Physics and Society
Methodological guidelines for circadian modeling of Daylight Saving Time: application to the United States
Jose Maria Martin-Olalla and Jorge Mira
Modeling the circadian impact of seasonal clock changing requires precise synchronization between
solar and social time. This report critiques a recent study that associated disease prevalence in the United States with seasonal clock exposure. We identify a fundamental computational error in which a sign reversal of the longitudinal offset effectively inverted the US East-West axis, cross-correlating local health data with the circadian burden of hypothetical locations on the opposite side of a time zone. We outline the methodology for a correct modelization of the circadian process in the context of US geography.
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Solar and Stellar Astrophysics
Review of Machine Learning Models for Solar Energetic Particle Prediction
Spiridon Kasapis, Pouya Hosseinzadeh, Kathryn Whitman et al. (+73 more)
Solar energetic particle (SEP) events have attracted increasing
attention due to their significant radiation hazards for aviation, spacecraft electronics, and human missions beyond Earth's magnetosphere. From a scientific perspective, SEP events are intriguing because they arise from a set of physical processes extending from the
solar surface and corona through the heliosphere, offering insight into particle acceleration and transport mechanisms that are widely applicable across astrophysics. Therefore, advancing our ability to understand and predict SEP events is essential both for deepening our knowledge of such mechanisms and for safeguarding space technologies and exploration. Traditionally, researchers have modeled SEPs using physics-based simulations and empirical methods. More recently, machine learning (ML) has emerged as a new tool for understanding and predicting SEP events. The purpose of this manuscript is to review the currently available ML models for SEP prediction, identify the
datasets used for training, compare their architectures, inputs, and outputs, and, based on these insights, outline good practices and recommendations for future research.
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All authors Spiridon Kasapis, Pouya Hosseinzadeh, Kathryn Whitman, Ricky Egeland, Manolis Georgoulis, Angelos Vourlidas, Athanasios Papaioannou, Eleni Lavasa, Anastasios Anastasiadis, Giorgos Giannopoulos, Andres Munoz-Jaramillo, Bala Poduval, Irina N. Kitiashvili, Alexander G. Kosovichev, Viacheslav Sadykov, Soukaina Filali Boubrahimi, Tate T. Hutchins, Hameedullah A. Farooki, Manuel E. Cuesta, Leng Y. Khoo, Sungmin Pak, Robert Czarnota, Jamie S. Rankin, Jamey Szalay, Mitchell M. Shen, Georgios Livadiotis, Zigong Xu, David J. McComas, Nikolaos Sarlis, Dionissios Hristopulos, Arik Posner, Alec J. Engell, Mohammed AbuBakr Ali, Ali G. A. Abdelkawy, Abdelrazek M. K. Shaltout, M. M. Beheary, Christina O. Lee, Sigiava Aminalragia-Giamini, Constantinos Papadimitriou, Ingmar Sandberg, Savvas Raptis, Shah Muhammad Hamdi, Monica Laurenza, Mirko Stumpo, Sumanth A. Rotti, India Jackson, Aatiya Ali, Atilim Gunes Baydin, Nathan Schwadron, Subhamoy Chatterjee, Maher A. Dayeh, Gelu M. Nita, Patrick M. O'Keefe, Chun Jie Chong, Paul Kosovich, Russell D. Marroquin, Berkay Aydin, Petrus C. Martens, Lulu Zhao, Yang Chen, Yian Yu, Monica G. Bobra, Ward Manchester, Tamas Gombosi, Ming Zhang, Jesse Torres, Philip K. Chan, Mohamed Nedal, Kamen Kozarev, Peijin Zhang, Kimberly Moreland, Hazel M. Bain, Samuel Hart, Michael J. Starkey, Alan G. Ling, Simone Benella
Physics Education
Vistas: A Visualization Interface for Particle Collision Simulations
Benoit Assi, Christan Bierlich, Rikab Gambhir et al. (+7 more)
We introduce Vistas, a tool for visualizing high-energy particle physics collisions simulated by the Pythia Monte-Carlo event generator. Vistas utilizes the browser-based event display framework Phoenix to show distinct computational stages of a high-energy collision event simulation: the hard process, parton shower, hadronization, and particle decays. Particles produced from each of these stages are represented as lines in an interactive three-dimensional graph structure, where each line is along the direction of its particle's three-momentum vector. The event can be rotated, translated and zoomed, and details for each particle can be accessed by selecting the relevant particle line. Additionally, particle lines from all stages of the simulation can be toggled on and off and can be filtered by particle-level kinematic selection requirements. This interactive environment provides an intuitive interpretation of Pythia simulation output, including detailed features such as color flow, beam remnants, and multiple parton interactions, making it a useful tool in physics education settings, from outreach activities to graduate particle-physics courses.
