Solar and Stellar Astrophysics
Pre-main Sequence B Stars Surrounding the Orion Nebula
P.H.F.B. Braz, A. Roman-Lopes, W.J.B. Corradi et al. (+6 more)
Pre-main sequence (PMS) early-type
stars are rare due to their rapid
evolution. Confirming PMS B
stars is accordingly valuable for constraining higher mass
star formation scenarios. Although the Orion Nebula (ON) region offers an ideal laboratory for such studies, its population of B
stars remains poorly characterized. We aim to determine spectral types, masses, and ages of B and early A
stars surrounding the ON, to identify robust PMS candidates. We combine optical and near-infrared spectroscopy to estimate spectral types using Brackett, He, Si, and Mg lines. Photometry from
Gaia, 2MASS, and WISE is used to construct colour-magnitude diagrams to fit isochrones via chi-square minimisation, yielding
stellar ages and masses. Dynamical masses from eclipsing binaries are employed as independent constraints on the mass range allowed for each spectral subtype. We derive
stellar ages and masses for 53
stars and spectral classifications for 48 of them, identifying 30 PMS candidates, including some that were previously assigned to luminosity classes I-III. Several
stars show spectroscopic variability, potentially linked to circumstellar material or binarity. Our combined spectroscopic and photometric approach identifies robust PMS B-
star candidates and provides a validated framework for distinguishing them from evolved counterparts - in this instance, refining the census of early-types young
stars in Orion. The age distribution of the PMS candidates offers preliminary clues about the
star formation history of the ON region.
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All authors P.H.F.B. Braz, A. Roman-Lopes, W.J.B. Corradi, E. B. Amôres, M. S. Angelo, F. S. S. Maia, J. F. C. Santos Jr., A. E. Piatti, W. Reis
Quantum Physics
Boosting State Discrimination in Quantum Brownian Motion Channel via Memory-Induced Coherence Preservation
João C. P. Porto, Pedro R. Dieguez, Carlos H. S. Vieira et al. (+3 more)
Preserving
quantum resources in dissipative environments is a fundamental challenge in
quantum information processing. While environmental interactions usually degrade
quantum resources, we theoretically show that in a
Quantum Brownian Motion (QBM) channel, continuous-variable state discrimination can be improved by increasing, rather than minimizing, the initial thermal noise. Specifically, without suppressing the inherent environmental dissipation, when combined with squeezing, this initial noise induces a coherence preservation mechanism driven by the transient non-thermalization of the probe with the bath. This preservation translates into a pronounced reduction in error probabilities for state discrimination between orthogonal squeezing directions. Furthermore, we also show that quadrature homodyne detection achieves near-optimal performance, approaching the Helstrom limit. These results highlight the advantage of exploiting thermal-squeezed states, offering a robust physical architecture for
quantum communication in high-temperature environments.
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All authors João C. P. Porto, Pedro R. Dieguez, Carlos H. S. Vieira, Irismar G. da Paz, Giandomenico Palumbo, Lucas S. Marinho
High Energy Astrophysical Phenomena
Large-scale emission from gamma-ray binaries: the case of LS 5039
J. R. Martinez and V. Bosch-Ramon
Abridged abstract: Context: Gamma-ray binaries hosting a non-accreting
neutron star and a massive
star exhibit multi-wavelength emission on different spatial scales. The interaction between their winds produces an
outflow that can inflate a bubble or form a bow shock as it interacts with the surrounding medium. LS 5039 shows extended (1 pc-scale) X-ray emission that may arise from one of these large-scale structures. Aims: We explain and predict the large-scale emission from LS 5039. Methods: We modelled the thermal and non-thermal emission from five scenarios, representing different evolutionary phases, assuming particle acceleration at the mixed-wind termination shock: three bubble scenarios, treated with a one-zone model, and two bow-shock scenarios, studied with a multi-zone approach. We also investigated the radiation from escaping particles. Results: The extended X-rays are best explained as synchrotron radiation. Some scenarios predict detectable
radio emission, while escaping particles may provide a minor steady contribution to the gamma rays in the powerful bow-shock scenario. Escaping
protons with energies of 0.1-1 PeV could also inject up to $\sim10^{36}$ erg s$^{-1}$ into
Galactic cosmic rays for optimistic injection luminosities. Conclusions: Gamma-ray binaries can efficiently accelerate particles on large scales, producing broadband emission and 0.1-1 PeV
cosmic rays. Our results can guide future multi-wavelength observations to constrain the large-scale interaction, age, and birthplace of LS 5039.
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Quantum Physics
Saturating the Bayesian Nagaoka-Hayashi bound within numerical precision for the depolarization SU(2) rotation channel
Leo Bia and Christos N. Gagatsos
The
Bayesian Nagaoka–Hayashi (NH) bound is a semidefinite lower bound on the Bayes risk of multiparameter estimation, tighter than the
Bayesian symmetric logarithmic derivative (SLD) Cramer–Rao bounds, and whether it can be attained is an open problem. We study the single-shot estimation of a
qubit rotation, all three parameters at once, under depolarizing noise and a uniform prior, with k parallel uses of the channel. Rotational covariance reduces the joint optimization of probe, measurement, and
estimator, and the NH bound itself, to small semidefinite programs, solvable through k=4. At every number of uses and noise strength the optimized strategy reaches the NH bound within the numerical precision of the calculation, numerical evidence that the bound is attained for this channel family, while the SLD bound lies strictly below and is never attained. As the noise grows the optimal probe collapses to the tensored Bell state.
