Lattice Field Theory
Smeared spectral functions from lattice QCD: opportunities and challenges
Shoji Hashimoto
A broad class of physical observables can be expressed in terms of smeared spectral functions. Important examples include the hadronic
vacuum polarization contribution to the
muon $g-2$, hadronic $\tau$ decays, inclusive semileptonic $B$ and $D$ decays, and amplitudes for rare processes such as $B\to K^{(*)}\ell^+\ell^-$. In recent years, a variety of methods have been proposed to reconstruct or constrain such spectral functions from Euclidean correlators and related inputs. However, the inverse problem is intrinsically ill-posed, making it difficult to obtain fully reliable, model-independent results with controlled uncertainties. In this contribution, I summarize recent developments, discuss the opportunities offered by smeared spectral observables, and highlight the main challenges that remain.
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Instrumentation and Methods for Astrophysics
Scientific performances of the XGIS instrument on-board THESEUS
E. Arrigoni, S. Mereghetti, R. Campana et al. (+6 more)
The Transient High Energy Sky and Early Universe Surveyor (THESEUS) satellite, currently undergoing a Phase-A study for the M7 ESA mission selection, will mainly rely on the XGIS (X and Gamma Imaging Spectrometer) instrument to discover and precisely localise gamma-ray bursts and other high-energy transients. The XGIS instrument has been designed to provide accurate sky images in a wide field of view (>2 steradians) in the 2-150 keV band, coupled to coverage of nearly half of the sky with good timing and spectroscopic capabilities up to several MeV. This will be achieved thanks to the combination of two identical cameras, based on the coded mask imaging technique, oriented to provide partially overlapping fields of view. We present the capabilities of the XGIS, focussing in particular on the sensitivity and source location accuracy. We discuss the expected scientific advances in the GRB field, estimated through detailed Monte-Carlo simulations which take into account the design of the XGIS imaging system and the properties of the GRB population at high
redshifts.
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All authors E. Arrigoni, S. Mereghetti, R. Campana, C. Labanti, A. Pisapia, P. Calabretto, G. Mattioli, E. Virgilli, L. Amati
Astrophysics of Galaxies
Is the Nuclear Star Cluster a Bulge Fossil Fragment?
R. Michael Rich, Brian Thorsbro and Christian Johnson
The Milky Way
nuclear star cluster (NSC) is unlike a conventional globular cluster: it contains a broad
metallicity distribution and
stellar populations formed over an extended interval, while its detailed abundances show a close connection to the inner
Galactic bulge. We ask whether the NSC should instead be compared with the proposed "bulge fossil fragments" Terzan 5 and Liller 1, complex
stellar systems interpreted as surviving remnants of massive structures involved in early bulge assembly. We place this comparison against the field-bulge
metallicity distribution measured by the Blanco DECam Bulge Survey and against high-resolution infrared abundance measurements in the NSC. A broad
metallicity distribution by itself is not diagnostic, because the bulge field is intrinsically broad and strongly structured. More discriminating tests are the presence of chemically narrow and age-coherent subpopulations, the relation between [alpha/Fe] and [Fe/H], light-element abundance patterns, spatial segregation, and chemo-dynamical differences among populations. Existing NSC data establish strong chemical links with the bulge but do not support a simple one-to-one analogue of either Terzan 5 or Liller 1. In particular, metal-rich alpha-enhanced
stars in the NSC provide an important contrast with the near-
solar [alpha/Fe] metal-rich populations of the best-studied fossil-fragment candidates. We argue that the BFF hypothesis is most useful as a falsifiable framework for identifying an early bulge-building component within a composite NSC assembled through in-situ
star formation, migration, and cluster infall.
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Quantum Physics
A proposal for a hybrid free-space optical quantum communication network with hexagonal boron nitride-based single photon sources
Julien Chénedé, Mostafa Abasifard, Tjorben Matthes et al. (+2 more)
Hexagonal boron nitride (hBN) is known as a promising solid-state platform to host room temperature
quantum emitters that produce high purity single
photons. The bright and spectrally adaptable hBN emitters are space-compatible, making hBN well-suited for satellite-based free-space optical (FSO)
quantum key distribution (QKD) at wavelengths where the atmospheric background is naturally suppressed. This paper presents a pathway to develop hBN emitters operating near the Ca-II Fraunhofer line (at 854 nm), enabling daylight FSO operation. Moreover, due to its compatibility with the first telecommunication window at 850 nm, it is possible to interface with optical fibers to bridge the `last mile' in a scenario where multiple end-users connect through a single optical ground station to a QKD satellite. We therefore introduce a concept that combines continuous operation of a
quantum network, hybrid links to minimize deployment costs, and high data rates due to the use of realistic single
photon sources. The realization would be an important milestone for the development of the
quantum internet.
