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Tuesday 29 September

Multiagent Systems

Absorbing State Phase Transitions in Multi-Agent Search

Wenwen Zheng, Yuzhe Yang, Helen Qu et al. (+2 more)

Nontrivial dynamics can emerge in large language model (LLM)-based multi-agent systems, and preliminary evidence exists that formalisms from statistical mechanics can be effective at modeling and predicting such behaviors. In parallel, designing multi-agent communication topology for optimal task-solving is an active research question. In this paper, we focus on predicting the success of multi-agent search tasks using the formalism of absorbing state phase transitions. We first taxonomize search tasks into four types, informed by classical results in combinatorial search. We then theoretically derive a critical communication degree $d_c$, the minimum number of agents each agent can communicate with, above which incorrect hypotheses do not proliferate uncontrollably and the search enters the solved state. Finally, we evaluate frontier LLM-based multi-agent systems on real-world search and discovery tasks, software configuration debugging and physical mechanism discovery, and find that agreement with theory is mixed. LLM agents may not communicate with their neighbors and can develop strategies that are individually beneficial but limits the benefits of collaboration.
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All authors Wenwen Zheng, Yuzhe Yang, Helen Qu, Xin Eric Wang, Haewon Jeong

Astrophysics of Galaxies

Learning Gaia: A Generative Model Trained on the Gaia Data Release 3 Source Catalog

John Soltis

I train a conditional flow matching model on the positions, photometry, and astrometry of $\sim$ 579 million sources from the Gaia Data Release 3 Source Catalog. Using a probabilistic masking scheme during training, I develop a model capable of generating mock Gaia catalog sources with and without partial measurements of real Gaia sources. The model can produce coarse-grained mock Gaia Source Catalogs that reproduce the Milky Way disk and Magellanic Clouds, and can impute photometric and kinematic information. The model fails to reproduce small, distinct subpopulations like $\omega$ Centauri. This model is a necessary step towards a foundation model trained on the entirety of Gaia data products, and provides a blueprint for future work with the upcoming Gaia Data Release 4.
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Computer Vision

Strike a Chord! Modal Kinetic Typography

Maham Tanveer, Jiyeon Han, Nanxuan Zhao et al. (+1 more)

We introduce modal kinetic typography, which animates a vector glyph to express a semantic concept while keeping it legible. Our key idea is to build motion from the glyph's natural vibration modes. Specifically, a finite-element eigenproblem assembled from the vector outline yields the glyph's softest modes, for the whole letter and for each of its parts, allowing it to bend. The problem's zero-energy solutions, i.e., rigid translations and rotations, are applied in closed form to each part, allowing parts to also move as blocks. To animate the glyph, a frozen video diffusion model supervises only the modes' amplitudes and phases. Our modal approach addresses two weaknesses of prior work. Free-form point optimization under video score distillation (SDS) moves each point and frame independently along noisy gradients, tearing the outline and causing jitter. In contrast, our modes are smooth along the outline and driven by a few whole-cycle harmonics, which restricts these gradients to smooth, seamlessly looping motion. On the other hand, structured alternatives rely on skeletons or keypoints from category-specific priors, whereas our modes come from the glyph itself; the only prior is a list naming each letter's moving parts, generated once for the whole alphabet by a language model. In modal kinetic typography, shape and motion are disentangled by construction: a single base outline is sculpted toward the concept, and the modal drive cannot alter it, so a letter can also be animated without being reshaped. Our method produces more articulated and smoother motion than Dynamic Typography and AniClipart at comparable or better concept alignment, with less glyph tearing than Dynamic Typography, and is preferred by human raters, including in a frozen-shape setting where motion alone must carry the concept. Our results were also preferred over Astra (GPT-6) by human raters.
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All authors Maham Tanveer, Jiyeon Han, Nanxuan Zhao, Hao Zhang

Physics and Society

Multi-agent discussion gains less when dissent is withheld

Chand Sahil Mansuri, Xin Wang, Mengying Li et al. (+4 more)

Multi-agent systems of LLMs add discussion to majority voting and are therefore expected to be more capable. However, empirical reports conflict on whether discussion improves accuracy or leads to an incorrect consensus. Here, we introduce a parsimonious model that explains when discussion improves accuracy and when it ends in an incorrect consensus, built from four behaviors repeatedly observed in LLM agents: (1) withholding dissent, (2) internalizing a stated answer, (3) reconsidering after seeing dissent, and (4) correcting toward the correct answer. The model shows that discussion can overturn an incorrect initial majority only when the withholding rate $c$ is below a critical rate $c^* = \gamma/(\gamma + a)$, set by the net correction rate $\gamma$ and the internalization rate $a$. We estimate these rates from conversation logs with a Bayesian method and place LLM teams relative to $c^*$. As the model predicts, the gain from discussion shrinks as withholding rises, across LLMs and on a hidden profile benchmark, HiddenBench, and MedEInst. Instructing agents not to withhold dissent increases this gain. Turning reasoning off also increases the gain, because reasoning raises the internalization rate $a$ and keeps agents from reconsidering a minority answer. These findings reconcile the conflicting reports and identify when discussion outperforms majority voting.
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All authors Chand Sahil Mansuri, Xin Wang, Mengying Li, Bryan Acton, Rory Eckardt, Dhaval Patel, Sadamori Kojaku

