Chemical Physics
A basis-set-free reference for the exact exchange-energy density and functional development
Alastair J. A. Price
The exact local exchange-energy density, obtained from the Slater potential of the Hartree-Fock exchange hole, is a central ingredient of Becke's B05 and B13 functionals and of many other local hybrids. It is usually evaluated in a Gaussian basis, so the local quantity retains a pointwise basis-set incompleteness error. We describe here a basis-set-free numerical code that solves the Kohn-Sham problem on real-space grids for atoms, diatomics, and polyatomics, and returns the exact local exchange-energy density together with the density, its derivatives, the kinetic-energy density, and the reverse Becke-Roussel hole quantities. Reconstructed from the published record of Becke's non-public NUMOL code, AXEL reproduces numerical atomic references through krypton, scalar-relativistic uranium orbital energies, and Becke's diatomic spectroscopic constants. We then extend the original local-density numerical framework to generalized-gradient and hybrid functionals. Comparisons with the independent adaptive-multiwavelet code MRChem give sub-millihartree agreement for Hartree-Fock and PBE0. The same calculations agree with large Gaussian-basis references to a similar level of accuracy. Atom-centred eXact Electronic Limit (AXEL) is intended as both a basis-set-free numerical reference and a platform for exchange-hole-based density-functional development.
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Astrophysics of Galaxies
The connection between massive galaxies and their dark matter haloes from $z=0.25$ to $z \sim 4$ from the combined COSMOS, XMM-LSS and ECDF-S fields
Natalia Stylianou, Matt J. Jarvis, Rohan G. Varadaraj et al. (+4 more)
Understanding how
galaxies populate and grow within dark matter
haloes is essential for linking the observed
evolution of
galaxies to the hierarchical growth of structure. We present a
galaxy clustering analysis using optical and near-infrared data from the UltraVISTA and
VIDEO surveys covering $9.3$ deg$^2$ across the COSMOS, XMM-LSS and ECDF-S fields, $\sim 5\times$ larger than previous comparable studies, providing sufficient volume to determine the
halo occupation of the most massive
galaxies to $z\sim 4$. We measure the angular two-point correlation function for stellar-mass-selected
galaxies over $0.25<z<4$ and by combining the three fields, we reduce the
cosmic variance by a factor of $\sim2$ compared to the individual fields. The stellar-to-
halo mass ratio peaks at a
halo mass of $M_{h}\approx10^{12} {\rm M}_{\odot}$ and is a maximum at $z\sim 1$. For the most massive
galaxies, the peak
halo mass ($M_{h}^{\rm peak}$) increases from $z=1\rightarrow 0$, while the peak stellar mass in such
haloes remains approximately constant, indicating that at $z<1$ massive
galaxy formation becomes less efficient. We also find a steady increase in the satellite fraction since $z\sim 1$, from which we infer that massive
halos continue to grow hierarchically while their central
galaxies experience suppressed stellar-mass growth. We suggest this is due to the central massive
galaxies having their growth controlled by feedback from active galactic
nuclei feedback, likely from low-power
stochastic radio emission.
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All authors Natalia Stylianou, Matt J. Jarvis, Rohan G. Varadaraj, Peter W. Hatfield, Joel Hamlett, Catherine L. Hale, Tariq Yasin
High Energy Physics (Phenomenology)
Two-loop $gg\to AA$ amplitudes near threshold and the double parton scattering singularity
Arunima Bhattacharya
The two-loop amplitudes for pseudoscalar pair production in gluon fusion, $gg\to AA$, with each pseudoscalar emitted from its own effective gluon vertex, are known in closed form, but large cancellations near threshold obscure their analytic structure. We expand the IR-finite amplitudes in the pseudoscalar velocity $\beta_A$ through $\beta_A^6$ at fixed scattering angle. All inverse powers of $\beta_A$ and the odd powers through $\beta_A^5$ cancel, and at leading power the angular dependence enters only through $\ln(2p_T/m_A)$. We identify this logarithm with the double parton scattering (DPS) singularity: with the overall constant fixed at threshold, the factorisation formula of Gaunt and Stirling reproduces the velocity dependence of its one-loop coefficient in the forward limit to $3\times10^{-15}$, and a one-loop $gg\to HH$ analysis confirms the corresponding CP-even weight. At two loops the equal-helicity amplitude grows as $\ln^3p_T$, with the leading logarithmic ratio of planar $\mathcal N=4$ super Yang-Mills theory, while the opposite helicity amplitude, which has no one-loop DPS logarithm, grows as $\ln^2p_T$. In the finite virtual correction, relative to the squared tree amplitude, the highest logarithm at order $\alpha_s^2$ is $-\tfrac{7}{64}\alpha_s^2N_c^2\ln^2(2p_T/m_A)$. For $\beta_A\leq0.2$ the series reproduce the unexpanded amplitudes with relative errors of at most $6.77\times10^{-5}$ at the tested points; they provide this two-loop contribution to the hard function for soft-gluon resummation of the pair invariant-mass distribution near $m_{AA}=2m_A$ and are released with code for their numerical evaluation.