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All authors Benoit Assi, Christan Bierlich, Rikab Gambhir, Philip Ilten, Tony Menzo, Stephen Mrenna, Manuel Szewc, Michael K. Wilkinson, Ahmed Youssef, Jure Zupan
Plasma Physics
Bayesian optimization of stellarator alpha-particle confinement using data-informed parameter spaces and dimensionality reduction
Matt Landreman, Michael Czekanski, Andrew Giuliani et al. (+2 more)
Modern stellarators are typically designed by optimizing the shape of the
plasma boundary surface, with the parameters taken to be
Fourier amplitudes. Many promising optimization
algorithms such as
Bayesian methods require bound constraints on the parameters and are most efficient when each parameter is scaled similarly to the others. With the typical
Fourier parameterization, it is unclear how to set these bounds: wide constraints lead to self-intersecting boundaries and frequent failures of the MHD
equilibrium calculation, while tight bound constraints limit expressiveness. To address these issues, here we propose two new parameter spaces for stellarator optimization. Both begin with a
dataset of existing stellarator boundaries. In the first approach, a
quantile transformation is applied to each
Fourier degree of freedom, mapping the data distribution to a uniform distribution on the unit interval. In the second approach, principal component analysis (PCA) is applied to points on the boundaries, followed by a
quantile transformation. For both approaches, the transformed variables become the degrees of freedom, naturally bounded to [0, 1]. The PCA method has the additional benefit of dimensionality reduction, with high expressiveness for a small number of parameters. The methods are demonstrated via
Bayesian optimization for good alpha-particle confinement with guiding-center tracing inside the optimization loop, using asynchronous parallelization. These optimizations yield stellarator configurations with excellent fast-particle confinement in fields that can be far from quasisymmetric or quasi-isodynamic.
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All authors Matt Landreman, Michael Czekanski, Andrew Giuliani, Byoungchan Jang, Rory Conlin
Cosmology and Nongalactic Astrophysics
Increasing the sensitivity of full-shape galaxy clustering measurements in configuration-space with three-point statistics
Zachery Brown and Lado Samushia
We investigate the cosmological constraining power of a compressed line of sight dependent three point correlation function (3PCF)
estimator on small scales (<80 Mpc/h) in configuration space, with a particular focus on emission line
galaxies (ELGs) targeted by the Nancy Grace Roman Space
Telescope's
Galaxy Redshift Survey (GRS), and complementary luminous red
galaxy (LRG) samples observed by the Dark Energy Spectroscopic Instrument (DESI). These scales avoid the
baryon acoustic oscillation (BAO) feature and are therefore expected to provide information that is largely complementary to standard BAO measurements, while retaining partial overlap with full shape clustering analyses. Our forecasts are based on AbacusSummit simulations at z = 1.1 and z = 0.8, populated with
galaxies using
halo occupation distribution (HOD) models matched to Roman ELG and DESI LRG samples respectively. The three point measurements are computed with TriCo, a fast configuration space triangle counting code developed for this analysis. After marginalizing over uncertainties in the
galaxy halo connection, we find that incorporating the 3PCF yields a substantial improvement over two point statistics alone, tightening the constraint on sigma_8 by a factor of 5 in our fiducial forecast. This gain arises not from a localized feature or specific scale range, but from the cumulative information content across triangle configurations. Restricting to the monopole of the 3PCF captures only part of this information, with the full line of sight dependent measurement providing an additional factor of 2 to 3 improvement over the monopole. Adding line of sight dependent three point information substantially increases the constraining power of small scale configuration space
galaxy clustering.
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Cosmology and Nongalactic Astrophysics
Reheating as a variational probe of cosmological observables
Jinn-Ouk Gong
We formulate reheating as a constrained variational problem in the space of equation-of-state histories, rather than attempting to describe it through microscopic models. We introduce a regularized functional framework that identifies reheating histories which extremize a given cosmological observable under minimal physical assumptions. As illustrative applications, we consider
prompt gravitational waves, induced gravitational waves, and
primordial black holes. We find that different observables select qualitatively different regions of reheating-history space. These examples demonstrate that cosmological observables define distinct extremal directions in reheating-history space and can therefore be used to systematically explore the space of post-inflationary expansion histories.
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Quantum Physics
Distinguishing quantum processes with bounded coherent memory
Magdalini Zonnios and Felix C. Binder
Distinguishing multi-time
quantum processes is a fundamental task underlying the diagnosis, benchmarking, and learning of temporally correlated
quantum dynamics. The standard
benchmark for distinguishing two processes is the strategy-norm distance, which optimizes over arbitrary adaptive probing strategies but can require large coherent
memory and time-dependent control. We introduce machines for autonomous distinction~($\mathsf{MAD}$s): probing strategies that apply the same
quantum instrument at each time step, retain the full classical outcome record, and carry a coherent
memory of dimension $d_A$. Optimizing over these strategies defines a
memory-parametrized distinguishability measure, $d^{(N)}_{\mathsf{MAD}}(\mathbf{P}^N,\mathbf{Q}^N;d_A)$. We show that the resulting hierarchy is monotone in coherent
memory and complete at finite times. Specifically, any admissible $N$-step probing strategy can be compiled into a single $\mathsf{MAD}$ with an internal counter and sufficiently large coherent
memory, so the hierarchy saturates the strategy-norm
benchmark. For recurrent processes generated by repeated system–environment interactions, we derive a single-step description that separates the generation of new distinguishing information from the propagation and decay of information generated at earlier times. Numerical results in a repeated-interaction model show that increasing coherent
memory systematically improves the $\mathsf{MAD}$ success probability and closes the gap to the strategy-norm distance while remaining substantially more tractable to evaluate. $\mathsf{MAD}$ distinguishability therefore provides an operational and scalable framework for quantifying what can be learned about genuinely multi-time
quantum processes with bounded coherent
memory.