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All authors Julien Chénedé, Mostafa Abasifard, Tjorben Matthes, Asl{\i} Çakan, Tobias Vogl
High Energy Physics (Theory)
Unfolded Krylov complexity: universal chaotic dynamics without false positives
Johanna Erdmenger, Kyoung-Bum Huh, Hyun-Sik Jeong et al. (+1 more)
A central challenge in diagnosing
quantum chaos is to distinguish genuine many-body scrambling from kinematic effects of the spectrum. Krylov state complexity, or spread complexity, has emerged as a powerful diagnostic, with its characteristic growth, peak, and relaxation often taken as signatures of chaos. However, previous work has shown that this criterion can give false positives: saddle-dominated integrable systems may display prominent peaks even without random-
matrix level correlations. We argue, based on complementary numerical and analytical evidence, that this ambiguity can be resolved by unfolding the spectrum prior to constructing the ensuing Krylov dynamics. By removing the non-universal smooth density of states while retaining microscopic spectral correlations, unfolding suppresses spurious peaks in integrable systems while preserving the universal spectral signatures of chaotic systems. Analytically, the formulation of the Lanczos iteration in terms of orthogonal
polynomials yields an exact complexity kernel with a robust near-diagonal structure whose fine-grained features reflect the underlying spectral correlations. Moreover, for the logarithmic model, unfolding can be performed exactly, mapping the spectrum to a uniform
lattice and yielding an analytic spread complexity that removes the false-positive peak. These findings establish unfolded Krylov complexity as a more reliable probe of genuine many-body scrambling.
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All authors Johanna Erdmenger, Kyoung-Bum Huh, Hyun-Sik Jeong, Juan F. Pedraza
Quantum Physics
Coherent microwave-to-optical transduction with Yb:YSO spins strongly coupled to a 3D resonator
Ujjwal Gautam, Nasser Gohari Kamel, Sourabh Kumar et al. (+1 more)
Microwave-to-optical
quantum transducers are essential for entangling remote superconducting
qubits. Among the available transduction platforms, ensembles of Er$^{3+}$ and Yb$^{3+}$ ions doped into solids have emerged as leading candidates. While external
magnetic fields are needed to split the Zeeman levels of erbium ions and enable a microwave–
qubit interface, superconducting
qubits suffer decoherence in such fields. In contrast, ytterbium ions exhibit zero-first-order Zeeman transitions and large hyperfine splittings at zero
magnetic field (when doped into inorganic
crystals). Owing to its long optical and
spin coherence times, Yb:YSO has been widely used as a
quantum memory, yet its potential for
quantum transduction remains largely unexplored. Investigating this material could enable the integration of
quantum memory and transduction in a single platform. Here, we demonstrate microwave-to-optical transduction in the continuous-wave regime using a 5\,ppm doped Yb:YSO
crystal. The internal transduction efficiency is $2\times10^{-8}$ with a bandwidth of 200\,kHz, achieved using a 3D loop-gap microwave resonator (LGR) and a single-pass optical configuration. We explore all the ground states that form a V-type three-level system with the first and second optical excited states and assert the use of the ground state, which provides the highest efficiency and isolated optical transition. We further establish strong
spin-microwave coupling from avoided crossing measurements. With a strong microwave drive to saturate the
spin transition, we estimate the
spin population pumped into the excited state, close to the simulated value. Finally, we calculate target parameter values for maximum efficiency with our system and suggest using 50\,ppm doped Yb:YSO
crystal. With the calculated target parameters, the internal transduction efficiency is predicted to reach up to $10^{-4}$ in the current LGR.
