Strongly Correlated Electrons
Tensor network study of deconfined quantum criticality in a one-dimensional spin-phonon model
Anton Romen, Josef Willsher, David Hofmeier et al. (+2 more)
Deconfined
quantum critical points (DQCPs) describe continuous transitions between ordered phases beyond the Landau paradigm. A simple example is the Néel antiferromagnet (AFM) to valence bond solid (VBS) transition in a 1D
antiferromagnetic $J_1-J_2$ model. In analogy to the
spin-Peierls instability of critical
spin chains, DQCPs are predicted to be unstable towards
lattice distortions below a critical
phonon frequency. In this work, we use tensor network simulations to investigate this instability in the
antiferromagnetic $J_1-J_2$ model coupled to
lattice vibrations. We confirm the stability of DQCP for large
phonon frequencies and demonstrate that the transition turns strongly first-order below a critical frequency. The instability is caused by a reduction of the Luttinger parameter due to
spin-
phonon interactions and we identify the effective theory of the behavior as the double sine-Gordon model. The same effective theory is known to describe the classical Ashkin-Teller model, which enables us to show that the critical endpoint is in the four-state Potts universality class. We argue based on non-linear bosonization that the sign of the double-frequency term is fixed, which provides a microscopic justification for the first-order transition. Furthermore, we provide quantitative numerical scaling results for the
phonon spectral function, offering an experimental signature to probe DQCP-
phonon coupling in low-dimensional materials.
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All authors Anton Romen, Josef Willsher, David Hofmeier, Johannes Knolle, Michael Knap
High Energy Physics (Phenomenology)
Reweighting Adversarial Networks for Unbinned Unfolding
Umar Sohail Qureshi, Krish Desai, Jesse Thaler et al. (+1 more)
Differential cross sections are the currency of scientific exchange in particle and
nuclear physics. Recently, machine learning methods have enabled unbinned and high-dimensional cross section measurements through new approaches to unfolding. A key challenge with unfolding is that it is a bi-level optimization problem where constraints are available at the detector level while the target is at the particle level, linked by a
stochastic detector response. Further complications arise when the particle-level and detector-level distributions have non-overlapping or only partially overlapping support, which can destabilize training and degrade unfolding performance. In this paper, we introduce a new unbinned unfolding technique called the Reweighting
Adversarial Network (RAN), which can be viewed as a generalization of the Moment Unfolding protocol to accommodate full phase-space unfolding. RANs address the bi-level optimization problem through a particle-level reweighting function steered by a Wasserstein critic at the detector level. RANs do not require overlapping support at the detector level, nor multiple iterations of training. We evaluate the performance of RANs with Gaussian data and jet substructure studies, including cases specifically designed to stress test the method under vanishing support overlap. We demonstrate that RANs outperform state-of-the-art methods in accuracy and have a lower computational overhead.
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All authors Umar Sohail Qureshi, Krish Desai, Jesse Thaler, Benjamin Nachman
High Energy Physics (Theory)
Boundary Layers and One-point Functions in the Presence of Monodromy Defects
Hugo Calvo Castro, Ignacio Carreño Bolla and Diego Rodriguez-Gomez
We study one-point functions of composites of charge $e$ operators in the presence of a monodromy defect for a $U(1)$ global
symmetry with monodromy $\beta$. We first compute these in free massless and massive theories, recovering in the former case the known $\sin(e\pi\beta)$ dependence and obtaining in the latter a $\sin^2(e\pi\beta)$ dependence. We then turn to holography and compute 1-point functions for operators $O$ of charge $J=\Delta$ in $\mathfrak{su}(N)$ $\mathcal{N}=4$ SYM in the presence of a monodromy defect for a $U(1)\in SO(6)_R$. From a WKB analysis in large $\Delta$ we recover the structure of standard and anchored saddles previously found in the literature, finding that, to subleading order in $1/\Delta$, the anchored regime is resolved by a boundary layer effect. Finally, using heat kernel methods, we determine the monodromy dependence of the induced 1-point function for the composite $O^{\dagger}O$, finding a smooth $\sin^2(J\pi\beta)$ behavior.
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General Relativity and Quantum Cosmology
Radial Oscillations of Viscous Stars at Finite Temperature
Amanda Guerrieri, Gabriel S. Rocha, Gabriel S. Denicol et al. (+1 more)
We study the radial oscillation spectrum of relativistic
stars within Israel-Stewart and Navier-Stokes theories, extending previous analyses to include heat
diffusion and a thermodynamically consistent finite-temperature equation of state. The inclusion of heat flux gives rise to a distinct thermal sector in the mode spectrum, whose structure closely mirrors the dispersion relations of an infinite dissipative fluid. Within Israel-Stewart theory, the thermal modes transition from purely damped to propagating behavior above a critical overtone number, providing a finite-size realization of relativistic second sound in compact
stars. Remarkably, the finite
stellar geometry can push even the fundamental thermal mode into the propagating regime – a feature with no continuum analogue. For the class of equations of state considered here, where finite-temperature corrections enter as controlled, Sommerfeld-type perturbations of a cold polytrope, the thermal sector couples only weakly to the ordinary fluid oscillation spectrum, with the coupling being of second order in a suitable temperature parameter. We further show that the discrete
stellar spectrum is well captured by an analytic ansatz constructed from the flat-spacetime dispersion relations, with the
star's finite radius discretizing the continuous mode structure. Our results complete the analysis of radial oscillations of viscous
stars by incorporating the last remaining dissipative degree of freedom within the Israel-Stewart framework.
