Strongly Correlated Electrons
Algebraic Diagrammatic Construction of the Multichannel Dyson Equation
Thibault Demartini, J. Arjan Berger, Guillaume Blanchon et al. (+4 more)
The multichannel Dyson equation (MCDE) was recently introduced as a new approximation scheme to compute the one-body Green function in many-body systems, as reported by Riva et al. in Physical Review Letters, volume 131, article 216401, published in 2023. The physical content of this novel approximation scheme is further clarified by recovering it from an extended version of the algebraic diagrammatic construction (ADC) truncation scheme. It is thus demonstrated that the MCDE approximation lies in between the so-called ADC(2) and ADC(3) truncations of the dynamical self energy. Building on this clarification, the MCDE approximation is tested on the periodic one-dimensional Hubbard model with 4, 6, and 8 site
lattices and shown to deliver an improved treatment over ADC(2) of both the quasiparticle peaks and the so-called satellites in the spectral strength distribution.
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All authors Thibault Demartini, J. Arjan Berger, Guillaume Blanchon, Thomas Duguet, Denis Lacroix, Pina Romaniello, Vittorio Somà
Optics
Signature of Magnon-Raman Phonon-Polariton Condensation in a Cavity via Transverse Pumping
Subrata Chakraborty and Shishir Kumar Pandey
Polaritons—hybrid light-matter quasiparticles—provide a versatile platform for dynamically controlling a wide range of condensed matter systems. While conventional polaritonic platforms rely on direct dipole coupling, controlling dipole-forbidden or Raman-active
lattice and
spin excitations remains challenging due to optical selection rules and the limitations of THz cavities. Here, we propose a theoretical platform for realizing a continuous-wave
magnon–Raman
phonon–polariton condensate. By
embedding a
magnetic medium hosting strongly coupled
magnon and Raman-active
phonon (MRP) modes inside an optical microcavity under continuous-wave transverse
laser pumping, we derive the stationary-state phase diagram and demonstrate the emerging signature of distinct MRP condensation phases under critical conditions. Furthermore, since the bare
magnon frequency is tunable via an external
magnetic field, we show that the transverse pump frequency and the external
magnetic field-dependent
magnon simultaneously as highly flexible control parameters for exploring and controlling macroscopic
quantum phenomena at the interface of cavity
quantum optics,
lattice dynamics, and
quantum magnetism.
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Materials Science
Transient Detour and Cooperative Oxygen Exchange in the Polarization Switching of Ferroelectric Hf0.5Zr0.5O2
Ryotaro Sahashi, Po-Yen Chen and Teruyasu Mizoguchi
Hafnium zirconium
oxide (HZO) has attracted significant
attention as a core material for next-generation non-volatile
memories due to its excellent ferroelectricity in the ultra-thin film regime and its CMOS process compatibility. However, the exploration of its polarization switching mechanism has predominantly relied on static energy barrier analyses, leaving the transient bond formation and cooperative dynamic mechanisms under actual electric field driving unresolved. In this study, we performed Electric-Field-Induced MD simulations on a defect-free ideal HZO
lattice using a fine-tuned machine learning force field (MACEField). As a result, we successfully reproduced the P-E hysteresis loop dynamically and demonstrated that the polarization switching in HZO is driven not by conventional simple displacement models (S:N/S:T models), but by the dynamic mutual exchange of 3-coordinated oxygen (O3c) and 4-coordinated oxygen (O4c). Analysis of the oxygen atom displacement trajectories revealed that this pathway is accompanied by a unique "detour" behavior originating from transient cation-oxygen bond formation. Furthermore, we identified an "internal self-compensation mechanism" in which the local volumetric expansion and contraction accompanying the coordination number changes are effectively offset within the
cell. These findings provide, from a dynamic perspective, a microscopic physical origin of for HZO's exceptional ability to sustain stable polarization switching without macroscopic strain, a property that has long distinguished HZO from conventional perovskite ferroelectrics yet lacked atomistic explanation. These findings suggest that preserving the integrity of cooperative O3c/O4c exchange pathways, rather than minimizing individual atomic displacements, is the key design principle for endurance and scalability in next-generation ferroelectric
memories.
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Materials Science
Percolating Multifractal Domains at a Polymorphic Phase Boundary
Yuan-Jinsheng Liu, Xu Tian, Jiahui Zhai et al. (+1 more)
Giant piezoelectricity in ferroelectrics is commonly associated with phase-boundary instabilities, among which the polymorphic phase boundary (PPB) is a prominent example conventionally attributed to the coexistence of ferroelectric phases. Here, using large-scale molecular dynamics simulations of the lead-free (K,Na)NbO3-(Bi,Na)ZrO3 solid solutions, we show that the PPB hosts a percolating multifractal polar domain which governs the dielectric and piezoelectric responses. By quantifying the global fractal dimension and multifractal spectrum width of this polar network, we identify fractal connectivity and multiscale heterogeneity as microstructural order parameters for the PPB. The maximum reversible piezoelectric response occurs when the fractal-domain volume fraction approaches the three-dimensional percolation threshold, suggesting that near-critical polar connectivity enables
giant reversible electromechanical coupling. In this mechanism, the fractal backbone preserves polar
memory and provides the restoring force required for reversibility, while the surrounding nonfractal regions supply the polar compliance needed for large polarization rotation and strain. These results establish percolating multifractal polar domains as a microscopic mechanism for PPB-enhanced piezoelectricity and suggest fractal connectivity as a design parameter for high-performance piezoelectrics.
