Astrophysics of Galaxies
Snapshots of r-process production in the Milky Way disk
Sarah G. Kane, Stephanie Monty, Madeleine McKenzie et al. (+9 more)
Stars enhanced in heavy
neutron capture elements like europium (Eu) provide a window into the rarest and most exotic nucleosynthetic events. Most Eu-enhanced
stars discovered thus far are found among metal-poor populations, with $\mathrm{[Fe/H]}<-1.0$. Here, we report the discovery of $17$ vetted Eu-enhanced
stars ($\mathrm{[Eu/Fe]}>0.7$) in the Milky Way disk with
metallicities in the range $-0.87<\mathrm{[Fe/H]}<-0.21$ identified from among $74\,717$
stars in the GALAH survey. 14 of these
stars additionally have $\mathrm{[Ba/Eu]}<0$, marking enhancement from the rapid
neutron capture ($r$-) process and making these r-II
stars. Included in their number is a
star with a remarkably high $\mathrm{[Eu/H]}=1.01\pm0.09$ at $\mathrm{[Fe/H]}=-0.21$. In addition to Eu, all 17
stars show enhancements in other
neutron capture elements, especially in Nd, while otherwise appearing chemically consistent with typical disk
stars, particularly in their $\alpha$-element abundances. Two of the Eu-enhanced
stars exhibit indications of binarity with strong enrichment in Ba and Y, marking potential signatures of the slow or intermediate
neutron capture processes. This sample of 17 Eu-enhanced
stars, which span both the high- and low-$\alpha$ disks, are valuable tracers of
neutron capture processes, including the $r$-process, at high
metallicities. Although we use criteria for Eu-enhanced
stars typically applied to the
halo to enable comparison to literature studies of $r$-process enhanced
stars, we propose a new,
metallicity-dependent selection for Eu enhancement that is better-suited to the regime of the
Galactic disk.
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All authors Sarah G. Kane, Stephanie Monty, Madeleine McKenzie, HanYuan Zhang, Sven Buder, Terese Hansen, Tadafumi Matsuno, Jason Sanders, Anke Ardern-Arentsen, Vasily Belokurov, Zofia Kaczmarek, Andrew Garner
Robotics
In-Context Learning for Robots: Methods and Applications
Haojian Huang, Zexi Li, Junhao Guo et al. (+36 more)
General-purpose
robots must infer what a new task requires and translate that understanding into appropriate physical action. In-context learning (ICL) for
robots supports this process by using demonstrations and interaction to direct existing competence with neural parameters held fixed during deployment. We organize this literature review around the interfaces connecting contextual evidence to execution, distinguishing four families: context-conditioned policies,
geometric demonstration transfer, world-model-based control, and skill- and
agent-based execution. Comparing these interfaces clarifies their transfer assumptions and the roles of training, correspondence, and
memory in making context useful. Across manipulation and
navigation, we examine how these mechanisms preserve taught requirements as objects, environments, and execution conditions change. This analysis links method design to evaluation practices that distinguish responsiveness to teaching, physical transfer, and benefits from retained experience. The resulting agenda connects compositional task acquisition and faithful transfer with physical recursive self-improvement, in which experience improves the ability to learn subsequent tasks.
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All authors Haojian Huang, Zexi Li, Junhao Guo, Yehang Zhang, Wenxuan Peng, Bohan Zhou, Weilin Ruan, Leyi Wu, Chenxu Wang, Jianchong Su, Binghui Xie, Wosong Chen, Yingjie Xu, Tianhao Zhou, Suzeyu Chen, Pukun Zhao, Jiaqi He, Xinyi Li, Runze Li, Peiran Dong, Shaoxiang Dang, Jing Huang, Yingbing Chen, Yifan Chang, Tianyi Zhang, Shiyuan Deng, Haozhi Wang, Yangkai Wei, Wenqian Li, Han Yang, Kaiwen Zhou, Huaping Liu, James Cheng, Rui Shao, Donglin Wang, Yaochu Jin, Jianye Hao, Ying-Cong Chen, Yinchuan Li
Social and Information Networks
Group dynamics of engagement with AI topics on Bluesky
Bradley Huynh, Moyi Tian and Nancy Rodríguez
Social media increasingly shapes everyday life, serving as both a central venue for discussion of major events and a space where online collective behavior can spill over into real-world activity, while artificial intelligence (AI) is likewise becoming increasingly influential across society. Understanding how different online communities respond to AI-related events, and disentangling the mechanisms underlying the development of such engagement, are therefore increasingly important for studying information spreading and the societal reception of AI. Our work addresses the limited connection between empirical studies of AI-related online engagement and mathematical modeling of group-level spreading dynamics. We develop a framework to collect and organize empirical Bluesky activity into distinct user groups, then use a network-based dynamics model to investigate the mechanisms underlying their engagement. We use the release of DeepSeek R1 as a case study under two complementary grouping schemes: AI-related communities and academic disciplines. For each group, we fit a network-based Susceptible-Infected-Recovered (SIR)-type model augmented with an exogenous engagement term, allowing us to quantify the relative strengths of endogenous network-driven spreading and direct external response. Across groups, we find that strong direct responses to the event do not necessarily coincide with strong network-driven propagation, revealing distinct engagement patterns that may be obscured by aggregate activity alone.
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Lattice Field Theory
A parameter independent analysis of the QCD chiral phase transition and its universal critical behaviour
Jishnu Goswami, Frithjof Karsch, Sabarnya Mitra et al. (+1 more)
We make use of unique properties of scaling functions to estimate the
chiral phase transition temperature and corresponding universal critical parameters of this phase transition directly from (2+1)-
flavor QCD simulations with highly improved staggered
fermions on
lattices with temporal extent $N_\tau=8$. Working with an improved
chiral order parameter for quantifying
chiral symmetry breaking, we analyze the finite-volume dependence of this observable for a wide range of
lattice volumes and light
quark masses, and quantitatively estimate the deviations from the expected universal scaling behaviour as a function of the light-to-strange
quark mass ratio.
