Cosmology and Nongalactic Astrophysics
Cosmological inference from the eBOSS QSO full-shape analysis with optimal redshift weights
Xiaoyong Mu, Zhuo-Heng Li, Wentao Luo et al. (+2 more)
We present a full-shape power-spectrum analysis of the eBOSS DR16
quasar sample with optimal
redshift weights. The DR16 QSO catalog contains 343,708
quasars over $0.8<z<2.2$, a
redshift interval broad enough to contain useful light-cone
evolution but not naturally captured by a single effective-
redshift measurement. We construct Karhunen–Loève weights for the parameters of interest and measure the resulting monopole and quadrupole with a cross-correlation
estimator, which remains well defined for sign-changing weights. The theoretical spectra are convolved with the measured
Fourier-space survey-window kernels for each
Galactic cap and weighting scheme, and both the covariance
matrix and the end-to-end validation are based on 1000 EZ light-cone mock catalogs. In $\Lambda$CDM, the
redshift-weighted and standard analyses give consistent constraints, as expected from the near-standard effective
redshifts of the weights targeting $h$, $\Omega_{\rm m}$, and $A_s$. In the Chevallier–Polarski–Linder (CPL) model, the
redshift-weighted DR16 analysis reduces the marginalized uncertainties on $H_0$, $\sigma_8$, and $w_0$ by $43.3\%$, $19.7\%$, and $20.5\%$, respectively, and turns the standard one-sided constraint on $w_a$ into a bounded posterior, $w_a=-0.98^{+1.0}_{-1.3}$. The gain is therefore concentrated where the model contains genuine
redshift evolution, demonstrating that optimal
redshift weighting can recover tomographic information from a wide QSO light cone while keeping the full-shape data vector compact.
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All authors Xiaoyong Mu, Zhuo-Heng Li, Wentao Luo, Yuting Wang, Gong-Bo Zhao
General Relativity and Quantum Cosmology
Non-perturbative, background independent canonical quantum gravity in Fock representations
Thomas Thiemann
It is commonly believed that a
quantum field theory of General Relativity requires a non-perturbative formulation. In addition, the background independence of classical General Relativity supplies a physical selection criterion for suitable
Hilbert space representations of the corresponding
quantum field theory. In this contribution we show that there exist background independent representations of Fock type within the manifestly non-perturbative, canonical approach to
quantum gravity. Mandatory for their existence is the presence of suitable matter fields next to the geometry field. In particular, the excitations of the corresponding Fock
vacuum necessarily entangles matter and geometry. In this article we use the constraint quantisation method. We compare the resulting Fock incarnation of background independent, non-perturbative canonical
quantum gravity with the well known Loop
quantum gravity incarnation. One of the most important differences is that the Fock
quantum gravity (FQG)
Hilbert space, in contrast to the Loop
quantum gravity (LQG)
Hilbert space, is separable. This has many advantages when attempting to implement the
Hamiltonian constraint, also known as Wheeler-DeWitt constraint, as a densely defined quadratic form.
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Quantum Physics
A unified framework for determining transition dipole polarization in solid-state spin defects
Gaia Da Prato, Yong Yu, Wolfgang Tittel et al. (+1 more)
Spin-
photon interfaces based on solid-state defects are key building blocks for scalable
quantum networks and hybrid
quantum platforms. Optimizing light-matter coupling in these systems requires precise knowledge of the optical transition dipole polarization, yet for many promising
quantum emitters this quantity is hard to determine and therefore remains poorly characterized. Here, we develop a framework for reconstructing electric transition dipole polarization in
spin-1/2 solid-state defects directly from ensemble spectroscopy. The approach combines the response of photoluminescence spectra to
magnetic field, optical polarization, and strain. Applied to erbium ions in silicon, a particularly challenging system containing multiple crystallographic subsites, the framework identifies strain-induced shifts as the origin of asymmetric ensemble spectra and enables simultaneous determination of the optical dipole polarization and strain-orbital coupling tensor. The resulting model predicts how cavity-ion coupling depends on crystallographic orientation and
magnetic-field direction, which we verify using single erbium ions coupled to a nanophotonic cavity. Together, these results establish a broadly applicable route for extracting microscopic properties of solid-state
quantum emitters from ensemble spectroscopy and for engineering optimized
spin-
photon and
spin-
phonon interfaces.
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All authors Gaia Da Prato, Yong Yu, Wolfgang Tittel, Simon Gröblacher
High Energy Physics (Theory)
UV completion of 2D Ising CFT:a golden E_8 massless $S$-matrix
Changrim Ahn and Minkyoo Kim
We present a full classification of UV complete QFTs that RG flow to the 2D Ising CFT by solving the bootstrap equations for massless right–left S-
matrices. For the Ising model with E_8 spectrum, we find exactly four completions, arising from higher-T\bar T-type deformations, including a previously unknown “golden flow” whose UV fixed point is a diagonal su(2) coset CFT (c=25/14) along \Delta_rel=2/7. A universal Fibonacci/E_8 structure governs the R–L adjacency
matrices and the Y-system periods, so that the E_8
symmetry persists across all RG scales.
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Solar and Stellar Astrophysics
Radio Diagnostics of Particle Acceleration in Solar Flares with SKAO Observations
Rohit Sharma, Marina Battaglia, Sijie Yu et al. (+3 more)
Particle acceleration is a fundamental astrophysical process occurring across diverse systems and scales, producing electromagnetic emission across all wavelengths.
