General Relativity and Quantum Cosmology
Mode decomposition methods for the analysis of black hole ringdown signals
Andrzej Krolak and Massimo Tinto
The ringdown phase of a binary black hole merger encodes fundamental information about the remnant through its quasinormal mode (QNM) spectrum. Extracting multiple modes from gravitational-wave data is essential for black-hole spectroscopy but remains challenging due to the short duration of the signal, limited signal-to-noise ratio (SNR), and interference between modes. In this work, we investigate the applicability of Empirical Mode Decomposition (EMD) and Variational Mode Decomposition (VMD) to the analysis of post-merger gravitational-wave signals. Using Monte Carlo simulations of noisy ringdown signals composed of pairs of QNMs, we assessed the ability of these methods to separate the two modes and estimate their frequencies. The instantaneous frequency is obtained via the
Hilbert transform (HT) and our new proposed method, named instantaneous frequency and amplitude determination (IFAD). We analyze performance over a wide range of SNR values relevant to current and future gravitational-wave detectors. Our results show that both EMD and VMD can resolve multiple modes, and VMD provides significantly more accurate frequency estimates. We also introduce a modified instantaneous frequency
estimator that improves accuracy over the
Hilbert transform. The study quantifies the conditions under which two-mode resolution is feasible and highlights the limitations imposed by closely spaced mode frequencies and short signal duration. These results are relevant for current observations and for future high-SNR detections expected from space-based and next-generation ground detectors.
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Chemical Physics
Oscillator Strengths and Transition Dipole Moments from a Simplified Equation-of-Motion Coupled Cluster Formalism within the Frozen-Pair Approximation
Seyedehdelaram Jahani, Katharina Boguslawski and Pawel Tecmer
In this work, we derive the working equations for the transition density
matrices within the equation-of-motion frozen-pair coupled-cluster framework. We focus specifically on the recently developed EOM-fpCCSD and EOM-ptCCSD models and present the corresponding transition dipole moments and oscillator strengths obtained via approximate expressions. This formulation avoids the computational overhead of solving the coupled-cluster $\Lambda$ equations. Furthermore, we employ a
matrix inverse approximation to eliminate the need for explicit calculation of the left EOM eigenvectors. The accuracy of the resulting EOM-fpCCD and EOM-ptCCSD excited-state properties is benchmarked against the linear-response (LR)-CCSD method. Our results demonstrate that the description of excited state properties is improved when using EOM-fpCCSD and EOM-ptCCSD models compared to the standard EOM-CCSD variant.
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Plasma Physics
Ionization potential depression in degenerate plasmas and Pauli blocking of multi-electron ions
Gerd Röpke
The composition of partially ionised
plasmas is investigated for densities and temperatures at which the free electrons are degenerate. Based on a
quantum statistical approach, the effect of Pauli blocking is addressed. Specifically, one- and two-electron ions are studied. Approximations for deriving an in-medium Schrödinger equation for the ionization potential are indicated. New results regarding the degree of ionisation and the Mott effect are presented. Standard codes for
plasma properties do not take Pauli blocking effects into account and are therefore unable to explain the experiments in the high-density regime, where the electrons are degenerate.
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Materials Science
Machine-learned dynamics of surface polarons at reduced oxide surfaces
Luca Leoni and Cesare Franchini
Reducible
oxides exhibit a rich interplay of electronic, structural, and chemical properties that underpins applications in catalysis, photovoltaics, batteries, and energy storage. This interplay is strongly shaped by excess electrons, often introduced by oxygen vacancies, that localize as small polarons and influence charge transport and surface chemistry. At surfaces, these polarons play a central role in charge localization, mobility, and reactivity, yet their finite-temperature dynamics remain difficult to access from first principles due to the long time scales needed to adequately sample polaron's hopping. To overcome this limitation, we extend machine-learning-assisted polaron dynamics to redox-active
oxide surfaces, using oxygen-deficient rutile TiO$_2$(110) as a paradigmatic case. By accessing several nanoseconds of dynamics over a range of temperatures, we show that small-polaron mobility at the reduced rutile TiO$_2$(110) surface is suppressed by several orders of magnitude relative to the corresponding bulk material, providing a microscopic interpretation of the lower electron mobilities observed in porous rutile TiO$_2$ compared with single-
crystal samples. This suppressed mobility arises from the loss of favourable hopping pathways: surface polaron motion is largely confined to planar inter-row trajectories within the second topmost layers, with only rare interlayer hopping events. These results establish a transferable machine-learning strategy for investigating polaron dynamics in reducible
oxides.
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Materials Science
Combining Frozen Trajectory Excitation and TACAW for in silico Time-Resolved Vibrational Electron Energy Loss/Gain Spectroscopy
Wojciech Marciniak, Joanna Marciniak, José Ángel Castellanos-Reyes et al. (+1 more)
Seeing that ultrafast (picosecond timescale) vibrational electron energy loss spectroscopy (EELS) should soon be experimentally realizable, we present in silico approach capable of providing insight from the computational physics perspective. We present a framework that combines frozen trajectory excitation (FTE) with time auto-correlation of auxiliary wavefunctions (TACAW) to study the time-dependent spectral response of non-
equilibrium lattice dynamics in a way comparable directly to experiment - (scanning) transmission electron microscope EELS, (S)TEM-EELS. In this approach, a selected
phonon excitation is first introduced into an
equilibrium molecular dynamics trajectory using FTE, after which the atomic positions during subsequent relaxations are treated with short-time TACAW analysis performed at different pump-probe delays. This yields momentum- and energy-resolved electron-scattering signals bearing a
phonon imprint during the relaxation process, going beyond time-dependent diffuse-scattering intensities alone. We demonstrate the approach for fcc-Ni and 3C-SiC and discuss the observed
phonon mode coupling and spectral redistribution during
phonon relaxation.