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Quantum Physics
Exact Markovian Dissipation Requires Singular Energy Resources
Hiroki Nakabayashi
The Gorini–Kossakowski–Lindblad–Sudarshan (GKLS) equation describes irreversible
quantum dynamical
semigroups. We show that this description cannot be exact under physically regular energy conditions. We prove that the open-system survival probability under physically regular energy conditions has sublinear decay, whereas any dissipative GKLS
semigroup has a linear short-time decay. Hence exact Markovian dissipation requires singular energy resources: an unbounded-below total
Hamiltonian or infinite initial energy, and a divergent interaction-energy moment. Therefore, a dissipative time-independent GKLS equation should be regarded as an effective description rather than the exact reduced dynamics of a
Hamiltonian dilation satisfying physically regular energy conditions.
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Mathematical Physics · Cross-listed from math.PR
The t-Split Two-Periodic Aztec Diamond Model
Meredith Shea
In this work we consider an Aztec diamond model split into two unequal regions which are asymptotically fixed in size. Each region is weighted with a distinct two-periodic weighting. We refer to this model as the t-split two-periodic Aztec diamond, to signify its difference from the previous work title Split Two-Periodic Aztec Diamond, where the model was split into two equal regions. We derive an integral expression for the correlation kernel of the model and give a partial description of the scaling limit behavior, along with a
conjecture for the remainder. We refer to the larger and smaller sides of the model as the dominant and non-dominant sides, and to the location of the weight change as the interface. The dominant side exhibits a limit shape that depends only on its own weighting and is identical to that of the two-periodic Aztec diamond, while the non-dominant side appears to have a novel limit shape that depends on both weightings and the location of the interface. Lastly, we consider the complete limit shape in the case where the dominant side two-periodic parameter goes to 0.
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Lattice Field Theory
Kernel transformations and bounds for smeared spectral functions
William I. Jay and Matteo Saccardi
This work develops a framework for transforming between smeared spectral functions computed using different smearing kernels. The kernel-transformation problem naturally arises when information is available for one family of energy-smeared observables, while phenomenology or comparison with other calculations require a different smearing. For exact transformations, analytic conditions are established for the maps to exist and converge without arbitrary regularization. Explicit expressions are provided for several kernel classes of interest, including Cauchy-to-Gaussian transformations and Gaussian-to-Cauchy width mixtures. When exact transformations are unavailable, the inverse problem is tackled through regulated maps paired with bounds on the associated systematic error, directly computable from the given input data. Errors on the input smeared spectral functions, either statistical or in the form of pointwise rigorous bounds, are then propagated to the target observables. Enforcing spectral positivity can be used to tighten the bounds.
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Quantum Physics
Entanglement Scaling and Problem Structure in Quantum Approximate and Adiabatic Optimization Algorithms
Georgios Arapantonis, Paraj Titum and Gregory Quiroz
Entanglement is widely regarded as a key resource underlying the power of
quantum algorithms and their potential to achieve
quantum advantage. With the emergence of variational
quantum algorithms, however, questions have arisen regarding how
entanglement relates to problem structure and algorithmic performance in near-term
quantum applications. Here, we examine this relationship through the
Quantum Approximate Optimization
Algorithm (QAOA), a specific class of variational
algorithms, applied to the MaxCut problem. We show that suboptimal variational parameter training can significantly modify the observed
entanglement profile, obscuring its scaling behavior. By employing a high-performance optimizer, we find empirical evidence that QAOA exhibits
entanglement scaling consistent with that of fermionic Gaussian states (up to a scaling factor) across a broad range of MaxCut instances. We further compare these results with adiabatic
quantum computation, observing annealing-schedule-dependent
entanglement profiles whose scaling behavior differs markedly from that of QAOA. Together, these findings provide new insight into how
entanglement manifests in and distinguishes these two algorithmic paradigms, highlighting its connection to both computational performance and problem structure.
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Physics and Society
Narrative Structure in Tropes: A Computational Analysis of `Friends'
Shun Zhang, Tabia Tanzin Prama, Christopher M. Danforth et al. (+1 more)
Tropes are recurring narrative devices in television and film. We carry out a computational analysis of tropes in the sitcom Friends, using human-curated trope annotations from TVTropes, episode transcripts, and IMDb ratings. Because automatic trope detection remains challenging, we treat existing trope annotations as a curated analytical layer and focus on their downstream narrative and semantic functions. We first examine the relationship between episode-level trope frequency and audience reception. We find a statistically significant positive association between trope count and weighted IMDb ratings, although the modest explanatory power suggests that more than trope density alone explains audience evaluation. We then connect trope annotations to dialogue transcripts and represent trope-related dialogue using TF-IDF-based semantic features. Using PCA and k-means clustering, we group 1,954 distinct tropes into 15 semantically interpretable clusters. Chi-square analyses show that the six main characters are unevenly distributed across these clusters, with character-specific trope profiles that are broadly consistent with their established narrative identities. Finally, we project trope clusters into the ousiometric power-danger space to examine their semantic organization. The results show that "Physical and Sexual Comedy" occupies a region associated with relatively high danger, while "Revelation, Surprise, and Reaction" occupies a region associated with relatively high power. Overall, our work demonstrates a way to operationalize trope measurement and shows that identifiable trope clusters can provide holistic "distant reading" descriptions of characters and stories.