High Energy Astrophysical Phenomena

Revealing the accretion disc structure in Changing State AGN: NGC1566

Huimei Wang, Chris Done, Riccardo Middei et al. (+1 more)

NGC1566 is a low mass ($\sim 6\times 10^6M_\odot$) Active Galactic Nuclei (AGN) with unusual large amplitude variabilty in its accretion flow. In the optical it cycles between recurring short bright episodes with strong blue/UV continuum and clear broad line emission, and a much weaker persistent level without strong broad lines, making it a repeating changing-state (CS) AGN. We re-analyse the intensive optical/UV and X-ray monitoring during the 2018 bright flare, showing for the first time the corresponding evolution of the (host galaxy subtracted) optical/UV AGN spectrum as well as the X-ray emission. As seen in other CS-AGN, the strongest spectral evolution is in a UV/soft X-ray component which likely disappears below $0.01L_{\rm Edd}$ while the hot corona and a redder optical/UV component show weaker variability. We show that the red optical emission is likely a composite of the intrinsic and reprocessed emission from the outer disc, together with diffuse continuum from the BLR, and discuss the different signatures predicted by this for continuum reverberation across the changing-state event. The historical lightcurves show repeated changing-state events tied to unusually large amplitude discrete flares in the lightcurve. While these do not appear to be periodic, the behaviour does support previous suggestions that the accretion flow is repeatedly perturbed, perhaps by an intermediate mass black hole companion.
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All authors Huimei Wang, Chris Done, Riccardo Middei, Xue-Bing Wu

Instrumentation and Methods for Astrophysics

An X-ray Extremely wide-field Spectroscopic Surveyor (XESS, or "chess")

W. P. Maksym, M. Ulmer, S. Friedrich et al. (+20 more)

We propose an X-ray observatory, the X-ray Extremely wide-field Spectroscopic Surveyor (XESS, pronounced "Chess") to bring high energy resolution X-ray spectroscopy into the era of synoptic surveys and of time domain and multi-messenger astrophysics (TDAMM). Such an observatory is optimally suited to addressing key elements of the 2020 Decadal Survey on Astronomy and Astrophysics.
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All authors W. P. Maksym, M. Ulmer, S. Friedrich, F. Tombesi, R. Arcodia, S. P. Singam, S. Bongiorno, N. Thomas, M. Elvis, Ming Sun, John ZuHone, M. Lynne Saade, Philip Kaaret, Doug Swartz, Erin Hicks, Ming-Yi Lin, Pallavi Patil, Jimmy Irwin, Shrabani Kumar, Kirtan Dixit, Sudip Chakraborty, Andrea Gnarini, Steven Ehlert

Solar and Stellar Astrophysics

Surveying for Close Binaries among Lithium-rich Giants

Jesús Torres, Sebastián Vilaza-Dallago, Julio Chanamé et al. (+1 more)

One of the possible scenarios usually considered to explain the existence of low-mass red giants with anomalously high lithium (Li) abundances requires the interaction with a close binary companion. If dominant, this enrichment channel predicts a significantly enhanced binary fraction among Li-rich giants relative to Li-normal ones. We aim to constrain the binary interaction hypothesis by using multi-epoch radial velocities (RVs) to measure the close binary fraction of a statistically robust sample of Li-rich giants. We are surveying both red clump (RC) and first ascent red giant (RGB) targets, which allows us to examine potential differences in the binary fraction as a function of evolutionary stage. We are monitoring 70 targets (40 RC and 30 RGB, all Li-rich) using ESPRESSO at the VLT, 57 of which (32 RC + 25 RGB) already have 4 or more visits over a $\sim$7 month baseline; the analysis in this paper is based on the latter. For the targets with RV variation larger than that expected for intrinsic jitter, we use a Monte Carlo analysis to estimate the probability that the observed RV variation is due to a stellar ($P_{SB}$) or sub-stellar ($P_{SS}$) companion. Discounting the 38 targets consistent with stellar jitter, we are left with 11 RC and 8 RGB stars (34% and 32% of the respective sub-samples) with RV variability consistent with the presence of a close companion with an orbital period shorter than 3000 days. Of these 19, 3 can be confirmed as stellar-mass companions. The distributions of $P_{SB}$ and $P_{SS}$ are statistically indistinguishable between the RC and RGB samples. We thus find no evidence so far in our current data for a binary fraction for Li-rich giants (in either evolutionary stage) larger than that expected for a Li-normal population. Extending the RV baseline to probe longer orbital periods will be important to keep exploring the plausibility of this scenario.
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All authors Jesús Torres, Sebastián Vilaza-Dallago, Julio Chanamé, Rafael Brahm