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All authors Wojciech Marciniak, Joanna Marciniak, José Ángel Castellanos-Reyes, Ján Rusz
Mesoscale and Nanoscale Physics
A Collective-Spin Derivation of the Uniform Magnon Hamiltonian in Cavity Magnonics
Tomas Aguiar and Marcos Cesar de Oliveira
We present a direct collective-
spin derivation of the effective uniform-mode
Hamiltonian used in cavity magnonics. Starting from a nearest-neighbor Heisenberg ferromagnet coupled to long-wavelength
magnetic fields, we show that the relevant dynamics can be restricted to the fully symmetric
spin sector, where the exchange interaction contributes only a constant energy shift and the ferromagnet behaves as a macrospin of length $Ns$. Applying the Holstein–Primakoff transformation directly to this total
spin yields the usual uniform
magnon mode and its leading nonlinear corrections without first introducing site-resolved bosonic operators. This collective formulation makes explicit the interpretation of the ferromagnet as a synthetic large-
spin atom and provides a compact route to the effective
Hamiltonians used in driven and Floquet cavity magnonics. As a physical consequence, the leading nonlinear correction produces an occupation-dependent reduction of the effective
magnon–
photon coupling, providing a simple signature of finite-
spin saturation under strong uniform-mode driving.
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Physics and Society
AI can help scientists publish less
Gianfranco Bertone
We can do more than defend science from a flood of AI-assisted papers. Used well, AI offers a historic opportunity to correct distortions in the publication system, help us publish fewer and better papers, and give scientists back the time to do their best work.
Superconductivity
Observation of intertwined charge density wave order and superconductivity in Janus monolayer
Subhajit Pramanick, Shubham Patel, Sudip Chakraborty et al. (+1 more)
Low-dimensional transition-metal dichalcogenides (TMDCs) provide an ideal platform for studying the emergence of charge density wave (CDW) and superconductivity. The discovery of emergent CDW order in 1T $\mathrm{ZrTe_2}$ monolayer raises an important question: does this instability persist when one $\mathrm{Te}$ chalcogen layer is substituted by $\mathrm{Se}$? In the present work, we investigate the CDW (2$\times$2$\times$1) and superconducting instability in 1T $\mathrm{ZrSeTe}$ Janus monolayer using first-principles calculations. The
phonon spectrum exhibits a pronounced anomaly at the $\mathrm{M}$ point of the irreducible Brillouin zone, arising from enhanced electron-
phonon interaction together with electronic instabilities originating from both interband and intraband scattering. The resulting
lattice distortion reconstructs the electronic structure, opening a small indirect band gap, driving the system from a semi-metallic to a semiconducting state. The energy gain associated with the distortion is significantly smaller than that of $\mathrm{ZrTe_2}$ monolayer, indicating that the replacement of one $\mathrm{Te}$ chalcogen layer with $\mathrm{Se}$ weakens the CDW instability. We have further investigated the effects of electronic correlation and biaxial strain, both acts as effective tuning parameters for the instabilities concerened. In the high temperature undistorted phase, $\mathrm{ZrSeTe}$ exhibits
phonon mediated two-gap superconductivity. It originates primarily from the robust coupling between the soft
phonon mode at $\mathrm{M}$ point and the electronic bands predominantly derived from $\mathrm{Zr}$ $\mathit{d}$ and $\mathrm{Te}$ $\mathit{p}$ orbitals crossing the
Fermi level.
Spin-orbit coupling (SOC) further modifies the electronic states and reduces the superconducting transition temperature.
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All authors Subhajit Pramanick, Shubham Patel, Sudip Chakraborty, A. Taraphder
Fluid Dynamics
Resistance tensors for aggregate particles with Stokesian dynamics
J. Gissinger, G. Voth, B. Mehlig et al. (+1 more)
The response of particles to low-Reynolds flow can be compactly predicted with resistance or mobility tensors. However, the difficulty of obtaining accurate values for the elements of these tensors for specific geometries has held back work on particles with complex shapes. Here we show how Stokesian dynamics can be adapted to efficiently compute the resistance and mobility tensors of rigid and flexible aggregates, including confinement by walls. We introduce SHAPES, an implementation of the method, and demonstrate its capabilities for complex geometries including curved fibres,
chiral dipoles, interacting aggregates, and active swimmers. Aggregates are represented by assemblies of beads designed to reproduce the geometry and motion of rigid or flexible particles. This coarse-grained description preserves the essential hydrodynamic interactions while substantially reducing computational cost. The method accurately reproduces known exact and approximate solutions, as well as experimental observations. The ability to compute the complete resistance and mobility tensors provides new insight into how aggregate shape controls translation, rotation, and coupling to fluid-velocity gradients. Previous descriptions often relied on simplified models retaining only a few
symmetry-allowed couplings. While useful, such reduced descriptions are not always structurally stable under small perturbations of particle shape. Computing the full tensors makes it possible to draw robust conclusions and relate them to shape
symmetry and hydrodynamic interactions. In particular, the method allows systematic analysis of non-Jeffery couplings to the strain rate that arise for helicoidal aggregates. SHAPES therefore provides a versatile framework for studying rigid and flexible aggregates in microfluidic, biological, and environmental flows.
