Peer Revenue Impact factor: volatile

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics

Watch Physics

Tuesday 14 July

High Energy Physics (Phenomenology)

Naturally quality-safe GeV axion with charm coupling

Bo-Qiang Lu

The GeV-scale QCD axion – where Peccei-Quinn (PQ) symmetry is broken by the QCD condensate at $f_a\sim\mathcal{O}(1)$~GeV – faces a structural isospin problem: the PQ spurion coupling to light quarks ($u,d,s$) breaks $\mathrm{SU}(2)$ isospin, generating an unacceptable $\sim 15\%$ $\pi^0$–$\pi^\pm$ mass splitting. We show that coupling the PQ scalar to the charm quark instead eliminates this violation entirely, and lowering $m_\phi\sim 3$–$4$~MeV makes the charm Yukawa $\kappa_c\propto m_\phi$ perturbative ($\kappa_c<1$). The resulting $f_a\sim\text{GeV}\ll M_{\rm Pl}$ solves the axion quality problem: even the lowest-dimension $d=6$ Planck-suppressed operator gives $m_{\rm PQ}/m_a\sim 10^{-14}$, without any additional symmetry. The model predicts a distinctive negative $\Delta N_{\rm eff}\sim -0.1$ for $m_\phi\sim 3$~MeV, testable by CMB-S4. The $B\to K\sigma$ penguin predicts $\mathrm{BR}\sim 2\times 10^{-5}$, consistent with the Belle~II evidence for $B^+\to K^+\nu\bar{\nu}$ at $(2.3\pm0.7)\times 10^{-5}$~\cite{BelleII:2024knv}. All ten classes of experimental, astrophysical, and cosmological constraints are satisfied in the viable window $m_\phi\sim 3$–$4$~MeV, with the $B_s$ mixing constraint pending a dedicated lattice calculation.
Read the full abstract

Statistical Mechanics

Optimal preparation and reachable-state constraints in the Mpemba effect

C. Ríos-Monje, A. Patrón-Castro, C. A. Plata et al. (+2 more)

The Mpemba effect, whereby an initially hotter system relaxes faster than a colder one towards a common final state, is often analysed within the kinetic framework by assuming non-stationary initial conditions that are selected a priori. Here, we revisit this viewpoint by explicitly incorporating the aging protocol used to prepare those states. Focusing on uniformly heated granular fluids, we formulate the preparation stage as an optimal-control problem in which the energy injection is tuned to generate the initial conditions that maximise or minimise the subsequent relaxation rate. Within the first Sonine approximation, this optimisation reduces to extremising the excess kurtosis of the velocity distribution function, the quantity controlling the cooling rate at fixed temperature. Applying Pontryagin's maximum principle, we show that the optimal preparation protocol is always a one-bang protocol and determine the corresponding extremal values of the excess kurtosis. Most importantly, we find that the stochastic thermostat imposes non-trivial reachable-state constraints: the accessible non-Gaussianities are bounded by those of the homogeneous cooling state, thereby limiting the relaxation-rate asymmetry and the maximum attainable Mpemba effect. These results demonstrate that the strength of the kinetic Mpemba effect cannot be disentangled from the accessibility of the underlying non-equilibrium states. More generally, our work establishes a connection between anomalous relaxation, optimal control, and state accessibility in non-equilibrium systems.
Read the full abstract

All authors C. Ríos-Monje, A. Patrón-Castro, C. A. Plata, B. Sánchez-Rey, A. Prados

Atmospheric and Oceanic Physics

Robustness of Deep Learning Models for PV Power Forecasting under NWP Forecast Errors: A Spatiotemporal and Physically Interpretable Analysis

Dandan Chen, Yan Zhao and Xuepeng Chen

Engineering use of AI forecasting models requires not only high nominal accuracy but also predictable behavior under uncertain inputs. In photovoltaic (PV) forecasting, this requirement is especially challenging because numerical weather prediction (NWP) errors are temporally correlated, state dependent, and physically coupled across variables. Existing evaluations, however, often rely on perfect forecast assumptions or simplistic perturbations that do not reflect these characteristics. This study presents a physically constrained robustness evaluation framework based on simulation, using virtual PV power as a controlled response variable to isolate the propagation of input uncertainty from confounders at the plant level. Six representative machine learning and deep sequence models, including PatchTST, GRU, N-HITS, and LightGBM, are evaluated under dynamic NWP perturbations with heteroscedasticity modulated by clear-sky conditions and Erbs reconstruction that preserves radiation consistency. The results show that sequence models provide stronger noise filtering and temporal resilience than a strong tabular baseline under medium to high disturbance regimes. SHapley Additive exPlanations (SHAP) and Integrated Gradients (IG) further support a feature reallocation tendency at the case level, in which predictive reliance shifts from corrupted future forecasts toward more stable historical observations and deterministic physical priors. A Pareto analysis of accuracy under clean conditions, robustness, and computational latency then translates these findings into engineering implications for robustness assessment and model selection under forecast uncertainty.
Read the full abstract

Instrumentation and Methods for Astrophysics

Fast and accurate bandpass integration of complex SEDs with neural networks

L. A. Bianchi

The paper presents a novel ML-based approach for fast and accurate bandpass integration of spectral energy distributions (SEDs). The non-locality of the integral operator involved guarantees the smoothness of the target function to be approximated, making it an excellent use-case for neural networks. The computational method developed for this work has been wrapped within pyfine (FINE: Fast Function Interpolation via NEural NEtworks). This new Python package makes the relevant code available and easy to use by everyone within the scientific community. The method is demonstrated with two different bandpass integration test cases with 3 and 9 free parameters, respectively, where both accuracy and computational performance are analyzed. The results show that the method is capable of predicting values of the bandpass integral with maximum relative residuals as low as 0.002% and 0.08% respectively, within the sampled region of the parameter space, fast run times, and very little memory overhead. The usage of pyfine is especially effective when the computation of an SED functional form, given a set of values for its free parameters, is expensive. However, already in the first of the two test cases, where a simple modified black body SED was employed, the neural network's measured run times resulted faster by two orders of magnitudes than an optimized multithreaded version of the “brute force” exact calculation of the integral.
Read the full abstract

