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Monday 5 October

High Energy Physics (Theory)

Generalised entanglement wedges in three dimensions

Generalized entanglement wedges (GWs), proposed by Bousso and Penington for gravitating regions in general spacetimes, share many properties of ordinary entanglement wedges, including nesting, monotonicity and strong subadditivity of their generalized entropies. In AdS/CFT, the corresponding properties of entanglement wedges are consequences of the structure of the dual CFT. In this paper we ask whether the properties of GWs have a similar origin. We explore this question in vacuum AdS$_3$ at leading order in $G$. We first show that every GW on a static slice is a union of geodesically convex regions. Each such region is an intersection of ordinary entanglement wedges, so every GW is built from unions and intersections of entanglement wedges. We then use the Crofton formula of integral geometry to write the perimeter of a convex region as the measure of the set of geodesics that intersect it. In AdS$_3$ every geodesic is the Ryu–Takayanagi surface of a boundary interval, so this measure can be written in terms of the von Neumann entropies of CFT intervals. Strong subadditivity of the CFT entropy guarantees that the measure is positive. Monotonicity and strong subadditivity of GWs then follow from simple inequalities between sets of geodesics. The strong subadditivity of GWs is therefore a direct consequence of strong subadditivity on the boundary. Our results further suggest that GWs correspond to subsystems of the CFT that are more general than boundary subregions.
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Mesoscale and Nanoscale Physics

Composite Fermion Theory of Fractional Chern Insulators in Rhombohedral Graphene

The experimental observation of the fractional quantum anomalous Hall effect in rhombohedral graphene multilayers has raised questions about the nature of the fractional Chern insulator (FCI) states and the role of the moiré potential. In this Letter we develop a composite fermion (CF) description and discuss how moiré modulation and Coulomb interactions stabilize the FCI ground states. Under a flux-attachment transformation and mean-field approximation, the CF spectrum forms Landau levels that are further split by the moiré potential. At moiré filling fractions in the Jain sequence, an integer number of CF bands are occupied, resulting in an incompressible ground state with fractionally quantized Hall response. Remarkably, when the attached flux opposes the Berry curvature of the conduction band of rhombohedral graphene, the CF Landau levels are widely spaced in energy and delocalized across layers, leading to a reduced density of states that helps protect the CF mean-field state and amplifying effects of the moiré potential acting on the layer away from the doped electrons. Interactions between CFs further enlarge the moiré-induced band gap and stabilize the FCI ground state. Our work sheds light on the nature of the FCI states in rhombohedral graphene and provides a new theoretical framework for further studies.
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Quantum Physics

Connectivity Controls Variational Accessibility in Symmetry-Preserving Quantum Circuits

Designing expressive quantum circuits for the variational quantum eigensolver (VQE) is a central challenge in simulating interacting many-body systems. Even symmetry-preserving (SP) circuits need not access the full many-body symmetry sector. We demonstrate this explicitly for the spin-$1/2$ XXZ and Hubbard models, where Hamiltonian-inspired nearest-neighbor (NN) SP circuits generate restricted dynamical Lie algebras (DLAs). While these restricted manifolds can accurately represent the ground state near the free-fermion limits, $J_z=0$ for XXZ and $U=0$ for Hubbard, interactions expose inaccessible many-body directions and severely limit VQE performance even at large circuit depth. Remarkably, a minimal modification of the generator connectivity can reconstruct the full orthogonal DLA within all relevant symmetry sectors studied in this work. For XXZ model, the addition of only one SP next-to-NN single-excitation connection triggers this dramatic reconstruction, whereas the Hubbard case requires a SP correlated double-excitation;–showing that the relevant connectivity can extend from the spatial lattice to many-body configuration space. This reconstruction enlarges the tangent space and accessibility of the energy-lowering Hamiltonian direction, leading to near-unit ground-state fidelity in VQE simulations. Our results establish a direct link between generator connectivity and variational accessibility and suggest a broader circuit-design principle: identify minimal symmetry-preserving generators that enlarge the accessible many-body space rather than increasing circuit depth alone. This perspective may have broader relevance for quantum many-body simulation at the interface of condensed-matter physics and quantum computing.
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Quantum Physics

Pauli Flat Quantum States Mimicking Maximal Magic

Quantum magic is a necessary resource for fault-tolerant quantum computing, capturing the departure of quantum states from the classically simulable stabiliser set. Motivated by its role in quantum information processing, we investigate the correlation structure of states that maximize the Rényi stabiliser entropies, focusing on the T-type and Hoggar states. Inspired by their distinctive properties, we explore the notion of Pauli flat states, defined as N-qubit states whose expectation values on all Pauli strings are equal in absolute value. These states reproduce the correlation structure of highly magical states, which could also be interpreted as a mixed variant of Pauli covariant N-qubit symmetric informationally complete (SIC) Weyl-Heisenberg fiducial states, while not necessarily possessing nontrivial quantum magic. We investigate their existence and possible constructions, including examples both inside and outside of the stabiliser polytope. To identify the latter, we examine a magic witness tailored to the introduced family of states. Finally, we discuss their entanglement and Bell nonlocality, providing a broader characterization of their quantum properties. For completeness, we find pure states with a relaxed condition on the Pauli expectations, which forces unequal elements to zero, and discuss their non-stabiliserness. Our results offer a new perspective on the relation between quantum magic and Pauli correlation structures. They hold relevance to geometrical approaches to quantum mechanics, entanglement and magic detection, as well as estimation tasks.
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High Energy Physics (Phenomenology)