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All authors J. Gissinger, G. Voth, B. Mehlig, F. Candelier
Quantum Physics
Calibrated Helstrom geometry on the Bloch ball via Connes spectral distance
Kaushlendra Kumar
We show that the equal-prior Helstrom trace-distance geometry of
qubit states is recovered from Connes spectral distance in a finite scalar-
qubit-scalar model. The two scalar reference sectors couple isotropically to the
qubit block through identity Dirac links, so that the full Bloch ball, including mixed states, inherits its standard chordal trace-distance geometry from the finite spectral metric. The scalar-sector distances serve a distinct calibration role: they determine the individual link lengths, satisfy a Pythagorean consistency relation, and reconstruct the middle-sector scale.
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High Energy Physics (Theory)
Unifying Gravities with Internal Interactions based on $SO(10)$ GUT
Stelios Stefas and George Zoupanos
Building on two key ingredients, namely the well established gauge-theoretic formulation of
gravity and the observation that the tangent space of a curved
manifold need not have the same dimension as the
manifold, we discuss how all known fundamental interactions can be accommodated within a single unified framework. The unification is realised by enlarging the tangent group of the four-dimensional spacetime
manifold to $SO(2,16)$, a choice that simultaneously encompasses both the gauge group underlying the gravitational sector and the $SO(10)$ Grand Unified Theory for the internal interactions. The gravitational theories entering this construction are Conformal
Gravity and Fuzzy (Noncommutative)
Gravity, each formulated in gauge-theoretic terms.
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Astrophysics of Galaxies
GA-NIFS: The interplay between feedback and star formation at 3 < z < 9 probed by JWST/NIRSpec IFU
L. Ulivi, M. Perna, S. Arribas et al. (+24 more)
The study of starburst- and AGN-driven feedback is fundamental for understanding the processes that shape
galaxy growth, quench
star formation, and drive the co-
evolution of
galaxies and their central black holes. We present a spatially resolved study of six
galaxies at $3 < z < 9$, including starburst- and AGN-dominated systems, observed with JWST/NIRSpec IFU in low- ($R \sim 100$) and high-resolution ($R \sim 2700$) mode. Previous analysis of $R \sim 2700$ data revealed ionized
outflows in all these
galaxies. We explore possible links between
outflows and
stellar population properties to assess the mechanisms driving
galaxy evolution at early epochs. Combining the spatially resolved
stellar population analysis with the
outflow properties, we find that the most massive
galaxies ($M_\star > 5 \times 10^{10} M_\odot$) with strong AGN-driven ionized
outflows show evidence of past quenching episodes occurring within the last $\sim 100$–$300$ Myr, mainly in the
nuclear regions ($r < 3$ kpc). In contrast, higher-
redshift ($z > 5$) and less massive ($M_\star < 10^{10} M_\odot$) starburst
galaxies with powerful (starburst-driven)
outflows appear to have experienced continuous growth, with no clear sign of quenching. Massive
galaxies with weaker
outflows do not show evidence of quenching in their history. One massive AGN host (GS20936) shows evidence for a recent ($10$–$30$ Myr) rejuvenation phase, likely fueled by a recent major merger. These results suggest that (AGN-driven)
outflows can already play a key role in shaping the SFHs of massive
galaxies at early
cosmic epochs.
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All authors L. Ulivi, M. Perna, S. Arribas, B. Rodríguez Del Pino, P. G. Pérez-González, I. Lamperti, C. Marconcini, H. Übler, F. D'Eugenio, T. Böker, A. J. Bunker, S. Carniani, S. Charlot, R. Maiolino, P. Alvarez, E. Bertola, G. Cresci, M. Curti, M. Hamed, L. R. Ivey, G. C. Jones, E. Parlanti, R. Pascalau, C. Prieto Jimenez, B. Trefoloni, G. Venturi, S. Zamora
Instrumentation and Methods for Astrophysics
Design and Commissioning of an Iodine Cell for the ESPRESSO Spectrograph
Gillian Nave and R. Paul Butler
High resolution echelle spectrographs remain the backbone of precision Doppler radial velocity (RV) programs, detecting almost all known
exoplanets within 50 pc. Precision Doppler RV spectrographs have traditionally fallen into two camps. Standard unstabilized echelles observe targets through an iodine absorption
cell. The iodine spectrum is embedded on the target spectrum, and provides a wavelength scale and a record of the spectrometer point-spread-function (PSF). Super-stabilized spectrometers are placed inside a
vacuum tank, temperature stabilized at the level of 0.001 deg C, and fed by two scrambled fibers. One fiber carries the target, the other the calibration source (ThAr, Fabry-Pérot,
laser-comb). Both techniques have found hundreds of
planets and produce sub m/s uncertainties on the highest resolution echelles currently available. Both techniques have advantages and disadvantages and can be combined with the goal of reducing the long-term Doppler RV uncertainty to the sub 10 cm/s level. We have designed, built, calibrated, and commissioned an iodine
cell for the European Southern Observatory's (ESO) ESPRESSO spectrograph. The design and construction of the
cell was carried out in 2022. The
cell was calibrated at the National Institute of Standards Technology (NIST) Atomic Spectroscopy laboratory in early 2023 and was commissioned in May 2023. The commissioning run was limited to evening and morning twilight on VLT-UT2. Five main sequence
dwarf stars ranging in spectral type from G to early K were observed between 4 and 6 nights spanning a total of ten nights.
