Strongly Correlated Electrons
Thermally melted quadrupolar order and intrinsically quantum phases in 5$d^1$ double perovskites
Rong Cong, Ginevra Corsale, Ilija K. Nikolov et al. (+3 more)
Spin-orbit-coupled $d^1$ double perovskites exhibit a rich interplay of
spin, orbital, and quadrupolar degrees of freedom (DOF), giving rise to competing
magnetic and multipolar phases. Although
quantum mean-field theories predict many exotic phases, their stability against thermal fluctuations and reproducibility within a classical framework remain an open question. Here, we surpass the mean-field limitations by deploying large-scale classical Monte Carlo simulations on the projected $j=3/2$
manifold of the FCC
lattice, allowing complex ordering patterns to emerge spontaneously without preassigned
magnetic symmetries. Our thermodynamic mapping reveals that thermal fluctuations melt the intermediate-temperature quadrupolar phase over part of the phase diagram, while it survives intact elsewhere. Crucially, by systematically isolating the boundary between classical and
quantum stability, we demonstrate that while the four-sublattice
antiferromagnetic and
ferromagnetic (FM) phases are robustly classical, the coplanar canted FM[110] state completely destabilizes. This identifies the FM[110] phase as an intrinsically
quantum state born out of
quantum fluctuations. Our results demonstrate that the dominant
magnetic phases are robust within a classical description, where the essential physics of the system is captured by weakly entangled, short-range correlated DOF and highlight the role of thermal fluctuations in determining the stability of different types of
magnetic and quadrupolar order.
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All authors Rong Cong, Ginevra Corsale, Ilija K. Nikolov, Wenjuan Zhang, Nandini Trivedi, Vesna F. Mitrović
General Relativity and Quantum Cosmology
Black Hole Perturbation Toolkit: Low frequency and post-Newtonian expansions
Jakob Neef, Chris Kavanagh and Adrian Ottewill
The Teukolsky and SpinWeightedSpheroidalHarmonics packages of the black hole perturbation toolkit (BHPT) are one of the main public libraries to compute numerical solutions to the Teukolsky equation and related quantities. This work is a companion paper presenting their new and improved weak-field analytic functionality focusing on post-Newtonian expansions. The Teukolsky package now allows users to independently extract multiple useful quantities, such as the so called MST coefficients, renormalized angular momentum, amplitudes of the radial functions or the phase shift as a low frequency/PM expansion. It also provides PN expansions of the homogeneous radial functions or - for circular orbits in Kerr - inhomogeneous amplitudes, as well as energy and angular momentum fluxes at infinity and the horizon. All quantities can be computed to state of the art precision on regular laptops. It also provides a suite of tools for post-Newtonian self force computations and updates the analytic functionality of the SpinWeightedSpheroidalHarmonics package. Computations are possible both for specific and generic
spin weight $s$ and harmonic mode numbers $\ell$ and $m$. This package paves the way for intensive high-order post-Newtonian self-force calculations at the forefront of waveform modelling of small mass ratio black hole binaries, as well as giving widely useful low-frequency expansions for black hole perturbation theory. All functions described in this paper are available in BHPT versions Teukolsky v.1.2 and SpinWeightedSpheroidalHarmonics v.1.1.
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Earth and Planetary Astrophysics
Inside the Eirenesphere: The Interplay of Porosity, Heat Flux and Mineralogy in Exoplanetary Aquable and Habitable Layers
Santiago A. Orjuela and Jorge I. Zuluaga
The classical circumstellar habitable zone restricts the search for life to planetary surfaces where
stellar irradiation sustains
liquid water, overlooking vast subsurface environments. Here, we present a geophysical model integrating internal radial structure, mineralogy, radiogenic heat, and pressure-dependent porosity to quantify the three-dimensional habitable volume-the eirenesphere-of rocky
exoplanets. We distinguish between aquability (thermodynamic water stability) and habitability, which requires temperatures and pressures within extremophile biological limits, plus sufficient porosity for fluid circulation. To compare planetary capacities, we introduce the Eirenesphere Volumetric Index (EVI), measuring average subsurface biosphere volume. Applying this framework, we find that Earth's current state (EVI$\approx 0.06$ terrestrial oceans) represents only a moderate regime. Instead, mature super-Earths with high geothermal activity provide the most extensive environments for deep biospheres. Crustal mineralogy exerts a first-order control: thermally insulating felsic crusts sustain significantly larger eirenespheres than primary mafic lithologies. Tracking secular cooling reveals internal habitability is an evolutionary property; young
planets host confined biospheres due to steep thermal gradients, whereas mature worlds maximize habitable volumes over billions of years. Finally, we demonstrate that around
solar-like
stars, subsurface habitability persists out to $5-7$ au, effectively decoupling life's potential from surface radiative balance. Extrapolating to the Milky Way reveals a staggering
galactic capacity for subsurface life, on the order of billions of terrestrial oceans. Ultimately, this framework shifts the astrobiological paradigm from a surface-dependent phenomenon to an intrinsic planetary property, offering a metric to prioritize targets.