Quantum Physics

When Symmetry Suppresses Magic

A. de Oliveira Junior, Jake Xuereb, Rafael A. Macêdo et al. (+2 more)

Nonstabilizerness is a critical resource for quantum advantage, but evaluating it, especially for mixed states, requires superexponentially many samples in system size, making the problem NP-hard. While symmetries are known to reduce this complexity, it is unclear whether they also restrict the amount of magic. In this work, we provide an explicit example of such a symmetry by proving that the Robustness of Magic (RoM) for N-qubit X-states is at most $\sqrt{3}$. Leveraging this symmetry constraint, we introduce a computationally efficient method to lower-bound the RoM of arbitrary many-body states, demonstrating its utility on the ground states of a spin-1/2 Hamiltonian with system sizes well beyond the reach of exact evaluation. Furthermore, for Hamiltonians whose equilibrium states are X-states, we analytically derive the critical temperature at which magic emerges. Our work shows why certain symmetries constrain magic while others do not, provides a scalable lower-bounding method, and identifies a nontrivial regime where many-body nonstabilizerness is analytically solvable.
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All authors A. de Oliveira Junior, Jake Xuereb, Rafael A. Macêdo, Jonatan Bohr Brask, Rafael Chaves

High Energy Physics (Theory)

Energy Transmission Across Holographic Conformal Interfaces in General Dimensions

Igal Arav, Theodore Bertrand, Shira Chapman et al. (+2 more)

Energy transport across conformal interfaces is universal in two spacetime dimensions, but its higher-dimensional counterpart has remained largely unexplored. In higher dimensions, scattering can depend on additional kinematic data, such as the angle of incidence, and conformal symmetry is far less restrictive. We use gravitational holography to study this problem. For a broad class of AdS$_d$-sliced domain-wall geometries, we derive a closed-form expression for the energy transmission coefficient in terms of the bulk warp factor. Our formula reproduces known two-dimensional holographic results and extends them to arbitrary dimension. Within this class, we establish different aspects of higher-dimensional universality. In particular, we show that the transmission is independent of the incidence angle and of the profile of the incident perturbation. We also derive bounds on transmission controlled by central-charge-like quantities characterizing the number of degrees of freedom of the theories on the two sides of the interface. This provides the first explicit result for reflection and transmission across conformal interfaces in higher dimensions, where no CFT-based results are currently available.
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All authors Igal Arav, Theodore Bertrand, Shira Chapman, Giuseppe Policastro, Sebastian Waeber

Mesoscale and Nanoscale Physics

Hidden Angular Momentum Loop Currents in Symmetric Crystals

Rule Yi, Vincent P. Flynn and Benedetta Flebus

Loop-current order has been invoked to explain unconventional electronic phases, with the crystal lattice usually regarded as a passive host for the underlying collective dynamics. Here we show that circulating currents can originate in the lattice itself, sustained by quantum and thermal fluctuations. We develop a microscopic description of angular momentum exchange that separates transfer between sites from crystalline restoring torques and reveals how circulation can emerge in a symmetry-preserving equilibrium state. In a two-dimensional elastic lattice preserving time-reversal, inversion, and fourfold rotational symmetries, we uncover opposite current loops on neighboring plaquettes while the mean angular momentum vanishes at every site. These currents are sustained by zero-point fluctuations in the phonon vacuum and persist at finite temperature. We trace their origin to directional elastic interactions in locally symmetry-lowered environments, with the higher crystal symmetry organizing the resulting currents into a compensated pattern of circulation. Our results extend the physics of equilibrium loop currents to lattice dynamics, revealing that elastic geometry can organize fluctuations into persistent angular momentum circulation without electronic or magnetic order, external driving, or spontaneous symmetry breaking.
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High Energy Physics (Phenomenology)

Constraints on Complex Electroweak WIMPs from Solar Capture

Juan P. Luengas, Maxim Pospelov and Harikrishnan Ramani

One of the most convincing realizations of particle dark matter is provided by models based on electroweak multiplets. The lightest neutral state of such a multiplet can be a stable Majorana fermion or a real scalar, and its phenomenology is governed by two parameters: the dark matter mass and the mass splitting $\{m_\chi,\delta\}$. The sub-MeV range for $\delta$ is particularly important as it allows for a large inelastic scattering cross section. In this paper, we analyze solar capture, energy loss, and annihilation of scalar and fermionic electroweak multiplet dark matter, generalizing earlier results for the Higgsino to other representations. We find that, while the case of a doublet is somewhat special, higher representations behave in a self-similar way. For the higher multiplets, IceCube results constrain the splitting to $\delta \gtrsim 350$ keV for all dark matter masses up to $100$ TeV. Assuming thermal freeze-out and a Standard Halo Model velocity distribution, this rules out most models of electroweak dark matter as a possible origin of the single high-recoil event reported by the LZ collaboration. We also show that a high-velocity tail in the dark matter distribution, such as that induced by the Large Magellanic Cloud, raises the splitting preferred by the LZ event above the solar bounds for many of the multiplets.
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Earth and Planetary Astrophysics

An Infant Sub-Saturn in Scorpius-Centaurus

Gurmeher Kathuria, Luke G. Bouma, Andrew W. Boyle et al. (+25 more)