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All authors Yuan-Jinsheng Liu, Xu Tian, Jiahui Zhai, Shi Liu
Soft Condensed Matter
Mode-Resolved Light Scattering Recovers Polymer Thermodynamics in Solutions with Trace Large-Mass Scatterers
Noriaki Mizumoto, Takashi Yasuda, Hiroshi Hinou et al. (+1 more)
Light scattering provides direct access to
polymer conformations and thermodynamics. However, trace large-mass scatterers such as aggregates and nanobubbles form unavoidably in
polymer solutions and dominate the scattered intensity, obscuring the intrinsic
polymer signal. We demonstrate that resolving the static scattering intensity by molecular mobility cleanly separates the
polymer and large-scatterer contributions. Applying this mode-resolved analysis to aqueous poly(ethylene glycol) solutions, we isolate the
polymer scattering even when these scatterers account for more than 90 % of the total intensity. The resolved
polymer intensity recovers the universal osmotic equation of state from the dilute to the semidilute regime over 288 to 358 K. This approach establishes a reliable basis for measuring the thermodynamics of interacting macromolecules in solutions where irreproducible large-mass scatterers have precluded quantitative analysis.
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All authors Noriaki Mizumoto, Takashi Yasuda, Hiroshi Hinou, Xiang Li
Accelerator Physics
Cherenkov Diffraction Radiation Interferometry for Beam Divergence Diagnostics
Artem Novokshonov
Cherenkov radiation (ChR) is widely used in charged-beam diagnostics, including bunch-length measurements and beam-loss monitoring. Synchrotron radiation (SR) interferometry is a well-established technique for measuring beam size. This work combines these approaches by proposing a ChR-based interferometric method for measuring beam divergence.
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High Energy Physics (Phenomenology)
Particle Production via Rippled Bubble Walls
Ryusuke Jinno, Shota Nakagawa, Yuichiro Nakai et al. (+1 more)
We investigate non-thermal particle production during first-order phase transitions in the presence of ultra-relativistic thick bubble walls with non-trivial internal structure. Extending the framework of bubble-expansion particle production, we consider bubble walls containing multiple ripples and study how such spatial modulations affect the production of heavy particles coupled to the order parameter field. By modeling an oscillatory thick-wall profile, we derive the transition probability for particle splitting processes in the wall background, and identify a new contribution associated with momentum transfer from the wall microstructure. In addition to the conventional channel, we find an enhanced production mode arising from resonant momentum exchange with the ripples. For sufficiently large numbers of ripples, the new contribution can dominate the production rate and significantly increase the abundance of particles much heavier than the phase-transition scale. Our results demonstrate that the internal structure of expanding bubble walls can play an important role in particle production and should be taken into account when assessing the cosmological implications of strongly first-order phase transitions.
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All authors Ryusuke Jinno, Shota Nakagawa, Yuichiro Nakai, Yaoduo Wang
Superconductivity
DC Josephson transport in a three-terminal Yu-Shiba-Rusinov system
Subrata Chakraborty
Scanning tunneling microscopy (STM) of
magnetic adatoms on superconducting surfaces has established Yu-Shiba-Rusinov (YSR) states as a versatile platform for studying
magnetic-superconducting interactions and phase-coherent
quantum transport. Here, we investigate nonreciprocal supercurrent transport in a three-terminal Josephson junction comprising three BCS
superconductors (`A', `B' and `C'), each coupled to a
magnetic impurity hosting a pair of YSR states. Treating terminals `A' and `C' as primary transport electrodes and terminal `B' as a phase-control node, we demonstrate field-tunable nonreciprocal supercurrent between the primary electrodes. This effect requires both: the control terminal and broken particle-hole
symmetry at least in one
impurity attached to a primary electrode. Without the control terminal we show that the supercurrent remains reciprocal. Our results establish multi-terminal YSR junctions as a promising platform for engineering nonreciprocal superconducting transport and
symmetry-breaking phenomena at the atomic scale.
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General Relativity and Quantum Cosmology
Constraining deviations from the Teukolsky equation with GW250114
Sebastian H. Völkel and Nicola Franchini
The recent gravitational-wave detection GW250114 by the LIGO-Virgo-KAGRA (LVK) Collaboration provides unprecedented precision for testing general relativity (GR) through black hole ringdowns. In this study, we provide the first bounds on theory-agnostic deviations from the Teukolsky equation as described by the beyond-Teukolsky formalism. It directly connects deviations in the perturbation equations on the level of the effective potential in the Teukolsky equation with changes in the quasinormal mode (QNM) spectrum. We incorporate information on the final mass and
spin from a full LVK inspiral-merger-ringdown analysis as parametrized priors in our analysis, reflecting theoretical uncertainties. Using publicly available LVK posterior information on agnostic damped sinusoid parameters, we then demonstrate how much beyond-Teukolsky potentials can be constrained. The high signal-to-noise ratio (SNR) allows us to avoid the expensive full
Bayesian analysis of all parameters and to work directly with a simplified likelihood for the fundamental QNM only. This strategy is promising for future events with even higher SNR and allows, in principle, for a quick and simple test of theories beyond GR without performing the full data analysis procedure. We report that current bounds on deviation parameters are in agreement with the Teukolsky equation.