Astrophysics of Galaxies

SMA Observations of the Archetypal Compact Steep-spectrum Radio Source 3C 303.1

Rushikesh Bhutkar, Mark Gurwell, Christopher O'Dea et al. (+5 more)

AGN (active galactic nuclei) feedback plays a crucial role in shaping galaxy evolution. Numerical simulations show that the kinetic energy transfer efficiency from radio jets to interstellar medium (ISM) is relatively high, suggesting a significant role of radio jets in the feedback. We investigate AGN feedback on cold gas in the compact steep-spectrum (CSS) radio source 3C 303.1. CSS sources are largely young radio galaxies evolving through dense environments of their host galaxies. This early evolutionary phase likely represents a critical stage in which the radio source has maximum impact on host galaxy evolution. 3C 303.1 is the only CSS source so far showing alignment in optical, X-ray and UV with the radio structure, making it an interesting source to investigate jet-feedback. We present continuum and spectral line observations of the J=3-2 transition of carbon monoxide ($^{12}$CO) of 3C 303.1, obtained with the Submillimeter Array. We detect continuum emission at 221.1 and 271.2 GHz. We do not detect the $^{12}$CO(J=3-2) line and derive an upper limit on the molecular gas mass of $\sim 2.3 \times 10^{9}\ \mathrm{M_\odot}$. The gas to-dust mass (G/D) ratio is found to be at the lower end of typical Galactic values, and the star-formation rate (SFR) derived is moderate but declining likely due to a recent quenching event. Therefore, $^{12}$CO(J=3-2) non-detection, relatively low G/D ratio, and the moderate but declining SFR point to the shock-heating and/or removal of CO gas by AGN, consistent with the AGN feedback signatures observed in 3C 303.1.
Read the full abstract

All authors Rushikesh Bhutkar, Mark Gurwell, Christopher O'Dea, Mojegan Azadi, Belinda Wilkes, Stefi Baum, D. J. Saikia, Grant Tremblay

Solar and Stellar Astrophysics

Structure and Dynamics of the Inner Corona Measured from the DEB Initiative 2024 Eclipse Image Sequence

Matthew J Penn, Robert Baer, Chris Mandrell et al. (+66 more)

The Dynamic Eclipse Broadcast (DEB) Initiative citizen science program observed coronal visible continuum brightness during the 2024 April 8 total eclipse from locations across North America. We present results from 11 DEB sites spanning 2700 km of distance and showing 49 minutes of evolution. The coronal brightness radial profiles from these telescopes are tightly correlated from 1.2 to 4.0 solar radii and comparable to published photometric coronal intensities. The coronal flattening parameter is measured from 1.4 to 2.8 solar radii. A Ludendorff index of 0.0761 +/- 0.0007 is computed but the extrapolation techniques used by some to calculate this index are shown to disagree with this direct measurement, and alternate structure parameters are suggested. Measured radial velocities are compared with an MHD model of the corona during the eclipse from Y. Li et al. (2026). A polar downflow is measured with an average radial velocity of -37 +/- 3 km s-1 and a deceleration of 14 +/- 3 m s-2 at a speed and position which agrees with the model. The predicted mixture of outflows and downflows at low heights is seen, as well as outflows in two western regions of the corona. The fastest observed outflow has a radial speed of 105 km s-1 and is likely associated with a transient event not predicted by the model. Future DEB Initiative eclipse experiments can more tightly constrain models of the inner corona by using both coronal intensity and radial velocity measurements.
Read the full abstract

All authors Matthew J Penn, Robert Baer, Chris Mandrell, Corinne Brevik, Castor Fu, Mike Conley, Richard Danley, Harvey Henson, David Iadevaia, Jonathan Mangin, Chris Midden, Brodye Miller, Claude Plymate, Teresa Plymate, Zack Stockbridge, Kevin Rasso, Autumn Awalt, Avery Awalt, Gracie Awalt, Josh Awalt, Lauree Rasso, Mike Chartrand, Noah Lambert, Zoee Rasso, Kevin Cobble, Amelia Menezes, Andrew Yu, Felix Mei, Hanson Du, Ramesh Pattar, Vishrut Kumaran, Robert Auburger, Brian J. Drake, Seth Antozzi, Chloe Rectanus, Grayson Garner, Michael Weiss, Bill Kloepping, Deborah Grubis, Maryanne Angliongto, Ashvik Chilakala, Carl Buz McCullough, Mark Bremer, Christina Adair, Amber Huffman, Charon Adair, Gabbie Graham, Nick Tillerson, Fred Isberner, Candy Isberner, Harry Treece, Lisa Sikorski, Sage Julian-Fralish, Heidi Schran, Addison Greene, Bibodh Baral, Crow Ely, Nolan Hodgson, Olive Blackmar Rice, Olivia Andrews, Olivia Freeman, Quinn Donnelly, Serenity Prince Kirk, Carmen Tran, Brianna Blanchard, Kyan West, Landon Bevier, Murali Saravanan, Jeremy Wright

Fluid Dynamics

A Unified Gradient Theory for Frame-Indifferent Rates of Tensorial Internal Variables