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All authors Jishnu Goswami, Frithjof Karsch, Sabarnya Mitra, Christian Schmidt
Mathematical Physics
Coherent energy cascades in nonlinear disordered Hamiltonians
Anxo Biasi, Brad Cownden, Oleg Evnin et al. (+1 more)
The familiar wave kinetic theory revolves around turbulent energy cascades characterized by random phases of the individual normal modes. By contrast, recent years have revealed turbulent cascades where the transfer of energy is mediated by phase-coherent dynamics. Such coherent cascades have been previously established in deterministic systems with a tightly controlled algebraic structure of the mode interactions, such as nonlinear Schrödinger equations. Here, we show that the presence of phase-coherent cascades is robust with respect to substantial alterations of the mode couplings. We prove that, in infinite-dimensional resonant
Hamiltonian systems with fully resonant normal mode spectra and random nonlinear couplings, a structured subset of couplings — an infinitesimal fraction of the total — suffices to support coherent cascades characterized by phase
alignment, the formation of power-law spectra, and either unbounded growth of Sobolev norms or a finite-time blow-up. Numerical simulations further demonstrate the emergence of coherent cascades from random initial data through a process of phase locking, suggesting a mechanism for their emergence in broader classes of initial data and systems. We thus show that disordered mode interactions can sustain, rather than block, coherent energy transport across arbitrarily distant scales.
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All authors Anxo Biasi, Brad Cownden, Oleg Evnin, Alvaro Iturbe Jabaloyes
Quantum Physics
Entanglement spectrum and magic in higher-dimensional free fermionic systems
Beatrice Magni, Daniele Iannotti and Riccardo Travaglino
We study fermionic non-local magic in higher-dimensional free-
fermion systems through the lens of the
entanglement spectrum. For translationally invariant Gaussian states in strip geometries, dimensional reduction maps the problem to independent lower-dimensional momentum sectors, leading in two dimensions to a multiplicative logarithmic violation of the boundary law analogous to Gioev-Klich-Widom scaling. We further show that the second Rényi fermionic non-local magic is bounded by the capacity of
entanglement and introduce an
entanglement-temperature deformation that probes the low-energy structure of the
entanglement Hamiltonian. Applied to the matter-Majorana sector of the Kitaev model, this response is exponentially suppressed in the Abelian phase and algebraic in the non-Abelian phase, where its ratio with the capacity approaches a universal constant. Out of
equilibrium, we extend the quasi-particle description to fermionic non-local magic in higher-dimensional quenches and show that random Gaussian
circuits exhibit diffusive spreading in two spatial dimensions.
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High Energy Physics (Phenomenology)
Infrared Subtraction with Artificial Intelligence
Wenjie He, Xiaohui Liu, Yandong Liu et al. (+1 more)
We present AI-developed local infrared subtraction, building on projection to Born and EFT matching. The framework separates an integrable radiation term from a finite contribution at Born kinematics, referred to as the Born contact. The contact is determined using the EFT singular distribution in a resolution observable such as N-jettiness $\tau_N$. Under human physics guidance, an LLM develops two implementations. One uses a neural network for phase space projection and fits the contact by matching to EFT cumulants. The other uses an analytic construction that keeps the Born momenta fixed while integrating over radiation. It combines the EFT $\delta(\tau_N)$ coefficient with finite 4-dimensional radiation integrals to calculate the contact term directly. This gives a local subtraction formula without a slicing parameter, while reusing existing lower-order radiation calculations and EFT singular predictions. As a demonstration, we reconstruct the full NLO correction for massless 3- and 4-jet production in electron-positron annihilation. The attempt to the NNLO dijet production is also made by recursively using the NLO P2B construction with the LLM designing machine-learning controls to reduce the variance of the contact integral. The tested predictions are in good agreement with EERAD3. The numerical calculation and projection-network training use a 2020 Apple M1 MacBook, without GPU acceleration, illustrating the feasibility of the construction with modest computing resources. The appendices develop an extension of the local subtraction to 3-jet NNLO, giving explicit radiation maps and a proposed contact formula. We also show how to integrate over NNLO radiation while keeping the Born momenta fixed, for any number of massless final-state jets. Our results demonstrate how AI can help higher-order calculations by constructing infrared subtraction and improving its numerical integration.
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All authors Wenjie He, Xiaohui Liu, Yandong Liu, Zhan Wang
Quantum Physics
Fast Hamiltonian engineering from cut polytope geometry
Thomas Joachim Friese, Özgün Kum, Aram W. Harrow et al. (+1 more)
Hamiltonian engineering (HE) simulates
quantum dynamics under a target
Hamiltonian using a native entangling system
Hamiltonian and restricted control, with applications from
quantum gate design to analog
quantum simulation. Observing that, for many systems, formulating HE as a linear program only requires specific commutation relations between the control pulses and the system
Hamiltonian, we provide a unified framework for broad classes of $2$-local
qubit, qudit, and fermionic systems. We reformulate time-optimal HE as a complex $k$-cut polytope problem, with $k$ the number of distinct phases in these commutation relations, and prove it NP-complete for every finite $k$. We therefore relax the polytope to the elliptope and apply a Krivine-type rounding, yielding pulses informed by the system and target
Hamiltonians, which we then use in a linear program. We derive how many informed pulses are necessary and sufficient for the linear program to be reliably feasible. Additionally mixing in uniformly sampled pulses guarantees a solution close to the relaxation value from $\mathrm{O}(m)$ pulses, with $m$ the number of interaction terms. Together with upper and lower bounds on the optimal
quantum run time, this yields an $\mathrm{O}(\sqrt{m})$ approximation ratio. In
benchmarks on a fully connected Ising model, a
chiral clock model for qudits, and the fermionic Harper-Hofstadter model, our approach attains near-optimal
quantum run times wherever the optimum is computable, reaches run times that saturate with the
lattice size in the fermionic case, and outperforms state-of-the-art methods with $\mathrm{O}(m)$ pulses. This establishes a unified approach with provable guarantees to the automatic programming of analog
quantum simulators.