Radio bursts from astrophysical systems like active
galaxy jets,
solar flares,
pulsars, etc., provide a probe into the emission mechanism and particle acceleration processes. Among all astrophysical phenomena, magnetically driven
solar flares provide unique diagnostics of nonthermal particles due to the advantage of multiple spatial-temporal and spectral measurements. The subsequent emitted radiation spans various sections of the
radio spectrum. Based on brightness temperature and spectrum, one can distinguish between bright
plasma emission or 'nonthermal' emission. Nonthermal
radio bursts in meter and microwave bands arise from suprathermal particles, while the surrounding
plasma produces fainter thermal emission. High spatial-temporal studies along with polarimetry will enable tracking of electron beams in evolving
magnetic fields and constrain coronal properties such as
magnetic strength, density, and temperature. Fine spectral structures from gyrosynchrotron bursts allow mapping of
magnetic fields along acceleration tracks. However, emissions from the more numerous, weaker particle populations remain difficult to observe. Particles in
solar flares follow a power-law energy distribution, with weaker populations being more common. The Square Kilometre Array Observatory (SKAO) will provide high-fidelity data that will enable detailed characterisation of these populations, statistical studies of particle beams, and insights into their interaction with
magnetic topologies. Its high-resolution (especially SKA-Mid) and multi-wavelength synergy (EUV, X-rays) will refine diagnostics of coronal and acceleration-region properties. This chapter reviews particle acceleration models and expected advances from SKAO.
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All authors Rohit Sharma, Marina Battaglia, Sijie Yu, Hamish Reid, Eduard Kontar, Bin Chen
Quantum Physics
Properties of 2D Electron or Hole Gases at Tailored s-Si/SiGe Interfaces: A First-Principles Investigation
Garima Ahuja, Farha S, Tanuja Shridhar Joshi et al. (+2 more)
We have performed first-principles hybrid density functional theory calculations to study the formation and properties of two-dimensional electron or hole gases (2DEG or 2DHG) at s-Si/SiGe interfaces. For small Ge concentrations $x < 0.25$, we find a novel type of band
alignment with no offset in the conduction bands, implying that a 2DEG cannot be formed, though a 2DHG can. In contrast, for $x > 0.25$ the band
alignment suggests that either a 2DEG or 2DHG can be formed. The electronic band structure features two nearly degenerate 2DEG states at the bottom of the conduction bands, and two 2DHG states at the top of the valence band. These states can be accessed by appropriate doping and gating. Charge density plots of these states show that they feature carriers confined to the near vicinity (2–3 atomic layers) of the interface. Calculated effective masses are anisotropic, being markedly so for the 2DHG states, and in excellent agreement with experiment. This property can be exploited to create a 1D carrier gas. Our results are especially important for s-Si/SiGe-based semiconducting
spin qubits for
quantum computing applications.
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All authors Garima Ahuja, Farha S, Tanuja Shridhar Joshi, Anil Shaji, Shobhana Narasimhan
Quantum Physics
Bipartite Gaussian Boson Sampling for Hamiltonian Cycles in Directed Graphs
Miaomiao Yu, Jingyi Lv, Yan Wang et al. (+2 more)
Bipartite Gaussian
boson sampling (BipartiteGBS) produces output probabilities governed by squared permanents of submatrices of arbitrary complex
matrices, matching the nonsymmetric structure of directed graphs. Most GBS-based graph
algorithms, however, rely on symmetric hafnian structure and are formulated for undirected problems. Here we propose a BipartiteGBS-based framework for directed-graph heuristic optimization. We introduce Max-Perm as a canonical optimization task for BipartiteGBS and derive a closed-form sampling enhancement factor relative to uniform classical sampling in this idealized setting. We then use permanent-biased BipartiteGBS samples to guide a genetic
algorithm for the celebrated directed
Hamiltonian cycle problem. Numerical experiments on Erdős–Rényi random directed graphs show that the resulting BipartiteGBS-enhanced
algorithms improve success rates over a standard genetic
algorithm and yield longer valid paths when no
Hamiltonian cycle is found, while ablation tests indicate that BipartiteGBS-guided initialization is the dominant contributor. These results show how permanent-based photonic sampling can provide useful algorithmic guidance for asymmetric combinatorial search.
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All authors Miaomiao Yu, Jingyi Lv, Yan Wang, Kun Wang, Ping Xu
Quantum Physics
Linear and nonlinear optical torque in multi-level atomic systems driven by counter-rotating orbital angular momentum fields
Dharma P. Permana, Mažena Mackoit Sinkevičienė, Viačeslav Kudriašov et al. (+3 more)
We investigate the generation of optical torque in coherently prepared multi-level atomic media driven by a vector
vortex beam composed of two counter-rotating components carrying opposite orbital angular momenta, $+l\hbar$ and $-l\hbar$. We consider a three-level $\Lambda$ configuration and a four-level tripod configuration. Using a perturbative steady-state solution of the optical Bloch equations, we obtain analytical expressions for both linear and nonlinear contributions to the optical torque. The results show that the torque is strongly controlled by atomic coherence, including the initial population imbalance and the relative phase between the
vortex components. Nonvanishing torque can arise even when the two components have equal amplitudes, due to coherence-induced asymmetry in the atomic response. In the tripod configuration, the presence of a strong control field leads to electromagnetically induced transparency, which suppresses the torque near resonance and shifts the dominant response to finite detunings. These results establish a route for controlling light-induced rotational dynamics in atomic media using vector
vortex fields, with potential applications in coherent optical manipulation and angular-momentum-based control in
quantum systems.