Luis Espath

We develop a thermodynamically consistent framework for weakly nonlocal continua with tensor-valued internal variables. Let $\boldsymbol{L}=\operatorname{grad}\boldsymbol{v}$, with stretching tensor $\boldsymbol{D}=\operatorname{sym}\boldsymbol{L}$ and spin tensor $\boldsymbol{W}=\operatorname{skw}\boldsymbol{L}$. We introduce the generators $\boldsymbol{\Gamma}_{\alpha}=\boldsymbol{W}+\alpha\boldsymbol{D}$, $\alpha\in\{0,1\}$, which unify corotational and upper-convected transport. The resulting kinematic structure induces canonical frame-indifferent evolutions of both the internal variable and its spatial gradient, thereby providing a closure for gradient-dependent theories. Starting from the balances of linear momentum and microforces, together with an internal power expenditure depending on the internal variable and its gradient, we derive a local free-energy imbalance for incompressible isothermal processes. Under isotropy and inherited symmetry assumptions, this imbalance admits a canonical decomposition into contributions associated with $\boldsymbol{D}$, $\operatorname{grad}\boldsymbol{L}$, the generator-induced rate $\mathfrak{D}_{\alpha}\boldsymbol{J}$, and its gradient $\mathfrak{D}^{\nabla}_{\alpha}(\operatorname{grad}\boldsymbol{J})$. This decomposition yields explicit constitutive restrictions ensuring thermodynamic consistency and identifies the induced higher-order stress contributions arising from gradient dependence. Finally, we construct a coupled gradient theory combining viscoelasticity and constrained orientational order, in which distinct internal variables evolve under different transport mechanisms. The framework extends classical theories with tensorial internal variables, including Oldroyd-B and Landau-de Gennes-type models.
Read the full abstract

Quantum Physics

Logical Entangling with Phantom Codes in Hypergraph Products

Keming He, Ziao Tang, Zetong Li et al. (+2 more)

Logical entangling gates are a major source of physical spacetime overhead in fault-tolerant quantum computation. Phantom codes reduce this cost by implementing every ordered in-block logical CNOT through physical qubit permutations and Pauli-frame updates. Whether this mechanism can coexist with the low-weight stabilizer structure of qLDPC codes is a central question for low-overhead fault-tolerant architectures. We give a deterministic answer within binary CSS hypergraph product (HGP) codes. Up to natural equivalences, the simplex-repetition family is the unique HGP family satisfying the phantom condition. We then evaluate this family under circuit-level noise in logical GHZ-state preparation and Trotterized many-body quantum simulation. The codes retain low-weight stabilizer checks and yield concrete advantages over rotated surface-code baselines in both benchmarks. Reconfigurable neutral-atom arrays offer a natural setting for this approach, supporting nonlocal qLDPC operations while enabling in-block logical CNOTs without additional physical operations. Together, these results make precise how permutation-based logical entangling constrains code design within the HGP framework, demonstrate the circuit-level benefits of the unique family, and guide the search for phantom qLDPC families with better asymptotic parameters for low-overhead fault tolerance on neutral-atom hardware.
Read the full abstract

All authors Keming He, Ziao Tang, Zetong Li, Ge Bai, Xin Wang

Quantum Physics

Ancilla-Depth Phase Diagrams for Quantum Reference-Frame Comparison

Maxim V. Churilov

Comparing two noisy quantum reference frames as statistical experiments depends on the dimension of the ancillary memory available to the decision procedure. For finite-dimensional channels A and B with invertible A, we show that exact simulation of all measurements assisted by an r-dimensional ancilla is equivalent to r-positivity of the unique factor Gamma = BA^{-1}. The hierarchy can be realized by physical channel pairs: every unital, trace-preserving map that is k-positive but not (k+1)-positive embeds as the factor between the channels D_a and Gamma composed with D_a on an exact interval determined by the smallest Choi eigenvalue. For depolarizing source and target channels D_a and D_b, including negative and singular source parameters, the phase boundary is $\mathcal{D}_a \succeq_r \mathcal{D}_b \Longleftrightarrow -1/(dr-1) \leq b/a \leq 1$ for $a\neq 0$. We derive closed formulas for the restricted level-r deficiency and for the distance to every physical post-processing, $\delta_{\mathrm{phys}}(\mathcal{D}_b\mid\mathcal{D}_a)=(1-1/d^2)\operatorname{dist}(b,I_a)$, where $I_a=\operatorname{conv}\{a,-a/(d^2-1)\}$. The largest physical conversion cost hidden from all tests through level k is $(d-k)/[d(d^2-1)]$. An untouched m-level spectator changes the first detecting external level from k+1 to $\lfloor k/m\rfloor+1$. A transpose–depolarizing construction shows that the separation is not confined to depolarizing factors. The results quantify the distinction between ancilla-restricted statistical simulation and implementation by a single quantum channel.
Read the full abstract

Fluid Dynamics

Energetics and Stochastics of Extreme Waves Breaking over a Symmetrical Breakwater

Saulo Mendes, Yuchen He, Jérôme Kasparian et al. (+1 more)

Rogue wave formation and enhancement over coastal areas have been documented over the last decade. This seems to contradict the observed low rogue wave (RW) probability near the surf zone. Without considering wave breaking, RW amplification is expected in this regime. To address this gap, we consider fully nonlinear effects of wave breaking through the proxy of height-to-depth ratio, spatial changes on the wavenumber through the WKB approximation, and slope-corrected refraction mild-slope equations on the energetics of irregular wave fields travelling over a breakwater. By increasing the significant wave height towards the breaking limit, the kinetic energy grows faster than the variance of the surface elevation due to nonlinearity. Thus, the kurtosis decays, albeit not to the point of getting sub-Gaussian statistics. We thereby resolve the apparent paradox of the occurrence probability of RW increase at the beginning of shoaling but subsequently decrease when wave breaking becomes dominant. Motivated by these theoretical developments, we experimentally probe inhomogeneous wave fields nearing the wave-breaking regime. We conduct unidirectional irregular wave experiments in a 30 m long wave flume, generating broad-banded waves over a symmetric submerged breakwater featuring a bottom slope of 1/5, allowing detailed characterization of spectral evolution and the persistence of elevated excess kurtosis even near the breaking limit for this steep slope. We thereby confirm that the excess kurtosis can still be large if the bottom slope is steep, and its maximum value is at least 4 times larger than in other ocean processes, occurring atop the breakwater and about half of its deep water peak wavelength distance after the shoal. As these conditions are typical near shorelines, this understanding is key to coastal areas.
Read the full abstract

