Soft Condensed Matter
Quantifying nanoparticle size effect on the photoacoustic generation efficiency
Arthur Billon, Sarah Boumati, Lorenzo Mancini et al. (+9 more)
Photoacoustic (PA) signal generation in colloidal suspensions of optically absorbing nanoparticles is dominated by the thermal expansion of water for gold nanoparticles, but remains mostly unexplored for organic nanoparticles. Here, we derive a model where the PA generation efficiency scales with particle size and thermoelastic contrast with water. The model is validated using solid lipid nanoparticles labeled with several BODIPY dyes. This experimental validation paves the way for quantitative PA characterization of nanomaterials and rational design of PA contrast
agents.
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All authors Arthur Billon, Sarah Boumati, Lorenzo Mancini, Charaf Eddine Benaddi, Elise Michel, Clément Linger, Colin Schotté, Rachel Méallet, Frédéric Gobeaux, Gilles Clavier, Nicolas Tsapis, Jérôme Gateau
Computational Physics
Scale-Bridging Phase-Field Modeling of Microstructure Evolution by FE$^2$ Computational Homogenization
Geralf Hütter, Fenil Lathiya, Vincent von Oertzen et al. (+1 more)
Phase-field models have become a standard tool for simulating complex microstructure
evolution in materials, but their application to engineering-scale components is often hindered by prohibitive computational costs arising from the need to resolve fine-scale features. To address this challenge, we propose a consistent homogenization framework for phase-field theory. By enforcing a Hill-Mandel-type condition of micro-homogeneity formulated in terms of Gurtin's microforces, a well-posed boundary value problem is derived for the representative volume element (RVE), establishing rigorous micro-macro relations for both the order parameter and its gradient. The theory is implemented within a computational two-scale (FE$^2$) scheme and validated against direct numerical simulations. Two distinct examples are investigated: a minimal Allen-Cahn model and a mechanically-coupled model for stress-driven martensitic phase transformation. The results demonstrate that the proposed framework can reliably predict the spatial and temporal
evolution of the macroscopically averaged fields with reasonable accuracy.
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All authors Geralf Hütter, Fenil Lathiya, Vincent von Oertzen, Bjoern Kiefer
High Energy Physics (Phenomenology)
Fully-beauty tensor tetraquark
S. S. Agaev, K. Azizi and H. Sundu
Parameters of the fully-beauty tensor tetraquark $T=bb\overline{b}\overline{b }$ are computed using QCD sum rule method. The mass $m$ and coupling $ \Lambda $ of this state are evaluated by means of two-point sum rule approach. Prediction $m=(18530 \pm 86)~\mathrm{MeV}$ for the mass demonstrates that $T$ is stable against decays to pairs of $\eta_b \eta_b$ and $\Upsilon \Upsilon$
mesons. But it transforms to conventional particles due to $\overline{b}b$ annihilations to light
quarks $\overline{q} q $ and $ \overline{s}s$ followed by creation of
mesons $B^{(\ast)+}B^{( \ast)-}$, $ B^{(\ast)0}\overline{B}^{(\ast)0}$ and $B_s^{(\ast)0}\overline{B} _s^{(\ast)0}$. Partial width of these decay channels are calculated by invoking technical tools of three-point sum rule method. The latter allows us to estimate strong couplings at relevant tetraquark-
meson-
meson vertices and, hence, a width of the process under consideration. Our prediction $ \Gamma=(48 \pm 6)~\mathrm{MeV}$ along with the mass of this state can be valuable for experimental studies of all-heavy resonances.
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High Energy Physics (Experiment)
Constraints on Sub-MeV Dark Matter from Solar Reflection with DAMIC-M
K. Aggarwal, I. Arnquist, N. Avalos et al. (+41 more)
The Sun acts as a natural dark matter accelerator.
Galactic halo particles scattering in the
solar plasma emerge with velocities well beyond the
Galactic escape speed, providing a boosted flux that extends the kinematic reach of direct detection experiments into the sub-MeV mass regime. We present constraints on
solar-reflected dark matter (SRDM) from the DAMIC-M prototype detector using $\sim$1.3~kg-day of data acquired with silicon skipper charge coupled devices (CCDs) at the Modane Underground Laboratory. Exploiting the spatial
diffusion signature of low-energy electron
recoils, we derive 90% C.L. upper limits on the DM-electron scattering cross section for both heavy- and ultralight-mediator
benchmarks, reaching $\bar{\sigma}_e\sim 3.16 \cdot 10^{-37} \rm{cm^2}$ at $0.1$ MeV. For the ultralight mediator, our limits are competitive with the world-leading constraints, achieved with an integrated exposure of $\sim1.3$~kg-day. These results probe the parameter space between
stellar-cooling bounds and terrestrial limits from standard
halo searches, a region inaccessible to direct detection experiments relying solely on the standard
halo flux.