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Solar and Stellar Astrophysics
SPICY 30021: an embedded bona fide FUor with a mid-infrared precursor
Zhen Guo, Calum Morris, Vitor Fermiano et al. (+37 more)
Unstable mass
accretion in young stellar objects (YSOs) often leads to observable outbursts, which play a key role in stellar mass assembly during pre-main-sequence
evolution. The highest-amplitude, longest-duration events are classified as FUors. Until recently, only 50 FUor events had been confirmed. Many occur in embedded protostars, which are difficult to monitor in optical surveys. We present photometric and spectroscopic observations of SPICY 30021, an eruptive young
star discovered in the mid-infrared (MIR) NEOWISE time series. We aim to construct its spectral energy distribution and characterise its eruptive nature. We compiled multi-wavelength photometric time series from NEOWISE, VVV and VVV-RENEW, and obtained photometric and spectroscopic observations during the outburst with SOAR, Magellan and VLT, including data from the ESO public survey VVVX-GalCen. We identified the outbursting source, separated it from nearby companions, and estimated the line-of-sight extinction from spectroscopic features. Stellar parameters were constrained using radial velocity, proper motions and stellar
evolution models. SPICY 30021 is an optically obscured FUor with a total interstellar and circumstellar extinction of Av = 12.5 mag. Its spectrum closely resembles those of classical FUors. Multiple methods yield a distance of 1.7+_0.4 kpc. Its
accretion luminosity is Lacc = 32 L_sol, moderate among FUors. Quiescent near-infrared photometry is consistent with a young 0.9 M_sol progenitor, although the mass depends on the adopted model and distance. We confirm SPICY 30021 as a bona fide FUor event. Its MIR precursor suggests an outside-in triggering mechanism.
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All authors Zhen Guo, Calum Morris, Vitor Fermiano, Carolina Lizana-Vidal, Aldo Aliaga, Javier Osses, Felipe Navarete, Philip Lucas, Roberto K. Saito, Adolfo Carvalho, Vardan Elbakyan, Carlos Contreras Peña, Koshvendra Singh, Min Fang, Philipp Weber, He Zhao, Tigran Yu. Magakian, Tigran A. Movsessian, Matias Gomez, Dante Minniti, Valentin Ivanov, Maria Gabriela Navarro, Sara Federle, Ilaria Petralia, Alonso Luna, Jesus Corral-Santana, Elisa R. Garro, Sean D. Points, Cesar Briceño, Zenghua Zhang, Radostin Kurtev, Jura Borissova, Jose G. Fernández-Trincado, Javier Alonso-García, Claudio Cáceres, Casmir O. Obasi, Daniela Galdeano, Laura Baravalle, Teresa Giannini, Zhikai Zhu
Mesoscale and Nanoscale Physics
Topological superconductivity in layered d-wave altermagnetic metals
Yijie Mo and Zhongbo Yan
We investigate multilayer d-wave altermagnetic metals with odd-parity helical p-wave pairing. In the minimal bilayer system, interlayer tunneling reconstructs the
spin-split Fermi surfaces and generates two layer-hybridized sectors with distinct effective chemical potentials. Without Rashba
spin-orbit coupling (RSOC), the emergent mirror
symmetry and subsystem chiral
symmetry stabilize phases with different numbers of helical Majorana edge-mode pairs and additional counterpropagating pairs, jointly characterized by the mirror Chern number and the winding numbers defined along high-
symmetry lines. The combination of RSOC and the altermagnetic exchange field gaps out the helical Majorana pairs while, in a certain parameter regime, leaving another pair of counterpropagating Majorana edge modes gapless, giving rise to second-order topological phases with isolated or twofold Majorana corner modes, as well as a hybrid-order phase in which gapless Majorana edge modes coexist with Majorana corner modes. We identify a layer
symmetry that elucidates the physical origin of these phases. For an arbitrary N-layer system, such a
symmetry naturally arises from the interlayer-coupling
matrix, allowing N-fold Majorana corner modes to emerge when all layer-hybridized sectors enter the nontrivial second-order regime. Our results establish the interplay among the layer degree of freedom, odd-parity pairing, and Fermi-surface configurations as a controllable route to engineering topological superconductivity in layered altermagnetic systems.
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High Energy Physics (Theory) · Cross-listed from math.AT
On the work of Graeme Segal
Daniel S. Freed
This is my written Laudatio for Graeme Segal on receiving the Chern Medal at the 2026 International Congress of Mathematicians. I make some general remarks about Segal's qualities as a mathematician. Then I discuss the origins of his work on classifying spaces of categories and Gamma-spaces. In the last section I describe his axiom system for Wick-rotated
quantum field theory and some of his subsequent work in the area. Of course, this is necessarily only a small slice of Segal's total research output.
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Solar and Stellar Astrophysics
First L-type substellar object discovered in the vicinity of the embedded cluster NGC 2023
Styliani Tsilia, Carlos Dominguez-Tagle, Maruša Žerjal et al. (+8 more)
We present the first substellar object in a
star-forming region spectroscopically confirmed with Euclid, namely J054158.70-021031.4. This young and faint source is located close to the embedded open cluster NGC 2023. It has a spectral type of L3, a reddening of Av = 3 mag, proper motion consistent with the nearby cluster NGC 2024, and a magnitude of $\sim24.5$ in the Euclid optical band. At the distance of 403 pc, its inferred mass lies close to the planetary-mass boundary. We discovered the object by searching for ultracool dwarf candidates in the Euclid Early Release Observations. The search was based on photometric criteria, followed by the analysis of slitless 2D spectro-images in order to distinguish features that indicate the nature of these objects. This work demonstrates the potential of Euclid to unveil previously hidden populations of very low-mass objects, located in obscured regions where
star formation is ongoing.