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All authors Ujjwal Gautam, Nasser Gohari Kamel, Sourabh Kumar, Daniel Oblak
General Relativity and Quantum Cosmology
Accretion dynamics of thin and thick disks in charged Kalb-Ramond black holes
Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo et al. (+5 more)
In this work, we investigate the
accretion properties of an electrically charged, static, spherically symmetric black hole in Kalb-Ramond (KR)
gravity, where a dimensionless parameter $l$ characterizes spontaneous Lorentz
symmetry-breaking. We first constrain the free charge and KR parameter space, $(Q,l)$, by comparing the predicted shadow radius of this family of solutions with the bounds inferred from Event Horizon
Telescope observations of Sagittarius A*. The inclusion of electric charge introduces a degeneracy between $Q$ and $l$, enlarging the region compatible with the observed shadow size and yielding the broad constraint $-0.3900 \leq l \leq 0.1898$, with part of the compatible parameter space extending into the naked-singularity sector. We then investigate relativistic
accretion disks around the charged KR black hole within the above constraints. For geometrically thin disks, we compute the time averaged energy flux, temperature distribution, emission spectrum, time averaged torque, and mass-to-radiation conversion efficiency, finding that the radiative output increases for higher values of $l$, while lower values of $l$ suppress it. Furthermore, when coupled with the electric charge this effect is amplified. For geometrically thick, constant-angular momentum
tori-shaped disks, Lorentz
symmetry-breaking shifts the characteristic orbital radii, compresses the radial extent of
equilibrium configurations, narrows the interval supporting finite
equilibrium tori, and shifts the stationary-fluid
topology toward open and unconfined configurations outside that interval. These results show how charge and spontaneous Lorentz
symmetry-breaking jointly affect observational constraints and the structure and emission properties of black hole
accretion flows, providing potential signatures of KR
gravity in the strong-
gravity regime.
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All authors Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo, Jorde A. A. Ramos, Manuel E. Rodrigues, Diego Rubiera-Garcia, Luís F. Dias da Silva, Henrique A. Vieira
Instrumentation and Methods for Astrophysics
Demonstrating the Time-Domain Capabilities of the 4-m International Liquid Mirror Telescope: An Early Census of Transient and Variable Detections
Kumar Pranshu, Kuntal Misra, Bhavya Ailawadhi et al. (+11 more)
The PyLMT transient detection pipeline has been operational since November 2023, detecting transient and variable objects in the ILMT images in almost real time. Using the image subtraction technique, nearly 3700 CCD frames have been analyzed by the automated pipeline, generating nearly 23,000 alerts for the detection of verified transient candidates and cataloged variable sources. Around 21,000 of the alerts correspond to known MPC asteroids, nearly 2000 correspond to variable
stars (including eclipsing binaries, RR Lyrae, Delta Scuti, T-Tauri, etc.), 509 correspond to variable AGNs (including QSOs, Seyfert
galaxies, and blazars), 21
supernova candidates, and several other interesting candidates. We provide a concise overview of the detections and their significance, emphasizing the surveys potential contributions to a broad class of astrophysical and scientific cases. A transient detection dashboard called DART was developed using Streamlit to visualize and categorize candidates based on PyLMT and SIMBAD classifications. It includes cone-search functionality and displays key metadata, offering an intuitive interface that is publicly accessible. Our results demonstrate the viability of
liquid mirror
telescopes such as the ILMT for time-domain astronomy, emphasizing the important role that small-field survey facilities can play in systematic transient science programs.
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All authors Kumar Pranshu, Kuntal Misra, Bhavya Ailawadhi, Monalisa Dubey, Naveen Dukiya, Sara Filali, Paul Hickson, Priyanshi Kumari, Gokul Singh Mehra, Vibhore Negi, Jeewan C. Pandey, Anna Pospieszalska-Surdej, Jean Surdej, Sarvesh Kumar Yadav
Solar and Stellar Astrophysics
The relationship between solar and stellar tachoclines, dynamos, and spin-down
Loren I. Matilsky, Lydia Korre and Nicholas Brummell
The
solar tachocline, a thin shear layer separating the differentially rotating convective zone (CZ) from the underlying rigidly rotating radiative zone (RZ), remains a dynamical mystery. Under the influence of "radiative spreading" (the process by which meridional circulation, baroclinicity, and differential rotation burrow through a stably stratified fluid), the tachocline should have spread significantly by the current age of the Sun. Some unknown torque must therefore rigidify the whole
solar interior below the CZ and keep the tachocline confined to a thin layer. At the same time, the
spin-down process (through which cool
stars shed angular momentum via surface
magnetic torques) must extract angular momentum from the
solar RZ, presenting a second mystery:
solar spin-down must be communicated from the near-surface layers to the deep interior, all the while leaving the tachocline intact. In this work, we explicitly analyze the dynamics of radiative spreading in two 3D, spherical-shell, fully nonlinear fluid simulations of a
solar-like CZ–RZ system, one without a
magnetic field (hydrodynamic—HD) and one with a small random seed
magnetic field (magnetohydrodynamic—MHD). We find that radiative spreading is unmitigated in the HD case (as expected), but in the MHD case, a self-excited dynamo not only confines the tachocline, but also extracts angular momentum from the RZ, thereby communicating the
spin-down downward. We thus speculate that
solar and
stellar tachoclines may be intimately linked to both the
spin-down process and global dynamo.