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All authors Amanda Guerrieri, Gabriel S. Rocha, Gabriel S. Denicol, Raissa F. P. Mendes
Cosmology and Nongalactic Astrophysics
Halo mass functions in mixed cold and fuzzy dark matter models
Sarah C. Johnston, Simon May, Tibor Dome et al. (+5 more)
We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the
halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight
axion-like component with mass $m =10^{-24.5} \mathrm{eV}$ constitutes a fraction $f \leq 0.3$ of the total dark matter. To enable consistent
halo identification in mixed-species scenarios, we develop a grid-based
halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass
haloes and modifying the HMF in a manner dependent on
redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on
redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored ($1 \leq z \leq 4$, $f \leq 0.3$). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation.
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All authors Sarah C. Johnston, Simon May, Tibor Dome, Sownak Bose, Alastair Basden, Carlton Baugh, Anastasia Fialkov, Alex Tocher
Quantum Physics
A superconducting surface-code processor with lattice-surgery logical operations
Yanzhe Wang, Fanhao Shen, Haipeng Xie et al. (+31 more)
Fault-tolerant logical operations are fundamental for scalable
quantum computation. Here, we report the experimental realization of
lattice-surgery operations between a pair of distance-three surface-code logical
qubits on a planar superconducting processor. During repeated syndrome extraction cycles, the logical
qubits exhibit per-cycle error rates of $0.0365(2)$ and $0.0282(1)$, respectively, after leakage events are rejected. By leveraging joint initialization and
lattice splitting, we deterministically prepare a logical Bell state, confirming genuine bipartite
entanglement via the error-corrected logical state fidelity. We further execute a two-
qubit Deutsch-Jozsa
algorithm at the logical level to demonstrate algorithmic utility in a fault-tolerant framework. Finally, to achieve universal control, we implement magic-state injection and gate teleportation to realize continuous non-Clifford rotations about the logical $X$ axis. For the logical $R_{X}(\pi/4)$ gate, we achieve a logical gate fidelity of $0.943_{-9}^{+10}$ conditioned on the absence of detected errors. These results establish
lattice surgery as a practical and versatile paradigm for logical computation in near-term surface-code architectures, representing a critical milestone toward scalable fault-tolerant
quantum advantage in superconducting
circuits.
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All authors Yanzhe Wang, Fanhao Shen, Haipeng Xie, Aosai Zhang, Yu Gao, Chuanyu Zhang, Xuhao Zhu, Feitong Jin, Yiren Zou, Ning Wang, Zhengyi Cui, Zehang Bao, Zitian Zhu, Jiarun Zhong, Gongyu Liu, Jia-Nan Yang, Yihang Han, Yiyang He, Jiayuan Shen, Han Wang, Jiahua Huang, Xinrong Zhang, Sailang Zhou, Hang Dong, Jinfeng Deng, Yaozu Wu, Zixuan Song, Hekang Li, Zhen Wang, Chao Song, Qiujiang Guo, Pengfei Zhang, H. Wang, Ying Li
Quantum Physics
Quantum-stabilized patterns in a vector Hopfield network
Richard D. Barney, Sharba Bhattacharjee, Victor Galitski et al. (+2 more)
We introduce the
quantum vector Hopfield network, in which patterns are formed by orientations of
quantum vector
spins;
quantum dynamics arise intrinsically from the non-commutativity of the
spin operators. We derive the equations of state and the phase diagrams for this network as well as its classical counterpart. We find that
quantum fluctuations, surprisingly, stabilize the stored patterns. Both the critical
retrieval temperature and the target pattern overlap are enhanced relative to the classical network. Additionally, we find that this enhancement grows with pattern loading up to network capacity. We interpret this effect as an analog of
quantum order-by-disorder, a mechanism by which
quantum fluctuations promote the formation of ordered phases. These findings offer a new route to
quantum-enhanced associative
memory.
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All authors Richard D. Barney, Sharba Bhattacharjee, Victor Galitski, Kartiek Agarwal, Ivar Martin
High Energy Physics (Theory)
Instanton-Induced Closed-String Amplitudes in Minimal Superstring Theory at Subleading Order
Jyotirmoy Barman, Rishabh Kaushik, Raghu Mahajan et al. (+2 more)
We compute the disk one-point function, the disk two-point function, and the annulus one-point function of the cosmological constant operator in the type 0A and type 0B minimal superstring theories with (1,1) ZZ instanton boundary conditions. The
moduli-space integrals appearing in the disk two-point function and the annulus one-point function have divergences associated with open-string-channel degenerations, which must be regulated using open-closed string field theory. The definition of the string field theory interaction vertices requires a choice of locations for the picture-changing operators, which we specify in detail. After carefully taking into account all contributions, including those from vertical integration, we find that the results precisely match the expectations from DDK-KPZ scaling. Our technical results on the detailed construction of interaction vertices are a first step toward understanding the analogous quantities in the ten-dimensional type IIB superstring, where one also needs to understand how to treat the bosonic and fermionic collective coordinates at subleading order.