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All authors Thomas Joachim Friese, Özgün Kum, Aram W. Harrow, Martin Kliesch
General Relativity and Quantum Cosmology
Stochastic gravitational-wave background from subsolar neutron stars in collapsar disks
Valerio De Luca, Loris Del Grosso and Emanuele Berti
The fragmentation of the
neutrino-cooled
accretion disks that surround the black holes formed in collapsars has recently been proposed as an astrophysical channel for the production of
neutron stars with masses well below the standard core-collapse floor. These disk-born objects merge either with one another or with the central black hole, and the superposition of all such mergers across
cosmic history sources a
stochastic gravitational-wave background. In this work we compute the energy density of this background for both merger channels, adopting a formation history tied to the observed rate of long gamma-ray bursts. We find that the merger of a subsolar
neutron star with the central black hole is the loudest channel, already constrained by current data and within reach of next-generation observatories, while the binary
neutron-
star channel is at most two orders of magnitude fainter, with its widest binaries remaining accessible to next-generation detectors. Confronting these predictions with the fourth observing run of the LIGO–Virgo–KAGRA Collaboration, we derive two upper bounds on the fraction of collapsars whose disks produce such mergers: a robust one from the non-detection of an isotropic background, and a tighter one that could be achieved by a dedicated search for resolvable subsolar events in current data. Gravitational waves from non-axisymmetric deformations of the collapsar disk itself would provide an additional independent signature for the collapsar scenario, enabling cross-correlation studies with future deci-Hz detectors. Overall, the background computed here provides a population-level probe of disk-born subsolar
neutron stars, which next-generation detectors could bring firmly into view.
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Quantum Physics
Digital Quantum Algorithms for Generating and Utilizing Spin Squeezed States
Mingru Yang, Ruby Wei and Chao Yin
Spin squeezed states (SSSs) are conventionally viewed as analog resources for
quantum metrology. Here we develop
algorithms to efficiently generate and exploit SSSs on a digital
quantum computer. We introduce an adaptive local-
circuit protocol that prepares SSSs with squeezing parameter $\xi$ in depth $\mathrm{O}\left(\log{1/\xi}\right)$, yielding an exponential improvement over non-adaptive approaches. We prove that this depth is optimal for permutation symmetric SSSs by deriving a matching lower bound on
entanglement entropy. We further leverage the squeezing paradigm to deterministically prepare the Dicke states using asymptotically fewer resources than prior methods. Remarkably, classical simulations of our preparation protocols under realistic noise models predicts a metrological gain of 4.2 dB beyond the standard
quantum limit with 55 superconducting
qubits in total including ancillae. Our work paves the way for performing
quantum metrology on near-term digital
quantum devices.
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Astrophysics of Galaxies
MOCSS: Multi-Object Coronagraphy for JWST/NIRSpec Slitless Spectroscopy
Mason S. Huberty, Claudia Scarlata, Matthew J. Hayes et al. (+10 more)
We present an experimental JWST/NIRSpec observational method to obtain $R\gtrsim1000$ G140M/F100LP slitless spectroscopic observations. This "Multi-Object Coronagraphy for Slitless Spectroscopy" (MOCSS) technique involves opening essentially all microshutters on NIRSpec simultaneously while closing shutters corresponding on-sky with known bright objects. Through observations of the Hubble Ultra Deep Field, we demonstrate the discovery potential of these deep, high resolution observations without the need for target pre-selection. We obtain a catalog of 22 secure multi-line emitters at $1.3<z<4.6$, with observations of [OII], [OIII], H$\alpha$, H$\beta$ and [NII] lines, accounting for $\sim80\%$ of the emission lines identified directly in the dispersed images. The MOCSS survey provides first time spectroscopic
redshifts for 18 of these sources. We also demonstrate that first order traces of the NIRSpec/G140M/F100LP observing mode extend substantially beyond the nominal $\sim1.89\rm \mu m$ red cutoff, as far as $2.94\rm \mu m$ in the most extreme case. Compared to existing NIRISS WFSS of similar exposure times, we find that the MOCSS technique can observe very faint lines while covering the full $1-2 \rm \mu m$ regime without gaps in wavelength coverage. This study describes the highest-resolution slitless spectroscopy campaign of the $1-2 \rm \mu m$ regime and emphasizes the discovery potential of this unorthodox observational technique.
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All authors Mason S. Huberty, Claudia Scarlata, Matthew J. Hayes, Alaina Henry, Danielle A. Berg, Vieri Cammelli, Richard Ellis, Anne E. Jaskot, Matilde Mingozzi, Pierluigi Monaco, Alberto Saldana-Lopez, Jonathan C. Tan, Alice Young
Cosmology and Nongalactic Astrophysics
Connecting the Dots: Prospects for Detecting Multi-Source Inflation through Scale-Dependent and Stochastic Bias of Little Red Dots
Peter L. Taylor, Xinyi Chen, Christopher M. Hirata et al. (+1 more)
Recent work has proposed using the spatial clustering of Little Red Dots (LRDs) as a high-
redshift cosmological probe. In this paper, we investigate the feasibility of obtaining a LRD sample with a future space experiment, and forecast LRD constraints on
primordial local-type non-Gaussianity, $f^{\rm loc}_{\rm NL}$, and the collapsed-limit trispectrum amplitude, $\tau^{\rm loc}_{\rm NL}$. LRDs are ideally suited to probe these inflationary parameters because they span a large cosmological volume, have high bias and are easily identifiable. We perform idealised joint $f_{\rm NL}^{\rm loc}$–$\tau_{\rm NL}^{\rm loc}$ Fisher forecasts assuming the universality relation, Gaussian covariance, Poisson shot-noise and a normalised
redshift dispersion, $\sigma(z) / \left( {1+z} \right)= 0.03$. We quantify the significance at which one would detect multi-source inflation under the Suyama–Yamaguchi relation, $\tau^{\rm loc}_{\rm NL} > \left( 6/5 f_{\rm NL}\right)^2$, across the $f_{\rm NL}^{\rm loc}$–$\tau_{\rm NL}^{\rm loc}$ plane. We find that a LRD analysis could robustly detect multi-source inflation at high-significance over a large region of parameter space, and would be more constraining than all other past or present experiments.
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All authors Peter L. Taylor, Xinyi Chen, Christopher M. Hirata, Charuhas Shiveshwarkar
Machine Learning
Making Cross-Continental Federated Learning Repeatable with FLIP: a Multi-Application Study
Rafael Garcia-Dias, Alexandre Triay Bagur, Chayanin Tangwiriyasakul et al. (+20 more)
Federated learning (FL) in healthcare remains challenging, as the overhead of rebuilding governance guarantees for every collaboration stops most projects at the proof-of-concept stage. Here we present FLIP (
Federated Learning Interoperability Platform), an open-source, multi-application platform that makes FL training and evaluation repeatable. FLIP implements common FL workflows as a set of composable services: cohort queries against per-site structured databases, on-demand DICOM
retrieval from institutional PACS, per-site project approval, and reusable FL job types. To demonstrate FLIP, we ran two distinct use cases,
federated fine-tuning and
federated evaluation, on synthetic chest X-ray cohorts across two client nodes based in the United Kingdom (UK) and Thailand. In FLIP, each institution independently approves its participation in each project and operates its own node under local IT security processes. This study makes an operational rather than an algorithmic claim. It does not compare
federated with centralised training; for that question, we refer the reader to existing systematic reviews and meta-analyses. The central result is evidence that such platforms enable international FL collaboration and improve repeatability, auditability, and site-specific governance. We also present a comprehensive comparison of existing platforms to help researchers and operators choose the right platform for their use case.