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Chemical Physics
Prototype-guided transfer of sparse literature knowledge for electrolyte additive discovery
Weixiang Hong, Hongting Du, Jiayue Tang et al. (+4 more)
Electrolyte additive discovery remains challenging because experimentally validated molecules are sparse, whereas accessible chemical spaces are vast and largely unlabeled. This challenge is amplified in lithium-ion batteries, where additive performance arises from coupled interfacial reactions rather than a single molecular property. Here, we develop a prototype-guided molecular intelligence, ProtoMI, a literature-driven framework that learns transferable structural priors from reported electrolyte additives and uses them to prioritize candidates in unlabeled chemical space. For boron-containing additives, ProtoMI combines 126 literature-reported molecules with 179,977 unlabeled candidates. Graph contrastive learning identifies seven chemically interpretable prototypes from the reported additives, and prototype guided semi-supervised contrastive learning adapts these prototypes to the candidate space under source-target distribution mismatch. In retrospective temporal validation, ProtoMI achieves enrichment factors of 9.2-45.6 while screening less than 2% of the candidate space. A subsequent translation step identifies four commercially accessible candidates. One representative candidate, 4,4,5,5-Tetramethyl-2-[10-(1naphthyl)anthracen-9-yl]-1,3,2-dioxaborolane (TNDB), improves high-temperature LiFePO4||graphite cycling at 55 {\deg}C by 34.93% relative to the baseline electrolyte. An arsenal of characterizations and operando optical fiber
Fourier transform infrared spectroscopy suggest that TNDB forms B-containing, F/P/O-modified inorganic interphases, suppresses solvent decomposition and reduces Fe deposition on graphite. This case study shows how sparse literature knowledge can guide experimentally efficient molecular discovery in data-scarce battery-additive spaces.
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All authors Weixiang Hong, Hongting Du, Jiayue Tang, Ruifeng Tan, Yangjian Quan, Jia Li, Jiaqiang Huang
Materials Science
Decoding Oxygen K-edge Fingerprints of NCM-811 Degradation via Ab Initio Many-Body Theory and High-Throughput Screening of Crystal Proxies
Daniel Duarte-Ruiz, Timo Reents, Elmar Kataev et al. (+4 more)
The degradation of LiNi$_{0.8}$Co$_{0.1}$Mn$_{0.1}$O$_2$ (NCM-811) in Li-ion batteries produces complex transition-metal
oxides and binary phases that fundamentally limit cathode performance. While identifying these degradation products via X-ray absorption spectroscopy (XAS) is essential for mitigating electrochemical performance loss, interpretation remains challenging due to the structural complexity of real-world samples. In this work, we present an integrated theoretical-experimental framework combining high-resolution oxygen K-edge XAS with ab initio simulations based on many-body perturbation theory and high-throughput screening from density functional theory. We first evaluate the spectroscopic fingerprints of eight layered, spinel, and nominal rock-salt reference
oxides, identifying discrepancies between the idealized single-
crystal bulk phase and experimental spectra. Using high-throughput screening to analyze the oxygen $p$-projected density of states of 38 distinct polymorphs of NiO, CoO, and MnO, we propose that the spectral differences can emerge, among other factors, from local structural variations represented here by simplified structural proxies. Our work establishes a viable and rigorous computational pathway to interpret the complex landscape of degraded battery materials.
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All authors Daniel Duarte-Ruiz, Timo Reents, Elmar Kataev, Raul Garcia-Diez, Regan G. Wilks, Marcus Baer, Caterina Cocchi
Mathematical Physics · Cross-listed from math.QA
The tensor category for W(2,2)-vertex algebra
Drazen Adamovic, Mingjie Peng, Gordan Radobolja et al. (+1 more)
This paper studies the category $\mathcal{C}$ of grading-restricted $C_1$-cofinite generalized modules for the vertex operator
algebra associated to the $W$-
algebra $W(2,2)$. We first show that $\mathcal{C}$ is the same as the category of finite length modules whose simple composition factors are the irreducible highest weight $W(2,2)$–modules $L[r]$ of highest weight $(\frac{1-r}{2}, 0)$ for $r \in \mathbb{Z}_{> 0}$, and hence $\mathcal{C}$ carries a braided tensor category structure. Then we prove the fusion rules for the simple objects $L[r]$ are governed by the $\mathfrak{sl}_2$ Clebsch–Gordan rule. In particular, we prove \[ L[r]\boxtimes L[s]\cong \bigoplus_{i=0}^{\min\{r,s\}-1} L[r+s-1-2i]. \] Using the fusion rules and a recent result of Etingof–Penneys, we establish the
rigidity of $\mathcal{C}$. We also show the semisimple subcategory generated by the simple objects $L[r]$ is tensor equivalent to the category Rep $\mathfrak{sl}_2$ of finite dimensional $\mathfrak{sl}_2$-modules.
