Atmospheric and Oceanic Physics
Toward Actionable Predictability of Tropical Mesoscale Convective Systems through Large-scale Recurrent Environments in Northern South America
Vanessa Robledo, John F. Mejía, Jhayron S. Pérez-Carrasquilla et al. (+2 more)
Mesoscale convective systems (MCSs) produce much of the extreme precipitation, floods, and landslides that affect northern South America (NOSA), yet remain difficult to anticipate because they are strongly governed by local processes. On the night of 31 March 2017, an MCS triggered a catastrophic flash flood in Mocoa, Colombia —an event whose severity was not foreseen with sufficient lead time for emergency action, which typically requires several hours to a couple of days. Motivated by this disaster, this study investigates whether such events emerge within recurrent environments that provide a source of large-scale predictability, rather than as isolated and inherently unpredictable occurrences. We combine a 21-year (2001–2021) MCS tracking
dataset, ERA5 reanalysis, equatorial Rossby (ER) wave diagnostics, and a Self-Organizing Map (SOM) to identify recurrent environments associated with MCS occurrence in the Orinoco–Amazon basin. The Mocoa environment maps onto one of nine recurrent configurations characterized by enhanced low-level moisture, neutral Orinoco low-level jet conditions, favorable upper-level circulation, and strong ER-wave activity. We further trace convective precursors to an upstream source region over the Guiana Highlands up to 24~h before arrival in the Mocoa region. Together, these results show that the Mocoa event was not climatologically exceptional but a high-impact expression of a recurrent, partly predictable large-scale regime, demonstrating that portion of MCS predictability arise from recurring large-scale conditions that can be monitored hours to days in advance, and support hazardous weather
forecasting in NOSA and other tropical regions.
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All authors Vanessa Robledo, John F. Mejía, Jhayron S. Pérez-Carrasquilla, Mohamed Abdelkader, Humberto Vergara
High Energy Physics (Theory)
Divergences in Nonpolynomial Quantum Field Theories
Galib Hoq and Thomas Curtright
The structure of divergences in several nonpolynomial scalar
quantum field theories are investigated. Various $n$-point Green functions for nonpolynomial theories are calculated and their renormalization is analyzed, with special regard for the nonpolynomial $\left|\phi\right|^{3}$ theory in $4$ spacetime dimensions.
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High Energy Astrophysical Phenomena
Infrared Cavity Surrounding T Pyxidis: Evidence of a Nova Super-remnant?
Michael W. Healy-Kalesh and Matthew J. Darnley
Nova super-remnants (NSR) are shell-like structures spanning tens of parsecs that are predicted to grow around all recurrent novae as a result of repeated ejecta sweeping up the surrounding material. After the first NSR was discovered in the Andromeda
Galaxy around M31N 2008-12a, a number of
Galactic NSRs have been uncovered, as has the first NSR in the Large Magellanic Cloud. Here we report an apparent infrared cavity surrounding the
Galactic recurrent nova, T Pyxidis, which we suggest may be a nova super-remnant and discuss the implications.
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Materials Science
Hydrogen-stabilized multimodal high-index twin network in iron
Mehrab Lotfpour, Haoran Cui, Yan Wang et al. (+2 more)
Hydrogen significantly affects plasticity in bcc iron, but its role is commonly attributed to dislocation-mediated mechanisms, leaving the influence of hydrogen on phase transformation and deformation twinning poorly understood. We use a density-functional-theory-trained deep-neural-network interatomic potential and large-scale molecular dynamics to study pure bcc Fe and Fe containing 10% hydrogen. It is found that hydrogen lowers the yield stress but, more importantly, increases the persistence of {112} twin variants and suppresses detwinning. This effect stabilizes an interconnected {332}-{10 9 3}
multimodal twin network and produces pronounced post-yield hardening. Higher temperature promotes the initial transformation but weakens the persistence of the high-index
multimodal twin network. Moreover, twinning follows distinct loading-dependent pathways: compression generates {332} and {10 9 3} boundaries through co-zone and non-co-zone twin-twin interactions, whereas tension produces {7 4 1} boundaries through non-co-zone interactions. These results establish a pathway-based picture in which the intermediate phase determines the accessible twin modes and variant crystallography, while hydrogen and temperature control their kinetic survival and the emergence of high-index twin networks.
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All authors Mehrab Lotfpour, Haoran Cui, Yan Wang, Eduardo Vitral, Lei Cao
Statistical Mechanics
Critical escape dynamics of an active particle moving on curved surfaces
Maxim Root, Hartmut Löwen, Peter Sollich et al. (+2 more)
On the macroscopic scale, active (self-propelled) objects moving through complex environments are often subject to effects arising from both the
curvature of the surrounding surface and external influences such as
gravity. We study the Kramers escape problem for active Brownian particles in two settings: motion in an external potential driven solely by gradient forces, and motion on a curved
manifold subject to an additional constant gravitational force. In the absence of translational noise, a sharp dynamical transition occurs when the self-propulsion velocity $v_0$ reaches a critical velocity $v_c$ required for an escape. Above this threshold, the escape rate $k$ follows a universal scaling form, $k \propto \exp\left[-\mathrm{const}(v_0-v_c)^{-\gamma}\right]$, with an exponent $\gamma=3/2$ for the escape in a potential and $\gamma=1/2$ for the escape on a curved
manifold in the presence of
gravity. These distinct exponents reveal how the interplay of activity, surface
curvature, and
gravity determines the critical escape dynamics. Our theoretical predictions are verified by numerical simulations.