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Optics
Contest between diverging k-vectors and astigmatism in an aberrated randomly scattered light
Abhijit Roy and Maruthi M. Brundavanam
The impact of astigmatism on randomly scattered light, here speckles which are generated from a ground glass (GG) plate, is investigated by studying the change in the shape of the intensity correlation function (ICF) of the speckles for different amount of astigmatism introduced to it by rotating a lens at different angles. It is observed that the shape of the ICF, which reflects the average shape of the speckles, changes from circular to elliptical with the change of the tilt angle of the lens (theta), and the variation of length of two axes of the ICF with theta is completely different in nature. It is shown that these different natures are observed due to a contest between the diverging k-vectors of the speckles and the astigmatism introduced by the tilted lens system. It is also found that the diverging k-vectors resist the effect of astigmatism on the speckles, and after a certain theta, the impact of astigmatism becomes prominent. The contest between the diverging k-vectors and astigmatism in an aberrated speckle pattern are confirmed by further experimental studies and are discussed in detail. This study will surely be helpful in designing different imaging systems, where scattered light plays an important role.
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High Energy Physics (Phenomenology)
Solar-System Abundances of $p$-Nuclides Probe Collective Neutrino Oscillations in Supernovae
Alexander Friedland, Derek J. Li, Giuseppe Lucente et al. (+3 more)
Direct evidence for collective
neutrino oscillations in core-collapse
supernovae remains elusive. We show that this
quantum phenomenon leaves a footprint on the abundance pattern of
proton-rich nuclides in the
solar system. Modeling the $\nu p$-process using a $20\,M_\odot$ progenitor, we map out the dependence of the total yields on the starting radius of the oscillations, self-consistently coupling hydrodynamics and nucleosynthesis. The oscillations boost key $p$-nuclides ($^{92,94}\text{Mo}$, $^{96,98}\text{Ru}$) and long-lived $^{92}\text{Nb}$ by up to two orders of magnitude, bringing their abundances into agreement with the observations. The best match is found when oscillations commence within $10\text{ km}$ of the proto-
neutron star surface, indicating fast collective oscillations.
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All authors Alexander Friedland, Derek J. Li, Giuseppe Lucente, Payel Mukhopadhyay, Ian Padilla-Gay, Amol V. Patwardhan
Earth and Planetary Astrophysics
Ephemeris Refinement for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b with Small Telescope and TESS Observations
Heather B. Hewitt, Mikaela Chamlee, Trinity Hockman et al. (+45 more)
We present updated transit timing measurements for three hot Jupiters (Qatar-4 b, HAT-P-18 b, and CoRoT-1 b) by leveraging data collected from the MicroObservatory
Telescope Network, a network of small, robotic ground-based
telescopes, and the NASA Transiting
Exoplanet Survey Satellite (TESS). By combining these data with archival published results, we present the most precise orbital solutions to date for all three systems, allowing for precise transit time predictions for future missions. We report an updated mid-transit time for Qatar-4 b of 2458919.5838 $\pm$ 0.000089 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.80536560 $\pm$ 0.00000021 days. For HAT-P-18 b, we find a mid-transit time of 2459743.85340 $\pm$ 0.000022 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 5.50802957 $\pm$ 0.00000012 days. For CoRoT-1 b, we report a mid-transit time of 2456268.99083 $\pm$ 0.000099 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.50896846 $\pm$ 0.000000071 days. Our results demonstrate improvements over recently published ephemerides, with reductions of 36.4%, 4.35%, and 17.5% in mid-transit time uncertainties and 65.0%, 77.4%, and 16.9% in orbital period uncertainties for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b, respectively. The results of this study improve the precision of future transit predictions and demonstrate the value of coordinated small-
telescope monitoring (and citizen science initiatives) when updating the orbital parameters of hot Jupiters.