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All authors Drazen Adamovic, Mingjie Peng, Gordan Radobolja, Jinwei Yang
Biological Physics
Trypanosome motility in blood and particle suspensions
Florian A. Overberg, Marie Kater, Timothy Krüger et al. (+3 more)
Motile microorganisms often navigate crowded and structurally complex environments, where surrounding obstacles can strongly influence locomotion. The bloodstream form of the flagellate parasite Trypanosoma brucei circulates in blood, a dense suspension of red blood
cells (RBCs), yet the physical mechanisms governing its locomotion under such conditions remain poorly understood because direct experimental observations are challenging. Here, we combine numerical simulations with in vitro experiments to investigate trypanosome motility in concentrated RBC suspensions and in suspensions of spherical colloidal particles. Simulations reveal that the parasite swimming speed increases by up to $50\%$ at RBC volume fractions comparable to those in blood. To identify the origin of this enhancement, we perform controlled studies in colloidal suspensions with particles of different sizes. We find that suspended particles substantially increase the anisotropy between the perpendicular and parallel friction coefficients acting on the beating flagellum, thereby enhancing propulsion. This effect is most pronounced when the suspended particles are comparable to or smaller than the characteristic wavelength of the flagellar beat. Experiments with microparticle suspensions confirm an increase in trypanosome propulsion with increasing particle concentration, in qualitative agreement with the simulations. Our results uncover a general physical mechanism by which concentrated particle suspensions can enhance flagellar-beat-driven locomotion and suggest that the densely crowded, particulate environment of blood may facilitate trypanosome propulsion. These findings provide new insight into trypanosome motility in the bloodstream and may apply broadly to other flagellated microswimmers in complex suspensions.
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All authors Florian A. Overberg, Marie Kater, Timothy Krüger, Gerhard Gompper, Markus Engstler, Dmitry A. Fedosov
Quantum Physics
Observation of Hong-Ou-Mandel interference between photon and polariton
Yun-Ru Fan, Ying-Ao Su, Kai Guo et al. (+11 more)
Light-matter interactions underlie many
quantum technologies, yet whether quasiparticles formed from such interactions preserve the full
quantum state of light remains unresolved. Surface plasmon polaritons (SPPs), a class of polaritons formed by interacting
photons with free-electron oscillations at metal-dielectric interfaces, are
prime candidates to explore this question. Here we demonstrate
quantum interference between single
photons and SPPs using an Au-SiN$_{\mathrm{x}}$ integrated photonic-plasmonic device. Our results reveal that SPPs retain the indistinguishability of their excitation
photons, establishing SPP as a viable
quantum information carrier and opening a potential route toward photonic-plasmonic
quantum circuitry.
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All authors Yun-Ru Fan, Ying-Ao Su, Kai Guo, Bo-Yu Fan, Yao-Qing Zhang, Hai-Zhi Song, Hao Li, Yong Geng, Kun Chen, Deng-Ke Zhang, Li-Xing You, Yan-Yu Wei, Guang-Can Guo, Qiang Zhou
Materials Science
The Locality Cost of Fully Flat Hopf Insulators
Feng Liu, Qifeng Liang and Wenlong Gao
Hopf topology permits a strictly finite-range
Hamiltonian with one exactly flat topological band. We prove, however, that extending flatness to the complete two-band spectrum necessarily sacrifices strict locality or the gap: any gapped, Hermitian, translationally invariant two-band
Hamiltonian with strictly finite-range hopping and two exactly flat bands has vanishing
Hopf invariant. Equivalently, within this two-band setting, a
Hopf band admits no compactly supported, translation-covariant, orthonormal Wannier generator. For factorized one-flat-band
Hopf parents, the unavoidable partner dispersion equals the Gram symbol of translated compact localized states and encodes their nonorthogonality. Full flattening converts this dispersion into exponentially decaying but infinitely supported hopping. Model-independent bounds provide a sufficient criterion for finite-range approximants to retain the
Hopf phase. An explicit model yields the axial decay length $\xi_z/a=1/\ln 2$, parameter-free hopping tails, and residual bandwidths testable in
circuit and photonic
lattices.
