Applied Physics
Progress in Cavitated Front Gridline Ag Paste for PERC Solar Cell Architecture
Donald Intal, Sandra Huneycutt, Abasifreke Ebong et al. (+2 more)
This paper reports on the progress made with the cavitated silver paste on passivated emitter rear contact
cells (PERC) to reduce the series resistance. Thus, electrical and microscopy characterizations are used to examine these resistive losses. Fifteen 252 cm2 PERC
cells were fabricated for this assessment. Under standard test conditions, these
cells achieved a mean conversion efficiency of 21.87% and a maximum of 22.07%. The mean measured fill factor was 79.98%, compared with a pseudo-fill factor of 83.60%, giving a mean deficit of 3.62 percentage points. Fill factor decreased with increasing area-normalized series resistance, which ranged from 0.53 to 0.83 ohm-cm2, while open-
circuit voltage and short-
circuit current remained unvaried. These electrical trends support resistive current extraction as the principal contributor to fill-factor variation. Electroluminescence imaging revealed localized emission nonuniformity. Cross-sectional scanning transmission electron microscopy showed variation in the glass interfacial layer, while scanning electron microscopy identified micrometer and sub micrometer silver particles. Conductive atomic force microscopy after sequential removal of the bulk metal and glass revealed spatially heterogeneous current response. These observations are consistent with nonuniform electrical access at the contact, where restricted conducting pathways may concentrate on current and increase local voltage drops. The combined characterization identifies interfacial heterogeneity and the connectivity of conducting pathways as priorities for understanding and reducing extraction losses in cavitated silver metallization.
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All authors Donald Intal, Sandra Huneycutt, Abasifreke Ebong, Dana Hankey, Marshall Tibbetts
Quantum Physics
Generating Superposition of Transverse Ising Ground States by Quantum Interaction
Koushik Das, Sayan Mondal and Ujjwal Sen
We investigate superpositions of
quantum Ising ground states generated through a
quantum interaction, in which the nearest-neighbor coupling strength is promoted to an operator acting on a central auxiliary
spin. We prepare the central
spin in a superposition, which allows the chain to evolve coherently under different effective interaction strengths. The states are prepared by adiabatic
evolution of the joint system comprising the central
spin and the many-body
spin chain, followed by a measurement on the central
spin and post-selection of a specific outcome. It is possible to prepare superpositions of transverse-field
quantum Ising ground states belonging to the three
magnetic phases, namely, the paramagnetic, ferromagnetic, and anti-ferromagnetic phases. For a
spin-1/2 central system, it is possible to prepare superpositions of ground states belonging to any two phases, while for the
spin-1 case, the superpositions may contain three ground states, each belonging to one of the three phases. We analytically derive expressions for the magnetization,
spin correlations, and
entanglement of such states. The magnetization and
spin correlations show distinct features in different superposition sectors. The nearest-neighbor
entanglement is largest where the transverse field and Ising interaction compete, and its behavior differs from that of the
magnetic observables. We also derive the
quantum Fisher information relevant to estimating the Ising interaction strength. And it exhibits multiple peaks near the critical points of the constituent ground states, with the maximum value showing Heisenberg scaling, for the parameters and system sizes examined.
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Atmospheric and Oceanic Physics · Cross-listed from stat.ML
Accounting for model error in ensemble variational data assimilation through learned generative dynamics
Marc Bocquet, Tobias S. Finn and Sibo Cheng
Many approaches have recently been proposed to combine data assimilation with machine learning for improved forecasts with geophysical models. Here, we focus on combining advanced sequential data assimilation schemes with a generative forecasting model which accounts for complex model errors. This generative model provides a
stochastic approximation of the conditional distribution of the successor state given the current state. The proposed variational formulation is a novel one-step weak-constraint 4D-Var scheme in which a learned conditional
stochastic forecast replaces the prescribed additive Gaussian model error representation. We derive and implement this formulation as an ensemble variational
algorithm, the generative iterative ensemble Kalman filter (IEnKF-G), which generalises the iterative ensemble Kalman filter with additive Gaussian model error (IEnKF-Q). We extend the method to a smoother with an assimilation window spanning multiple time steps and propose a simplified variant. The IEnKF-G is evaluated on a
stochastic variant of the Lorenz 1963 model to assess its robustness. It is then tested on a multi-scale variant of the one-dimensional Lorenz 1996 model, in which the resolved variables are affected by model error originating from the hidden small-scale variables. The
algorithm is then compared to an ensemble Kalman filter that adaptively mitigates model and sampling errors, and to the IEnKF-Q. The IEnKF-G is generally more accurate in the tested configurations, with substantial gains under partial observations and significant model error. This demonstrates the potential of generative data-driven models when paired with classical data assimilation methods, particularly when model error is substantial.