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All authors Heather B. Hewitt, Mikaela Chamlee, Trinity Hockman, Annalise Igyarto, Dan van der Burg, Federico R. Noguer, Ira Bell, Jeremie Abides, Simon Abshear, Philip Arthur Ellis, Shashank Avinash Araokar, Eurico Bras, Jamie Buckingham, Dion Bumpus, Kartavya Chauhan, Logan Conrad, Koty Creel, Courtney Dammann, Samantha Duarte Rodriguez, Jeffrey Ensor, Benjamen Erickson, Adam Facciponti, Logan Farrar, Blaise Foca, Holly Foreman, Mark Foreman, Haley Fournier, Jeff Franklin, Keith Goss, Dustin Hubbartt, Nicolette Jeantilus, Justin Kobrin, Spencer Lunsford, Wyatt McCormick, Zachary McNeely, Kurtis Merrill, Sarah Miller, Dean Miller, Sofie Miura, Cody Montgomery, Karina Munoz, Keith Norton, Anna Plum, Jake Raby, Jay Thompson, Sohley Wallace-Pichardo, Molly N. Simon, Robert T. Zellem
Solar and Stellar Astrophysics
Luminous Red Novae as shock-powered transients I: Electron-scattering wings and deviations from Case B
Albert Sneppen, Kenta Hotokezaka and Christopher M. Irwin
Luminous red novae (LRNe) are a class of optical transients resulting from the mergers of binary
stars or common envelope events. The population displays heterogeneous light curves with extended luminosity plateaus and/or secondary peaks, suggested to be powered by hydrogen recombination or shocks between pre- and post-merger ejecta. However, much of their spectroscopic behaviour remains unexplained. Using a sample of six LRNe, we identify telltale spectral evidence for shock processes across the LRNe luminosity range ($10^{38}$-$10^{41}\,\mathrm{erg/s}$): (i) fast ejecta sweeping up slower upstream material; (ii) composite epochs with two distinct components, namely a cool
stellar-like continuum underneath a hot nebular recombination region; and (iii) extremely broad line wings extending to $1000$-$10\,000\,\mathrm{km/s}$. Such line profiles reveal
photons scattering off hot electrons in an
outflow ($T_e\sim5000$-$10\,000 \,\mathrm{K},\,v_{es}\!\sim\!300$-$500\, \mathrm{km/s}$), with recombination seen from both the upstream and downstream of the shock surface. Additionally, constraints on the density of the upstream medium are obtained from recombination-line ratios, where brighter LRNe show deviations from Case B, consistent with denser surrounding environments. Given the
outflow's velocity and surrounding density constraints, the shock luminosity is sufficient to account for the total energetics of LRNe without requiring other energy-injection mechanisms. During the plateau phase, the scattering wings are hidden and line ratios are affected by radiative transport effects, which highlights the utility of post-plateau phase spectroscopy.
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Materials Science
Phase-Field Simulation of Dendrite Evolution in All-Solid-State Sodium Batteries during Cycling
Chengyin Wu, Wolfgang Windl, Jung-Hyun Kim et al. (+1 more)
Dendrite growth during cycling remains a critical challenge for all-solid-state batteries (SSBs), limiting the full realization of their inherent safety and high energy density. In particular, the mechanisms of continuous dendrite penetration during charge-discharge cycling remain poorly understood and are difficult to characterize experimentally. This study applies a phase-field model, informed by density functional theory calculations, to rationalize and visualize the dendrite penetration behaviors during cycling in sodium (Na) SSBs with pure Na or Na-Sb
alloy anodes and polycrystalline Na$_3$SbS$_4$ electrolyte. We show that dendrite stripping is intrinsically asymmetric with respect to plating due to grain boundary geometry, leading to the formation of isolated Na metal that persists between cycles. This residual Na metal becomes kinetically stabilized at grain-boundary junctions and is readily reactivated during subsequent plating, thereby accelerating and amplifying dendrite penetration. We further investigate the effects of applied voltage, solid-electrolyte microstructure, and anode chemistry on this phenomenon. These findings establish isolated Na metal as a key contributor for continued dendrite propagation in Na SSBs and provide design principles for stabilizing anode/electrolyte interfaces in Na SSBs.
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All authors Chengyin Wu, Wolfgang Windl, Jung-Hyun Kim, Yanzhou Ji
High Energy Physics (Phenomenology)
Charge-Odd Hyperon Polarization from Magnetic Spin Precession
Dushmanta Sahu and Captain R. Singh
We demonstrate that polarized strange
quarks undergo Larmor precession in the intense
magnetic field produced in non-central heavy-ion collisions and as a possible source of charge-odd hyperon polarization. Strange and antistrange
quarks carry opposite electric charges and therefore acquire opposite precession phases. This opposite
spin rotation mixes the transverse and longitudinal polarization components, yielding measurable polarization splittings between $\Lambda$ and $\bar{\Lambda}$ hyperons. For the
magnetic-field
evolution scenarios, the predicted splittings reach the sub-percent level and are within the experimentally accessible range at RHIC and the LHC energies. These charge-resolved hyperon polarization observables provide a direct probe of
magnetic-field-driven
spin dynamics of deconfined QCD matter at ultra-relativistic heavy-ion collisions.
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Instrumentation and Methods for Astrophysics
Assembly, integration, and verification of MITESI: an optical testbed for simulating the ELT in the laboratory
Daniel J Ahrer, M. Concepción Cárdenas Vázquez, Thomas Bertram et al. (+5 more)
MITESI is an optical testbed which simulates key characteristics of the ELT, ultimately producing an artificial natural guide
star. It was designed primarily to enable testing of the METIS instrument's SCAO system in closed loop. In this contribution, we discuss the assembly, integration and verification process of the testbed, taking the project from design to assembled hardware.