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All authors Dharma P. Permana, Mažena Mackoit Sinkevičienė, Viačeslav Kudriašov, Julius Ruseckas, Gediminas Juzeliünas, Hamid R. Hamedi
Astrophysics of Galaxies
Low cosmic-ray ionisation at parsec scales in G035.39-00.33
Andrea Socci, Ashley Barnes, Jaime Pineda et al. (+11 more)
Cosmic rays (CRs) regulate the chemical
evolution of the gas and its coupling to the
magnetic field in the densest and coldest regions of the interstellar medium (ISM). However, the CR ionisation rate of H$_2$ ($\zeta_2$) is one of the most debated parameters characterising molecular clouds due to the uncertainties in its estimation. We developed a new analytical framework based on the chemistry of N$_2$H$^+$, N$_2$D$^+$ and DCO$^+$ to overcome observational limitations in current estimates of $\zeta_2$ and to probe the latter and the electron fraction, $x(e)$, in the gas across multiple density regimes. We applied this method towards the parsec-scale filament of the infrared dark cloud (IRDC) G035.39-00.33 with new observations from the NOrthern Extended Array (NOEMA) at a resolution of $3''$ (or $\sim9000$ au). Ancillary observations of C$^{18}$O complete this survey to measure $x(e)$ and $\zeta_2$ in G035.39-00.33. CO depletion is widespread in G035.39-00.33 with factors, $f_\mathrm{D}$, positively correlated with column and number densities of H$_2$ in the cloud. The deuterium fractions ($R_\mathrm{D}$) are enhanced towards these same sites in which the corresponding electron fraction values cluster below $\lesssim10^{-8}$. $\zeta_2$ varies by three orders of magnitude in G035.39-00.33 ($\sim10^{-18}-10^{-15}$ s$^{-1}$) with a median of $\sim2.3\times10^{-18}$ s$^{-1}$, consistent with those reported for other IRDCs and
giant filaments, but on average lower than the typical $\zeta_2$ for the ISM. $\zeta_2$ shows a functional dependence on $N(\mathrm{H_2})$, but with absolute values lower compared to those predicted by theoretical models. This behaviour suggests the presence of an overall attenuation of the CR flux taking place in G035.39-00.33. The CR flux appears to be reduced by the change in
magnetic field strength and morphology previously reported in the region.
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All authors Andrea Socci, Ashley Barnes, Jaime Pineda, Olli Sipilä, Caroline Gieser, P. Caselli, Alvaro Hacar, Giuliana Cosentino, Chi-Yan Law, Morgan T. Owen, Prasanta Gorai, Francesco Fontani, Isazkun Jiménez-Serra, Jonathan C. Tan
Fluid Dynamics
The intrinsic decomposition of vorticity dynamics on an arbitrarily moving and deforming boundary
Tao Chen
Boundary vorticity dynamics provides a rigorous theoretical foundation for understanding vorticity creation at boundaries, vorticity-boundary interactions, as well as the rational design of effective boundary flow control strategies. It cornerstone is the boundary vorticity flux (BVF), first introduced by Lighthill in 1963, which quantities the local rate of vorticity production at a boundary, and thereby serves as a mathematical measure of distributed vorticity source strength. By adopting a differential-
geometric approach, we develop a general theory of the intrinsic decomposition of BVF for compressible Newtonian fluid interacting with an arbitrarily moving and deforming boundary surface. The analyses are further extended to the decomposition of boundary enstrophy dynamics, centered on the boundary enstrophy flux (BEF). Beyond the existing literature, the new theory explicitly identifies a complete set of boundary sources for the rigid-rotation and
spin modes, as well as for various enstrophy constituents, arising from the interplay among external force, surface geometry and kinematics, and both longitudinal and transverse physical processes on a deformable boundary. It is noteworthy that introducing a conjugate
curvature tensor pair consistently yields compact mathematical representations for all source terms, manifesting as bilinear (or quadratic-form-type) couplings between fundamental vortcity modes and the surface
curvature tensors, irrespective of the complexity or generality of the boundary kinematics.
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Mesoscale and Nanoscale Physics
Multi-level {\pi}-junction in a proximitized Ge/SiGe quantum dot probed by an on-chip superconducting microwave resonator
Luigi Ruggiero, Vera Jo Weibel, Pauline Drexler et al. (+5 more)
Using on-chip microwave measurements, we investigate multilevel $\pi$-junctions formed by proximitized
quantum dot (QD) in a germanium (Ge)/silicon-germanium (SiGe)
heterostructure. In the multilevel regime, where several QD orbitals contribute simultaneously to superconducting transport, the Josephson ground state is no longer determined solely by the occupation of a single orbital. By combining DC transport and microwave techniques, we identify the qualitative signatures of multilevel $\pi$-junctions in both their gate-voltage dependence and microwave response. In particular, we observe combinations phase transitions that are sharp or smooth in gate voltage and which exhibit distinct inductive and dissipative signatures. Such multilevel Josephson transport has previously been observed primarily in exceptionally clean systems such as carbon nanotubes. Our results establish proximitized Ge as a platform for investigating hybrid
superconductor/
semiconductor physics and demonstrate the integration of gate-defined superconducting
quantum devices with high-quality on-chip microwave resonators.
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All authors Luigi Ruggiero, Vera Jo Weibel, Pauline Drexler, Carlo Ciaccia, Christian Olsen, Dominique Bougeard, Christian Schönenberger, Andrea Hofmann
Fluid Dynamics
Quadruple decomposition of boundary vorticity flux
Tao Chen and Tianshu Liu
First introduced by Lighthill in 1963 for two-dimensional flows and later generalized by Jie-Zhi Wu to three-dimensional scenarios since 1986, the boundary vorticity flux (BVF) is the cornerstone of boundary vorticity dynamics, which quantifies the vorticity source strength on a solid boundary. Recent advances in vorticity and
vortex dynamics have revealed both the rigid-rotation and
spin modes of vorticity from multiple perspectives. In the present study, we propose a novel quadruple decomposition of the BVF on a stationary solid wall, which essentially uncovers the boundary creation rates of the elementary vorticity modes for both the tangential and wall-normal BVF components, respectively. The proposed framework is illustrated through skin-friction and surface-pressure measurements for flow over a hill model in a low-speed wind tunnel, revealing a set of intriguing BVF patterns for the first time. These theoretical results are expected to be valuable for global surface flow diagnostics when combined with experiments, as well as for understanding the formation mechanisms of near-wall coherent structures and flow-induced noise.