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All authors K. Aggarwal, I. Arnquist, N. Avalos, X. Bertou, N. Castello-Mor, C. Centeno-Lorca, A.E. Chavarria, A.R. Chriss, J. Cuevas-Zepeda, A. Dastgheibi-Fard, C. De Dominicis, O. Deligny, J. Duarte-Campderros, E. Estrada, R. Ga{\i}or, E.-L. Gkougkousis, T. Hossbach, L. Iddir, B. J. Kavanagh, B. Kilminster, I. Lawson, A. Letessier-Selvon, H. Lin, P. Loaiza, A. Lopez-Virto, R. Lou, H. Lumengo-Kidimbu, S. Munagavalasa, J. Noonan, D. Norcini, S. Paul, P. Perez-Cobo, P. Privitera, P. Robmann, B. Roach, D. Rosenmerkel, M. Settimo, R. Smida, M. Traina, R. Vilar, R. Yajur, D. Venegas-Vargas, C. Zhu, Y. Zhu
High Energy Physics (Experiment)
Commissioning and Low Latency Operation of the Graph Neural Network Electromagnetic Calorimeter Trigger at the Belle II Experiment
M. Neu, F. Baptist, I. Haide et al. (+10 more)
We present the commissioning and operation of the Graph Neural Network Electromagnetic Calorimeter Trigger Module (GNN-ETM) of the Belle II experiment at the SuperKEKB
collider. The GNN-ETM processes calorimeter trigger
cells as graph nodes to perform clustering and feature extraction. We fully integrate the system with the successive stages of the first-level trigger, develop slow-control drivers, and add online monitoring capabilities. We optimise the existing FPGA-based architecture through hardware-
algorithm co-design, achieving an overall system latency of 1.053 us. Our hardware implementation is validated through register-transfer-level simulations, achieving bit-accurate agreement with the offline reference model. Online monitoring enables the measurement of instantaneous trigger rates, providing a quantitative basis for trigger-level performance studies. In summary, we report on the GNN-ETM as a fully operational, low-latency trigger module with online control and monitoring capabilities, compatible with the latency requirements of the Belle II first-level trigger system.
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All authors M. Neu, F. Baptist, I. Haide, Y. Unno, J. Becker, T. Ferber, K. Arai, Y.-T. Lai, T. Koga, M. Maushart, H. Nakazawa, V. Savinov, K. Unger
Plasma Physics
The fixed boundary plasma equilibrium basis for a one Gigawatt electric stellarator power plant
Samuel A. Lazerson, António J. Coelho, Dana Douqa et al. (+9 more)
A fixed boundary stellarator
equilibrium capable of producing 3 GW of fusion power (1 GW-electric) is presented as the design basis for the GIGA fusion power plant being developed by Gauss Fusion GmbH. The stellarator concept provides a steady-state, transient free, low recirculating power approach to a fusion power plant, which builds on 50 years of progress in
plasma physics. A set of requirements for a fixed boundary
equilibrium were determined through application of 0.5 D modeling. Optimization of a modified Wendelstein 7-X (W7-X)
equilibrium was performed to achieve these requirements including alpha power confinement greater than $85\%$, neoclassical effective ripple below 0.01, bootstrap current below 50 kA, and reduced turbulent heat fluxes. In order to fix the
plasma volume of $1500~m^3$ during optimization, the VMEC code was modified to renormalize the boundary coefficient to the desired
plasma volume. The STELLOPT stellarator optimization code was modified as well to include new bootstrap current targets, a new target for the radial electric field, and the capability to hold the
magnetic field on axis at a fixed value. An intermediary conceptual design
plasma and final evolved fixed boundary
equilibria are compared to the original modified W7-X
equilibrium. The final evolved
equilibrium is shown to achieve all the necessary requirements for the GIGA fusion power plant through more detailed modeling of stability, fast ion confinement, and transport.
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All authors Samuel A. Lazerson, António J. Coelho, Dana Douqa, Adrian Asmund Fessler, Luisa Hübner, Matteo Moscheni, Eoin Hodge, Richard Kembleton, Joona Sissonen, Konsta Särkimäki, Antti Snicker, the Gauss Fusion Team
High Energy Physics (Phenomenology)
A Window onto New Invisible Particles via Semi-Visible Higgs Decays
Sally Dawson, Arnab Roy and German Valencia
Searches for new physics continue at the LHC in several forms, including new-particle searches, precision measurements of SM couplings, and searches for signals of new invisible particles. In this talk, we discuss the reach in parameter space of new invisible particles with the semi-visible
Higgs decay modes $H\to \ell^+\ell^- + ~\rm E{\!\!\!/}_T$ and $H\to jj + ~\rm E{\!\!\!/}_T$. We first parametrise the new invisible particles and their interactions with the SM through an effective field theory at dimension six. We then study the respective signals and the corresponding background, finding small signals with large backgrounds. We find, however, that the kinematics of these processes are sufficiently rich to allow a signal extraction that we first quantify with a cut-based analysis and later with a multivariate BDT.