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Superconductivity
Weyl Chirality and Kitaev Topology through Bargmann Invariants
Swarup Sangiri and A. Taraphder
We apply a finite-state
geometric formulation based on Bargmann invariants to a two-band Weyl
Hamiltonian and the one-dimensional Kitaev model of a p-wave
superconductor. For the Weyl system, a
symmetry-antisymmetrized third-order Bargmann combination selects the chirality-sensitive component of the local pseudospin geometry and extends to a two-band
lattice Weyl model. For the Kitaev chain, a normalized ratio involving a third-order Bargmann invariant and a second-order overlap factor removes the dependence on an intermediate state and reproduces the $Z_2$ distinction between its two gapped phases. We further construct a fourth-order loop connecting localized Majorana edge-mode profiles with finite-energy BdG states and an alternating fourth-order loop involving opposite Weyl pseudospin sectors. These constructions illustrate how suitable Bargmann combinations can probe chirality-sensitive, topological, and higher-order
geometric information directly through
quantum-state overlaps, providing an alternative state-based route without requiring a continuous description of the underlying state-space geometry.
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General Relativity and Quantum Cosmology
Circular acceleration in Minkowski spacetime: thermality versus finite size
Cameron R D Bunney and Jorma Louko
The Unruh effect predicts that a uniformly linearly accelerated observer with proper acceleration $a$ reacts to the Minkowski
vacuum through excitations and de-excitations with the characteristics of a thermal state at temperature $T_U=a/(2\pi)$. An observer in uniform circular motion will experience similar excitations and de-excitations that we may use to operationally define an effective temperature, which however depends not only on the acceleration but also on the orbital speed and excitation energy. Motivated by the experimental interest in the circular motion Unruh effect, we investigate how spatial confinement modifies the response of an Unruh-DeWitt detector in $2+1$ Minkowski spacetime. We consider a massless scalar field confined within a circular boundary prepared in either the
vacuum or a thermal state, probed by an Unruh-DeWitt detector on a circular orbit, a setting that describes proposed analogue spacetime systems for testing the effect, and in which both a boundary and an ambient temperature will necessarily be present. We establish analytic results for the detector response in the large-boundary regime and identify resonance peaks, which are more prominent when the field has an ambient temperature.
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Mesoscale and Nanoscale Physics
Finite-state automata for exact matrix product operators of tight-binding Hamiltonians: fractals, quasicrystals, trees and hyperbolic lattices
Marta Brzezińska, Jeanne Colbois and Loïc Herviou
Inspired by the recent progress in the simulation of tight-binding
Hamiltonians on large
lattices using tensor networks, we introduce a systematic
matrix product operator (MPO) construction for single-particle
Hamiltonians on recursively structured
lattices. Taking advantage of this recursive structure, we encode the
lattice geometry in a finite-state automaton and, adapting ideas from Abelian-symmetric tensor networks, obtain an exact and analytical MPO representation of the
Hamiltonian, where the number of tensors grows logarithmically with the system size and the bond dimension is set by the number of automaton states. Several examples demonstrate the generality of the framework: regular
lattices, fractals, Cayley trees,
hyperbolic lattices, and one- and two-dimensional Fibonacci quasicrystals. Combined with the kernel
polynomial method, these MPO representations enable large-scale calculations of spectral properties without explicitly constructing the full
Hamiltonian. This provides a unified route to the exploration of electronic properties across a broad class of
lattices at exponentially large system sizes.
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Mathematical Physics
Eigenvectors and Eigenvalues of $p$-Curvature Operators for KZ–type Differential Connections
Vitaly Tarasov and Alexander Varchenko
A KZ-type connection in characteristic $p$ has $p$-
curvature operators. These operators are commuting endomorphisms of the connection. We present a Bethe-ansatz-type construction of their eigenvectors and
eigenvalues. The eigenvector is constructed as the value of a characteristic $p$ hypergeometric integral and extends to a flat eigensection over the Frobenius neighborhood of the corresponding Bethe point.
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Soft Condensed Matter
Universal behavior in diffuse charge dynamics with patterned electrodes
E. Krucker-Velasquez, E. Kirkinis and M. Olvera de la Cruz
Iontronic devices that replicate physiological processes will improve energy efficiency to support artificial-intelligence architectures. Energy storage and conversion devices, however, display disordered interfacial and bulk configurations that conventional impedance spectroscopy cannot resolve. Here, we show that the onset of frequency dispersion in the impedance of an electrolytic
cell with non-uniformly charged electrodes takes place at approximately twice the resonator natural frequency, independently of whether the
cell is driven by oscillating charges or voltage differences, and remains valid for both overlapping and non-overlapping double layers. In addition to characterizing energy storage devices, these universal findings apply to devices interfaced with biomaterials.
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Statistical Mechanics
Order-parameter-dependent mobility in the convective-viscous Cahn-Hilliard equation
P. O. Mchedlov-Petrosyan, L. N. Davydov and O. A. Osmayev
Generally the mobility in the Cahn-Hilliard equation may depend on the order parameter; this was evident already from the original derivation. However, explicit introduction of such dependence results in tremendous calculation difficulties, so the constant mobility approximation was commonly used. On the other hand, in several cases this dependence appeared to be crucial, so more realistic expressions were applied, usually positive powers or
polynomials; still, for such dependencies only approximate and/or numerical solution exist. We consider 'reciprocal' linear and quadratic dependencies of mobility on the order parameter; for these dependencies exact traveling wave solutions are obtained. Even more, in a limited interval of the parameters reciprocal quadratic mobilities are rather good approximations to
polynomial mobilities.