Compositeness and decay properties of the flavor partner of $D^{*}_{s0}(2317)$

In view of the recent experimental finding of the heavy quark flavor partner of the $D_{s0}(2317)$ in the bottom sector, the $B_{s0}(5700)$, we perform the $B^{(*)}\bar{K}^{(*)}$ coupled-channel calculation in the hidden-gauge formalism. By fixing the mass of the bound state generated by the $B\bar{K}$ interaction with $J^P=0^+$ to the observed state, we also predict five new states with $J^P=\lbrace 0,1,2\rbrace^+$ in this sector. In particular, three of them have $J^P=1^+$ and masses $5740$, $6005$ and $6065$ MeV, respectively. In addition, we evaluate the decay width of the $B_{s0}$ and $B_{s1}$ states through the isospin breaking decay mode $B_s^0\pi^0$ and $B_s^{*0}\pi^0$, respectively. We find that, because these states have large binding energies with respect to the $B^{(*)}\bar{K}$ threshold, the coupling to the bare component can reduce this decay width by more than half of the decay width, from $50$ keV in the purely molecular model to $10-20$ keV, when the $B_{s0}$ is coupled to the bare component. We also observe that, after considering heavy-quark-spin violating contributions, the decay width for the $B_{s1}$ becomes smaller than for the $B_{s0}$.
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High Energy Physics (Theory)

Multi-Point Affine Bialgebras for AdS/CFT Integrability

In this work, we revisit the analytical structure of the classical affine Lie bialgebra underlying the integrable structures of AdS/CFT worldsheet scattering and the one-dimensional Hubbard model. Earlier work showed that the algebraic relations implied two singularity locations in the evaluation parameter plane besides the common expansion points infinity and zero for Laurent polynomials forming the basis for loop and affine algebras. Our aim is to formulate these singularities rigorously using meromorphic functions rather than by expansion into geometric series. We thus carefully analyse the analytical structure of the affine bialgebra relations in the complex plane paying attention to potential restrictions and extensions due to the additional singularities. As a first attempt with some shortcomings, we reformulate the affine bialgebra relations with the extra singularities serving as the expansion points for Laurent polynomials. We finally overcome the remaining issues by proposing three-point and four-point affine algebras for the rational and trigonometric cases. With a suitable choice of basis for meromorphic functions on the Riemann sphere with several punctures based on Krichever-Novikov algebras, we show that the multi-point affine algebras form consistent quasi-triangular Lie bialgebras.
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Mesoscale and Nanoscale Physics

Proposing one-sided tetrons as topological qubits for Majorana-based quantum computation

One-dimensional SM-SC hybrid nanowires with Rashba spin-orbit coupling and applied Zeeman field can support Majorana zero modes (MZMs) at the ends of the wire. In finite-length systems, residual wave-function overlap between the end modes produces an energy splitting. In a two-sided tetron qubit, composed of a pair of parallel Majorana wires coupled by a trivial SC backbone in the middle, this splitting limits the parity lifetime associated with Majorana pairs involving both wires and the coherence of the qubit, adversely affecting measurement-based braiding and readout operations. Here, we propose a one-sided tetron made of four parallel Majorana wires connected at a common end by an SC backbone. In the topological phase, the free wire ends host four MZMs that define the topological qubit, while the Majoranas localized near the opposite ends hybridize through the backbone and acquire finite energy. To study the basic hybridization mechanism, we consider a simpler two-wire subsystem, i.e., half of a one-sided tetron, which we call a doublon. In a doublon, the backbone, or bridge, strongly hybridizes the two Majorana modes at the connected end and shifts them away from zero energy, while the modes at the free ends form a near-zero energy fermion. We show that the splitting of the surviving MZM pair can fall by about two orders of magnitude compared to the splitting energies in a two-sided tetron, thereby dramatically increasing the parity lifetimes. Thus, the one-sided tetron ensures a suppression of the Majorana overlap comparable to doubling the length of the corresponding two-sided tetron.
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General Relativity and Quantum Cosmology

Propagation and horizon formation in Einstein–Gauss–Bonnet scalar collapse. I. Characteristic conditions, bounds and formation