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Astrophysics of Galaxies
An Enhanced Catalog of Gaia DR3 Galaxy Candidates with Spectroscopic and Machine-Learning Photometric Redshifts
Junghyun Hwang and Ho Seong Hwang
We present an updated
galaxy catalog based on the
Gaia Data Release 3 (DR3)
Galaxy Candidates table, augmented with both spectroscopic and machine-learning based photometric
redshift estimates. While the original catalog of
Gaia DR3
galaxy candidates provides an unprecedented all-sky sample of extragalactic sources, its scientific utility for extragalactic and cosmological studies has been limited by the absence of
redshift information and by its relatively low source purity. To address these limitations, we cross-match the catalog of
Gaia DR3
galaxy candidates with existing spectroscopic
redshift catalogs including DESI, SDSS, 2MRS, and NED. For sources without spectroscopic measurements, we compute photometric
redshifts using a Multiple-Bin Regression Neural Network (MBRNN) machine-learning model. The input features for this model are drawn from a newly constructed multiwavelength catalog that combines
Gaia DR3 measurements with 2MASS and unWISE photometry, as well as shape parameters, QSO classification flags, and extinction values. The model is trained and validated using the spectroscopic subsample. As a result, spectroscopic
redshifts are assigned to 24.5% of the catalog sources, while photometric
redshifts are provided for the remaining objects. The MBRNN model achieves improved
redshift accuracy and precision compared to previously published photometric
redshift estimates based on
Gaia data alone. In addition to
redshift values, we provide a score quantifying the likelihood that a given source represents a statistical outlier. The resulting catalog significantly enhances the scientific value of the
Gaia DR3
galaxy candidates sample and provides a valuable resource for large-scale extragalactic and cosmological studies.
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Plasma Physics
One dimensional high-order moment models with realistic collisions for nonequilibrium ion transport in weakly ionized plasmas
Anatole Berger and Alejandro Alvarez Laguna
Ion-neutral collisions are fundamental in the transport of partially ionized
plasmas. When collisional scales are comparable to the system scales or the electric field is strong, nonequilibrium conditions for the ions arise that are beyond classical transport models due to large drifts, strong heat flux, and temperature anisotropy. In this paper, we propose the resolution of non-linear high-order moment closures for simulating nonequilibrium ion dynamics in one-dimensional weakly ionized
plasmas. We compare a four-moment anisotropic Maxwellian model (mass, axial momentum, and axial and perpendicular energies), a five-moment
hyperbolic quadrature-based model (first five axial moments), and a novel six-moment
hyperbolic quadrature-based model (first five axial moments + perpendicular energy). We derive analytical collision source terms from the Boltzmann operator for ion-neutral scattering with arbitrary differential cross sections. This formulation generalizes the Chapman-Cowling theory for arbitrary drift velocities, temperature anisotropies, and heat flux, ensuring strictly realizable distributions. The models are validated via non-linear simulations benchmarked against kinetic solutions for argon
plasmas with realistic cross sections (0.05-500 mTorr). We test a bounded
plasma between floating walls and a direct-current discharge. The six-moment model robustly captures ion dynamics, particularly under strong nonequilibrium, where anisotropy and heat flux are non-local. It reconstructs the distribution function with high fidelity, without noise, and at a cost comparable to fluid models in a self-consistent manner.
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Quantum Physics
QKD-Integrated Quantum Noise Stream Cipher: An Overview
Umesh Kumar Chandra, Avinash Kote, Neha Pathania et al. (+4 more)
Quantum Noise Stream Cipher (QNSC) has emerged as a physical-layer encryption technique that exploits
quantum noise and non-orthogonal coherent-state modulation to secure optical communication. However, the security of QNSC relies exceedingly on the secrecy and freshness of its seed key.
Quantum Key Distribution (QKD), on the other hand, provides information-theoretically secure key exchange rooted in the laws of
quantum mechanics. The convergence of these two paradigms, i.e., integrated QKD-QNSC architectures, offers a compelling solution to each of their limitations. In such integrated systems, QKD continuously supplies and refreshes the secret seed key that governs QNSC modulation. Thus, governing a unified security framework that couples provably secure key establishment with high-speed
quantum-enhanced physical-layer encryption. This work presents a comprehensive review of QNSC systems, examining their operating principles, security models under various attacks, and their integration with QKD systems. We analyze the security interplay between the key generation and encryption layers and survey experimental demonstrations and architectural progress toward practical deployment. Furthermore, we identify the open challenges and future research directions that must be addressed to realize fully integrated,
quantum-secured optical communication networks at a practical scale.