We report the discovery and validation of TIC 88297141 Ab, a transiting planet orbiting a pre-main-sequence M dwarf (0.31 solar masses, 0.74 solar radii) in the Scorpius-Centaurus OB association. Group membership implies an age of $15.6 \pm 1.6$ Myr, supported by lithium and isochrone age-dating. We detected the TESS transits using a custom pipeline designed for variable stars and used ground-based photometry (LCO/Swope and LCOGT/Sinistro) to confirm the on-target nature of the signal. Our global fit of the transits and stellar activity gives an orbital period of 4.64 days and a planet radius of $7.21 \pm 0.32$ Earth radii (0.64 Jupiter radii). The star has a comoving M-dwarf companion (0.4 solar radii) at a projected separation of $260$ au; speckle imaging (Gemini-S/Zorro) reveals no additional stellar companions, and radial velocities from Magellan/PFS are consistent with stellar activity, giving $M_p \sin i < 4.7$ Jupiter masses at $2\sigma$. A statistical validation analysis yields a false positive probability of $10^{-5}$, validating the planet. A mass measurement will determine whether TIC 88297141 Ab is a low-density super-puff, like other comparably sized planets at these ages, or an unusually massive planet for its radius.
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All authors Gurmeher Kathuria, Luke G. Bouma, Andrew W. Boyle, Roberto Tejada Arevalo, Andrew W. Mann, Nidia Morrell, Karen A. Collins, R. Paul Butler, Stephen A. Shectman, Johanna Teske, Jeffrey D. Crane, Shreyas Vissapragada, Madeleine Mckenzie, Khalid Barkaoui, Norio Narita, Akihiko Fukui, Jerome P. De Leon, Toshi Suganuma, Madyson G. Barber, Francis P. Wilkin, Victoria Zaledonis, Sophia Garcia-Gallet, Glauk Hizmo, Steve B. Howell, David R. Ciardi, Colin Littlefield, Sarah Deveny, Douglas A. Caldwell

High Energy Physics (Phenomenology)

How collective modes terminate in the dispersion relation of neutrino plasmas

Damiano F. G. Fiorillo

Neutrino plasmas support flavor waves, collective oscillations of flavor, that neutrinos can resonantly emit or absorb when they fulfill the Cherenkov condition. For massless neutrinos, this condition leads to singular features in the dispersion relation: Landau-damped modes, for example, disappear abruptly as their phase velocity approaches the speed of light. We investigate how these singularities change when nonzero neutrino masses introduce a spread in velocities. We classify singular behavior of the frequency as a function of wavevector into i) degeneracy points, where two modes merge, and ii) abrupt mode termination, when the frequency approaches a branch cut of the flavor dielectric function. For each class, we derive a local expansion and determine where such behavior can occur. Degeneracy points, frequently encountered in axially symmetric dispersion relations in the fast limit, are not generic. Nonzero neutrino masses lift the degeneracy along the symmetry axis; in three-dimensional wavevector space, there might still be degeneracy lines, not necessarily intersecting the symmetry axis. Abrupt mode termination, instead, persists generically, except for special energy distributions which are entire functions. As a byproduct of this study, we show that a collisionless plasma with a Lorentzian neutrino-frequency distribution is exactly equivalent to a monochromatic one with an effective collision rate. Approximating a general frequency distribution by a sum of Lorentzians therefore substantially simplifies the dispersion relation.
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High Energy Physics (Theory)

Holographic Krylov spread complexity for a confining multi-charge AdS soliton

Dimitrios Chatzis, Madison Hammond, Ricardo T. Santamaria et al. (+1 more)

We study holographic spread complexity for a Type IIB solution dual to a deformation of $\mathcal{N} = 4$ SYM that flows to a confining (2+1)-dimensional supersymmetric theory in the IR. We use the proposal that relates the rate of change of spread complexity of local operators with the proper momentum of an infalling probe particle in the bulk. We analyse two cases: a probe particle falling radially and a probe falling radially while rotating with conserved angular momentum. We elaborate on how to define the proper coordinate in the presence of a conserved Noether charge using the Routhian. The trajectories for the probes were studied numerically, revealing an oscillatory behaviour of the complexity.
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All authors Dimitrios Chatzis, Madison Hammond, Ricardo T. Santamaria, Jonathan Whittle

Instrumentation and Methods for Astrophysics

Gestalt: a meta-foundation model for astronomy

Michael J. Smith and Shashwat Sourav

The Platonic Representation Hypothesis predicts that sufficiently scaled foundation models converge on a shared representation of the world. As each non-converged model gives a noisy view of a common structure when passed the same input, we ask whether we can combine models into a representation that outperforms its individual components. We test this on galaxies: we embed images via a basket of 22 frozen foundation models from eight families, whiten each view, and take a randomised SVD of the embedding concatenation. The resulting 1024-dimensional embedding outperforms every basket member on 19/21 of our tested metrics for physical property and galaxy morphology estimation for HSC, JWST, and DESI Legacy Survey imagery. We find that performance rises with basket size and basket architectural diversity, and that the meta-foundation model's performance transfers across astronomical surveys. We conclude that a useful astronomical foundation model can be assembled from existing generalist models with no training required beyond a single unsupervised projection. By leveraging the community's already-spent work, we save a lot of compute: a fresh pre-train of a comparable single-domain model would cost $\mathcal{O}(10^{4}$–$10^{5})$ A100 GPU hours (emitting several tonnes of CO$_2$eq.), whereas assembling Gestalt requires minutes on a single machine.
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High Energy Physics (Theory)