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All authors Shun Zhang, Tabia Tanzin Prama, Christopher M. Danforth, Peter Sheridan Dodds
Soft Condensed Matter
Collective phases in overdamped magnetic self-propelled spherocylinders
Francisca Guzmán-Lastra and Néstor Sepúlveda
We study the collective dynamics of self-propelled spherocylinders carrying
magnetic dipole moments in two dimensions.
Magnetic interactions are modeled as two opposite monopoles $\pm Q$ separated by a distance $\ell$ along the particle director, a dumbbell model that remains well-defined at short range and introduces an explicit
geometric lever arm for the
magnetic torque. This approach, combined with the elongated particle geometry, produces a torque that competes with steric
alignment in a manner inaccessible to point-dipole or disk models. By independently varying monopole separation and dipole strength (parameters that map directly onto the geometry and magnetization of cylindrical magnets) we show that the system navigates a rich landscape of collective states: gas, polar flock, chain,
vortex-
alignment, and locked-dimer phases. Our results establish that particle elongation and distributed
magnetic charge together provide a minimal, experimentally accessible set of tuning knobs for controlling coherent states in
magnetic active matter, with direct implications for the design of self-organized
magnetic microswimmers and active colloidal assemblies.
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Mathematical Physics · Cross-listed from cs.IT
Ricci flow for the Bures–Helstrom qubit metric
Andrew Lesniewski
The Bures–Helstrom metric is the minimal monotone Riemannian metric on the state space of a
qubit. With the
quantum Fisher normalization used here, it identifies the Bloch ball with a geodesic hemisphere of the unit round three–sphere. We describe its
Ricci flow explicitly. In a general rotationally symmetric gauge the flow is a coupled system for the radial lapse and warping factor; a single scalar equation appears only after a Hamilton–DeTurck gauge choice. In the corresponding moving DeTurck frame the squared warping function $\Psi=\Phi^2$ satisfies the linear forced heat equation \begin{equation*} D_t\Psi=\Psi_{ss}-2, \end{equation*} while the fixed-lapse coordinate form contains the associated transport term. Since the Bures–Helstrom metric is Einstein, the
geometric flow itself is the homothetic shrinker \begin{equation*} g(t)=(1-4t)g_{\mathrm{BH}}, \end{equation*} with scalar
curvature $6/(1-4t)$ and extinction time $T=1/4$. Thus the metric remains inside the monotone cone for all $t<T$ and leaves the cone of nondegenerate Riemannian metrics only through the collapsed limit. We also record the volume–normalized flow, for which the Bures–Helstrom metric is a fixed point. Its linearization is the shifted round–sphere
Laplacian $\Delta_{\mathbb S^3}+3$, with spectrum \begin{equation*} \sigma_\ell=-(\ell-1)(\ell+3), \end{equation*} and spectral gap $5$ after removal of the scaling mode.
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Solar and Stellar Astrophysics
Simulation to a Newborn Supernova Remnant from a Low-mass Iron Core Star
Sudarshan Neopane, Michael A. Sandoval, W. Raphael Hix et al. (+3 more)
Supernova remnant observations show a high degree of asymmetry, mixing, and inhomogeneity. These asymmetries are seeded during the early seconds of the explosion and are further enhanced and modified as the shock and ejecta move through the
stellar progenitor and into the circumstellar medium. We present simulations of a 9.6
solar mass zero-
metallicity progenitor initialized after shock revival and evolved for several years when the ejecta is in the circumstellar medium. A suite of 1D and 2D simulations examines the effects of
neutron-
star wind and radioactive decay heating. In 1D, decay heating forms a low-density bubble that suppresses the reverse shock. While in 2D, the heating is localized to metal-rich pockets, inflating them and compressing the surrounding material into dense shells. In 3D the
neutron-
star wind and decay heating modify the plume morphology, producing more large-scale structures. The extended plume morphology leads to an asymmetrical shock breakout. After breakout, the leading plumes cannot keep up with the shock front, resulting in deceleration and fragmentation by the reverse shock while retaining the large-scale asymmetry. The projected ejecta morphology and velocities are strongly viewing angle dependent. The relatively uniform metal-rich distribution does not resemble the strongly inhomogeneous ejecta structure of Cas A. The 160-isotope decay network shows that 24.4% of the radioactive heating comes from decay chains other than the canonical Ni-56 chain. The low explosion energy, low Ni-56 yield, and Ni/Fe ratio greater than unity suggest an observational signature similar to an electron capture
supernova.
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All authors Sudarshan Neopane, Michael A. Sandoval, W. Raphael Hix, J. Austin Harris, O. E. Bronson Messer, Eric J. Lentz
Physics and Society
Networks of agglomeration: how population density rewires social networks and reshapes contagion dynamics
Christopher K. Tokita
From ancient Mesopotamia to modern cities, dense human settlements coincide with bursts of economic productivity, cultural innovation, and social change. But how does packing people more tightly together alter social organization in ways that reshape collective outcomes? Here, I use a minimal
agent-based model to isolate the effect of population density, holding population size and individual behavior fixed while varying only how closely individuals are placed in space. In the model, individuals form social ties gradually, favoring those nearby and those already well-connected. Under these simple rules, varying population density alone is sufficient to reorganize social network structure: sparse populations develop locally clustered communities, while denser ones form globally integrated networks with shorter social distances and a tightly interconnected core of popular individuals. This structural transition occurs sharply over a narrow range of densities and is governed by whether physical proximity or social popularity dominates tie formation. Simulating contagions on these networks reveals that the consequences of this shift depend on what is spreading. Simple contagions (e.g., information or disease) reach a majority of individuals more quickly in denser populations. Complex contagions (e.g., social norms or collective behaviors) do not spread faster, but instead achieve broader and more reliable adoption as density increases. Together, these results show that population density can act as a structural force independent of the economic and behavioral mechanisms typically invoked to explain why cities are engines of change.