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Quantum Physics
A Quantum Phase-based Comparator
Alessandro Berti and Alessandro Poggiali
Quantum comparators decide the order of two operands. They rely on reversible logic acting on basis-encoded integers, so their width grows with the precision. We introduce the
Quantum Phase-based Comparator (QPC), which compares two values carried in relative phases instead. The
circuit places the two phases, entered with opposite signs, between a pair of Hadamard gates, and a fixed offset centers the interference, so that the probability of measuring zero falls below one half exactly when the first phase is the smaller. We give two implementations. With hard-coded values, the two values are written into the parameters of two phase gates, and the comparison costs one
qubit and five gates. With the register-driven cascade, the values are drawn from two $t$-
qubit registers through binary-weighted controlled-phase gates, at a cost of one
qubit beyond the registers and depth linear in $t$; since the cascade induces each phase linearly from the register content, one
circuit handles a superposition of operand pairs. The readout yields a biased coin rather than a definite bit, and we quantify the shots that a decision takes at a given phase separation. Scaling both phases by an integer widens the decision margin at no cost in width or depth, and an adaptive doubling schedule turns this amplification into a shot count logarithmic in the inverse separation.
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High Energy Astrophysical Phenomena
A Magnetic Unification of Merging Supermassive Black Hole Binaries
Mark J. Avara, David O'Neill and Zoltán Haiman
The detection of an electromagnetic (EM) transient from a supermassive black hole binary (SMBHB) merging within a gaseous environment will constitute a multi-messenger milestone. Numerical simulations of these systems have mostly been performed in 2D with a constant viscosity parameter representing turbulent and
magnetic stresses. These simulations predict a steep drop in
accretion rate and X-ray luminosity at merger, followed by a slow recovery. However, 3D-GRMHD and 3D-MHD simulations have shown only a modest reduction in
accretion rate and a fast post-merger recovery. We present a new 2D pseudo-Newtonian framework with physically motivated prescriptions for
stochastic viscosity, relativistic apsidal precession, and large-scale
magnetic fields. When suitably calibrated, this 2D framework accurately captures key 3D-GRMHD behavior, demonstrating that it can be used to explore binary
accretion without the high computational cost of 3D-GRMHD simulations. We find that the merger signatures are most sensitive to the strength of the
magnetic field, with a drop in the
accretion rate at merger progressively less pronounced for stronger fields. Post-merger
evolution is determined by both magnetization and relativistic precession of orbiting gas, yielding rapid recovery of
accretion. For low-magnetization disks, recovery is driven by self-intersection shocks, and the dip at merger is followed by a distinct second dimming. Large-scale
magnetic fields of increasing magnitude lead to magnetically arrested disk (MAD) behavior which disturbs the merging system progressively earlier before merger, and longer after. Our results unify the EM signatures of the merger of embedded coplanar SMBHBs, and provide novel observational constraints on their intrinsic magnetization.
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Astrophysics of Galaxies
Giant Low-Surface Brightness Galaxies in the Global Picture of Galaxy Formation and Evolution
Fedor M. Kolganov, Igor V. Chilingarian, Anna S. Saburova et al. (+5 more)
Giant low-surface brightness
galaxies (gLSBGs) challenge standard merger-driven
galaxy assembly models due to their large, dynamically cold disks, with radii often larger than 100~kpc and dynamical masses exceeding ${\sim}10^{12}$~\Ms. We identify $60$ gLSBGs, including a volume-complete subsample of $35$
galaxies out to $z=0.1$ in the 120~sq.deg. area. Using new and archival photometric and spectroscopic data, we homogeneously analyze their structural properties and derive central velocity dispersions. We update the gLSBG volume density estimate in the local Universe to $(3.6 \pm 0.6) \cdot 10^{-5}~\text{Mpc}^{-3}$. This number corresponds to about 1 in 4000
galaxies in the $g$-band luminosity range $0.14-1.37 \cdot 10^{11}~L_{\odot}$ out to $z=0.1$, which is consistent with EAGLE cosmological simulations but 3.8 times lower than the corresponding value in TNG100. Central surface brightness and scalelength of the gLSB disks scale with the luminosity of the central component, becoming fainter and flatter as the central component grows more luminous, suggesting rapid disk formation rather than the inside-out growth typical of high surface brightness late-type
galaxies. Many gLSBGs also show extended UV counterparts in GALEX, strengthening their connection to XUV-disk
galaxies. Finally, comparison with superluminous spirals shows that even complete gas-to-
star conversion cannot transform a typical gLSBG into a superspiral, owing to their lower total baryonic mass.