A New Approach to Black Hole Thermodynamics in General EMD-like Theories

Peng-Yu Wu and H. Lu

We consider general EMD-like theories involving arbitrary numbers of both Maxwell fields and dilatonic scalars. We study charged black holes and derive several algebraic and differential relations among the thermodynamic quantities, scalar charges and the non-extremal parameter. These allow us to obtain two sets of master equations of thermodynamic quantities, depending on the choice of basic variables parameterizing the system. Solutions to either set of the master equations give rise to all the thermodynamic quantities, without constructing black hole solutions. We obtain all the thermodynamic quantities perturbatively in the power series expansions of charges, which we then verify using perturbative black hole solutions up to and including the quartic order in charges.
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Cosmology and Nongalactic Astrophysics

Testing Offsets Between Cluster-Scale Halos and BCGs in Strong Lensing Models Using the Jackknife Method

Sangjun Cha, Marceau Limousin and M. James Jee

Offsets between cluster-scale dark matter halos and brightest cluster galaxies (BCGs) inferred from strong lensing (SL) models have been used to investigate cluster dynamics and dark matter physics. However, it is necessary to test whether these offsets are required by SL data themselves. We investigate whether allowing these offsets improves predictive accuracy and examine the effects on magnification, time-delay predictions, and critical curve positions. We evaluate lens models of Abell 370, RX J1347.5-1145, and MACS J0416.1-2403 using the jackknife method, which assesses predictions for source systems excluded from the lens reconstruction. Models are constructed with MrMARTIAN, which combines analytic mass profiles with a regularized grid that represents mass structure not captured by the profiles. We compare fixed and free halo position models across regularization weights. The root mean square values averaged over excluded systems agree within bootstrap uncertainties, while the median paired differences remain close to zero across all three clusters and tested regularization weights. These results indicate comparable predictive accuracy between the fixed and free models. The total mass distributions remain broadly similar, although the magnitudes of fitted halo offsets vary with regularization, showing that the mass decomposition is not unique. For these three clusters, offsets between BCGs and cluster-scale halos in the lens models are not required by the SL data to improve predictive accuracy within the MrMARTIAN framework. The mass decomposition between the regularized grid and cluster-scale halos is not uniquely determined. These findings limit physical interpretations based on fitted halo positions alone. The model dependence of magnification and time-delay estimation can also affect the inferred intrinsic properties of high-redshift sources or the Hubble constant.
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High Energy Physics (Phenomenology)

Searching for BSM Experimental Signatures with Large Lagrangian Models

Ibrahim Elsharkawy, Victoria Knapp-Perez, Wahid Bhimji et al. (+1 more)

The search for physics Beyond the Standard Model (BSM) is generally limited not by the supply of theory descriptions but by the lack of discriminating experimental observations. A case in point is dark matter, where the overwhelming gravitational evidence only goes so far in distinguishing between models within a vast theory space. Exploring the space of testable model signatures may help identify overlooked experimental observables and indicate the utility of future experiments. A challenge is designing a search through model signatures outside what is found in the literature. Our primary contribution is hAIthem, a framework that combines the self-guided exploration of reinforcement learning (RL) with the broad literature-derived knowledge of LLMs. We build an RL agent that learns to find which portions of a theory's high-dimensional parameter space are not excluded under some subset of constraints by playing a Battleship-style "game" against a suite of phenomenology tools. The agent is built as a Large Lagrangian Model (LLaM), an autoregressive transformer that reads a tokenized Lagrangian, is pretrained at scale (here on ~1 billion tokens from ~10,000 Lagrangians), and is fine-tuned in a live environment. The framework then constructs a decision tree that separates RL-found regions using observables computed with established tools, and passes the remaining degenerate regions to a set of LLM agents that compete to produce realistic signatures. In this proof of concept, RL-search outperforms an evolutionary-algorithm baseline, finding more viable regions with greater physical diversity. In a restricted space of single dark scalar multiplet models, we find that hAIthem proposes interesting combinations of previously studied observables, such as the application of a halo-independent kinematic ratio to paleo-detectors.
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All authors Ibrahim Elsharkawy, Victoria Knapp-Perez, Wahid Bhimji, Aishik Ghosh

High Energy Physics (Theory)

Bootstrapping Weakly Broken Gauge Theories in (A)dS

Daniel Baumann, Kurt Hinterbichler, Callum R. T. Jones et al. (+1 more)