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All authors Daniel J Ahrer, M. Concepción Cárdenas Vázquez, Thomas Bertram, Peter Bizenberger, Armin Huber, Raphaël Pourcelot, Silvia Scheithauer, Horst Steuer
Fluid Dynamics
Controlled drop generation via ligament extraction from a static or vibrating liquid bath
Johnathan Hoggarth, Daniel M. Harris, John W.M. Bush et al. (+1 more)
We introduce a simple method for generating droplets at the surface of a
liquid bath by rapidly stretching a
liquid ligament with a spring-loaded cylindrical probe. By varying the probe radius $a$ and retraction length $L$, we identify three regimes. Overstretching a thin ligament produces multiple drops, while insufficient stretching of a thick ligament yields none. The optimal regime for single-drop generation lies in between. In the single-drop regime, the drop radius scales as $R \sim a^{2/3} L^{1/3}$, consistent with volume conservation of the stretched ligament. This method enables repeatable generation of single droplets (with <5% variation in $R$) on both still and vibrating baths and of ordered droplet
lattices for pilot-wave hydrodynamics experiments.
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All authors Johnathan Hoggarth, Daniel M. Harris, John W.M. Bush, Bauyrzhan K. Primkulov
Quantum Physics
The Trinity of Markovian Quantum Thermodynamics: Unifying the Axiomatic, Microscopic, and Operational Paradigms
Yutong Luo, Jakub Czartowski, Felix Hubmann et al. (+2 more)
Thermodynamics imposes fundamental constraints on the
evolution of
quantum systems. These constraints and their dynamical consequences have been formulated within distinct paradigms, including axiomatic approaches based on
quantum master equations, microscopic descriptions of open-system dynamics, and operational formulations rooted in resource theories. While each perspective has yielded important insights into thermodynamically consistent
quantum dynamics, their precise relationship has remained unresolved. Here we establish the exact equivalence of these three paradigms in the Markovian regime. We prove that thermal Lindbladians satisfying Markovianity, time-translation
symmetry, and
quantum detailed balance are precisely those admitting a microscopic realisation as an energy-conserving thermal collision model and, equivalently, those generating Markovian thermal operations. This unifies the existing approaches to Markovian
quantum thermodynamics and identifies its dynamical underpinnings. We further provide an explicit microscopic protocol for simulating thermal Markovian processes with controlled finite-time simulation errors. We illustrate its applicability by providing faithful thermal collision-model implementations of a
qubit thermalising in a bosonic environment and of a three-level autonomous thermal machine. In the latter case, the protocol gives rise to a finite-stroke thermal engine that not only reproduces the continuous-time dynamics but also its steady-state thermodynamic performance. As a whole, these results establish a unified foundation for Markovian
quantum thermodynamics, showing that its axiomatic, microscopic, and operational formulations are exactly equivalent and providing a universal protocol for implementing thermal processes and machines.
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All authors Yutong Luo, Jakub Czartowski, Felix Hubmann, Simon Milz, Felix C. Binder
Solar and Stellar Astrophysics
Stellar heavy-element slope index
Gerd Roepke, Friedrich K. Roepke and David Blaschke
The distribution of heavy elements in
stars is described using a phenomenological approach, in which Lagrange parameters related to temperature and the chemical potentials of
protons and
neutrons are introduced within a freeze-out concept. Slope parameters are considered which describe the gross behavior of the distribution of the heavy elements. Universality and deviations from universality are discussed, and various examples are provided. These slope parameters may be of interest for characterizing the conditions under which heavy elements form, but the astrophysical sites where heavy elements are produced remain to be determined.
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High Energy Physics (Phenomenology)
Muon Bremsstrahlung as a New Probe of Dark Sector at Neutrino Experiments
P. S. Bhupal Dev, Bhaskar Dutta, Aparajitha Karthikeyan et al. (+2 more)
We show that
muon bremsstrahlung provides a new production mechanism for light new physics at accelerator
neutrino experiments beyond the
meson kinematic limit. The intense, highly collimated
muon beam produced alongside the
neutrino beam in
meson decays provides a powerful source for the bremsstrahlung production of new physics when it impinges on the beam dump at these facilities. As a
benchmark scenario, we consider a muonphilic scalar coupled to Heavy Neutral
Leptons (HNLs) and show that
muon bremsstrahlung enables the production of HNLs with masses beyond the kinematic reach of
meson decays. Using this new production mechanism and focusing on HNL mixing with tau
neutrinos, we find that the upcoming
neutrino experiments, such as the DUNE Near Detector, can probe previously unexplored parameter space for HNL masses up to $\mathcal{O}(1)~\mathrm{GeV}$ through their decay into pions, $\mu^+\mu^-$, and $e^+e^-$ final states at the detector. The resulting signals exhibit distinctive kinematics, allowing efficient discrimination from
neutrino-induced Standard Model backgrounds. Our results demonstrate that the
muon bremsstrahlung mechanism substantially extends the discovery potential of accelerator
neutrino experiments for HNLs and other dark sector particles.