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Quantum Physics
Aligning Quantum Operators with Large Language Models
Rogerio Feris, Yunchao Liu, Pengyuan Li et al. (+2 more)
Can Large
Language Models (LLMs) understand and reason about
quantum operators? Despite their remarkable capabilities in mathematics and symbolic
reasoning, LLMs remain inherently blind to
quantum representations such as
unitary matrices. In this work, we take a step toward bridging this gap by introducing an approach that maps
unitary operators into the latent space of an LLM, enabling unified modeling over
quantum and linguistic inputs. We instantiate this idea on Clifford+T
circuit synthesis over a Pauli rotation gate set, where our model achieves results competitive with state-of-the-art methods and scales consistently with training data, with no signs of saturation. Our approach further enables
language-conditioned synthesis, allowing gate constraints unseen during training to be specified directly in natural
language. This work suggests a path toward
quantum–aware foundation models that can natively interpret and reason about
quantum operations, which could have broader implications reaching across
quantum compilation and
algorithm discovery.
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All authors Rogerio Feris, Yunchao Liu, Pengyuan Li, Hang Hua, David Kremer
Quantum Physics
Universal Crossovers of Stabilizer Entropy Beyond Criticality
Reyhaneh Khasseh, E. A. Ramirez Trino and M. A. Rajabpour
Stabilizer Rényi
entropy has emerged as a probe of nonstabilizerness in
quantum many-body systems, but its scaling structure beyond critical points remains poorly understood compared with
entanglement entropy. Recent field-theory approaches indicate that stabilizer
entropy contains universal critical data and boundary-sensitive terms, raising the question of how these structures extend into massive and crossover regimes. We address this problem for a broad class of finite-range
spin chains at Rényi index one-half. We derive exact finite-size formulas for both full periodic chains and finite intervals of the infinite chain, making the universal crossover from critical to noncritical behavior analytically accessible. In periodic geometry, the
entropy obeys a volume law away from criticality and exhibits a universal finite-size crossover controlled by the competition between system size and correlation length. We also show that the large-scale SRE density develops a cusp across the field-tuned critical line, while the XX endpoint is governed by a distinct scaling regime associated with the saturation point. In the subsystem geometry, the interval
entropy separates bulk critical behavior from boundary contributions generated by the way the finite region cuts the infinite chain. The crossover from critical to massive behavior is then encoded in boundary constants and universal functions controlled by the correlation length. Through exact stabilizer-
entropy correspondences, the scaling theory extends to internal XY reductions, Finite-range
spin chains, and Cluster–Ising representatives. Our results provide an exact
lattice benchmark for the emerging QFT description of stabilizer
entropy beyond isolated conformal points.
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High Energy Astrophysical Phenomena
Observational Biases and Improved Modelling of Off-axis Relativistic Jets
A. J. Cooper, A. P. Scott, L. Rhodes et al. (+8 more)
Relativistic Doppler boosting significantly affects the observed emission of astrophysical jets resulting in observational biases. In this work we investigate the observational biases and modelling opportunities which arise due to relativistic boosting using two X-ray binary case studies. Using the one-sided jet ejecta from MAXI J1535-571, we demonstrate that incorporating non-detections of the receding jet ejecta into kinematic modelling can significantly improve parameter estimation, reducing posterior uncertainties by over 40%. For the bipolar jets of MAXI J1820+070, we recover the intrinsic jet rest-frame emission of both approaching and receding jet components, demonstrating that they follow a common powerlaw
evolution. Using this rest-frame emission profile as a base model, we show that current observational strategies strongly bias against detecting ejecta with high initial Lorentz factors >5 and receding ejecta components across a broad region of parameter space. These results highlight the importance of observational strategy selection, particularly early-time and late-time observations, and leveraging non-detections in the modelling of relativistic jets. More generally, quantifying observational biases and maximising modelling capabilities by incorporating the non-detection of receding jets can be employed to enhance interpretation of future gravitational-wave/optically-triggered observations of off-axis, extragalactic jetted transients.
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All authors A. J. Cooper, A. P. Scott, L. Rhodes, F. Carotenuto, A. K. Hughes, J. H. Matthews, K. Savard, F. J. Cowie, E. L. Elley, C. Lilje, R. Fender
Mesoscale and Nanoscale Physics
Enhancement of spin current in Fe$_{85}$Co$_{15}$/Ni$_{80}$Fe$_{20}$ bilayers via interlayer ferromagnetic coupling
A. A. Pérez Martínez, D. Velázquez Rodríguez, D. Goijman et al. (+6 more)
We present a detailed study on how the strength of the interlayer
magnetic coupling on Fe$_{85}$Co$_{15}$/Ni$_{80}$Fe$_{20}$
bilayers modifies the
spin wave behavior of this system. A series of Fe$_{85}$Co$_{15}$/Ni$_{80}$Fe$_{20}$
bilayers deposited on MgO[100] substrates were grown by magnetron sputtering.
Magnetic characterization of the samples was performed using a vibrating sample magnetometer and magneto-optical Kerr effect. The in-plane hysteresis loops reveal a cubic
magnetic anisotropy of magnetocrystalline origin, with easy and hard axis along the [100] and [110] Fe-Co crystallographic directions, respectively.
Ferromagnetic resonance measurements were performed to analyze the in-plane angular dependence of the resonance field, and also the resonance field at several frequencies was determined along the hard axis. By using a
bilayer model in the frame of the Landau-Lifshitz-Gilbert magnetization equation of motion, the magnetization precession components were calculated, as well as the dependence of precession area on the Fe-Co layer thickness and the
ferromagnetic interlayer coupling. We observe a maximum in the area of the ellipsoid generated by the magnetization precession of the permalloy layer at a certain exchange constant, showing that this effect could be used to maximize the injected
spin currents, which could be tuned by changing the interlayer exchange constant in
bilayer systems, the saturation magnetization of the materials, or the excitation frequency.
