativistic hydrodynamic equations in the presence of multiple conserved charges, i.e.,
baryon number ($B$), electric charge ($Q$), and strangeness ($S$), using the Chapman-Enskog (CE) method within the kinetic theory approach. The relativistic Boltzmann equation is solved within the relaxation-time approximation with a momentum-independent relaxation time in the collision term. We derive both first-order (Navier-Stokes limit) and second-order dissipative hydrodynamic equations. Within the kinetic theory framework, using the Boltzmann's H-
theorem, and by demanding that for a dissipative system, the
entropy must be produced, we find different transport coefficients at the first-order and second-order gradient expansion of the out-of-
equilibrium distribution function around the local
equilibrium. Apart from the well-known transport coefficients, the shear ($\eta$) and the bulk ($\zeta$) viscosities , we also find the
diffusion matrix elements ($\kappa_{qq^{\prime}}$) for the conserved charges $B$, $Q$ and $S$. The
diffusion matrix elements ($\kappa_{qq^{\prime}}$) are important to model the multi-component
diffusion dynamics sourced by inhomogeneous
baryon stopping in the initial state of heavy-ion collisions. We estimate the temperature ($T$) and chemical potential dependence of diagonal and off-diagonal elements of the
diffusion matrix elements for the (2+1)
flavor quark-
gluon plasma. We further estimate the ratio $\kappa_{qq^{\prime}}T/\eta$ for a wide range of temperature and chemical potentials to show the relative importance of the
diffusion matrix elements compared to other transport coefficients.
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All authors Samapan Bhadury, Arpan Das, Sandeep Chatterjee, Hiranmaya Mishra
General Relativity and Quantum Cosmology
On Cosmological Correlators with Boundary Contributions
Yanjiao Ma, Dong-Gang Wang, Xiangwei Wang et al. (+2 more)
Cosmological correlators receive contributions from both field interactions in the bulk of quasi-de Sitter (dS) spacetime and boundary terms at the end of inflation. While most of the research efforts focus on the former, boundary contributions are normally believed to be negligible or related to field redefinitions that are associated with redundancies of the bulk Lagrangian. In this paper, we revisit this topic in the light of the cosmological bootstrap. We first establish the correspondence between boundary terms and field redefinitions for cosmological correlators. This result provides a set of criteria for determining when boundary terms lead to non-vanishing contributions to cosmological observables. Next, we apply this general understanding to concrete examples of correlators from massive-exchange diagrams, in both dS-invariant and boost-breaking scenarios. For theories with dS isometries, both IBP and field redefinitions are used to relate derivative and non-derivative exchange diagrams, from which the leading boundary contributions and IR-divergent pieces are extracted; we also derive recursion relations among higher-derivative exchange correlators. For theories with broken dS boosts, we use IBP and EoM to reduce exchange diagrams to a basis of independent templates, and then present a classification of the boundary contributions in the general effective field theory framework. These results pave the way for a more systematic investigation on the boundary physics of the inflationary spacetime.
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All authors Yanjiao Ma, Dong-Gang Wang, Xiangwei Wang, Yi Wang, Wenqi Yu
Strongly Correlated Electrons
Discovery of hidden order in the Shastry-Sutherland magnet Nd2Be2GeO7
Andi Liu, Samuel H. Moody, Thomas J. Hicken et al. (+9 more)
Hidden order typically manifests as a thermodynamic phase transition without a conventional order parameter, leaving its true nature concealed even at the lowest temperatures. In the frustrated Shastry-Sutherland magnet Nd$_2$Be$_2$GeO$_7$, we observe a related yet fundamentally distinct phenomenon. A sharp specific-heat anomaly appears at 250 mK, but zero-field
neutron diffraction and
muon spin relaxation detect no static magnetism down to 100 and 30 mK, respectively, pointing to a hidden-order state. Remarkably, this hidden order does not emerge under an applied
magnetic field, but instead reveals itself only after the field is applied and subsequently removed where
magnetic Bragg peaks appear, albeit with strongly suppressed moments. A glassy state is ruled out by ac susceptibility and specific heat measurements. Complementary $\mu$SR measurements reveal coherent
spin fluctuations at a rate on the order of gigahertz. Taken together, these results suggest that the system lies in close proximity to the
quantum spin liquid and long-range
magnetic order state such that a small perturbation can effectively drive the system towards distinct ground states. These findings also distinguish Nd$_2$Be$_2$GeO$_7$ from known frustrated systems, establishing it as a unique platform where the synergistic interplay among the
spin-orbit coupling,
crystal field, and
magnetic frustration leads to unexpected
quantum states.
