High Energy Physics (Phenomenology)
Too good to go: Upcycling Phase-Space Points for Multijet Processes
Konrad Helms, Timo Janßen and Steffen Schumann
The efficient sampling of high-dimensional phase spaces is a major challenge for Monte Carlo event generators, as for high-multiplicity final states the evaluation of scattering
matrix elements becomes computationally expensive. We here introduce a training strategy that significantly reduces the cost of adapting the samplers, while delivering samplers that outperform the current
benchmarks. The method exploits the nested structure of phase spaces, where an $(N+1)$-particle phase space factorises into an $N$-particle and a one-particle phase space. We thereby assume that an efficient sampler for the corresponding $N$-particle phase space is already available, as is the case in stacks of QCD $X+n$-jets processes. By augmenting an $N$-particle to an $(N+1)$-particle
dataset, we obtain a training sample that more closely resembles the integrand and is statistically larger than, for example, a uniformly sampled one. Starting the adaptation phase of the sampler with a well-sampled $N$-particle core accelerates learning of the full $(N+1)$-particle phase-space density. Since the augmented sample is only used as an initial proposal distribution, unbiased Monte Carlo estimates are still guaranteed by exact event weighting. The approach is agnostic to the trained sampler and can be applied to machine-learning-based methods as well as more traditional
algorithms such as VEGAS. We demonstrate the reduction in
matrix-element evaluations and final performance increase for jet-associated Drell–Yan and top-pair production at the LHC, using Continuous Normalising Flow samplers.
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General Relativity and Quantum Cosmology · Cross-listed from math.DG
An isoperimetric characterization of a new ADM-like mass for $C^0$-asymptotically flat manifolds
Luca Benatti and Mattia Fogagnolo
We prove that the notion of mass recently introduced by Mazurowski and Yao for continuous metrics coincides with Huisken's isoperimetric mass on smooth Riemannian $3$-
manifolds with nonnegative scalar
curvature whose metric has sharp $C^0$-asymptotically flat behavior. As a consequence, we deduce a Riemannian Penrose inequality for the mass parameter of asymptotically Schwarzschildian $3$-
manifolds.
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Quantum Physics
Towards Reproducible Evaluation of Distributed Quantum Circuit Partitioning Algorithms
Javier Vela-Tambo, Davud Azizov and Tian Guo
Distributed
Quantum Computing (DQC) addresses the physical scaling limitations of monolithic
quantum processors by networking modular
Quantum Processing Units (QPUs). Efficient execution of
quantum algorithms on DQC architectures requires compiling them across QPUs while minimizing inter-QPU communication bottlenecks, primarily through
circuit partitioning. However, current evaluations of state-of-the-art partitioning heuristics focus primarily on the total
entanglement cost of the partitions, failing to capture the broader structural and temporal overheads introduced by distributed network constraints. This paper addresses this evaluation gap by applying established monolithic benchmarking metrics to partitioned distributed
circuits to quantify the performance impact of network constraints. Using an open-source, automated evaluation pipeline, we systematically assess diverse partitioning
algorithms across standardized workloads and
quantum network
topologies. Our empirical results reveal that partitioning
algorithms with comparable
entanglement costs can still introduce drastically different physical execution penalties. By exposing these hidden trade-offs, such as severe increases in
circuit depth and substantial reductions in gate density, this study demonstrates that comprehensive
circuit-level metrics are essential for guiding the future design of DQC compilers.
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Atomic Physics
Beyond-EUV spectrum of highly-charged gadolinium
M.L. Reitsma, J. Sheil, O.O. Versolato et al. (+2 more)
We report ab initio relativistic calculations on the complex Gd$^{18+}$ and Gd$^{26+}$ highly-charged ions, which are relevant to beyond-extreme-ultraviolet (BEUV) light sources based on
laser-produced gadolinium
plasmas. Using the particle-hole configuration-interaction with many-body perturbation theory (CI+MBPT) method, we systematically saturate the $n=4$ configuration space and determine the influence of multiply excited states on the emissivity spectrum. For Gd$^{26+}$ we find behavior analogous to that of its isoelectronic counterpart Sn$^{12+}$, with strong contributions from multiply excited states, where even the quadruply excited states become significant at certain effective temperatures. In contrast, the industry-relevant 6.7 nm emission of Pd-like Gd$^{18+}$ is dominated by the singly excited $4d^{10} {\ }^{1}S_{0}$ – $4d^{9}4f {\ }^{1}P_{1}$ transition, while multiply excited states primarily contribute to out-of-band emission. The calculated spectra show good agreement with experiment and demonstrate that the importance of multiply excited states depends strongly on both charge state and
plasma conditions.