Hopf topology therefore does not prohibit a flat band but forces the locality–flatness cost to appear as either partner-band dispersion or nonlocal hopping.
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Mathematical Physics · Cross-listed from math.PR
Paracontrolled approach to the stochastic Cahn-Hilliard equation
Joe Ghafari
We prove the existence and uniqueness of a local-in-time solution to the
stochastic Cahn-Hilliard equation in space dimensions 1, 2, 3, 4 and 5. Our method relies on the Da Prato-Debussche trick for $d=4$ and paracontrolled distributions for $d=5.$
Disordered Systems and Neural Networks · Cross-listed from cs.NE
Memory as an Energy Landscape—Hopfield
Nima Dehghani
This chapter reconstructs the Hopfield network as a physical theory of
memory rather than merely an early neural-network
algorithm. It begins with the problem as it stood before 1982-threshold logic, Hebbian association, correlation
memories, and recurrent binary networks-and isolates what Hopfield's synthesis added: a dynamical definition of content-addressable
memory, a symmetric recurrent architecture with a Lyapunov function, a Hebbian
embedding of patterns in its couplings, and a physical account of basins, robustness, and graceful degradation. The binary and graded-response energy functions are derived in full, together with the signal-crosstalk decomposition governing pattern stability, the mean-field theory of
retrieval at extensive load, and the zero-temperature
retrieval spinodal at (alpha 0.138) established by Amit, Gutfreund, and Sompolinsky. The energy-based program is then followed through analog optimization networks,
polynomial dense associative
memories, exponential interactions, and modern continuous Hopfield updates, including the precise conditions under which the update becomes scaled dot-product
attention. Throughout, capacity claims are tied to their disorder ensemble, scaling limit, and success criterion, showing why numerically different storage limits need not conflict. A closing assessment distinguishes established results from surviving principles, assumption-bound limitations, and open problems, treating the Hopfield network as an effective theory whose
symmetry, locality, and point-
neuron assumptions delimit its biological reach. Fixed-seed numerical experiments expose the mechanisms discussed but do not substitute for analytical results.
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Earth and Planetary Astrophysics
Double Gravity-Assist Rendezvous Trajectory to Halley's Comet Using Deep-Space Low Thrust
Roberto Flores, Alessandro Beolchi, Chiara Pozzi et al. (+4 more)
The perihelion of comet 1P/Halley in 2061 is an excellent chance to revisit this object of outstanding scientific and cultural relevance. During its 1986 approach to the Sun, it was targeted by several flyby missions. Due to its retrograde, highly-inclined orbit, the relative velocities during the encounter were large, limiting the scientific return due to the short time spent inside the coma. A rendezvous trajectory would overcome this limitation, but the design is challenging due to the limitations of current propulsion technology. Given the lead times of spacecraft development and the long duration of the interplanetary transfer to the comet, it is imperative to start mission planning as soon as possible. We present a novel rendezvous strategy, combining unpowered Jupiter and Saturn
gravity-assists with deep-space low-thrust arcs. It minimizes launch energy and propellant budget, constraining the arrival to occur before the onset of high activity. The double flyby strategy reduces the otherwise prohibitive cost of the plane change maneuver. Closed expressions for the optimal flyby geometry, together with an explicit low-thrust transcription technique, reduce the number of design parameter to three, improving computational efficiency. Crucially, this is the first rendezvous mission concept achievable with well-proven technology (standard radioisotope thermoelectric generators and a
Hall-effect thruster) and compatible with several existing launchers. We describe the trajectory optimization strategy and perform a comprehensive exploration of the design space. Finally, we present two promising proof-of-concept trajectories in detail.