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High Energy Physics (Theory)
$T\bar{T}$ deformation and multiple-flavor Lorentzian threads
Mojtaba Shahbazi and Mehdi Sadeghi
This work is motivated by the proposed relationship among finite cut-off holography and generalized $T\bar T$ deformations, and examines
holographic complexity within the framework of the "complexity = anything" proposal. Employing a Fefferman-Graham expansion near the finite cut-off surface, the deformation-induced correction to generalized complexity is derived and shown to allow a systematic expansion in terms of generalized Willmore-type functionals. The resulting formulation broadens earlier findings for the complexity-volume proposal to encompass arbitrary
geometric complexity measures. Furthermore, the structure of the correction allows a natural interpretation as multiple-
flavor Lorentzian threads, where distinct thread sectors correspond to different
curvature invariants in the complexity functional. These results show a
geometric connection among finite cut-off holography, generalized complexity, and the emergence of non-local computational structures in
holographic quantum field theories.
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Statistical Mechanics
Is the Eyring Plot Misleading? A Case for Arrhenius Analysis of Activation Parameters
Titus S. van Erp
A common view in physical chemistry literature is that the Eyring representation, in which a linear fit of $\ln(k/T)$ versus $1/T$ is attempted, is more fundamental than the Arrhenius representation, $\ln(k)$ versus $1/T$. This perception is typically motivated by its derivation from statistical mechanics and
quantum mechanics, and by the interpretation of the intercept in terms of the activation
entropy $\Delta S^\ddagger$, whereas the Arrhenius equation and its prefactor are often regarded as purely phenomenological. However, harmonic approximation models yield exact linearity in Arrhenius plots but not in Eyring plots, although for real experimental data both generally appear equally linear within typical experimental accuracy. Furthermore, the impression that the Eyring formulation is inherently
quantum mechanical arises from the presence of the Planck constant in the prefactor, whereas this term results from normalization conventions in the partition function. This also highlights an interpretational issue in $\Delta G^\ddagger$, which is based on partition functions of different dimensionality between reactant and transition state. This dimensional mismatch can be reformulated in an alternative representation that improves interpretability and reduces to an Arrhenius-type expression in which the prefactor is directly related to an
entropy of activation. In this framework, both activation enthalpy and
entropy obtained from an Arrhenius fit are arguably more physically relevant than the corresponding Eyring fit values.
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Quantum Physics
PCPOP.jl: A Julia package for partially commutative polynomial optimization
Moisés Bermejo Morán and Abhishek Mishra
Here we present PCPOP, a Julia package for
polynomial optimization that supports non-commutative optimization, tracial
polynomial optimization, trace
polynomial optimization and state
polynomial optimization. PCPOP fully supports exact arithmetic computations and incorporates convenient functionalities such as algebraic reductions based on Gröbner basis methods, automatized symmetrization via Wedderburn decompositions, and Jordan
algebra reductions. As a distinguished feature, PCPOP implements a specialized framework for
polynomial computations in partially commutative variables that provides significant computational advantages for problems appearing in
quantum information.
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High Energy Physics (Phenomenology)
Running coupling effects in the anti-collinear resummation in high energy evolution
Alex Kovner, Michael Lublinsky, Maxim Nefedov et al. (+1 more)
We study the effects of the running of the QCD coupling on the anti-collinear resummation in JIMWLK
evolution in the linear (BFKL) regime. We determine the appropriate scale choice for the coupling entering the JIMWLK kernel, and derive the anti-collinearly resummed BFKL kernel, which includes running-coupling effects both in the resummation equation (i.e. DGLAP) and in the JIMWLK kernel proper. We find that the running of the coupling generally further slows down BFKL
evolution, as expected. Surprisingly however the value of the generalized characteristic function at $\gamma=1$ is unaffected by the running coupling owing to subtle cancellations. We develop an approximation that allows us to use the generalized characteristic function to study the BFKL Green's function. Within this approximation we find that the Pomeron intercept in the anti-collinear regime is significantly reduced by both, the resummation and the running of the coupling.
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All authors Alex Kovner, Michael Lublinsky, Maxim Nefedov, Vladimir Skokov
General Relativity and Quantum Cosmology
Clock-noise subtraction in geometric time-delay interferometry for space-based gravitational-wave parameter estimation
Rui Luo, Pan-Pan Wang, Zi-Jiang Yang et al. (+2 more)
Millihertz gravitational-wave observations with space-based interferometers require time-delay interferometry (TDI) observables whose residual instrumental noise is sufficiently controlled for both detection and parameter inference. Although TDI suppresses
laser phase noise in unequal and time-dependent arms, clock jitter from onboard ultra-stable oscillators can remain above the secondary-noise floor and bias the effective noise weighting used in data analysis. We formulate a clock-noise subtraction scheme directly in the
geometric-TDI framework. The construction introduces generalized clock-noise observables for the four space-time link structures that arise when both delay and time-advance operators are allowed. This makes the clock-noise residual algebraically parallel to the
laser-noise residual and yields explicit subtraction terms for arbitrary two-path
geometric TDI observables. We illustrate the method with representative first- and second-generation
geometric TDI combinations, and test it with time-domain simulations using LISA-like orbits and noise levels. For a modified second-generation U-type observable, the subtraction suppresses the clock-noise residual below the signal region, restores the expected sensitivity to a monochromatic source, and improves the Fisher and Markov-chain Monte Carlo parameter constraints on the source amplitude, frequency and phase. These results show that clock-noise calibration is a necessary component of precision data analysis for future space-based gravitational-wave detectors.