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All authors Umesh Kumar Chandra, Avinash Kote, Neha Pathania, Ken Tanizawa, Fumio Futami, Prem Kumar, Sandeep Singh
Nuclear Theory
Intruder-driven mirror energy differences between $^{29}$Cl and $^{29}$Mg studied with antisymmetrized molecular dynamics
Dae Ik Kim, Masaaki Kimura, Chang-Hwan Lee et al. (+1 more)
To clarify the mirror energy differences (MEDs) of the
proton-unbound
nucleus $^{29}$Cl and their microscopic origins, we investigate the low-lying states of the $^{29}$Cl-$^{29}$Mg mirror pair using antisymmetrized molecular dynamics. The calculation reasonably reproduces the normal and intruder states of $^{29}$Mg, while suggesting alternative
spin-parity assignments for $^{29}$Cl. The $1/2^+$ and $3/2^+$ states are predicted to form a nearly degenerate ground-state doublet with a small MED because of their similar intrinsic structures. In contrast, the $3/2^-$ and $7/2^-$ intruder states exhibit large negative MEDs and are assigned to the observed resonances at approximately 500~keV and 1.1~MeV, respectively. Their large MEDs originate from the reduced Coulomb energies associated with the stronger deformation and spatially extended
proton distributions in the intruder configurations.
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All authors Dae Ik Kim, Masaaki Kimura, Chang-Hwan Lee, Youngman Kim
Instrumentation and Methods for Astrophysics
Impact of microlens shape on the performance of Laser Guide Star wavefront sensors for ELT-class telescopes
Paul Rouquette, Benoit Neichel, Cédric Taisir Heritierc et al. (+4 more)
Laser Guide
Star (LGS) adaptive optics systems on extremely large
telescopes (ELTs) rely on Shack-Hartmann wavefront sensors (SHWFS) equipped with large-format microlens arrays. Manufacturing imperfections in the microlens surface profile degrade spot quality and reduce centroiding accuracy, yet this effect is rarely quantified in the context of full AO system performance. This paper presents a comprehensive characterization of the impact of microlens shape on LGS wavefront sensing, using the MORFEO-HARMONI LGS wavefront sensor design as the primary test case, results are directly applicable to any ELT-class or future large-
telescope LGS instrument, including systems on the GMT and TMT. Starting from interferometric surface profile measurements of prototype microlenses, we derive the induced phase errors and compute the degradation of center-of-
gravity (CoG) spot detection accuracy as a function of LGS elongation and flux. A real microlens degrades CoG variance by a factor of 1.8 to 2.4 compared to an ideal lens, equivalent to requiring approximately twice the
photon flux to maintain the same measurement accuracy. This effect is shown to decrease with increasing LGS elongation, and to improve with higher microlens sag. The per-subaperture flux-loss model is then propagated into tomographic AO end-to-end simulations, where measurement redundancy across multiple LGS and MMSE reconstructor weighting partially mitigate the penalty, reducing the effective Strehl ratio flux loss to factors of 1.25-1.4. Experimental validation is provided with the LGS wavefront sensor optical bench prototype at LAM, which also enables full-array characterization in a single measurement. The methodology is broadly applicable to any Shack-Hartmann system operating in a low-flux regime.
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All authors Paul Rouquette, Benoit Neichel, Cédric Taisir Heritierc, Pierre Jouve, Anne Costille, Kjetil Dohlen, Thierry Fusco
Instrumentation and Methods for Astrophysics
Towards an Extended VLTI: Turbulence Characterization for Kilometer-Scale Optical Links at Paranal
B. Neichel, T. Pichon, G. Bourdarot et al. (+10 more)
Future extensions of the VLTI aim to push infrared interferometry toward kilometer scale baselines, enabling angular resolutions of a few tens of micro-arcseconds. A first step would couple a new
telescope on the VISTA platform to the existing VLTI infrastructure, creating a 1.4 km baseline at Paranal. Among the possible beam-transport solutions, direct free-space transmission with adaptive-optics (AO) pre-compensation, inspired by Free-Space Optical (FSO) communications, offers an attractive combination of spectral flexibility, moderate cost, and preservation of field information. We present a preliminary AO dimensioning study, including fitting error,
photon noise, anisoplanatism, and scintillation, showing that moderate-order correction (around 10x10 actuators) may be sufficient, but that performance depends critically on the poorly known
turbulence distribution along the horizontal path. We therefore propose a dedicated
turbulence-monitoring experiment across the VISTA-VLTI line of sight, using two 30-50 cm
telescopes equipped with calibrated light sources. The experiment combines a wide-field Shack-Hartmann sensor for tomographic reconstruction of the
turbulence volume with an event-based (neuromorphic) camera capable of capturing fast, anisotropic
turbulence at microsecond timescales. The resulting
dataset will provide the first systematic characterization of kilometer-scale horizontal
turbulence at Paranal, paving the way toward an extended kilometer-baseline VLTI.
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All authors B. Neichel, T. Pichon, G. Bourdarot, D. Perez, E. Vera, V. Chambouleyron, T. Fuscod, C.-T. Heritier, F. Eisenhauer, N. Vedrenne, D. Delamoye, F. Glasser, S. Esposito
Adaptation and Self-Organizing Systems
Determining Critical Temperature Differences of Low-Temperature-Differential Stirling Engines: Nonlinear Dynamics Approach
Momoko Amemiya and Yuki Izumida
While the low-temperature-differential (LTD) Stirling engines are innovative engines that can operate with low temperature differentials in our daily life, the problem of determining the critical temperature differences below which the engine ceases to rotate remains unexplored. In this study, we solve this problem using a nonlinear dynamics approach. We derive the self-consistent equations that determine the critical temperature differences as homoclinic bifurcation points of a dynamical model of the LTD Stirling engines. The solutions of the self-consistent equations reveal a combination of parameters that determines the critical temperature differences. This enables us to establish the fundamental design principles for improving the performance of the LTD Stirling engines beyond empirical designs.