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All authors Styliani Tsilia, Carlos Dominguez-Tagle, Maruša Žerjal, Eduardo L. Martín, Hervé Bouy, Nafise Sedighi, Sara Muñoz Torres, Nikola Vitas, Khalid Barkaoui, Nicolas Lodieu, Jerry J.-Y. Zhang
Mesoscale and Nanoscale Physics
Nanoscale Mapping of Strain-engineered Excitons in Monolayer WSe$_2$
Anna S. Roche, Nicholas V. Proscia, Paul D. Cunningham et al. (+12 more)
Excitons in monolayer transition metal dichalcogenides (TMDs) are highly sensitive to external stimuli, allowing control of resonance energies and lifetimes through electric and
magnetic fields,
heterostructures, moire potentials and mechanical strain. Observations of single-
photon emission (SPE) near sample edges, wrinkles, and strained nanobubbles have motivated strain-engineering aimed at realizing localized emitters in 2D materials. The origin of these emitters remains unclear and prior studies have relied on far-field spectroscopy with strain profiles inferred separately through topography, limiting direct correlation between local strain and excitonic response. We directly probe strain-modified excitonic spectra in monolayer WSe$_2$ using cryogenic scattering-type scanning near-field optical microscopy (s-SNOM). We compare two strain-engineering techniques, nano-indentation and patterned substrates, used to produce SPEs. At 9 K, we spatially resolve
exciton resonance shifts with sub-diffraction limit resolution, simultaneously measuring near-field optical response and topography. We observe that strain transferred from nano-indentation into a deformable
polymer substrate differs from that produced by draping TMDs over patterned dielectric pillars. Adhesion and tearing during plastic deformation drive a compressive
exciton blueshift, while draping produces dominant tensile strain. Comparing the strain model results to the experimentally observed energy shifts shows that the nano-indentation strain is over an order of magnitude smaller than previously inferred, due to puncturing of the fragile monolayer, whereas pillar-strained devices remain intact under more modest strain. These differences suggest SPE arises from complex, strain-mediated interactions rather than simple confinement potentials, establishing s-SNOM as a powerful probe of
quantum emission in strained 2D materials.
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All authors Anna S. Roche, Nicholas V. Proscia, Paul D. Cunningham, Kathleen M. McCreary, Dante J. O'Hara, Hsun Jen Chuang, Cory Cress, Collin Sanborn, Samuel W. LaGasse, Jose J. Fonseca, Jeremy T. Robinson, Takashi Taniguchi, Kenji Watanabe, John R. Schaibley, Brian J. LeRoy
Mathematical Physics
Anomalies, higher symmetries, and homotopy theory I: crossed precosheaves and a nonabelian Cech construction
Anton Kapustin and Shixiong Xu
Symmetries of a
quantum field theory or a
quantum lattice model are expected to be described not by a group but by a homotopy type, whose homotopy groups are the higher
symmetry groups and whose Postnikov invariants encode 't Hooft anomalies. We propose a homotopy-theoretic definition of 't Hooft anomalies based on the structure of localized
symmetries in the operator-algebraic approach. The input is a crossed precosheaf: a collection of groups attached to regions of space, equipped with pairings recording that the commutator of two transformations localized in two regions is localized in their intersection. To a crossed precosheaf and a finite family of regions we attach a pointed connected homotopy type, the Cech-Loday classifying space. As the family of regions ranges over finite covers of space, the classifying spaces form a pro-object in the homotopy category. There is a canonical map from the ordinary classifying space of the
symmetry group to this pro-type. Composing this map with a group action gives an anomaly whose nontriviality obstructs gauging. In favorable cases, the Cech-Loday space is essentially independent of the cover. In such cases, the homotopy fiber of the canonical map is a candidate for the classifying space of the higher group of
symmetries. We give examples of crossed precosheaves arising from gauge transformations in continuum field theory and from
quantum cellular automata and finite-depth
circuits. For
quantum spin systems in one and two dimensions, our construction recovers the Else-Nayak index and its generalizations to two dimensions.
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General Relativity and Quantum Cosmology
The WDM time-frequency transform in gravitational-wave data analysis II: Evolutionary spectrum and noise covariance
Aaron D. Johnson, Katerina Chatziioannou and Robert Rosati
Noise cannot be treated as stationary over the timescales required for upcoming gravitational-wave detectors, minutes for ground-based and months for space-based detectors. Nonstationarity leads to a non-diagonal frequency-domain noise covariance
matrix, thus motivating a shift to the time-frequency domain. We introduce evolutionary power spectra for describing nonstationary noise in the Wilson-Daubechies-Meyer time-frequency basis. Under the framework of oscillatory processes, we show that, to leading order in the ratio of the Meyer filter and the nonstationarity timescales, the evolutionary spectrum is a power-frequency distribution that can be estimated from a single noise realization. We derive the corresponding noise covariance
matrix and show that it is band tri-diagonal, like its stationary counterpart. The exact covariance to all orders is positive semi-definite by construction and dense depending on the noise. We further derive the optimal tiling of the time-frequency plane that minimizes the error of a diagonal covariance approximation and show that coarse-graining the plane suppresses correlations quadratically. Using simulated data with a LISA Galactic foreground and a drifting powerlaw spectrum, we show that the stationarity approximation leads to signal-to-noise ratio loss and severely biases inference. For realistic LISA data, approximating the covariance as diagonal in the Wilson-Daubechies-Meyer domain is accurate for the narrow-band analysis of a single resolved Galactic binary, but insufficient for a broad-band analysis. Finally, we provide mitigation strategies for the wraparound correlations induced across the data time edges whenever the spectrum differs between the start and the end of the data.