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Earth and Planetary Astrophysics
Atmospheric asymmetries in WASP-121 b revealed by rotational transits detected with JWST
Cyril Gapp, Aurélien Falco, Thomas M. Evans-Soma et al. (+6 more)
Close-in
exoplanets are tidally locked to their host
star and thus exhibit extreme atmospheric temperature gradients. It has been theorized that the fraction of
star light absorbed by such
planets during transit changes as a function of orbital phase as progressively hotter or colder atmospheric gas rotates into view, but this effect has not been observed so far. Here, we show that two transits of the ultra-hot Jupiter WASP-121 b, acquired with JWST/NIRSpec and NIRISS, exhibit asymmetric transit light curves caused by the
planet's rotation during transit. We observe increasing CO absorption and slightly decreasing H$_2$O absorption in the transmission spectrum, as the
planet rotates. These results are indicative of a stronger longitudinal temperature gradient across the evening than across the morning terminator, consistent with higher temperatures in the eastern half than in the western half of the dayside. The observed changes of the transmission spectrum with orbital phase are in line with the temperature increase causing thermal dissociation of H$_2$O, while CO remains abundant. The observation of longitudinal gradients of atmospheric temperature and chemistry from the
planet's rotational transit provides a new probe for constraining atmospheric heterogeneity using JWST beyond differences between morning and evening terminators from limb asymmetries.
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All authors Cyril Gapp, Aurélien Falco, Thomas M. Evans-Soma, David K. Sing, Shashank Dholakia, Vivien Parmentier, Jérémy Leconte, Eva-Maria Ahrer, Guangwei Fu
Quantum Physics
Optimal Ansatz-free Hamiltonian Learning In Situ
Taiqi Zhou and Weiyuan Gong
Characterizing the features of a
Hamiltonian that governs a
quantum system serves as a fundamental subroutine of
quantum device calibration, signal sensing, and error correction. Recent works have proposed protocols achieving the optimal Heisenberg-limited scaling learning ansatz-free
Hamiltonians from their real-time evolutions without fully specifying interaction structures. However, these protocols rely on both deep
circuits with interleaving probes and control, and extremely short time resolution, making them difficult to implement on near- and intermediate-term in situ
quantum experiments. In this work, we propose a computationally efficient, control-free, and ancilla-free
algorithm that uses only Pauli product state preparation and measurement, and learns an ansatz-free
Hamiltonian $H$ with $||H||\leq\Lambda$ in total
evolution time of $\Theta(\frac{\Lambda}{\epsilon^2}\log(\frac{\Lambda}{\epsilon}))$. The
evolution time cost of our
algorithm is optimal for any control-free protocols as we further prove a lower bound of $\Omega(\frac{\Lambda}{\epsilon^2}\log(\frac{\Lambda}{\epsilon}))$. Technically, our method introduces a randomized-sampling framework that combines band-limited kernel-based time sampling with a displacement sieve for
Hamiltonian structure learning. The characteristic probe time resolution depends only on $\Lambda$ instead of $\varepsilon$, which makes our protocol especially appealing in the high-precision regime for sensing and calibration applications. We also show that the
algorithm maintains the same asymptotic total
evolution time in the presence of state-preparation-and-measurement (SPAM) noise when the
Hamiltonian is local after calibration. Our results demonstrate the fundamental cost of experimentally friendly
Hamiltonian learning and provide a practical route to rigorous in situ characterization of near-term
quantum platforms.
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Optics
Record nonlinear conversion efficiency in the production of high spectral purity vacuum ultraviolet laser at 148 nm
Sergey Vasilyev, Tian Ooi, Igor Moskalev et al. (+14 more)
Coherent
vacuum-ultraviolet (VUV)
lasers are indispensable for precision measurement,
quantum optics, and materials science. Recent high-resolution spectroscopy of the Th-229
nuclear clock transition near 148 nm highlights the urgent demand for intense, narrow-linewidth VUV
lasers for advancing metrology and testing fundamental physics. However, existing VUV generation schemes typically require enhancement cavities [C. Zhang et al., Opt. Lett. 47, 5591-5594 (2022)], atomic resonances [Q. Xiao et al., Nature 650, 852-856 (2026)], or random quasi-phase-matched nonlinear
crystals [V. Lal et al., Optica 12, 1971-1974 (2025)]. Here, we demonstrate a VUV frequency comb via cascaded frequency doubling of a 2400 nm Cr:ZnS comb to its 16th harmonic in nonlinear
crystals. The final stage employs a bulk-grown, spatially uniform quasi-phase matched (QPM)
crystal developed by IPG, combining VUV transparency, high $\chi^2$ nonlinearity, and power scalability. Using this QPM
crystal we generate a VUV frequency comb with 40 $\mu$W average power (1 nW per mode at 80 MHz mode spacing) with a conversion efficiency order of magnitude higher than other known methods. These results establish a scalable route to compact VUV sources via direct frequency doubling, opening a path toward a robust continuous-wave
nuclear clock
laser.