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All authors Jyotirmoy Barman, Rishabh Kaushik, Raghu Mahajan, Chitraang Murdia, Ashoke Sen
High Energy Astrophysical Phenomena
VLA Observations Confirm AT 2023mfm as an Off-nuclear Tidal Disruption Event
Wenkai Li, Collin T. Christy, Kate D. Alexander et al. (+15 more)
We report new
radio observations of the
tidal disruption event (TDE) AT 2023mfm, which we identified as a high-confidence candidate in a systematic search for off-
nuclear TDEs. High-resolution NSF Karl G. Jansky Very Large Array C-band (6 GHz) imaging resolves two
radio sources: one consistent with the host-
galaxy nucleus and one offset by $0.651\pm0.036^{\prime\prime}$ ($1.06\pm0.06$ kpc), consistent with the Zwicky Transient Facility and Pan-STARRS1 positions of AT 2023mfm. These observations confirm the off-
nuclear nature of AT 2023mfm, demonstrating the power of high-resolution
radio imaging to validate off-
nuclear TDE candidates and reveal hidden off-
nuclear massive black holes.
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All authors Wenkai Li, Collin T. Christy, Kate D. Alexander, Itai Sfaradi, Xinya Huang, Ning Jiang, Tanmoy Laskar, Andrew Mummery, Noah Franz, Adelle J. Goodwin, Walter W. Golay, Raffaella Margutti, Ryan Chornock, Jiazheng Zhu, Sjoert van Velzen, Yvette Cendes, Wenbin Lu, Jimmy Lynch
Astrophysics of Galaxies
The accretion history of the Milky Way V. The kinematics of most globular clusters trace the merger epochs
Istiak Akib, François Hammer and Yanbin Yang
Several studies have associated globular clusters (GCs) with former
Galactic accretion events by comparing their positions in the energy-angular momentum ($E$-$L_z$) plane, an approach further supported by similarities in their age-
metallicity relations. However, recent merger simulations suggest that GCs initially associated with the
Gaia-Sausage-Enceladus (GSE) disc may have lost their orbital energy and thus may not reliably trace this
accretion event. We extend this framework by considering three N-body simulations of the Milky Way-GSE merger with different initial masses, mass ratios, and gas content. In addition to GCs belonging to the GSE disc progenitor, we accounted for GCs in its
halo and, in gas-rich models, a population of GCs formed during the Milky Way-GSE merger. We confirm that most GCs originating in the disc have lost a significant part of their orbital energy during repeated passages through the dense disc medium, and we
conjecture that associated
tidal shocks may have destroyed many of them. In contrast, GCs from the
halo and GCs formed during the merger have largely retained their orbital energy, which remains comparable to that of GSE
stars even up to 9 Gyr after the completion of the merger. By using a more realistic GC population and GSE modelling, we find that most GCs linked to GSE can be associated with Milky Way
accretion events in the $E$-$L_z$ plane, which supports previous observational associations based on a combination of energy-angular momentum and age-
metallicity relations.
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Cosmology and Nongalactic Astrophysics
The colour variability of low-z SNe Ia is entirely explained by dust
Marco Giunta, Konstantin Karchev and Roberto Trotta
The relative importance of intrinsic colour variability of
supernovae type Ia (SN Ia) versus
dust-induced reddening remains an open question with important ramifications for understanding their environmental dependence, as well as for the validity of the traditionally employed Tripp linear correction for cosmological inference. We revisit this question in the light of two low-
redshift, homogeneous
datasets, the ZTF DR2 and Foundation DR1, which we analyse within the framework of the
Bayesian hierarchical model Simple-BayeSN. We demonstrate both with simulation and on real data that traditional colour cuts, which remove highly reddened samples, induce a previously unrecognized selection effect, which may have biased previous conclusions on the origin of SN Ia colour variability. Once this is accounted for, we are able to explain the entirety of the colour–magnitude correlation as due to
dust effects, with no need for an intrinsic colour correlation. This result is robust with respect to a host
galaxy mass split and projected distance from the center of the host. Our findings imply that the traditional linear Tripp correction maintains an empirical validity, even though it should be ascribed to
dust rather than intrinsic colour variation.
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General Relativity and Quantum Cosmology
Measuring a Black Hole's Area Immediately after Merger: A Direct-Wave Test of Hawking's Area Law
Adrian Ka-Wai Chung, Kelvin Ka-Ho Lam, Anna Liu et al. (+1 more)
Black-hole area is the
geometric variable behind horizon thermodynamics. We introduce a gravitational-wave method to infer a Kerr-equivalent horizon area from direct waves in the near-merger signal, before quasinormal ringing dominates at late times. Applied to GW250114, and interpreting the fitted direct-wave frequency and damping rate as horizon quantities, we find that analyses initiated $3$–$4.5M$ before the peak-amplitude time yield an area consistent with the Kerr remnant. This result gives a first area measurement using direct waves and a new near-merger test of Hawking's area law.