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All authors Andi Liu, Samuel H. Moody, Thomas J. Hicken, Jonas A. Krieger, Hubertus Luetkens, George D. A. Wood, Helen C. Walker, Zhendong Fu, Jason S. Gardner, Jinkui Zhao, Zhaoming Tian, Hanjie Guo
High Energy Physics (Theory)
A note on the 2D NLSM free energy
Yizhuang Liu
This note contains the perturbative computation of the 2D non-linear sigma model (NLSM) energy-density in a chemical potential $h$, at the fourth order in the coupling constant expansion. The result is in fully agreement with the $h\rightarrow \infty$ asymptotics extracted from the thermodynamical Bethe ansatz (TBA).
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Mathematical Physics · Cross-listed from math.DS
Existence of the C-type renormalisation two-cycle
Zainab Rahman, Maria Pickett and Andrew Burbanks
We prove the existence of the C-type renormalisation two-cycle, helping to establish the universality of the C-type route to chaos in families of non-invertible maps of the plane. Families of two-dimensional non-invertible maps, with at least two parameters and critical points of fold type, exhibit a distinct type of critical scaling, the C-type. An accumulation of parameter values leads to an infinite collection of coexisting attracting cycles of periods $4^n$ or $2\cdot 4^n$. Asymptotically, period quadrupling is accompanied by parameter-space scaling and state-space scaling governed by particular universal constants. Kuznetsov et. al. explained this phenomenon in terms of a stationary orbit of period two of the renormalisation group (RG) transformation for period-doubling. We prove the existence of the corresponding renormalisation two-cycle in a
Banach space of analytic maps and gain rigorous bounds on the corresponding universal state space scaling constants. This result provides a further step in proving a series of outstanding
conjectures concerning distinct universality classes for period-doubling. It extends the recent results for unidirectionally-coupled maps (the FS-type) to bidirectionally-coupled maps, and generalises the framework from fixed points to periodic orbits of the corresponding renormalisation operators. It also provides a further step in establishing the conjectured picture that the C-type universality class is born from the FS-type class via a period-doubling bifurcation in the dynamics of the RG transformation itself. The proof relies on rigorous computations to establish that a variant of Newton's method for the two-cycle is a contraction map. The C-type scaling regularity is known to occur in a number of dynamical systems of interest, perhaps most notably in biologically-plausible models of nephron blood pressure autoregulation.
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Astrophysics of Galaxies
Ghostly DLAs in SDSS DR16
Patrick Petitjean
In Petitjean (2026, A&A 710, 340), we revisited the origin of proximate damped Lyman-alpha absorbers (PDLAs), which trace cold gas within 3000 km/s of the
quasar redshift, and interpreted their kinematics and physical properties within a unified framework. We showed that most PDLAs are associated with the environment of the AGN and/or the
quasar host
galaxy. We also provided the first census and characterization of absorption systems exhibiting strong absorption from excited levels of atomic ground states among
quasar-associated absorbers. Among these, ghostly and coronagraphic systems arise in dense, compact gas that partially covers the
quasar emission regions. Most systems are associated with
outflows reaching velocities up to -2000 km/s, while a smaller fraction of inflowing clouds extends to velocities of up to +1200 km/s. In the present work, we provide an updated classification of PDLAs, including a revised catalogue of ghostly systems that more than doubles the number of previously known detections. We investigate the properties of these systems by measuring and discussing the equivalent widths of the detected absorption lines in both stacked spectra and individual ghostly systems. In particular, we show that although most ghostly systems are bona fide DLAs, this is not always the case.