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All authors M.L. Reitsma, J. Sheil, O.O. Versolato, E.V. Kahl, J.C. Berengut
Statistical Mechanics
Localization Delocalization Transition in Diffusion with Adaptive Resetting
Tommer D. Keidar and Shlomi Reuveni
Stochastic resetting can localize
diffusion and generate nonequilibrium steady states, but the conditions under which spatially dependent resetting produces localization remain unclear. Here, we establish a general classification for
diffusion under adaptive resetting, where the resetting rate $r(x)$ depends on position. For rates with the asymptotic scaling $r(x)\sim |x|^\lambda$, we identify a sharp threshold at $\lambda=-2$. For $\lambda>-2$, the steady state is localized and exhibits stretched-exponential tails, whereas for $\lambda<-2$, resetting is asymptotically too weak to localize the particle. Precisely at the marginal scaling $r(x)\sim |x|^{-2}$, a qualitatively new regime emerges: the steady state develops power-law tails with a temperature-dependent exponent and exhibits a finite-temperature delocalization transition. Thus, inverse-square resetting plays the role of the logarithmic potential in
equilibrium, establishing a nonequilibrium counterpart of the temperature-driven delocalization seen there.
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Materials Science
Laser induced ultrafast Co 3d and Ho 4f spin dynamics in CoHo ferrimagnetic alloys
Deeksha Gupta, Boonthum Kunyangyuen, Matthias Riepp et al. (+8 more)
The transition metal (TM) / rare-earth (RE)
alloys have received renewed interest lately as model systems to decipher the origin of all-optical helicity-independent switching (AO-HIS) by femtosecond
laser pulses. Recently, a distinct single-pulse magnetization reversal mechanism, based on domain-wall motion and coalescence, has been reported in CoDy and CoHo
alloys, as well as in Co/Gd ultrathin
bilayers. It has been claimed that this specific toggle switching is achieved when the Co sublattice is fully demagnetized and the characteristic demagnetization times {\tau}RE of the RE (Gd, Dy or Ho) sublattices is longer than that of the Co and the angular momentum transferred to Co is reduced. Element- and time-resolved X-ray spectroscopy studies of CoDy
alloys have reported characteristic demagnetization times of {\tau}Co = 0.2 ps and {\tau}Dy = 0.6 ps at room temperature. Similarly, Ho is expected to exhibit a slower response, but its ultrafast 4f
spin dynamics remain experimentally unexplored. Here, we report on element- and time-resolved investigations of femtosecond
laser induced ultrafast dynamics of the Co 3d and Ho 4f
spins in ferrimagnetic Co_{80}Ho_{20}
alloys to verify this prediction. We observed characteristic demagnetization times {\tau}Co = 0.22 +/- 0.01 ps and {\tau}Ho = 0.87 +/- 0.15 ps at room temperature. These results show that Ho demagnetizes substantially more slowly than Co in Co_{80}Ho_{20}, supporting the proposed condition for domain-wall-mediated all-optical toggle switching
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All authors Deeksha Gupta, Boonthum Kunyangyuen, Matthias Riepp, Karsten Holldack, Radu-Marius Abrudan, Torsten Kachel, Niko Pontius, Christian Schüßler-Langeheine, Mircea Vomir, Michel Hehn, Nicolas Bergeard
High Energy Astrophysical Phenomena
Source models of ultrahigh-energy cosmic rays
Bing Theodore Zhang
We investigate potential sources of ultrahigh-energy
cosmic rays (UHECRs) and their acceleration mechanisms, focusing on astrophysical phenomena associated with massive
stellar deaths and supermassive black holes. These phenomena include gamma-ray bursts (GRBs), engine-driven
supernovae/hypernovae, magnetars, newly born
pulsars, binary
neutron star mergers (BNS),
tidal disruption events (TDEs), and active
galactic nuclei (AGN). While high-luminosity GRBs (HL GRBs) are constrained as UHECR sources by high-energy
neutrino observations, low-luminosity GRBs (LL GRBs) and engine-driven
supernovae remain promising candidates, with intermediate-mass
nuclei as the dominant components. Compact binary mergers and $r$-process nucleosynthesis in
neutron-rich environments may also contribute to ultraheavy UHECRs. The composition of UHECRs from TDEs depends on the properties of the disrupted
stars. AGN, particularly
radio galaxies, remain promising sources, with acceleration occurring in their large-scale jets and lobes. Shear acceleration mechanisms have been proposed as a viable alternative for accelerating UHECRs, involving the re-acceleration of low-energy
cosmic rays and being compatible with the observed spectrum and composition. Future multi-messenger observations, especially from upcoming observatories, are expected to provide critical data to refine our understanding of UHECR origins, test existing models, and explore new acceleration mechanisms.
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High Energy Physics (Phenomenology)
Learning Transverse Momentum Distributions from Raw Scattering Events via Conditional Diffusion
Jitao Xu, Christopher Cocuzza, Kevin Braga et al. (+3 more)
Extracting transverse momentum dependent parton distribution functions (TMD PDFs) from semi-inclusive deep inelastic scattering (SIDIS) data is a central goal of the nucleon structure program at Jefferson Lab and the future Electron-Ion
Collider. Traditional extraction methods rely on parameterized functional forms and iterative fitting, which can limit the flexibility of the resulting distributions and make uncertainty quantification cumbersome. We present a conditional
diffusion model that learns to map raw SIDIS event kinematics directly to TMD PDFs, bypassing explicit functional assumptions. Evaluated on simulated SIDIS data at CLAS12 kinematics, the model recovers the underlying TMD with informative uncertainties that narrow steadily with increasing event statistics, and produces reliable estimates even with as few as 1,000 conditioning events, a statistics-limited regime directly relevant to ongoing and planned experiments.