We study scalar collapse in five- and six-dimensional Einstein–Gauss–Bonnet gravity with positive coupling, treated as an exact classical theory. On spherical scalar backgrounds, the characteristic conditions of the tensor, vector and scalar gravitational sectors reduce to inequalities in two local invariants: $K=1+\tilde\alpha F/R^2$, which compares the enclosed mass with the areal radius $R$, and a scalar-gradient invariant $j$. In five dimensions they imply $R_h^2>\tilde\alpha$ for the areal radius $R_h$ of a regular marginal sphere on the GR branch and the sharp bound $\tilde\alpha^2\mathcal R_{abcd}\mathcal R^{abcd}<28$ for nonnegative mass. For initially untrapped five-dimensional spherical data with a regular center, a bound on $K$ alone ensures smooth continuation on compact domains of dependence, so any first characteristic loss occurs on a smooth background, and a marginal sphere formed before any loss forces a later loss. Complete smooth data form marginal spheres at every allowed radius with mass arbitrarily close to its sharp lower bound; in six dimensions radius and mass can both be arbitrarily small. Without spherical symmetry, complete initial data with weak curvature contain, at sufficiently large scale, outermost strictly stable marginal surfaces with prescribed $S^3$ geometries satisfying a spectral condition; Berger surfaces among them have arbitrarily small area at fixed mass. Their formation from untrapped data is left open. Near a contracting homogeneous core, exact nonspherical developments of smooth constrained data converging with every derivative have bounded curvature but, after the core's characteristic loss, a fixed discrepancy in a geometric tidal record. Classical existence, local geometric uniqueness and continuity of this pointwise record cannot all be guaranteed on a common observation region. A companion paper treats narrow incoming pulses.
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High Energy Physics (Theory)

Non-invertible SPT phases from fusion rings via Tannaka duality

In a (1+1)-dimensional QFT with non-invertible symmetry, the fusion rules of topological lines are often the most accessible data, yet they do not fully determine whether the symmetry is anomaly-free, i.e. whether it admits trivially gapped phases. Such phases are characterized by fiber functors of the corresponding fusion category. Building on Tannaka duality, we extract fiber functors from the fusion ring alone by solving simultaneously for monoidal structure maps and tensor automorphisms. This allows us to find categorifications admitting a fiber functor without solving the pentagon equations directly. We test this procedure on the known Tambara–Yamagami ring of $\mathbb{Z}_2\times\mathbb{Z}_2$. Our main result concerns the rank-11 fusion ring shared by the representation categories of the two extraspecial groups of order 27, which has a multiplicity 3 channel and is relevant to self-triality. In both cases we find more than one fiber functor, i.e. several non-invertible SPT phases. We use the explicit data of these fiber functors to derive the $F$-symbols of the two representation categories in a compact form depending on a non-degenerate alternating bicharacter and an invertible object $\epsilon$. Using the reconstructed data, we compute the anomalous algebra on the interface between two different SPT phases.
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Astrophysics of Galaxies

DIGging into HII regions: the role of ionizing photon leakage and spectral hardening in coupling HII regions and diffuse ionized gas

The optical emission-line ratios of star-forming galaxies are broadly understood in the framework of photoionization, yet some systematic trends remain unexplained. Using 50–100 pc resolution PHANGS-MUSE observations of 19 nearby galaxies, we investigate how escaping ionizing radiation couples HII regions to the diffuse ionized gas (DIG), analyzing thousands of HII regions and DIG sightlines. HII regions and the DIG form a continuous sequence across standard line-ratio diagnostic diagrams (e.g., BPT diagrams), where progressively fainter regions show elevated high- and low-ionization line ratios, and the DIG extends the same trends into the composite–LINER regime. Line-ratio variations with global specific star formation rate (sSFR) suggest progressively harder ionizing radiation with increasing star formation activity, contrary to expectations for emission increasingly dominated by older stellar populations. Line-of-sight mixing explains part of the behavior but cannot reproduce all line-ratio trends. We therefore develop a model in which ionizing photons escape HII regions and propagate through the diffuse ISM, undergoing geometric dilution, attenuation, and spectral hardening. The model predicts that progressively fainter HII regions are increasingly ionized by leaked radiation from neighboring luminous regions, implying radiative coupling between HII regions. Joint modeling of HII regions and the DIG reproduces the HII region luminosity distribution and DIG surface brightness for escape fractions of $\sim$0.4$-$0.6 and ionizing-photon mean free paths of $\sim$0.5$-$1 kpc, and qualitatively reproduces the observed line-ratio sequences and their dependence on sSFR. Our results suggest that ionizing photon leakage may provide an important non-local feedback channel linking compact star-forming sites to large-scale galaxy disks.
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All authors Dalya Baron, Kathryn Kreckel, Gwen C. Rudie, Karin M. Sandstrom, Alberto D. Bolatto, Guillermo A. Blanc, Oleg V. Egorov, Eva Schinnerer, Ashley T. Barnes, Enrico Congiu, Daniel A. Dale, Simon C. O. Glover, Jaeyeon Kim, Ralf S. Klessen, José Eduardo Méndez-Delgado, Justus Neumann, Ismael Pessa, Thomas G. Williams