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Quantum Physics
Krylov Complexity and Quantum Many-body Scars in Non-Hermitian Kinetically Constrained Models
Arkaprava Sil, Rudraksh Kaushik, Souvik Kundu et al. (+2 more)
Thermalization in closed
quantum systems and its breakdown are central to understanding the emergence of statistical behavior in isolated many-body systems. Kinetic constraints can hinder thermalization by restricting the allowed dynamics and giving rise to non-ergodic behavior. While various aspects of ergodicity breaking in kinetically constrained models have been extensively studied in Hermitian systems, their behavior in non-Hermitian kinetically constrained models remains less explored. In particular, the inequivalence of left and right eigenstate ensembles in non-Hermitian systems raises the question of whether they exhibit qualitatively different dynamical and eigenstate properties. In this work, we study non-Hermitian generalizations of the paradigmatic PXP and PPXPP models, focusing on their Krylov complexity, eigenstate structure, and dynamics. By exploiting the Arnoldi's
algorithm, we find distinct behavior of Krylov complexity in the left and right eigenstate ensembles as non-Hermiticity is increased: in the right ensemble, it exhibits persistent oscillations with an increasing period, while in the left ensemble, it gradually saturates. The characteristic arch-shaped profile of the Arnoldi coefficients is also modified differently in the two ensembles, with a Hermitian-like arch re-emerging in the left ensemble at large non Hermiticity. Additionally, in the non-Hermitian PXP model, the right ensemble retains the characteristic scar structure, while the left ensemble develops additional non-scar eigenstates with anomalously low
entanglement and large overlap with the
vacuum state. These findings reveal that non-Hermiticity can affect Krylov dynamics and eigenstate structure differently in the left and right ensembles, demonstrating the need to treat them separately when characterizing non-Hermitian kinetically constrained systems.
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All authors Arkaprava Sil, Rudraksh Kaushik, Souvik Kundu, Prasant Mallik, Sudipto Singha Roy
Quantum Physics
Optical interferometric tools for probing memory effects
Saheli Mukherjee, Bivas Mallick, Samyadeb Bhattacharya et al. (+2 more)
Recent efforts to detect non-Markovian
memory have become increasingly important, motivated by the broad relevance of
memory effects in
quantum information processing, metrology, and thermodynamic engines. Here, we show that interferometric methods, particularly the phase shift and visibility, provide an experimentally accessible framework for probing environmental effects and witnessing non-Markovian dynamics. Specifically, suitably constructed witness operators enable the detection of non-Markovianity through measurable phase shifts in the interference pattern. Furthermore, we prove that the interferometric visibility is monotonically non-increasing under incoherent CP-divisible (Markovian) dynamics. Consequently, any revival of the optimized visibility constitutes a sufficient signature of information backflow and hence non-Markovianity. The effectiveness of the proposed phase-based and visibility approaches is illustrated for representative examples of non-Markovian dynamics. Our results offer a simple and experimentally feasible framework for probing
memory effects, with potential applications in
quantum sensing and noisy intermediate-scale
quantum devices.
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All authors Saheli Mukherjee, Bivas Mallick, Samyadeb Bhattacharya, Ananda G. Maity, A.S. Majumdar
Mathematical Physics · Cross-listed from math.PR
Kinetic SDEs and kinetic Fokker-Planck equations with critical Morrey-type drifts, and local blow-ups
Jean-François Jabir, Damir Kinzebulatov and Chengjun Yue
We develop a Sobolev theory for the kinetic Fokker-Planck equation subject to a singular Morrey-form $L^\infty+M^q_K$ force field which can produce local blow-ups due to strong attraction to a submanifold. Our approach is based on the fractional representation for the Duhamel series of the equation and on establishing kinetic Adams-type estimates. Accordingly, we construct weak solutions of Brownian-driven kinetic SDEs in a critical Morrey set-up, obtain kinetic Krylov-type estimates and a strongly continuous Feller propagator, and establish uniqueness criteria for a large class of weak solutions.
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Materials Science
Evidence of an anisotropic Griffiths phase in a two-dimensional van der Waals magnet
Anupam K. Singh, Dhananjay Nair, Holger Meyerheim et al. (+2 more)
Over the last decade, the emerging field of two-dimensional van der Waals magnetism has focused mainly on long-range-ordered
magnetic phases. Disordered
magnetic phases, however, remain largely unexplored. Here, we report a highly anisotropic Griffiths phase driven by self-intercalation in the van der Waals magnet Fe5GeTe2. We find evidence of short-range-ordered ferromagnetic clusters embedded in a paramagnetic
matrix, which dominate the
magnetic response between the Curie temperature and a higher characteristic Griffiths temperature. An anomalous power-law divergence in the
magnetic susceptibility, universal Lee Yang scaling, and distinct
entropy anomalies provide further evidence for this phase. Strikingly, the non-analytic Griffiths response emerges exclusively under in-plane
magnetic fields, whereas out-of-plane fields abruptly alter this behavior. This directional dependence indicates that the local
magnetic interactions within nanoscale clusters are closely coupled to the layered
lattice geometry. Our findings establish a regime of dimensionally constrained, disorder-driven magnetism and identify self-intercalated van der Waals magnets as a platform for investigating the interplay between
magnetic disorder, anisotropy, and reduced dimensionality.
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All authors Anupam K. Singh, Dhananjay Nair, Holger Meyerheim, Stuart S. P. Parkin, Banabir Pal
Mathematical Physics · Cross-listed from math.CT
Models for dagger $(\infty,1)$-categories III: Univalent flagged dagger $(\infty,1)$-categories and unitarily complete dagger Segal anima
Keima Akasaka
We identify the $(\infty,1)$-category presented by the dagger Bergner, dagger Joyal, and dagger Rezk models of Parts I and II with that of univalent flagged dagger $(\infty,1)$-categories. We first construct a realization–nerve adjunction between reversal simplicial anima and Hermitian flags. We prove that its nerve restricts to an equivalence between flagged dagger $(\infty,1)$-categories and dagger Segal anima, under which univalence corresponds to
unitary completeness. We then construct the adjunctions for univalentization and Hermitian completion and identify univalentization with
unitary completion.