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All authors Jitao Xu, Christopher Cocuzza, Kevin Braga, Daniel Lersch, Nobuo Sato, Yaohang Li
Mathematical Physics
Coupled stochastic variational principles for multiscale surface gravity waves – Part I: theoretical framework
Etienne Mémin and Arnaud Debussche
This paper develops a comprehensive
stochastic variational framework for surface
gravity waves. Starting from Luke's variational principle for irrotational, incompressible free-surface flow, we introduce a decomposition of the velocity potential into a large-scale deterministic component and a regularized
stochastic noise term representing unresolved scales. A path-wise variational principle yields the
stochastic counterparts of the Laplace, Bernoulli, and kinematic boundary conditions. To close the system, a second variational principle in expectation is formulated, providing
evolution equations for the noise correlation functions. The resulting coupled system preserves the
Hamiltonian structure of the Zakharov–Craig–Sulem formulation. We further analyze explicit solutions via WKB approximation and show that the noise correlation functions satisfy a Hamilton-Jacobi equation with ray-tracing dynamics. This framework provides a rigorous foundation for reduced
stochastic models of ocean waves and for the kinetic theory developed in the companion paper.
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Applied Physics
Ternary-Valued Finite-Difference Time-Domain Method: Asymptotic Agreement with the Yee Scheme Through Noise-Shaped Quantisation
Ivan S. Maksymov
I show that finite-difference time-domain (FDTD) dynamics can be reproduced using field variables restricted to the ternary alphabet ${-1,0,+1}$. The integration is carried out by a state accumulator, while quantisation is done by a second-order noise-shaped encoder with a separate error register. The Courant number $S$ plays two roles: it is the exact fixed-point ratio and also sets the encoder's oversampling ratio. When $S$ is chosen as a power of two, each
cell update requires neither run-time multiplication nor floating-point arithmetic, and each emitted field symbol is represented by just two bits. The ternary scheme converges asymptotically to the standard Yee scheme as $S$ decreases towards zero. I report wall-clock and instruction counts relative to a floating-point reference, long-time energy integrations over $2\times10^{5}$ steps and the $S$ required to achieve a prescribed accuracy for the driven mode. Extending the approach to acoustics, Virieux-type elastodynamics and Schrodinger-equation solvers is a prospective direction towards a broader class of quantised physics solvers for resource-constrained and specialised hardware.
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Astrophysics of Galaxies
HURACAN: A comparison of stellar and interstellar proper motions inside L1688
M. Piecka, J. Alves, A. Rottensteiner et al. (+3 more)
The assumption that molecular clouds are kinematically coupled to the young
stellar populations forming within them is observationally still poorly constrained. With the transverse component $v_{\textrm{t}}$ of the interstellar medium (ISM) motion being largely unknown, the three-dimensional kinematic state of even the closest clouds remains incomplete. We provide the first direct measurement of the transverse motion of the ISM inside the Ophiuchus cloud L1688 and compare it with the kinematics of the surrounding young
stellar populations. The measurement was obtained using intensity-based image registration applied to archival data, allowing us to generate a proper motion field of the studied regions and determine the cloud's bulk motion, $(\mu_{\alpha^*},\mu_\delta)^{\mathrm{ISM}}_{\mathrm{median}}=(-3.0, -24.1)$ mas yr$^{-1}$. This motion differs from the kinematics of the youngest population in Upper Scorpius by $3\pm1$ km s$^{-1}$, highlighting the possibility of a bias when using
stars as a proxy for the ISM motion near
star-forming regions. By comparing the cloud's motion with that of the youngest
stellar population in the region and the B-
star Oph S1 located within the cloud, we find that
stellar feedback must have dynamically shaped the motion of the ISM over the last few million years. Furthermore, by studying a shell-like ISM structure appearing in L1688, we find evidence suggesting that this object is likely neither a typical Herbig-Haro object nor a
supernova remnant, with its origin remaining a mystery. Our results demonstrate that archival and future high-resolution near-infrared observations can and will continue to enable measurements of ISM transverse motions in nearby clouds, opening a new window for studying ISM dynamics that is not accessible when using radial velocities alone.
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All authors M. Piecka, J. Alves, A. Rottensteiner, S. Hutschenreuter, S. Meingast, L. Posch
Mesoscale and Nanoscale Physics
Giant bulk photovoltaic effect driven by interfacial symmetry breaking in MoS2/Ta2NiSe5 heterostructures
Jianwen Ma, Pengliang Leng, Lei Peng et al. (+16 more)
Van der Waals (vdW)
heterostructures offer a versatile platform for engineering unconventional bulk photovoltaic (BPV) effect through interfacial
symmetry breaking. However, the coexistence of multiple photophysical mechanisms, driven by structural complexity, spontaneous charge transfer, and strong interlayer coupling, often obscures the microscopic origin of the BPV response and hinders its rational optimization. Here, we demonstrate a pronounced BPV effect localized at the overlap region of a cross-bar MoS2/Ta2NiSe5 vdW
heterostructure, where
symmetry breaking induced by vertical stacking lifts the inversion center of MoS2. The orthogonal device geometry enables the independent probing of intralayer and interfacial photoresponse pathways, facilitating clear separation of competing mechanisms. Spontaneous interfacial charge transfer between MoS2 and Ta2NiSe5 further establishes a strong interlayer electronic coupling. By modulating the interlayer potential landscape through gate voltage and vertical electric fields, we achieve an optimized zero-bias photocurrent density of 247 A/cm2 and a BPV coefficient of 0.99 V-1. Supported by theoretical modelling, our results illustrate how minimalist device geometry can transform complex
heterostructures into experimentally tractable platforms. This strategy paves the way for analyzing and optimizing interface-driven BPV effect, with implications for self-powered optoelectronics, broadband photodetection, and energy-harvesting nanodevices.