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All authors Rafael Garcia-Dias, Alexandre Triay Bagur, Chayanin Tangwiriyasakul, Virginia Fernandez, Parhom Esmaeili, Piyalitt Ittichaiwong, Yang Li, Lawrence Adams, Wason Buncharoen, Martin Chapman, Benjamaporn Chayanond, Sadthavud Chunrod, Tanawat Fongsri, Kass Gibson, Supat Plungprasertkul, Supawit Tangpanithandee, Kanyakorn Veerakanjana, Vicky Goh, Michela Antonelli, Joe Zhang, Kongkiat Kespechara, Sebastien Ourselin, M. Jorge Cardoso
Cosmology and Nongalactic Astrophysics
Cosmological-perturbation equations from the total-angular-momentum formalism
Marc Kamionkowski and Robert R. Caldwell
We derive the equations for the linear
evolution of cosmological perturbations using total-angular-momentum (TAM) waves. The
cosmic microwave background temperature and polarization transfer functions are first derived as integral equations and from these the usual Boltzmann hierarchy of differential equations are then obtained for both scalar and tensor perturbations. We include the effects of isotropic
cosmic birefringence and discuss anisotropic
cosmic birefringence. We note a subtle effect of
cosmic birefringence on temperature fluctuations. The TAM derivation of the equations provides physical insights to results obtained previously.
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Solar and Stellar Astrophysics
Beyond what's observed: hierarchical inference of Gaia astrometric compact-object binaries
Natsuko Yamaguchi, Kareem El-Badry, Reed Essick et al. (+3 more)
Astrometry from the
Gaia mission has revealed a large and homogeneous population of binaries containing compact objects, including more than 3000 white
dwarf–main sequence (WDMS) binaries with orbital periods of $P_{\rm orb}\sim100$–$1000$ d. Most of these binaries likely underwent mass transfer from asymptotic
giant branch donors, but their evolutionary histories remain uncertain. We develop a hierarchical
Bayesian inference model to constrain the intrinsic properties of the
Gaia WDMS binary population while accounting for measurement uncertainties and the survey selection function. We infer the distributions of orbital period, component masses, and eccentricity, as well as the total space density. We find that the intrinsic orbital-period distribution follows a declining power law, $p(P_{\rm orb})\propto P_{\rm orb}^{-0.445\pm0.048}$, and the WD mass distribution is sharply peaked near $0.6\,M_\odot$, with only ~1% of systems hosting WDs more massive than $0.8\,M_\odot$. The inferred MS-
star mass distribution is relatively flat down to ~$0.3\,M_{\odot}$, which is unexpected if the population is dominated by products of stable mass transfer with a fixed critical mass ratio. The eccentricity distribution peaks at a nonzero value, $e=0.046\pm0.001$, suggesting incomplete circularization or eccentricity excitation. We infer a midplane space density of ~$3\times10^4\,{\rm kpc}^{-3}$ for WDMS binaries in the parameter space probed by
Gaia DR3. These properties provide empirical
benchmarks for future work to constrain binary
evolution models. We also apply the framework to
Gaia black hole and
neutron star binaries, inferring that $30^{+66}_{-20}$ and $614^{+203}_{-149}$ such systems exist within 2 kpc, respectively. This framework will enable detailed population-level constraints on a wide range of systems identified from the much larger catalog of astrometric orbits expected from
Gaia DR4.
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All authors Natsuko Yamaguchi, Kareem El-Badry, Reed Essick, Amanda Farah, Cheyanne Shariat, Sahar Shahaf
Astrophysics of Galaxies
An Off-Nuclear Tidal Disruption Event Discovered At Late Times: The Case Of TDE 2023mfm
Itai Sfaradi, Ryan Chornock, Yuhan Yao et al. (+24 more)
We present the discovery and analysis of the optically selected
tidal disruption event (TDE) 2023mfm, which originates from a wandering massive black hole (MBH) in a massive ($\sim 10^{11} \,$M$_{\odot}$)
galaxy hosting a central low-luminosity active
galactic nucleus (AGN). Our analysis of the ZTF, Lick, Keck, Swift, Chandra, XMM-Newton, HST, and VLA observations reveals that TDE 2023mfm is a TDE-H from a $10^{6.2 \pm 0.5}\,$M$_{\odot}$ black hole which is offset by $0.66 \pm 0.02$" from the center of its host
galaxy, corresponding to a projected distance of $1.08 \pm 0.04$ kpc. TDE 2023mfm displays all the traits of optically selected TDEs. The emission remains hot, $T_{\rm bb} \sim 22,000 \pm 1,000$ K, for more than a month after peak, and the $g$-band light curve peaks at $\left( 2.24^{+0.10} _{-0.11} \right) \times 10^{43} \, \rm erg \, s^{-1}$ and stays above half-maximum luminosity for $47.8^{+3.7}_{-3.5}$ days. The late-time optical-to-UV emission observed with the HST suggests the presence of an unresolved
stellar population with a
stellar mass of $10^7-10^8\,$M$_{\odot}$ at the position of the TDE, possibly being a low-mass
dwarf galaxy or a stripped
galaxy from a previous minor merger. The
radio emission from TDE 2023mfm emerges at least a year after optical discovery, and we find it likely that it originates from a delayed
outflow, however, further observations are needed to determine its true origin.