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All authors P. S. Bhupal Dev, Bhaskar Dutta, Aparajitha Karthikeyan, Mudit Rai, Zahra Tabrizi
Applied Physics · Cross-listed from eess.SY
Induction-heated resonant reactors for electrified thermochemistry
Connor Cremers, Chenghao Wan, Calvin H. Lin et al. (+7 more)
We present induction-heated resonant reactors, a new concept in electrified thermochemistry in which the reactor itself serves as a volumetric electromagnetic resonator heated through resonant wireless power transfer. We use the Swiss roll resonator as a model system and show that it can be designed to support uniform volumetric heating profiles and enhanced heat transfer characteristics, creating opportunities for process intensification in scaled systems. Compared to conventional (i.e., non-resonant) induction heating systems, resonant reactors can achieve exceptionally high system efficiencies through the combination of near-unity power-to-heat efficiencies and low thermal losses, both enabled by the utilization of resonant energy transfer. These concepts demonstrate how the integration of electromagnetic power transduction with thermochemical reaction engineering enables new opportunities for utilizing green electricity in sustainable chemical conversion.
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All authors Connor Cremers, Chenghao Wan, Calvin H. Lin, Zhennan Ru, Kesha Tamakuwala, Ariana B. Hofelmann, Dolly Mantle, Matthew W. Kanan, Juan Rivas-Davila, Jonathan A. Fan
Fluid Dynamics
Lattice Boltzmann Methods for Navier-Stokes Equations in General Orthogonal Coordinates for Efficient Flow Simulations using Nonuniform Clustered Grids
Eman Yahia, Kannan Premnath and William Schupbach
Resolving multiscale fluid flows or boundary layers effectively requires the use of nonuniform meshes with local grid clustering. The standard
lattice Boltzmann method (LBM), a kinetic theory-based approach for computational fluid dynamics, however, is restricted to the use of uniform Cartesian grids. We present new and improved formulations of the LBM that accommodate continuously varying spatial grids via coordinate transformations to simulate the Navier-Stokes equations (NSE) in the general orthogonal coordinates (GOC). They are constructed using a Chapman-Enskog analysis to specify the
equilibrium moments of the distribution functions and the
geometric force terms used in the collision step to be dependent on the local metric factors and their spatial derivatives, along with the density, momentum and their fluxes, and some correction terms related to the normal velocity gradients so as to accurately represent the NSE in the GOC. The resulting GOC-LBM importantly maintains the simplicity of the collide-and-stream approach and is Galilean invariant that is free of the cubic velocity artifacts. Our GOC-LBM is general and modular in that it can be used with any collision model with appropriate modifications to the
equilibria and forcing terms. We present its implementation details for a variety of collision models while the central moments-based model using multiple relaxation times was found to be the most robust in practical implementations. We validate the GOC-LBM through numerical simulations for various
benchmark flow problems. Moreover, we demonstrate significant computational advantages of our approach for a case study on simulating boundary layer flows efficiently that involves coupling the GOC-LBM for the NSE with a new GOC-LB scheme for solving the
magnetic induction equation for magnetohydrodynamics (MHD), and for another case study involving orthogonal curvilinear grids.
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High Energy Physics (Experiment)
Mitigating Detector Ageing Effects with Graph-Based Multi-Modal Track Reconstruction at Belle II
Lea Reuter, Tristan Brandes, Giacomo De Pietro et al. (+1 more)
Large backgrounds that can lead to hardware failures and the degradation of detector gain impact the track finding in the Belle II central drift chamber. These conditions lead to spatially non-uniform and time-dependent inefficiencies, which results in inactive regions and missing hits which challenges conventional tracking
algorithms and necessitate the development of new track finding
algorithms. In this work, we evaluate the performance of our previously developed unified graph neural network (GNN) based track-finding
algorithm under realistic long-term detector ageing conditions. Track finding is formulated as a global relational clustering problem using object condensation, which enables the reconstruction of an unknown and variable number of tracks per event. Using a realistic full detector simulation incorporating beam-induced backgrounds, detector noise, and measured detector ageing effects, we evaluate the tracking performance and compare it to the current Belle II baseline reconstruction. We show that detector degradation can be treated as a domain shift in the observed hit patterns, rather than requiring a fundamentally new reconstruction strategy. After retraining on degraded detector conditions, the GNN-based approach limits the absolute track efficiency loss for uniformly displaced
muons to 14%, compared to 28% for the baseline tracking, while maintaining a track purity of 96%. Under the same conditions, the baseline reconstruction achieves only 90% track purity. These results demonstrate that the unified GNN-based reconstruction provides increased robustness to irregular hit patterns and extended inactive regions, enabling stable tracking performance under long-term detector ageing at Belle II.