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All authors Jianwen Ma, Pengliang Leng, Lei Peng, Congming Hao, Xianghao Meng, Jiaqi Liu, Yang Gan, Min Luo, Zifan Zhang, Jiaming Gu, Qinghang Liu, Lidan Duan, Du Xiang, Wu Shi, Peng Wang, Weibin Chu, Xiang Yuan, Weida Hu, Cheng Zhang
Materials Science
THz-induced phonomagnetism in diamagnetic quantum paraelectric KTaO$_3$
C. Kadlec, F. Kadlec, D. Repček et al. (+13 more)
The current efforts striving to develop new ways of data manipulation are aimed at ultrafast control of magnetization in
magnetic materials, as well as at inducing
magnetic moments in diamagnetics. We demonstrate that in the diamagnetic
quantum paraelectric KTaO$_3$, the electric field of circularly polarized THz pulses with an amplitude of $\sim 300\,$kV/cm induces a transient
magnetic-like response by resonantly exciting its degenerate soft polar
phonon. This
phonon-mediated response was measured using the THz pump—optical probe technique via the time-resolved magneto-optic Faraday effect. Our detection scheme was set up to cancel out the major part of the electro-optic Kerr effect which also usually significantly contributes to the transient response. The Kerr-effect-related signal was further suppressed by subtracting the experimental data related to oppositely circularly polarized THz radiation. Thus, we were able to unambiguously identify a temperature-dependent
magnetic-like behavior of the KTaO$_3$
crystal manifested by the extracted Faraday rotation. We developed a theoretical model describing well quantitatively the measured curves of the transient Faraday effect signal. However, their amplitudes exhibit an unexpected temperature dependence, which might be a key to a deeper understanding of the observed phonomagnetic effect.
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All authors C. Kadlec, F. Kadlec, D. Repček, P. Kužel, M. Basini, J.-C. Deinert, S. Kovalev, T. Tadano, M. Udina, I. Ilyakov, T.V.A.G. de Oliveira, A. Ponomaryov, A. Arshad, A. Maia, S. Bonetti, S. Kamba
Quantum Physics
Fast On-Chip Thermometry with TiN Kinetic Inductance Resonators in 22 nm Process Technology
Johann Drayne, George Ridgard, Lorenzo Peri et al. (+9 more)
Understanding the temporal and spatial dependence of temperature is critical in high-performance cryogenic devices. Typical thermometry techniques struggle to simultaneously combine high bandwidth, sensitivity and on-chip integration, limiting their ability to measure fast intra-device thermal fluctuations. Here, we demonstrate a time-resolved thermometry platform based on TiN kinetic inductance resonators integrated in a 22 nm FDSOI chip. By tracking temperature-dependent shifts in the resonant frequency, we achieve sub-millikelvin temperature sensitivity down to temperatures of 100 mK. Time-resolved on-chip pulsed heating experiments as a function of distance reveal an onset delay, consistent with a quasi-ballistic heat propagation velocity of 3.9 ${\pm}$ 0.1 mm ${\mu}$s${}^{-1}$. We also show that elevated temperatures increase net thermal conductance, shortening thermal relaxation times across all spatial separations. This behaviour manifests in two distinct regimes: a substrate-limited regime at 100 mK, where cooling rates vary with heater distance, and a Kapitza boundary-limited regime at 400 mK, where thermal relaxation becomes more spatially uniform. These measurements demonstrate kinetic inductance thermometry's ability to rapidly probe non-
equilibrium temperature dynamics in cryogenic devices such as
quantum processors.