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All authors Sergey Vasilyev, Tian Ooi, Igor Moskalev, Mike Mirov, Andrey Muraviev, Dmitrii Konnov, Victor Churikov, Viktor Sukharev, Evgeny Galenin1, Jack F. Doyle, Chuankun Zhang, Kai Li, Georgiy Seryogin, Dan Perlov, Igor Samartsev, Konstantin Vodopyanov, Jun Ye
Quantum Physics
Nearest-neighbour gates are all you need: High-rate quantum low-density parity-check codes on a planar grid
Boren Gu, Tamas Noszko, Vincent Steffan et al. (+4 more)
High-performance
quantum low-density parity-check codes promise substantial reductions in the overhead of fault-tolerant
quantum computation, but most constructions require long-range connectivity or
qubit shuttling, both of which are difficult to realise in superconducting architectures. Here we introduce a family of
quantum low-density parity-check codes that, for the first time, combines planar open-boundary layouts, finite-size advantages over surface codes, and syndrome extraction using only nearest-neighbour gates on a planar grid of
qubits with either square or hexagonal connectivity. The resulting
circuits achieve optimal constant-depth stabiliser measurement, independent of code size, and naturally remove leakage from the system by exchanging the roles of check and data
qubits at each syndrome extraction round. We find finite-size instances such as a [[323,14,15]] code, whose code-efficiency ratio is nearly an order of magnitude larger than that of rotated surface-code patches. At around 40
circuit qubits per logical
qubit, the best directional tile-code layouts reduce the per-logical per-round logical error rate by a factor of 100 relative to rotated surface-code
memories. These results show that the advantages of
quantum low-density parity-check codes can survive compilation into strictly planar nearest-neighbour
circuits, bringing low-overhead fault-tolerant
memories closer to near-term hardware.
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All authors Boren Gu, Tamas Noszko, Vincent Steffan, Jens Niklas Eberhardt, Joschka Roffe, Jens Eisert, Stergios Koutsioumpas
Computational Physics
sft-wick: A formalism and package for Feynman-diagram expansion and evaluation in stochastic field theories
Zheng Zhang
When
stochastic field dynamics are cast into a path-integral formulation, perturbation theory becomes systematic but the resulting expansion quickly grows combinatorially large. The setting targeted here includes fields with several components and several dimensions,
matrix propagators, tensor-valued couplings, and non-Gaussian driving noise specified by arbitrary n-point cumulants. Wick pairings grow factorially, and component indices must be routed through the tensor-valued vertices. The useful output is not a raw contraction list, but a diagram table: one entry per
topology, with multiplicities, coupling sums, signs, and causal constraints resolved. We present sft-wick, an open-source Python package that constructs these diagram tables and computes their integrals numerically. Given an action and an observable, it enumerates topologically distinct Feynman diagrams, derives their algebraic coefficients, and evaluates the resulting diagram integrals from user-supplied response and cumulant functions. The core
algorithm enumerates spatial
topologies before routing component indices, avoiding contraction-by-contraction Wick expansion. Response-field constraints, including vanishing response-response contractions, the Ito prescription, and the absence of causal response loops, are enforced during enumeration. Predictions are validated against direct Langevin simulations in two worked examples, with Gaussian and with non-Gaussian driving noise, and agree with the simulations within stated error budgets.
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High Energy Physics (Theory)
Generating Function of single-centered Black Hole Index in CHL Models
Ranveer Kumar Singh
We present the construction of the generating function of single-centered black hole index in general $\mathbb{Z}_N$ CHL models. This is done by subtracting from the index of quarter BPS dyons, described by a meromorphic Siegel modular form, the generating function for the index of two-centered black holes. We use black hole bound state metamorphosis in CHL models for the construction of the generating function of two-centered black hole index. We prove the convergence of the generating function for the cases $N=2,3$.
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Astrophysics of Galaxies
Something green beneath the surface: The dynamical nature of Fossil Structures in IllustrisTNG-100
Mary Verdugo-Santos, Facundo A. Gómez, Diego Pallero et al. (+2 more)
Fossil structures (FS) have traditionally been considered dynamically relaxed end-products of group
evolution, characterized by a large magnitude gap ($\Delta m_{1,2} \geq 2$). However, recent observations and simulations suggest this picture is incomplete. We investigate whether FS are dynamically relaxed systems and how their
galaxy populations differ from non-fossil systems (non-FS), focusing on system dynamics and
evolution of the
galaxies inside them. Using IllustrisTNG-100, we select 182 structures ($M_{200} > 10^{13}\,M_{\odot}$) at $z = 0$, classifying them as FS/non-FS based on $\Delta m_{1,2}$ in the $r$-band. We track $\Delta m_{1,2}$
evolution over 9\,Gyr and analyze: (1) the emergence of $\Delta m_{1,2}$, (2) the fraction of quenched
galaxies (sSFR $< 10^{-11}$\,yr$^{-1}$), (3) the distribution of
galaxies in color–
stellar mass space, and (4) the gas–BSG centroid shift as a dynamical proxy. The magnitude gap in FS is primarily driven by the absence of massive recent
accretion: FS exhibit significantly lower BSG-to-satellite
stellar mass ratios ($\mu^{\rm{FS}}{\star}$=0.17 vs. $\mu^{\rm{NFS}}{\star}$=0.39) for the most massive satellite accreted within the last 6\,Gyr. FS also host a more prominent red sequence and marginally higher quenched fractions than non-FS. Our findings indicate that while the magnitude gap effectively identifies systems that have ceased major mergers in the last 3-6 Gyr, it is a poor proxy for their current global dynamical state. Both FS and non-FS populations exhibit intermediate gas-BSG offsets ($D_{BSG-CM} \approx 0.15 R/R_{200}$), failing to reach full relaxation. This decoupling suggests that the magnitude gap traces the assembly history of massive components rather than the overall stability of the intra cluster medium.