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Cosmology and Nongalactic Astrophysics
Kinetic Theory of the EFTofLSS : A Halo-Based Approach
Om Kishor Hebbar, Caio B. de S. Nascimento and Arka Banerjee
The Effective Field Theory of Large Scale Structure (EFTofLSS) provides a coarse-grained description of the non-linear gravitational clustering of dark matter, in which the effects of short-scale physics are encoded in an effective stress tensor and a set of counterterms. In this work, we develop a framework to investigate the physical origin of these counterterms by relating the effective stress tensor to the dynamics of individual dark matter
halos in cosmological N-body simulations. We find that
halo accretion contributes to the trace of the
halo-based effective stress tensor, contributing to the background pressure and effective sound speed, while anisotropic
accretion generates the traceless part, consequently contributing to the shear viscosity. For the
halo population with $M_\mathrm{vir}>10^{12}\,M_\odot/h$, we find that
halos account for $\sim\!95\%$, $\sim\!85\%$, and $\sim\!70\%$ of the full box background pressure, effective sound speed, and shear viscosity, respectively, depending on the EFT cutoff scale. The contributions to the counterterms are dominated by cluster-scale
halos, $M_\mathrm{vir} \sim 10^{14} - 10^{15}\,M_\odot/h$ and
halos with larger inflow rates, supporting an interpretation in terms of
accretion-driven, out-of-
equilibrium dynamics. Our results provide a short-scale, kinetic-theory interpretation of the EFTofLSS counterterms and establish a framework for connecting the properties and dynamics of short-scale structures to physics-informed priors for large-scale cosmological observables.
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Instrumentation and Methods for Astrophysics
jax-SNANA: A GPU-accelerated Supernova Framework for the SBI Era
Matthew Grayling
We present jax-SNANA, a JAX reimplementation of the
supernova analysis framework SNANA. jax-SNANA enables GPU-accelerated transient simulations and light curve fitting,
supernova standardisation and cosmological inference. Running in single precision on an NVIDIA A100 GPU, jax-SNANA simulates more than 100,000 LSST-observed
supernovae per second and fits 5,000 light curves per second after JIT compilation, a two orders-of-magnitude increase over current tools, essential for analysing samples at the scale expected from LSST. jax-SNANA currently supports the SALT and BayeSN spectral energy distribution (SED) models as well as physical models from redback-jax and a variety of SN SED templates; light curve fitting is supported with both photometric and spectroscopic
redshifts. We fully validate the accuracy of jax-SNANA by comparing to SNANA, finding excellent consistency between the two across a variety of tasks. The code provides a modular JAX end-to-end
supernova cosmology pipeline, user-extensible to support new features including different SED templates and photometric classification
algorithms. jax-SNANA has been designed with future applications of simulation-based inference in mind, providing fast simulations and enabling fully compiled on-the-fly simulations to be generated within the training loop of downstream SBI tasks. jax-SNANA extends beyond SNANA by supporting simulations of generic SN-host
galaxy relationships and multiple sub-populations of events, for example originating from young and old progenitors. jax-SNANA is publicly available at https://github.com/mattgrayling/jax-snana and installable through pip.
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Materials Science
Electron-Mediated Phonon Polaritons in Quantum Cavities
Mattia Udina, David Hagenmüller and Indranil Paul
Phonon-
photon coupling in
quantum materials is commonly treated as an effective direct interaction, neglecting the crucial role played by electrons. Here we develop a gauge-invariant theory of cavity
phonon polaritons that captures electronic screening, dissipation, and hybridization. We show that screening can suppress polariton formation in metals, severely constraining cavity control of
phonon-mediated superconductivity. By contrast, interband electronic resonances in time-reversal-symmetric gapped systems can strongly enhance
phonon-
photon coupling, enabling robust polariton formation down to the monolayer limit despite electronic absorption. We illustrate these effects in NbSe2, hBN, and gapped
graphene. Finally, we show that gauge invariance enforces
photon decoupling from a critical soft
phonon, establishing a general no-go mechanism for
photon condensation.
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Astrophysics of Galaxies
The convective-transition gap in 47 Tucanae with JWST
M. Scalco, L. R. Bedin, M. Libralato et al. (+3 more)
We report the detection of the convective-transition gap along the lower main sequence (MS) of the Galactic globular cluster (GC) 47 Tucanae using deep James Webb Space
Telescope (JWST) observations. We analyse the stellar luminosity function (LF) in the vicinity of the gap location using two independent colour-magnitude diagrams (CMDs). In both cases, the LF is characterised by a narrow gap followed by a discontinuous increase in the stellar number counts, and presents an overall morphology qualitatively consistent with that reported in previous studies. By modelling the observed LFs with an empirical likelihood model, we estimate the statistical significance of the observed feature. Additional JWST passbands exhibit similar signatures, providing further evidence for the presence of a discontinuity.