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Astrophysics of Galaxies
M. J. Hardcastle, C. Konar, S. Dutta et al. (+10 more)
Radio-luminous active
galactic nuclei, or
radio galaxies, are the brightest population of objects in the extragalactic
radio sky and will be seen in large numbers in essentially every SKA observation. Despite having been studied for more than seventy years, some aspects of
radio galaxy physics are still poorly understood, and the SKA will shed light on this by enabling the generation of very large samples of high-resolution, sensitive, broad-band images of
radio galaxies, allowing us to probe, for example, regions of particle acceleration, spectral ageing, and the
magnetic field structures both internal and external to the
radio lobes. A key feature of the
radio galaxy population is that observations of extended sources probe the past history, and thus the duty cycles, of
accretion onto the central supermassive black hole, and we discuss ways in which the SKA will improve our understanding of episodic and dying
radio galaxies in particular.}
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All authors M. J. Hardcastle, C. Konar, S. Dutta, D. V. Lal, R. D. Baldi, M. Brienza, A. Hota, M. Kunert-Bajraszewska, B. Mingo, M. Pandey-Pommier, K. Rubinur, S. Shabala, E. Vardoulaki
Statistical Mechanics · Cross-listed from cs.LG
A Path-Space Formulation of Prediction in World Models: From a Single Action to Prediction, Planning, and Irreversibility
Gunn Kim
We propose a path-space formulation of prediction in AI world models. Rather than sequences of one-step conditional distributions, we argue that a world model implicitly defines a probability measure over future trajectories. In the local regime where latent dynamics admit an effective Markovian description, this path measure takes the Onsager-Machlup form. Within this framework, prediction (most probable trajectory), planning (constrained optimization), and uncertainty (fluctuations) emerge as operations on a single action functional. We decompose the latent dynamics into reversible and irreversible components and introduce operational measures of
entropy production from model rollouts. In controlled small-scale
attention-based models, we find that
attention asymmetry is acquired during training in proportion to the irreversibility of the data. Symmetrizing the learned
attention suppresses
entropy production and selectively degrades long-horizon prediction of irreversible dynamics while preserving relaxational prediction. These results suggest that irreversibility may serve as a computational resource for predictive world models. More generally, the fundamental predictive object is a distribution over future paths rather than states.
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Quantum Physics
Dissipative phase decision without ground-state preparation
Hao-En Li, Yilun Yang and Lin Lin
We propose a dynamical approach to identifying ground-state
quantum phases through short-time dissipative cooling. Rather than determining the phase by preparing highly accurate approximations to ground states, we prepare a representative state of a candidate phase and monitor the early-time response of phase-sensitive observables under cooling dynamics tailored to the target
Hamiltonian. For a class of phase-decision problems in which the relevant observables can be inferred from the low-energy
manifold, and with jump operators implementable using only short-time
Hamiltonian simulation, the dissipative
evolution rapidly suppresses high-energy components and drives the system into a low-energy
manifold whose observables already reveal the underlying ground-state phase, well before mixing to the steady state. We demonstrate this strategy for the frustrated $J_1$–$J_2$ Heisenberg chain, the Kitaev honeycomb model, and the XXZ chain, including Berezinskii–Kosterlitz–Thouless and topological phase transitions. In particular, coarse filter resolutions and short
evolution times suffice to recover phase-sensitive quantities such as the Luttinger parameter and topological diagnostics. We further provide theoretical justification that cooling dynamics with such jump operators can rigorously prepare low-energy
manifolds for free-fermionic and free-bosonic systems, and investigate this mechanism for interacting fermionic systems. Our results suggest that phase decision is a plausible target for future utility-scale studies on early fault-tolerant
quantum devices.
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Optics
Reflection and Refraction at Nonlinear Temporal Boundaries in Synthetic Lattices
Chong-Xiao Chen, Zheng-Wei Zhou and Xi-Wang Luo
Temporal boundaries in time-modulated media provide a powerful route toward wave manipulation beyond conventional spatial boundaries. Here, we investigate nonlinear temporal boundaries generated by interaction quenches in a synthetic
lattice with exactly solvable interacting dynamics. Unlike conventional temporal boundaries arising from abrupt changes of single-particle dispersion, the present system realizes a self-induced temporal medium in which the propagating wave packet dynamically determines its own effective dispersion and transport properties. By solving the nonlinear Schrödinger dynamics analytically, we show that the interaction generates an emergent wave-packet-dependent band structure and a state-dependent temporal refractive response while preserving fully controllable
evolution. Based on this framework, we establish a nonlinear temporal-scattering picture and uncover phenomena including amplitude-dependent temporal reflection/refraction and nonlinear temporal birefringence. Furthermore, we demonstrate that gradient-induced Bloch oscillations suppress wave-packet
diffusion and enable coherent periodic transport with exact state reconstruction. Our results extend temporal reflection and refraction from dispersion-quenched linear systems to interaction-quenched nonlinear media and provide a tractable framework for nonlinear wave manipulation in synthetic
lattices.