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All authors Itai Sfaradi, Ryan Chornock, Yuhan Yao, Erica Hammerstein, Jean Somalwar, Raffaella Margutti, Huei Sears, Robert Stein, Natalie LeBaron, Adelle J. Goodwin, Sjoert van Velzen, Matthew J. Graham, Kate D. Alexander, Nayana A. J., Edo Berger, Jonathan Carney, Yvette Cendes, Collin T. Christy, Walter W. Golay, Wenbin Lu, James C. A. Miller-Jones, Charlotte Ward, Eli Wiston, Tracy X. Chen, Mansi M. Kasliwal, Frank J. Masci, Jesper Sollerman
High Energy Physics (Theory)
D-branes and orientifolds on quasicrystalline orbifold backgrounds
Antony Wendels
We construct and analyse orientifold descendants of a six-dimensional type IIB $\mathbb Z_{12}$ quasicrystalline orbifold. The parent background is defined by a Narain-
lattice automorphism that is not crystallographic on the
geometric torus. We determine the closed-string spectrum and twisted-sector orbit structure, construct a compatible unoriented projection, and compute the Klein bottle, annulus and Möbius strip amplitudes. Tadpole cancellation selects boundary orbits that admit a partially T-dual description as D7-branes at angles and fixes the Chan-Paton gauge group and massless spectrum. The resulting supersymmetric six-dimensional
vacuum satisfies the irreducible anomaly constraints, its reducible anomaly
polynomial factorizes through the Green-Schwarz mechanism, and its anomaly
lattice obeys the Kim-Shiu-Vafa string-probe bound. We also construct a Brane Supersymmetry Breaking descendant with a perturbatively tachyon-free rigid branch, and a freely acting five-dimensional orientifold whose two decompactification limits reproduce a
geometric type IIA $\mathbb Z_3$ orientifold and an antisymmetric type IIB $\mathbb Z_4$ orientifold. These examples show that quasicrystalline closed-string backgrounds can admit controlled perturbative open-string completions with non-trivial boundary and crosscap sectors.
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Astrophysics of Galaxies
A Systematic Assessment of Total Stellar Mass Measurements with Spatially Resolved Photometry and Medium Bands at 1 < z < 9: The Impact of Mass-to-Light Variations and Outshining
Naadiyah Jagga, Adam Muzzin, Visal Sok et al. (+16 more)
JWST NIRCam spatially resolved photometry enables studies of
galaxies'
stellar populations and
stellar masses on sub-kpc scales. We use JWST (CANUCS, Technicolor, JUMPS) and HST data, covering wide- and medium-band UV-IR filters to study the
stellar mass bias between spatially resolved and integrated photometry of $\sim$3000
galaxies at 1 $<z_{\mathrm{phot}}<$ 9. The 2D parameter maps reveal spatial variations in
stellar mass and populations, showing that integrated measurements systematically underestimate
stellar masses. We find that the
stellar mass bias remains small for
galaxies with specific
star formation rate $\mathrm{sSFR} < 10^{\mathrm{-9}}$ yr$^{\mathrm{-1}}$, but increases for
galaxies with $\mathrm{sSFR} > 10^{\mathrm{-8.5}}$ yr$^{\mathrm{-1}}$. For these high-sSFR
galaxies, the median offset reaches $\Delta \log_{\mathrm{10}} (M_{\ast})$ $\sim$ -0.36 dex with the largest bias occurring in low-mass ($M_{\ast} \leq 10^{\mathrm{ 9.5}} M_{\odot}$)
galaxies. These results are consistent with the outshining of older populations by recent
star formation. High-sSFR
galaxies also show spatial variations in their mass-to-light ratios ($M_{\ast}/L_{V}$): the
stellar mass bias decreases with $\sigma[\log_{\mathrm{10}}(M_{\ast}/L_{V})]$ for
galaxies with $10^{\mathrm{-8}} \leq \mathrm{sSFR}[\mathrm{yr}^{\mathrm{-1}}] < 10^{\mathrm{-9}}$, with the strongest trend for $10^{\mathrm{-7}} \leq \mathrm{sSFR}[\mathrm{yr}^{\mathrm{-1}}] < 10^{\mathrm{-8}}$, quantified by the Spearman correlation coefficient $\rho_{\rm S}=-0.37$. While medium bands are important for constraining
stellar masses from integrated photometry, spatially resolved photometry reduces the impact of their absence, with dispersion offsets of $\Delta \log_{\mathrm{10}} (M_{\ast})$ = 0.33 dex for integrated photometry but 0.15 dex for resolved photometry when only wide-bands are included.
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All authors Naadiyah Jagga, Adam Muzzin, Visal Sok, Vivian Yun Yan Tan, Ghassan Sarrouh, Kartheik Iyer, Yoshihisa Asada, Chris J. Willott, Maruša Bradač, Nicholas S. Martis, Gaël Noirot, Gregor Rihtaršič, Marcin Sawicki, Sunna Withers, Jacqueline Antwi-Danso, Samantha C Berek, Danilo Marchesini, Maya Merchant, Katherine Myers
High Energy Astrophysical Phenomena
Bayesian Evidence for Inspiraling Hotspot Motion in the Galactic Center
Pablo Ruales, Maciek Wielgus, Delilah E.A. Gates et al. (+1 more)
During flaring episodes, polarimetric observations of the
Galactic Center black hole Sagittarius A* (Sgr A*) reveal evolving, loop-like trajectories in the Stokes Q-U plane, the so-called Q-$U loops. Keplerian models of transiently energized orbiting features, hotspots, have been employed to reproduce these polarimetric signatures. In this work, we develop a
Bayesian framework to infer the time-dependent kinematics of the hotspot from polarized light curves, using a general prescription for its motion. We model the emitting region's trajectory as a continuous, piecewise sequence of K kinematic segments, each described by radial and azimuthal velocity parameters. We perform analyses with K=1,2,3 and compare these models to millimeter-wavelength ALMA observations of Sgr A* from 2017 April 11 that include two subsequent Q-U loops, extending the observational constraints on the kinematics. We examine the effects of the local
magnetic field geometry, spectral index, and kinematic profile of the hotspot's trajectory on the polarized signal. We find statistically significant evidence that the emitting region follows a non-geodesic inspiraling trajectory, and this preference over a strictly Keplerian orbit strengthens sharply when a longer data segment is modeled. The inspiraling non-Keplerian models are preferred to a purely Keplerian model based on both the
Bayesian log-evidence comparison and the reduced chi-square statistic. Our results offer new insight into the nature of flaring events in the
Galactic Center and the episodically produced hotspots associated with them.