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All authors Rui Luo, Pan-Pan Wang, Zi-Jiang Yang, Wei-Liang Qian, Cheng-Gang Shao
Exactly Solvable and Integrable Systems
Discrete Gerdjikov-Ivanov models and their higher-order counterparts from the Cauchy matrix scheme
Xiao-gang Mu and Song-lin Zhao
The Gerdjikov-Ivanov (GI) equation is an important model in the derivative nonlinear Schrodinger system, yet its fully discrete integrable analogues remain unexplored. In this paper, we systematically construct discrete versions of both the GI equation and its higher-order counterpart (hGI equation) within the Cauchy
matrix framework. Starting from the Sylvester equation equipped with two distinct sets of discrete dispersion relations, we derive the shift dynamics of the master functions and eliminate auxiliary variables to obtain closed
lattice systems. Since the elimination step admits several equally valid algebraic identities, this procedure yields four conjugate-symmetric families of discrete GI (dGI) models and four families of discrete higher-order GI (dhGI) models. For each discrete model, we provide explicit N-
soliton and multiple-pole solutions via the Cauchy
matrix method with diagonal and Jordan-block spectral
matrices, respectively. We verify through a two-step continuum limit, contracting one
lattice direction at a time, that all four dGI models reduce to the same continuous GI equation and all four dhGI models reduce to the same continuous hGI equation. Finally, we investigate reductions: local complex conjugate reductions yield scalar dGI and dhGI equations with explicit solutions. Moreover, in the higher-order case, pairwise recombinations of the dhGI
lattice equations admit nonlocal reductions that produce nonlocal dhGI equations and their solutions.
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Chaotic Dynamics
Global continuation as a complement to traditional continuation and bifurcation analysis
George Datseris, Andreas Morr, Muhammed Fadera et al. (+1 more)
Multistable dynamical systems are ever-prevalent, used to model for example ecosystems, power grids,
climate elements,
neurons, and more. When perturbed, such systems may “tip” from one state of operation to another, often with abrupt, irreversible, and high-impact consequences in each context. Traditionally, these systems are analysed via bifurcation diagrams, the result of a process we refer to as local continuation, as it only captures the linear (local) system response to infinitesimal perturbations. Local continuation requires substantial expertise, constant interventions, and may yield inaccurate assessment of the system's response to large perturbations that is crucial for tipping analysis. To address some inherent challenges of local continuation and to provide fundamentally new information during a continuation, this paper introduces global continuation as a complement suitable for the study of multistability, critical transitions and real-world-oriented applications. Global continuation finds and continues in parallel (practically) all system attractors and their response to finite perturbations by synthesising information from the whole state space, while placing a focus on the qualities or observables of a dynamical system that the practitioner cares about in context. Global continuation does not require deep expertise and is effortless to use and troubleshoot, making it attractive to applied scientists from different disciplines. We highlight several unique advantages that allow global continuation to complement the status quo and exemplify them through a plethora of representative examples. Global continuation is also implemented as open source software in DynamicalSystems.jl, enhancing its accessibility.
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All authors George Datseris, Andreas Morr, Muhammed Fadera, Juergen Kurths
General Relativity and Quantum Cosmology
Nonlinear stability of Einstein-de Sitter universes
Louie Bernhardt, David Fajman and Zoe Wyatt
The Einstein-de Sitter universe is the prevailing model used in cosmology to describe the cold dark matter-dominated epoch of the universe. This model is a spatially homogeneous and isotropic spacetime undergoing decelerated expansion, and is linearly unstable under the Einstein-Euler equations with a pressureless fluid equation of state. We show that every initial data set for the Einstein-Euler equations on $\mathbb{T}^3$ with a near-flat metric and positive fluid energy density converges to a flat metric under the Einstein-Euler flow with a polytropic equation of state. This means the metric asymptotes to an Einstein-de Sitter spacetime. In particular, this settles the question of whether the Einstein-de Sitter model can be nonlinearly stable for an appropriate matter model.