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Fluid Dynamics
Turbulence-based parametrization of animal flight
Ariane Gayout, Eize J. Stamhuis and Casper J. van der Kooi
Animals capable of powered flight range in wingspan from a few hundred microns to a few meters. The inertial
turbulence to which these animals are exposed features
vortices ranging from a few hundred micrometers to hundreds of kilometers in size. Yet, the impact of ambient
turbulence on animal flight is virtually uncharted and most studies on animal flight are conducted in still air or under laminar conditions. Here, we propose a novel parameterization that links animal flight with
turbulence, through a proxy for the energy injected into the atmosphere, $E_{sp}=b^3 f^2$, with $f$ the animal's flapping frequency and $b$ the wingspan. We model this parameter using a scaling relation in the shape of a power law $E_{sp} \propto k^\alpha$, with $k=1/b$ the wavenumber corresponding to the animal inverse wingspan. Literature provides four theoretical predictions on the exponent $\alpha$: two connected to aerodynamic and energetic aspects of flight, $\alpha_{aero}=-2$ and $\alpha_{power}=-5/3$, and two linked to physiological limits. Drawing from experimental data of over 400 species spanning 13 insect orders and two vertebrate classes, we recover $\alpha_{power}=-5/3$ as the best scaling relation across the animal kingdom. Grouping per animal clade however reveals a secondary power law with $\alpha=-5/2$ exponent for invertebrate orders, with a family-dependent coefficient. This new scaling relation suggests a yet-unknown universal physical mechanism in insect flight, likely depending on wing morphology and mechanical properties.
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High Energy Physics (Phenomenology)
Spin-orbit correlation of quarks within quarkonium
Tianyang Hu, Xianghui Cao, Siqi Xu et al. (+3 more)
The
spin-orbit correlation (SOC) provides a unique probe into the internal
spin structure of
hadrons. Defined via the parity-odd (P-odd) energy-momentum tensor (EMT), this observable can remain non-vanishing even in systems where the total angular momentum is zero. In this study, we connect the formal field-theoretical definition of the SOC to a non-perturbative
quantum many-body framework utilizing light-front dynamics. Furthermore, we show how the SOC can be extracted directly from the hadronic
matrix elements of the P-odd EMT, establishing a pathway to access this observable within the partonic picture. As a practical application, we compute the transverse and longitudinal SOC distributions for charmonium and $B_c$
mesons. While our findings align with rough estimates based on the Clebsch-Gordan decomposition, we demonstrate that these observables yield rich, non-trivial information regarding partonic dynamics.
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All authors Tianyang Hu, Xianghui Cao, Siqi Xu, Weijie Du, Qin-Tao Song, Yang Li
Physics and Society
Assessing Power System Vulnerability to Climate-Related Stressors and Shocks: The Case of Indonesia
Hariadi Aji, Nihit Goyal, Stefan Pfenninger-Lee et al. (+1 more)
Climate change and extreme weather are increasing the vulnerability of power systems globally, particularly in emerging economies such as Indonesia. Yet, existing studies often assess these impacts in isolation, focusing on individual components or specific hazards, leaving system-level implications under-examined. To address this gap, we develop an integrated, spatially explicit approach to assess an energy system's
climate-related vulnerabilities and their impacts, and apply the approach to Indonesia. We quantify
climate-based vulnerabilities in generation and transmission infrastructure as well as in demand by distinguishing stressors (temperature rise) and shocks (disruptive hazards due to sea-level rise, flooding, and landslides). Through geospatial data analysis, derating models, and regression analysis, we examine existing and planned assets and demand under historical and future
climate conditions. Results indicate that both existing and planned generation are likely to experience stress, which implies a reduction in usable capacity, even as electricity demand increases due to temperature rise, and transmission assets face potential disruption from
climate change-induced shocks. Together, these effects erode reserve margins by up to 36 percentage points under the 10-year plan, indicating a substantial reduction in system resilience. The largest system, Jawa-Madura-Bali, experiences a 20.8 percentage point decline, leaving a remaining margin of 26.5%, below the 10-year planning threshold. Importantly, the findings suggest that a growing share of future capacity expansion may be absorbed by
climate-induced losses, implying that adaptation-related investments may increasingly be required simply to maintain existing supply levels rather than meet future requirements. We conclude that there is an urgent need to embed
climate considerations more explicitly into power sector planning.