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Quantum Physics
Ghost unitaries for loss-resilient photonic resource-state generation
Kevin J. Randles, Manuel H. Muñoz-Arias and Kevin Thompson
Entangled few-
photon states, such as Bell and Greenberger-Horne-Zeilinger (GHZ) states, are central resources for discrete-variable photonic
quantum information processing. In many architectures, these states are generated probabilistically by first heralding single
photons from biphoton sources and then interfering them in linear-optical
circuits. In this work, we show that the
entanglement structure of said biphoton sources can be directly exploited for noise-engineering to deliver higher quality resource states. Using the transpose identity of multi-mode squeezed
vacuum states, we introduce "ghost-
unitary" implementations in which the target resource-generation interferometer is applied to the heralding modes rather than to the delivered resource modes. When the dominant imperfection is interferometric loss, this relocation converts direct amplitude damping of the output into false-positive heralding events that require both higher-pair emission and
photon loss. In the low-squeezing regime, these events are parametrically suppressed, yielding higher-fidelity conditional resource states. We analyze this mechanism for single-
qubit states, two-
photon NOON states, Bell states, and a family of $n$-
qubit GHZ states, as well as for single-
qubit teleportation and type-I-fusion-based resource growth. Across these examples, we delineate finite parameter regimes in which ghost-
unitary implementations outperform direct implementations, with particular relevance to frequency-bin photonics where active linear-optical transformations can be relatively lossy. We also prove that, in the setting considered here, the direct implementation of the $n$-GHZ family delivers identically damped outputs: equivalent to the ideal state followed by uniform amplitude damping. This extends the known $n=2,3$ cases and provides a structural result of independent interest for photonic
quantum information processing.
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Strongly Correlated Electrons
Quantum skyrmion molecule: two quantum skyrmions bound by coherent magnon exchange
Ricardo L. Silva
Quantum skyrmions in frustrated
spin-$1/2$ magnets are bound states of a few flipped
spins in a ferromagnetic background. Using exact diagonalization and density-
matrix renormalization group calculations for the $J_1$–$J_2$ triangular-
lattice model with easy-axis anisotropy $K$, we ask what happens when two such objects are brought together. The binding energy per flipped
spin of a single skyrmion has a minimum at $\Nf^{*}=7$ for $K=0.02$–$0.04$, and skyrmions smaller than $\Nf^{*}$ do not exist as pairs: at any distance they coalesce into a single larger object, and pinning wells cannot prevent it. Two skyrmions of natural size, by contrast, form a bound molecule without pinning or external field, with binding energy $U\simeq-0.007J_1$ at $K=0.03$–$0.04$ and an
equilibrium separation of $5.5$
lattice spacings that does not depend on $K$ or on the size of the simulation domain; at $K=0.02$, where the single skyrmion is itself marginally bound, the pair is unbound within our resolution. The two constituents keep their identity ($7+7$ flipped
spins) and are coupled by a coherent exchange of
magnons, visible as number fluctuations between the two halves of the domain in excess of those of two independent skyrmions and as in-plane
spin correlations between the two skyrmion walls that reach $0.16$ across the gap. These correlations follow the
vortex pattern of the two textures and lock their relative helicity, the
quantum counterpart of the helicity-dependent interaction of classical skyrmions. We discuss the molecule as a self-assembled two-
qubit element for skyrmion helicity
qubits in a single layer.
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Chemical Physics
Chromatographic Peak Shape beyond the High-Péclet Approximation: Analytic Time-Domain Expression and Derivatives
Hernán R. Sánchez
Analytic time-domain expressions for the elution-time density and its parameter derivatives were recently derived from a
stochastic model of linear isocratic chromatography incorporating advective-diffusive transport, injection dispersion, and fast and slow retention mechanisms. A Gaussian approximation, justified asymptotically at high column-scale Péclet numbers, was adopted for the distribution of the combined mobile-phase and fast-retention time, while slow retention was incorporated through a series of Gaussian-Gamma convolutions. Here, the underlying normal-inverse-Gaussian density is approximated by a finite Gaussian mixture using an existing quadrature rule. The elution-time PDF is a weighted sum of series of the previously derived Gaussian-Gamma form. Its parameter derivatives are also obtained. Newly derived recurrences reduce the cost of evaluating the coefficients of that series and their derivatives from quadratic to linear in truncation order for a fixed number of mechanisms. Through a probabilistic analysis of the series coefficients, the required number of terms is found to be small enough for rapid evaluation under usual chromatographic conditions. A relative roundoff-error
estimator is derived to quantify finite-precision loss in the inherited forward recurrence for Gaussian-Gamma convolutions. For the cancellation-prone regime, a backward reconstruction is developed, initialized from an exact ratio of consecutive Gaussian-Gamma terms expressed through parabolic-cylinder functions. A highly accurate approximation is derived for rapid evaluation of this ratio. Independent high-precision calculations confirm the high accuracy of the resulting double-precision evaluation in the tested numerical case.
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Accelerator Physics
HOM Mitigation
Nicoleta Baboi
Higher Order Modes (HOMs) in accelerating structures are resonant electromagnetic fields excited and left behind by charged particle bunches. They can severely degrade the beam quality in accelerators, such as the multi-bunch energy spread and transverse emittance, and therefore one must carefully study and mitigate them. In this lecture, various methods of HOM mitigation are reviewed. On one hand, one tries to avoid their existence, for example by careful design of the accelerating structures and damping systems. On the other hand, one can reduce the effect of the excited HOM fields, for example by means of fast feedbacks or beam
alignment. Additionally, a few ways to make HOM signals useful are referred to, such as diagnostics of the beam or of accelerating structures.