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Plasma Physics
Simulation Study of Coupling Effects Between a Hall Thruster and a Power Processing Unit
Zirui Fan, Yinjian Zhao, Jingjing Li et al. (+4 more)
The complex and nonlinear load characteristics of
Hall thrusters remain a key challenge in the design of propulsion power-supply output stages. In existing power-supply simu-lations for electric propulsion systems, the
Hall thruster is often simplified as a fixed im-pedance or a prescribed current source, which makes it difficult to capture the real-time interaction between the power-supply output stage and the thruster discharge process. To address this issue, this study encapsulates a one-dimensional discharge model as an externally callable thruster slave and proposes a HallThruster.jl-Saber-Simulink co-simu-lation method. The proposed method enables synchronized closed-loop exchange be-tween the power-port voltage Vcmd and the thruster discharge current Iout . The results show that the discharge current under the co-simulation condition exhibits a sustained low-frequency response at approximately 11 kHz. Compared with a fixed-voltage standalone simulation, the co-simulation shows observable differences in port waveforms, spectral characteristics, and internal field distributions. This method provides a co-simu-lation basis for realistic load analysis of propulsion power supplies and subsequent stress evaluation of key components.
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All authors Zirui Fan, Yinjian Zhao, Jingjing Li, Yingying Tian, Leilei Shi, Suliang Wu, Liqiu Wei
Superconductivity
Anomalous Behavior of the Ni$^{1+}$ moment in bi-infinite-layered La$_3$Ni$_2$O$_5$F
Young-Joon Song, W. E. Pickett and K.-W. Lee
The discovery of superconductivity in hole-doped Ni$^{1+}$ systems with “infinite layer" NiO$_2$ square-
lattices analogous to the Cu$^{2+}$ CaCuO$_2$ cuprate has renewed conflicting pictures of the Cu$^{2+}$$-$Ni$^{1+}$ similarities and distinctions. Recent synthesis of formal Ni$^{1+}$ La$_3$Ni$_{2}$O$_{5}$F with two infinite NiO$_{2}$ layers per
cell provides a novel member of this class. We find that Ni$^{1+}$ in this material is unusually flexible. First principles density functional theory studies reveal a single partially occupied electron band derived from density in three interstitial layers that provides self-doping to a Ni$^{1.09+}$ charge state. The blocking La(O/F)La layer provides isolation of the NiO$_2$
bilayer to strictly two-dimensional electronic and
magnetic systems. Fixed
spin moment calculations of
magnetic tendencies reveal behavior unlike previous nickelates, including an essentially vanishing differential susceptibility up to a large
magnetic field and a metastable
ferromagnetic (FM) state.
Antiferromagnetic (AFM) order is favored energetically as expected; surprisingly both FM and AFM states are obtained without correlation (Hubbard $U$) corrections. Doping away from half-filling by an interstitial density derived band and likely two-dimensional fluctuations account for the lack of observation of any
magnetic transition.
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Superconductivity
Distinct Roles of Hydrogen in Superconducting and Ferromagnetic Phases of CoZr$_{2}$H$_{x}$
Yuto Watanabe, Takayoshi Katase, Daisuke Takegami et al. (+1 more)
Hydrogenation offers a versatile route to tuning the physical properties of intermetallic compounds. In this study, we synthesized CoZr$_{2}$H$_{x}$ with different hydrogen contents and found that hydrogen is incorporated in two distinct concentration regimes separated by a wide composition gap: a low-concentration hydrogenated superconducting phase ($x$ = 0-0.054) and a high-concentration hydrogenated
ferromagnetic phase ($x$ = 2.786). Hydrogen plays fundamentally different roles in the two concentration regimes. In the high hydrogen concentration phase, the Zr-H interactions substantially modify the metallic bands crossing the
Fermi level, leading to the emergence of ferromagnetism. In contrast, in the low hydrogen concentration phase, hydrogen behaves as a nonmagnetic
impurity without altering the electronic band structure. Despite the nearly identical Debye temperatures across the low-concentration series, the superconducting transition temperature ($T_{\mathrm{c}}$) is progressively suppressed with increasing hydrogen content.The observed $T_{\mathrm{c}}$ suppression is quantitatively described by the Abrikosov-Gor'kov pair-breaking theory, indicating that the superconducting gap of CoZr$_{2}$ is anisotropic or multigap rather than a fully isotropic $s$-wave
symmetry.
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All authors Yuto Watanabe, Takayoshi Katase, Daisuke Takegami, Yoshikazu Mizuguchi
Instrumentation and Methods for Astrophysics
Enhancing VLBI Capability with the SKA-Mid and the Jingdong 120-m Radio Telescope
Wen Chen, Jun Yang, Zhixuan Li et al. (+2 more)
The Jingdong
Radio Telescope (JRT) is a 120-meter fully steerable
radio telescope currently under construction in Jingdong County, Yunnan Province, China. Located at a relatively low latitude (24.5 degree), the JRT will enable observations of nearly 90% of the sky. Equipped with two broadband single-pixel receivers covering 1-8 GHz and 6-18 GHz, and a powerful digital backend, the
telescope will support single-dish studies of various
radio sources-particularly millisecond
pulsars for enhancing the detection of nanohertz gravitational waves. In addition to single-dish capabilities, the JRT is expected to contribute approximately 800 hours annually to international Very Long Baseline Interferometry (VLBI) observations via a standard VLBI backend. When operating in conjunction with the phased-up SKA-Mid, the JRT will significantly enhance the technical and scientific capabilities of existing VLBI networks. This paper presents a comprehensive overview of the JRT's VLBI module and explores its potential to improve joint VLBI observations with current VLBI networks. Our analysis suggests that coordinated VLBI observations involving both the SKA-Mid and the JRT have the potential to significantly advance the field. For early sciences, we also highlight a few highly promising scientific cases, e.g. measuring the distance to PSR J0437-4715 with <1 ly accuracy and exploring jet formation with an event-horizon-scale resolution in M60*.