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All authors Fedor M. Kolganov, Igor V. Chilingarian, Anna S. Saburova, Damir Gasymov, Evgenii V. Rubtsov, Vladislav I. Klochkov, Kirill A. Grishin, Mariia Demianenko
General Relativity and Quantum Cosmology
Kerr-Degenerate Shadows and Distinct Strong-Deflection Lensing in Rotating Hayward-like and Bardeen-like Geometries
Chen-Hung Hsiao, Limei Yuan and Yidun Wan
We study and compare rotating Hayward-like and Bardeen-like geometries within a common Kerr-like axisymmetric ansatz, with the models distinguished by their areal-radius functions $R_i(\rho)$. On the adopted radial branches, the positive minimum areal radius excludes the Kerr ring locus, and the
curvature invariants examined here remain finite. We identify the parameter domains containing two, one, or no horizons. The two geometries have the same asymptotic Komar charges but different finite-radius values. If we treat the Einstein tensor as an effective stress tensor, then for every nonzero regularity length $\ell$, this ansatz violates the null and weak energy conditions, as demonstrated by the equatorial radial-null contraction. For the complete
photon family on a black-hole branch, the shadow boundary is identical to that of Kerr at the same mass,
spin, and observer inclination, and is also identical for the two regular geometries. The corresponding area-equivalent shadow diameters for M87* and Sgr~A* are consistent with the approximate Event Horizon
Telescope (EHT)-based intervals adopted here, and we do not obtain further constraints on $\ell$. By contrast, the prograde equatorial strong-deflection limit (SDL) calculations are only partly degenerate. At fixed
spin, $u_m^+$ and $\theta_\infty^+$ are common to Kerr and the two regular geometries, whereas $\bar a_+$, $\bar b_+$, the image separation, the relative magnitude, and the subleading time-delay correction depend on $\ell$ and on the areal-radius profile. Within the stated strong-deflection approximation, future measurements of $\Delta T_{2,1}$, $s^+$, and $r_{\rm mag}^+$ may help test these rotating geometries and distinguish the Hayward-like and Bardeen-like predictions from Kerr, including in the one-horizon parameter domain where the adopted branch contains no Kerr-like inner horizon.
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High Energy Physics (Theory)
Primary Decompositions in Lorentz-Covariant Rings
Giuseppe De Laurentis and David Tai
An effective strategy for constructing compact representations of integral coefficients in scattering amplitudes is to make their singularity structure manifest. This is naturally achieved by treating them as elements of fraction fields of
polynomial quotient rings, where poles correspond to algebraic vanishing loci. Simplification via partial fraction decomposition relies on exploiting the structure of the numerators and is governed, at least in a first approximation, by their behaviour on irreducible codimension-two varieties. These are identifiable through primary decompositions of the associated ideals. Despite the availability of general
algorithms, primary decompositions remain computationally challenging and often require tailored strategies. In this work, we extend an approach based on ideal saturation, identify an issue related to the breaking of Lorentz covariance in the choice of ideal generators, and present a solution based on fitting ansätze in special kinematic limits. We also provide substantial improvements to an
algorithm for the generation of numerical points in proximity of given varieties and to one for testing primality of unmixed ideals, both of which rely on a semi-numerical procedure for computing independent sets and variety dimensions. Finally, we present new codimension-two primary decompositions for five-point massless amplitudes at higher powers in the dimensional regulator, and for finite remainders with five-point one-mass kinematics, where a new spurious singular locus appears.
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Statistical Mechanics
Approach to Steady-State in Nested Resetting Processes
Callum Britton, Ben Le Jeune, Henry Alston et al. (+2 more)
We characterise the approach to nonequilibrium steady state in nested resetting processes by deriving accumulation times for the system, which quantify the effective first-passage time for the local establishment of steady state. For equal resetting rates, we obtain closed-form expressions showing that relaxation propagates as a wavefront with a delay that increases linearly along the resetting chain. We then extend this analysis to heterogeneous resetting rates, deriving exact steady-state distributions, spatial moments and accumulation times for both degenerate and non-degenerate resetting rates. We show that relaxation to steady state is ultimately governed by the minimum resetting rate in the system and, in degenerate systems, its multiplicity. These results provide a comprehensive analytical description of first-passage to nonequilibrium steady state in hierarchically coupled
stochastic resetting systems, with potential applications to relaxation and transport processes in biological systems.
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All authors Callum Britton, Ben Le Jeune, Henry Alston, Paul C. Bressloff, Thibault Bertrand
Quantum Physics
Exploring Asymmetric QEC Code Concatenation
Sayam Sethi, Maxwell Poster, Aditi Awasthi et al. (+3 more)
Concatenated
quantum error-correcting codes have recently gained popularity because they improve the effective distance of a joint code without requiring the discovery of new codes with desirable parameters. A common building block for such studies is the $[[4,1,2]]$ Iceberg code, the smallest error-detecting code and therefore the one with the lowest resource overhead. However, it has an asymmetric number of $X$ and $Z$ checks, and concatenating it produces skewed logical error rates (LERs) between the $X$ and $Z$ observables. This asymmetry can be mitigated by Clifford-deforming the individual blocks of the concatenation, but the space of possible Hadamard deformations grows doubly exponentially with the number of concatenation levels. We formalize this deformation space and investigate it by proposing six concrete deformation strategies, which we compare under a code capacity (with and without bias) noise model using a concatenated maximum-likelihood soft-information decoder. Among the strategies we study, one one of them achieves near-identical $X$ and $Z$ LERs in a logical-
memory experiment while simultaneously reducing the total LER (the sum of the $X$ and $Z$ error rates).