We develop a bootstrap approach for weakly broken gauge theories in (anti-)de Sitter space, focusing on cases in which the conservation of the dual boundary current is broken by a double-trace operator. Integrating the corresponding Ward identity, we derive pseudo-charge conservation identities that contain fixed nonlocal contributions as integrals of three-point functions. These identities impose consistency conditions on the space of allowed theories. As an illustrative example, we study Yang-Mills theory in AdS with symmetry-breaking boundary conditions for charged matter and show that the pseudo-charge conservation identities constrain the mixing between the two quantization sectors. We then apply the framework to the Higgs mechanism for gravity in two AdS spaces with a common boundary, coupled so that the corresponding stress tensors are not separately conserved. In this setting, the ordinary charge conservation identities recover the factorization into two independent CFTs, whereas the pseudo-charge conservation identities hold for arbitrary values of the symmetry-breaking parameter. Finally, for conformal gravity in de Sitter space, we constrain the interactions between the graviton and the partially massless spin-2 field, both in the minimal theory and in the presence of additional scalar or vector matter, finding agreement with the predictions of the corresponding bulk theories.
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All authors Daniel Baumann, Kurt Hinterbichler, Callum R. T. Jones, Nathan Meurrens

High Energy Physics (Theory)

Quantum Gravity Principles for 4d $\mathcal{N}=2$ Supergravity Theories and Asymptotic Hodge Theory

Lukas Kaufmann and Timo Weigand

We study the behaviour of general four-dimensional N=2 supergravity theories near boundaries at infinity of the vector multiplet moduli space, with a focus on a clear distinction between properties that follow from supergravity alone rather than from a consistent UV completion in quantum gravity. The basis for our analysis is the appearance of a real variation of polarised Hodge structure governing the vector multiplet moduli space of N=2 supergravity, combined with very recent advances in the mathematics literature. The resulting classification of infinite distance degenerations exactly agrees, at the level of gauge couplings, with a possible interpretation of the limits as decompactification limits to five or six dimensions or as weakly coupled string limits, as expected from a quantum gravity perspective. This observation extends previous results found in the context of string compactifications on Calabi–Yau varieties and, remarkably, holds for general four-dimensional N=2 supergravity theories regardless of a UV completion. We furthermore show the existence of a Kähler basis in which the triple couplings of the prepotential are non-negative, irrespective of a geometric origin of the supergravity theory. Finally we propose two non-trivial constraints for a four-dimensional N=2 supergravity to be compatible with quantum gravity: Integrality of the Hodge structure as a necessary condition for the completeness hypothesis and the existence of a simple normal crossing compactification of the moduli space to ensure compatibility of the weakly coupled asymptotic gravitational duality frames.
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Quantum Physics

Making the most of leftovers: Improved privacy amplification for quantum key distribution

Matthew Simon Tan, Bartosz Regula and Marco Tomamichel

The amount of secret key that can be obtained from a quantum key distribution run depends on both the physically observed error rates and the mathematical bounds used to certify security. For finite datasets, conservative bounds force users to discard a substantial fraction of the potentially available key. Here we further refine and extend the privacy amplification bounds achievable through the recent leftover hash lemma of Regula and Tomamichel [arXiv:2603.04493] and incorporate them into the security analysis of quantum key distribution based on entropic uncertainty relations. This improves on state-of-the-art key rates in finite-block regimes, certifying more secret key from the same experimental data without changes to the protocol, and outperforming techniques based on entropy accumulation. The results illustrate how sharper mathematical estimates can directly increase the usable output of a quantum communication system.
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Cosmology and Nongalactic Astrophysics

Close Pulsar Pairs See Dark Matter Substructure through the Gravitational-Wave Background

Abhiram Cherukupalli, Vincent S. H. Lee, Kim V. Berghaus et al. (+1 more)

Pulsar timing arrays detect signals from dark matter substructure, but a nanohertz gravitational-wave background (GWB) severely degrades their sensitivity. We show that timing pulsar pairs separated by sub-parsec distances avoids this degradation. The GWB imprints nearly the same perturbation on both pulsars and is suppressed in the difference of their residuals, whereas a nearby dark matter subhalo perturbs the two differently and survives. We find that an array with pulsar pairs separated by $0.1\,\mathrm{pc}$ improves the sensitivity to subhalos of order $\sim10^{-6}$ solar masses by more than an order of magnitude, relative to an otherwise identical array of widely separated pulsars. Dense globular clusters naturally host many such pairs, though the baryonic environment must be separated from a dark matter substructure signal.
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All authors Abhiram Cherukupalli, Vincent S. H. Lee, Kim V. Berghaus, Kathryn M. Zurek

High Energy Astrophysical Phenomena

Nearby Supernova Science in the Era of High Cadence, Deep Time Domain Surveys

David J. Sand, Bhagya Subrayan, Conor L. Ransome et al. (+41 more)