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All authors Wen Chen, Jun Yang, Zhixuan Li, Yingjie Li, Niu Liu
Instrumentation and Methods for Astrophysics
VLBI-Enabled Localization of Continuous GW Sources
Keitaro Takahashi, Takuya Akahori, Kenta Fujisawa et al. (+8 more)
Pulsar timing arrays (PTAs) are opening the nanohertz gravitational-wave (GW) band by timing millisecond
pulsars (MSPs) to target signals from supermassive black hole binaries (SMBHBs). Beyond evidence for a
stochastic background, a central SKA-era objective is detecting individual continuous-wave (CW) sources. The scientific payoff hinges on localization: conventional PTA searches yield uncertainties of tens-hundreds of deg$^2$, too large to identify a unique host, obtain a
redshift, infer intrinsic masses, or pursue electromagnetic counterparts. This limitation is chiefly
geometric: the CW response includes Earth and
pulsar terms, and poorly known
pulsar distances make the
pulsar-term phase a free parameter that degrades triangulation. If distances to a few MSPs are known to better than a GW wavelength ($\sim$ 1 pc), these phases are fixed and localization improves by orders of magnitude. Simulations indicate that with sub-parsec distances for a handful of nearby MSPs, the uncertainty can shrink to $\sim 10^{-3}$ deg$^2$ (arcminute scale), enabling unique host association and multi-messenger follow-up. Achieving such distances requires $\sim$ 10 $\mu$arcsec parallaxes for MSPs within a few hundred parsecs, a precision now approached with Very Long Baseline Interferometry (VLBI) and expected to become practical with phased-array SKA1-Mid operating as a sensitive VLBI element. SKA1's multi-beam, multi-calibrator astrometry will provide the independent distance priors needed for PTAs to localize nanohertz GW sources and measure SMBHB parameters and environments. We assess VLBI's role in PTA CW searches and propose a concrete SKA1-Mid observing strategy for nearby MSPs to deliver the required sub-parsec distances.
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All authors Keitaro Takahashi, Takuya Akahori, Kenta Fujisawa, Hiroshi Imai, Hajime Kita, Hideyuki Kobayashi, Hiroaki Misawa, Kotaro Niinuma, Tomoaki Oyama, Kazuhiro Takefuji, Fuminori Tsuchiya
High Energy Physics (Phenomenology)
Vector-Like Lepton Pair Production With Polarized Beams at Linear Colliders:Sensitivity Projections and Chirality Observables
Haroon Sagheer, Ijaz Ahmed and Jamil Muhammad
We study pair production of a vector-like
lepton doublet at polarized future linear
colliders, focusing on the charged and neutral channels $e^+e^-\to\tau^\prime\bar{\tau}^\prime$ and $e^+e^-\to\nu^\prime\bar{\nu}^\prime$. The
benchmark masses are $M_{\rm VLL}=1000,1200~{\rm GeV}$ at CLIC with $\sqrt{s}=3~{\rm TeV}$ and $M_{\rm VLL}=390,460~{\rm GeV}$ at ILC with $\sqrt{s}=1~{\rm TeV}$. Using the realistic polarization configurations LR$=(-0.8,+0.3)$, RL$=(+0.8,-0.3)$, LL$=(-0.8,-0.3)$, and RR$=(+0.8,+0.3)$, we evaluate tree-level production-level cross sections and construct observables designed to test the electroweak structure of the doublet. The charged channel is consistently larger than the neutral channel because it receives both
photon and $Z$ exchange. In the LR configuration, the charged-channel rates reach $23.32$ and $20.28~{\rm fb}$ at CLIC, and $188.83$ and $129.04~{\rm fb}$ at ILC, for the two
benchmark masses at each
collider. We express rate reach through the projected visible-fraction requirement $f_{\rm vis}^{95}=3/(\mathcal{L}\sigma_{\rm prod})$, keeping the result independent of a specific decay selection. To quantify charged–neutral separation we use the absolute discriminator $D_\sigma$, which reaches about $0.546$ at CLIC and $0.542$ at ILC in the LR
benchmark. We also find a stable observed asymmetry separation, $|\Delta A_{LR}^{\rm obs}|\simeq 0.45$–$0.46$, between the charged and neutral channels. The corresponding production-level statistical projection gives sizeable $Z_A$ values for the
benchmark luminosities, scaling as $\sqrt{\mathcal{L}_{\rm tot}f_{\rm vis}}$ under an equal LR/RL luminosity split. These results demonstrate that the beam polarization can provide a representation-sensitive diagnostic of vector-like
lepton doublets, beyond a simple rate enhancement.
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Materials Science
Emergence of half-semiconductor behavior and tunable magnetism via carrier doping in Janus VXSe (X=Cl, Br, I) monolayers
Zhixiang Wang, Aining Wang, Zikui Ye et al. (+5 more)
Two-dimensional
ferromagnetic semiconductors with high Curie temperature, large
magnetic anisotropy, and electrically tunable properties are highly sought for nanoscale spintronics. Here, using first-principles calculations, we predict a new class of Janus VXSe (X=Cl, Br, I) monolayers. All three compounds are intrinsic
ferromagnetic semiconductors with indirect band gaps of 1.66-2.33 eV, Curie temperatures up to 128 K, and
magnetic anisotropy energies up to 910 ueV per V, leading to easy-plane magnetization for VClSe and VBrSe and an out-of-plane easy axis for VISe. The robust
ferromagnetic order originates from the competition between superexchange and itinerant magnetism. Remarkably, VISe is a pristine half-
semiconductor, whereas carrier doping unlocks fully
spin-polarized states in the initially non-ideal VClSe and VBrSe. We also find that hole doping can switch the
magnetic easy axis of VBrSe from in-plane to out-of-plane, enabling a
spin-field-effect transistor with
giant magnetoresistance. Our findings highlight carrier doping as a key to unlock hidden half-semiconducting behavior and establish Janus VXSe as a promising platform for 2D spintronics and magnetoelectric devices.