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All authors A. A. Pérez Martínez, D. Velázquez Rodríguez, D. Goijman, T. Torres, M. H. Aguirre, J. Gómez, A. Butera, E. De Biasi, J. Milano
High Energy Astrophysical Phenomena
Resolving the temporal evolution of M87 jet with $\lesssim0.1$-arcsec Chandra observations
Camille Poitras, Gerrit Schellenberger, Ralph Kraft et al. (+3 more)
We present a 13-year Chandra/HRC-I study of the M87 jet, using point-spread-function deconvolution to achieve unprecedented sub-arcsecond X-ray resolution of its kiloparsec-scale structure and temporal
evolution. The deconvolved images reveal previously blended structures within the jet, including two components in HST-1 and complex morphology in downstream
knots. Flux measurements reveal a global decrease in X-ray emission across the jet of up to 84 %, consistent with synchrotron cooling. Modeling the fading yields minimum
magnetic field strengths of ~324-1006 $\mu$G for HST-1 and ~41-115 $\mu$G for
knot A. Consistent with synchrotron cooling, multi-wavelength comparisons with ALMA, JWST, and HST show that the principal X-ray structures closely match the jet width and
knot locations observed at lower energies, while the X-ray emission is generally shifted upstream. Proper motion measurements show that jet features exhibit both quasi-stationary and superluminal apparent motions, reaching up to 4.8 $c$ for HST-1, and also demonstrate that unresolved component blending can substantially bias inferred velocities. These results demonstrate the unique capability of high-resolution Chandra X-ray imaging over long temporal baselines to resolve the evolving substructure of relativistic jets and to probe the particle acceleration and energy dissipation processes that shape their dynamics.
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All authors Camille Poitras, Gerrit Schellenberger, Ralph Kraft, Paul Nulsen, Marie-Lou Gendron-Marsolais, Eileen Meyer
Earth and Planetary Astrophysics
Solar System Technosignatures
T. Joseph W. Lazio
NASA has five robotic space probes on escape trajectories from the
Solar System, and the Interstellar Probe concept was considered in the recent U.S.
Solar & Space Physics Decadal Survey. While none of these robotic probes will be operational when they reach another
star, it is natural to ask whether another civilization also might have sent out interstellar probes. Serious consideration of interstellar probes dates at least to R. Bracewell in the early 1960s, and the discovery of three interstellar objects has rekindled some of that interest. I consider current limits on signatures of extraterrestrial technology in the
Solar System, both objects on various orbits ("probes") and surface artifacts, using data from planetary exploration and astronomical sky surveys. Perhaps not surprisingly, the completeness to which the
Solar System has been searched varies as a function of distance from the Sun. I conclude that only extremely crude upper limits can be placed on the existence of technosignatures in the
Solar System and that, in some cases, relatively large probes or surface artifacts would have escaped detection. I also highlight areas that might be profitable for improving these limits considerably.
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Instrumentation and Methods for Astrophysics
A Scalable Fast Multipole Method Poisson Solver for the RAMSES code: I. Unigrid Algorithm
Jun-Young Lee and Romain Teyssier
We present a scalable Poisson solver with $O(N)$ complexity based on the fast multipole method (FMM) implemented in RAMSES. Our FMM constructs a hierarchy of FMM grids on top of the pre-existing Cartesian grid which is used to compute the force for hydrodynamics or particle-mesh simulations. In contrast to the $O(N)$ multigrid solver (MG) - an iterative method that requires multiple V-cycles through a multi-resolution hierarchy of Cartesian grids - the FMM
algorithm performs just one upward pass through the same hierarchy, during which multipole expansions are accumulated and shifted, followed by a single downward pass, in which local expansions are propagated. Numerical tests indicate that FMM attains accuracy comparable to that of MG for smooth potentials and is particularly well-suited for problems with isolated boundary conditions, since it avoids the approximate Dirichlet boundary conditions required by MG schemes. Although in theory FMM requires around 30 times more floating-point operations than MG, its higher arithmetic intensity leads to comparable performance and better scalability relative to MG.
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High Energy Physics (Theory)
RG Dynamics of Irrelevant Fermion Operators and the Drag Coupling Mechanism
Jeremias Aguilera-Damia, Diego Rodriguez-Gomez and Jorge Russo
We study the renormalization-group flow of higher-dimensional fermionic interactions $(\psi^\dagger \psi)^{2n}$ in the presence of a
Fermi surface. We show that the growth of the BCS four-
fermion coupling induces a drag mechanism whereby higher-order fermionic couplings are driven to strong coupling in the infrared. We derive the corresponding beta functions and show that the drag effect applies generically to the whole tower of fermionic operators. Remarkably, although all couplings are driven toward the same strong-coupling scale, the renormalization-group flow preserves a hierarchy in which higher-dimensional operators remain parametrically suppressed relative to the BCS interaction. We then investigate this mechanism in a $2+1$-dimensional non-
Fermi liquid coupled to a critical
boson. While higher-order fermionic interactions are similarly enhanced along the flow, we show that they do not destabilize the IR stable non-
Fermi-
liquid fixed point, present for sufficiently large $N$. We briefly discuss possible implications for multicomponent
superconductors and other strongly correlated metallic systems.