Earth and Planetary Astrophysics

Discovery of a second-generation planet candidate accreting onto a white dwarf

Many white dwarfs accrete the debris of disrupted planetary bodies, detected in the form of metal-enrichment in their atmospheres, dusty or gaseous circumstellar discs, and photometric transits from debris. The composition of accreted debris has been shown to be diverse yet overall closely resembles Solar System bodies. We report the discovery of a white dwarf accreting material that is unlike any Solar System object. The atmosphere of HS 0209+0832 is strongly enriched in trans-iron elements including zinc, copper, and niobium but depleted in the canonical rock-forming elements silicon and iron. The composition of the accreted object is consistent with a candidate second-generation planet, formed from the stellar material ejected during the giant phase. The key abundance signature which differentiates it from a first-generation planet is the high enrichment of s-process elements. Photospheric helium and the absence of terrestrial rock-forming elements implies the white dwarf is accreting from the escaped atmosphere of a photo-evaporating giant planet candidate. This is further supported by the detection of a sinusoidal photometric period of 4.399+/-0.026 days at an amplitude of 0.120+/-0.018 %, which we attribute to thermal emission phase variability from a planetary day-night cycle or a transiting cometary tail of an evaporating gas giant.
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All authors Jamie T. Williams, Boris T. Gänsicke, Nicholas C. Stone, Detlev Koester, Benjamin D. R. Davies, Christopher Tong, David J. Wilson, Snehalata Sahu, Andrew Swan, Thomas G. Beatty, Sergio H. Ramírez, Tim Cunningham, Knox S. Long

High Energy Astrophysical Phenomena

Power-Law Injection Spectrum from an Ensemble of Reconnecting Current Sheets

A collisionless, low-$\beta$ plasma undergoing strong sub-Alfvénic turbulence is expected to form a broad hierarchy of reconnecting current sheets immersed in a strong guide magnetic field. If the reconnecting field strength of a sheet scales with its length as a power law of index $\kappa$, and the number of sheets per unit interval of sheet length decreases as a power law of index $x$, the current-sheet ensemble injects nonthermal particles with a power-law energy spectrum $\propto \gamma^{-s}$, where $s = 1 + (x-2)/(1 + \kappa)$. The spectrum is hard ($s < 2$) when the longest sheets deliver most of the injected energy, which requires $x < 3 + \kappa$. Past numerical studies have measured $2 \lesssim x \lesssim 3.3$, and the scalings of intense current sheets support $\kappa \gtrsim 0$, resulting in $1 \lesssim s \lesssim 2.3$. This injection may yield flat or mildly steep radio spectra in optically thin sources and hard ion spectra in the coronae of active galactic nuclei.
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High Energy Physics (Phenomenology)

Magnus: neutrino oscillation probabilities for any Hermitian Hamiltonian, any number of flavors, and any matter profile

Interpreting neutrino oscillation measurements requires computing the probability that a neutrino born with one flavor is detected with another. In vacuum and in matter of constant density, this probability has exact formulas. Where the density varies along the path, as in the Earth, the Sun, or a supernova, it does not. There, the usual approaches either replace the profile by constant-density steps, whose error falls only as the square of their width, or integrate the evolution equation with a general-purpose solver, which must shorten its steps to meet a tighter tolerance. Both become slow at high accuracy, yet an analysis needs the probability at many energies, directions, and parameter values. Each new experiment or model often requires writing and validating a new solver. We present Magnus, an open-source Python code that avoids these limitations. It uses the Magnus expansion, whose error falls as a high power of its step width and whose cost is set by how fast the density varies, not by how many oscillations the path holds. Magnus accepts any density profile, any number of flavors, and any Hermitian Hamiltonian, such as those of non-standard interactions, sterile neutrinos, Lorentz-invariance violation, and pseudo-Dirac neutrinos. Where a cheaper route exists, it takes it automatically. For example, where the density varies slowly, as in the Sun, it follows the instantaneous eigenstates and applies the expansion only at resonances. Besides oscillating probabilities, Magnus returns phase-averaged ones, which describe solar and astrophysical neutrinos. A typical probability takes a few milliseconds, and batched scans are one to two orders of magnitude cheaper per point. Among the public codes we compared, Magnus is the fastest at high accuracy on a varying profile. Magnus shifts the effort of studying a new experiment or model from writing a solver to specifying its physics.
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Strongly Correlated Electrons