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All authors Mary Verdugo-Santos, Facundo A. Gómez, Diego Pallero, Franklin Aldás, Cristian A. Vega-Martínez
Cosmology and Nongalactic Astrophysics
Statistical Field Theory for Weak Gravitational Lensing
Zheng Zhang, Philip Bull, Chris Clarkson et al. (+1 more)
Standard weak-
lensing calculations treat
lensing as a linear remapping of the matter field along the line of sight. We instead formulate
lensing as a
stochastic field theory for the Sachs optical scalars, driven by random
Ricci-focusing and Weyl-shearing fields. With convergence and shear expressed linearly in the Sachs-scalar fluctuations, the resulting path integral generates a diagrammatic expansion for their $n$-point correlation functions, organised into linear response, nonlinear propagation, and driving-field cumulants. The conventional calculation emerges as the lowest-order, linear-propagation limit. Beyond it, nonlinear Sachs
evolution couples to driving-field non-Gaussianity, mixing the matter cumulant hierarchy into the
lensing hierarchy. A selection rule governs the couplings: an $n$-point observable receives a direct contribution from the $n$-point driving-field cumulant, and its leading hierarchy-mixing correction from the $(n+1)$-point cumulant via one nonlinear Sachs interaction, with higher cumulants entering only at higher order. The two-point function, for instance, receives corrections from three-point cumulants of
Ricci focusing and Weyl shearing through nonlinear Sachs
evolution. Rather than a restrictive approximation scheme, the formalism is a paradigm shift: a unified framework naturally accommodating path corrections, higher-order matter statistics, stochasticity, and small-scale effects.
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All authors Zheng Zhang, Philip Bull, Chris Clarkson, Andrina Nicola
Materials Science · Cross-listed from math.NA
Moreau-Yosida-based Kohn-Sham Inversion for Periodic Systems
Vebjørn H. Bakkestuen, Michael F. Herbst, Vegard Falmår et al. (+2 more)
Density-potential inversion for periodic systems within Moreau-Yosida-regularised density-functional theory is investigated, both theoretically and numerically. We develop the framework in a periodic homogeneous Sobolev space and use it to recover the exchange-correlation potential of Kohn-Sham theory through a limiting procedure. A key analytical ingredient is the proof of lower semicontinuity of the non-interacting kinetic-energy functional in the chosen
topology. The proximal mapping, together with its algorithmic evaluation, plays a central role in the resulting inversion scheme. Numerical experiments illustrate the performance and properties of the method for both the Kohn-Sham and Gross-Pitaevskii equations.
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All authors Vebjørn H. Bakkestuen, Michael F. Herbst, Vegard Falmår, Markus Penz, Andre Laestadius
Quantum Physics
Local controllability of heralded quantum linear optics
Tommaso Francalanci, Nicolò Spagnolo, Mario Sigalotti et al. (+3 more)
Photonic linear optical networks provide a versatile platform for
quantum information processing and
quantum state engineering. However, the set of states that can be generated using passive linear optics alone is fundamentally constrained by bosonic
symmetries. Heralding, based on conditional measurements on auxiliary modes, is a widely used technique to overcome these limitations and effectively enlarge the set of accessible states. Despite the widespread use of heralding, it is often unclear how specific ancillary resources impact the overall reachability of the target space. In this work, we investigate the local controllability of photonic states in linear optical networks by analyzing the rank of the Jacobian of the output state with respect to the underlying
unitary circuit, which provides a quantitative measure of the dimension of the accessible tangent space at a given configuration. Our analysis ranges from passive linear optics to heralded linear optics, where auxiliary resources and conditional measurements are included. Within this framework, we quantify how different resources enlarge the locally accessible state space beyond that of passive linear optics and determine the resources required for the Jacobian rank to reach its maximal value, thereby achieving full local controllability. As maximal local rank is a necessary condition for global reachability, our framework offers a systematic tool to assess and compare the accessible state space of measurement-based photonic architectures, and to establish practical criteria for the resources needed in high-dimensional
quantum state engineering.