All authors Saulo Mendes, Yuchen He, Jérôme Kasparian, Amin Chabchoub

Quantum Physics · Cross-listed from math.CO

Large sets of mutually orthogonal quantum Latin squares

Simeon Ball and Robin Simoens

How large can a set of mutually orthogonal quantum Latin squares (MOQLS) get? We show that a set of n - 2 MOQLS of order n is necessarily classical and construct large non-classical sets of MOQLS of orders that are prime powers, improving both the previously known lower and upper bounds.
Read the full abstract

Chemical Physics

Measurement and assignment of $\it{J}$ $\geq$ 10 rotational energy levels in the 9510 to 9810 cm$^{-1}$ and 6590 to 6900 cm$^{-1}$ ranges of methane using optical frequency comb double-resonance spectroscopy

Yuan Cao, Adrian Hjältén, Vinicius Silva de Oliveira et al. (+4 more)

Accurate models of high temperature methane spectra are needed in astrophysics. Previous measurements of methane hot-band transitions in the $\it{P}$6 $\leftarrow$ $\it{P}$2 polyad range have been limited to final rotational numbers of $\it{J}$ $\le$ 9, with theoretical predictions at higher $\it{J}$s remaining unvalidated. Here, we use optical-optical double resonance spectroscopy (OODR) with a 3.3 ${\mu}$m narrow linewidth pump to excite the ${\nu}$${_3}$ P(12, A${_1}$$^{(2)}$) methane transition ($\it{P}$2 $\leftarrow$ $\it{P}$0) and a cavity-enhanced frequency comb centered around 1.68 ${\mu}$m to probe the sub-Doppler ladder-type ($\it{P}$6 $\leftarrow$ $\it{P}$2) and V-type ($\it{P}$4 $\leftarrow$ $\it{P}$0) transitions, as well as Doppler-broadened collision-induced four-level transitions ($\it{P}$6 $\leftarrow$ $\it{P}$2). 49 ladder-type transitions with final rotational states $\it{J}$ = 10-12 in the range of 9510 to 9810 cm$^{-1}$ (i.e., the $\it{P}$6 polyad) were assigned to effective Hamiltonian predictions and the ExoMol database, of which 6 reached vibrational states that had not been observed experimentally before. 19 sub-Doppler V-type transitions with final states $\it{J}$ = 11-13 in the range of 6590 to 6900 cm$^{-1}$ (i.e., the $\it{P}$4 polyad) were observed and assigned to the Hamiltonian and ExoMol, while only 2 of these V-type transitions could be unambiguously assigned to WKLMC and HITRAN line lists. 170 Doppler-broadened four-level double-resonance (4LDR) lines were observed, 7 of which were newly observed compared with our previous work when pumping transitions starting from the $\it{J}$ = 7 level in the ground state [Lehmann et al., J. Chem. Phys. 163, 144304 (2025)]. We could not assign these lines as they did not form combination differences with other observed 4LDR transitions.
Read the full abstract

All authors Yuan Cao, Adrian Hjältén, Vinicius Silva de Oliveira, Isak Silander, Michael Rey, Kevin K. Lehmann, Aleksandra Foltynowicz

Astrophysics of Galaxies

The MAGPI survey: Stellar population radial trends and mass assembly in star-forming galaxies at z~0.3

Federica Mauro, Bodo Ziegler, Iris Breda et al. (+19 more)

The evolution of galaxies from cosmic noon to the present day provides a key window to probe the balance between early, rapid bulge formation and prolonged disk growth. The epoch at $z \sim 0.3$ marks a crucial transitional phase between the peak of cosmic star formation and the predominantly quiescent local Universe. In this work, we examine the spatially resolved stellar populations of 34 galaxies at $z \sim 0.3$ to quantify radial gradients in age, stellar metallicity, and star formation activity, and disentangle the distinct evolutionary pathways of inner and outer galactic components. We utilise MUSE integral-field spectroscopy data cubes from the MAGPI survey at redshifts of $0.28 < z < 0.35$. Stellar population properties are derived using the spectral synthesis codes FADO and Starlight, and radial profiles are constructed by fitting isophotal annuli to the galaxy continuum emission. We further reconstruct star formation histories and cumulative mass assembly curves for inner and outer regions. We find pronounced negative radial gradients in age and negative to flat gradients in stellar metallicity. Inner regions are systematically older and more metal-rich than their surrounding outskirts, with age differences up to 3-4 Gyr in the most massive systems. H$\alpha$ equivalent width profiles reveal centrally suppressed specific star formation in most galaxies. Star formation histories and mass assembly curves demonstrate that galaxy cores formed $80\%$ of their stellar mass rapidly, within the first 2-3 Gyr of cosmic time; while areas outside $\mathrm{1\,R_{eff}}$ assembled more gradually and sustained star formation to later epochs. Outskirts evolve primarily through extended, secular star formation, establishing the centrally concentrated quenching and inside-out growth that link high-redshift systems to the quiescent galaxies of the local Universe.
Read the full abstract

All authors Federica Mauro, Bodo Ziegler, Iris Breda, Polychronis Papaderos, Gauri Sharma, Sabine Thater, Katherine E. Harborne, Trevor Mendel, Emily Wisnioski, Claudia Lagos, Caroline Foster, Andrew J. Battisti, Ryan S. Bagge, Joss Bland-Hawthorn, Scott Croom, Siddhartha Gurung-López, Marcie Mun, Tamal Mukherjee, Sarah M. Sweet, Lucas M. Valenzuela, Glenn van de Ven, Tayyaba Zafar

Fluid Dynamics

Mixing and sharpening at the interface of a two-layer fluid forced by random jets

Noé Clavier, Hugo Pradel, Romain Volk et al. (+2 more)