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All authors Lea Reuter, Tristan Brandes, Giacomo De Pietro, Torben Ferber
High Energy Astrophysical Phenomena
Multimessenger prospects of quasi-periodic eruptions
Vojtěch Witzany, Alessia Franchini, Matteo Bonetti et al. (+1 more)
Quasi-Periodic Eruptions (QPEs) are recurring soft X-ray transients that may be generated by inspirals of
stellar-mass objects spiraling into supermassive black holes, known as extreme mass ratio inspirals (EMRIs). Independently, EMRIs and the gravitational-wave signals they generate are one of the key targets for the
Laser Interferometer Space
Antenna (LISA). What is the potential of a coincident detection of EMRIs both as a QPE and by LISA? Electromagnetic counterparts to LISA events would provide sky localization, enable standard siren measurements of the Hubble constant and constrain formation mechanisms of the corresponding inspirals. Combined observations would link the accurate measurements of black hole masses and
spins to their
galactic nuclear environments and would thus enable lasting synergies with various observations across the electromagnetic spectrum. However, most of the currently known QPEs imply EMRI orbital periods that place the frequencies of the corresponding gravitational-wave signal out of the LISA sensitivity band. Additionally, the selection biases of QPE detections and the LISA instrument may preclude a coincident detection. Future searches should focus on expanding the QPE catalogs and ultimately hunt for “golden” short-period QPEs that correspond to EMRIs that fall within the LISA band.
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All authors Vojtěch Witzany, Alessia Franchini, Matteo Bonetti, Luca Broggi
High Energy Astrophysical Phenomena
Observations of X-ray quasi-periodic eruptions
Thomas Wevers, Joheen Chakraborty, Erwan Quintin et al. (+2 more)
Quasi-periodic eruptions (QPEs) are a novel class of repeating
nuclear transients, discovered exclusively in the X-ray band to date. Since their initial discovery in 2019, the QPE sample has grown to 13 sources, exhibiting large amplitude, quasi-regular eruptive variability patterns that are distinct from previously known modes of massive black hole variability. In this chapter, we provide a comprehensive overview of their observational characteristics. We review the X-ray spectral and timing properties of QPE eruptions, their long-term
evolution, as well as the underlying quiescent emission, which is well described by thermally dominated, compact
accretion disks. We discuss population-level emerging trends and selection biases, and present an updated census of their host
galaxy properties. We also highlight the growing body of evidence pointing to strong connections between QPEs and
tidal disruption events. Finally, we briefly summarize the key observational constraints on proposed QPE model interpretations, before looking ahead to the observational challenges and opportunities that will shape future progress in understanding this emerging population of
nuclear transients.
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All authors Thomas Wevers, Joheen Chakraborty, Erwan Quintin, Michal Zajaček, Margherita Giustini
Quantum Physics
Spectral amplification for ground-state energy estimation of electronic structure in first quantization
Alicja Dutkiewicz, Alec F. White, Guang Hao Low et al. (+6 more)
We demonstrate an asymptotic gate complexity improvement in first-quantized ground-state energy estimation of electronic structure
Hamiltonians in a plane wave basis by employing the sum-of-squares spectral gap amplification protocol. The improvement relies on identifying a sum-of-squares representation of the
Hamiltonian which provides a lower bound certificate and low cost block encoding that leads to a provably lower
quantum phase estimation gate cost. This is achieved by using a sum-of-squares operator generated by the total charge density operator resulting in a block encoding normalization improvement of $\lambda = \mathcal{O}\left(\eta\Delta^{-1.5}+\eta^{1.5}\Delta^{-1} \right)$ compared to prior work $\lambda = \mathcal{O}(\eta\Delta^{-2}+\eta^2\Delta^{-1})$ where $\eta$ is the number of electrons and $\Delta$ is the simulation grid spacing. The asymptotic reduction in block encoding normalization and similar block encoding costs to prior work is demonstrated to reduce resource estimates for materials and chemical systems by a factor of $2 - 44\times$ corresponding to the lowest cost estimates for ab initio materials simulation.
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All authors Alicja Dutkiewicz, Alec F. White, Guang Hao Low, A. Eugene DePrince III, Matthew P. Harrigan, Marika Kieferova, Ryan Babbush, Dominic W. Berry, Nicholas C. Rubin
Astrophysics of Galaxies
Non-Thermal Physics Drives Compact, Self-Regulated Galaxy Morphologies at Cosmic Dawn
Michelle S. Park, Sergio Martin-Alvarez and Risa H. Wechsler
James Webb Space
Telescope (JWST) has discovered unexpectedly bright, rapidly growing
galaxies in the early universe, which were not predicted by most previously existing
galaxy formation models. Using synthetic JWST observations of the Azahar simulation suite, we show that comprehensive non-thermal physics ("Full-Physics") produces compact, self-regulated
galaxies that match observations from $z = 12$ to $z = 3$. This model also produces broad surface brightness distributions, where the bright end is dominated by compact sizes and bursty
star formation. This compact starburst scenario naturally explains the detection of bright $z > 10$
galaxies in flux-limited surveys. By contrast, a model with standard hydrodynamics yields systems that are smaller and more concentrated than current data, while a model with calibrated
supernova feedback produces unphysically large systems nearly twice the size of those observed. At lower masses ($\mathrm{M}_{*} < 10^{8}\,\mathrm{M}_{\odot}$), the Full-Physics model predicts sizes that are smaller than can be resolved with JWST, consistent with extrapolations from observations of higher-mass systems. Future observations with higher resolution could resolve this population and elucidate the physics driving the formation of the first
galaxies.