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All authors Sayam Sethi, Maxwell Poster, Aditi Awasthi, Willers Yang, Joshua Viszlai, Jonathan Mark Baker
High Energy Physics (Theory)
Anyon Crystallization by Statistics
Zohar Komargodski, Xuzixiang Lou, Ivri Nagar et al. (+3 more)
We revisit the long-standing problem of the anyon gas. We study the solvable near-bosonic limit of a large number of anyons $N$ at fixed $N/k$, where $1/k$ characterizes the statistical interaction. In this limit, the ground state is a
crystal with order $N/k$
lattice sites. The statistical interactions, mediated by a long-range gauge field, are completely screened within the crystalline phase. The resulting state is a conventional
crystal without superfluidity. We characterize this anyon
crystal by determining its unit-
cell size, ground-state energy, acoustic excitations, angular momentum crossings, and other properties. Our results indicate a
quantum phase transition between the
crystal at $k>k_c$ and a superfluid at $k<k_c$, with a critical value $k_c\simeq2\text{--}5$. These results imply that an anyon gas with only statistical interactions is not necessarily a superfluid, contrary to common lore. We also present a detailed analysis of the renormalization-group
evolution of anyon–anyon interactions, identifying many new potential fixed points and elucidating finite-size effects.
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All authors Zohar Komargodski, Xuzixiang Lou, Ivri Nagar, Domenico Orlando, Susanne Reffert, Amit Sever
Quantum Physics
In-orbit operation of a programmable quantum photonic processor
Simon Steiner, Peter Schiansky, Antonius Scherer et al. (+17 more)
Quantum technologies promise computational capabilities beyond the reach of classical systems. A forward-looking application lies in satellite missions, which increasingly depend on onboard computing under stringent constraints on size, weight and power.
Quantum photonics is particularly attractive here:
photon interference can enhance the machine-learning models needed to process large onboard data volumes, at fixed hardware resources. However, harnessing this interference requires more than generating single
photons, as they must remain mutually indistinguishable: a fragile condition that is hard to maintain within the technically demanding framework of a space mission, which includes a rocket launch, strong thermal drifts, and radiation. This is why
quantum states of light, though already generated and transmitted in orbit for secure communication and fundamental tests, have never been used as a computational resource. Here, we report a programmable
quantum photonic platform operating on a nanosatellite, processing two
photons in a six-mode universal integrated
circuit. By programming distinct
unitaries and tuning the
photons into indistinguishability, we observe two-
photon interference, establishing the on-board generation, manipulation and detection of non-classical light. This extends space-based technologies towards in-orbit
quantum-assisted computing, for instance local encoding of Earth-observation data, or nodes in a distributed
quantum network.
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All authors Simon Steiner, Peter Schiansky, Antonius Scherer, Riccardo Albiero, Mathias Dragosits, Zhenghao Yin, Martin Mauser, Patrik Zahálka, Raphael Pimenta, Cristóbal Melo, Cédric Léonard, Abhiram Rajan, Niki Di Giano, Antonino Caime, Roberto Osellame, Francesco Ceccarelli, Daniel Martínez, Tobias Guggemos, Iris Agresti, Philip Walther
Quantum Physics
Shreya Shukla, Abhijith Jayakumar and Andrey Y. Lokhov
Learning
quantum Hamiltonians from low-temperature thermal state measurements is a fundamental problem in
quantum physics. Scalability of existing methods is limited by the complexity of semidefinite optimization problems or partition function computation. Here, we develop a
quantum analog of classical score matching method that exploits generalized notions of derivatives and integration by parts in operator
algebras. We introduce a new Operator Score Matching loss function that recovers
Hamiltonian parameters by a simple gradient descent without the need to compute intractable normalization constants. Numerical experiments on the Gibbs states of the transverse-field Ising model, XXZ
spin chain,
Fermi-Hubbard model, and
lattice $\phi^4$ theory demonstrate efficient parameter recovery using finite-depth truncations of nested commutator expansions. Our results establish Operator Score Matching as a practical, partition-function-free framework for
quantum Hamiltonian learning.
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Quantum Physics
A dual-region ytterbium tweezer apparatus with an in-vacuum nanofiber cavity
Shunichiro Hashimoto, Hideki Ozawa, Yusuke Hisai et al. (+2 more)
We present a dual-region experimental apparatus for trapping single atoms of the fermionic isotope ytterbium-171 (${}^{171}\mathrm{Yb}$) with optical tweezers in a science chamber containing an in-
vacuum nanofiber cavity. A source region is located approximately $240\,\mathrm{mm}$ from the science chamber, preserving optical access around the chamber for high-numerical-aperture tweezer optics. A pulsed transport sequence based on longitudinal moving molasses launches atomic pulses toward the science chamber, where they are decelerated and recaptured in a magneto-optical trap. We subsequently load single atoms into a $2\times2$ tweezer array located approximately $50\,\mathrm{\mu m}$ from the nanofiber and measure a $1/e$ lifetime of $9.5(7)\,\mathrm{s}$. These results demonstrate that the dual-region architecture provides sufficient ${}^{171}\mathrm{Yb}$ atoms for single-atom tweezer operation near an in-
vacuum nanofiber cavity.