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Strongly Correlated Electrons
Phase-Coherent Spin and Lattice Modulations in a Y-type Hexaferrite
Oskar Stepančić, Annika Stellhorn, Emma Campillo et al. (+7 more)
Spin-driven multiferroics owe their electric polarization to
lattice distortions that follow the
magnetic order, yet in incommensurate magnets
symmetry normally forbids such a distortion at the fundamental
magnetic wavevector, and the distortions themselves are rarely observed. Here we use half-polarized
neutron scattering to show that the Y-type hexaferrite Ba$_{0.4}$Sr$_{1.6}$Mg$_2$Fe$_{12}$O$_{22}$ hosts, in its saturated high-field state, a
magnetic modulation and a longitudinal
lattice modulation at one and the same wavevector, locked in phase. The signature is a large nuclear-
magnetic interference asymmetry, $r$ ~ 0.8, of the same sign at the two conjugate satellites and persisting to 275 K. The zone contrast and the field dependence of the satellite indicate an internal, field-induced longitudinal distortion. The modulated state coexists with the transverse-conical magnetoelectric phase and outlives it, revealing a fundamental-wavevector
spin-
lattice coupling in a
magnetic field regime previously regarded as a simple ferrimagnet.
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All authors Oskar Stepančić, Annika Stellhorn, Emma Campillo, Kun Zhai, Niklas Ekström, A. Corani, D. Alba Venero, R. Cubitt, E. Blackburn, L. Shen
Instrumentation and Methods for Astrophysics
Graph Learning with Multiplicative Aggregation for Solar Filament Fragment Association Modeling in Full-disk H$\alpha$ Images
GaoFei Zhu, GangHua Lin, Xiao Yang et al. (+4 more)
Solar filaments are prominent features in H$\alpha$ observations. During their
evolution, they often exhibit complex morphological and topological changes, which, due to line-of-sight projection effects, appear as fragmentation and merging. These phenomena make it difficult to reliably track solar filaments using automated methods, as the same structure may appear different over time. To address this issue, we formulate filament fragment association as a graph-based learning problem, where individual fragments are represented as nodes and candidate pairwise relationships are modeled as edges to infer whether fragments belong to the same filament. Furthermore, we propose a novel graph neural network (GNN) that incorporates multiplicative aggregation layers to enhance feature aggregation in the graph, replacing conventional additive aggregation with a multiplicative mechanism to better capture information between fragments. Experimental results demonstrate that the proposed method achieves reliable performance in filament fragment association, validating the effectiveness of the graph-based formulation and the proposed multiplicative aggregation mechanism.
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All authors GaoFei Zhu, GangHua Lin, Xiao Yang, Suo Liu, Yu Liu, ZhiSheng Gao, Cheng Zeng
High Energy Physics (Phenomenology)
Lepton Flavour Universality in Semileptonic $\bar B_{(s)} \to D_{(s)}^{(\ast)}$ Transitions
Yu-Chen Hu, Cong-Cong Ye, Craig D. Roberts et al. (+1 more)
Using continuum Schwinger function methods, we deliver parameter-free pointwise predictions for the complete set of twelve Standard Model (SM) $\bar B_{(s)} \to D_{(s)}^{(\ast)}$, i.e., $b\to c$, semileptonic transition form factors on the entire kinematically accessible domain. Therewith, we calculate SM theory values for the decay-rate ratios of $\tau$ and $\mu$ final states: $\{ R(D) \, , \, R(D)^\ast \} = \{ 0.290(11) \, , \, 0.267(5) \}$, $\{ R(D_{s}) \, , \, R(D_{s}^{\ast}) \} = \{ 0.283(11) \, , \, 0.251(5) \}$. The former is consistent with an existing average of SM estimates, but disagrees with the experimental average by $2.8\sigma$. Comparing transitions with light
quark and strange
quark spectators, we find a $2.3\sigma$ signal for violation of SU$(3)$ flavour
symmetry, expressed at the 5% level in $D_{(s)}^\ast$ final states. It is induced by
Higgs boson couplings into the strong interaction and modulated by phenomena deriving from emergent features of the strong interaction.
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All authors Yu-Chen Hu, Cong-Cong Ye, Craig D. Roberts, Zhao-Qian Yao
Quantum Physics
Quantum Cryptography and Autoformalization in Lean
Maor Ben Shahar, Jonathan Morag, Dirk Englund et al. (+1 more)
Quantum key distribution provides secure communication by relying on physics principles and mathematical
reasoning. Security proofs across the field can contain gaps, often between individually valid
theorems integrated under mismatched assumptions. We produce an end-to-end security
theorem formalized in the Lean proof assistant, eliminating hidden hypotheses by building only on Lean's standard axioms. Our proof covers composable security of the
entanglement-based
qubit BB84 protocol against coherent attacks by the postselection technique, accounting for finite block size, and is written in a
language that enforces local operations and classical communication to help ensure a faithful representation of the protocol. The proof itself was enabled by LLM-based autoformalization, and with the proof complete, we used the same pipeline as a discovery machine, reducing the finite-size penalty on the key rate. Our work sets a reproducible standard for security arguments in
quantum cryptography and shows how formal proof engines can accelerate discovery across
quantum information science.