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All authors M. Scalco, L. R. Bedin, M. Libralato, M. Griggio, E. Vesperini, R. Gerasimov
General Relativity and Quantum Cosmology
The Forgetful Black Hole: Memory Burden and Hysteresis in Hawking Evaporation
Yen Chin Ong
The
memory-burden scenario of black hole evaporation proposes that Hawking emission may become increasingly suppressed as maintaining stored
quantum information becomes dynamically costly. In this work, we revisit this scenario and investigate the conditions under which information retention can produce a genuine dynamical burden. We derive general scaling conditions for incremental
memory accumulation at a fixed fractional mass loss and establish a conditional no-go result:
entropy-suppressed, zero-mean deposits with subextensive integrated correlations cannot produce an order-one luminosity modification through unamplified accumulation and bounded feedback. We identify three essential requirements for dynamical
memory: a record of the past must be written, retained, and coupled back to subsequent evaporation. We illustrate these requirements with concrete toy models that exhibit either a prolonged but finite black hole lifetime or an asymptotically approached finite-mass state (an effective remnant). We further distinguish kinetic-
memory, thermodynamic-
memory, and spectral-
memory sub-categories of possible
memory-burden mechanisms. In particular, we demonstrate that an independently evolving
memory variable can generate evaporation-
accretion hysteresis, such that a black hole returning to the same mass may possess a different retained
memory and consequently a different luminosity. This history dependence may have implications for primordial black hole phenomenology. Finally, we briefly discuss the possibility of "merger rejuvenation", in which black hole mergers reorganize or reset the effective
memory state.
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Solar and Stellar Astrophysics
The mass functions of multiple stellar populations in 47 Tucanae
M. Scalco, J. Bruce, E. Vesperini et al. (+1 more)
We used a combination of James Webb Space
Telescope (JWST) and Hubble Space
Telescope (HST) observations to investigate the mass functions (MFs) of the different stellar populations in the globular cluster (GC) 47 Tucanae (NGC 104) over a wide stellar-mass interval. We identified the multiple populations along the lower main sequence using only JWST photometry and, in particular, colour combinations sensitive to variations in oxygen abundance. We derived the MFs of the first- and second-population (1P and 2P)
stars separately and found that in the low-mass regime, the present-day MF of the 1P population is significantly steeper than that of the 2P population, which appears nearly flat. We also present the results of a dynamical model showing that this behaviour requires a different initial mass function (IMF) for the 2P and the 1P populations in the 0.1-0.4 solar masses mass range, thus providing a new fundamental constraint for the study of the
star formation of multiple populations in GCs.
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All authors M. Scalco, J. Bruce, E. Vesperini, L. R. Bedin
Solar and Stellar Astrophysics
JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit
M. Scalco, R. Gerasimov, L. R. Bedin et al. (+4 more)
We present the first results of a series of studies based on JWST observations of the globular cluster 47 Tucanae (47 Tuc, or NGC 104) obtained with NIRCam. By combining new data with earlier JWST observations, we derive high-precision proper motions (PMs) over a multi-year baseline (of ~3 years) and construct a clean sample of cluster members extending to very faint magnitudes (F444W~24.25 mag, corresponding to ~0.077 solar masses, slightly above the estimated hydrogen-burning limit of 47 Tuc, ~0.074 solar masses) along the main sequence (MS). We investigated the presence of the low-mass MS kink previously identified in 47 Tuc using the new F090W and F444W photometry. No significant signature of the feature is found using these filters, consistent with its proposed physical interpretation as a consequence of the transition in carbon chemistry toward a methane-dominated
equilibrium in very low-mass
stars. A comparison with theoretical isochrones indicates that the stellar population near the bottom of the MS is likely dominated by oxygen-poor
stars, in agreement with previous findings. Using artificial-
star tests, we quantify the completeness of our sample and show that the requirement of PM-based membership significantly limits the detection of the faintest objects, indicating that current JWST observations of 47 Tuc are not sufficiently deep to reliably trace the cluster's brown dwarf cooling sequence. The mass function (MF) of 47 Tuc shows a structured behaviour, with a break at ~0.15 solar masses not associated with the onset of convection, and a mild but systematic radial variation consistent with mass segregation. Our analysis indicates that the MF shape in this mass regime is more complex than a simple power-law description. This feature in the MF may point to a presently unrecognised mechanism affecting the formation or dynamical
evolution of low-mass
stars in globular clusters.
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All authors M. Scalco, R. Gerasimov, L. R. Bedin, E. Vesperini, M. Griggio, D. Nardiello, J. Anderson
Quantum Gases
Full-Continuum Ultrafast Quantum Gas Microscopy
Andrea Litvinov, Clemens Ulm, Eva Casotti et al. (+3 more)
Quantum gas microscopy provides single-shot access to many-body configurations, but their microscopic reconstruction has so far largely relied on a predefined discrete spatial basis during fluorescence readout. Here we realize ultrafast atom-resolved fluorescence microscopy of an ultracold $^{162}$Dy gas directly in continuous space, with all external confinement removed during imaging. Exploiting the large mass and broad optical transition of dysprosium together with a high numerical aperture in-
vacuum objective, we detect single atoms within $4\,\mu\mathrm{s}$ while maintaining an effective point-spread function with a full width at half maximum of $254.8(3)\,\mathrm{nm}$, and an isolated single-atom classification fidelity of $99.72(3)\%$. We use the measured single-atom response to construct a statistical configuration-inference model that recovers atomic positions and multiplicities, coming from overlapping atoms, directly from single fluorescence snapshots. Benchmarking our model on Monte-Carlo generated images shows a total reconstruction fidelity of $98.7\%$. Our approach extends
quantum gas microscopy beyond predefined detection
lattices, enabling atom-resolved measurements of counting statistics and higher-order spatial correlations directly on the intrinsic length scales of continuum many-body systems.