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All authors Adrian Ka-Wai Chung, Kelvin Ka-Ho Lam, Anna Liu, Nicolas Yunes
Cosmology and Nongalactic Astrophysics
Impact of fiducial cosmology in model-agnostic cosmological inference with the BAO feature
Aseem Paranjape and Ravi K. Sheth
In recent work, we have developed a model-agnostic framework for cosmological inference using the
baryon acoustic oscillation (BAO) feature in
redshift space. The framework, which we dub the `Zel'dovich smearing approximation', involves several ingredients, including an optimal basis for the linear theory correlation function in real space, a Gaussian kernel that describes the smearing of the BAO feature due to bulk flows, and a model for the impact of scale dependent bias and mode coupling in
redshift space. Unlike traditional, template-based approaches, this framework does not assume any particular cosmological model. An important ingredient – which impacts both the traditional as well as model-agnostic frameworks – is the
geometric distortion introduced by the inevitable choice of the fiducial cosmology used for converting observed angles and
redshifts to comoving separations. In this work we show how this distortion, which was not yet included in our framework, affects the output of the Zel'dovich smearing approximation. We test our completed framework on two
halo samples derived from the AbacusSummit simulation suite and designed to mimic
galaxy samples from the ongoing DESI and Euclid surveys, respectively. We show that our framework produces unbiased cosmological constraints when applied to these semi-realistic samples and compare the organization of cosmological information in the model-agnostic and traditional approaches. We end with a roadmap to a detailed comparison of the performance of the traditional approach with the Zel'dovich smearing approximation, which is `data ready' as presented here.
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Astrophysics of Galaxies
The Combined Dense Gas and Excitation Atlas of the Milky Way I. Mass Distribution and Ripples in the Molecular Layer
Peter J Barnes
The first components of a new meta-survey, the Combined Dense Gas and Excitation Atlas (CODEX) of the Milky Way, are presented here with combined data from five previously published surveys: NANTEN+CHaMP, ThrUMMS, FUGIN, and MWISP. The CODEX is first used to harmonise the combination of parameters used to describe the
Galaxy's scale and rotation, including $R_0$ and $\Theta_0$ from recent work, since these are critical components of standard techniques for obtaining kinematic distances. An additional feature is added to these formulae to accommodate local clouds that are otherwise kinematically inconsistent with the Local Standard of Rest. The structure in the combined lV diagram spanning 230 deg of longitude is then analysed, yielding a new Ragged Spiral Arm model that better traces the deprojected (x,y) 12CO structure. The widespread existence of ripples in the molecular layer, first reported in the ThrUMMS data of the Fourth Quadrant (4Q), is confirmed in FUGIN data of the First Quadrant (1Q), averaging amplitudes $\sim$40 and $\sim$23 pc respectively, and wavelength $\sim$4 kpc in both. The (x,y) mass distributions as traced by the molecular line data and the published
dust extinction data match well across the 4Q+inner1Q, but poorly across the outer 1Q, probably due to lower sensitivity in the 1Q extinction data. In the 1Q+4Q, however, the two mean-z distributions do not match: the
dust ripple amplitude is $\sim$3x smaller than, and opposite in sign to, the gas ripples. This is nevertheless consistent since the
dust extinction is insensitive to the densest molecular gas.
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High Energy Physics (Theory)
Closing the loop on $\Phi^4$ in AdS$_3$
Dean Carmi, Riccardo Ciccone and Shimon Sukholuski
We compute the one-loop correction to the CFT data of all double-trace operators $[\phi\phi]_{n,\ell}$ for a $\Phi^4$ theory in AdS$_3$, for arbitrary values of $n$, $\ell$, and of the scaling dimension $\Delta_\phi>1$. Working in the spectral representation, the $t$-channel one-loop bubble diagram is reduced to a product of spectral integrals dressed by the conformal $6j$ symbol. Both the spectral integrals and the subsequent sums over residues are performed analytically, yielding finite closed-form expressions for the anomalous dimensions in terms of higher hypergeometric functions. We discuss the structure of the results, including their large-
spin and high-energy behaviors, and show that the anomalous dimensions are completely monotonic in
spin.
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Quantum Physics
Demystifying Objectivity with Operator Algebra Quantum Error Correction
Marin Girard, Gong Cheng and ChunJun Cao
Quantum Darwinism extends the decoherence formalism to explain how objectivity emerges from
quantum mechanics. However, existing approaches often capture only partial aspects of objectivity. By connecting
quantum Darwinism to operator
algebra quantum error correction, we show that the emergence of objectivity can be identified with the algebraic local recoverability of
quantum codes. Applying this algebraic framework to stabilizer codes, we show that it yields a far more precise characterization of classicality and redundancy, unifies the traditional measures of objectivity, enables efficient classification via coding-theoretic tools, and supports large-scale Clifford simulations of decoherence dynamics.