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All authors Pablo Ruales, Maciek Wielgus, Delilah E.A. Gates, Alejandro Cardenas-Avendano
High Energy Astrophysical Phenomena
Hierarchical Bayesian Inference on the intrinsic event rate of Type I gamma-ray bursts from the Fermi/GBM catalogue
Cao Tian-Yong, Yi Shu-Xu, Du Yun-Fei et al. (+2 more)
The intrinsic event-rate of Type I gamma-ray bursts (GRBs) as a function of
redshift, provides a probe for binary
neutron star (BNS) mergers population. However, the above-mentioned inference is complicated by instrumental selection effects, the lack of
redshift measurements for the majority of GRBs, and uncertainties in jet geometry. In this work, we applied a hierarchical
Bayesian inference framework to the
Fermi/GBM Type I GRB catalogue to reconstruct the underlying event-rate population. This framework accounts for the selection effects and marginalizes over the limited-information posteriors of individual GRB
redshifts and jet structures. The population model uses parameterized luminosity function, distribution of jet structure parameters, the Madau-Dickinson
star-formation rate and a delay-time distribution of BNS mergers. The posterior distribution of the hyperparameters in the model are to be inferred, using a GPU-accelerated MCMC
algorithm. The intrinsic event rate density as function of
redshift is constrained up to $z=5$, which a local rate density of \(R_0 = 22.6^{+15.0}_{-10.6}\,{\rm Gpc^{-3}\,yr^{-1}},\), which is consistent with the latest gravitational-wave measurements.
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All authors Cao Tian-Yong, Yi Shu-Xu, Du Yun-Fei, Yorgancioglu S. Emre, Xiong Shao-Lin
General Relativity and Quantum Cosmology
Spectral instabilities in the time domain
Taillte May, Adrien Kuntz, Nicola Franchini et al. (+2 more)
We investigate the effect of a spectral instability on the time domain waveform using a one-dimensional double Pöschl-Teller model. By analytically following successive scatterings between the primary potential barrier and a weak, spatially separated perturbation, we identify a secular contribution that first appears after one causal round trip between the barriers. Before the first echo, all overtones remain at their unperturbed frequencies. After the first echo reaches the observer, there is a secular, linear-in-time correction. When this correction is perturbative, it can be interpreted as a shift of the quasinormal mode frequency. In that case, we show that its coefficient reproduces the frequency-domain result. More generally, it generates finite-time effective frequencies that need not coincide with either the unperturbed or fully perturbed quasi-normal mode spectrum. We confirm the results of our analytic calculation using numerical time-domain evolutions.
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All authors Taillte May, Adrien Kuntz, Nicola Franchini, Valentin Boyanov, Vitor Cardoso
Astrophysics of Galaxies
CHAMPS: The COSMOS High-Redshift ALMA-MIRI Population Survey - A New Census of the Dusty Early Universe
Andreas L. Faisst, Felix Martinez III, Jeyhan S. Kartaltepe et al. (+86 more)
Understanding how
dust forms and evolves over
cosmic time is a key open problem in extragalactic astrophysics.
Galaxies in the early Universe were once thought to be mostly
dust-poor, but recent discoveries of heavily
dust-obscured
galaxies near the Epoch of Reionization challenge models of early
dust production and raise new questions about the true
cosmic star formation rate density. In this paper, we present the COSMOS High-
Redshift ALMA-MIRI Population Survey (CHAMPS), which sheds light on the dusty early universe at z>4. CHAMPS is a new 144h ALMA 1.2mm (band 6) large program mapping the combined JWST/NIRCam+MIRI footprint in the COSMOS field. It covers 0.2deg2 with a synthesized beam size of 1.1" and a sensitivity of 0.14mJy/beam. It is complemented, alongside JWST, by ancillary X-ray, UV, optical, sub-mm, and
radio data. CHAMPS, optimized as a blind survey, detects above 5$\sigma$ approximately 385 individual dusty high-
redshift sub-mm sources, 68 dusty AGN, and a dozen dusty
galaxies at z>6. The
galaxies are largely not detected in JWST/F150W, making them prototypical near-IR dark
galaxies. We showcase three of the highest-
redshift most dusty and massive candidate
galaxies detected in CHAMPS with
redshifts up to z=7.5. CHAMPS also enables stacks of thousands of
galaxies grouped in bins of various physical parameters. Its sub-mm coverage of
dust-attenuated JWST-identified
galaxies provides robust constraints on
dust masses and obscured
star formation rates to study early
dust formation and
evolution. In addition, CHAMPS enables a blind search for luminous CO line emitters at z=0.4-2.7 and [CII]158$\mu$m emitters at z=6.7.
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All authors Andreas L. Faisst, Felix Martinez III, Jeyhan S. Kartaltepe, Manuel Aravena, Caitlin M. Casey, John D. Silverman, Sune Toft, Ezequiel Treister, Jorge A. Zavala, Hiddo S. B. Algera, Andrew J. Battisti, Michele Catone, Jaclyn B. Champagne, Yingjie Cheng, Rasha M. Samir, Maximilien Franco, Kyle Finner, Carter Flayhart, Fabrizio Gentile, Ghassem Gozaliasl, Santosh Harish, Shuowen Jin, Yu-Heng Lin, Lun-Jun Liu, Arianna S. Long, Crystal L. Martin, Bahram Mobasher, Francesca Pozzi, Huimin Qu, Chuan Tian, Mattia Vaccari, Wuji Wang, Can Xu, Hollis B. Akins, Micaela B. Bagley, Angela Bongiorno, Kevin C. Cooke, Olivia R. Cooper, Simon Hempel-Costello, Ivan Delvecchio, Nicole E. Drakos, Andrea Enia, Steven L. Finkelstein, Seiji Fujimoto, Steven Gillman, Carlos Gomez-Guijarro, Jorge Gonzalez-Lopez, Michaela Hirschmann, Olivier Ilbert, Kei Ito, Knud Jahnke, Boris S. Kalita, Daichi Kashino, Vasily Kokorev, Thomas S.-Y. Lai, Erini Lambrides, Daizhong Liu, Georgios E. Magdis, Vincenzo Mainieri, Sinclaire M. Manning, Claudia Maraston, Richard Massey, Henry Joy McCracken, Jed McKinney, Wilfried Mercier, Thibaud Moutard, Masafusa Onoue, Louise Paquereau, Alvio Renzini, Jason Rhodes, R. Michael Rich, Brant E. Robertson, Giulia Rodighiero, David B. Sanders, Claudia M. Scarlata, Nick Scoville, Kartik Sheth, Marko Shuntov, Laura Sommovigo, Martin Sparre, Tomoko L. Suzuki, Margherita Talia, Benny Trakhtenbrot, Francesco Valentino, Brittany N. Vanderhoof, Eleni Vardoulaki, Aswin P. Vijayan, Katherine E. Whitaker, Stephen M. Wilkins
Cosmology and Nongalactic Astrophysics
Enhanced density fluctuations: consequences for stellar dynamics and dark matter substructure
Wenzer Qin, David E. Kaplan and Neal Weiner
Enhanced density fluctuations form early dark matter
halos, which serve as early gravitational potential wells for
baryons. These
baryons can then condense to form
stars and black holes at high
redshifts, $1+z \gtrsim 100$. Larger density fluctuations result in denser
halos with higher virial temperatures; hence, a
halo at a mass that is below the threshold for forming
stars under standard astrophysical expectations may form astrophysical objects if its initial density is higher than expected, although the exact threshold for compact object formation is subject to large astrophysical uncertainties. We outline the conditions under which enhanced density fluctuations form dark (
star-less)
halos, early
galaxies, or even
star clusters. Using toy model enhancements to the
primordial power spectrum that have been shown to explain the abundances of “little red dots", along with our fiducial set of astrophysical parameters, we show that the number of clusters initially captured by the Milky Way is highly sensitive to the shape of the enhancement, with the narrowly peaked enhancement resulting in $50$ clusters and the step-function enhancement resulting in $\sim 4.1 \times 10^5$. The initial
stellar masses of the clusters is also $O (100) \,M_\odot$, although this range is also dependent on the shape of the enhancement. In addition, the abundance of dark matter subhalos with masses greater than $10^7 \, M_\odot$ can be enhanced by as much as a factor of $\sim 6.5$ and is denser than in $\Lambda$CDM, which will increase their detectability in future
stellar stream surveys such as the Via Project.