We discuss science opportunities for nearby supernovae (SNe) in the era of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), emphasizing the youngest phases of SN evolution and the value of contemporaneous high-cadence shadowing surveys. LSST's Wide Fast Deep survey will discover enormous numbers of SNe, but its $\sim 3$ day cadence will miss signatures that evolve on timescales of hours to days, requiring cadence augmentation by other programs. We present simple depth and cadence metrics for early SN signatures and use empirical nearby SN discovery rates to estimate the resulting science opportunities. LSST will detect or set limits on precursor emission from hundreds of core-collapse SNe, including $\gtrsim 50$-100 Type IIn and normal Type II SNe annually, as well as $\gtrsim$5 Type Ibn. Within $\sim 200$ Mpc, roughly 250 Type Ia SNe are classified annually, providing the potential to identify hundreds of early light-curve excesses, and a robust measurement of the incidence of extreme high-velocity features ($>$25,000 km s$^{-1}$). A shadowing survey with a depth of $\sim 22.5$ mag could search for early light-curve features, akin to the light-curve excess seen in SN2023ixf, across dozens of nearby core-collapse SNe every year. Rapid spectroscopy of $\gtrsim$150 Type II SNe per year within $\sim$160 Mpc could constrain the incidence of short-lived flash features to $\lesssim$10% within a few years, while also tying this to the rate of precursor emission in normal Type II SNe. We also discuss the challenges posed by early classification ambiguity and faint nonterminal transients, and we request that the 80 hour embargo on LSST images be waived for nearby galaxy fields. Finally, we advocate for a Nearby Galaxy Transient Broker that integrates transient streams, archival data, forced photometry, and follow-up triggering in a single platform.
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All authors David J. Sand, Bhagya Subrayan, Conor L. Ransome, Griffin Hosseinzadeh, K. Azalee Bostroem, Jennifer E. Andrews, Jeniveve Pearson, Yize Dong, Stefano Valenti, Saurabh W. Jha, Brian Hsu, Aravind P. Ravi, Manisha Shrestha, Charles D. Kilpatrick, Noah Franz, Mojgan Aghakhanloo, Igor Andreoni, Moira Andrews, Katie Auchettl, Federica B. Bianco, Régis Cartier, Siddharth Chaini, Diva Chaudhary, Analía V. Smith Castelli, Shar Daniels, Alexei V. Filippenko, Melissa L. Graham, Xander J. Hall, Daichi Hiramatsu, D. Andrew Howell, Lindsey A. Kwok, Amanda R. Lopes, Thomas Matheson, Curtis McCully, Maryam Modjaz, Phillip Noel, Gregory S. H. Paek, Antonella Palmese, Anthony L. Piro, Monika Soraisam, Sergiy Vasylyev, József Vinkó, J. Craig Wheeler, Samuel D. Wyatt

General Relativity and Quantum Cosmology

A Strong Cosmologically Coupled Mass Growth Solution in Linearized General Relativity

Kevin S. Croker, Joshua Cohon, Viktor T. Toth et al. (+13 more)

DESI Data Release 2 has heightened interest in cosmologically coupled black holes (CCBHs) as an explanation for accelerating late-time expansion, but known models for CCBHs grow too slowly to drive it. We construct at linear order a solution to General Relativity whose Hernandez-Misner-Sharp mass passively grows $\propto a^\kappa$ as the universe expands. The constant $\kappa$ enters all eigenvalues of the Weyl and stress-tensor operators, so growth is unambiguously physical in both free-field and material sectors. The solution is causal over spacetime relevant for stellar collapse compact objects. A cloud of energized vacuum emerges at $\kappa = 3$, complementing the $a^3$ scaling predicted elsewhere for the masses of energized vacuum black holes. This first step toward $\kappa \sim 3$ CCBH exact solutions enables observational tests with pulsar binaries.
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All authors Kevin S. Croker, Joshua Cohon, Viktor T. Toth, Massimiliano Rinaldi, Nicolas Fernandez, Joel L. Weiner, Duncan Farrah, Gregory Tarlé, Gustavo Niz, Christopher Cain, James W. Rohlf, Alejandro Aviles, Jake Summers, Leander Thiele, Rogier A. Windhorst, Joshua Grumski-Flores

High Energy Physics (Theory)

Scale-Covariant Holography

Nikolay Bobev, Pieter Bomans and Fridrik Freyr Gautason

We explore a vast landscape of scale-covariant string backgrounds that arise from the backreaction of D$p$-branes. In a convenient Weyl frame the metric has an AdS factor and the dilaton has a non-trivial profile. This structure provides a notion of scale covariance that facilitates a holographic analysis and provides a window into the dynamics of the dual strongly coupled non-conformal gauge theory. We present different classes of supergravity solutions of this kind and discuss their dual field theory interpretation. We find several new supersymmetric backgrounds arising from D2-branes by utilizing four-dimensional gauged supergravity, D$p$-branes wrapped on compact manifolds, and infinite families constructed directly in ten dimensions. We construct holographic RG flows between some of the new supersymmetric backgrounds and compute the spectrum of low-lying local operators. Holography determines the form of observables such as the thermal free energy and scalar two-point functions, predictions which could be tested on the lattice.
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High Energy Physics (Theory)

Detectors in Nonrelativistic Conformal Field Theories

Cyuan-Han Chang, Subham Dutta Chowdhury, Ian Moult et al. (+1 more)