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High Energy Physics (Phenomenology)
A New Origin of the Big Bang from Dark-Sector-Induced Vacuum Decay and Its Gravitational-Wave Signal
Haipeng An and Tingyu Li
We propose a novel scenario for the onset of the thermal Big Bang. In this framework, the inflaton transfers its energy exclusively into a dark sector, leaving the Standard Model (SM) sector temporarily trapped in a false
vacuum. As the Hubble expansion rate rapidly decreases, the SM phase transition eventually completes, and the standard thermal Big Bang era commences upon the thermalization of the highly energetic bubble walls. We demonstrate that the large Lorentz boost of these bubble walls, combined with their Hubble-scale macroscopic size, generates distinctive gravitational-wave signatures from the SM
vacuum decay. This
stochastic gravitational-wave background provides a powerful new probe of the early Universe's expansion history, with a present-day energy density fraction that can reach $\Omega_{\text{GW}} \sim 3\times10^{-8}$.
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Astrophysics of Galaxies
A Population of Red Galaxies with Very Strong Emission Lines at $z > 5$ Revealed by the NIRCam Medium Bands: ”Classic” LRDs, Dusty Star-Forming Galaxies, and a Missing Population of LRDs
Sunna Withers, Adam Muzzin, Swara Ravindranath et al. (+16 more)
The NIRCam medium-bands have proven to be efficient at identifying Emission Line
Galaxies (ELGs) with high equivalent width (EW) H$\alpha$ and [OIII]+H$\beta$ emission lines. In this paper we exploit this efficiency to identify a sample of ELGs at $4.9 \lesssim z \lesssim 8.9$ using medium-band imaging from the CANUCS, Technicolor, and JUMPS surveys. We find that the ELGs exhibit a strong correlation between continuum color and emission line strength, such that
galaxies with bluer UV/optical continua have stronger H$\alpha$ and [OIII]+H$\beta$ emission lines. We identify 26
galaxies that are outliers from this relation, which we call the Red Emission line
Galaxies (REGs), because of their red continuum color and strong emission lines. We classify the REGs into three categories: 1) ”classic” Little Red Dots (LRDs) selected with common literature criteria, 2) extended REGs, resolved in F444W and consistent with being Dusty
Star Forming
Galaxies (DSFGs), and 3) compact REGs, unresolved in F444W but not classified as LRDs. The compact REGs fail common LRD selections for several reasons, including faint continuua, contamination from emission lines (very strong [OIII]+H$\beta$), and UV/optical colors that are flatter than those of LRDs. We conclude that the compact REGs are likely LRDs that ”classic” selection criteria miss, and are therefore missing from existing samples. Our results suggest that medium-band selection can provide more complete samples of these objects.
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All authors Sunna Withers, Adam Muzzin, Swara Ravindranath, Chris J. Willott, Nicholas S. Martis, Roberta Tripodi, Yoshihisa Asada, Maruša Bradač, Maya Merchant, Lamiya Mowla, Gaël Noirot, Ghassan T. E. Sarrouh, Marcin Sawicki, Jacqueline Antwi-Danso, Anishya Harshan, Naadiyah Jagga, Danilo Marchesini, Katherine Myers, Visal Sok
Strongly Correlated Electrons
Bootstrap bounds for Quantum Spin Systems using String Operators
Nisarg Chadha, Michael G. Scheer and Eslam Khalaf
Bootstrap is a numerical many-body method that provides rigorous bounds on ground-state observables by imposing a set of necessary constraints on the expectation values of operators. The quality of the resulting bounds is sensitive to the choice of operators entering the constraints. In particular, bounds on ground-state correlations are often loose in spontaneous
symmetry-breaking (SSB) phases, since local operator sets cannot exclude domain-wall excitations. In this work, we introduce non-local, string-like operators into the bootstrap and show that the program can be formulated directly in thermodynamic limit. We then apply our construction to several 1D
spin models. First, we obtain a significant tightening of the bounds in the SSB phase of the 1D transverse-field Ising model. Using the 1D axial next-nearest-neighbor Ising model, we further show that this tightening allows for a quantitative estimate of the locations of phase boundaries. Finally, we generalize the string operators to the 1D $\mathbb{Z}_3$
chiral clock model and track the behavior of the bounds across the phase diagram. Our results broaden the class of constraints available to the bootstrap and open a route toward bootstrapping more general
symmetry-broken and topological phases, where the relevant constraints may involve non-local or extended operators.
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Instrumentation and Methods for Astrophysics
The short and long of iPhoton science for a boosted Hubble
Stephan R. McCandliss, Jack Ford, Anne E. Jaskot et al. (+7 more)
Boosting the Hubble Space
Telescope (HST) will provide unique opportunities to carry out precursor science for the Habitable Worlds Observatory (HWO). Chief among them are science cases for determining the properties of
star forming
galaxies that contribute to creating and sustaining the universe in a mostly ionized state. The farUV and nearUV spectroscopic capabilities of the
Cosmic Origins Spectrograph (COS) and the Space
Telescope Imaging Spectrograph (STIS) are unique and unlikely to be replicated in the near future. Here we describe the benefits of a deep panchromatic spectroscopic effort to answer questions concerning the shape of the rest frame ionizing radiation escaping from
star forming
galaxies at modest
redshift, capture crucial missing spectral regions, and explore whether their
star formation histories are truly similar to the LyC leakers responsible for initiating and later sustaining the mostly-ionized-state of the universe. An observing program emphasizing multi-orbit observations, unencumbered by HST orbit competition and freely accessible to the wider ionizing
photon (iPhoton) community, will catalyze crowd-sourced answers to these questions and offer a lower operating cost price point.