Local-moment magnets on all close-packed lattices are equivalent

The Heisenberg antiferromagnet on the fcc lattice is a canonical example of frustration. The fcc lattice is but one of an infinite number of close-packed structures, all of which have the same frustration-inducing local geometry. In this letter, we demonstrate a hidden symmetry that relates classical magnets on all close-packed lattices. This symmetry derives from a similar property in tight binding models that may explain the disordered low-temperature structures of lithium and sodium metals. In magnets, the symmetry holds when couplings are restricted to nearest ($J_1$) and next-nearest neighbours ($J_2$). It guarantees that all close-packed lattices are equivalent at the Luttinger-Tisza level. For any given values of $J_1$ and $J_2$, they have the same ground-state energy. Their ground state momenta are identical when projected onto the stacking plane. We construct a unified phase diagram as a function of $J_1$ and $J_2$ couplings for Heisenberg, XY and Ising magnets on any close-packed lattice. In each phase, the ground-state degeneracy is the same on all close-packed lattices, even after accounting for multi-Q spirals. This phase diagram can be easily adapted to any magnet composed of stacked triangular layers with similar couplings. Fluctuations above the classical ground state(s) are not related by any symmetry. This suggests that close-packed structures can show interesting differences in order-by-disorder selection.
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High Energy Physics (Theory)

Interacting multicomponent $SU(N)$ magnets

We study magnets composed of molecules with atoms interacting via $SU(N)$-invariant two-body interactions. Atoms carry states transforming in generically different irreducible representations of $SU(N)$, and the interaction strength between atoms depends on the specific atoms involved. We derive the thermodynamics of these magnets in the mean-field approach, and find that they can exhibit mixed ferro-antiferromagnetic behavior. We present a full analysis of the simplest nontrivial case of molecules consisting of two atoms in the spin-$j$ representation of $SU(2)$, which generalizes conventional magnetic systems, and derive its phase structure and transitions.
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Strongly Correlated Electrons

Chiral Parafermions in Floquet $\mathbb{Z}_N$ Topological Order

Floquet topological order (FTO) extends topology beyond equilibrium, giving rise to phenomena, such as the dynamical transmutation of anyons. Here, we realize $\mathbb{Z}_N$ FTO in a generalized Kitaev honeycomb model with clock degrees of freedom using a three-step periodic drive. The driven system admits an emergent description in terms of constrained parafermions coupled to conserved $\mathbb{Z}_N$ gauge fields. At the boundary, the drive generates chiral parafermionic Floquet edge modes. We resolve their propagation through correlation functions, characterize their fractional quantum-information transport through the radical chiral unitary index, and use their dynamics to probe exchange statistics. In the bulk, we explore the dynamical anyon transmutation with a non-equilibrium loop order parameter. At a Floquet sweet spot, where the drive becomes Clifford, these phenomena can be accessed using stabilizer simulations. Short-time matrix-product-state simulations away from this point show that the chiral edge response persists at accessible times. Our results establish $\mathbb{Z}_N$ Kitaev models as a setting for exploring intrinsically non-equilibrium topological phenomena on qudit-based quantum processors.
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All authors Melissa Will, Harald Schmid, Jan Egger, Adam Gammon-Smith, Michael Knap, Frank Pollmann

High Energy Physics (Phenomenology)

Coherent versus incoherent amplification: from parametric resonance to the kinetic regime in stimulated axion decay

Although the spontaneous decay of axions into two photons is extremely slow on cosmological timescales, it can be strongly enhanced in environments with large bosonic occupation numbers. From a classical field perspective, stimulated axion decay is described by modified Maxwell equations. For a coherent axion background, these equations exhibit a parametric resonance characterized by a photon growth exponent $s\propto g_{a\gamma}$. By contrast, a standard kinetic description, for instance based on Boltzmann equations, involves the squared matrix element of the decay process and therefore would naturally predict a characteristic rate scaling as $s\propto g_{a\gamma}^2$. In this work, we show that these apparently different behaviors originate from the coherence properties of the axion field. Starting from an axion field with a finite momentum dispersion, we show how dephasing among its momentum modes modifies the photon instability and derive an effective evolution equation in which this effect is encoded in a kernel. For a continuous Maxwell-Boltzmann distribution of axion velocities, we obtain an implicit expression for the photon growth exponent that reproduces the two asymptotic regimes and provides an approximate description of the crossover. When amplification develops on scales shorter than the axion coherence length, the parametric resonance scaling $s\propto g_{a\gamma}$ is recovered, whereas in the opposite limit an effectively kinetic behavior with $s\propto g_{a\gamma}^2$ emerges. Although the detailed form of the crossover depends on the axion momentum distribution, we expect the asymptotic scaling with $g_{a\gamma}$ to be largely insensitive to the specific distribution assumed.
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High Energy Physics (Theory)