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All authors Hariadi Aji, Nihit Goyal, Stefan Pfenninger-Lee, Igor Nikolic
Quantum Physics
Non-equilibrium thermodynamics of collapse models in the strongly non-Gaussian regime
Pedro B. Melo, Pedro V. Paraguassú, Simone Artini et al. (+3 more)
Standard objective collapse models offer a unified approach to the
quantum measurement problem but predict an unphysical, indefinite increase in the energy of the system. The dissipative Diósi-Penrose (dDP) model resolves this heating issue by introducing a linear friction mechanism. However, this modification induces complex, non-Gaussian phase-space dynamics. We rigorously establish the thermodynamic consistency of this friction mechanism – extended to the CSL model – across both weakly and strongly non-Gaussian regimes. Using the Wigner phase-space formalism, we go significantly beyond the quadratic approximation and, to bypass the failure of perturbative methods under strong dissipation, introduce a novel exact pseudo-spectral simulation approach. Our analysis reveals that the system subjected to the dDP mechanism does not thermalize, but rather settles into a non-
equilibrium steady-state (NESS) where the asymptotic non-Gaussianity scales as the third power of the dissipation parameter $\beta$. By evaluating the Wigner
entropy production, we confirm the thermodynamic validity of the model and demonstrate that highly sensitive information-theoretic quantities require exact numerical methods to accurately capture the key non-Gaussian tails of the distribution.
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All authors Pedro B. Melo, Pedro V. Paraguassú, Simone Artini, Gabriele Lo Monaco, Sandro Donadi, Mauro Paternostro
Soft Condensed Matter
Investigating frictional instability due to pressurization in granular media: insights from coupled computational fluid dynamics discrete element method
Bimal Chhushyabaga and Behrooz Ferdowsi
Fluid pressurization can reactivate subcritically stressed granular layers in faults, slopes, and injection-perturbed reservoirs, but grain-scale feedbacks among pressure
diffusion, drainage, and contact-network degradation remain unresolved. Here, 3D coupled CFD-DEM simulations investigate pore-pressure-induced reactivation of confined, fluid-saturated granular shear layers under imposed shear stress. Strain-controlled tests define the Mohr-Coulomb strength envelope; stress-controlled simulations then impose subcritical shear stresses while basal pore pressure increases under drained and undrained conditions. Instability is governed not by pore pressure alone, but by its coupled
evolution with effective stress, drainage, dilation or compaction, hydraulic connectivity, and granular fabric. Undrained boundaries retain excess pore pressure, whereas drained boundaries maintain vertical gradients and suppress excess pressure. Internal fields reveal alternating dilation and compaction bands and reorganization of a porosity-derived permeability proxy, showing that hydraulic pathways evolve during deformation. Micromechanical diagnostics identify localized particle rotation, force-chain reorganization, porosity redistribution, and coordination-number variations controlled mainly by imposed shear-stress level rather than drainage. Second-order fabric metrics show that post-failure weakening coincides with loss of directional force-chain organization, especially at lower shear. Friction-velocity and friction-porosity trajectories indicate a transition from dilatancy-dominated strengthening to pore-pressure-driven weakening. Viscous-number scaling partially organizes the low-Iv creeping response, 10^-8 <= Iv <= 10^-5, but not onto a unique local rheology. These results clarify how drainage-controlled hydromechanical feedbacks and fabric degradation convert pore-pressure forcing into instability.
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Astrophysics of Galaxies
Bar-induced deflection of open cluster tidal tails
Hanna Parul, Laia Casamiquela, Paola Di Matteo et al. (+1 more)
We present a systematic study of how the
Galactic bar affects the orientation of
tidal tails of open clusters and assess the power of tail morphology to constrain the bar's pattern speed. Using test-particle simulations, we follow the
evolution of $\sim 1450$ observed open clusters from the Hunt & Reffert (2024) catalogue in an axisymmetric reference potential and in eight barred potentials with pattern speeds ranging from $\Omega_b = 20$ km/s/kpc to $\Omega_b = 55$ km/s/kpc. We quantify the bar effect through the deflection angle – the rotation of the tail orientation in the barred model relative to the axisymmetric case. The deflection angle varies systematically with bar pattern speed and cluster guiding radius. The largest deflections occur for clusters near the outer Lindblad resonance (OLR), with the sign of the angle set by the orientation of the orbit's pericentre relative to the bar's major axis. For each cluster we measure the distance from the centre beyond which different bar models produce distinguishable tail orientations, and classify each cluster as bar-sensitive or bar-insensitive based on its maximum absolute deflection across the bar models. Comparing with observed
tidal tails from the literature, we find that the extended tails of NGC 2632 and the Hyades disfavour moderate pattern speeds. We provide a catalogue of deflection angles, minimal tail extents, and bar-sensitivity flags to guide future observational searches and the re-assessment of existing
tidal tail catalogues.