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Instrumentation and Methods for Astrophysics
HARMONI@ELT: instrument design, performance, and science capabilities
B. Neichel, J. Dunlop, S. Chittick et al. (+17 more)
HARMONI is the integral field spectrograph for the Extremely Large
Telescope (ELT). Designed as the primary workhorse near-infrared spectrograph of the ELT, it will deliver spatially resolved spectroscopy at diffraction-limited angular resolution over the wavelength range 0.75 - 2.4 um, addressing science questions ranging from the characterization of
exoplanet atmospheres to the internal kinematics of
galaxies at the epoch of reionization. This paper presents the current status of the HARMONI project following its recent rescope, describing the new instrument architecture, its key subsystems, and the three adaptive optics modes (Single Conjugate AO (SCAO), Multi-Conjugate AO (MCAO) provided by MORFEO, and High Contrast AO (HCAO)). We present the top-level technical specifications and the expected on-sky performance in terms of Strehl ratio, PSF FWHM, sky coverage, sensitivity, and astrometric accuracy. We describe the new project organization, with a new leadership and Project Management Office (PMO), and provide an update on the project schedule and the path toward instrument delivery.
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All authors B. Neichel, J. Dunlop, S. Chittick, D. Le Mignant, M. Swinbank, A. de Lorenzo-Caceres, W. Taylor, M. Tecza, B. Johnson, A. Costille, N. Bouche, A. Delsanti, T. Morris, J. Piqueras Lopez, B. Garcia, M. Mateo, A. Carlotti, Dan Dickens, Edgard Castillo Dominguez, the HARMONI Consortium
High Energy Physics (Theory)
Static topological dilatonic black hole with multiple horizons and its thermodynamics
M. M. Stetsko
We obtain a static topological charged black hole solution within Einstein-dilaton theory with nonlinear electromagnetic field represented by an infinite series over Maxwell field invariant. In contrast with standard Einstein-Maxwell-dilaton (EMD) theory where the black hole might have no more than two horizons, the nonlinear generalization might give rise to a solution with arbitrary number of horizons. We examine energy conditions and show that for the nonlinear electromagnetic field itself all the energy conditions are fulfilled outside of the black hole, whereas for the dilaton field the only condition which is not violated outside is the Null Energy Condition (NEC). We also study thermodynamics of the black hole and show that the thermal behaviour of the solution is considerably richer than for its standard EMD cousin. To have complete description of the thermodynamics we also use the Euclidean method, which allows us to consider the so-called Grand Canonical and Canonical Ensembles. The results obtained by different approaches show their consistency. The Euclidean description naturally allowed us to consider global stability, which is shown to have some common features with standard EMD solution, or even Reissner-Nordström black hole. But there some new peculiarities caused by the nonlinear field, namely we might have additional stable phases and a triple point. To examine near critical behaviour we consider the extended phase space approach, where the cosmological constant is supposed to be a thermodynamic variable. Making use of the extended formalism we also obtain the Smarr relation.
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High Energy Physics (Theory)
Massive and massless particles in Mielke–Baekler geometries
Carles Batlle, Roberto Casalbuoni, Daniele Dominici et al. (+2 more)
The Mielke–Baekler geometries are three-dimensional reductive homogeneous spacetimes together with a choice of invariant connection which is compatible with a lorentzian metric. The spacetimes generalise Minkowski and (anti)de~Sitter spacetimes in that the invariant metric connection can have torsion, a peculiarity of three dimensions. Using coadjoint orbits and the techniques of nonlinear realisations, we construct worldline actions for massive and massless spinning particles moving in these spacetimes. We pay particular
attention to the so-called teleparallel branch, in which the
curvature of the invariant connection vanishes. Apart from the trivial Minkowski case, this singles out anti-de~Sitter spacetime, as the only of these lorentzian
manifolds admitting an invariant Weitzenböck connection; that is, a flat connection with torsion. The introduction of a Wess–Zumino term describing
spin has, as a main consequence, the appearance of dynamical sectors (denoted “regular” and “critical”), with a different number of physical degrees of freedom. In particular, in the massive case, we discuss the formulation of the dynamics in terms of either the Weitzenböck or the Levi-Civita connection, and the emergence of a Papapetrou-type forcing term in the critical sector. For the massless particle we study the Noether
symmetries of the action, which, for the spinless case, include the conformal transformations. For nonzero
spin, only the Killing subset survives as genuine Noether transformations in the regular sector, while in the critical sector any conformal Killing contribution can be set to zero by a gauge transformation.
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All authors Carles Batlle, Roberto Casalbuoni, Daniele Dominici, José Figueroa-O'Farrill, Joaquim Gomis
Strongly Correlated Electrons
Quantum Geometry-Driven RKKY: From Flat to Dispersive Bands
Zhenggang Zhou, Chuang Li and Lun-Hui Hu
In flat-band systems,
quantum metric bounds physical observables like superfluid weight and coherence length, suggesting a single
geometric scale for spatial correlations. Here, we show that the RKKY exchange in an isolated filled flat band can violate this expectation. With the intraband channel absent, the exchange proceeds via virtual interband transitions across the gap; the kernel becomes the inverse-gap-weighted trace product of the real-space flat-band projector and empty-band projectors. Because the corresponding momentum-space projectors are analytic, the kernel decays exponentially, with a decay length $\xi_\text{RKKY}$ set by the closest singularities of the analytically continued projectors in the complex momentum plane. Thus, this length depends on both the flat-band geometry and the band gap. Applying this formalism to Chern flat-band systems, we find that for small gaps, $\xi_\text{RKKY}$ depends non-monotonically on the
quantum metric length: it first decreases, then increases, revealing that stronger
quantum geometry can shorten the
magnetic exchange range. Upon restoring dispersion, a nontrivial inversion representation can force the overlap between Bloch states at antipodal
Fermi points to vanish under gate tuning, producing a $1/R^3$ RKKY tail instead of the conventional $1/R^2$—a
geometric selection effect.