Understanding mixing at density interfaces is essential for predicting transport in stratified environmental flows. Laboratory studies have mostly relied on steady, spatially uniform forcing, whereas turbulence in nature is intermittent and heterogeneous. Here, we present experiments on a two-layer salt-stratified fluid forced by random turbulent bursts generated with a randomly actuated synthetic jet array (RASJA). Density fields are recorded with the light attenuation technique, allowing us to resolve the interface evolution. We measure that the upward velocity of the interface decreases with the density jump, in agreement with the power-law found in previous oscillating-grid studies. At large density differences, the interface sharpens during mixing, contrary to the smaller density jump case. Background potential energy analysis demonstrates irreversible mixing in both cases, with comparable energy changes. These results extend classical laboratory observations to a more isotropic forcing, offering new insights into the dynamics of mixing in geophysical settings.
Read the full abstract

All authors Noé Clavier, Hugo Pradel, Romain Volk, Mickaël Bourgoin, Yvan Dossmann

Statistical Mechanics

Coherent Bose-Einstein condensation with fluctuating density

L. Salasnich, A. Crisanti, A. Sarracino et al. (+1 more)

Bose-Einstein condensation in the grand canonical ensemble admits a formulation in terms of a phase-density decomposition of the condensate mode operator $\hat{\psi}_{\bf 0}$. In the presence of macroscopic condensate number fluctuations this representation presents nontrivial implications. In particular, we show that, for the ideal gas, under the assumption of a well-defined phase and a fluctuating condensate density, the square modulus of the anomalous average $\langle \hat{\psi}_{\bf 0}\rangle$ can provide only a fraction of the whole condensate density $\rho_{\bf 0}$ and for the grand canonical statistics of the ideal Bose gas one obtains the value $|\langle {\hat \psi}_{\bf 0}\rangle|^2 =(\pi/4) \rho_{\bf 0}$. The remaining part is supplemented by the (macroscopic) fluctuations of $\hat{\psi}_{\bf 0}$, which become a distinctive feature of the BEC in this setting. This provides a transparent physical picture of a condensate of photons with a well-defined phase but large number fluctuations, as observed in dye-filled microcavity photon experiments. We also propose a way to access the square modulus of the anomalous average to test theoretical predictions.
Read the full abstract

All authors L. Salasnich, A. Crisanti, A. Sarracino, M. Zannetti

Strongly Correlated Electrons

Microscopic Spin-1 Parent Hamiltonians for Emergent Valence-Bond Loop Manifolds

Hari Borutta, Yasir Iqbal and Kirill Shtengel

We construct an exact spin-$1$ parent Hamiltonian for constrained valence-bond loop manifolds on the checkerboard and pyrochlore lattices. The Hamiltonian is local, SU(2)- and time-reversal-invariant, and built from positive-semidefinite projectors acting on triangular faces. Each projector removes only the maximally polarized state of a triangle, so the model is frustration-free. Its zero-energy states are generated by an AKLT-like construction in which each spin-$1$ moment is resolved into two virtual spin-$\tfrac12$ degrees of freedom, singlets are formed inside every crossed plaquette or tetrahedron, and the physical spin-$1$ Hilbert space is recovered by projection. The resulting ground states are fully packed singlet-loop states on the corner-sharing lattice. Thus, a loop or dimer constraint, usually introduced as part of an effective Rokhsar–Kivelson description, appears here as the exact zero-energy manifold of a microscopic spin Hamiltonian. We analyze spin correlations within this manifold and show that, for a fixed loop covering, they are determined by loop connectivity. We also project symmetry-allowed perturbations into the ground-state manifold and derive the resulting low-energy pseudospin dynamics. The checkerboard and pyrochlore cases differ sharply. On the pyrochlore lattice, tetrahedral symmetry removes simple local bias terms, and the leading nontrivial next-nearest-neighbour Heisenberg perturbation gives an emergent spin-$\tfrac12$ XY model on the diamond lattice of tetrahedron centers. These results give an exact spin-$1$ microscopic starting point for constrained valence-bond physics in two and three dimensions, and show how loop, dimer, and gauge-theoretic descriptions can be approached from a small-spin, SU(2)-invariant frustrated magnet.
Read the full abstract

High Energy Physics (Theory)

Holography from number theory: Emergent holographic AdS$_2$ space-time from exact BPS black hole microstate counting

Gabriel Lopes Cardoso and Suresh Nampuri

In this note, starting from the exact counting formulae for 4D BPS black hole degeneracies in the cases of 1/2 BPS $\mathcal{N}=4$ and 1/8 BPS $\mathcal{N}=8$ solutions, expressed as Rademacher expansions for coefficients of modular and Jacobi forms respectively, we explicitly show how the number theoretic data in each Rademacher summand is encoded by a Segal-Bargmann heat kernel calculation in the de Alfaro-Fubini-Furlan (DFF) model of conformal quantum mechanics, thus demonstrating the holographic origin of the BPS Bekenstein-Hawking entropy, and all logarithmic and power law suppressed corrections to it. We then derive the 2D holographically dual bulk space-time for this CQM and show that it is an AdS$_2$ space-time with radial length scale correlated to the energy scale of the DFF model. We further show how the Bekenstein-Hawking entropy emerges from an entanglement entropy computation in this bulk space-time. Hence, for the two classes of 4D BPS black holes under consideration, we have inferred the holographic CQM relevant for microscopic state counting from the exact number-theoretic degeneracy formulae and demonstrated the emergence of the near-horizon AdS$_2$ attractor geometry that is holographically dual to it.
Read the full abstract

Physics and Society

Balancing innovation and assimilation in research communities

Bill Nunn, Maria Horner, Marcel Ortgiese et al. (+1 more)