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Astrophysics of Galaxies
A novel data-driven approach to extract stellar population properties from galaxy spectra using absorption indices
Zahra Sharbaf, Ignacio Ferreras, Anna R. Gallazzi et al. (+3 more)
In an era of highly complex machine learning methods that often are informative but not straightforward to interpret, Principal Component Analysis (PCA) offers a simple, easily interpretable approach. With no fitting parameters, it extracts the most salient statistical trends in data without the need for training sets. In this paper, we explore a large range of composite
stellar population models defined for detailed analyses of
galaxy spectra from surveys. Six of the most prominent spectral indices are targeted to visualize a PCA-based latent space created by the model data. The age-
metallicity degeneracy is broken in the 3-dimensional space spanned by the first three eigenvectors, but we emphasize that non-trivial combinations of all six absorption indices are needed for this. Moreover, the last eigenvector suggests an intriguing tug of war between two Balmer indices: H$\gamma_A$ and $H\delta_A$, that can help discern the presence of recent bursting behaviour, as it exploits the different behaviour of the two indices over timescales $\sim$0.5-1 Gyr. Comparisons can be made between SDSS and LEGA-C
galaxy spectra based on the latent space created by the models. This method, based on pure data, produces excellent results in agreement with standard SPS model fitting techniques, allowing for the study of
stellar populations in a variety of surveys or observational/synthetic databases on solid ground.
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All authors Zahra Sharbaf, Ignacio Ferreras, Anna R. Gallazzi, Stefano Zibetti, Daniele Mattolini, Laura Scholz-Díaz
Lattice Field Theory
Shiyang Chen, Moxian Qian, Gert Aarts et al. (+2 more)
In
lattice field theory, target distributions are known only up to normalization, (\tilde{\pi}(\phi)\propto e^{-S(\phi)}), while the partition function is intractable. Markov chain Monte Carlo simulations often become inefficient near phase transitions or the continuum limit due to critical slowing down. In this work, we propose a novel sampler based on nonequilibrium thermodynamics, called
Stochastic Path Sampler (SPS), which can generate configurations for the unnormalized target distribution without requiring training data. The central idea of SPS is to establish a trajectory-level balance for learnable forward and backward
stochastic dynamics between two
equilibrium states, namely the prior and target distributions. This is achieved by minimizing the path-space variational free energy, equivalently an
entropy-production upper bound, defined by the log-ratio of forward and auxiliary backward trajectory measures, thereby enhancing the reversibility of the forward and backward processes. The learned forward process provides independent proposals, which are subsequently corrected by an extended-space Independence Metropolis–Hastings step. In two-dimensional (\phi^4) theory, we demonstrate that our neural sampler can achieve the same sampling quality as HMC but with a much shorter autocorrelation time in the critical region. This sampler offers a
stochastic-quantization-inspired route to data-free proposal construction for
lattice field theory by leveraging a variational free-energy principle derived from path-space irreversibility.
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All authors Shiyang Chen, Moxian Qian, Gert Aarts, Biagio Lucini, Kai Zhou
Earth and Planetary Astrophysics
COUNTESS I: A Uniformly Vetted Catalog of Known and New Transiting Exoplanets in the TESS Northern Continuous Viewing Zone
Andrew Hotnisky, Rachel B. Fernandes, Kevin K. Hardegree-Ullman et al. (+9 more)
The Transiting
Exoplanet Survey Satellite (TESS) has transformed the study of nearby exoplanetary systems; however, its nominal observing strategy limits sensitivity to
planets with orbital periods shorter than $\sim$10 days for most parts of the sky. The two TESS Continuous Viewing Zones (CVZs) provide extended temporal baselines that help overcome this limitation, enabling the detection of longer-period ($>$10 days) transiting
planets around nearby
stars. Here, we present COUNTESS, a transit-search pipeline optimized for long-baseline TESS observations that combines multi-sector light curves with heterogeneous cadences, and implements fast-folding BLS period detection, vetting, and statistical validation. As a first application of the pipeline, we conducted a search on the primary and first extended mission photometry in the TESS northern CVZ. For this analysis, we used
Gaia DR3 and 2MASS photometry to homogeneously derive a
stellar catalog of FGKM
stars for the TESS northern CVZ, resulting in a sample of 391,059
stars. We used COUNTESS to search for transiting
planets around 26,114 of these
stars with TESS-SPOC light curves and assessed its performance, recovering 115 out of 159 known TESS Objects of Interest (TOIs; $0.85\ \text{days} < P <124.72\ \text{days}$; $1.03\ R_\oplus < R_p < 16.35\ R_\oplus$). Additionally, we identified 10 new
exoplanet candidates ($1.20\ \text{days} < P <34.62\ \text{days}$; $1.73\ R_\oplus < R_p < 4.19\ R_\oplus$) that passed vetting tests, including two new statistically validated sub-Neptunes, TIC 219893931b and TIC 237254473b. COUNTESS enables extended-baseline TESS analyses and identification of longer-period
planets, establishing a foundation for future
exoplanet demographic studies, including comparisons with Kepler and K2.