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All authors Maor Ben Shahar, Jonathan Morag, Dirk Englund, Kfir Sulimany
Earth and Planetary Astrophysics
DEMOS. II. What the full Lupus demographics truly tell us about protoplanetary disc evolution
Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato et al. (+7 more)
Assessing whether disc
evolution is driven by viscosity or MHD winds is crucial to determine the conditions in which
planets form. The rich statistical information encoded in nearby
star-forming regions provides an excellent opportunity to probe disc
evolution. In this paper, we apply the
Bayesian inference tool DEMOS, designed to exploit the statistical properties of disc populations and infer initial conditions and model parameters, to the Lupus disc population. We consider the observed distributions of stellar mass $M_\star$, disc mass $M$ (from continuum flux), mass
accretion rate $\dot{M}$ and CO disc size $R_{90%, CO}$. We constrain all parameters for both the viscous model, with internal photoevaporation, and the MHD winds model, with unprecedented precision. The inferred initial conditions suggest that positive correlations between initial disc properties and $M_\star$ must be present. Both models yield a typical $R_0$ of $3-5$ au for a disc around a $0.3\ \text{M}_\odot$
star, with positive stellar-mass dependence. We infer $\alpha$ (or $\alpha_\text{DW}$) of $3-4 \times 10^{-4}$ for discs around $0.3\ \text{M}_\odot$
stars, with an approximately quadratic dependence on $M_\star$. For the viscous-photoevaporative model, the typical wind mass-loss rate is $\dot{M}_\text{w} \sim 10^{-9}$ M$_\odot$ yr$^{-1}$, scaling with $M_\star$ with an exponent of $\sim 2.5$. The inferred mean age is 1.6 Myr for the MHD winds model and 0.9 Myr for the viscous-photoevaporative model. Despite a slight preference for the latter,
Bayesian evidence shows that both models reproduce the data comparably well, and neither can be ruled out. However, their best-fit synthetic populations predict substantially different evolutionary pathways. Applying DEMOS to multiple populations, especially evolved ones like Upper Scorpius, will allow to place stronger constraints on disc
evolution mechanisms.
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All authors Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato, Alice Somigliana, Benoît Tabone, Rossella Anania, Carlo F. Manara, Leonardo Testi, Claudia Toci, Francesco Zagaria
High Energy Astrophysical Phenomena
Discovery of 51 pulsars in a reanalysis of the Green Bank North Celestial Cap Survey and a revised pulsar census
R. Sengar, L. Vleeschower, D. L. Kaplan et al. (+13 more)
We present results from a reanalysis of the Green Bank North Celestial Cap (GBNCC) survey, conducted at 350 MHz with the Green Bank
Telescope between 2009 and 2020, covering the sky with declinations $\delta>-40^\circ$. We searched the survey data using an FFT-based periodicity search, with candidate selection extending to very low spectral signal-to-noise ratios and summing up to 32 harmonics. From the 60 promising candidates identified in this search, we confirmed 51 new
pulsars using the Green bank and CHIME. We also used a direct folding search method (DFSM) to search for slow
pulsars between 500 ms and 10 s. Of the 51
pulsars identified in the FFT search, 43 fall within this period range, all of which were found by the DFSM. The DFSM also found an additional
pulsar that had been missed during the inspection of the FFT candidates. Most of the new discoveries are canonical
pulsars, with
spin periods ranging from 299 ms to 4.4 s and dispersion measures from 10 to 192 $\rm pc \, cm^{-3}$. We also found a binary millisecond
pulsar with a
spin period of 3.2 ms in a 4.5-d orbit. We redetected 855
pulsars in the data, 825 of which were found in the FFT search. Within the effective parameter space of our periodicity search, the FFT search recovered $\sim$98 % of the known
pulsars within the survey sensitivity limits. After accounting for previously reported
pulsars whose observations were not processed or whose parameters lay outside our search range, the updated GBNCC census now includes 964
pulsars.
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All authors R. Sengar, L. Vleeschower, D. L. Kaplan, G. Y. Agazie, M. Bailes, A. Cassity, H. T. Cromartie, M. E. Decesar, T. Dolch, W. Fiore, E. Fonseca, R. S. Lynch, E. Parent, S. M. Ransom, I. H. Stairs, J. van Leeuwen
General Relativity and Quantum Cosmology
Null-Energy Bounds on Photon-Orbit Instability in Einstein-Gauss-Bonnet Gravity
Sarandas A., C. Fairoos and C. L. Ahmed Rizwan
We derive a local upper bound on the coordinate-time Lyapunov exponent of unstable circular null orbits in static, spherically symmetric, asymptotically flat Einstein–Gauss–Bonnet
gravity in $n\geq5$ dimensions with nonnegative Gauss–Bonnet coupling. On the regular Einstein branch, the tangential null energy condition suffices; no additional density-pressure inequality is required for the principal result. The bound retains the local matter-density contribution dictated by the field equations. Using the spherical mass relation, we express the departure of its dimensionless coefficient from the Einstein value $n-3$ in terms of the difference between the local density and the enclosed generalized Misner–Sharp mass per areal volume. This gives a sufficient density-contrast criterion for the Einstein optical bound to remain valid at nonzero coupling. Optical Gaussian
curvature and tangential null convergence provide geometrical interpretations that distinguish radial tidal instability from the focusing of a null congruence.
Vacuum solutions saturate the bound, while a Maxwell field with nonzero charge produces a strictly positive gap. The smooth Einstein limit and explicit
vacuum and charged solutions provide consistency checks. A separate matter condition yields a density-free corollary. We also discuss consequences for strong-deflection
lensing and test-field eikonal damping within their respective regimes of validity.