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All authors Johann Drayne, George Ridgard, Lorenzo Peri, Frederic Schlattner, Fabio Olivieri, Mathieu de Kruijf, Isaac Harris, Grayson Noah, James Kirkman, Alberto Gomez-Saiz, M. Fernando Gonzalez-Zalba, Thomas Swift
Optics
Self-starting Dynamics in All-fibre All-Normal-Dispersion Thulium Mamyshev oscillator
Dennis C. Kirsch, Kirill Grebnev, Alberto Rodriguez Cuevas et al. (+8 more)
Ultrashort pulse formation from noise represents a fundamental self-organisation process in nonlinear dissipative systems and remains central to ultrafast photonics. Mamyshev oscillators offer a particularly valuable platform for investigating this phenomenon because they do not rely on conventional saturable absorbers. Instead, pulse formation is governed by self-phase modulation in normal-dispersion fibres combined with periodic offset spectral filtering. Achieving self-starting pulse formation in these systems is challenging, particularly at longer wavelengths, due to limited normal-dispersion components and the complex gain dynamics. This work reports, to the best of current knowledge, the first self-starting, all-fibre, all-normal-dispersion Thulium-doped Mamyshev oscillator operating near 1.9um. The cavity employs a compact Fabry-Perot design incorporating a dispersion-engineered Thulium-doped gain fibre, a highly nonlinear passive normal-dispersion fibre, and a pair of chirp-free broadband fibre Bragg gratings. The oscillator self-starts without external seeding or active modulation and stabilises noise-like pulse generation regime at a fundamental cavity repetition rate. Real-time measurements and numerical simulations reveal the build-up pathway from noise through transient multi-pulsing and pulse competition to a stationary noise-like envelope. Our results show that both tailored
laser components and gain-medium-specific dynamics are essential for enabling self-starting ultrashort pulse generation in Mamyshev oscillators and for extending these
laser concepts beyond the near-infrared, thereby facilitating the development of compact and robust shortwave infrared (SWIR) sources and new regimes of ultrafast self-organisation.
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All authors Dennis C. Kirsch, Kirill Grebnev, Alberto Rodriguez Cuevas, Mikhail E. Likhachev, Svetlana S. Aleshkina, M. V. Yashkov, Sonja Unger, Claudia Aichele, Adrian Lorenz, Auro Perego, Maria Chernysheva
Quantum Physics
A Superconducting Phase Transition Single-Electron Transistor
Gorka Aizpurua-Iraola, Thomas H. Swift, Felix-Ekkehard von Horstig et al. (+6 more)
Quantum computers require fast and accurate methods for
qubit state detection. Phase-transition sensors exploit the abrupt change between two physical states of a material to achieve enhanced sensitivity and have enabled advanced detectors for
quantum technologies, such as superconducting nanowire single-
photon detectors. However, this sensing principle has not yet been applied to
semiconductor spin qubits. Here, we demonstrate a superconducting phase-transition
radio-frequency single-electron transistor (PTSET), a charge sensor for
semiconductor spin qubits whose response is enhanced by a superconducting-to-normal phase transition. The transition is engineered by linking the sensor current to a low-critical-current, high-kinetic-inductance inductor integrated into the
radio-frequency matching network. We demonstrate improvements in sensitivity of one and two orders of magnitude over conventional rfSETs in the large- and small-signal regimes, respectively. Our results establish phase-transition sensing as a route towards ultrasensitive, integrated charge sensors for
semiconductor quantum computing and point to broader applications, including cryogenic
photon detection for
radio astronomy.
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All authors Gorka Aizpurua-Iraola, Thomas H. Swift, Felix-Ekkehard von Horstig, Domenic Prete, James Kirkman, Grayson M. Noah, Fabio Olivieri, Alberto Gomez-Saiz, M. Fernando Gonzalez-Zalba
Fluid Dynamics
High-resolution in situ analysis of biomass pyrolysis by combining quantitative synchrotron $\mu$CT and 3D particle-resolved simulations
Emeric Boigné, Mohamed M. Ahmed, Collin Foster et al. (+7 more)
Understanding the coupling between transport, chemical kinetics, and structural response within solid fuel combustion requires in situ measurements at high spatial resolution. To examine the dynamics of biomass pyrolysis, we optimize synchrotron X-ray micro-computed
tomography ($\mu$CT), and conduct 3D particle-resolved simulations. A micro-focused heating
cell with controlled heating and flow rate is employed, achieving temperatures of up to 1240 K and 3D imaging at 3.24 $\mu$m spatial and sub-minute temporal resolutions. The pyrolysis of three biomass materials at sample heating rates of 10-14 K/min are examined. The $\mu$CT measurements capture pore deformation, cracking, anisotropic shrinkage, and provide simultaneous thermogravimetric and thermovolumetric analyses to examine specific secondary pyrolysis pathways. Complementary 3D simulations considering detailed kinetics and structural response reproduce the key trends observed, and identify deficiencies in capturing simultaneous mass and volume losses during pyrolysis.
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All authors Emeric Boigné, Mohamed M. Ahmed, Collin Foster, Edna R. Toro, Dilworth Y. Parkinson, Alastair A. MacDowell, Harold S. Barnard, Francesco Panerai, Chiara Saggese, Matthias Ihme
Quantum Gases
Crossing the Rotational Sound Barrier in a Quantum Solvent
Baptiste Coquinot, Giacomo Bighin, Mikhail Lemeshko et al. (+1 more)
Molecules embedded in superfluids provide an experimentally controllable platform for investigating
impurity physics. Here, we investigate a driven molecule rotating in a superfluid environment, including helium and Bose–Einstein condensates, at rotation frequencies similar to the bath dynamics. Within the experimentally relevant platform of an optical centrifuge, we show that the rotor remains localized up to a characteristic harmonic frequency that can realistically exceed the excitation energies of the bath, enabling access to ultrafast rotating
impurities. In the co-rotating frame, the bath excitations experience a rotational Doppler shift, generating angular-momentum-resolved resonances absent in
equilibrium angulon theory. We identify a dissipative rotational sound barrier at which the molecule resonantly emits bath excitations and undergoes strong angular momentum exchange with the surrounding medium. Overall, we establish the dynamical phase diagram of the driven rotor in a
quantum solvent and introduce a generic platform for investigating fast driven rotating
impurities in
quantum many-body systems.