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General Relativity and Quantum Cosmology · Cross-listed from math.DG
A note on the stability of surfaces along null cones under area-preserving variations
Markus Wolff
In this note we investigate a notion of stability for spacelike cross sections of a null cone under area preserving variations that has been introduced in previous work by Kröncke and the author. Here, we consider null cones with spherical cross sections in a $4$-dimensional spacetime and show that the Hawking energy of a stable cross section admits a non-negative lower bound provided the dominant energy condition holds. Similar to a recent work by Peñuela Diaz, we show that under an additional assumption the Hakwing energy is zero if and only if the stable cross section embeds isometrically into the Minkowski lightcone. As a main result, we show that the only stable cross sections of the standard Minkowski lightcone are round spheres.
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Materials Science
Semi-Empirical Kinetic Model for Phase Selection in Rapidly Solidified Multicomponent Concentrated Alloys
O.I. Kushnerov, S.I. Ryabtsev and V.F. Bashev
A semi-empirical kinetic framework is formulated for predicting phase selection in multicomponent concentrated
alloys under rapid solidification. The approach is based on the critical cooling rate required to suppress competing crystalline pathways and combines
topology-dependent ranking of BCC-, FCC-, and HCP-like crystallization pathways with a correction for glass-forming ability. The formulation includes a
topology-dependent viscosity correction with a smoothed BCC multiplier and a continuous correction factor for glass-forming ability based on mixing enthalpy, excess
entropy, and atomic-size dispersion. Comparison with experimental and computational data shows that the kinetic criterion captures changes in the
lattice type expected from the valence electron concentration criterion, describes kinetic suppression of phase separation, and identifies competitive multiphase crystallization. The model also distinguishes
alloys with high and low glass-forming ability. The proposed framework provides a practical approach for preliminary evaluation of kinetic phase competition in rapidly solidified multicomponent melts.
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Earth and Planetary Astrophysics
The GAPS Programme with HARPS-N at TNG LXXVII. Occurrence rates of small close-in planets in the presence of cold Jupiters
A. Ruggieri, S. Desidera, M. Pinamonti et al. (+18 more)
Context. The architecture of our
Solar System, with inner small
planets (ISPs) and outer
giants, may or may not be common. Understanding whether a correlation exists between ISPs and outer cold
giants is key to evaluating how common systems with a similar architecture to our own are. Aims. This study aims to build a large, homogeneous sample of systems hosting cold Jupiters (CJs, a > 1 au, msini > 0.1 M$_J$) detected via radial velocities (RVs), and to assess the presence of additional ISPs (P < 400 d, 3 < msini < 31.7 M$_{\oplus}$), studying the correlation between these two types of objects. Methods. We selected 137
stars known to host a CJ, including 23 which also harbor a hot Jupiter and were treated separately. Data from various instruments were compiled, including unpublished data gathered with HARPS-N within the GAPS program, and consistently fitted using PyORBIT. We derived RV detection maps and calculated occurrence rates for ISPs, cross-validating results with two independent codes. The sample was divided into subgroups to evaluate how system parameters influence
planet occurrence. Results. We confirmed the 213 already known
planets in the 137 systems and also identified six new candidates. We divided them, based on mass and period, into Neptunes (10 < m sin i < 31.7 M$_{\oplus}$) and Super-Earths (3 < m sin i < 10 M$_{\oplus}$), and into hot (1 < P < 10 d), warm (10 < P < 100 d), and cool (100 < P < 400 d). We found occurrences of 5%, 13%, and 12% for hot, warm, and cool Neptunes, respectively, and 11% and 16% for hot and warm Super-Earths, respectively. Systems with dynamically stable inner regions show higher rates of small
planets. These findings are consistent with previous studies showing no strong correlation between ISPs and CJs at average
stellar metallicity and mass, and suggest that HJs may be more commonly associated with external
giants.
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All authors A. Ruggieri, S. Desidera, M. Pinamonti, D. Barbato, A. Sozzetti, A. S. Bonomo, L. Naponiello, M. Damasso, S. Benatti, I. Carleo, R. Gratton, K. Biazzo, A. F. Lanza, G. Piccinini, N. Nari, G. Mantovan, J. Maldonado, D. Nardiello, A. Fiorenzano, A. Ghedina, A. Bignamini
Quantum Physics
Operational Shadows of Hilbert-Space Probabilities
Karl Svozil
At one frozen setting, the probabilities observed in a sharp
quantum context are indistinguishable, as detector-click statistics, from ordinary probabilities on the atoms of a classical partition. But an actual analyzer usually comes with a calibrated knob: a tangible handle on the apparatus. If the measurement configuration is co-varied continuously through this physical parameter, the operational object is no longer one point of a simplex but a response curve. Classical linear responses, Malus-type
Hilbert-space responses, softmax links, non-homomorphic parameter transcriptions, and discontinuous threshold limits are different maps from settings to probabilities. Continuity, calibration, and preservation of the physical composition law are then part of the experimental meaning of the knob. Such comparisons distinguish specified, calibrated response models; by themselves they do not constitute a classical-versus-
quantum impossibility
theorem. The static operational coincidence can also persist for two intertwined contexts: if the common outcomes receive the same probabilities, the remaining masses can always be coupled by a classical joint distribution. Genuine multi-context nonclassicality begins when a family of local shadows cannot be glued into one nonnegative global distribution or one simplex factorization. Farkas' lemma gives the exact alternative: either the classical extension exists, or a separating linear inequality certifies its impossibility.