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Quantum Physics
Out-of-time-order Correlators in Volcano potentials
Aritra Banerjee, Reetik Jangir and Rishant Sharma
The out-of-time-order correlator (OTOC) has emerged as an important diagnostic for
quantum information scrambling and a key signature of
quantum chaos. In this work, we discuss out-of-time-order correlators, analytically and numerically, for the so-called Volcano potentials. This family of potentials parametrically interpolates between bounded wells and confining walls, and includes Pöschl-Teller as a specific case. Through a combination of numerical diagonalization and semiclassical analysis, we investigate various regimes of the potential parameter regimes containing regions of both positive and negative
curvatures. Moreover, we demonstrate in this case that short-time exponential growth of the OTOC does not necessarily signal global
quantum chaos; instead, it correlates with the sampling of negative
curvature regions by excited states.
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Instrumentation and Methods for Astrophysics
Divergence-free magnetohydrodynamics on a moving mesh
Volker Springel, Alexander C. Mayer and Rüdiger Pakmor
Magnetic fields are ubiquitous in the Universe and play an important role in many astrophysical processes, such as
star formation and the
evolution of
galaxies. Hydrodynamical simulation methods that account for ideal magnetohydrodynamics (MHD) are however challenged by the need to achieve numerical stability and physical consistency. Both can be compromised by the occurrence of non-vanishing local divergence errors in the
magnetic field. Different approaches to either eliminate or reduce these discretization errors are in widespread use, including constrained transport or divergence cleaning techniques. However, thus far a divergence-free Galilean invariant formulation of MHD that can be readily applied in Lagrangian codes has been an elusive goal. Here we revisit the use of the vector potential for evolving the
magnetic field on an unstructured moving-mesh and show how a particular gauge choice combined with a suitably discretized integration scheme provides a stable and accurate formulation of MHD. Our method combines a finite-difference
evolution of a
cell-centred vector potential with a finite volume representation of the other fluid quantities, and is realized in the moving-mesh code AREPO. The new approach is fully Galilean invariant and therefore shows vanishing errors for classic problems such as field loop advection. We demonstrate good accuracy and stability when our scheme is applied to various test problems and to practical applications in 3D, including when local timesteps and adaptive mesh refinement and derefinement are used.
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Cosmology and Nongalactic Astrophysics
Satellite stellar-to-halo mass relations in primordial black hole universes
Patricio Colazo, Nelson Padilla and Federico Stasyszyn
Primordial black holes (PBHs), in particular with a fixed-conformal-time (FCT) extended mass function, can modify small-scale structure through enhanced
primordial power and discreteness-driven Poisson fluctuations, altering subhalo abundances and internal structure. We study their effects on satellite
stellar-to-
halo mappings, bound-remnant compactness, and the link to compact dark perturbers. We compare two dark-matter-only simulations, a fiducial CDM run and an FCT/PBH run. As these runs form no
galaxies, we construct an approximate abundance-based
stellar-to-
halo mapping using the progenitor virial mass at last isolation. The CDM mapping is anchored to a
redshift-dependent abundance-matching
stellar-to-
halo relation, and the FCT mapping is derived from the relative cumulative subhalo abundances. We use resolved SOAP (V_max) and (R_max) to characterize present-day subhalo compactness, supplemented by a subgrid estimate of mass segregation in the unresolved PBH population. FCT enhances the subhalo abundance in a mass-dependent way, but abundance-based
stellar-mass reassignment makes satellite
stellar-mass functions weak discriminants. Internal structure is a stronger test: FCT subhaloes are more compact and have larger NFW-reconstructed enclosed masses at fixed radius, strengthening a Too-Big-To-Fail-like tension if all compact subhaloes host luminous satellites. FCT subhaloes also form earlier, accounting for much of the low-mass compactness difference, while PBH mass segregation adds a central perturbation with typical \mu ~ 0.4-0.5. Neither effect fully explains the resolved FCT compactness enhancement. Changes in the
galaxy–
halo mapping can partly hide the enhanced FCT subhalo abundance in satellite counts, whereas internal dynamics remain more discriminating. Satellite abundances, dynamics, and compact dark perturbers are complementary probes of PBH-induced small-scale structure.