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All authors Maxim Root, Hartmut Löwen, Peter Sollich, Lorenzo Caprini, Alexander P. Antonov
High Energy Physics (Theory)
de Sitter Spacetime: Geometry, Causal Structure, and Quantum Fields
Azadeh Maleknejad and Ethan Richardson
de~Sitter spacetime plays a central role in modern cosmology, providing an excellent approximation to both inflation and the present accelerated expansion. It also offers a particularly simple setting in which
gravity, spacetime
symmetry, and
quantum field theory depart qualitatively from their Minkowski-space counterparts. These lecture notes introduce de Sitter spacetime, from its geometry and
symmetries to
quantum fields and perturbations on a fixed \(3+1\)-dimensional de Sitter background. We cover coordinate systems, causal structure,
unitary representations, particle production in time-dependent backgrounds, and cosmological perturbations, with emphasis on physical interpretation, applications to cosmology, and how
curvature reshapes the notions of mass,
vacuum, particles, and late-time observables.
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Plasma Physics
Demonstration of H-mode Error Field Identification in a Single Discharge via Island Healing
E.M. Bursch, A. Xie, J.L. Barr et al. (+15 more)
Non-disruptive compass scan error field identification via island healing is demonstrated on KSTAR in a single H-mode discharge. This method can allow for up to a 75% reduction in the operational time necessary for a complete compass scan by reducing the required discharges from four to one. Previous experiments on DIII-D, JET, and MAST-U have demonstrated the technique in Ohmic and L-mode but required multiple discharges and strong real-time n=1 magnetics diagnostics close to the
plasma that are unlikely to be viable for future devices. The results presented here were made possible by implementing a new set of triggering
algorithms relevant to fusion pilot plant operation into the KSTAR
plasma control system, along with KSTAR's strong RMPs and long pulse lengths. This represents a significant step towards the disruption-free error field identification method being demonstrated for deployment on future disruption-averse tokamaks, including ITER and fusion pilot plants. Steps needed to close remaining gaps to viability are addressed.
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All authors E.M. Bursch, A. Xie, J.L. Barr, S.K. Kim, N.C. Logan, S.M. Yang, J.G. Bak, W. Choi, Q. Hu, J.W. Juhn, J. Kim, J. Lee, N. Leuthold, J.K. Park, C. Paz-Soldan, L. Piron, G. Seo, J. Seo
General Relativity and Quantum Cosmology
Quasinormal modes and shadow of Schwarzschild-Tangherlini black hole with GUP
J. A. V. Campos, M. A. Anacleto, F. A. Brito et al. (+2 more)
In this work, we investigate quasinormal modes and the shadow of a Schwarzschild-Tangherlini black hole in $(d+1)$ dimensions, incorporating corrections arising from the Generalized Uncertainty Principle (GUP). Using the WKB approximation up to sixth order, we calculate the quasinormal frequencies for $l=1, 2$ and $d=3, 4, 5, 6$, and analyze the effects of the dimensionless linear and quadratic GUP parameters $\bar{\alpha}$ and $\bar{\beta}$, respectively. We find that the linear correction increases the oscillation frequency and the damping rate, whereas the quadratic correction produces the opposite behavior within the parameter range considered. Using the finite difference scheme, we obtain the time-domain
evolution and find that higher dimensions lead to faster damping and that the visibility of GUP-induced modifications to the time-domain waveform depends on the excitation profile of the initial perturbation, whereas the underlying quasinormal spectrum remains determined by the black hole geometry.Furthermore, we investigate the shadow and establish its correspondence with the quasinormal spectrum in the eikonal limit through the properties of the unstable circular null geodesics. Finally, we confront the predicted shadow size with Event Horizon
Telescope observations of Sagittarius A* and use these constraints to investigate the allowed GUP parameter space.
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All authors J. A. V. Campos, M. A. Anacleto, F. A. Brito, E. Passos, Amilcar R. Queiroz
Astrophysics of Galaxies
S. Fujimoto, Q. Fei, G. B. Brammer et al. (+41 more)
We report a long-lived
nuclear transient in GNz7q, a red
quasar at $z=7.19$ powered by a $\sim3\times10^{7}\,M_\odot$ black hole and hosted by a compact, dusty starburst
galaxy. The transient was identified in more than two decades of imaging with HST, Spitzer, and JWST. After a rapid rise, the source faded smoothly by $\Delta m\simeq1.1$ mag in the rest-frame ultraviolet over $\sim2$ rest-frame yr, with coherent, wavelength-dependent
evolution across 1–5 $\mu$m that places GNz7q above the 99.9th percentile of the SDSS
quasar variability distribution and is absent at $z\gtrsim5$. The duration and energetics disfavor superluminous
supernovae, and
stochastic quasar variability reproduces the multi-band
evolution with a probability of $\lesssim10^{-5}$. A panchromatic model combining a thermal continuum with a $t^{-5/3}$ decline reproduces the light curves, yielding a peak bolometric luminosity of $\simeq3\times10^{45}$ erg s$^{-1}$ and a radiated energy of $\simeq1.5\times10^{53}$ erg, which imply the
tidal disruption of a
star of a few
solar masses and place the event among the most energetic
tidal disruption events (TDEs) known. A redshifted, extremely broad Balmer-line component in independent JWST/NIRSpec spectroscopy is consistent with a transient, non-virialized broad-line region. JWST/MIRI photometry further reveals delayed mid-infrared emission from $\simeq1500$ K
dust at a sub-parsec radius, consistent with a
dust echo of the
flare. The relatively low black-hole mass and dense
star-forming
nucleus of GNz7q are conditions under which TDEs are expected to be most efficient. These observations provide a time-domain view of episodic black-hole fueling and its dusty
nuclear environment 700 million years after the Big Bang. Wide-field surveys with Roman and Euclid in the near-infrared, complemented by LSST at lower
redshifts, may uncover such transients in large numbers.