It has been statistically observed that the speed at which a corpus of knowledge advances does not scale linearly with quantities like the number of active researchers or number of research papers published in a given field. Furthermore, as a body of knowledge grows, individual researchers must somehow strike the right balance between generating new knowledge through innovation and assimilating knowledge generated by others. Here, we propose and analyse a pair of interacting particle system models representing some stylised features of the advancement of knowledge in a research community, captured as a stochastic travelling wave in knowledge space. Both particle systems exhibit a diminishing return in the knowledge advancement speed as research communities grow larger, and suggest that researchers should spend more time on assimilation of knowledge than innovation as their research community grows.
Read the full abstract

All authors Bill Nunn, Maria Horner, Marcel Ortgiese, Tim Rogers

High Energy Physics (Phenomenology)

Hadronic vacuum polarization contribution to $a_\mu$ from functional methods with strong and electromagnetic isospin breaking

Angel S. Miramontes, Adnan Bashir, Christian S. Fischer et al. (+1 more)

We present a continuum-QCD determination of the leading-order hadronic vacuum-polarization contribution to the anomalous magnetic moment of the muon within the Dyson-Schwinger and Bethe-Salpeter equation framework. The calculation incorporates pion back-reaction, a fully dressed quark-photon vertex with a dynamically generated $\rho$-resonance structure in the timelike region, and both strong and electromagnetic isospin breaking treated self-consistently at the quark level. We obtain $a_\mu^{\mathrm{HVP,LO}}(u+d+s+c)|_{\mathrm{ISB}} = 709.7 \times 10^{-10}$, in good agreement with recent lattice-QCD determinations, and find an isospin-breaking shift of $\Delta a_\mu^{\mathrm{HVP,LO}} = 4.5 \times 10^{-10}$ ($0.6\%$), demonstrating that isospin-breaking effects, while quantitatively modest, are not negligible. Including the bottom-quark contribution and an indicative estimate of the systematic uncertainties, we obtain our final result, $a_\mu^{\mathrm{HVP,LO}}(u+d+s+c+b)|_{\mathrm{ISB}} = (710.0 \pm 14.5) \times 10^{-10}$.
Read the full abstract

All authors Angel S. Miramontes, Adnan Bashir, Christian S. Fischer, Pablo Roig

Quantum Physics

Heisenberg-limited metrology in the presence of non-Markovian noise with finite control rates

Shravan Shravan and Tyler G. Thurtell

Recently, it has been shown that protocols utilizing infinitely fast controls, such as quantum error correction, can in principle restore Heisenberg-limited frequency estimation in the presence of a broad class of non-Markovian noise models arising from coupling to finite-dimensional environments. However, these controls differ substantially from those used to address Markovian noise, and their underlying physical mechanism remains unclear. In this work, we establish a direct connection between these protocols and the quantum Zeno effect, and extend the framework to infinite-dimensional environments. We delineate three types of constructions: (a) protocols that rely solely on measurements, (b) protocols using an active recovery after measurements and (c) protocols using dynamical decoupling and rigorously analyze the performance of each when controls can be applied at only a finite rate. While protocols relying purely on measurements can be engineered for noise models where active recoveries are fundamentally impossible, they result in the quantum Fisher information exhibiting a quadratically worse dependence on the control frequency. Surprisingly, while dynamical decoupling protocols are possible whenever protocols relying only on measurements can be engineered, the quantum Fisher information has the same dependence on control frequency as the active recovery protocols. Numerical simulations suggest that the improvement offered by dynamical decoupling may work in regimes beyond the perturbative setting where our rigorous theorems apply.
Read the full abstract

Mathematical Physics · Cross-listed from math.AG

Obstructions to Deformation Quantization of Bundles

Vladimir Baranovsky and Greg Huey

Let $\left(M, \mathcal{O}_M \right)$ be a smooth algebraic variety over field $\kappa$ of characteristic $0$ with an algebraic symplectic form $\omega$, or a complex manifold with a holomorphic form $\omega$. Furthermore, let $E$ be a vector bundle over $\left(M, \mathcal{O}_M \right)$ and $\mathcal{O}_{\hbar}$ a deformation quantization of $\mathcal{O}_M$ compatible with $\omega$. Assuming that $E$ possesses a deformation quantization to order $\hbar^k$ we consider the problem of extending it to order $\hbar^\ell$ for $\ell > k$, and establish triviality of an obstruction class as a necessary condition for this extension to exist. Furthermore, in the case $\ell \le 2k+1$, we prove that this condition is also sufficient.
Read the full abstract

Instrumentation and Methods for Astrophysics

Updates to the WFC3/IR Photometric Stability Stellar Cluster Study

Ky Huynh and Varun Bajaj

The WFC3/IR channel has been shown to lose sensitivity over time. The sensitivity loss rate has been quantified in past works and we extend those measurements into 2026 using photometry of uncrowded regions of star clusters 47 Tucanae and Messier 4 in the F110W and F160W filters. This study adds 4-7 additional visits since Bajaj et al. (2022) for each target/filter combination. Using F160W data of 47Tuc, we find that the IR channel continues to lose sensitivity at a rate of -0.07% $\pm$ 0.01% per year using the full dataset, and -0.06% $\pm$ 0.02% per year using only the first exposure of every visit. Using M4 data observed in F110W, we find a sensitivity loss rate of -0.13% $\pm$ 0.02% per year using the full dataset, and -0.07% $\pm$ 0.03% per year using just the first exposure of every visit. We find that the rate of sensitivity loss has decreased since the previous study. This likely stems from the inclusion of more recent visits that were designed to mitigate persistence effects. These results suggest that earlier observations, which were not intended for sensitivity measurements, may have overestimated the IR channel's sensitivity due to the effects of persistence from bright sources. The IMPHTTAB reference file that contains the correction to the time-dependent sensitivity remains unchanged from the sensitivity measurements of this report.
Read the full abstract