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All authors Tommaso Francalanci, Nicolò Spagnolo, Mario Sigalotti, Eliott Z. Mamon, Ulysse Chabaud, Fabio Sciarrino
High Energy Physics (Theory)
Membrane instantons and non-perturbative effects in $\mathrm{AdS}_{4}/\mathrm{CFT}_{3}$
Stefan A. Kurlyand
We study Euclidean M2-brane instantons in Freund-Rubin backgrounds $\mathrm{AdS}_{4}\times \mathrm{Y}_7$. For a seven-dimensional weak $G_{2}$
manifold $\mathrm{Y}_7$, we show that the BPS condition for an M2-brane wrapping a three-cycle $\Sigma\subset \mathrm{Y}_7$ is equivalent to the associativity condition with respect to the nearly parallel $G_{2}$-structure. When $\mathrm{Y}_7$ is Sasaki-Einstein, we identify a special class of BPS M2-branes that preserve both real internal Killing spinors and correspond to invariant three-dimensional submanifolds inheriting a Sasakian structure. We analyse the quadratic fluctuations around BPS M2-brane instantons in these backgrounds. For the special class of M2-branes in Sasaki-Einstein
manifolds, the fluctuation problem reduces to transversely
elliptic complexes, and the one-loop partition function can be expressed in terms of the corresponding equivariant indices. We then apply the index formula for the one-loop partition function to invariant M2-branes in $S^{7}/\mathbb{Z}_{k}$, recovering the known result for the $S^3/\mathbb{Z}_k$ instantons and discussing more general invariant BPS cycles. As a further application, we consider M2-brane instantons with $S^3$-quotient worldvolumes in the $(p,q)$-model geometry.
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General Physics
Non-degenerate and degenerate wormholes: a unified approach
Juri Dimaschko
A generalized notion of degenerate wormholes is introduced, defined by the vanishing of the metric determinant g at the throat. It is described by the
polynomial, g^2 modified Einstein field equations. Building on this framework, we show that both the Einstein Rosen bridge and the Klinkhamer defect wormhole are exact
vacuum solutions of the g^2 modified equations, valid globally including at the degenerate throat, while the Klinkhamer configuration additionally admits traversable geometries with b>2M, where b sets the length scale of the wormhole throat and M is a mass parameter. In contrast, standard Morris Thorne and thin shell wormholes, governed by the conventional (non regularized) Einstein equations, are intrinsically non degenerate and necessarily supported by exotic stress energy. Within a unified regularized system with matter, both thin shell and Klinkhamer wormholes appear as two qualitatively distinct classes of states: non degenerate with exotic matter versus degenerate with
vacuum sharing the Einstein Rosen bridge as a common limiting configuration. This unified viewpoint clarifies why classical null energy condition no go
theorems apply only to the non degenerate sector and suggests the possibility of stationary degenerate traversable wormholes that do not require NEC violation.
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Statistical Mechanics
Exact operator dynamics in Lindbladian Wess-Zumino-Witten conformal field theories
Qicheng Tang, Ruhanshi Barad and Xueda Wen
Understanding the time
evolution of physical observables in open
quantum many-body systems coupled to external environments is a natural and difficult problem, and exact results are still rare. In this work, we study this problem for Wess-Zumino-Witten (WZW) conformal field theories with Lindblad jump operators linear in Kac-Moody current modes. We investigate the exact operator dynamics generated by these Lindbladians, identifying classes of current operators whose Heisenberg equations close and can therefore be solved analytically using the underlying current
algebra. In Abelian $U(1)_k$ WZW theories, this closure of operator dynamics holds for arbitrary settings of jump rates and includes exactly tractable cooling dynamics. In contrast, for non-Abelian WZW theories, exact closure occurs only for symmetric current-mode dissipation, where upward and downward current-mode transitions occur with equal rates, and even then it leads to a simple closed
evolution only for a single current operator. Generic imbalances, including those needed for cooling, produce additional non-Abelian terms and prevent closure of the opeartor dynamics. Consequently, the current
algebra gives rise to a broad family of exactly solvable dissipative dynamics in the Abelian setting, whereas in the non-Abelian case it singles out only a special exactly solvable dynamics corresponding to an infinite-temperature bath.
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Astrophysics of Galaxies
On the later evolution of observationally selected protocluster candidates at $z\,{\gtrsim}\,5$
Seunghwan Lim
Recent observations have revealed numerous protocluster candidates at $z\,{\gtrsim}\,5$, yet whether these systems will eventually evolve into today's
galaxy clusters remains an open question. Using the FLAMINGO simulations – resolving protocluster cores up to $z\,{\simeq}\,10$ – we track the later
evolution of observationally selected protocluster candidates, comparing three selection methods against observational samples. The observed number density falls between our mass-selected and abundance-matched samples, implying that current searches pick up both genuine cluster progenitors and significant interlopers that will not reach cluster masses by $z\,{=}\,0$. We find that candidates at $z\gtrsim5$ are heavily clustered, hosting 2$-$10 neighbors within 10\,cMpc. Consequently, a candidate with a neighbor at 5\,cMpc (10\,cMpc) faces a $\gtrsim50\%$ ($\gtrsim30\%$) probability of later merging into a larger system, mostly at $z\,{\lesssim}\,2$. The merger count converges beyond ${\sim}10$\,cMpc, pointing to a fundamental scale in structure formation. Observations show markedly weaker clustering than our simulations predict, suggesting clustering offers a currently overlooked diagnostic. Each candidate undergoes roughly 2$-$6 later major mergers, mostly with systems too small to be recognized as massive at the selection epoch. Hence, relying solely on high-$z$ mass and
galaxy overdensity to forecast a candidate's fate is prone to severe scatter and systematic error. A robust identification of true cluster progenitors demands a total mass sum of
galaxies down to the faintest levels within a 10\,cMpc radius. Upcoming surveys with both depth and area will be key to reliably linking high-$z$ protocluster candidates to their ultimate destiny.
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