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All authors S. Fujimoto, Q. Fei, G. B. Brammer, K. Inayoshi, V. Kokorev, L. C. Ho, R. Li, F. Walter, V. Bromm, L. Colina, P. Dayal, S. L. Finkelstein, M. Ginolfi, Z. Liu, G. C. K. Leung, G. E. Magdis, J. Matthee, R. P. Naidu, P. Oesch, M. Onoue, P. G. Pérez-González, D. Watson, J. Álvarez-Márquez, J. Antwi-Danso, Y. Asada, G. Barro, C. M. Casey, J. Chisholm, S. Gillman, R. Marques-Chaves, J. P. U. Fynbo, T. R. Greve, I. Labbe, R. A. Meyer, F. Rizzo, A. Robbins, R. Schneider, C. L. Steinhardt, S. Toft, A. Trinca, F. Valentino, R. Valiante, M. Vestergaard, M. Xiao
Astrophysics of Galaxies
SN Helios: A Multiply Imaged Type II Supernova Opening Time-Delay Cosmography beyond redshift of 3
Seiji Fujimoto, Conor Larison, Justin D. R. Pierel et al. (+63 more)
We report the discovery and spectroscopic confirmation of SN Helios, a strongly lensed, multiply imaged Type II
supernova (SN) at $z=3.34$ behind the
galaxy cluster RXC J0018.5+1626. The transient was identified as a red F150W-dropout source (F277W = 26.1 mag) in JWST/NIRCam imaging taken on 2026 July 3 for the VENUS survey, with no counterpart in 2024 December imaging. Director's Discretionary Time observations on 2026 August 17 added second-epoch NIRCam imaging and a deep NIRSpec prism spectrum. The spectrum shows a strong, spectrally resolved H$\alpha$ emission line (FWHM $\approx 7900$ km/s) with a P-Cygni absorption blueshifted by 8800 km/s, together with corresponding H$\beta$ and He I $\lambda$10830 features, establishing a hydrogen-rich photosphere at $z=3.34$. Template fits classify SN Helios as a Type II SN, and light-curve comparisons with well-studied local SNe II yield a phase of $27.5\pm2.8$ rest-frame days past B-band maximum. Independent cluster lens models magnify the observed image by $\mu\approx 10$-20 and predict another image within $\simeq 2$-6 yr, offering a rare opportunity for a time-delay measurement of $H_{0}$ with a source at $z>3$. The host
galaxy is undetected in deep rest-frame ultraviolet and optical imaging, in emission lines, and in ALMA 2 mm
dust continuum, leaving a heavily obscured counterpart unlikely. Its de-lensed $M_{\rm UV}\gtrsim -13$ places it far below blank-field limits and adds support to an elevated core-collapse rate per unit
star formation in ultra-faint
galaxies. Without the multi-epoch data, SN Helios would masquerade as a convincing $z\approx 16$ Lyman-break
galaxy, with
galaxy-template fits strongly disfavoring any low-
redshift solution even with multiple medium bands. Its spectrum thus provides an empirical SED template with which high-
redshift searches can vet similar dropout candidates.
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All authors Seiji Fujimoto, Conor Larison, Justin D. R. Pierel, Lukas J. Furtak, Masamune Oguri, Adi Zitrin, Jose M. Diego, Keren Sharon, David A. Coulter, Gabriel Brammer, Vasily Kokorev, Chelsea Nash, Pedram Abedi, Christa DeCoursey, Armin Rest, Andreas L. Faisst, Brenda L. Frye, Tiger Yu-Yang Hsiao, Kohei Inayoshi, Kotaro Kohno, Jorryt Matthee, Matteo Messa, Yoshiaki Ono, Fengwu Sun, Eros Vanzella, Rogier A. Windhorst, Abdurro'uf, Aadya Agrawal, Joseph F. V. Allingham, Yoshihisa Asada, Hakim Atek, Maruša Bradač, Larry D. Bradley, Mateusz Bronikowski, Dan Coe, Christopher J. Conselice, Pratika Dayal, Eiichi Egami, Michael Engesser, Gavin Scott Farley, Qinyue Fei, Ori D. Fox, Yoshinobu Fudamoto, Miriam Golubchik, Yuichi Harikane, Gourav Khullar, Tomokazu Kiyota, Paulo A. A. Lopes, Ray A. Lucas, Guillaume Mahler, Ashish Kumar Meena, Rohan P. Naidu, Gautham Narayan, Gaël Noirot, Pascal A. Oesch, Masami Ouchi, José María Palencia, Massimo Pascale, Luke Robbins, M. R. Siebert, Roberta Tripodi, Francesco Valentino, Darach Watson, Hayley Williams, Hiroto Yanagisawa, Anita Zanella
Mathematical Physics · Cross-listed from math.AP
Sharp critical Strichartz estimates for a resonant hyperbolic Schrödinger flow on the 3D waveguide
Xi Cen and Zhezhi Zhang
We study critical Strichartz estimates for the resonant
hyperbolic Schrödinger flow on the waveguide $\mathbb{R} \times \mathbb{T}^2$. For initial data localized to frequencies at most $N$, we prove that the unit-time $L^2\to L^{10/3}$ operator norm has sharp order $N^{1/5}$. We further track its dependence on the observation length, obtaining sharp estimates in the short- and long-time regimes and characterizing the frequency-dependent intervals on which the critical estimate remains lossless. The precise dependence on $T$ in the intermediate regime $N^{-1}<T<1$ remains open. The upper bounds are obtained by lifting the global endpoint estimate on the
elliptic cylinder $\mathbb{R} \times \mathbb{T}$ to
Hilbert-valued data, preserving its time summability, and combining this with periodic Bernstein and interpolation. The lower bounds exploit an exact integer null direction in the periodic frequency
lattice together with a suitably scaled Euclidean wave packet. Finally, using a Bloch–Floquet transference argument, we recover the known
elliptic unit-time estimate from compact
torus theory and obtain a lossless
elliptic estimate on frequency-dependent short time intervals.