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All authors Hanna Parul, Laia Casamiquela, Paola Di Matteo, Salvatore Ferrone
Fluid Dynamics
A high-order Fourier Continuation (FC)-based spectral incompressible Smoothed Particle Hydrodynamics (ISPH) scheme for general boundary conditions in wall-bounded domains
Meixuan Lin, Georgios Fourtakas and Benedict D.Rogers
In this paper, a high-order
Fourier Continuation (FC)
algorithm is introduced into the spectral smoothed particle hydrodynamics (SPH) scheme to simulate the wall-bounded incompressible flows. This work aims to extend the spectral ISPH scheme towards the high-order simulation of flows with non-periodic wall boundary conditions. Herein, a
polynomial-based
Fourier continuation technique is applied to the velocity and pressure to make the domain both periodic and Cp smooth. The spatial SPH discretisation is performed subsequently in the frequency space on the FC-extended domain by building upon the convolution
theorem using fast
Fourier transform (FFT). The incorporation of Neumann boundary conditions is straightforward, and more generally, the FC method enforces periodicity across the domain regardless of the boundary condition type. The convergence order, additional computational cost, and implementation technique of the FC method are also discussed. Combined with a projection-based time integration scheme and a spectral PPE solver, the FC-based spectral ISPH framework is validated against several classical CFD
benchmarks. The principal finding of this work is that the incorporation of FC techniques enables the spectral ISPH scheme to simulate wall-bounded flows with high-order convergence, and accurately capturing complex
vortex dynamics. This work therefore represents a step towards a fully high-order spectral Lagrangian SPH solver with complex geometries
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Quantum Physics
Multiple Quantum Hypothesis Testing: One-Shot Pairwise Bounds and Sharp Asymptotics
Hao-Chung Cheng and Po-Chieh Liu
We consider
Bayesian discrimination among multiple
quantum states and establish a dimension-free one-shot upper bound on the minimum probability of error in terms of the sum of pairwise errors. This resolves a
conjecture of Audenaert and Mosonyi [J. Math. Phys. 55 (2014)] and improves the multiple
quantum Chernoff bound of Li [Ann. Statist. 44 (2016)] by removing its dimension-dependent prefactor. In the asymptotic many-copy regime, our bound proves the achievability of the multiple
quantum Chernoff distance for arbitrary separable
Hilbert spaces, thereby settling the previously open infinite-dimensional case, and further yields constant-factor sharp asymptotics for the optimal error probability. In binary
quantum hypothesis testing, we prove that the minimum error probability is characterized, up to universal constants, by a trace harmonic-mean quantity. Consequently, the optimal binary
quantum error probability is within a factor of two of the optimal classical error probability for the associated Nussbaum-Szkoła distributions, complementing the lower bound of Nussbaum and Szkoła [Ann. Statist. 37 (2009)].
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Statistical Mechanics · Cross-listed from cs.LG
Generative Criticality in Large Language Model Temperature Scaling
Huajian Ruan, Jinyang Li, Xingyu Guo et al. (+1 more)
We propose a statistical-field framework for text generated by large
language models (LLMs), treating
token embeddings as continuous
spin variables on a one-dimensional chain. Defining a susceptibility from the connected two-point correlator and an order parameter from the ensemble-averaged
embedding field, we vary the softmax temperature $T$ and observe a sharp susceptibility peak near a characteristic $T_c$ with power-law-like scaling, a concurrent rapid change in the order parameter, and a collapse onto a single semantic direction below $T_c$. The intrinsic dimension estimated by the two nearest neighbor (TwoNN) method independently corroborates these findings, reaching a minimum near $T_c$. Results are robust across model scales (Qwen3: 0.6B–32B) and
prompt categories. While the phenomenology closely resembles a continuous phase transition, the non-
equilibrium nature of autoregressive generation warrants further investigation. Our framework provides quantitative tools for probing the collective statistical structure of LLM outputs and suggests connections between decoding strategies and critical phenomena.