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All authors Stephan R. McCandliss, Jack Ford, Anne E. Jaskot, Matthew J. Hayes, Alberto Saldana-Lopez, Alaina Henry, Timothy Heckman, Sophia R. Flury, Claudia Scarlata, Cody Carr
Quantum Physics
Fun with Graph States: Nonlocal Bell Pairs and the Arf Invariant
Bartlomiej Czech, Yichen Feng, Xianlai Wu et al. (+1 more)
We study inner products and partial amplitudes of graph states–a commonly employed class of
quantum states, which are specified by graphs. We find that the magnitudes of these quantities are simply related to the rank of the adjacency
matrix of the graph over F_2 while the phase is determined by the Arf invariant of its quadratic refinement. These facts motivate a nonlocal tensor factorization of the
Hilbert space, with respect to which all graph states are products of Bell pairs with unentangled ancillae. These results may illuminate the
quantum advantage in the framework of Measurement-Based
Quantum Computation and suggest that graph states can be usefully visualized in the
language of algebraic
topology. In addition, we develop a specialized technique for computing expectation values of
qubit-wise permutations in graph states, which is useful for calculating multi-invariants.
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All authors Bartlomiej Czech, Yichen Feng, Xianlai Wu, Minjun Xie
High Energy Physics (Theory)
Three Advanced Lectures on Inflation
Martin S. Sloth
Lecture notes on inflation. The lectures are three double lectures, held for the first time at the Nordita Winter School 2024 - Particle Physics and Cosmology, covering an advanced introduction to the theory of
primordial inflation, as well as the linear and non-linear perturbation theory of slow-roll inflation/quasi-de Sitter spacetimes.
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High Energy Physics (Phenomenology)
Neutrino mass ordering from the next Galactic supernova at DUNE, HK, and JUNO
Prantik Sarmah, Sovan Chakraborty, Abinash Medhi et al. (+2 more)
The next
Galactic core-collapse
supernova (CCSN) will offer a unique opportunity to determine the
neutrino mass ordering. We focus on two observables: the electron
neutrino ($\nu_e$) neutronization burst and the rise-time of the electron antineutrino ($\bar{\nu}_e$) flux during the
accretion phase. The neutronization burst, a sharp $\nu_e$ peak within $\sim 20$-$30$ ms, provides a clean and robust signature of mass ordering through its appearance or disappearance. During the
accretion phase, the faster rise of heavy
lepton flavor neutrinos ($\nu_x$) leads to a distinct faster rise-time behavior of the oscillated $\bar{\nu}_e$ signal, resulting in mass ordering discrimination. Using realistic CCSN simulations for multiple progenitor masses, we compute event rates and perform a statistical analysis for a
Galactic ($10$~kpc) CCSN event at DUNE, Hyper-Kamiokande (HK), and JUNO detectors. The neutronization burst remains largely independent of SN hydrodynamic simulation models, with DUNE and HK achieving $\gtrsim 6\sigma$ and $\gtrsim 4\sigma$ sensitivity for normal (NO) to inverted ordering (IO) discrimination, respectively. However, the rise-time observable is prone to progenitor degeneracies. To mitigate this cumulative and ratio-based observables constructed at characteristic timescales ($20$ ms & $100$ ms) are used. The resulting confidence levels from the rise-time analysis to discriminate IO/NO in HK and JUNO are $\sim 5\sigma$ and $\sim 3\sigma$, respectively. Our results highlight the complementarity of detectors and observables, and demonstrate that combining neutronization burst and
accretion phase information will be crucial for a definitive determination of the
neutrino mass ordering in the next
Galactic supernova.
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All authors Prantik Sarmah, Sovan Chakraborty, Abinash Medhi, Debanjan Bose, Moon Moon Devi
Mesoscale and Nanoscale Physics
Self-organized Floquet band geometry in cavity-driven quantum materials
Christopher Yang, Gil Refael, Mark S. Rudner et al. (+1 more)
Floquet engineering has emerged as a powerful route to dynamically control band structure and
topology in
quantum materials, but most implementations rely on externally imposed
laser fields that are power intensive, difficult to integrate into devices, and weakly coupled to the electronic system. We propose and analyze an alternative paradigm in which a self-generated cavity field Floquet-dresses the electronic bands and produces a
geometric Hall response in an electrically driven cavity material system. We consider a
semiconductor layer embedded in a cavity and coupled to external leads and a bath of acoustic
phonons, where dc pumping leads to the buildup of a coherent intracavity field through light-matter coupling. We determine the resulting nonequilibrium steady state self-consistently and show that, above threshold, the coupled system settles into a stable time-periodic limit cycle with a field amplitude set by the cavity quality factor and dissipation. This emergent periodic field Floquet-dresses the electronic bands and modifies the anomalous
Hall response of a material with broken time-reversal
symmetry. We demonstrate that the resulting
Hall conductivity can be directly probed via in-plane dc transport measurements. Our work establishes a route to self organized Floquet band reconstruction and
geometric transport without external
laser illumination, highlighting cavity driven steady states as a platform for electrically controlled nonequilibrium phases.