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Materials Science
Activating Basal Planes in Transition Metal Dichalcogenides for CO2 Reduction to CO through Alloying
Eric Montufar-Morales, Daniel Rinder, Pravan Omprakash et al. (+2 more)
Transition metal dichalcogenides (TMDCs) have emerged as highly tunable platforms for electrocatalysis, particularly for the CO2 reduction reaction (CO2RR). While TMDC edge sites exhibit catalytic activity, the basal plane is typically inert, severely limiting the overall active site density. In this work, we show that sulfur vacancies activate the basal plane of 1H-TMDCs, while concurrent solid-solution alloying provides a mechanism to broadly tune intermediate adsorption energies. We evaluate a library of quasi-binary TMDC sulfide
alloys comprising V, Nb, Ta, Mo, and W, screening them by stability, defect energetics, and competitive selectivity to identify the most effective catalysts for CO2RR. Electronic-structure analysis reveals that a d-band center closer to the
Fermi energy weakens intermediate binding by leaving key bonding states unoccupied above the
Fermi energy. Our calculations identify (Nb,Ta)S2 as a promising catalyst with low sulfur vacancy formation energies, near-optimal CO2RR intermediate binding, and selectivity against the hydrogen
evolution reaction. Overall, this work establishes a rational design framework for TMDC
alloy catalysts through the simultaneous use of defect engineering and alloying.
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All authors Eric Montufar-Morales, Daniel Rinder, Pravan Omprakash, Rohan Mishra, Gwan Yeong Jung
Medical Physics · Cross-listed from eess.IV
PGDM-MRSRGAN: Physics-Guided Degradation Model with an SRGAN Framework for Magnetic Resonance Image Super-Resolution: Applications in Low-Field MRI
Yashwant Kurmi, Charlotte R. Sappo, Sai Abitha Srinivas et al. (+3 more)
Magnetic Resonance Imaging (MRI) often suffers from low signal-to-noise ratio (SNR) and limited spatial resolution, which compromise clinical precision. This study aims to address these challenges by developing a physics-guided degradation model (PGDM) and a novel deep learning framework,
Magnetic Resonance Super-Resolution GAN Imaging (MRSRGAN), for improved super-resolution reconstruction of MRI images. The proposed approach consists of two stages: (1) a physics-guided degradation model that simulates low-field MRI conditions by incorporating artifacts such as blur, B0 inhomogeneity, chemical shift effects, down-sampling, and noise to generate paired low-resolution (LR) and high-resolution (HR) training
datasets; and (2) an MRSRGAN-based reconstruction network utilizing a hybrid loss function, including modified spectral angle mapper (MSAM) and sharpened ground truth images based on de-convolution of slice profile-based kernels to restore high-SNR and high-resolution images. Experimental validation demonstrates that the proposed method achieves superior spatial resolution, enhanced SNR, improved peak signal-to-noise ratio (PSNR), higher structural similarity index (SSIM), reduced MSAM error, and better non-reference image quality evaluation (NIQE) metrics. Furthermore, it effectively reduces artifacts and demonstrates robustness on real MRI
datasets. The MRSRGAN framework, guided by the physics-informed degradation model, provides a significant improvement in MRI image quality, enhancing spatial resolution and diagnostic accuracy. Its demonstrated robustness and effectiveness on real MRI
datasets highlight its potential to resolution enhancement for precise diagnostic imaging.
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All authors Yashwant Kurmi, Charlotte R. Sappo, Sai Abitha Srinivas, Selin D. Kandemir, Malvika Viswanathan, Zhongliang Zu
Mesoscale and Nanoscale Physics
Engineering nonlinear spin-orbit torque driven by intra-band transport in MoSe$_2$/CrI$_3$ and WSe$_2$/CrI$_3$ van der Waals heterostructures
Leyla Majidi, Azadeh Faridi and Reza Asgari
The role of nonlinear carrier dynamics in current-driven
spin phenomena remains poorly understood in van der Waals
magnetic heterostructures. Here, we investigate the
spin polarization and the resulting
spin-orbit torque (SOT) in transition-metal dichalcogenide/chromium iodide (TMDC/CrI$_3$)
heterostructures, focusing on WSe$_2$/CrI$_3$ and MoSe$_2$/CrI$_3$, in the zero-Rashba
spin-orbit coupling (SOC) limit and beyond the linear-response regime. We find that linear
spin polarization is forbidden by
symmetry, making nonlinear intraband transitions the dominant mechanism in this regime. Consequently, the current-driven
spin response differs fundamentally from conventional linear-response predictions. The resulting nonlinear
spin polarization generates a purely field-like torque whose magnitude and sign depend sensitively on the chemical potential and doping type, with pronounced asymmetries between n- and p-doped systems. A strong material dependence is also observed: n-doped MoSe$_2$/CrI$_3$ exhibits a torque nearly an order of magnitude larger than that of WSe$_2$/CrI$_3$, together with two sign reversals, reflecting differences in their SOC and proximity-exchange parameters. Structural and electrostatic control through the twist angle and gate electric field provides additional means of tuning the nonlinear torque, including substantial modulation and controllable sign reversals. These findings establish TMDC/CrI$_3$
bilayers as a versatile platform for engineering nonlinear
spin-orbit phenomena in ultrathin, low-power spintronic devices.