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All authors Baptiste Coquinot, Giacomo Bighin, Mikhail Lemeshko, Ragheed Alhyder
Quantum Physics · Cross-listed from math.NA
A quantum-assisted framework for PDE-based Bayesian inverse problems
Dong An, Yinan Li, Pucheng Tang et al. (+1 more)
Quantum computing offers potential advantages for solving partial differential equations (PDEs). However, most existing
quantum PDE solvers primarily focus on preparing
quantum states for solutions, while the efficient recovery of classical information from these states remains less explored. Motivated by the readout limitation, we propose a
quantum-classical hybrid framework for
Bayesian PDE inversion problems: The
quantum processor evolves the PDE and evaluate the loss function with sampling noises, while the classical computer tunes the hyper-parameters in the Gaussian Process Regression to explore the next trial candidate. To match the
quantum solvers for linear and semi-linear autonomous
evolution PDEs, we suggest to use a normalized
quantum-state loss as the data-misfit function and evaluate the new misfit by combining
quantum PDE solvers with the Hadamard test, thereby allowing us to extract useful classical information using only a limited number of
quantum state copies without reconstructing the full solution vector. The analysis of error propagation and overall complexity of loss evaluation under a prescribed accuracy shows that the new data-misfit function outperforms the conventional L2-loss under
quantum measurements.
Quantum circuit simulations of 1D and 2D linear convection
diffusion equations under approximate and finite sampling loss evaluations, together with classical numerical experiments on a nonlinear forced viscous Burgers equation, demonstrate the feasibility of the proposed approach for parameter inversion even when the loss evaluations are affected by sampling noise. This framework may provide a viable
quantum-assisted scheme for PDE-based inverse problems and elucidate the potential of
quantum PDE
algorithms in addressing a complete
quantum-to-end optimization stack.
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All authors Dong An, Yinan Li, Pucheng Tang, Yunfeng Xiong
Materials Science
Intrinsic anomalous Hall response in the bilayer kagome ferromagnet Co$_3$Sn
Yuqi Qin, Soumya Sankar, Xingkai Cheng et al. (+4 more)
Transition-metal kagome magnets provide a rich platform for investigating the interplay between layer stacking,
magnetic order, and band
topology. Here, we report the molecular beam epitaxy and experimental investigation of high-quality thin films of the kagome metal Co$_3$Sn, which has not been synthesized in bulk form yet. Structural and chemical analyses confirm a hexagonal
lattice structure ($P6_3/mmc$) composed of direct A-B stacked Co$_3$Sn kagome
bilayers. Magnetometry reveals robust easy-plane ferromagnetism with a Curie temperature exceeding $300\,\text{K}$. Magneto-transport measurements demonstrate metallic behavior (carrier density $n\approx5.01\times10^{22}\,\text{cm}^{-3}$) alongside a temperature-independent anomalous
Hall conductivity of $\sigma_{\rm AHE}\approx90\,\Omega^{-1}\cdot{\rm cm}^{-1}$, extending from $2\,\text{K}$ up to room temperature. Results from first-principles density functional theory calculations attribute this anomalous
Hall response to intrinsic Berry
curvature hotspots near the
Fermi level in the
spin-split band structure. Our results establish Co$_3$Sn as a room-temperature kagome ferromagnet and highlight the impact of the layer stacking sequence on the material properties of kagome metals from the CoSn family.
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All authors Yuqi Qin, Soumya Sankar, Xingkai Cheng, Yifan Jiang, Shiming Lei, Junwei Liu, Berthold Jäck
High Energy Physics (Phenomenology)
Advances in the holographic description of hot and dense QCD matter
Nicolas Kovensky and Andreas Schmitt
We review and extend recent progress on QCD-like phases at nonzero temperature and chemical potentials within the gauge-
gravity duality. We focus on the Witten-Sakai-Sugimoto model, a top-down approach based on string theory which allows for a unified treatment of
mesons,
baryons and
quarks. Phases such as pion condensation, baryonic and quarkyonic matter are located in the phase diagram, and we discuss predictions as well as weaknesses and limitations of this
holographic approach. One of the novelties included in this review is the first
holographic construction of a pionic phase between BEC and BCS regimes, which however is found to be metastable. We also discuss future directions in
holographic QCD, within the model used here and in a wider context.