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All authors Christopher Yang, Gil Refael, Mark S. Rudner, Iliya Esin
High Energy Astrophysical Phenomena
A Disappearing Act: Constraints From "Missing" Flares of Repeating Partial TDE Candidates
Jason T. Hinkle, Chang Liu, Adam A. Miller et al. (+6 more)
Recurrent
tidal disruption events (rTDEs) are sources that exhibit multiple TDE-like
flares; many are likely powered by the recurring partial disruption of a bound
star, in a repeating partial TDE (rpTDE). Two such sources, TDE 2022dbl (ASASSN-22ci) and TDE 2020vdq (ZTF20acaazkt), each exhibited two UV/optical
flares and, under the assumption of periodicity, both were expected to exhibit a third
flare in early 2026. Neither exhibited such a
flare, to limits of $L_{\textrm{UV/optical}} \lesssim 10^{42}$ erg s$^{-1}$, $\sim$30$\times$ fainter than the previous
flares. Here, we examine several possible explanations. Observing two independent TDEs from the same
galaxy within $\sim$2 yr has a probability of $\lesssim$0.5% for measured average TDE rates and currently expected rate enhancements, unless there is extreme intrinsic dispersion in the rates. Theoretical predictions for a double TDE of both
stars in a binary are inconsistent with the observed
flares. We therefore conclude that TDE 2022dbl and TDE 2020vdq are rpTDEs. To produce only two observable
flares with similar energetics, our semi-analytical modeling strongly favors a main-sequence
star promptly placed on a bound orbit with a deep initial
tidal encounter at pericenter. These results suggest that the majority of rTDEs with multiple
flares over a few-year baseline are likely to be rpTDEs, and that a significant fraction of systems may produce only two observable
flares. This has important implications for the use of r(p)TDEs as probes of TDE physics and dynamical processes in the
nuclei of other
galaxies, in addition to the expected yield from upcoming surveys.
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All authors Jason T. Hinkle, Chang Liu, Adam A. Miller, Ping Chen, Katie Auchettl, Benjamin J. Shappee, Christopher S. Kochanek, K. Z. Stanek, Todd A. Thompson
Solar and Stellar Astrophysics
Nonthermal line broadening at solar flare footpoints is primarily field-aligned
Andy S. H. To and Alexander J. B. Russell
Magnetic reconnection powers
solar and
stellar flares, but a full understanding of how the released energy is transported and converted within the
solar atmosphere remains elusive. One clue lies at
solar-
flare footpoints, where spectral lines are far broader than the electron temperature alone can explain. Unresolved flows, waves,
turbulence and ion heating have all been proposed, but observations have not yet conclusively distinguished between these mechanisms. Here we perform an unprecedented
geometric test for
flare footpoints, using 4,593 Hinode/EIS spectra from 407 C- to M-class
flares. Line widths decrease systematically from disk centre to limb in all coronal emission lines, showing that the dominant broadening component is
magnetic field aligned rather than isotropic or transverse. Cooler lines retain substantial broadening into the early decay phase, consistent with persistent unresolved field-aligned flows or line-of-sight velocity gradients. Hotter lines show an impulsive component that decays rapidly after the soft X-ray peak, consistent with preferential ion heating and ion temperature anisotropy. These findings resolve the long-standing question of the nature of line broadening at
flare footpoints, place direct limits on
flare energetics, and motivate a new direction in
flare physics incorporating distinct field-aligned and perpendicular ion temperatures that exceed the electron temperature.
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Earth and Planetary Astrophysics · Cross-listed from cs.LG
Gaussian Process Latent Factor Regression for Low-Data, High-Dimensional Output Problems
Edward T. Stevenson, Eric T. Wolf, Mei Ting Mak et al. (+2 more)
In the sciences, regression tasks often require predicting high-dimensional outputs from few training examples. Multi-output Gaussian processes excel in low-data regimes but typically struggle with high-dimensional outputs. Compress-then-predict pipelines such as PCA-GP (principal component analysis plus Gaussian process regression) handle high dimensionality, but rely on bases optimized for reconstruction rather than prediction. To address this gap, we propose a model that represents each output as a linear-Gaussian decoding of a low-dimensional latent state drawn from a Gaussian process prior. By analytically marginalizing the decoder weights, we couple compression and prediction in a single objective that scales to high-dimensional outputs. We refer to this model as Gaussian process latent factor regression (GPLFR). We demonstrate GPLFR by building the first spatially resolved emulator of global
climate models for rocky
exoplanets.