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High Energy Physics (Theory)
Gauge-Invariant Brout–Englert–Higgs Mechanism without Spontaneous Breaking of Local Gauge Symmetry: A Quantum-Reference-Frame Formulation
Kei-Ichi Kondo
The Brout–Englert–
Higgs (BEH) mechanism can be formulated in gauge-invariant relational terms without assigning physical spontaneous breaking to a local gauge redundancy. We treat the gauge orientation of the
Higgs field as dynamical internal reference data and describe the gauge connection relative to this
Higgs frame. On a regular patch where the frame exists, the
Higgs kinetic term induces a positive-semidefinite mass-squared quadratic form on the gauge-orbit directions and reproduces the standard tree-level vector masses. A complete
Higgs frame yields a gauge-invariant relational connection, whereas a partial frame is defined only up to a stabilizer group $H$ and produces
Higgs stiffness only along the coset directions $G/H$. In
quantum field theory the normalized frame and relational connection are nonpolynomial composite variables; physical masses are therefore characterized through suitably renormalized gauge-invariant composite correlators, or through fully dressed operators in residual-charged sectors. Applying this construction to the electroweak theory, we show that the
Higgs frame relationalizes the $SU(2)_L$ redundancy while leaving a residual electromagnetic $U(1)_{\rm em}$ Gauss law: $W^\pm$ and charged fermionic modes require electromagnetic dressing, whereas neutral channels admit local gauge-invariant interpolators. This formulation connects
Higgs dressings, FMS composites, and internal
quantum-reference-frame
language while keeping local mass generation distinct from global
symmetry realization and topological obstructions.
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High Energy Physics (Phenomenology)
Felix Kling, Toni Mäkelä, Sebastian Trojanowski et al. (+1 more)
Muon colliders are exceptionally intense sources of multi-TeV
neutrinos, allowing even relatively small detectors to record large rates of
neutrino interactions. In addition to serving as
neutrino-ion
collider for precision measurements of
neutrino deep inelastic scattering, this setup allow to study even rare
neutrino processes with at high statistics. In this study, we investigate the feasibility of measuring
neutrino trident and on-shell W-
boson production, predicting over one million trident events and one hundred thousand W-
boson events in a 100 kg silicon-based active target over ten years and allowing to detect these processes for the first time. We further show that these measurements could constrain new vector and axial-vector interactions beyond projected DUNE sensitivities and provide unprecedented constraints on the high-x
photon distribution through W-
boson production near threshold. We also discuss strategies for signal-background discrimination and the resulting detector requirements.
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All authors Felix Kling, Toni Mäkelä, Sebastian Trojanowski, Bei Zhou
High Energy Physics (Theory)
Love at First Loop: Quantum Deformability of Near-Extremal Black Holes
Pablo A. Cano, Marina David, Roberto Emparan et al. (+1 more)
The static Love numbers of black holes vanish in classical, four-dimensional, asymptotically flat General Relativity. We study how this changes for the response of near-extremal Reissner–Nordström black holes to a minimally coupled massless scalar, at energies where the Schwarzian mode of the near-horizon throat fluctuates strongly. The black hole then responds as a
quantum system with a spectrum of states. Its static response is a polarizability, given by virtual transitions between them. For $\ell=0$ the static Love number vanishes, by the shift
symmetry of the scalar, but for multipoles $\ell\geq1$ the static Love numbers are nonzero: the finite rotational energy of the
spin-$\ell$ intermediate states spoils the cancellation responsible for the classical result. Since the throat no longer has a classical geometry from which to read off a tidal response, we define it through the retarded Green's function, and compute its full frequency dependence at leading order in $r_+\omega$. Its conservative part requires renormalization: the near-horizon theory fixes the coefficient of its logarithm, and with it a dependence on the energy that no local term can remove, while its finite local terms are matching data of the four-dimensional theory. The dissipative part is finite and scheme independent. For $\ell\geq1$, it vanishes at low frequencies when the energy is below the rotational gap, while at the gap threshold it becomes non-analytic in frequency and produces a late-time $t^{-3/2}$ tail.
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All authors Pablo A. Cano, Marina David, Roberto Emparan, Stefano Trezzi
Mesoscale and Nanoscale Physics
Turning a superconducting diode into a Feynman ratchet to realize a nanoscale heat engine
Konstantinos Kontogeorgiou, İnanç Adagideli, Géraldine Haack et al. (+1 more)
Feynman's ratchet illustrates how work can be extracted from thermal fluctuations in the presence of two heat baths at different temperatures. While some experimental realizations of the ratchet effect have been studied, most lack miniaturization, which is important for some applications. Here, we propose a physical implementation of Feynman's ratchet based on Josephson junctions exhibiting the superconducting diode effect. This setup functions as a heat engine that generates work solely from a temperature gradient via thermal fluctuations. We analyze its output power and efficiency, and, through the Seebeck coefficient, identify the conditions under which the device operates in reverse, functioning instead as a Peltier cooler.