Quantum Physics

Unitary Synthesis with Near-Optimal T-Count for Near-Clifford Unitaries

Wang Fang, Chris Heunen and Qisheng Wang

We present an approach to unitary synthesis that implements an arbitrary $n$-qubit unitary operator $U$ by a Clifford+T circuit with T-count $\widetilde{O}(2^n d_F^{\mathcal{C}}(U))$, where $d_F^{\mathcal{C}}(U)$ is the Frobenius norm distance of $U$ to the Clifford group. The T-count is shown to be near-optimal when $d_F^{\mathcal{C}}(U)$ is a constant. Our approach improves the previous best upper bound $\widetilde{O}(2^{4n/3})$ due to Tan (2025) for a large class of unitary operators $U$ as long as $d_F^{\mathcal{C}}(U) \ll 2^{n/3}$.
Read the full abstract

High Energy Physics (Theory)

Thermodynamic scaling and string dynamics in rotating holographic QCD

Leila Shahkarami and Farid Charmchi

We investigate the effect of finite angular velocity on the phase structure and Schwinger pair production in a holographic QCD model based on the Einstein–Maxwell–dilaton framework. Rotation is introduced through a boost construction that generates a stationary rotating geometry from the corresponding static background. We first study the thermodynamic phase diagram using the grand potential together with several response functions and show that all thermodynamic phase boundaries satisfy an exact scaling relation under rotation, implying that the rotating thermodynamic sector is completely determined by the corresponding static solution through a simple boost transformation. We then investigate confinement through the effective string tension and find that, consistent with the thermodynamic observables, rotation decreases the string confinement–deconfinement transition temperature and chemical potential. The corresponding phase boundary, however, no longer obeys the thermodynamic scaling relation. Consequently, the region in the phase diagram that is thermodynamically confined but string deconfined grows with angular velocity. We further study the Schwinger effect using the potential analysis approach. Rotation lowers both the confining and catastrophic critical electric fields and suppresses the height and width of the potential barrier, thereby enhancing pair production in both confined and deconfined phases. In the deconfined phase, rotation also generates a worldsheet horizon that limits the radial extent of connected string solutions and reduces both the maximum quark–antiquark separation and the deepest turning point of the energetically favored string. These results demonstrate that, while rotation acts trivially in the thermodynamic sector through an exact scaling law, it produces genuinely new effects in the string sector.
Read the full abstract

Plasma Physics

A new model for runaway electron transport based on chaotic Hamiltonian systems

Dániel Jánosi, Anikó Horváth, Hannes Bergström et al. (+5 more)

The transport of runaway electrons (RE) in ergodic magnetic geometries is an area of active study. Computing the transport from the direct simulation of particle trajectories is computationally expensive. Instead, diffusion models, such as the one by Rechester and Rosenbluth, are often employed to incorporate transport effects into reduced simulations. However, the comparison of diffusion-based to direct simulations reveals that the transport is typically not purely diffusive. In this paper, we introduce a simple transport model, based on chaos theory, which goes beyond the Rechester-Rosenbluth approximation. Besides chaotic diffusion, our model takes into account the effect of so-called sticky regions, a trapping layer around magnetic islands, where particle escape slows down to a power-law decay rather than an exponential decay. We demonstrate the applicability of the model both in the Ullmann-Caldas map with parameters corresponding to the TBR-1 tokamak, and in a JOREK simulation of a JET disruption scenario, with remarkably good fits achieved in both cases.
Read the full abstract

All authors Dániel Jánosi, Anikó Horváth, Hannes Bergström, Matthias Hölzl, Gergely Papp, Gábor Veres, Gergo I. Pokol, György Károlyi

High Energy Astrophysical Phenomena

Investigating the Periodic X-ray Behaviour in the Eclipsing AGN NGC 6814

T. O. Hodd, L. C. Gallo, A. G. Gonzalez et al. (+2 more)

A 2016 XMM-Newton X-ray light curve of the Seyfert 1.5 galaxy NGC 6814 exhibited clear eclipsing behaviour, with distinct ingress and egress, during half of the observation. Here, we report on the periodic behaviour in the light curve prior to the eclipse. We use timing and spectral analysis techniques to quantify the behaviour and examine the characteristics of the periodic signal. A superlet transform of the X-ray light curve reveals a period of ~45-50 $\mu$Hz in the initial 60 ks of the observation with a detection significance at the >90% level in both the broad (0.3-10 keV) and soft (0.3-1.0 keV) bands. The period is confirmed by fitting a sinusoid, and is also evident in the highest energy bands with diminished significance because of reduced signal-to-noise. There appear to be distinct changes in the variability behaviour during the eclipse as the measured period is modulated (stretched) at all energies. From phase-resolved spectra, we investigate possible physical causes of this periodic behaviour and find that it can be interpreted as changes in the covering fraction or a non-standard inner accretion flow (e.g. truncated disc and misaligned flow). The non-standard inner flow appears consistent with previous reports of a truncated inner disc and compact corona in NGC 6814.
Read the full abstract

All authors T. O. Hodd, L. C. Gallo, A. G. Gonzalez, J. M. Miller, D. Rogantini

Instrumentation and Methods for Astrophysics

Establishing baseline model performances for optical turbulence forecasting

M. De Sepibus, E. Masciadri, C. Weinberger et al. (+2 more)

Accurate optical turbulence (OT) forecasts help telescopes observe with maximum efficiency, as the performance of adaptive optics (AO) systems strongly depends on turbulence conditions. OT forecasting remains a challenging problem. A wide range of methods has been explored to address this problem, including numerical weather prediction (NWP) models, machine learning algorithms, and hybrid approaches, each varying in complexity, computational cost, and accuracy. Assessing the performance of forecasting methods is essential to benchmark them against simple, well-defined reference models, known as baselines, which establish reference thresholds. This paper aims to calculate these thresholds for the astroclimatic and atmospheric parameters most relevant for ground-based astronomy related to two of these baseline methods that are suitable for use in two different types of forecast, which are among the most relevant for application to the ground-based astronomy: the forecast of the average of a parameter on a defined timescale and the forecast of the temporal evolution of a parameter on a defined timescale. We apply these baseline methods to a dataset related to a rich statistical sample of many years encompassing key astroclimatic and atmospheric parameters above the sites of the Very Large Telescope and the Large Binocular Telescope, and we discuss the implications of these results and the possibility of extrapolating such values for general rules. We demonstrate that the predictive performance of each reference method depends on the observing sites, the parameter that is forecasted, the forecast timescale, and the type of forecast used. That means that it is meaningless to quantify the performance of OT forecasts in absolute terms, since they depend on the context.
Read the full abstract