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All authors Zhixiang Wang, Aining Wang, Zikui Ye, Yuqiao Qu, Qian Zheng, Yiding Liu, Qiang Fan, Gang Yao
Statistical Mechanics
Forward-backward correspondence between stationary structure and splitting probabilities in active matter
Derek Frydel
Active particles confined by hard walls accumulate at boundaries and may become dynamically adsorbed due to directional persistence. In this work, we show that the same persistence mechanism also gives rise to a finite wall splitting probability, meaning that a particle initialized at a wall can reach the opposite boundary before returning to its starting point. By comparing forward and backward
evolution equations directly in position–velocity phase space, we derive exact relations linking stationary distributions and splitting probabilities for run-and-tumble, active Brownian, and active Ornstein–Uhlenbeck particles. In particular, we show that the stationary density is generated by the spatial derivative of the splitting probability, while the distribution of dynamically adsorbed particles at the walls is encoded in wall splitting probabilities. The correspondence is valid in arbitrary spatial dimension and establishes an exact bridge between stationary and first-passage descriptions of confined active matter, revealing them as complementary representations of the same persistence-driven dynamics.
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Medical Physics
NGSE-Corr: A technique for objective clinical evaluation of quantitative-imaging methods without a gold standard
Yan Liu, Ziping Liu, Zekun Li et al. (+4 more)
Objective evaluation of quantitative-imaging (QI) methods based on how reliably they measure true values is important for clinical translation. Performing such evaluation with patient data is highly desirable but hindered by the lack of gold standards. To address this challenge, advancing on previous studies, we propose a no-gold-standard evaluation technique, NGSE-Corr, that objectively evaluates QI methods without true values. The technique assumes a linear
stochastic relationship between true and measured values, characterized by a slope, bias, and multivariate Gaussian-distributed noise term that models correlated noise across QI methods. We derive a maximum-likelihood approach to estimate these parameters using only measured values. From the estimates, we compute noise-to-slope ratio (NSR) to rank QI methods based on precision. Numerical experiments showed that NGSE-Corr reliably estimated the NSR, accurately ranked methods, and maintained performance even when assumptions made by the technique were partially violated. We also validated NGSE-Corr in an in silico imaging trial to rank three quantitative SPECT methods for measuring regional activity uptake in patients with bone metastatic castrate-resistant prostate cancer treated with radium-223. NGSE-Corr correctly identified the most precise QI method and ranked the methods for 95% (95% CI, 89%-98%) and 91% (95% CI, 84%-95%) of trials, respectively, with data from 50 patients. Performance further improved with larger cohorts. With 200 patients, NGSE-Corr yielded same rankings as those obtained with true values across all trial instances. These findings demonstrate the ability of NGSE-Corr to accurately rank QI methods without gold standards and motivate clinical validation and broader applications.
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All authors Yan Liu, Ziping Liu, Zekun Li, Jingqin Luo, Daniel L. J. Thorek, Barry A. Siegel, Abhinav K. Jha
High Energy Physics (Phenomenology)
Heavy mesons from the QCD instanton vacuum beyond the static limit
Ki-Hoon Hong, Yongwoo Choi, Nurmukhammad Rakhimov et al. (+1 more)
We study pseudoscalar heavy
mesons in the QCD instanton
vacuum beyond the static limit. Finite-mass effects in the heavy-light loop are encoded in a separable effective vertex built from a profile function $\phi(\vec{p})$, kept distinct from the static Wilson-line form factor $F_Q^{(\infty)}(\vec{q})$ of the $m_Q\to\infty$ limit. The pseudoscalar two-point function fixes the residual mass $\Lambda$ and the residue-normalized
meson-
quark coupling, from which we evaluate the decay constant and the
spin-independent kinetic
matrix element including the retained $1/m_Q$ derivative and kinetic contributions. The Isgur-Wise function is evaluated separately in the static heavy-
quark limit, and its zero-
recoil slope is extracted by using the same residue-normalized heavy-light vertex. The subleading calculation is restricted to the kinetic (derivative) part of the HQET operators. For a representative vertex, calibrated at fixed $m_b^{\mathrm{eff}}=5.04\,\mathrm{GeV}$ to the leading-order decay constant $f_B^{\mathrm{LO}}=180.0\,\mathrm{MeV}$ and the
spin-averaged mass $\bar{m}_B=5.313\,\mathrm{GeV}$, we obtain $\delta f_B^{(1/m_Q,\mathrm{partial})}=+121.9\,\mathrm{MeV}$ and $f_B^{\mathrm{partial}}=301.9\,\mathrm{MeV}$, $\Lambda=190.7\,\mathrm{MeV}$, $\lambda_1^{(\partial)}=-0.773\,\mathrm{GeV}^2$, and $\rho_{\mathrm{IW}}^2=1.153$. The kinetic contribution yields a mass shift of order $\Lambda/2$ and a sizable partial $1/m_Q$ correction, indicating that the
spin-independent nonperturbative $1/m_Q$ sector is a sensitive probe of the finite-mass heavy-light vertex.
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All authors Ki-Hoon Hong, Yongwoo Choi, Nurmukhammad Rakhimov, Hyun-Chul Kim
Quantum Physics
Quantum Counterparty Credit Risk: A Study of Path-Dependent Derivatives
Sandeep Jha, Richard Oentaryo, Sanjay Sekaran et al. (+7 more)
Estimating potential future exposure (PFE) for path-dependent derivatives, such as FX Target Redemption Forwards (TARFs), represents a formidable computational challenge due to the demand of nested Monte Carlo simulations. We present a hybrid
quantum-classical framework that leverages Iterative
Quantum Amplitude Estimation (IQAE) to address this via a reduced-order counterparty credit risk model. Our methodology maps the non-linear TARF payoff – including cumulative gains and knock-out features – into a
quantum circuit via a two-step formulation, whereby a first-step percentile is computed classically and then used to condition
quantum evaluation of subsequent exposure. We employ discretisation of the FX process and a linearised additive approximation of dynamics to enable implementation on current
quantum platforms. Developed via the Classiq platform and validated on NVIDIA CUDA-Q and Amazon Braket SV1, our approach achieves relative errors of 1%-8% against classical
benchmarks at the 97.5% and 99% confidence levels. While discretisation constraints and approximate monotonicity assumption may introduce bias and limit recovery of the full exposure distribution, our framework offers a tractable testbed for
quantum acceleration. Scaling analysis suggests that $\sim$300 logical
qubits could enable full 52-week exposure estimation, reducing sample complexity for tail-risk estimation via amplitude estimation at the cost of increased
circuit depth.