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All authors Konstantinos Kontogeorgiou, İnanç Adagideli, Géraldine Haack, Fabian Hassler
Astrophysics of Galaxies
Physical characteristics of the Galaxy defining the oscillation period of librating orbits near the OLR of the bar
A. M. Melnik and E. N. Podzolkova
We studied librating orbits of
stars near the Outer Lindblad Resonance (OLR) of the bar using the angle-action variables of
Hamiltonian dynamics. The librating orbits change the direction of their elongation relative to the major axis of the bar in a limited range of angles. To calculate orbits, we used the model of the
Galaxy with an analytical bar which reproduces well the distributions of the observed stellar velocities along the Galactocentric distance R derived from the Gaia DR3 data. We compared the values of the orbital oscillation period of a typical
star obtained from the theory and with the use of numerical simulation. Both values were found to be in good agreement and are equal to 2.0 Gyr. It was shown that the change in the average orbital radius, <R>, of a
star, calculated over the time interval of one radial oscillation, is regulated by the change in the direction of orbital elongation. As the orbit is tilted relative to the minor axis of the bar in the sense of Galactic rotation, the angular momentum of the
star, L, decreases, on average, causing a decrease in <R>. As the orbit is tilted in the opposite direction, <L> and <R> increase. We derived a general formula for the oscillation frequency, omega, of orbits captured by libration near the OLR of the bar. It turned out that the ratio of the frequency of orbit oscillations to the epicyclic frequency, omega/kappa, is determined by the parameters q_R and <p>, where the factor q_R is the ratio of the amplitude of the radial force generated by the bar to the average radial force produced by the entire
galaxy at the distance of the OLR, and the parameter <p> characterizes the average elongation of orbits captured by libration near the OLR.
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Earth and Planetary Astrophysics
DEMOS I. A Bayesian inference framework to constrain disc evolution from observed demographics
Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato et al. (+3 more)
The mechanism driving the
evolution and dispersal of protoplanetary discs has a substantial impact on the theories of
planet formation. To date, neither the viscous paradigm nor the MHD wind-driven framework have been ruled out by the observations. The statistical richness of the observed samples provides a unique opportunity to test evolutionary models through population synthesis. However, comparisons between models and observations are normally carried out by eye, and a more statistically rigorous approach has not yet been implemented. We present DEMOS, a
Bayesian inference tool that aims to infer the model parameters and initial conditions that best reproduce the full distribution of global properties of disc populations. This framework relies on a comparison between observations and synthetic populations generated with the 1D disc population-synthesis code Diskpop. We tested the tool with both the MHD wind model and the viscous framework with internal photoevaporation. Applying DEMOS to synthetic populations, we find that, for both models, it accurately recovers the model parameters of disc populations and their associated uncertainties, including cases in which initial conditions are correlated with the stellar mass. In the optimal scenario in which disc masses,
accretion rates and disc sizes are available, the tool can also constrain the angular-momentum transport parameter. We show that, although parameter estimates are the most precise with samples of about 100 discs, the tool also yields meaningful constraints for smaller populations of 10-30 discs. We further find that the predictions obtained with DEMOS closely align with those found by previous works. We anticipate that DEMOS will be a valuable tool to infer the initial conditions of observed disc populations, to design observational programmes, and to assess which evolutionary model best reproduces the data.
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All authors Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato, Benoît Tabone, Alice Somigliana, Leonardo Testi
Solar and Stellar Astrophysics
An upper limit on Galactic OB+black hole binaries from SDSS-V
J. Müller-Horn, H.-W. Rix, S. Shahaf et al. (+14 more)
Binaries composed of a luminous OB
star and a black hole (BH) are a key evolutionary link between massive stellar binaries and merging compact-object binaries, but only a handful are known and their occurrence fraction remains poorly constrained. We use multi-epoch spectroscopy from the SDSS-V Milky Way Mapper to place a first rigorous empirical upper limit on the fraction of Galactic massive ($\geq 10\,\mathrm{M}_\odot$) OB
stars with a close BH companion, $f_\mathrm{BH}$. Radial-velocity (RV) variability alone cannot distinguish BH companions from the far more numerous luminous binaries. We therefore combine the SDSS-V RV variability measurements of 3130 massive OB
stars with high-resolution follow-up and literature information to identify luminous companions among the RV-variable subset. Forward-modelling the detectability of OB+BH systems using BH masses and orbital parameters from binary-
evolution models, we find $f_\mathrm{BH} \lesssim 3\%$ at 95% credibility. This empirical upper limit approaches, but does not exclude, theoretical predictions for the OB+BH fraction. The constraint is primarily limited by the number of RV-variable systems that can be decisively classified, highlighting the importance of complete, high-quality follow-up for future searches.
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All authors J. Müller-Horn, H.-W. Rix, S. Shahaf, B. Pennell, E. Zari, M.C. Ramírez-Tannus, A. Farah, R. Essick, J.I. Villaseñor, M.R. Blanton, J.G. Fernández-Trincado, J.A. Kollmeier, C. Lam, K. Maltsev, A. Roman-Lopes, D.P. Schneider, A. Tkachenko
High Energy Astrophysical Phenomena
Scaling Up: A Global Optical/X-ray Correlation For Reprocessing Across Black Hole Masses
Changhyun Cho, David M. Russell, Aaryan Sharma et al. (+9 more)
This study extends the optical/X-ray correlation from black hole low-mass X-ray binaries (XRBs) to active galactic
nuclei (AGN), bridging scales from stellar-mass to supermassive black holes (SMBHs). In XRBs, optical emission predominantly originates from the thermal reprocessing of high-energy
photons on the surface of the geometrically thin, optically thick
accretion disk. The reprocessed optical luminosity follows a power-law relation of the form $L_{V} \propto L_{X}^{\beta} a$, with $\beta \sim 0.5$, where $L_X$ is the X-ray luminosity and the orbital separation $a$ serves as a proxy for the disk size. To test the universality of this relationship across all mass scales, we analyzed quasi-simultaneous X-ray and optical flux data from a sample of XRBs and AGN that have estimates of the radius of the optically emitting disk. To bridge the structural differences between these populations, we utilized the characteristic optical/X-ray time lag derived from reverberation mapping as a physical proxy for the reprocessing radius. Our analysis reveals a tight, global correlation across all black hole masses, described by $\log L_V = 0.48\log L_X + 0.96\log a_R + 6.5$ with a scatter of $\sim 0.20$ dex, where $a_R$ is the reprocessing radius derived from the lag. Incorporating a
geometric correction for the disk inclination angle ($\cos i$) slightly reduces this scatter to $0.18$ dex. These results suggest that X-ray reprocessing is scale-invariant across
accretion disks, from stellar-mass black holes to SMBHs. This scaling relation provides new constraints for models of X-ray emission regions in accreting black holes.