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All authors Huajian Ruan, Jinyang Li, Xingyu Guo, Lingxiao Wang
Instrumentation and Methods for Astrophysics
Sensitivity Limits and Operational Threshold Calibration for DINOv2-based Gravitational-Wave Glitch Characterization: A Strain-Domain Mock Data Challenge on LIGO O4a
Luca Cirfeta
We present a Mock Data Challenge (MDC) to characterize the sensitivity limits of the gravi-signal-ml pipeline (Cirfeta 2026) for unsupervised gravitational-wave glitch detection. Strain-domain synthetic injections of eight morphological families into public LIGO O4a L1 data reveal two threshold-dependent sensitivity regimes. With a session-adaptive dynamic threshold (tau_dyn = mu_bg - 2.5 * sigma_bg), the pipeline recovers visually anisotropic morphologies (Butterfly, ZSweep) at matched-filter SNR >= 70, reaching Recall = 1.0, though the False Positive Rate (FPR) remains uncontrolled across sessions. Characterization of the full O4a
embedding distribution (N = 188,142 segments) reveals extreme non-Gaussianity (skewness = -4.12, excess kurtosis = 15.38, Shapiro-Wilk p-value near 0), with the left tail best modeled by a Generalized Extreme Value (GEV) distribution. Under a statistically rigorous operational threshold (tau_op = 0.874) calibrated at the empirical 5x10^-5
quantile (FPR < 0.01%), the MDC yields Recall = 0 for all eight morphologies at all tested SNR levels, including narrowband structures (HarmonicComb, NarrowChirp) and impulsive transients (AsymBlip) at SNR up to 430. We trace this insensitivity to the global average pooling of the DINOv2 [CLS]
token, which dilutes signals occupying a small fraction (<5%) of the spectrogram's 37x37 patch grid. The null result of Cirfeta (2026) is conditionally reinterpreted: it confirms the absence of novel macro-structures but cannot exclude localized micro-structures. These findings provide a quantitative roadmap for next-generation ViT-based pipelines using patch-level scoring and multi-scale windowing.
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Solar and Stellar Astrophysics
gr8stars II : judgement day for spectroscopic parameter model systematics
Alix Violet Freckelton, Annelies Mortier, Megan Bedell et al. (+18 more)
Many areas of astrophysics, including exoplanetary studies, rely on precise and accurate
stellar parameters. This demands that uncertainties on these parameters truly reflect all biases and systematics. Within this second work of the gr8
stars collaboration, we take a set of 585 bright FGK
dwarfs with high resolution, high signal-to-noise ratio spectra from the SOPHIE spectrograph. We determine
stellar effective temperature, surface
gravity, and
metallicity using five different spectroscopic methods for each
star, with an additional method used for comparisons. We find a typical scatter of 76 K in \teff, 0.14 dex in \logg, and 0.07 dex in \feh. These deviations are significantly larger than the average precision error on these parameters. We furthermore use isochrone fitting to determine mass, radius, and age for all 585
stars, using input from all results. We use the radii determined by SED fitting in the first gr8
stars paper as a comparison to our isochronal radii from this work, in addition to comparing the isochronal \logg to spectroscopic \logg. The scatter in mass and radius from the use of different spectroscopic methods is investigated and propagated to exoplanetary parameters. The induced fractional uncertainties in planetary radius ($\lesssim$ 3 %) and mass ($\lesssim$ 5%) are found to be below those typically found in the literature. We estimate a lower limit on planetary
equilibrium temperature fractional uncertainty of $\approx$ 4%, a noise floor that is currently not sufficiently represented in the literature.
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All authors Alix Violet Freckelton, Annelies Mortier, Megan Bedell, Michael Cretignier, Jared R. Kolecki, Andreas J. Korn, Sérgio G. Sousa, Maria Tsantaki, John M. Brewer, Lars A. Buchhave, Guy R. Davies, J. I. González Hernández, Sam Morrell, Martin B. Nielsen, Vera Maria Passegger, Andreas Quirrenbach, Arpita Roy, Nuno C. Santos, A. Suárez Mascareño, Christopher Allan Watson, Lily L. Zhao