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All authors Sandeep Jha, Richard Oentaryo, Sanjay Sekaran, Vadym Kullish, Rajanikanth Annam, Paul Griffin, Hanan Rosemarin, Nadav Yoran, Nati Erez, Rei Sato
High Energy Physics (Phenomenology)
Gravitational waves from graviton bremsstrahlung in scalar leptoquark decays
Qian-Jiu Wang, Hua Tong and Zhao-Huan Yu
We study the
stochastic gravitational wave background originated from graviton bremsstrahlung in decays of scalar leptoquarks, which are colored scalar
bosons simultaneously coupling to a
quark and a
lepton. We take the scalar leptoquarks in the $\mathrm{SU}(5)$ grand unified theory as a concrete example. Stringent experimental bounds on
proton decay force these particles to be superheavy, which in turn renders their graviton bremsstrahlung, induced by
quantum gravity effects, less suppressed. By solving the relevant Boltzmann equation, we trace the
evolution of the scalar leptoquark number density in the early universe and use it to compute the resulting gravitational wave spectrum. We find that high-frequency gravitational wave detectors employing resonant cavity techniques offer a promising means to probe such signals.
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Quantum Physics
Detecting entanglement of non-Gaussian continuous-variable states from single-copy homodyne measurements
Moritz Straeter, Michael Tsesmelis and Leong-Chuan Kwek
The
entanglement of Gaussian continuous-variable (CV) states is fully determined by the state's second moments. In contrast, some entangled non-Gaussian states evade every second-moment criterion, and non-Gaussian
entanglement detection remains an experimental challenge. The $p_3$-PPT criterion detects
entanglement using moments of the partial transpose of the density
matrix. This criterion was recently extended to CV systems using
photon-number-resolving detectors and multi-copy interferometry; here we introduce a single-copy homodyne protocol that detects bipartite CV
entanglement via the same criterion. Unbiased U-statistic
estimators for the partial-transpose moments $p_2$ and $p_3$ are constructed directly from randomized homodyne data and used to evaluate the $p_3$-PPT
entanglement witnesses: a linear one for detection, and a quadratic one whose violation yields a dimension-free lower bound on the
entanglement negativity. The protocol estimates $p_2$ and $p_3$ up to additive error $\varepsilon$ at Fock cutoff $N$ from $O((N+1)^{14/3}/\varepsilon^2)$ measurements at fixed confidence. We demonstrate the protocol on six families of Gaussian and non-Gaussian states, reaching $95\%$ empirical one-sided detection probability from $\sim 10^3$ to $10^4$ homodyne measurements for states with $\bar{n} \approx 2$, placing non-Gaussian
entanglement detection within reach of current homodyne experiments.
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Quantum Physics
High-Fidelity Hole Spin Qubits Reveal Quadrupolar Nuclear-Bath Dynamics in Isotopically Purified Planar Germanium
Jian Zeng, Xiangjun Tan, Hongzhang Wang et al. (+10 more)
Planar Germanium has emerged as a promising platform to build
spin-based large scale
quantum computers. By exploiting the anisotropic hyperfine interaction of holes in Ge,
qubits with long T2* have been recently realized. While the performance of single
qubits is still more or less limited by 73Ge
nuclear spin fluctuations, the site-to-site variation of
qubit sweet spot becomes obstacles to maintaining high fidelity of each
qubit across the whole wafer. To achieve high performance Ge-based
quantum circuit, it is therefore essential to eliminate the origin source of hyperfine noise. In its Silicon counterparts, reduction of 29Si abundance enables exceptional high-fidelity operation. In contrast, hole
qubits based on isotopically purified Ge have not been demonstrated. Here, we report the synthesis of high quality 2-dimensional hole gas (2DHG) with enriched 70GeH4 precursor. Due to the suppression of nonzero
spin nucleus, the
qubits' T2* on the sweet spot is moderately extended beyond 20 us, surpassing the previous best reported Ge hole
qubits. More importantly, the
qubits' T2* off the sweet spot is enhanced to above 3 us, enabling single
qubit gate fidelity exceeding 99.9% in both operating regimes. Hahn-echo spectroscopy further resolves a finite-frequency
nuclear-noise channel that is distinct from the conventional Larmor-linked hyperfine response. We associate this channel with quadrupole-modified dynamics of residual 73Ge
nuclei sampling local electric-field gradients near the Ge/SiGe interface. Its field scaling and angle-dependent visibility are consistent with a
qubit-visible quadrupolar
nuclear-noise component transduced through the anisotropic hyperfine interaction of Ge holes. These results establish isotopically purified planar Ge as a high-coherence scalable platform for hole
spin qubits and provide a spectroscopic probe of interfacial quadrupolar
nuclear dynamics.
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All authors Jian Zeng, Xiangjun Tan, Hongzhang Wang, Yulei Zhang, Wendong Bian, Lingting Wu, Chenggang Yang, Zhengshan Guo, Jiankun Li, Yongfeng Wang, Jun Lu, Jun-Wei Luo, Tian Pei