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Optics
Field-driven attosecond deflection of electron beams at the position of planar foils
Xiaofan Gui, Kenichi L. Ishikawa and Yuya Morimoto
While the coupling of free-electron beams and light has enabled the control of electron's
quantum states and the generation of ultrashort electron pulses, it can distort the measured signal when probing a
laser-driven sample with an electron beam. Here, we theoretically study optical-field-driven beam deflection that inevitably occurs at the location of a
laser-excited sample. Treating electrons in a beam as classical point particles and focusing on thin planar samples, we conduct a systematic study of the instantaneous deflection amplitudes with respect to light polarization, material type, thickness, and interaction geometry. For s-polarized excitation fields, the deflection amplitude is strictly proportional to the excitation-field amplitude in a foil, making beam deflection unavoidable. Conversely, for p-polarized fields, a nontrivial relationship emerges between the deflection amplitude and the field amplitude due to the interplay of electric and
magnetic fields coupled with the electron-light velocity mismatch. Crucially, we demonstrate that the deflection can be minimized even under high field strengths by selecting an optimal configuration for a given foil material and thickness. These findings provide key guidelines for designing future time-resolved imaging experiments using ultrashort electron beams.
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General Relativity and Quantum Cosmology
Conformal Cyclic Cosmology from Varying Fundamental Constants
Konrad Marosek and Adam Balcerzak
We investigate a bimetric cosmological model in which the gravitational and matter sectors are described by distinct metrics related through a time-dependent function $\alpha(t)$. This relation leads to dynamical gravitational parameters, with $G(t)\propto\alpha^{-3}$ and $c_{\rm grav}(t)\propto\alpha^{-1}$, where $c_{\rm grav}$ denotes the propagation speed of gravitational interactions. We consider a class of solutions for which $\alpha\rightarrow\infty$ at a finite
cosmic time, resulting in $G\rightarrow0$ and $c_{\rm grav}\rightarrow0$. For an analytically tractable solution, we show that the final singularity occurs at finite conformal time and possesses a conformal structure compatible with a possible transition between successive cosmological cycles. The Tipler and Królak criteria indicate that the singularity is strong. We further discuss the physical consequences of the weakening gravitational interaction, including the dissolution of gravitationally bound structures and the shrinking of black-hole horizons. These effects suggest a possible mechanism leading toward an effectively radiation-dominated final state, which may be relevant for Conformal Cyclic Cosmology. The results provide a motivation for extending the analysis to more general scalar–tensor theories of
gravity.
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Materials Science
Atomic-scale composition of the ternary III-V semiconductor (Al,Ga)Sb visualized by cross-sectional scanning tunneling microscopy
Hitesh Kumar, Vladimir Kaganer, Zijin Lei et al. (+3 more)
Cross-sectional scanning tunneling microscopy at 5 K is used to investigate cation mixing in (Al,Ga)Sb layers grown by molecular beam epitaxy, via direct atom counting at the (1-10) and (110) cleavage planes. Electronic contrast between Al and Ga surface cations enables statistical analysis of the metal sublattice along the non-equivalent <110> directions within the zincblende (001) surface and along the [001] growth direction. The cation distribution is found to be random both along the growth direction and within the growth plane, with no evidence of long-range order or anisotropic growth kinetics; notably, the mean numbers of consecutive cations of the same type along the two in-plane directions are equal, possibly due to statistical averaging over randomly distributed subsurface cations. The results are compatible with either strain-mediated interactions during cation incorporation at the growth front or ideal, uncorrelated cation mixing. Overall, the examined (Al,Ga)Sb
alloy shows an exceptionally high degree of atomic-level homogeneity.
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All authors Hitesh Kumar, Vladimir Kaganer, Zijin Lei, Rüdiger Schott, Werner Wegscheider, Stefan Fölsch
Mesoscale and Nanoscale Physics
Rui-Chang Shen, Yihao Yang and Haoran Xue
High-frequency artificial phononic
crystals offer a low-loss platform compatible with on-chip integration, yet realizing Chern phononic phases at GHz frequencies remains challenging. Here, we propose a
magnon-induced phononic Chern
insulator in a honeycomb phononic
crystal hybridized with
ferromagnetic islands at the hexagon centers. A circularly polarized Kittel mode couples to the surrounding
phonons with a phase winding, which breaks time-reversal
symmetry and opens a full Chern gap. In the large-detuning regime, this mechanism leads to an effective Haldane-type phononic model with
magnon-induced complex hopping. By tuning the
magnon-
phonon interaction, the full hybrid system accesses Chern phases with tunable Chern numbers |C|=1 and |C|=2. The predicted gaps can exceed realistic
phonon and
magnon linewidths, enabling their observation in GHz acoustic devices. Our work establishes
chiral magnon–
phonon hybridization as a route to magnetically reconfigurable topological phononics.
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Materials Science
Topology-Controlled Phonon Dielectric Response Beyond Density Scaling in Metal-Organic Frameworks
Debayan Mondal, Jiahao Ye, Lorenzo Donà et al. (+1 more)
Effective-medium theory treats material porosity as passive dilution. Using ab initio density functional theory and high-resolution synchrotron terahertz (THz) spectroscopy on isochemical zeolitic-imidazolate frameworks, we show that while the electronic permittivity obeys Clausius-Mossotti density scaling, the
phonon contribution violates the conventional density scaling rules. Identical Born charges rule out the role of local chemistry. Instead, the framework connectivity localizes the THz response, where the coherency of
phonon eigenvectors determines the mode-effective charges. Long-range architecture of framework
topology ubiquitous in metal-organic frameworks is therefore a dielectric degree of freedom beyond the density scaling of conventional solids.