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Optics
Generation of high-fluence and high-intensity hard x-ray attosecond pulses at European XFEL
Ichiro Inoue, Ulrike Boesenberg, Rustam Rysov et al. (+41 more)
By combining hard x-ray attosecond pulses from the European XFEL with total-reflection focusing x-ray optics, we generated nanofocused hard x-ray attosecond pulses with intensities and fluences comparable to the highest values attained in the hard x-ray regime. A peak intensity on the order of 10$^{20}$ W/cm$^2$ is confirmed through the observation of saturation in amplified spontaneous emission from copper atoms. These x-ray pulses enable new scientific opportunities, including the exploration of higher-order nonlinear light–matter interactions, damage-free structure determination, and coherent control of atoms and molecules.
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All authors Ichiro Inoue, Ulrike Boesenberg, Rustam Rysov, Takahiro Sato, Ichika Harima, Chenzhi Xu, Jia Liu, Thomas M. Linker, Zain Abhari, Andrei Benediktovitch, Uwe Bergmann, Ye Chen, Lu Cao, Winfried Decking, Gianluca Geloni, Marc Guetg, Trey Guest, Aliaksei Halavanau, Jörg Hallmann, Takashi Kimura, Naresh Kujala, Aliaksandr Leonau, Shan Liu, Tianyun Long, Johannes Möller, Taito Osaka, Jan-Etienne Pudell, Weilun Qin, Nina Rohringer, Angel Rodriguez-Fernandez, Daniele Ronchetti, Yasuhisa Sano, Matthias Scholz, Roman Shayduk, Jergus Strucka, Yanwen Sun, James Wrigley, Kazuto Yamauchi, Diling Zhu, Alexey Zozulya, Makina Yabashi, Anders Madsen, Jumpei Yamada, Jiawei Yan
Quantum Physics
Converting Quantum Sensing Noise into Erasures
Xingyu Liu, Zhaotong Cui, Binke Xia et al. (+4 more)
Erasures are more favorable for
quantum sensing than unflagged errors such as Pauli errors. However, realistic sensing noise does not usually appear as erasures; it often acts within the same sensing
Hilbert space as the signal, making it difficult to identify and mitigate. For such noise, we establish a noise-model-agnostic necessary and sufficient condition for erasure conversion, identifying the noise components that can be converted into erasures and removed without damaging the signal. For components satisfying the condition, conversion can be realized by a passive dimension-lifted scheme requiring neither detailed noise knowledge nor active control. Theoretically, the protocol remains effective over a broad range of noise strengths and approaches the corresponding precision limit. Experimentally, in single-
photon phase sensing, we recover standard-
quantum-limit precision in a Pauli-noise channel with erasure-convertible weight 0.5, using orbital angular momentum as the ancilla. These results provide a practical route to robust
quantum sensing under realistic noise.
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All authors Xingyu Liu, Zhaotong Cui, Binke Xia, Yuegang Li, Hongjing Li, Jingzheng Huang, Guihua Zeng
Nuclear Theory
Impacts of hexadecapole correlations in actinide nuclei
L. Lotina, K. Nomura, R. Rodríguez-Guzmán et al. (+1 more)
The impact of hexadecapole correlations on the low-energy spectroscopic properties of Th, U, and Pu
nuclei, within the mass range $232 \le A \le 240$, is studied systematically using the mapped $sdg$-IBM model. Fermionic input is obtained via the quadrupole-hexadecapole constrained Hartree-Fock-Bogoliubov approximation, based on the parametrization D1S of the Gogny energy density functional. The $sdg$-IBM
Hamiltonian parameters are determined by mapping the quadrupole-hexadecapole fermionic mean-field potential energy surfaces onto the corresponding bosonic surfaces. The low-energy spectra and transition strengths, obtained via the diagonalization of the $sdg$-IBM
Hamiltonian, compare well with the available experimental data. It is shown that the effects of hexadecapole collectivity can be observed in high-
spin yrast states with
spins $J^{\pi} \geqslant 10^{+}$. The mapped $sdg$-IBM improves the excitation energies of those states, as compared with the simpler $sd$-IBM model. The $sdg$-IBM also improves the description of the $E2$ transition strengths between high-
spin yrast states and predicts strong $E4$ transitions from nonyrast $4^+$ states to the $0^+$ ground state.