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High Energy Physics (Theory)
Classification of Conformal Supersymmetric Deformations of Schwarzschild Spacetime via Super Poisson-Lie T-duality/Plurality
Ali Eghbali, Meysam Hosseinpour-Sadid and Adel Rezaei-Aghdam
This paper investigates conformal supersymmetric deformations of Schwarzschild spacetime through the framework of super Poisson-Lie T-duality/plurality. We first study super non-Abelian T-duality in $\sigma$-models featuring a Schwarzschild metric coupled to two fermionic fields. This is realized by describing the original four-dimensional geometry and its dual counterpart via semi-Abelian Drinfeld superdoubles generated by the Lie superalgebras $({\C}^3 +{\A})$, ${\C}^3 \oplus {\A}_{1,1}$ and $(2{ \A}_{1,1}+2{ \A})^0$, supplemented by two spectator fields. We enforce the vanishing of one-loop beta-function equations for both original and dual models to guarantee UV finiteness at
quantum level; this procedure necessitates the inclusion of the dilaton field alongside the metric and the Kalb-Ramond field ($B$-field) already present in the classical action. We further study the
curvature invariants, singularity structure, and superisometries, and compare the resulting supergeometries, with particular emphasis on their fermionic parts and $B$-fields. Starting from the decompositions of semi-Abelian Drinfeld superdoubles associated with the $({\C}^3 +{\A})$ and ${\C}^3 \oplus {\A}_{1,1}$ Lie superalgebras, we derive the conformal duality/plurality chains for four-dimensional string backgrounds, characterized by a Schwarzschild metric coupled to two
fermions. Our results span an interesting spectrum of super Poisson-Lie T-dual $\sigma$-models described by Lie superalgebras with two bosonic and two fermionic generators. These are all non-trivial and interesting examples of super Poisson-Lie T-dual models which help in the intent of providing a general classification of four-dimensional geometries describing supergravity backgrounds.
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Statistical Mechanics
Unified description of random motions and generalized Fokker-Planck equations
Luca Angelani
This review surveys diverse types of random motion within a unified framework, introducing essential mathematical tools, including special functions and fractional calculus, in a pedagogical manner. We focus on generalized random motions in one-dimensional space described by Fokker-Planck like equations, whose fundamental solutions take a universal and simple form in the Laplace-
Fourier domain in terms of a generic function $\varphi(s)$. By exploring the functional forms of $\varphi(s)$ consistent with physical constraints, we derive a broad class of
stochastic dynamics. This includes Brownian and active motion, simple and anomalous
diffusion, and processes featuring
stochastic resetting or trapping mechanisms. For each case, we provide the corresponding kinetic equation, explicit solutions (where available), and mean-square displacements alongside their asymptotic behaviors. Finally, we discuss the physical interpretation of these motions through the lens of time-changed processes and subordinators.
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Materials Science
Current density functional theory in the age of generalized Kohn-Sham theories
Giovanni Vignale
I review the
evolution of electronic non-relativistic current density functional theory (CDFT) from its original formulation in the late 1980's to present day's formulations, which rely on the generalized Kohn-Sham theory. Axel Becke's outstanding contributions are highlighted throughout. I propose a form of the generalized Kohn-Sham equation that combines the exchange-correlation vector potential of the original formulation with an “effective mass term" – the latter following from the inclusion of Becke's kinetic energy density as a basic input of the exchange-correlation energy functional.
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Atmospheric and Oceanic Physics
Understanding Perturbed Parameter Ensemble Sensitivities Using A Contrastive Learning Approach
Da Fan, David John Gagne II, Gregory S Elsaesser et al. (+5 more)
Perturbed parameter ensembles (PPEs) reveal how physics parameters affect
climate simulations, but interpreting parameter sensitivities across multivariate, spatially structured outputs remains challenging, particularly when calibrating models against observations. We develop an explainable contrastive learning model that maps 5 monthly cloud and radiation fields into a shared representation space. We train the model on the fields of two 100-member Community Atmosphere Model version 6 (CAM6) PPEs, spanning 34 parameters, that only differ in the warm rain microphysics scheme: KK2000, the default bulk microphysics scheme, and TAU-ML, a neural network emulator of a bin microphysics scheme. The learned representations separates two PPEs with over 94% linear classification accuracy while preserving the seasonal variability and ensemble spread due to parameter perturbations. In the shared representation space, the representations of satellite observations occupy the same low-dimensional
manifold as the PPEs but are displaced from them most strongly during boreal spring and autumn. TAU-ML PPE has a lower distance to observations compared to KK2000 in the representation space. Integrated Gradients attributions highlights the contributions in subtropical low-cloud regions, Northern and Southern Hemisphere storm track regions, and tropical convection regions to differences between PPEs and observations. Regional attributions correlate most strongly with parameters associated with cloud microphysics, boundary layer
turbulence, and deep convection. These results demonstrate that explainable representations of
climate fields can attribute model differences to specific variables, regions, seasons, and physical parameters.