Correlations in asymptotic fluxes provide one of the primary experimental means of studying physical systems. In the context of relativistic QFT, the formalization of such experiments in terms of detector operators has led to significant progress. Motivated by these successes, in this paper we initiate a study of detector operators in nonrelativistic conformal field theories (NRCFTs). In NRCFTs, fluxes are distributed in both angle and velocity, making the natural detector operator the energy flux differential in velocity, $\mathcal{E}_v(\hat{n})$. We provide non-perturbative definitions of these operators in NRCFTs, and study their symmetries and algebra. We calculate one-point functions of these detector observables in a variety of few and many body states of representative NRCFTs, including free fermions, as well as fermions at unitarity. In interacting three-body states, they exhibit a remarkably rich behavior reflective of the Efimov three-body wave-function, including the formation of an enhanced "jet" structure due to the presence of resonant interactions. We use these detectors to derive a nonrelativistic generalization of the Hofman-Maldacena conformal collider bounds by arguing for positivity of $\mathcal{E}_v(\hat{n})$, and imposing this in spin 1 states. We outline a number of future directions for the study of detectors in NRCFTs, and discuss how they can be measured in a variety of experimental platforms from cold atoms to low energy neutron experiments.
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All authors Cyuan-Han Chang, Subham Dutta Chowdhury, Ian Moult, Dam Thanh Son

Quantum Physics

Exact Operator Complexity Measures from Random Matchgate Unitaries

Gregory A. L. White, Jens Eisert and Neil Dowling

Matchgate circuits describe classically tractable dynamics in a physically relevant setting while nonetheless exhibiting features characteristic of complex quantum systems, such as high amounts of magic. This invites the broader question: to what extent are typical complexity measures saturated under trivial dynamics? Here, we address this by studying the behaviour of different Heisenberg-picture complexity measures in random matchgate ensembles. Our main technical contribution is a tractable and generalisible free-fermionic unitary Weingarten calculus formulated entirely in the Majorana basis. This method is tailored to computing moments of operators, and simplifies to a combinatorics problem which depends on the boundary conditions prescribed by a given operator functional. Using this framework, we derive closed-form expressions for the typical local-operator entanglement, operator stabiliser entropy, and higher-order out-of-time-ordered correlators. For extensive initial Majorana strings, both operator entanglement and stabiliser entropy obey volume laws, even though the underlying circuits remain classically simulable. Out-of-time-ordered correlators can likewise become exponentially small, showing that their late-time saturation value alone does not witness computational hardness and constituting a classically tractable example of emergent free independence. Finally, we relate these separations to operator resource theories, showing how operator entanglement beyond the Gaussian baseline lower-bounds the number of non-Gaussian gates in doped matchgate circuits. Our results present a practical toolbox for computing exact averages over random matchgates, while clarifying the distinction between quantum resources versus simulation complexity, and their dependence on the representation being exploited.
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High Energy Astrophysical Phenomena

Not So Heavy Metal I: Low Metallicity Enhances the Rate of high-redshift Superluminous Supernovae

Ben Margalit, Allison L. Strom, Cristina Andrade et al. (+4 more)

Type-I superluminous supernovae (SLSNe) are extremely luminous stellar explosions originating from the core collapse of massive stars. Unlike normal core-collapse supernovae, however, SLSNe occur almost exclusively in metal-poor environments. As a result, their volumetric rate should not simply trace the cosmic star-formation history, but instead evolve with the metallicity distribution of galaxies across cosmic time. In this work, we introduce a new theoretical framework for modeling the volumetric rate of astrophysical sources as a function of redshift and metallicity. Our formalism combines metallicity scaling relations, stellar-mass distribution functions, and metallicity-dependent production efficiencies. Importantly, it also distinguishes between metallicity measures based on O/H and Fe/H abundances. Applying our new formalism to SLSNe, we predict volumetric rates that are nearly an order of magnitude higher at $z \gtrsim 2$ compared to models in which the rate traces the cosmic star-formation rate alone. This has direct implications on the detection prospects of high-$z$ SLSNe with the Vera C. Rubin Observatory and other time-domain surveys.
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All authors Ben Margalit, Allison L. Strom, Cristina Andrade, Michael W. Coughlin, Adam A. Miller, Steve Schulze, Ved G. Shah

Computer Vision

It Takes Little to Rewrite Perception: Targeted Semantic Substitution in Vision-Language Models at $\epsilon \leq 4/255$

Binchi Zhang, Apurva Narayan and Atrisha Sarkar

Vision Language Models (VLMs) are widely deployed in safety-critical scenarios, and understanding to which extent they can be controlled by adversarial perturbation is a prerequisite for evaluating their trustworthiness. Existing representation-alignment attacks, which make a VLM perceive a target image, achieve limited success at $\varepsilon \leq 4/255$. Therefore, VLMs seems robust to perturbations in this range. We show that this robustness does not hold, as targeted semantic substitution succeeds within the same range. Specifically, we align each stream of the source image with its counterpart in the target image in the victim VLM's post-merger token space, operating under a white-box threat model. We evaluate under a strict success criterion, requiring the model to simultaneously name the target, confirm its presence, and deny the source. In images, target semantics appear at $\varepsilon = 2/255$ and complete replacement reaches 38% at $\varepsilon = 4/255$. On video, complete replacement reaches 35.9% at $\varepsilon = 1/255$. We also observe a phenomenon of semantic fusion, where Large Language Model (LLM) rationalizes contradictory visual signals into a coherent narrative.
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