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All authors L. Lotina, K. Nomura, R. Rodríguez-Guzmán, L. M. Robledo
Medical Physics · Cross-listed from cs.CV
HERMES: A Hybrid Ensemble for Head-and-Neck Tumor Segmentation, TN Staging, and Recurrence-Free Survival on PET/CT
Kai Wang, Meixu Chen, Elie Nasr et al. (+2 more)
We present HERMES (Hybrid Ensemble for Radiotherapy-target
segmentation, Malignancy staging, and Event-free Survival), a single containerized
algorithm for the three HECKTOR 2026 subtasks:
segmentation of the primary tumor (GTVp) and pathological lymph nodes (GTVn), radiological T/N staging, and recurrence-free survival (RFS), computed from a paired FDG-PET/CT scan and an electronic health record. A 10-fold ensemble of STU-Net Small networks produces the
segmentation; the predicted mask then drives two downstream tasks. Rather than pass a generic radiomics vector to the staging models, we derive from the predicted masks a compact set of geometry features aligned with the size and number axes of AJCC/UICC 7th-edition radiological N/T staging. On internal cross-validation these features raise N-stage balanced accuracy from 0.691 to 0.720 (+0.030), our largest single design gain, at lower feature dimensionality. For prognosis we combine complementary deep and clinical risk experts in an equal-weight ensemble, and train one deep expert with a concordance-tracking survival loss of our own, whose value approximates the concordance index during training. Every component was selected on honest out-of-fold predictions under a regularization-oriented protocol, with no tuning on the public validation set, and deployed as two decorrelated submissions. On the HECKTOR 2026 validation leaderboard, HERMES achieved a weighted score of 0.6454 (Mean Dice 0.641, T balanced accuracy 0.580, N balanced accuracy 0.642, RFS C-index 0.679) and qualified for the testing phase. Team: AMC_HNC.
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All authors Kai Wang, Meixu Chen, Elie Nasr, Ryan Lanning, Moyed Miften
Materials Science
Nanoscale Imaging of Strain-Controlled Altermagnetic Domains in {\alpha}-MnTe
Alex L. Melendez, Sijie Xu, Liangbo Liang et al. (+6 more)
Altermagnets combine compensated
magnetic order with momentum-dependent
spin splitting, offering a route to spintronic functionality without the stray fields of conventional ferromagnets. Mechanical strain provides a promising means of controlling their Néel order, yet the microscopic pathway by which strain reorganizes an altermagnetic texture remains unresolved. Here, we combine scanning nitrogen-vacancy magnetometry with a piezo-driven uniaxial strain
cell to directly image the strain-driven
evolution of
magnetic domains in bulk {\alpha}-MnTe at room temperature. By applying uniaxial stress along the nearest-neighbor Mn-Mn bond direction, we find that compressive strain reorganizes the
magnetic texture through domain coalescence, increasing the size of the largest connected domain while reducing the domain-wall density. On sweeping toward tensile strain direction, however, the domain network follows a distinct trajectory from that observed during the compressive sweep. Instead, the large connected regions fragment into a new metastable configuration, producing pronounced hysteresis in the maximum domain size and stray-field distribution. These results identify domain connectivity and
topology as key carriers of strain-induced
magnetic memory. Our work reveals domain coalescence and hysteretic fragmentation as the microscopic pathway of strain control in {\alpha}-MnTe and establishes a route toward strain-programmable altermagnetic textures and reconfigurable spintronic devices.
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All authors Alex L. Melendez, Sijie Xu, Liangbo Liang, Rong-Zhu Lin, An-Ping Li, Pengcheng Dai, Hu Miao, Zhaoyu Liu, Huan Zhao
Plasma Physics
Revisiting Electron Heating in Capacitively Coupled Plasma (CCP) Discharges: A Nonlinear Dynamics Perspective
Rishabh Singh, Sarveshwar Sharma, Bhooshan Paradkar et al. (+1 more)
Despite decades of research, the electron heating mechanisms in capacitively coupled
plasma (CCP) discharges over a wide range of operating conditions is not fully understood. Although
stochastic heating is generally regarded as the dominant collisionless heating mechanism at low pressures, the inherently nonlinear electron dynamics responsible for this process have not been fully quantified. These nonlinear interactions drive
stochastic heating, a mechanism considered crucial for energy transfer in CCPs, yet its quantitative impact on
plasma parameters remains insufficiently explored. In this work, we investigate electron dynamics in steady-state CCP discharges and demonstrate that electron motion in the
plasma bulk exhibits intrinsically chaotic behavior. The onset of chaos is identified using Poincare sections and quantified through Lyapunov exponent analysis. To further quantify this behavior, we map the spatial distribution of the Lyapunov exponent-normalized by the electron-neutral collision frequency-across the
plasma bulk for different pressures and RF voltages. The normalized Lyapunov exponent increases systematically with decreasing pressure and increasing RF voltage, indicating enhanced stochasticity and a stronger sensitivity of electron trajectories to initial conditions. These results establish the Lyapunov exponent as a quantitative measure of effective
stochastic scattering in collisionless CCPs and provide a direct comparison with the classical
stochastic collision frequency proposed by Popov and Godyak [Journal of Applied Physics 57, 53-58 (1985)]. The present analysis offers a unified nonlinear dynamical framework for understanding
stochastic electron heating in low-pressure RF
plasmas.