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Astrophysics of Galaxies
COSMOS-3D: Diverse Environments and Hot-dust Signatures among Dusty Star-forming Galaxies at $z$ = 4.9-7.2
Siwei Zou, Manuel Aravena, Shaoze Geng et al. (+20 more)
Dusty
star-forming
galaxies (DSFGs) are expected to trace early massive-
halo assembly, but the connection between
dust-obscured
star formation, morphology, hot
dust, and environment remains unclear at $z$>4. We combine JWST/NIRCam F444W grism spectroscopy from COSMOS-3D with MIRI F1000W/F2100W imaging and a mixed ALMA-selected and ALMA-followed dusty-
galaxy sample from CRISTAL, CHAMPS, REBELS, and A3COSMOS to study 18 DSFGs or DSFG candidates at z=4.9-7.2. We compare their environments with the parent spectroscopically confirmed emission-line sample and the COSMOS-Web photo-z
galaxy sample using separate and combined overdensity
estimators. The parent narrow-line H$\alpha$ sample has a median observed,
dust-uncorrected ${\rm SFR}_{\rm H\alpha}=11.7 M_\odot~{\rm yr^{-1}}$. Within R=0.5 pMpc, DSFGs have a median $\delta_{\rm spec+phot}=0.92^{+0.06}_{-0.16}$, compared with $0.80^{+0.05}_{-0.04}$ for HAEs, with a stronger contrast on smaller scales. The strongest compact overdensities are associated with merger/interacting morphology: merging DSFGs reach $\delta_{\rm spec+phot}=4.70^{+1.61}_{-1.51}$ within R=0.5 pMpc. In contrast, MIRI-bright DSFGs do not show an enhanced number of nearby visible H$\alpha$-emitting companions, and their F2100W fluxes are difficult to explain with the 3.3 $\mu$m PAH feature alone, suggesting an additional hot-
dust component. These results are consistent with a possible phase-dependent picture in which the compact line-emitter core, merger-driven dusty phase, and MIRI-bright hot-
dust phase need not be spatially or temporally identical during early structure growth.
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All authors Siwei Zou, Manuel Aravena, Shaoze Geng, Romain A. Meyer, Jianwei Lyu, Jaclyn B. Champagne, Jia-Sheng Huang, Andreas L. Faisst, Shuqi Fu, Andrew J. Battisti, Hiddo Algera, Caitlin M. Casey, Xiaohui Fan, Maximilien Franco, Ghassem Gozaliasl, Linhua Jiang, Koki Kakiichi, Darshan Kakkad, Zihao Li, Lun-Jun Liu, Felix Martinez III, Jorge A. Zavala, Rasha M. Samir
Quantum Physics
Asymptotically Optimal Mixed-State Cloning
Jiani Fei and Jinzhao Wang
We determine asymptotic global fidelities of cloning generic mixed states with simple (non-degenerate) full-rank spectra. In fixed dimension $d$, let $n$ inputs and $m_n$ outputs satisfy $m_n/n\to\gamma>1$. For a known simple full-rank spectrum $p_1>\cdots>p_d>0$, we prove that the optimal root fidelity between the entire output and the product target state is $$ F_\rm{orb}(\gamma,p) =\prod_{i<j} \frac{\sqrt{\gamma}+\sqrt{q_{ij}(\gamma-1+q_{ij})}} {\gamma+q_{ij}}, \qquad q_{ij}=\frac{p_j}{p_i}. $$ When the spectrum is unknown, one spectrum-independent cloner attains $$ F_\rm{univ}(\gamma,p) =\left(\frac{2\sqrt\gamma}{1+\gamma}\right)^{(d-1)/2} F_\rm{orb}(\gamma,p), $$ uniformly on compact subsets of the simple full-rank chamber and is minimax optimal. The two factors quantify spectral and eigenbasis uncertainty. Our channels combine classical processing of Schur–Weyl labels with a covariant Cartan-sector channel. Local asymptotic normality and a Gaussian fidelity bound against arbitrary channels yield the converses. For flat projector states $\rho=P/r$, with $P$ a rank-$r$ orthogonal projector, we separately prove the optimum $\gamma^{-r(d-r)/2}$. Furthermore, we estimate the exact asymptotic fidelity of purify–clone–trace (PCT), and show that our cloners strictly outperform PCT at every fixed gain for simple full-rank spectra and rank-$r$ projector states with $1<r<d$.
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High Energy Physics (Theory)
Control Problem of de Sitter Vacua with T-brane Uplift
Daniel Junghans
T-branes have been argued to provide a consistent uplift to de Sitter
vacua in the context of the LARGE-volume scenario of type IIB string theory. We point out that this construction suffers from a serious control problem: the string-frame volume is bounded from above by a number that depends only on the
topology of the Calabi-Yau orientifold and is often $\mathcal{O}(1)$ or smaller. This observation immediately rules out controlled de Sitter
vacua in many models with $h^{1,1}=2$ if the non-perturbative superpotential is generated by D3-brane instantons. We give evidence that similar conclusions apply for $h^{1,1}>2$ and show this explicitly for two models with $h^{1,1}=4$. Our volume bound is seemingly less severe in models where the non-perturbative superpotential is generated by gaugino condensation. However, we study $\mathcal{O}(600)$ such models and find that, although de Sitter solutions with large volumes are naively possible there, they suffer from uncontrolled warping corrections whose volume suppression is cancelled by other factors, in particular large charges. We also observe that the models with the smallest warping corrections within our set have very small tadpoles and at the same time require a fine-tuned string coupling and flux superpotential, which may indicate an additional problem with the axio-dilaton/complex-structure-
moduli stabilization. Finally, we point out an independent challenge related to the stabilization of the brane
moduli. Our various results lead us to conclude that it is unlikely that the scenario of T-brane uplifting can be realized in string theory in a self-consistent manner.
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Statistical Mechanics
Nonreciprocal Chiral Automata
Andrew A. Allocca, Armin Rahmani, Pouyan Ghaemi et al. (+1 more)
Odd pressure is a parity-odd transport coefficient that gives an isotropic pressure response to vorticity in compressible two-dimensional fluids. By asymmetrically coupling vortical and compressional modes, it provides a direct mechanism for a nonreciprocal hydrodynamic response reminiscent of several biological systems. Yet microscopic models realizing odd pressure as a transport coefficient are relatively scarce. Here, we construct one such model using a
lattice-gas cellular automaton based on the Frisch-Hasslacher-Pomeau II model with rest particles and
chiral collisions, whose Chapman-Enskog coarse-graining produces a nonzero odd pressure coefficient. The key ingredient is a local parity-breaking collision that weakly rotates moving particles in the presence of a rest particle. At hydrodynamic scales, this microscopic rule acts as an effective
magnetic field, converting the model's bulk viscosity into odd pressure. More generally, we derive expressions relating
Hall viscosity, odd pressure, and odd torque to their parity-even counterparts in our model.
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All authors Andrew A. Allocca, Armin Rahmani, Pouyan Ghaemi, Sriram Ganeshan