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General Relativity and Quantum Cosmology
The significance of first post-adiabatic contributions for scalar charge measurements with intermediate and extreme mass ratio inspirals
Susanna Barsanti, Ollie Burke, Andrea Maselli et al. (+3 more)
We present the first self-force-based beyond-GR waveform model incorporating post-adiabatic orbital
evolution for intermediate- and extreme-mass-ratio inspirals in theories of
gravity with additional scalar fields. Focusing on quasi-circular inspirals into a non-spinning primary, we combine a first post-adiabatic (1PA) gravitational sector with leading-order scalar field effects and use
Bayesian injection-recovery studies to assess the impact of waveform systematics on the inference of scalar charges with LISA. We find that neglecting 1PA effects in the gravitational sector can bias the inference of intrinsic binary parameters, while scalar-charge measurements remain robust across a wide range of mass ratios. In contrast, analysing signals from binaries in which the secondary carries a scalar charge using pure-GR templates leads to significant biases and underestimated uncertainties due to unmodelled correlations between the scalar charge and the binary parameters. We also investigate the role of secondary
spin and find no significant correlation between the secondary
spin and the scalar charge. Notably, up to a mass ratio of $10^{-4}$, the secondary
spin itself remains unconstrained even in the pure-GR case, in contrast with previous claims in the literature. Finally, we show that modelling scalar emission with a leading-order dipolar post-Newtonian approximation – for quasi-circular inspirals into a non-spinning primary – introduces negligible systematic errors relative to fully relativistic scalar fluxes.
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All authors Susanna Barsanti, Ollie Burke, Andrea Maselli, Thomas P. Sotiriou, Andrew Spiers, Niels Warburton
Astrophysics of Galaxies
Structural Diversity Among the Milky Way's Dwarf Spheroidal Satellites
Matthew G. Walker, Raphaël Errani, Andrew B. Pace et al. (+3 more)
We fit a flexible double power-law (`$\alpha\beta\gamma$') model to the
stellar density fields observed for the Milky Way's known
dwarf spheroidal satellite
galaxies. We show that where standard criteria for model selection are decisive, the $\alpha\beta\gamma$ model is favored over the special case of the Plummer model, and also over the \sersic\ model and its special case, the exponential. The Milky Way's dSph population exhibits a diverse range of
stellar density profile shapes, as quantified by the values we infer for outer and inner power-law indices $\beta$ and $\gamma$. Several of the most massive dSphs (e.g., Eridanus II, Fornax, Leo I, Leo II) have steeply-declining outer profiles, with $\beta\gtrsim 8$; others (e.g., Sextans, Boötes I) fade slowly, with $\beta\lesssim 4$. The inner profiles of dSphs with
stellar mass $\gtrsim 10^5 M_{\odot}$ are consistent with `cores' of uniform
stellar density ($\gamma\approx 0$). At lower masses the slopes of inner density profiles are poorly constrained, except in a few ultrafaint dSphs (e.g., Hercules, Ursa Major II) where we infer steep
stellar cusps, with $\gamma\gtrsim 1.5$. Owing to the $\alpha\beta\gamma$ model's flexibility, the inferred halflight radii and total
stellar masses are significantly more uncertain than previous estimates, with halflight radii larger by up to an order of magnitude in some cases. Finally, we demonstrate that allowing for flexibility in the shape of the
stellar density profile is crucial for dSph mass modeling, where systematic errors associated with choice of
stellar density profile can outweigh random errors in the observed velocity dispersions.
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All authors Matthew G. Walker, Raphaël Errani, Andrew B. Pace, Jorge Peñarrubia, Sofia Splawska, Eduardo Vitral
Optics
Optical Fourier Surfaces for Free-Space Computer-Generated Holography
Y. M. Glauser, C.-Y. Shen, D. B. Seda et al. (+10 more)
Computer-generated holography can shape electromagnetic fields by encoding wavefront information in nanostructured surfaces. However, despite significant progress, hologram designs for visible and near-infrared wavelengths remain largely limited by fabrication constraints. Most implementations rely on lithographic methods that produce discretized surfaces that do not match the wave nature of light. Further advances would benefit from accurate continuous (grayscale) control of interfacial profiles, which would allow straightforward design principles from
Fourier optics to be applied. In this work, we introduce optical
Fourier surfaces as a versatile, intuitive platform for free-space computer-generated holograms. Exploiting these arbitrarily wavy surfaces, we demonstrate three different design strategies for computer-generated holography. First, we use an analytical linear design approach based on sinusoidal lenses and gratings as fundamental
holographic building blocks. Second, we enhance diffraction efficiencies through an iterative
Fourier-transform
algorithm. Finally, we extend our framework with machine-learning-based inverse design, creating wavelength-multiplexed holograms that reconstruct distinct diffraction responses in a predefined image plane. Our results combine advanced thermal scanning-probe lithography with flexible design strategies to create useful structures for photonic applications, particularly in settings where rapid prototyping is crucial.