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All authors Shunichiro Hashimoto, Hideki Ozawa, Yusuke Hisai, Takao Aoki, Ryotaro Inoue
Strongly Correlated Electrons
Extended symmetric quantum phase in a honeycomb Heisenberg model with sublattice-selective interactions
Nai Chao Hu, Xing-Yu Zhang, Yuchi He et al. (+1 more)
Motivated by two-dimensional
bilayer systems we numerically study an anti-
ferromagnetic spin-$1/2$ Heisenberg model on the honeycomb
lattice with a nearest-neighbour exchange coupling $J_1$, and a next-nearest-neighbour exchange coupling $J_2'$ for the B sublattice sites only. Using infinite Projected Entangled-Pair States (iPEPS), variational uniform
matrix-product states on cylinders, and exact diagonalization, we find an extended symmetric regime $0.4\lesssim J'_2/J_1\lesssim0.6$, in which local observables show no
magnetic, valence-bond, or
chiral spin order. At $J'_2/J_1=0.5$, the PEPS correlation length grows systematically with bond dimension, and an inverse-correlation-length extrapolation favors a vanishing limit. We also find that various observables scale algebraically with the finite bond-dimension-induced correlation length, which points to a gapless
spin liquid ground state. We propose a $\mathbb{Z}_2$ Dirac
spin liquid parton state, with Dirac points that are protected by translation, time-reversal and three-fold rotation
symmetry, as a promising candidate state to explain the numerical results. We also discuss the possibility that the symmetric ground state is a featureless, short-range entangled state with a small gap.
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All authors Nai Chao Hu, Xing-Yu Zhang, Yuchi He, Nick Bultinck
Strongly Correlated Electrons
From Effective Temperature to Non-Boltzmann State Selection in Driven-Dissipative Quantum Criticality
Tiago Jorge, Jens Paaske and Pedro Ribeiro
Whether a nonequilibrium
quantum-critical steady state can be described by an effective temperature remains an open question. We address it in a voltage-biased electronic Lipkin–Meshkov–Glick model, a minimal driven-dissipative model of a collective
spin coupled to metallic leads. A controlled large-$N$ treatment reveals an overdamped open
quantum-critical regime distinct from the closed model. The surrounding
quantum critical fan, organized by temperature and voltage, is explored and fluctuations are found to be governed by an effective temperature $T_{\rm eff}$. At strong bias, the transition becomes first-order through a tricritical point. Remarkably, the same $T_{\rm eff}$ governs the strongly driven regime, but now varies across the entire order-parameter landscape. The steady state is therefore selected by a non-Boltzmann rule, shifting the first-order transition away from the equal-depth point of a deterministic potential. Driven criticality thus remains organized by an effective temperature while revealing non-thermal state selection.
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General Relativity and Quantum Cosmology
Reconnection of Gravitational Fields
Luca Comisso and Felipe A. Asenjo
In a tetrad formulation of general relativity, an ideal Ohm-type condition for the gravitational field implies the conservation of gravitational fluxes and the preservation of the connectivity of gravitational field sheets. We investigate the consequences of departures from ideal gravitational
evolution by developing a theory of gravitational reconnection, defined as a change in the connectivity of gravitational field sheets arising from the breakdown of the ideal frozen-in
evolution of the gravitational field. We derive quantitative measures of the gravitational reconnection rate, show that gravitational reconnection alters the energy-momentum exchange between the gravitational and matter sectors, and determine how it modifies the
evolution of gravitational helicity. Our results provide a quantitative framework for describing changes in gravitational connectivity and their consequences in dynamical spacetimes.
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General Relativity and Quantum Cosmology
Frozen-In Gravitational Fields
Felipe A. Asenjo, Maricarmen A. Winkler and Luca Comisso
Spacetime can undergo complex nonlinear
evolution, as governed by the Einstein field equations, and a central challenge is to understand the
geometric structures that arise, persist, and interact throughout its
evolution. Using a formulation of Einstein equations that parallels nonlinear electrodynamics of continuous media, we show that general relativity admits gravitational field connections—two-surfaces and associated field lines whose connectivity is maintained by the spacetime dynamics. This gravitational frozen-in behavior is enabled by an ideal Ohm-type condition for the gravitational field. We further show that the same framework naturally leads to a conserved “gravitational
magnetic” flux. A conserved gravitational helicity also emerges, with a clear topological interpretation in terms of gravitational field-line structures. These results identify well-defined topological constraints on admissible spacetime
evolution and provide an organizing principle underlying the nonlinear dynamics of spacetime.