The s-Rule from Geometry

String Theory provides powerful tools for constructing and studying five-dimensional Quantum Field Theories, notably through geometric engineering and five-brane webs. Understanding how these two descriptions are related in the presence of 7-branes requires incorporating the s-rule into the geometry. To address this question, we focus on basic three-legged five-brane webs ending on 7-branes. Building on the local M-theory description of five-branes ending on 7-branes, we consider triangular toric diagrams with a single non-primitive edge. We show that the corresponding local complex-structure deformation is well defined on the overlaps with the neighboring toric patches, while the corresponding gluing map remains well behaved as a function of the holomorphic coordinates throughout the neighboring patches precisely when the s-rule is satisfied. At saturation, the geometry is a T-cone and the 7-brane deformation becomes its Q-Gorenstein smoothing. Our results thus identify the s-rule with the obstruction to globalizing the local 7-brane deformation and provide a direct geometric link between T-cones and five-branes ending on 7-branes.
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High Energy Physics (Theory)

Localizing $\mathcal{N}=(2,0)$ $AdS_3$ solutions of M-theory

We apply equivariant localization to supersymmetric $AdS_3\times M_8$ solutions of eleven-dimensional supergravity, dual to two-dimensional $\mathcal N=(2,0)$ SCFTs. We construct equivariantly closed polyforms encoding the magnetic flux and its dual, calibrated M2-branes and the warped volume, reducing protected observables to fixed point data of the $U(1)$ R-symmetry action. We apply the framework to $S^4$ bundles over coassociative four-cycles and $S^2$ bundles over compact six-manifolds, obtaining topological formulae for leading central charges and gravitational anomalies in terms of quantized fluxes and topological data. We recover the known results for $T^2\times KE_4$ solutions and construct a compact numerical solution with quantized flux that lies outside the known polynomial branch.
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High Energy Astrophysical Phenomena

Uncovering the Physical Origins of Black Holes in the Milky Way for Astronomical Surveys

The observational landscape of stellar-mass black holes (BHs) in the Milky Way is expanding beyond X-ray binaries, with Gaia DR4 and Roman expected to open new windows onto BH populations. We use the binary population synthesis framework POSYDON to predict the present-day Galactic BH population and connect it to its evolutionary origins. We test the robustness of these predictions to uncertainties in binary evolution and BH formation, including core-collapse mechanisms, natal kicks, common-envelope efficiency, metallicity, and initial binary distributions. Across our models, we find that most Galactic BHs are isolated, with stellar mergers providing the largest contribution and binary disruptions the second largest. Among surviving binaries, detached BH-BH systems dominate. We identify a distinct, narrow feature at higher BH masses ($\simeq13\,\mathrm{M}_{\odot}$ in the fiducial model) produced by wind-driven evolution of massive Wolf-Rayet progenitors. This feature is particularly prominent among detached BH-BH binaries and persists across variations in binary-evolution and BH-formation physics, but depends strongly on metallicity. At lower masses, these BH-BH systems predominantly originate from progenitors that undergo stable mass transfer before BH formation. Finally, for more direct observational applications, we embed the synthetic populations in a Galactic model, evolve their kinematics, perform first-order microlensing calculations for BH-BH lenses, and examine BH systems with luminous companions in the context of the Gaia BHs. In the latter, we uncover a robust stable-mass-transfer population largely absent in rapid population-synthesis predictions. These results provide an evolutionary framework for interpreting the emerging Galactic BH population across complementary observational channels.
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All authors Ilia Kiato, Pierson Lipschultz, Vicky Kalogera, Jeff J. Andrews, Max M. Briel, Abhishek Chattaraj, Seth Gossage, Philipp M. Srivastava

Computational Physics

Constitutive-Set Mechanics: variational mechanics on an admissible set of constitutive laws

A structural simulation needs a constitutive law, and experiments rarely determine one uniquely: several laws may fit the same data and satisfy the same physical constraints, yet differ where the structure is loaded in ways the tests never were. Constitutive-Set Mechanics (CSM) keeps all of those laws. It replaces the single law in the variational formulation by the admissible set, and lets the mechanics itself decide which members of the set affect the structural prediction. The framework rests on one observation: a finite element assembly consults the law only at the strains the structure reaches, so the incremental energy depends on the law through a weighted record of those strains, the occupation measure of the state. The energy of a state under the set is a support function on that measure, and the equilibrium solve one performs anyway supplies the information needed to bound the worst case. Equilibrium states become certificates on the robust response, rigorous on the upper side for any mechanics solver and two-sided under global minimisation; the certificate has at most one more state than the number of constitutive directions the structure interrogates; a coherence theorem identifies when the pointwise-worst material is one no single material can be; and constitutive inference acts on the same support function. The method is demonstrated on linear elasticity, a data-constrained constitutive function, phase-field fracture, an assembled finite-strain composite shell, and a membrane characterised by one-mode tests alone. On the shell the structure interrogates four of 226 constitutive directions; on the membrane the certified worst-case energy exceeds the reference more than fourfold, and the experiment that most contracts the certified prediction is not the one where the constitutive uncertainty is largest.
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All authors Altaf Ahmad Lone, R. T. Durai Prabhakaran, Tawqeer Nasir Tak, Timon Rabczuk, Xiaoying Zhuang