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High Energy Physics (Phenomenology)
Multiboson Signatures of Doubly Charged Scalars at a Same-Sign Muon Collider
Mariana Frank, Benjamin Fuks, Chayan Majumdar et al. (+1 more)
We investigate the sensitivity of a same-sign $\mu^+\mu^+$
collider to doubly charged scalars in the Type-II seesaw framework, focusing on the regime in which the doubly charged scalar decays dominantly into same-sign $W$-
boson pairs. Motivated by the $\mu$TRISTAN proposal, for a
benchmark we consider a degenerate triplet spectrum at a center-of-mass energy of $2~{\rm TeV}$ and an integrated luminosity of $1~{\rm ab}^{-1}$. The signal process is studied in the fully hadronic $W$-decay mode, leading to a characteristic $\mu^+\mu^+ + 8j$ final state. We develop a cut-based analysis based on high jet multiplicity and global hadronic $W$ reconstruction, and then improve its sensitivity with a multivariate strategy exploiting reconstructed $W$ observables, global event kinematics, multi-
boson variables and spectator-
muon information. The best-performing setup reaches a $2\sigma$ sensitivity level for doubly charged scalar masses up to $425-430~{\rm GeV}$, extending the cut-based reach by a few tens of GeV. This indicates an improvement over the current LHC coverage, while also providing an independent probe based on a qualitatively different production mode and
collider environment.
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All authors Mariana Frank, Benjamin Fuks, Chayan Majumdar, Supriya Senapati
Earth and Planetary Astrophysics
Very Large Telescope observations of interstellar comet 3I/ATLAS III: High-resolution monitoring of CN and forbidden oxygen emission across the perihelion passage with ESPRESSO
Baltasar Luco, Thomas H. Puzia, Rohan Rahatgaonkar et al. (+2 more)
We characterize in 3I/ATLAS the heliocentric
evolution of the CN production rate and the forbidden [OI] emission, describe the broader emission line inventory, and release the analysis tools and reduced data products to the community. We obtained high-resolution spectroscopy of 3I/ATLAS with VLT/ESPRESSO ($r_{\rm h}\!=\!1.67\!-\!2.45$ au). The CN production rates were derived by fitting the $B^2\Sigma^+\!-\!X^2\Sigma^+$ band using CometSpec, a publicly released Python package for flexible fluorescence modeling. The three forbidden [OI] lines were modeled to derive the green-to-red (G/R) flux ratio and a $\rm CO_2 / H_2O$ proxy. We fit $\text{Q}_{\rm CN}=a\,(r_{\rm h}/1\text{ au})^{\,b}$ to the production rate versus heliocentric distance relation. The pre-perihelion CN power-law index is $b_{\rm pre}\!=\!-4.62^{+1.25}_{-1.22}$, which is within the range observed for
Solar System comets. The CN residuals about the smooth model show substantial scatter that we attribute to a combination of systematics and possible physical drivers that the current cadence cannot disentangle. The G/R ratio decreases from $\sim\!0.42\!\pm\!0.14$ at $r_{\rm h}\!\simeq\!2.4$ au to $\sim\!0.114\!\pm\!0.004$ near perihelion. The $\rm CO_2 / H_2O$ proxy spans $\sim 0.06 - 1.06$ and is comparable to the values reported by Subaru/HDS and SPHEREx and to those measured for 2I/Borisov. We additionally identify NiI and FeI and report post-perihelion production rates for $\rm C_2$ and CH. Our high-resolution monitoring of 3I/ATLAS reveals a $\rm CO_2$-rich coma that becomes progressively $\rm H_2O$-dominated near perihelion. Together with the public release of CometSpec and the reduced data, these results provide an empirical reference and a methodological framework for the next generation of interstellar object monitoring campaigns.
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All authors Baltasar Luco, Thomas H. Puzia, Rohan Rahatgaonkar, Juan Pablo Carvajal, Prasanta K. Nayak
Cosmology and Nongalactic Astrophysics
Tunnelling out of Starobinsky inflation: Raising the spectral tilt
Jose A. R. Cembranos, Jesús Luque and Javier Rubio
We propose a hybrid realization of Starobinsky inflation in which the inflationary epoch ends through
vacuum decay. The model consists of an effective two-field system with a metastable Starobinsky branch shifted with respect to the true one. During the observable stage, the inflaton slow-rolls along the false branch, until a first-order phase transition in an orthogonal direction connects it to the true branch and ends inflation abruptly. This old-inflation-like exit skips the last part of the would-be Starobinsky trajectory. As a result, the
Cosmic Microwave Background pivot scale exits the Hubble radius further from the minimum of the false branch than in ordinary Starobinsky inflation, raising the scalar spectral tilt $n_s$ while preserving the characteristic small tensor-to-scalar ratio. This provides a simple way of moving Starobinsky inflation towards the high-$n_s$ region favoured by recent ACT-related combinations. The same
vacuum transition leaves a
stochastic gravitational-wave relic whose peak frequency is controlled by the tunnelling timescale and the subsequent reheating history.