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History and Philosophy of Physics
Before WIMPs: Neutrinos and the origins of particle dark matter
Jaco de Swart
After four decades of null-results, the experimental quest to discover a dark matter particle ardently continues. While confidence in the leading candidate, the Weakly Interacting Massive Particle (WIMP), is waning, its explanatory success still shapes current experimental approaches and theoretical expectations - from underground detecting efforts in Europe, China, and the U.S. to modern theories of
cosmic structure. This paper traces the origins of this particle-based paradigm to a critical predecessor: the
neutrino-dominated universe. Proposed in the early 1970s as a solution to extra-
galactic anomalies,
neutrinos became the leading explanation of 'missing matter' following experimental hints of
neutrino mass in 1980. Although short-lived, the model's coherent picture of
cosmic evolution and structure formation set strong conceptual and methodological standards - providing critical impetus to the field of particle cosmology. Examining this history invites renewed reflection on how such past aims and expectations continue to guide dark matter inquiry today.
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High Energy Physics (Theory)
Functional Dimensional Regularization
Piero Beretta and Alessandro Codello
We introduce and develop Functional Dimensional Regularization (FDR), a novel functional renormalization group (RG) framework that extends the principles of dimensional regularization beyond the perturbative $\varepsilon$-expansion. The key insight is to define the FDR beta functions, valid in any continuous dimension $d$ and characterized by threshold functions, as a sum over all critical dimensions of the corresponding scheme-independent beta functions computed in DR. We demonstrate that this formalism exhibits all the hallmarks of a fully-fledged functional RG. Within the local potential approximation, we perform a general fixed point analysis, recovering the $\varepsilon$-expansion for all multi-critical models and establishing a direct connection to functional scaling solutions, spike plots, and eigen-perturbation spectra. Extending the framework to the second order of the derivative expansion, we compute the critical exponents for the Ising universality class in $d=3$, providing estimates for the anomalous dimension $\eta$ and RG spectrum that converge rapidly and show favorable agreement with state-of-the-art results. We present a detailed comparison with non-perturbative and proper-time RG approaches, highlighting structural similarities and key differences. In particular, we introduce a “
distillation” procedure that allows one to systematically derive the FDR flow from any other one-loop-exact RG scheme. Our results establish FDR as a self-contained and competitive RG framework that combines the technical simplicity of dimensional regularization with the versatility of the functional approach.
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General Relativity and Quantum Cosmology
Higher derivative Hořava-Lifshitz fermions: from superconductivity to atomic spectroscopy
A. A. Araújo Filho, K. E. L. de Farias, N. Heidari et al. (+2 more)
We investigate an isotropic Hořava-Lifshitz
fermion theory supplemented by a dimension-six spatial derivative operator, preserving first order time
evolution while modifying the ultraviolet dispersion relation. Within the regime of validity of the derivative expansion, we develop three complementary consequences of the $z=2$ sector. First, a Bardeen-Cooper-Schrieffer/Nambu-Jona-Lasinio (BCS/NJL) mean field treatment of
fermion pairing yields the particle and antiparticle quasiparticle spectra, the finite temperature gap equation, and the gauge invariant criterion for a stable superconducting phase. The modified dispersion alters both the density of states governing the pairing scale and the electromagnetic vertices entering the Meissner response. Second, using the scalar pole denominator as a minimal
spin independent exchange kernel, we derive an exponentially damped and oscillatory massive potential and obtain the corresponding Born scattering amplitudes. The quartic momentum dependence renders both the forward and total cross sections finite and produces a large transfer behavior distinct from Rutherford scattering. Finally, we evaluate the induced shifts of the hydrogenic $1S$, $2S$, and $2P$ levels in closed form, retaining the full dependence on the interaction range. In other words, these latter results gives direct spectroscopic constraints on the product of
nuclear and leptonic couplings, with muonic atoms, showing the respective sensitivity to the short distance Hořava-Lifshitz sector.
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All authors A. A. Araújo Filho, K. E. L. de Farias, N. Heidari, M. Paganelly, A. F. Santos
Solar and Stellar Astrophysics
The oldest low-$\alpha$ thin disc stars
Riano E. Giribaldi, Laura Magrini, Marco Palla et al. (+1 more)
The formation pathway of the $\alpha$-poor Milky Way thin disc remains under debate. The latest observational data indicates the presence of comparable numbers of old
stars in both the low- and high-$\alpha$ disc components, suggesting either coeval or overlapping formation epochs. Using GALAH DR4, we provide evidence that the $\alpha$-poor
stars coexist with $\alpha$-rich
stars up to $\sim$12.5 Gyr.
Stellar ages of 0.5 Gyr precision were re-derived for nearly $30\,000$ subgiant
stars using accurate effective temperatures ($T_{\rm{eff}}$) from the infrared flux method (IRFM) together with distances based on
Gaia parallaxes. About 22% of the sample constitutes a population peaking at 9.2 Gyr, with evidence for an extended old-age tail reaching 12.5 Gyr. Among
stars older than 10 and 11 Gyr, between 20 and 30% have relative low [$\alpha$/Fe] and
solar-like
metallicities ($-0.5 \leq \mathrm{[Fe/H]} \leq +0.5$ dex). These
stars exhibit kinematics consistent with those of near
solar-age $\alpha$-poor
stars in the thin disc. These
stars can be evolved Sun-like
stars, i.e. old
solar analogues, whose $T_{\rm{eff}}$ and
gravity modified with the time. Comparison with a well-tested
Galactic disc chemical
evolution model supports the presence of a significant fraction of old, $\alpha$-poor disc
stars, confirming the plausibility of our selection criteria. We provide a catalogue with the selected sample to facilitate spectroscopic follow-ups at high resolution.