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All authors Debayan Mondal, Jiahao Ye, Lorenzo Donà, Jin-Chong Tan
Mesoscale and Nanoscale Physics
Spin preservation in screw-symmetric molecules
Jonas Bloch, Fedor Baranov and Maxim Breitkreiz
In electronic transport through long molecules,
spin is expected to be preserved only when the dwell time is much shorter than the characteristic
spin-mixing timescale $\hbar/\Delta$, where $\Delta$ is the magnitude of a
spin-dependent potential, such as
spin-orbit coupling. We show that, in molecules featuring discrete screw
symmetry,
spin preservation can be enhanced far beyond this timescale owing to strong
spin separation in quasi-momentum. This
spin fidelity in long molecules is consistent with chirality-induced
spin selectivity (CISS), suggesting
spin-dependent transport in long,
chiral molecules with amplified
spin-splitting mechanisms. We provide analytical derivation of the enhanced
spin preservation and test it on tight-binding models, which confirm that the effect gradually weakens when the screw
symmetry is broken or changes from discrete to continuous. Furthermore, we perform transport simulations to show that a strong magnetoresistance trace of
symmetry-protected
spin fidelity emerges in a
spin-valve setup with two
magnetic leads, which we propose as an experimentally accessible signature.
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High Energy Physics (Theory)
Liang Li
We establish a bottom-up model for studying the `would-be' de-Sitter/interface CFT (dS/ICFT) correspondence on the
gravity side, using the Coleman-De Luccia instanton. After absorbing the region where the inflaton changes dramatically by a brane, the spacetime consists of two de Sitter spacetimes with different radii joined by a brane, which is expected to be dual to an interface CFT provided that the dS/CFT
conjecture is correct. Our goal is to analyze existing prescriptions for the
holographic computation of pseudo-
entropy, i.e. the extremal surface in such a spacetime and argue that some of them would cause parodox with the results expected the universal properties of interface CFT and compare our results with that of Anti de Sitter/interface CFT correspondence (AdS/ICFT) after analytic continuation. We also read off the $g$-function from the
entanglement entropy associated with a subregion perpendicular to the interface.
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Fluid Dynamics
Quantum-Inspired Computational Fluid Dynamics for Transient Turbulent Compressible Flows
Shang Xian Matthew Lee, Melissa Kozul, Muhammad Usman et al. (+3 more)
Quantum-inspired
algorithms are an emerging class of
algorithms for computational fluid dynamics (CFD) with potentially favourable scaling for large problems compared to classical methods. However, their applications have been limited to incompressible flows due to arithmetic limitations, which are addressed in this work. This work introduces the first true end-to-end
quantum-inspired computational fluid dynamics (QICFD) solver for direct numerical simulation of the compressible Navier-Stokes equations, that is, all arithmetic operations, as well as initialisation and post-processing, are undertaken in the tensor train (TT) format. Importantly, new division and square-root
algorithms using TTs enable the use of Sutherland's law for viscosity, and leverages recent improvements in TT arithmetic
algorithms for reduced runtime and
memory cost. The new QICFD solver is validated by comparison with the classical CFD solver HiPSTAR and by way of a challenging fluid-flow test case, the low resolution Taylor-Green
Vortex (TGV) at Mach numbers of 0.8 and 0.1. The TGV test case is a transient turbulent case that is very sensitive to accumulating errors, yet our QICFD solver achieves excellent agreement with the classical CFD reference. This work demonstrates the correctness of the new TT division and square-root
algorithms, and that QICFD is capable of compressible flow simulations. The new QICFD solver is also able to perform simultaneous simulations, running multiple TGV-like cases initialised differently in parallel with reduced extra cost. Finally, the demonstrated TGV test case reveals additional challenges of QICFD as well as highlight the need for future advances to make TT methods viable for industrially-relevant conditions.
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All authors Shang Xian Matthew Lee, Melissa Kozul, Muhammad Usman, Martin Sevior, Matthew L. Sims-Goh, Richard D. Sandberg
Nuclear Theory
Optimizing artificial neural networks for dipole strength predictions in light nuclei
Tim Egert, Weiguang Jiang and Sonia Bacca
We present an optimized artificial neural network approach for predicting electric dipole strength functions in
nuclei with $A < 50$. Building upon a previous global study [Phys.Rev.C $\textbf{111}$ (2025) 5, L051308], we focus here on the region of light
nuclei where dipole responses are more structured. The new network incorporates a two-stage training process, a learned
embedding of the
proton number, explicit low-energy dipole onsets, uncertainty-weighted training, and high-energy regularization. Ensemble predictions show improved stability and substantially reduced variability across independently initialized networks compared with the earlier global neural network. Tests on selected isotopes withheld from training show that, for elements represented in the training set, the optimized network captures the main isotope dependent dipole strength systematics. As a further test, we compute electric dipole polarizabilities for selected light
nuclei and compare them with literature values revealing a pronounced sensitivity to the covered energy interval. The resulting set of continuous electric dipole strength functions for
nuclei with $A < 50$ provides a practical complement to existing tabulated photonuclear databases and is particularly suited for applications requiring smooth response functions over broad energy intervals. As an application, we provide an update on the electric dipole polarizability of $^9$Be.
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