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All authors Andrea Litvinov, Clemens Ulm, Eva Casotti, Gerard Solà Berga, Manfred J. Mark, Francesca Ferlaino
High Energy Physics (Theory)
Monopoles on the edge
Stefan A. Kurlyand
Quantum M2-brane instantons are studied in eleven-dimensional Freund-Rubin backgrounds. The construction uses the identification of the Calabi-Yau cone over the Sasaki-Einstein
manifold $\mathrm{SE}_7$ with the
geometric branch of the abelian moduli space of the dual superconformal field theory. A class of BPS cycles in $\mathrm{SE}_7$ wrapped by M2-branes is identified as links of two-dimensional holomorphic cones whose coordinate rings contain BPS monopole operators. The algebraic structure and R-charge assignment on the moduli space further allow the computation of both the classical exponents and one-loop partition functions of the corresponding M2-brane instantons. Several three-dimensional superconformal field theories are analysed explicitly, and the relation to the corresponding localisation
matrix models is discussed.
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General Relativity and Quantum Cosmology
Black Hole Fine Structure
Adrian Ka-Wai Chung, Richard Dyer, Tomasz Kinowski et al. (+1 more)
In General Relativity, axial and polar black-hole perturbations share identical quasinormal-mode spectra, a property known as isospectrality. New physics can break this degeneracy, producing a spectral splitting analogous to atomic fine structure. We perform a theory-agnostic search for such splitting in gravitational-wave observations. We find no evidence for isospectrality breaking and place a combined $90\%$ upper limit of $<28.5\%$ on the relative frequency splitting. We map these constraints onto several modified-
gravity theories, constraining the coupling-lengths to be $\lesssim 28\,\mathrm{km}$.
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All authors Adrian Ka-Wai Chung, Richard Dyer, Tomasz Kinowski, Christopher J. Moore
Plasma Physics
Coulomb collision operator
R. D. Hazeltine
Properties of the Coulomb collision operator that have been found useful in
plasma kinetic theory and
plasma transport theory are gathered and reviewed, with derivations. The use of velocity-space coordinates appropriate to a magnetized (drift-kinetic)
plasma is emphasized. Little of the material is new, although the derivations may be more detailed than is customary.
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High Energy Physics (Theory)
Thermal Giant Graviton Expansion
Kasia Budzik and Atul Sharma
We construct giant graviton expansions of the thermal and $(-1)^F$-graded partition functions of $\mathcal{N}=4$ and $\mathcal{N}=1$ super Yang-Mills theories at zero 't Hooft coupling. These observables are generically non-BPS and do not admit a direct bulk interpretation in a supergravity regime. Instead, we exploit the corresponding self-dual theories, which arise as chiral zero-coupling limits and admit twistor string holographic duals. We apply a quiver generalization of Murthy's expansion motivated by twistor strings. Notably, we obtain expansions at both finite and infinite $N$. We reproduce the terms in these expansions from bulk closed string and D-brane sectors, identifying the nonperturbative corrections with D-instanton/anti-D-instanton pairs. At infinite $N$, resumming the D-instanton sectors reproduces the Hagedorn temperatures of the free gauge theories, providing a microscopic bulk origin for their Hagedorn singularities.
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Cosmology and Nongalactic Astrophysics
Scalar-Assisted Growth of Supermassive Black Holes: Boson-Mass Windows and Observational Constraints
Jorge Castelo Mourelle, Darío Núñez Zúñiga, Saeed Fakhry et al. (+1 more)
We study a phenomenological cosmological model of black-hole growth in which a finite baryonic reservoir and a bosonic scalar cloud feed the black hole simultaneously. The baryonic component accretes through an Eddington-like channel, while the scalar cloud transfers mass through an effective quasibound-state decay rate. Evolving the system directly in
redshift within a flat $\Lambda$CDM background, we scan over $\mu$, $M_0$, $M_{c,0}$, and $M_{b,0}$ to assess whether scalar-assisted
accretion can accelerate the formation of $10^9M_\odot$ supermassive black holes. We find that the scalar contribution is highly selective in parameter space. For the mass scales explored here, scalar transfer is most efficient for $\mu\sim10^{-19}-10^{-16} \mathrm{eV}$, producing rapid cloud depletion and significantly earlier black-hole growth, while outside this interval the
evolution remains mainly baryonic. More generally, this efficient window reflects a preferred range of the dimensionless coupling $\alpha=\mu M_{\rm BH}$ and therefore shifts approximately as $\mu\propto M_{\rm BH}^{-1}$. Comparison with observed
quasar masses and luminosities instead favors lower
boson masses, broadly around $\mu\sim10^{-21}-10^{-20}\mathrm{eV}$. These results are not necessarily in tension, since the
boson mass that maximizes early growth depends on the characteristic black-hole mass and evolutionary stage. This separation between dynamical efficiency and observational compatibility leaves open complementary roles for different bosonic mass scales in supermassive black hole growth and dark-matter phenomenology.