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All authors Da Fan, David John Gagne II, Gregory S Elsaesser, Brian Medeiros, Addisu G Semie, Qingyuan Yang, Akila Sampath, Subashree Venkatasubramanian
General Relativity and Quantum Cosmology
On the completeness of gravitational pp-wave spacetimes: A counterexample to the {Ehlers–Kundt} conjecture
Hannah Cairo
This paper concerns the geometry of gravitational pp-wave spacetimes. We give a counterexample to the Ehlers–Kundt
conjecture. In fact, we show that geodesic completeness is generic, in the sense of Baire category, among gravitational pp-waves. We also define a concept of “universal pp-wave”, i.e. a pp-wave whose metric approximates that of every other gravitational pp-wave arbitrarily closely on arbitrarily large compact sets, and we show that there are geodesically complete universal pp-waves. Our machinery also suffices to give a new proof of the
polynomial case of the Ehlers–Kundt
conjecture (previously proved by Flores and Sánchez).
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High Energy Physics (Phenomenology)
A Phase-Space Inclusive Figure of Merit Based in Optimal Transport for Validating Monte Carlo Reweightings
Rishabh Jain, Lauren Hay, Matt LeBlanc et al. (+1 more)
Validating whether the underlying physics of a model has been retained after a full phase-space reweighting poses a unique challenge. Often, validation relies on comparing histograms of 1D observables; however, this can mask correlations and biases in the complete prediction. We present a novel, unbinned approach to comparing the performance of such reweighting schemes based on the "Cross-Section-Mover's Distance", an application of Optimal Transport that quantifies the work required to transform one theoretical prediction into another and enables an interpretation of results in terms of metric spaces. We demonstrate its utility when benchmarking various reweighting schemes that mitigate the effects of negative weights in a Monte Carlo simulation. This approach can be broadly applied in other scenarios where biases in full phase-space reweighting schemes should be studied in an unbinned way.
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All authors Rishabh Jain, Lauren Hay, Matt LeBlanc, Jennifer Roloff
High Energy Astrophysical Phenomena
Machine Learning $\beta$-decay Half-lives and Their Application to $r$-Process Observables
Mengke Li, Flora Wang, Jonathan Engel et al. (+3 more)
Accurately modeling $\beta$-decay half-lives of highly
neutron-rich
nuclei is a critical challenge for understanding $r$-process nucleosynthesis and the resulting kilonova light curves. We introduce a data-driven approach to model $\beta$ decay that uses Mixture Density Networks (MDNs) trained on the latest experimental measurements to extrapolate the half-lives of
neutron rich
nuclei. Unlike standard deterministic regression, the MDN directly parameterizes the probability distribution of the half-lives, providing intrinsic (aleatoric) uncertainty. We contrast the intrinsic uncertainty of a single model with the range of models produced by using random variations of the input training data samples. While all models show excellent agreement with experimental data, we find that varying the training data sets produces a wide range of extrapolations, particularly along data-poor regions such as the $N=126$ isotonic chain. We then propagate a selection of model results into $r$-process network calculations to evaluate their impact on isotopic abundances. Finally, by coupling the resulting isotopic abundances with thermalization efficiencies, we translate the effective
nuclear heating rates into bolometric light curves. We compare the ranges of outcomes produced from the intrinsic uncertainty of a single model to those produced by multiple independent models trained on different training data sets.
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All authors Mengke Li, Flora Wang, Jonathan Engel, Matthew Mumpower, Rebecca Surman, Nicole Vassh
Mathematical Physics · Cross-listed from math.GT
Planar Contact Structures with Calabi-Yau Fillings and Topological Quantum Computation
Atsuhide Mori
We study planar openbooks obtained by lifting braids through branched covers of D^2, together with the
quantum operations in the Ising representation. We give a criterion for the Stein fillings to be Calabi-Yau (CY). Among positive factorizations of a fixed monodromy, a CY one has minimal length and its filling minimizes \chi and b_2. Applied to Baykur's recent examples, this gives a planar contact 3-
manifold with infinitely many non-homeomorphic CY fillings, the cover there having degree \ge 6. At degree 4 a single CY filling forces every filling to be CY, and in one case the filling is unique; at degree \le 3 it is unique, and CY under a mild condition. Admissible cuts of D^2 decompose the openbook into subopenbooks. Every positive factorization then localizes, and the CY condition holds exactly when it holds locally. The state space is then a direct sum of tensor products indexed by the compatible parity choices, with at most two
qubits per factor when the pieces have degree $\le 4$, the same range in which the CY condition depends only on the monodromy. For one degree 4 cover, the points, lines and flags of the two-
qubit doily are realized by its subopenbooks. Fifteen liftable braids there share the same
quantum operation and Stein filling, and are separated only by the subopenbook systems they admit. A choice of tensor-product structure is thus carried by the lift, not by the braid group representation, suggesting a link between contact
topology and
quantum entanglement.
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Instrumentation and Detectors
Point-cloud generative models for fast calorimeter simulation across particles and geometries
Thorsten Buss, Henry Day-Hall, Frank Gaede et al. (+7 more)
Detailed Geant4 simulation of calorimeter showers is the largest single computing cost of
collider experiments, and the High-Luminosity LHC will need about ten times more simulated events than are currently produced. We summarise recent progress in generative point cloud fast simulation for highly granular calorimeters. CaloClouds3 generates
photon (electromagnetic) showers, is geometry-independent, and runs on average about 120x faster than Geant4 on a single CPU. CaloHadronic uses
transformer attention to extend the point cloud
diffusion approach to pion (hadronic) showers spanning the electromagnetic and hadronic calorimeters. AllShowers unifies twelve particle types in a single model with far fewer parameters than the specialised baselines while matching or exceeding their fidelity. We close with cross-geometry transfer learning, which needs two to three orders of magnitude fewer training showers while preserving the generative performance.