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All authors Y. M. Glauser, C.-Y. Shen, D. B. Seda, Ç. Işil, P. Benito Eberhard, H. Niese, J. G. Crimmann, D. Petter, G. Nagamine, S. J. W. Vonk, N. Lassaline, A. Ozcan, D. J. Norris
Materials Science
Learning to Converge: Warm-Starting DFTB Self-Consistent Charges with Machine Learning
Maximilian L. Ach, Karsten Reuter and Chiara Panosetti
Semiempirical electronic structure methods such as Density-Functional Tight-Binding (DFTB) offer a computationally efficient approach to molecular and materials simulations, bridging the gap between first-principles accuracy and classical force field speed while retaining full access to electronic properties. However, DFTB calculations based on self-consistent charge (SCC) schemes can still suffer from slow convergence, particularly for complex molecular and materials systems, making the iterative procedure a significant bottleneck in large-scale simulations and high-throughput workflows. We present a machine learning approach that accelerates DFTB simulations by predicting optimal initial atomic charges. Using element-specific models based on the Smooth Overlap of Atomic Positions descriptor and kernel ridge regression, we train charge models on reference calculations and demonstrate that ML-predicted initial charges consistently and significantly improve SCC convergence across diverse chemical systems including organic molecules, biomolecules, water clusters, transition metal
oxides and solid electrolytes.
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Mathematical Physics · Cross-listed from math.AP
Local well-posedness for nonlinear Dirac equation on $N$-star metric graphs
Huichao Xing and Zhipeng Yang
We consider the Cauchy problem for the nonlinear Dirac equation on a noncompact $N$-
star metric graph $G$, \[ \mathrm{i}\partial_t \psi = D\psi - |\psi|^{p-2}\psi, \qquad \psi(0)=\psi_0, \] where $p\ge3$, $\psi:\mathbb{R}\times G\to\mathbb{C}^2$ and $D$ denotes the self-adjoint Dirac-Kirchhoff operator on $G$. Using Bourgain-type spaces defined through the spectral resolution of $D$, together with elementary $L^\infty$ bounds for the Dirac flow and fractional Nemytskii estimates below the trace threshold, we prove local well-posedness for initial data \[ \psi_0\in H_D^s(G)\cap L^\infty(G;\mathbb C^2), \qquad 0\le s<\frac12 . \] The corresponding solution belongs to \[ C([0,T];H_D^s(G))\cap X_T^{s,b}\cap L^\infty([0,T]\times G). \] Moreover, $\|\psi(t)\|_{L^2(G;\mathbb{C}^2)}$ is conserved along the solution on the existence interval. We also establish a blow-up alternative in the combined $H_D^s$ and space-time $L^\infty$ control norm.
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Optics
Universal Neural Network Based Calibration and Control of Programmable Classical and Quantum Photonic Integrated Processors
José Roberto Rausell-Campo, Daniele Melati, Bhavin Shastri et al. (+2 more)
Efficient calibration and control of programmable photonic integrated
circuits are fundamental for scaling
quantum and classical optical computing processors. While neural network-based models offer an architecture-agnostic solution, existing approaches suffer from limited learning and generalization capabilities due to the many-to-one mapping problem between sets of control signals and optical responses, and biased training
datasets derived from uniform current sampling. In this work, we propose a universal calibration and control framework employing tandem neural networks combined with two novel data generation strategies: architecture-aware sampling based on Haar measure principles, and optimized sampling, a physics-agnostic approach utilizing differential
evolution. We experimentally validate these methods on 3x3 and 4x4 coherent MZI meshes, demonstrating that our approach addresses the sampling bias inherent in previous works. When evaluated using random
unitary matrices, our solution outperforms standard uniform sampling baselines by ~2 bits of precision. Furthermore, we experimentally extend the application of this framework to coherent detection, achieving precise control over both amplitude and phase, and validate its impact on photonic neural network tasks.
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All authors José Roberto Rausell-Campo, Daniele Melati, Bhavin Shastri, Daniel Pérez-López, José Capmany Francoy
Materials Science
Kinetic Cellular Model of Corrosion
Orkan Sezer and Andrew Horsfield
Aqueous corrosion of metals involves multiple interconnected processes. Thus, computer simulation of corrosion as a whole needs to be able to describe the individual processes and how they influence each other. Atomistic simulations are designed to obtain detailed information for small regions of space over short times. Thus there are limits to the understanding that can be obtained by atomistic simulations alone. Here is presented a method that uses generalised rate equations to extend the length and time scales that can be accessed. It is shown to reduce to either the phase field or cellular automata methods in certain limits. The generalised kinetic equations can reproduce the behaviour described by both the Nernst-Planck and Butler-Volmer equations, which are frequently used to describe corrosion. In addition, the method can describe local rearrangements of atoms such as chemical reactions. Example results are shown for illustrative 1D and 2D problems, with good agreement being found with other methods.