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All authors Jorge Castelo Mourelle, Darío Núñez Zúñiga, Saeed Fakhry, Nicolas Sanchis-Gual
Astrophysics of Galaxies
Substructure-enhanced Collisional Relaxation in Stellar Systems
Jian-Yu Gu, Xiao-Bo Dong and Run-Yu Meng
Two-body collisional relaxation in stellar systems is conventionally estimated using the classical Chandrasekhar theory, in which a subject
star is assumed to be embedded in a homogeneous medium of field
stars and their velocity distribution taken to be isotropic and Gaussian. Real stellar systems, however, can exhibit pronounced spatial and kinematic substructures. We investigate how such substructures – particularly the non-classical spatial inhomogeneity – modify the two-body
diffusion coefficient. We retain
hyperbolic two-body encounters but generalize the encounter calculation by integrating explicitly over the spatial distribution $n(\mathbf{r})$, while evaluating the velocity contribution from the full distribution $f_v(\mathbf{v})$. This yields a separable tensor expression for the
diffusion coefficient. We find that spatial substructure produces the dominant enhancement. The enhancement of the
diffusion coefficient increases systematically as the effective fractal dimension $D_{\rm frac}$ decreases, $\log \zeta_r(D_\text{frac}) \sim \left(1-D_\text{frac}/3\right)^q$ with $q \approx 4.28$. For the observationally motivated case with $D_{\rm frac}\approx 1.5$, the enhancement is moderate, whereas substantially lower fractal dimensions produce much larger enhancements. In contrast, the anisotropic, power-law-tailed, and fractal-like velocity distributions modify the
diffusion coefficient only by factors of order unity. Our representative substructured model yields enhancement ratios $\zeta_r\simeq3.45$ and $\zeta_v\simeq1.33$ when the measured particle-number trends are extrapolated to $N=10^{11}$, corresponding to an overall enhancement of $\zeta\simeq4.6$. Therefore, within the two-body encounter framework and the commonly used separable distribution functions, the enhanced collisional relaxation still has little impact on the mean-field nature of typical galactic systems.
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General Relativity and Quantum Cosmology
Strong-Field Gravitational-Wave Lensing from Ray-Traced Arrival-Time Surfaces
Luka Vujeva, João S. Santos and Brian C. Seymour
The diffraction integral formalism has been greatly successful in describing gravitational wave
lensing effects in scenarios where the wavelength of the signal is comparable to the characteristic length scale of the lens, known as the wave optics regime. However, the assumptions required to construct its integrand break down as the source approaches the strong
gravity region of a black hole lens. In particular, we are interested in the lensed signal from a binary (the source) near a massive black hole (the lens). We present a new formalism for obtaining low frequency corrections to sources being lensed in the strong field regime of
gravity by leveraging the fact that null geodesics obey the Hamilton–Jacobi equations. In doing so, we are able to construct a time delay surface without relying on the thin lens approximation, and solve the diffraction integral for the resulting surface directly. For a stationary source at $10M$, deep in the strong field regime, when comparing the results with a relativistic wave scattering model, we find $6.5\%$ and $0.3\%$ agreement in the peak amplification and first diffractive fringe, respectively. Furthermore, we find a $< 1\%$ agreement with the amplitude of the point mass lens with a source at $10^4 M$ in the weak field, but noticeable dephasing between the peaks of the amplification function at higher frequencies. This work allows for clean interpolation between otherwise separate regimes, valid for sources from $\sim 6M \to \infty$. It provides a transparent, physically motivated framework for computing beyond-
geometric optics
lensing effects in the strong field regime.
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Quantum Physics
Instability of Markov chains under infinitesimal coherent dissipation
Amir-Reza Negari, Yijian Zou and Timothy H. Hsieh
Under local Lindbladian
evolution, the growth of conditional mutual information and its associated Markov length scale is not limited by Lieb-Robinson bounds, yet it has been unclear how quickly the Markov length can increase. We show that an arbitrarily short, strictly local Lindbladian can generate infinite Markov length from a product state. We also construct strictly local Lindbladians that converge rapidly to steady states with algebraically decaying conditional mutual information. Despite their long-range conditional correlations, the states we construct are local reversibly connected to a product state by sublinear depth
circuits. Thus infinite Markov length does not imply slow relaxation nor obstruct phase stability when suitably defined.