High Energy Physics (Phenomenology)

Monopole Catalysis from Standard Model Anomalies

We study the generalized symmetries associated with Standard Model flavor and their fate in the presence of magnetic monopoles. This illuminates a striking phenomenological consequence: even when baryon and lepton number are classically conserved, the electroweak anomaly induces $\Delta B = \Delta L \in 3 \mathbb{Z}$ in monopole-fermion scattering for any monopole activating the anomaly. We demonstrate this mechanism in Pati-Salam theory and trinification.
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Earth and Planetary Astrophysics

Detecting multiple planets in Gaia data using Bayesian model selection

Gaia will soon provide a census of cold giant planets. However, an astrometric signal contains the superimposed reflex motion of all companions, so planetary signals cannot be treated individually. We therefore investigate Gaia's planet-detection capabilities for 1-planet and 2-planet systems, with special attention to systems near 2:1 mean-motion resonance. Gaia can detect 2-planet systems, although the lower-S/N planet requires a higher S/N threshold, especially when the outer planet is more massive and near 2:1 commensurability. When fitting a 1-planet model to a circular 2-planet resonant system, the resulting fit shows biases in eccentricity (up to e = 0.8), mass (up to 100%), and inclination (up to 50 deg). The bias is maximised when the planets' astrometric signatures are similar, since the combined orbital signal deviates most from a single Keplerian orbit. Many of these systems can be identified as having 2 planets using Bayesian model selection. Still, in some cases the second planet is hidden and undetectable due to its S/N, leading to these biases for the outer planet's orbital parameters. When the outer planet is roughly over three times as massive as the inner planet, orbital approximations allow us to recover the astrometric resoeccentric degeneracy from the bias. When the planets are in dynamical resonance, apsidal precession observed over a long enough baseline (e.g. DR5) can contribute to breaking the degeneracy at short orbital periods. Overall, these biases might significantly affect constraints on planet formation, migration, and evolution models from Gaia population-wide demographics.
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Solar and Stellar Astrophysics

Unlocking new information in stellar circular polarisation with second-order least-squares deconvolution

Least-squares deconvolution (LSD) is the standard technique for measuring stellar magnetic fields from circular polarisation spectra. It rests on the weak-field approximation and yields the longitudinal field alone. We aim to extend LSD beyond the weak-field limit and interpret departures from a linear field response in terms of the field modulus. The Stokes V absorption coefficient is expanded in odd wavelength derivatives of the intensity profile, with coefficients given by the Zeeman pattern moments. Truncation after two terms gives every line a second weight, formed from the third moment of its splitting pattern, and two mean Stokes V profiles follow from multiprofile LSD. This description was tested with polarised spectrum synthesis and applied to archival spectra of two Ap stars and two active M dwarfs. The second mean profile is proportional to the second derivative of the first, with a coefficient measuring the mean square field modulus weighted by the longitudinal flux. This observable separates field strength from the area it covers. Simulations at realistic signal-to-noise ratios show that the second component is reliably detected from about 500 G and constrains the field modulus up to several kG. Applying this methodology to the Ap stars, we found the modulus consistent with their known field strengths, whereas for the M dwarfs it was close to the Zeeman-broadening measurements and far above the large-scale fields from Zeeman-Doppler imaging. Second-order LSD turns the breakdown of the weak-field approximation from a source of error into a new magnetic observable, revealing for the first time the field strength in the regions emitting circular polarisation. It applies to any star with a detectable Stokes V signature and bridges the gap between polarimetry and Zeeman broadening, most promisingly for cool active stars in the infrared.
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High Energy Physics (Theory)

Deriving the $\text{AdS}_3\times\text{S}^3\times \text{T}^4$ Quantum Spectral Curve II: T-system and QSC

We complete the systematic derivation of the Quantum Spectral Curve (QSC) for strings on $\text{AdS}_3\times\text{S}^3\times \text{T}^4$ with pure Ramond–Ramond (RR) flux, building on the extended Y-system obtained in our preceding paper. We establish the precise relation between the two formalisms of the Thermodynamic Bethe Ansatz and the QSC, derive the previously conjectured QSC, and, along the way, uncover additional relations satisfied by its solutions. Our analysis also clarifies how massless excitations, although not explicit among the basic QSC building blocks, are encoded in their analytic structure. The derivation culminates in the so-called $\mathbf{P}{\mu}$-system, a compact formulation of the QSC in terms of a small set of functions and their analytic continuations.
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All authors Andrea Cavaglià, Davide Polvara, Nicolò Primi, Alessandro Sfondrini, Roberto Tateo

Strongly Correlated Electrons

Heavy-fermion hybridization waves from Dirac spinons near a Kondo-breakdown quantum phase transition