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All authors Thorsten Buss, Henry Day-Hall, Frank Gaede, Gregor Kasieczka, Katja Krüger, Anatolii Korol, Thomas Madlener, Peter McKeown, Martina Mozzanica, Lorenzo Valente
Quantum Physics
Generation of Photonic Graph States with minimal number of quantum emitters
Konstantinos-Rafail Revis, Nils Tomke Ottink, Pierre-Emmanuel Emeriau et al. (+1 more)
Graph states are a fundamental resource for measurement and fusion-based
quantum computing,
quantum networks, and sensing. Preparing them in a photonic system deterministically is, in principle, possible, but finding efficient schemes to prepare them was a long-standing problem addressed recently. Additionally, heuristic optimization schemes for reducing the required number of two-
qubit gates were developed. However, the problem of reducing the number of emitters by optimizing the emission ordering was not addressed, due to its computational complexity, as it is connected to a well-known NP-hard problem from graph theory, the linear rank width computation. In this work, we focus on developing heuristic
polynomial algorithms to reduce the number of emitters required. In total, we propose four distinct
algorithms, which demonstrate up to $30\%$ emitter reduction on random graphs. Furthermore, we provide numerical and statistical evidence that the combination of our optimization schemes with the preexisting
algorithms for optimizing the two-
qubit gates of the preparation protocol can further reduce them by around $20\%$. Finally, we examine the developed
algorithms for various useful graph state families, such as graphs useful for measurement-based
quantum algorithms, and cluster states and graph codes used for
quantum error correction, to determine the performance of each
algorithm.
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All authors Konstantinos-Rafail Revis, Nils Tomke Ottink, Pierre-Emmanuel Emeriau, Paul Hilaire
Quantum Physics
Three-uniform edge-ordered hypergraph quantum states: entanglement and its relation to hypergraph properties
N. A. Susulovska and Kh. P. Gnatenko
The encoding of 3-uniform edge-ordered weighted hypergraphs into multiqubit
quantum states is proposed. We derive an analytical expression for the
geometric measure of
entanglement of hypergraph
quantum states and establish its relation to hypergraph properties. The results establish a direct connection between the local structure of hypergraphs, hyperedge weights, and the
entanglement of the corresponding
quantum states. For equally weighted hypergraphs, it is shown that the
entanglement depends explicitly on the vertex degree. The dependence of
entanglement on hypergraph parameters is studied analytically and using
quantum computing. Hypergraph states associated with chain,
star, regular
lattice, and binary-tree hypergraphs are examined, and their
entanglement is quantified using
quantum computing. These results open up the possibility of studying hypergraph properties with
quantum programming.
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Quantum Physics
Optimal noisy sequential multiparameter quantum sensing
Andrew Tanggara, Lorcán O Conlon, Alexey V. Gorshkov et al. (+1 more)
The most general strategy for estimating parameters of a
quantum channel is to probe the channel many times sequentially with the help of coherent ancillary systems. However, finding the strategy that minimizes the mean-squared error (MSE) is a notoriously hard problem, requiring optimization over the initial probe state, intermediate evolutions, final measurement, and classical postprocessing. In this work, we study how the minimum attainable MSE can be bounded from below in this setting. We propose a lower bound for the MSE of any physically implementable sequential sensing strategy that applies to estimating parameters of any physical
quantum evolution, including
quantum channels probed over multiple time steps under temporally correlated noise and general temporally correlated
quantum processes. We show that this lower bound can be formulated as a semidefinite program (SDP). Our bound generalizes the Nagaoka-Hayashi lower bound (that applies to parameter estimation tasks with separable measurements) to the regime where the
quantum channel can be accessed sequentially multiple times. For regular finite-dimensional single-parameter sequential estimation tasks admitting an optimal strategy, we show that our SDP bound is tight and provide a procedure to obtain a locally optimal strategy from the SDP optimizer. Using our optimization bound, we compute the MSE lower bound and derive new protocols for several other physically motivated problems including error-corrected
quantum sensing under an unknown correlated noise model, multiparameter estimation, and estimation with qudit systems.
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All authors Andrew Tanggara, Lorcán O Conlon, Alexey V. Gorshkov, Kishor Bharti
High Energy Astrophysical Phenomena
Interaction of stellar dipole and disk magnetic fields in accretion-ejection systems
Somayeh Sheikhnezami and Sarah Aslani
We study jet formation from a magnetically diffusive, sub-Keplerian
accretion disk threaded by different
magnetic field configurations. We present two dimensional, axisymmetric MHD simulations in spherical coordinates employing the PLUTO code. Our results show that the reference simulation, in which the disk is threaded by an initial large scale poloidal
magnetic field, reaches a quasi steady state and produces a well collimated jet.Both kinetic and
magnetic torques are significant and evolve smoothly over time. The
accretion process is established smoothly, with about 26% of the accreting material being delivered into the
outflow. Alternatively, applying a purely
stellar dipolar
magnetic field produces weak and unstable
outflows, characterized by inefficient angular momentum transport and strongly suppressed
accretion. Additionally, in simulations where the
stellar dipolar
magnetic field is present alongside the disk's initial poloidal
magnetic field, the disk
magnetic field predominantly stabilizes the system. It also facilitates angular momentum transport from the disk and sustains a significant
outflow mass flux. Furthermore, we performed additional simulations that explicitly include an inner gap associated with the disk truncation region. These simulations were designed as a robustness test of the treatment of the innermost disk region and confirm that our main conclusions are not sensitive to the presence of this gap. Overall, our findings demonstrate that although the magnitude of
stellar dipole plays an important role in the
evolution of the
accretion-ejection structure, the large scale poloidal
magnetic field threading the disk is essential for launching and sustaining a stable and well collimated magnetized jet.