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All authors Rishabh Singh, Sarveshwar Sharma, Bhooshan Paradkar, Sudip Sengupta
General Relativity and Quantum Cosmology
Chaotic Imprints in Gravitational Waves from Conformal-Anomaly-Corrected Extreme-Mass-Ratio Inspirals
Wei-Hao Zhang and Yu-Sen An
In this work, we investigate the effect of chaotic orbits on the extreme mass ratio inspiral (EMRI) gravitational wave signals where the central black hole is corrected by
quantum conformal anomaly. We utilize the numerical kludge method to compute gravitational waveforms produced by the compact object along different orbital trajectories, and also derive the corresponding frequency distribution and energy spectra of gravitational waves. Our calculations reveal that variations in orbital energy or anomaly coefficient drive the orbital
evolution from regular integrable motion to chaotic motion, and such dynamical transition leaves clear imprints on gravitational-wave signal. Specifically, gravitational waves originating from chaotic orbits feature pronounced irregular and time-varying amplitude fluctuations, accompanied by abundant fine spectral spikes and extended continuous spectral distributions in both frequency and energy domains, which differ drastically from the gravitational radiation generated by the regular non-chaotic orbits. Moreover, we evaluate the detectability by comparing the calculated characteristic strain of gravitational waves emitted by the compact object on different orbits with the sensitivity curves of future space-based GW detectors, including LISA, Taiji and TianQin. The results demonstrate that these detectors are capable of capturing gravitational-wave signals from chaotic systems modified by conformal anomalies, which provide a potential pathway for detecting conformal anomaly correction in astronomical observation.
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Mesoscale and Nanoscale Physics
Same-spin Andreev reflections in the quantum Hall regime: the role of loss
Chun-Chia Chen, Jordan T. McCourt, John Chiles et al. (+7 more)
The interfaces of
superconductors and topological materials hold promise for realizing exotic states and excitations. An important example is provided by the
chiral Andreev edge states (CAES), which are formed at interfaces between
quantum Hall (QH) states and
superconductors (SC). CAES combine electron and hole amplitudes which are hybridized via Andreev reflections. This study explores the
spin properties of the CAES through selective
spin filtering of the QH edge channels. We find robust evidence of
spin-flips accompanying the Andreev processes: electrons can be reflected from the
superconductor as holes in the same
spin channel. We demonstrate that the distribution of the reflection probabilities is exponential and then use random
matrix theory to account for this observation. Finally, we observe Andreev reflections in the
spin-polarized {\nu} = 1 case, which is enabled by particle loss. Our findings shed light on the mechanism underlying Andreev reflections of
spin-polarized
chiral states. They also demonstrate the importance of considering non-Hermiticity when constructing topological
superconductors in hybrid materials.
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All authors Chun-Chia Chen, Jordan T. McCourt, John Chiles, Lingfei Zhao, Kenji Watanabe, Takashi Taniguchi, François Amet, Antonio L. R. Manesco, Harold U. Baranger, Gleb Finkelstein
Quantum Physics
Quantum random number generation using spatial quantum noise of light
Mohamed Armoon Shaliq and Ashok Kumar
Generating high-speed, verifiable random numbers is a fundamental requirement for cryptography, large-scale
stochastic simulations, and secure
quantum communication. Here, we present a robust
quantum random number generator that utilizes the spatial distribution of
quantum fluctuations captured by an electron-multiplying charge-coupled device operated in high-speed kinetic mode. Through rigorous detector calibration and shot-noise analysis, we characterize the spatial
quantum noise obtained from the spatial intensity fluctuations of the coherent states of light. Such
quantum noise serves as a high-
entropy source, enabling an instantaneous random bit generation rate of 5.92 Gbps without algorithmic randomness extraction in the present configuration. The sustained output rate is, however, limited to 7.5 Mbps by the bandwidth of the serial electronic readout. The generated sequences successfully pass the NIST SP 800-22 and Marsaglia Diehard statistical test suites, confirming the high quality and unpredictability of the
entropy source.
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Quantum Physics
Feedback stabilization of multi-qubit Hamiltonian parameters enabled by single-shot measurement-based sequential Monte Carlo
Hyeongyu Jang, Jaemin Park, Younguk Song et al. (+6 more)
Fast measurement, signal processing, and accurate estimation of
Hamiltonian parameters are essential for feedback control in
quantum-classical interface circuitry. However, existing frequentist and
Bayesian inference methods typically require a large number of measurements to achieve the accuracy needed to mitigate
qubit decoherence. Consequently, feedback control of
semiconductor qubits has largely been limited to single-
qubit frequency stabilization, whereas two-
qubit parameter stabilization remains experimentally unexplored. Here, we demonstrate a real-time feedback framework based on sequential Monte Carlo estimation using one bit of data from a single-shot measurement. Using a four-
qubit semiconductor quantum dot device, we rapidly estimate individual
qubit frequencies, yielding an approximately twofold increase in coherence time compared with a conventional
Bayesian strategy. Moreover, sequential two-
qubit parameter estimation using two bits of data enables stabilization of
qubit-
qubit coupling, allowing both quasi-static frequency drift and exchange-interaction noise to be estimated and suppressed. By shortening the time required for precise parameter estimation, these results demonstrate the importance of the synergistic development of classical and
quantum electronics for building robust and scalable
quantum technologies in fluctuating environments.
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All authors Hyeongyu Jang, Jaemin Park, Younguk Song, Jinwoong Kim, Hanseo Sohn, Lucas E. A. Stehouwer, Davide Degli Esposti, Giordano Scappucci, Dohun Kim