All authors M. De Sepibus, E. Masciadri, C. Weinberger, C. Veillet, S. Ragland

Instrumentation and Methods for Astrophysics

Astra: an open-source fully autonomous robotic observatory control software

Peter P. Pedersen, David Degen, Lionel Garcia et al. (+12 more)

Robotic and autonomous observatories are critical for modern time-domain and high-cadence astronomical surveys. The operation of these facilities requires complex software coordination to manage hardware, schedule observations, and ensure safety. However, existing observatory control software are often proprietary and platform-locked or require complex message-brokering infrastructure. Here we present Astra (Automated Survey observaTory Robotised with Alpaca): an open-source, cross-platform Python system for the sustained, fully autonomous operation of astronomical observatories, requiring no external message-broker infrastructure. Astra controls observatory hardware via the ASCOM Alpaca protocol, and executes prescheduled observatory actions under continuous safety supervision. Its multi-device actions include plate-solve-based pointing correction with a local Gaia–2MASS catalogue fallback, PID-controlled autoguiding, and autofocus. A FastAPI web service provides a browser UI, REST and WebSocket APIs for real-time status, image previews, and SQLite-backed telemetry and logs. Astra has run in fully unattended production since January 2024, scaling to six telescopes across three facilities: the SPECULOOS-South network (4 $\times$ 1\,m class, Chile), SAINT-EX (1\,m class, Mexico), and the ETH Observatory (0.5\,m class, Switzerland), with no schedule aborts attributable to Astra software. Across the SPECULOOS-South network, it achieves sub-arcsecond autoguiding (0.11\unit{\arcsecond} median pointing scatter) and plate-solve failure rates below 1% on three of the four telescopes (3% on the narrowest-field unit), demonstrating that an open, standards-based software stack can meet the reliability demands of production survey astronomy.
Read the full abstract

All authors Peter P. Pedersen, David Degen, Lionel Garcia, Urs Schroffenegger, Daniel Sebastian, Sebastián Zúñiga-Fernández, Brice-Olivier Demory, Elsa Ducrot, Michaël Gillon, Matthew J. Hooton, Clàudia Janó-Muñoz, James McCormac, Mathilde Timmermans, Amaury H.M.J. Triaud, Didier Queloz

High Energy Astrophysical Phenomena

Momentum Space Resolution Dependence in Boltzmann Neutrino Radiation Hydrodynamics Simulations of Core-collapse Supernovae

Ryuichiro Akaho

Finite momentum space resolution is a primary source of uncertainty in solving the Boltzmann equation with the discrete-ordinates method. In this paper, the momentum space resolution dependence of Boltzmann neutrino transport is studied by performing a series of two-dimensional core-collapse supernova (CCSN) simulations. The effects on the explosion dynamics are discussed by individually varying the resolutions of the zenith and azimuth angles in momentum space, and of the energy. It is found that a coarse zenith angle resolution artificially facilitates the explosion, even turning non-exploding models into exploding ones. This is because the coarse zenith angle grid cannot capture the forward-peaked distribution, thereby underestimating the flux factor and making neutrinos stay in the gain region for a longer time. The dependence on the azimuth angle resolution is found to have little effect for the present non-rotating models, which is understandable given the sphericity of the CCSN core. In contrast to the zenith angle resolution, a coarse energy resolution is found to artificially suppress the explosion. This is because the neutrino heating rate at intermediate energies ($\sim30$–$50\,\mathrm{MeV}$) is underestimated in the low-resolution case. Finally, the resolution dependence is studied for a one-dimensional black hole (BH) forming model. Unlike the explosion dynamics, BH formation does not exhibit a strong angular dependence. On the other hand, a coarse energy resolution is found to delay the BH formation time. This is because the momentum feedback is overestimated at low resolution, which allows a more massive neutron star to be supported.
Read the full abstract

Cosmology and Nongalactic Astrophysics

Overview: Cosmology with the SKAO

Marta Spinelli, Ian Harrison, Richard A. Battye et al. (+5 more)

The SKA telescopes will revolutionise our ability to do cosmology at radio wavelengths, via both their own data and in synergy with other wavelengths. SKAO will be the first instrument able to conduct large-scale cosmological surveys as done in the last decades in the optical and near-infrared. This complementarity will be vital as cosmology hits the limit of systematic uncertainties. Radio cosmology surveys will have radically different systematics, allowing data combinations across surveys to calibrate systematics and increase overall constraining power. Neutral hydrogen (HI) intensity mapping surveys are now reaching maturity, as demonstrated by the progress made by the MeerKLASS survey with MeerKAT. Along with continuum galaxy surveys, they will provide detailed maps of the Universe covering large fractions of the sky, allowing us to answer questions about fundamental physics which can only be measured on the largest scales. In combination with weak lensing and HI galaxy probes, HI intensity maps will also measure the distributions of matter and velocities to give precisions tests of the $\Lambda$CDM model, including its foundational assumptions of isotropy and homogeneity. In combination with gravitational wave observations and fast radio bursts, they will also help us measure the expansion history and baryon content of the Universe. Here we provide an overview of the achievements of precursor surveys and the progress towards SKA cosmology, starting with AA* and reaching full maturity with AA4 telescopes.
Read the full abstract

All authors Marta Spinelli, Ian Harrison, Richard A. Battye, Stefano Camera, Xuelei Chen, Roy Maartens, Mario G. Santos, Laura Wolz