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Mesoscale and Nanoscale Physics
Dynamical unmasking of $p$-wave magnetism by ac spin and dc orbital polarizations
Yantao Li, Jacob Linder and Pavlo Sukhachov
Odd-parity magnets have strong
spin polarization in momentum space but no net magnetization, making their
spin texture hidden from conventional magnetometry. We show that a monochromatic electric field dynamically lifts this cancellation in a $p$-wave magnet. Within each drive cycle, the field produces a net ac
spin polarization linear in the driving field whose interband component is resonantly enhanced at the nonrelativistic exchange gap. Because this polarization oscillates at the drive frequency, it vanishes upon period averaging. The orbital channel follows a different hierarchy: its linear response cancels in momentum space, whereas interband coherence produces a rectified dc orbital polarization at second order when the field has components parallel and transverse to the $p$-wave
spin-splitting direction. Together, the ac
spin and dc orbital responses dynamically unmask $p$-wave magnetism without requiring any
spin-orbit coupling.
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Astrophysics of Galaxies
The first three-dimensional map of thermal phases in the local interstellar medium
Jonathan Shelest, Shmuel Bialy, Troy A. Porter et al. (+3 more)
The thermal state of interstellar gas controls whether it remains warm and diffuse or cools into dense clouds. Twenty-one centimetre observations have established a statistical picture of neutral-gas phases, but their three-dimensional architecture has not previously been mapped. Here we present $\mathcal{P}_{\rm 3D}$, a three-dimensional reconstruction of thermal phase in the local interstellar medium (ISM), covering a 1 kpc-diameter region centred on the Sun and sampled on a 2 pc Cartesian grid. $\mathcal{P}_{\rm 3D}$ combines high-resolution 3D maps of
dust extinction and interstellar far-ultraviolet radiation with a neutral-ISM thermochemical model. The reconstruction reveals cold clouds surrounded by thermally unstable envelopes and embedded in a pervasive warm phase. Within $|z| \leq 150$ pc of the
Galactic midplane, $\sim$41 % of the
dust-traced neutral mass is thermally unstable, implying phase cycling on a timescale of $\sim$2.9-6 Myr. Yet the cold phase has a narrow density distribution, consistent with internal Mach numbers that are transonic at most ($\mathcal{M}_s \lesssim 1.5$). Together, these findings favour a dynamically cycling multiphase interstellar medium and motivate reassessing
star-formation models that assume a single-phase, strongly supersonic cold-gas density field.
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All authors Jonathan Shelest, Shmuel Bialy, Troy A. Porter, Mark Wolfire, Matan Berko, Margarita Grinberg
Quantum Physics
The Paradox of the Third Particle is classical
Ladina Hausmann and Renato Renner
The Paradox of the Third Particle arises when particles are described relative to one of them serving as a reference frame. Although it is typically attributed to
quantum superpositions, we show that the paradox and its ramifications$\unicode{x2014}$such as the relativity of subsystems$\unicode{x2014}$already occur classically. In light of this insight, we establish a no-go
theorem that holds whenever physical subsystems, whether classical or
quantum, are used as reference frames: if one demands that frame transformations be information-preserving, then it is impossible to meaningfully partition the world into subsystems, like individual particles, from the perspective of each frame.
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Statistical Mechanics
Fragmented ETH and Ensemble Inequivalence
C. L. Sriram, Soumya Kanti Pal and Lea F. Santos
We investigate thermalization in finite
quantum systems with strong long-range interactions. Nearly conserved quantities inherited from the fully connected limit organize the
Hilbert space into weakly coupled sectors and split the many-body spectrum into energy bands. Despite the resulting breakdown of global ergodicity,
quantum chaos develops within individual energy bands, enabling the definition of microcanonical ensembles within the bands. This supports a band-resolved formulation of thermalization, which we term fragmented eigenstate thermalization hypothesis (fETH). Unlike conventional ETH, finite-size scaling in fETH obeys a
symmetry-imposed selection rule that restricts which system sizes can be compared. This band-resolved description has consequences for
equilibrium statistical mechanics. While microcanonical ensembles remain confined to a single band, canonical ensembles mix different bands. This mismatch explains ensemble inequivalence without invoking
equilibrium phase transitions. Our results apply broadly to
Hamiltonians near a fully permutation-symmetric limit.
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High Energy Physics (Theory)
Non-abelian asymmetric orbifolds with vanishing one-loop vacuum energy
Bernardo Fraiman, Vittorio Larotonda and Michelangelo Tartaglia
We present a partial classification of four-dimensional, non-supersymmetric Type II toroidal orbifolds with non-abelian point groups of rotations, and vanishing
vacuum energy at one loop in string perturbation theory. The classification is complete within a class of such orbifolds with the restriction that the point group only acts on a $T^5$ inside the full internal $T^6$. By studying their decompactification limits along the leftover $S^1$, we see that the 17 solutions we find can alternatively be obtained as Scherk–Schwarz compactifications of some parent asymmetric orbifold. Along the way, to ensure the absence of anomalies, we compute bordism groups $\Omega_3^{Spin(BG)}$ for a variety of non-abelian crystallographic groups $G$.
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