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All authors Roberto Flores, Alessandro Beolchi, Chiara Pozzi, Mauro Pontani, Ivano Bertini, Cesare Barbieri, Elena Fantino
Quantum Physics
Quantum MeanFlow: single-shot generative sampling on NISQ hardware
Ashish Joshi, Eshaan Mistry and Takahiko Koyama
Quantum generative models offer a promising framework for exploring whether
quantum computation can enhance generative machine learning. Flow matching is a generative method in which samples are generated by transporting a simple, known distribution to the target data distribution with a learned velocity field. Its
quantum counterpart, known as
quantum flow matching (QFM), was introduced recently, and, like its classical counterpart, requires integrating an ordinary differential equation over many time steps during inference. As each step requires the output from the previous step, the
circuit submission is sequential and a drawback on
quantum computers as they have high input/output costs. To alleviate this problem, we introduce
Quantum MeanFlow (QMF), the
quantum analogue of the MeanFlow formulation, which allows single-step sample generation. While the QFM learns an instantaneous velocity field at each time step, QMF learns the average velocity over a time interval. We use a parameterized
quantum circuit to learn these velocity fields and
benchmark the two methods on the MNIST
dataset. We show that while single-step QMF has lower image quality compared to multi-step QFM, it performs better than the single-step QFM sampling at every shot count. Both of our models are executed on IBM
quantum computers and best-of-N rejection sampling recovers most of the accuracy lost to device noise without modifying the
circuit. This is especially advantageous for QMF which has only one
circuit evaluation per image. Here, We establish QMF as a viable method for single-step
quantum generative sampling, saving on
quantum circuit evaluations per generated sample.
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Astrophysics of Galaxies
Disc-Based Estimation of the Local Dark Matter Density and Velocity Distribution in IllustrisTNG50
Hatsume Chujo, Shogo Masaki, Keiko I. Nagao et al. (+1 more)
We study the dark matter (DM) density and velocity distribution in the
solar neighborhood of Milky Way-like
galaxies using the TNG50-1 run of the IllustrisTNG simulation suite. Milky Way-like
galaxies are selected according to both their
halo mass and their bulge-to-total
stellar mass ratio, and the
solar-neighborhood region within each
galaxy is identified from the positions and number density of
stars, so that DM particles associated with the
galactic disc are extracted while contributions from the
halo component are suppressed. Averaging over the selected
galaxies, we obtain a local DM density of $\rho \simeq 0.47\pm0.02~{\rm GeV\,cm^{-3}}$, consistent with the range inferred from observations. The disc-based extraction gives a higher peak density, $0.41\pm0.02~{\rm GeV\,cm^{-3}}$, than the value $0.34\pm0.02~{\rm GeV\,cm^{-3}}$ from a simple distance-based extraction, probably because it excludes the low-density DM in the
halo. The width of the density distribution, on the other hand, is nearly unchanged. The velocity distribution is well described by an isotropic Maxwellian with a peak velocity of about $226~{\rm km~s^{-1}}$, close to the value assumed in the standard
halo model. The differences in the density and velocity distributions between our disc-based and simple distance-based extractions are not so large as to significantly affect the interpretation of direct-detection experiments.
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All authors Hatsume Chujo, Shogo Masaki, Keiko I. Nagao, Takuho Nakabayashi
Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
Neural Logic, Invariance, and the Retina—McCulloch and Pitts
Nima Dehghani
This chapter reconstructs the McCulloch-Pitts program as a physics of neural computation rather than the familiar cartoon of a binary
neuron. The 1943 logical calculus is developed in both directions: given a net, characterize the propositions realized by its activity; given an admissible logical expression, construct a net that realizes it. We recover the original distinction between thresholded excitatory summation and absolute inhibitory veto-one the weighted-threshold form cannot preserve for arbitrarily large excitatory inputs-and read unit-time delay as the physical realization of logical depth. Recurrence is treated exactly: an autonomous, deterministic network of finitely many binary units has a finite state space, so every trajectory eventually enters a periodic orbit-a fact about finite-state dynamics, not unbounded Turing computation. A single threshold element realizes only linearly separable Boolean functions, whereas finite feedforward networks of them synthesize any Boolean function on a finite domain. We then follows McCulloch and Pitts beyond threshold logic. The 1945 heterarchy paper turns cyclic preference into an obstruction to representation by a scalar utility. The 1947 work on universals asks how a physical network can identify inputs related by nuisance transformations, developed here via group averaging and feedback canonicalization. The 1959 frog-retina study makes the adequate-stimulus question experimental, revealing parallel invariant operations before the
brain proper. Spike-triggered analysis shows how a nonlinearly driven
neuron can have a vanishing first-order average while second-order statistics recover its hidden selectivity: methodological failure can masquerade as physiological absence. Modern mathematical tools are used without projecting their notation onto the historical papers, and limitations of the idealization are stated explicitly.