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High Energy Physics (Phenomenology)
Diffusion Monte Carlo study of deuteron-like fully light hexaquarks
M.C. Gordillo and J. Segovia
We perform a
Diffusion Monte Carlo study of fully light hexaquarks containing three $u$
quarks and three $d$
quarks within a constituent-
quark model. Both compact and
baryon–
baryon-like arrangements were considered separately. All compact hexaquark configurations are found well above their corresponding
baryon–
baryon thresholds, suggesting that deeply bound compact six-
quark states are not favored in the light-
quark sector within this model. By contrast, several dibaryon-like configurations lie close, but above, to the $NN$, $N\Delta$, and $\Delta\Delta$ thresholds and show spatial structures compatible with molecular states. One configuration exhibits two well-defined nucleon-like subclusters separated by several femtometers, characteristic of deuteron-like spatial clustering, although its calculated energy remains slightly above the corresponding threshold.
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Instrumentation and Methods for Astrophysics
Enhancing the Cherenkov Telescope Array Observatory high-level performance through an event-type-based analysis
Juan Bernete, Silvia García-Soto, Tarek Hassan et al. (+4 more)
The analysis traditionally employed by Imaging Atmospheric Cherenkov
Telescopes involves optimizing quality cuts to select a sub-sample of high-quality events. These events are used for the scientific interpretation of the data, employing a single set of Instrument Response Functions (IRFs). All selected events are treated equally and assumed to be well represented by these IRFs, while the rest are discarded. An alternative approach, successfully applied in experiments such as
Fermi-LAT, is an event-type-based analysis. This method divides
datasets into subsamples, each containing events of a given expected reconstruction quality. IRFs are computed for each subsample independently, improving the accuracy with which IRFs represent the reconstruction quality of each event. The high-level analysis of these subsamples is performed treating them as independent observations, each with their own set of IRFs, and analyzed jointly. In this work we present a proof-of-concept implementation of an event-type-based analysis for the future CTAO using simulated data. A neural network (specifically a multi-layer perceptron) is trained to predict the direction reconstruction error of each event, and the simulated
dataset is divided into event types based on this predicted variable. We compute IRFs for each event type and compare them with those from the standard analysis (without event types). Finally, we simulate observations using these event-type-wise IRFs and analyze them with high-level analysis tools to test the performance of both approaches. This implementation demonstrates notable improvements: 25% to 50% boost in spatial resolving power and ~25% in sensitivity. This boost in performance will have strong implications in the scientific exploitation of the CTAO data, especially in crowded regions such as the
Galactic Plane or searching for spectral signatures like Dark Matter annihilation lines.
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All authors Juan Bernete, Silvia García-Soto, Tarek Hassan, Orel Gueta, Maximilian Linhoff, Atreyee Sinha, Gernot Maier
Cosmology and Nongalactic Astrophysics
Primordial Black Hole mass growth from neutrinos during the radiation era
Maël Gonin
We present a new picture of
primordial black holes mass
evolution through
neutrino absorption. Using semi-classical approach and a closer look at the kinetic of the early
plasma we revisit the thermal absorption of radiation by a population of
primordial black holes ranging from $10^{-3}-10^9 M_\odot$ embedded in a thermal bath. We find significant mass growth of intermediate mass and supermassive PBHs, the effect shift the predicted $e^+e^-$ peak from thermal history. Depending on the value of the collapse fraction an additional peak around the intermediate mass range, might become significant. Moreover, because PBH grow from the thermal bath the fraction of DM in PBH $f_{\rm PBH}$ also change. These results revise the previous view on mass
evolution of PBH and have implications for dark matter PBH observations.
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High Energy Physics (Phenomenology)
Leptogenesis with sub-electroweak-scale reheating temperature
Basabendu Barman, Arindam Basu, Debasish Borah et al. (+1 more)
We study the generation of the
baryon asymmetry of the Universe via leptogenesis during the post-inflationary reheating epoch, considering reheating temperatures below the temperature of sphaleron freeze-out. Within the framework of a monomial inflaton potential during reheating, we analyze three perturbative reheating scenarios in which the inflaton decays into (i) a pair of Standard Model (SM)-like
bosons, (ii) a pair of SM-like
fermions, or (iii) exclusively into a pair of heavy right-handed
neutrinos, which eventually decays into the SM final states after briefly dominating the energy density of the Universe. For each case, we identify the regions of parameter space that successfully reproduce the observed
baryon asymmetry consistently tracking the sphaleron interaction rate during reheating, while satisfying existing cosmological constraints. We also highlight the potential of future
primordial gravitational wave observations to probe this class of scenarios.
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All authors Basabendu Barman, Arindam Basu, Debasish Borah, Nayan Das