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All authors Edward T. Stevenson, Eric T. Wolf, Mei Ting Mak, N. J. Mayne, Miles Cranmer
Astrophysics of Galaxies
The quasi-star model for Little Red Dots: potential and challenges
Fabrizio Gentile, Mauro Giavalisco, Emanuele Daddi et al. (+25 more)
(Abridged) Little Red Dots (LRDs) are a class of sources discovered by JWST observationally defined by a "V-shaped" rest-frame UV-Optical SED, a compact or unresolved morphology, and for having, frequently, broad hydrogen emission lines. Among various models, those involving a quasi-
star interpret LRDs as an intermediate stage in the
evolution of a super-massive black hole (SMBH) seed into a classic AGN. In this paper, we employ the radiative-transfer code Cloudy to study whether this model is able to reproduce the spectral features commonly observed in LRDs. The model consists of an accreting SMBH ($M_{\rm BH}\sim10^{5-6} \ M_\odot$) surrounded by a convective layer where a black-body (BB) spectrum with $T\sim5000 \ {\rm K}$ and $L\sim10^{44.4} \ {\rm erg \ s}^{-1}$ is produced. This BB is then reprocessed by a concentric thick ($\Delta R\sim1000 \ {\rm AU}$) shell of dense ($n_{\rm H}\sim10^{11} \ {\rm cm}^{-3}$) gas partially ionised by thermal collisions. The emerging radiation is further reprocessed by a diffuse clumpy medium surrounding the quasi-
star. We fit this model to JWST/NIRSpec spectra of LRDs from the literature, deriving the main physical parameters and the SMBH masses. Once coupled with the UV emission from a host
galaxy, this model is able to reproduce the shape of the UV-to-NIR continuum, including the presence of a Balmer break, as well as the luminosity of the hydrogen emission lines. However, this quasi-
star model does not natively account for the presence of broad helium lines and for the possible presence of hot
dust, needing additional components to match these observables. Our main result is to show how some LRDs can be modeled as quasi-
stars, highlighting that a significant degeneracy exists among different LRD models. This has important consequences for our understanding of the mechanisms driving black hole growth in the early Universe.
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All authors Fabrizio Gentile, Mauro Giavalisco, Emanuele Daddi, David Elbaz, Jean-Baptiste Billand, Maximilen Franco, Benjamin Magnelli, Guillermo Barro, Yingjie Cheng, Nikko J. Cleri, Kelcey Davis, Ivan Delvecchio, Mark Dickinson, Steven L. Finkelstein, Giovanni Gandolfi, Michaela Hirschmann, Weida Hu, Dale Kocevski, Anton M. Koekemoer, Ray Lucas, Sara Mascia, Lorenzo Napolitano, Casey Papovich, Borja Pérez-Díaz, Pablo Perez-Gonzalez, Jonathan R. Trump, Xin Wang, L. Y. Aaron Yung
Fluid Dynamics · Cross-listed from cs.LG
Multiscale POD of Transformer Attention Fields: Scale-Selective Analysis via Morlet Scalogram
Athanasios Zeris
We introduce scale-selective Proper Orthogonal Decomposition (POD) for
transformer attention fields, inspired by the use of POD for extracting energetically dominant modes from turbulent flow ensembles. The Morlet continuous wavelet transform identifies dominant temporal scales in the
attention lag structure across a document ensemble; POD then extracts the energetically dominant modes at each scale from the ensemble of
attention fields. The resulting modes reveal layer-dependent scale organisation, with early layers emphasising fine scales and later layers shifting toward coarser scales. We define a spectral concentration index from the POD
eigenvalue decay rate and show empirically that it differentiates layers by their
attention field complexity. By the classical POD optimality
theorem, the extracted modes minimise the average L2 reconstruction error over the ensemble (
Theorem 1), giving a data-driven effective rank for each layer. The method requires no architectural modification and no linguistic annotations: dominant
attention patterns emerge from ensemble statistics alone. The
turbulence analogy is structural rather than physical: we borrow ensemble covariance and modal analysis, not fluid dynamics itself.
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Materials Science
Element-Specific Solute Trapping and Grain Structure Evolution during Laser Powder Bed Fusion of Multicomponent Alloys
Xinxin Yao, James Hanagan, Md Shafiqur Rahman Jame et al. (+5 more)
Under the rapid solidification conditions of
laser powder bed fusion (LPBF), solute trapping manifests in an element-specific manner, altering nonequilibrium partitioning, constitutional undercooling, and grain selection behavior in multicomponent
alloys. Here, we elucidate the mechanisms by which element-specific solute trapping governs nucleation behavior and grain structure
evolution during LPBF demonstrated on a SS316L. This requires quantitative description of nonequilibrium multicomponent thermodynamics and grain
evolution across broad LPBF solidification conditions, which is achieved through a CALPHAD-informed Gaussian Process Regression (GPR)-assisted Phase-Field (PF) approach. The predicted transitions in grain morphology and grain size are validated against EBSD measurements under multiple LPBF processing conditions. Results demonstrate that increasing solidification rate drives a composition-dependent transition from solute
diffusion-controlled nucleation to solute trapping-controlled grain growth, where nonequilibrium solute redistribution intensified by solute trapping suppresses equiaxed grain formation despite high cooling rates. Quantitative decomposition of multicomponent undercooling further reveals distinct element-specific sensitivities to solute trapping, where C, Cr, and Mo remain dominant contributors to the overall undercooling, while the undercooling contribution of low-partitioning elements such as S and P are strongly suppressed relative to their
equilibrium values under rapid solidification conditions. These results reveal how element-specific solute trapping governs grain selection in multicomponent
alloys, providing a mechanistic basis for
alloy design under nonequilibrium solidification conditions.
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All authors Xinxin Yao, James Hanagan, Md Shafiqur Rahman Jame, Mallikharjun Marrey, Mohsen Taheri Andani, Raymundo Arróyave, Veera Sundararaghavan, Lei Chen