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All authors Andrew Hotnisky, Rachel B. Fernandes, Kevin K. Hardegree-Ullman, Steven Giacalone, Kiersten M. Boley, Kristo Ment, Michelle Kunimoto, Galen J. Bergsten, Sakhee Bhure, Jessie L. Christiansen, Brandon Radzom, Suvrath Mahadevan
High Energy Physics (Phenomenology)
Probing New Degrees of Freedom with the Universal Tail of Primordial Black Hole Mass Functions
Kaustubh Agashe, Jae Hyeok Chang, Steven J. Clark et al. (+3 more)
The
primordial black hole (PBH) mass function today develops a low-mass evaporation tail whose shape is universal with respect to the initial PBH mass distribution. This universality is fixed by the continuity equation and the Hawking mass-loss rate, but the tail is distorted if additional particle degrees of freedom participate in Hawking evaporation. Since this tail controls high-energy PBH
photon emission, such distortions leave characteristic features in the gamma-ray spectrum. We show that these features provide a robust probe of new degrees of freedom, even for subdominant PBHs, within reach of future experiments and independent of visible-sector couplings or relic abundance.
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All authors Kaustubh Agashe, Jae Hyeok Chang, Steven J. Clark, Bhaskar Dutta, Yuhsin Tsai, Tao Xu
Astrophysics of Galaxies
Reconstructing the orbits of Milky Way dwarf galaxies: A Large Magellanic Cloud perspective
Alberto Manuel Martínez-García, Andrés del Pino, Roeland P. van der Marel et al. (+14 more)
The orbital histories of the
dwarf satellites of the Milky Way (MW) are key to understanding their
evolution and placing their present-day properties in a dynamical context. We present the results of the orbit integration of 72
dwarfs in the vicinity of the MW, based on accurate 6D phase-space coordinates from the literature and a suite of six realistic, time-evolving gravitational potentials that account for the mutual interaction of the MW and the Large Magellanic Cloud (LMC). We provide the largest catalogue of orbital parameters for MW
dwarfs to date, in terms of both
galaxy sample size and range of potentials explored. We also assess the binding status of the
dwarfs and estimate their infall times, finding that the majority of them have spent the last 5 Gyr within the MW virial radius. From the reconstructed orbits, we identify ten likely LMC satellites, several of which have experienced very close passages within the LMC
stellar disc. For the Small Magellanic Cloud (SMC), we find that its most recent pericentre about the LMC ($\sim$8 kpc, $\sim$170 Myr ago) is consistent with predictions from the direct collision scenario proposed to explain the LMC's offset and tilted bar. We also note a broad temporal coincidence between previous SMC pericentres and
star formation rate peaks reported in both Magellanic Clouds, suggesting a causal connection. Finally, we identify Grus II and Tucana IV as possible MW satellites recently captured by the LMC, based on their pronounced orbital deflections and velocities relative to the LMC.
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All authors Alberto Manuel Martínez-García, Andrés del Pino, Roeland P. van der Marel, Giuseppina Battaglia, Ewa L. Łokas, Eduardo Vitral, Kevin A. McKinnon, Laura L. Watkins, Nitya Kallivayalil, Sangmo Tony Sohn, Guillaume F. Thomas, Salvador Cardona-Barrero, Borja Anguiano, Jairo A. Alzate-Trujillo, Francisco Nogueras-Lara, Paul Bennet, Adrián Hidalgo-Pinilla
General Relativity and Quantum Cosmology
Universality in the Transition from Inspiral to Plunge for Extreme-Mass-Ratio-Inspirals: High-Accuracy Analytic Solutions and Catastrophe Theory
Ariadna Ribes Metidieri, Béatrice Bonga, Badri Krishnan et al. (+1 more)
We revisit the transition from inspiral to plunge for extreme mass-ratio inspirals on quasi-circular, inclined orbits in Kerr spacetime from the perspective of catastrophe theory. Our goal is to uncover the mathematical structures underlying the universality of the transition dynamics, which remains governed by the same Painlevé I differential equation as for equatorial inspirals despite the additional complexity. We first analyze the solution of the Painlevé I equation selected by the physical boundary conditions of slowly evolving quasi-circular inspiral at early times. We argue that these conditions uniquely select the tritronquée solution of Painlevé I. We then compare existing high-accuracy analytic approximations of the tritronquée solution with direct numerical integrations of the Painlevé I equation, finding comparable accuracy and improved stability under differentiation and integration for the analytic solution. In the second part of this work, we show that the
equilibrium structure of the Kerr radial effective potential admits a natural interpretation in terms of catastrophe theory. Equatorial orbits are associated with the fold catastrophe, while inclined orbits are described by the cusp catastrophe. In both cases, the transition to plunge corresponds to slow
evolution across fold lines of the catastrophe
manifold, providing a
geometric explanation for the universal appearance of the Painlevé I equation in the transition dynamics.
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All authors Ariadna Ribes Metidieri, Béatrice Bonga, Badri Krishnan, José Luis Jaramillo
General Relativity and Quantum Cosmology
Relativistic and Newtonian Proca Stars: A Tale of Two Limits
Alberto Diez-Tejedor, Carlos Herdeiro, Claudio Lazarte et al. (+4 more)
We investigate a representative set of static solitonic solutions of the Einstein-Proca theory in the Newtonian regime, where the field frequency approaches the particle mass, $\omega \to \mu$, and compare them with the corresponding solutions of the
spin-1 Schrödinger-Poisson system, which provides the effective description in this limit. While this correspondence is relatively straightforward in the Einstein-Klein-Gordon case, the vector nature of the Proca field, combined with the enhanced $U(3)$
symmetry of the nonrelativistic
spin-1 regime, gives rise to several nontrivial features that require careful analysis. We establish a mapping between the two descriptions by identifying $\ell=0$ electric Proca
stars with radially polarized (hedgehog) configurations and $\ell=1$ electric Proca
stars with linearly polarized configurations. We further clarify some aspects of the ground state and resolve several apparent discrepancies between relativistic and Newtonian solutions, particularly concerning their morphology and stability properties. An important conclusion of this work is that the nonrelativistic regime supports a richer spectrum of stable
equilibrium configurations than the relativistic theory, including stable excited states.