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All authors Riano E. Giribaldi, Laura Magrini, Marco Palla, Carlos Viscasillas Vázquez
Earth and Planetary Astrophysics
Probing Exoplanetary Rings with Asterodensity Profiling: A PhotoRing Analysis of Kepler-51
Jorge I. Zuluaga, Sebastian Numpaque, David M. Kipping et al. (+1 more)
The Kepler-51 system hosts transiting super-puff
planets whose extremely low bulk densities challenge structural models, possibly because unresolved rings inflate their inferred radii. We test this hypothesis by combining asterodensity profiling with TTV-aware transit fits of Kepler long-cadence photometry. For Kepler-51b we measure a density ratio $\Psi\equiv\rho_{\star,\mathrm{obs}}/\rho_{\star,\mathrm{true}} = 1.18\pm0.06$, a $2.9\sigma$ offset from $\Psi=1$; for Kepler-51d we find $\Psi=1.04\pm0.08$ ($0.6\sigma$), consistent with no anomaly. Unmodelled eccentricity is disfavoured for
planet b by TTV-derived dynamical constraints ($p=0.007$) but remains viable for
planet d ($p=0.33$). The offset of Kepler-51b is also compatible with the PhotoRing (PR) effect of unmodeled rings. Using a
geometric ringed-transit forward model and
Bayesian retrieval, we identify ring configurations that reproduce the transit observables and the measured density ratios. The preferred solutions are consistent with compact, moderately inclined rings that raise the true bulk densities by factors of $2-5$. Conversely, the absence of a large PR offset excludes extended, optically thick, high-obliquity rings at $99\%$ credibility for b and $70\%$ for d from archival photometry alone. These objects may thus be "puff ringed
planets" although recent JWST observations of Kepler-51d show no direct signature of an opaque ring. While the required impact parameters and
stellar densities show tension with independent constraints -attributable to Kepler's 30-minute cadence- this study presents the first complete application of the PR effect, offered as a methodological demonstration and exclusion experiment rather than as evidence that rings are present. All code is publicly available to support applications to other systems.
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All authors Jorge I. Zuluaga, Sebastian Numpaque, David M. Kipping, Jaime A. Alvarado-Montes
High Energy Astrophysical Phenomena
Early NIR echo and the time variable mass loss history of Type IIn SN 2024kgi
Naveen Dukiya, Kuntal Misra, Andrea Pastorello et al. (+30 more)
We present a comprehensive analysis of the long-term photometric and spectroscopic monitoring campaign of the Type IIn
Supernova (SN) 2024kgi. The SN reaches at peak an $r$-band absolute magnitude of $-19.81 \pm 0.06$ mag and a bolometric luminosity of $\sim 2 \times 10^{43}$ erg s$^{-1}$. We observe a break in the lightcurve at day $\sim 312$, after which the luminosity decline changes from $t^{-1.0}$ to $t^{-4.5}$, likely due to the shock sweeping the dense CSM. We introduce a semi-analytical lightcurve modeling approach for CSM-interaction in transients that accounts for variable
diffusion time. We hence estimate a CSM mass of $2.34^{+11.8}_{-1.6} M_{\odot}$ and with a density profile $\rho_{csm} \propto r^{-2.74}$, indicating progressively increasing mass loss toward the SN explosion. The ejecta signatures emerge as broad H, He, and Ca II triplet lines, at day $\sim 80$, much earlier than expected from a spherically symmetric CSM, suggesting asymmetry in the CSM. After the lightcurve break, the H lines exhibit a wavelength-dependent deficit in the red-wing flux, indicating new
dust formation in the ejecta and/or in the post-shock gas. We observe an NIR excess from day $\sim 40$ onwards. We attribute the early NIR excess before the lightcurve break solely to the NIR echo from pre-existing
dust, as there are no other indications for new
dust formation. The late-time NIR excess likely has contributions from both the preexisting and newly formed
dust. The steady increase in mass loss, slow CSM velocity, and asymmetric CSM favor a binary interaction-induced mass loss.
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All authors Naveen Dukiya, Kuntal Misra, Andrea Pastorello, Andrea Reguitti, Anjasha Gangopadhyay, Aravind P. Ravi, Brian Hsu, Noah Franz, David J. Sand, Nathan Smith, Jennifer E. Andrews, Moira Andrews, K. Azalee Bostroem, Collin Christy, Monalisa Dubey, Joseph R. Farah, Archana Gupta, Estefania Padilla Gonzalez, Emily Hoang, D. Andrew Howell, Curtis McCully, Darshana Mehta, Megan Newsome, Jeniveve Pearson, Nicolas Meza Retamal, Jeonghee Rho, Manisha Shrestha, Bhagya Subrayan, Giacomo Terreran, Lina Tomasella, Stefano Valenti, Giorgio Valerin, Kathryn Wynn