Motivated by the recent observation of spatially modulated screening in different paramagnetic heavy-fermion materials, we propose a theoretical mechanism for the emergence of such hybridization waves in frustrated Kondo lattices with no magnetic order. By applying a parton mean-field theory and a perturbative calculation to a minimal Kondo-Heisenberg lattice model, we demonstrate that a heavy Fermi liquid can naturally develop hybridization waves when it approaches a quantum phase transition where Kondo screening breaks down and the local magnetic moments form a Dirac spin liquid. We relate the strength of this mechanism to a kinematic condition on the electronic and spinon band structures and show that the spatial periodicity of the hybridization wave is set by a momentum $\vec{Q}$ connecting the nodes in the dispersion of the Dirac spinons to low-energy portions of the electronic band structure.
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High Energy Physics (Theory)

The Back-to-Back Plateau of the Energy-Energy Correlator from Weak to Strong Coupling

The back-to-back limit of the energy-energy correlator (EEC) exhibits a finite plateau, capturing the evolution from perturbative soft-collinear radiation at weak coupling to string dynamics at strong coupling. At weak coupling, we resum its leading and next-to-leading-power logarithms through N$^3$LL in $\mathcal N=4$ SYM, including non-planar contributions. Combining this weak-coupling endpoint with bootstrap and strong-coupling data, we construct an interpolation for the plateau height from weak to strong coupling. The calculation uses a human-in-the-loop agentic workflow.
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All authors Hao Chen, Ian Moult, Bo Wang, Hua Xing Zhu

Quantum Physics

Decoupling Spectral Gaps from Entanglement Complexity in Quantum Annealing

Exponentially small spectral gaps are the central obstacle to adiabatic quantum annealing, yet whether such bottlenecks demand correspondingly complex entanglement remains unclear. We show that gap scaling and entanglement complexity need not be linked. Conventional first-order transitions combine exponentially small gaps with bounded $O(1)$ bipartite Schmidt rank, even though the critical states retain global multipartite correlations, while continuous transitions combine polynomially closing gaps with logarithmically growing entanglement. We show that each pairing can also be inverted: in a known first-order transition in a staggered-field antiferromagnetic Ising chain the gap closes polynomially despite bounded Schmidt rank, while we construct a mirror-twin manifold model whose gap closes exponentially even as its entanglement entropy grows logarithmically with system size. We derive bounds connecting Schmidt rank to Hamming-space geometry, and identify manifold density and connectivity as the ingredients that determine which combination occurs. These results show that entanglement complexity alone cannot characterize annealing difficulty, and point toward a broader search for quantum resources that capture the geometry of state evolution in Hilbert space.
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Quantum Physics

Kardar-Parisi-Zhang superdiffusion in chaotic quantum circuits

We construct a family of chaotic brickwork quantum circuits exhibiting superdiffusive transport with dynamical exponent $z=3/2$ in the full Kardar–Parisi–Zhang (KPZ) universality class. This is enabled by the equilibrium current associated with a inhomogeneous conserved density having a nontrivial dependence on the chemical potential. Using nonlinear fluctuating hydrodynamics, we derive the propagation velocity, broadening scale, and universal scaling form of the charge correlation function from microscopic equilibrium properties. Tensor-network simulations of a two-site spin-$1$ (qutrit) circuit reproduce these parameter-free predictions, including the full stationary KPZ profile. We further construct a three-site spin-$\frac12$ (qubit) circuit, where transport varies from diffusive to superdiffusive with the chemical potential, while long-lived coherent quasiparticles delay the convergence of the profile to the KPZ scaling form. Our results establish that KPZ superdiffusion in quantum systems is not restricted to fine-tuned integrable models.
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All authors Rustem Sharipov, Urban Duh, Sun Woo P. Kim, Friedrich Hübner

General Relativity and Quantum Cosmology

The quasinormal modes of Kerr-Newman black holes: a separated approach

We compute Kerr-Newman quasinormal modes using a recently found exact separation of the gravitoelectric perturbation equations. For each spin-label $\varsigma=\pm1$, a matrix angular ordinary differential equation and a scalar second-order radial ordinary differential equation define a joint spectral problem for the complex frequency $\omega$ and separation constant $\lambda$. We solve this problem by imposing regularity at the angular poles, ingoing behavior at the event horizon, and outgoing behavior at infinity. We benchmark the numerical code built to solve the separated equations, and the resulting frequencies, against recently published spectral calculations of the coupled system. Comparisons with those results yield absolute differences of order $10^{-10}$ to $10^{-5}$, depending on the BH parameters and overtone number. We also find numerical hints of spin-label isospectrality in both the electromagnetic-led and gravitational-led sectors of fundamental quasinormal modes, even at near-extremal Kerr-Newman configurations. These results provide numerical evidence that the separated equations reproduce Kerr-Newman quasinormal frequencies and offer a practical route to exploring the ringdown of rotating, charged black holes.
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