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All authors Alberto Diez-Tejedor, Carlos Herdeiro, Claudio Lazarte, Eugen Radu, Armando A. Roque, Nicolas Sanchis-Gual, Etevaldo dos Santos Costa Filho
Astrophysics of Galaxies
The host halo masses of AGNs and quasars at $z \sim 3-7$ with TNG-Cluster, FLAMINGO and other cosmological galaxy simulations
Akanksha Kapahtia, Annalisa Pillepich, Joey Braspenning et al. (+5 more)
Most observations and clustering analyses suggest that
quasars inhabit a narrow range of dark-matter
halo masses ($10^{12-13}$ M$_{\odot}$) across
cosmic time ($z\lesssim7$). Recent hydrodynamical simulations in gigaparsec-scale volumes now enable direct comparison of this picture with self-consistent
galaxy-formation models. We quantify the relation between AGN bolometric luminosity and host
halo mass before
Cosmic Noon in TNG300, TNG-Cluster, FLAMINGO L1_m8 and L2p8_m9, and in smaller-volume simulations (Illustris, EAGLE, TNG100, and Simba). For AGNs with $L^{\mathrm{AGN}}_{\mathrm{bol}} \ge 10^{42}$ erg s$^{-1}$, more massive
haloes host more luminous AGNs on average, but only up to a certain mass. The median luminosity-
halo mass relation is highly non-linear, with large scatter, and flattens (FLAMINGO) or turns over (TNG300+TNG-Cluster) at
halo mass, $M_{\mathrm{200,crit}} \gtrsim10^{12}$ M$_{\odot}$, at least at $z<5$-6. This high mass AGN quenching also manifests as a characteristic
quasar host
halo mass: in TNG300+TNG-Cluster,
quasars ($L^{\mathrm{AGN}}_{\mathrm{bol}} \sim10^{45-47}$ erg s$^{-1}$) typically reside in
haloes of mass $10^{12-12.5}$ M$_{\odot}$ at $z=3$-6, while FLAMINGO
quasars extend to median masses of $\sim10^{12.8}$ M$_{\odot}$ at $z\sim3$-4. All simulations predict substantially larger scatter in AGN luminosity at fixed
halo mass than in
halo mass at fixed luminosity (up to 3 dex versus $\lesssim1$ dex between the 5th and 95th percentiles), implying weak coupling between
halo growth and instantaneous SMBH
accretion. Consequently, simulated
quasar host masses broadly agree with observational estimates. The most luminous AGNs occupy increasingly rare
haloes at earlier epochs but typically do not reside in the most massive
haloes at any
redshift up to $z\approx7$.
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All authors Akanksha Kapahtia, Annalisa Pillepich, Joey Braspenning, Dylan Nelson, Joop Schaye, Eduardo Bañados, Silvia Belladitta, Frederick Davies
Astrophysics of Galaxies
CANUCS/Technicolor Data Release 2: A Catalogue of Galaxy Structural Parameters in up to 29 HST+JWST bands and a Multi-Wavelength Exploration of the Galaxy Size-Mass Relation at $0.6 < z \leq 4$
Maya Merchant, Lamiya A. Mowla, Georgios E. Magdis et al. (+23 more)
We present James Webb Space
Telescope (JWST) results of a morphological study of
galaxies in the CAnadian NIRISS Unbiased Cluster (CANUCS) and Technicolor surveys, observed in 19 medium- and broadband NIRCam filters in five CANUCS NIRCam Flanking Fields with rest-frame wavelength coverage between $\sim 0.2 - 3.2\mu m$. Using GALFIT, we measure the morphological parameters of $\sim$ 4,100
star-forming
galaxies at $0.6 < z \leq 4$ with
stellar masses of $8.5 < \text{log}(M_*/M_\odot) \leq 11.5$. This enables us to concurrently examine how
galaxy size varies as a function of
stellar mass,
redshift, and rest-frame wavelength to provide a novel parametrization of the
galaxy size-wavelength relation. Additionally, we analyze the
evolution of the
galaxy size-mass relation in the rest-frame optical and NIR with the introduction of wavelength as a free parameter. We report a gradient in the slope of the size-mass relation with respect to rest-frame wavelength with a critical crossover mass at $\sim 10^{9.5} M_\odot$. We propose this characteristic mass as the
stellar mass at which
galaxies transition between diffuse and compact morphologies. We concurrently present the data release of morphological measurements of the five CANUCS-Technicolor NIRCam Flanking Fields in which we provide structural parameters for $\sim$ 41,000
galaxies in up to 29 JWST+HST filters.
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All authors Maya Merchant, Lamiya A. Mowla, Georgios E. Magdis, Adam Muzzin, Chris J. Willott, Roberto Abraham, Yoshihisa Asada, Maruša Bradač, Gabriel B. Brammer, Guillaume Desprez, Kartheik G. Iyer, Nicholas S. Martis, Gaël Noirot, Gregor Rihtaršič, Marcin Sawicki, Ghassan T. E. Sarrouh, Sunna Withers, Natalie Allen, Jacqueline Antwi-Danso, Westley Brown, Jon Judež, Danilo Marchesini, Rosa M. Mérida, Katherine Myers, Luke Robbins, Visal Sok