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Earth and Planetary Astrophysics
Thermodynamically consistent equation of state tables for use in giant planet and brown dwarf interior modeling
Emily Sandford and Yamila Miguel
Equation of state (EOS) tables used in giant
planet modeling exhibit regions of strong thermodynamic inconsistency, or disobedience to the first law of thermodynamics. These generally result from smooth interpolation over physical discontinuities or between thermodynamic sub-domains governed by different physical models. The effect of thermodynamic inconsistency on structure models of
planets evolved with these EOS has never been studied in detail, although it is understood to introduce spurious sources or sinks of energy or
entropy in the models, leading to inaccuracies. Here, we present a method for improving the thermodynamic consistency of an existing EOS table, based on constructing a Helmholtz free energy $F(\rho,T)$ covering the EOS domain and deriving all the other necessary EOS quantities from it. This method produces EOS tables with roughly thousandfold better thermodynamic consistency across the EOS domain of interest, as quantified by three thermodynamic consistency metrics derived from the first law. We also present a controlled experiment comparing giant
planet models evolved with MESA using the original EOS and the $F$-derived, thermodynamically consistent versions, and find that the models can differ by up to $5\%$ in radius at an age of 5 Gyr, and by up to $25\%$ in luminosity at earlier stages of
evolution; thermodynamic consistency is thus an especially important consideration for characterising young directly imaged
planets. We present the $F$-derived, thermodynamically consistent versions of the tables for download at \href{https://doi.org/10.5281/zenodo.21103561}{https://doi.org/10.5281/zenodo.21103561}, along with example MESA inlists to reproduce our
evolution models.
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Cosmology and Nongalactic Astrophysics
Forecasting a Cosmological 21 cm Stacking Detection with Early HIRAX Data
Pascal Hitz, Devin Crichton and Alexandre Refregier
Post-reionization 21 cm intensity mapping provides a powerful technique for efficiently mapping the Universe on large scales. The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a compact and highly redundant
radio interferometer designed to exploit this technique. We present a forward modelling pipeline for forecasting a statistical detection of the cosmological 21 cm signal with HIRAX through cross-correlation with an external source catalogue. We simulate the cosmological signal using the
halo model and propagate it, together with Galactic and extragalactic foreground emission and instrumental noise, through a model of an early-stage 36-dish HIRAX array configuration. We generate simulated visibilities, apply delay-domain foreground filtering, and construct cross-correlation-ready ringmaps for an observing time of 120 days with a single zenith pointing over the frequency range from 700 to 800 MHz, covering approximately 3547 deg$^2$ of the sky. We investigate the prospects for an early statistical signal detection by stacking these ringmaps at the known three-dimensional positions of sources from an overlapping external survey. Specifically, we quantify how delay-domain foreground filtering, the number of stacking sources, catalogue completeness, and source
redshift uncertainties affect the detection significance. We find that
redshift precision is the most critical requirement: while spectroscopic
redshifts with $\sigma_z / (1+z) \sim 0.001$ preserve a significant stacking signal even under realistic foreground filtering and substantial catalogue incompleteness, photometric
redshift uncertainties of $\sigma_z / (1+z) \sim 0.01$ strongly suppress the signal for realistic delay cutoffs. Applying the framework to a Euclid-like spectroscopic
galaxy sample, we recover a minimum signal-to-noise ratio of 11 for our most conservative delay cutoff of 100 ns.
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Mesoscale and Nanoscale Physics
Transmission representation of the Josephson free energy beyond the short-junction limit
Anton R. Akhmerov
Beenakker's formula, $U(\varphi)-U(0)=\Delta\sum_n\bigl(1-\sqrt{1-\tau_n\sin^2(\varphi/2)}\bigr)$, expresses the zero-temperature energy-phase relation of a short Josephson junction through its normal-state transmission
eigenvalues. We generalize this transmission representation beyond the short-junction limit and express the phase-dependent free energy of a time-reversal-symmetric $s$-wave junction as a Matsubara sum over channels with frequency-dependent transmissions. The representation constrains the small-phase expansion of the free energy. In particular, we prove that the normalized ratio of its quartic and quadratic coefficients satisfies $-1\le\alpha_r\le7/80$ at finite temperature. We also construct a four-site junction with $\alpha_r>0$, which disproves the conjectured upper bound $\alpha_r\le0$. So that these results can be trusted without repeating the derivations, every numbered equation is formally verified in the Lean proof assistant.
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Astrophysics of Galaxies
A Nonlinear General Implicit Runge-Kutta Integrator for Multifluid Charged Dust and Gas
Mengxuan Chen, Hui Li, Chong-Chong He et al. (+3 more)
Charged dust in magnetized gas is subject to aerodynamic drag and the Lorentz force, both of which can be difficult to model numerically in a fluid simulation where their characteristic timescales are shorter than the timestep set by the Courant condition. We present a two-stage general implicit Runge-Kutta (GIRK) source integrator for multifluid charged dust coupled to an ideal magnetohydrodynamic (MHD) gas, implemented in the open source GPU-accelerated quokka code. Drag and Lorentz forces are advanced together in one implicit source update, avoiding errors in the terminal drift that can arise when the two forces are advanced in separate substeps. The timestep is compared with a drag-Lorentz timescale to select between resolved and stiff branches. The resolved branch uses Gauss-Legendre coefficients, while the stiff branch uses a coefficient set designed to recover the terminal drift set by the drag-Lorentz balance. We also allow the dust stopping time and charge-to-mass ratio to depend on the evolving state, evaluating them separately at the two implicit stage states and solving the resulting nonlinear stage equations by Picard iteration. The source update conserves total gas-dust momentum, and its computational cost scales linearly with the number of dust species. Tests reproduce the expected drag damping and terminal drift, confirm the predicted gyromotion amplitude and phase errors, demonstrate accurate treatment of state-dependent source coefficients, and recover the expected wave, shock, and instability dynamics in dusty MHD flows.
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All authors Mengxuan Chen, Hui Li, Chong-Chong He, Benjamin D. Wibking, Mark R. Krumholz, Xue-Ning Bai