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Cosmology and Nongalactic Astrophysics
Analyzing $\mu$ Parameter Range and the Duration of Reheating in the Polynomial $\alpha$-attractor Models using CMB Observations
Ajay Atwal and Apurba Samanta
Cosmological $\alpha$-attractor models are renowned for their universal predictions for inflationary observables, largely independent of the detailed form of the inflaton potential. In this work, we investigate the extent to which this universality persists for
polynomial $\alpha$-attractor models, with particular emphasis on the scalar spectral index ($n_s$) and the post-inflationary reheating history. We derive an extended analytical expression for the scalar spectral index ($n_s$) and the tensor-to-scalar ratio ($r$), retaining sub-leading contributions beyond the commonly used universal approximation. Interestingly, we find that these corrections introduce an explicit dependence of $n_s$ on the parameter characterizing the
polynomial attractor potential $\mu$, a dependence that is absent in the leading universal expression. We systematically investigate how this model dependence modifies the predictions in the $(n_s-r)$ plane and affects the model parameter ($\mu$). We further incorporate the Duration of reheating ($\Delta N_{rh}$) and effective equation of state parameter of the reheating epoch ($w_{rh}$), accounting for their impact on the number of e-folds between horizon crossing and the end of inflation ($\Delta N_{\mathrm{CMB}}$). By confronting the resulting predictions with current CMB observations, we identify the viable parameter space and examine the interplay between the model parameter ($\mu$) and reheating. Our results demonstrate that sub-leading corrections can provide a window into the underlying structure of
polynomial attractors, offering a possible way to distinguish different members of the attractor class observationally.
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Computational Physics · Cross-listed from cs.CE
Perspectives on Sustainable Computational Science and Engineering
Julia Kowalski, Ann S. Almgren, Achim Basermann et al. (+43 more)
Computational Science and Engineering (CSE) combines expertise at the intersection of engineering, applied mathematics, and computer science to form powerful methods for model-based design and model-based decision support across disciplines. Today, CSE methods and tools have an impact as an enabling technology in the development of increasingly sustainable products, processes, and operations. However, sustainability is rarely considered holistically in the context of CSE itself. This paper develops a perspective on sustainability in CSE by distinguishing CSE as an enabler of sustainability in application domains from sustainability within CSE itself, which rests on two complementary pillars: sustainable computing and sustainable software. We present illustrative examples for these pillars and derive recommendations and best practices for CSE stakeholders. Developing an understanding of how sustainability can create added value in CSE is an important future direction for the field. This calls for a concerted effort within the CSE community to define measurable outcomes and best practices that embed sustainability as a core design principle rather than an afterthought.
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All authors Julia Kowalski, Ann S. Almgren, Achim Basermann, Alan Correa, Immo Huismann, Uwe Naumann, Hendrik Ranocha, Matthias Rauter, Jens Saak, Michael Schlottke-Lakemper, Robert Speck, Manuel Torrilhon, Mario Wolter, Niklas von der Assen, Maria Guadalupe Barrios Sazo, Dipankul Bhattacharya, Marcel Bock, Faras Brumand-Poor, Dirk Brömmel, Semih Burak, Sara Grundel, Christiane Helzel, Bruce Hendrickson, Robert Klöfkorn, Katharina Kormann, Zahra Lakdawala, Hannah Lanzrath, Camilla Lüttgens, Anna Matuszy`nska, Matthias Meinke, Abigail Morrison, William S. Moses, Georgii Oblapenko, Marcel Pfeiffer, Jana Sasse, Katharina Schmitz, Miriam Schulte, Anna Schwarz, Pit Steinbach, Ingo Steldermann, Anton Stratmann, Lambert Theisen, Joseph De Veaugh-Geiss, Tim Wegmann, Gabriel Wittum, Anil Yildiz
Quantum Physics
Rényi Phase Transitions and Analytic Continuation to the von Neumann Entropy
Ayush Raj, Akash Vijay, Hong-Chen Jiang et al. (+1 more)
Extracting operationally meaningful quantities such as von Neumann
entropy and mutual information is central to characterizing many-body
quantum systems, yet experiments and numerics often provide direct access only to integer Rényi
entropies. Whereas conventional extrapolation relies on a prescribed fitting ansatz, in PRL 137, 100202 we introduced an alternative approach based on stabilized analytic continuation (SAC), which avoids such an ansatz and is inherently robust to noise. Here, we further develop this framework in the noiseless setting and
benchmark its performance across several nontrivial many-body problems. We first show that, besides the intrinsic ambiguity of reconstructing the von Neumann
entropy from finitely many Rényi samples, analytic continuation can also fail because of genuine nonanalyticities in the Rényi function arising from zeros of $\text{Tr}\rho^z$. We derive universal zero-free domains for $\text{Tr}\rho^z$ and systematically sharpen these bounds using additional spectral information about $\rho$. We then
benchmark the performance of SAC in three settings: ($i$) extracting topological
entanglement entropy from DMRG Rényi data for the toric code and Kagome Heisenberg models; ($ii$) reconstructing the mutual information between disjoint intervals in a $(1+1)d$ compact-
boson CFT; and ($iii$) recovering finite-time ballistic growth of the von Neumann
entropy from integer Rényi
entropies that cross over toward subballistic growth in diffusive
quantum dynamics. In the latter setting, analytic continuation is expected to fail in the long time limit. We illustrate this mechanism with a physically motivated two-sector model, where the asymptotic separation between von Neumann and higher-Rényi growth is accompanied by a zero of $\text{Tr}\rho^z$ pinching the real axis at $z=1$, thereby producing a first-order Rényi phase transition.
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All authors Ayush Raj, Akash Vijay, Hong-Chen Jiang, Laimei Nie