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All authors Changhyun Cho, David M. Russell, Aaryan Sharma, Payaswini Saikia, Maria Cristina Baglio, Kevin Alabarta, Sandeep K. Rout, Yi-Jung Yang, Eleonora Caruso, Mokhine Motsoaledi, Meriana Allah, Ian M. McHardy
High Energy Astrophysical Phenomena
Radio and Gamma-Ray Timing of a Newly Discovered Millisecond Pulsar
L. Vleeschower, R. Sengar, L. Nieder et al. (+17 more)
We report the discovery and timing of PSR J2147-3604, a fully recycled millisecond
pulsar with a
spin period of 3.2 ms, discovered in a reprocessing of the 350-MHz Green Bank North Celestial Cap (GBNCC) survey and later serendipitously confirmed by the MeerKAT TRAPUM UHF survey of Fermi-LAT unidentified sources. We followed up this
pulsar with Murriyang/Parkes
radio telescope and obtained a phase-connected timing solution spanning one year, revealing a 4.5-day binary orbit with very low eccentricity (e ~ 1.9 x $10^{-5}$). A follow-up search in LAT data revealed gamma-ray pulsations, allowing for a joint
radio and gamma-ray timing analysis. Assuming a
neutron-
star mass of 1.5 Msun, the inferred median companion mass (~0.2 Msun) is consistent with a helium white dwarf. The
pulsar has a low dispersion measure of 17.0 pc cm$^{-3}$ and shows strong scintillation, leading to it being detected in ~72% of the observations covering the 704-1174 MHz band with Murriyang. The
pulsar has a narrow duty cycle of ~6.5%, which leads to individual time of arrival (ToA) uncertainties of ~4.5 us for a 10 min integration with MeerKAT, suggesting this
pulsar is well suited for inclusion in PTA experiments.
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All authors L. Vleeschower, R. Sengar, L. Nieder, C. J. Clark, D. L. Kaplan, A. Anumarlapudi, R. Girgaonkar, T. Thongmeearkom, G. Y. Agazie, M. Bailes, E. D. Barr, R. P. Breton, M. E. Decesar, T. Dolch, M. Kramer, R. S. Lynch, E. Parent, S. M. Ransom, B. W. Stappers, J. van Leeuwen
Mathematical Physics
Willis-type thermal homogenization for particulate composites under harmonic heat transfer
Chunlin Wu, Ning Ding and Huiming Yin
This paper develops a Willis-type thermal homogenization framework for two-dimensional particulate composites under harmonic heat transfer and establishes a unique effective constitutive relation without introducing residual fields. The local thermal fields are obtained using the dual-reciprocity inclusion-based boundary element method, in which two eigen-fields are introduced to simulate the mismatches in thermal conductivity and heat capacity. Instead of retrieving effective kernels from several independent macroscopic solutions generated by residual fields, the complete constitutive operator is constructed upon relations between eigen-fields and generalized macroscopic responses. The effective constitutive relations are validated against a one-dimensional analytical solution and an extended
Fourier-series homogenization scheme. The
Fourier formulae further establish the opposite-wavenumber reciprocity relations between two coupling tensors and reflection-
symmetry parity relations, which explain when transverse coupling components vanish and the sign reversal of off-diagonal conductivity components under reflection. Numerical results further demonstrate that the de-phased average is required to extract physically consistent effective thermal properties under the Bloch conditions, and reveal their nonlocal frequency/wavenumber-dependent behavior. The framework provides a general computational method for Willis-type homogenization of particulate composites and is extendable to three-dimensional, multiphysical problems.
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Chemical Physics · Cross-listed from cs.LG
MIRRA: Fast, High-Fidelity Molecular Generation with Chemistry-Informed Discrete Flow Matching
Ge Sun and Juan J. de Pablo
Fast, high-fidelity molecular generation requires accurate chemical choices and efficient sampling. Chemical building blocks reduce graph size, but make each node a choice among tens of thousands of related identities. We introduce MIRRA (Molecular Identity Representation, Refresh and Assembly), a discrete flow-matching generator that learns from chemical knowledge and evaluates identity probabilities only when needed, while keeping every identity in its vocabulary available. Chemical features share information across related blocks, and learned identity corrections distinguish them in molecular context. By deciding which positions will refresh before computing their probabilities, the sampler avoids unused predictions while preserving each sampling transition. Against the strongest baselines in each task, MIRRA reduces chemical and graph distribution errors on ZINC250k by 29-31% and 53-60%, respectively, with generation up to 8.6 times faster. Property targeting yields an estimated 7.8-20.8 times more distinct novel hits per second. On a held-out
polymer test set, MIRRA achieves 100% periodic validity with known chain
topology, versus 57.0% for a
polymer variational autoencoder. These results demonstrate fast, high-fidelity generation with the full chemical vocabulary available throughout sampling.
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