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Plasma Physics
A Hybrid Simulation Code for Hall Thrusters and its Sensitivity to Numerical Parameters
Xingdong Che, Hong Li, Xin Guo et al. (+3 more)
Hybrid methods offer an attractive balance between computational efficiency and physical accuracy, playing an important guiding role in the design and optimization of
Hall thrusters. In this work, a hybrid simulation code, named HYSCH, is developed, utilizing a 1D-MFAM as the mesh framework for the electron submodel. HYSCH enables decoupling of the two submodel meshes, providing a higher degree of flexibility in spatial resolution settings. The sensitivity of the simulated results to numerical parameters is analyzed to validate the model's numerical robustness and physical consistency. The analysis shows that the temporal resolution of the heavy-species submodel and the spatial resolution of the electron submodel exert a more pronounced influence in the agreement with measurements than the heavy-species macroparticle weight and spatial resolution, confirming that the decoupled formulation enables more efficient resource allocation than coupled discretizations.
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All authors Xingdong Che, Hong Li, Xin Guo, Zhaoyu Wang, Xifeng Cao, Daren Yu
Astrophysics of Galaxies
Constraints on the Intranight Optical Variability of Intermediate-Mass Black Hole Candidates
Wenwen Zuo, Hengxiao Guo, Wanling Liu et al. (+12 more)
Intermediate-mass black holes (IMBHs) provide a unique regime for studying
accretion variability at the low-mass end of the black hole population, yet their intranight optical variability (INOV) remains poorly constrained. We present a systematic investigation of INOV in an optically selected sample of IMBH candidates using high-cadence observations from the Zwicky Transient Facility (ZTF). From a parent sample of 1,447 broad H$\alpha$-selected candidates, we identify 64 IMBH candidates (median $f_{\mathrm{AGN}}\sim0.06$) with 163 intranight monitoring sessions. Apparent INOV signals identified by conventional ZTF PSF-fit photometry are largely associated with seeing-dependent changes in the relative contributions of compact
nuclear and extended host components, which can mimic intrinsic short-timescale variability. In contrast, no robust INOV is detected with difference-image analysis. An ensemble structure function spanning $\Delta t\sim0.003$–$1600$ days reveals long-term variability in a small subsample of sources, whereas intrinsic variability remains unresolved at intranight timescales. Monte Carlo simulations further show that ZTF-like single-night monitoring has a low INOV recovery probability ($\sim1.2%$) for the variability amplitudes inferred from the long-term analysis. The recovery probability is primarily controlled by source brightness, AGN contribution, intrinsic variability amplitude, and photometric precision. These results demonstrate that the absence of detected INOV does not imply the absence of rapid
accretion variability, but can reflect the limited detectability of low-amplitude signals under current observing capabilities. Our findings highlight the importance of robust photometric methodologies for future high-cadence variability studies of low-mass accreting black holes.
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All authors Wenwen Zuo, Hengxiao Guo, Wanling Liu, Wenke Ren, Jingbo Sun, Patricia Arévalo, Luis C. Ho, Alok C. Gupta, Vineet Ojha, Mouyuan Sun, Shuangliang Li, Haicheng Feng, Qi Yuan, Minfeng Gu, Xuebing Wu
Astrophysics of Galaxies
The Intermediate-Mass Black Hole Reverberation Mapping Project: Scientific Overview and Sample Characteristics
Hengxiao Guo, Jiancheng Wu, Wenwen Zuo et al. (+38 more)
Recent discoveries with the James Webb Space
Telescope of massive black holes at high
redshift have highlighted fundamental questions about black hole seed formation and the coevolution of black holes with their host
galaxies. Because the initial seed population cannot yet be observed directly, nearby intermediate-mass black holes provide a complementary fossil record of black hole formation and early growth. Motivated by this opportunity, we present the Intermediate-Mass Black Hole Reverberation Mapping (IMBH-RM) project and construct a homogeneous Sloan Digital Sky Survey sample of active broad-line IMBHs by uniformly reanalyzing literature candidates with consistent spectral decomposition and black hole mass estimation. Our sample contains 192 reliable IMBH candidates at $z\lesssim0.3$ with $\log(M_{\rm BH}/M_\odot)<6$, including four particularly compelling sources with $\log(M_{\rm BH}/M_\odot)<5$. The primary goal of IMBH-RM is to obtain reliable black hole masses from direct measurements and characteristic sizes of the broad-line region and
accretion disk for a carefully selected subsample. These measurements will provide robust low-mass anchors for calibrating single-epoch black hole mass estimates and extending black hole–
galaxy scaling relations into the IMBH regime. By building a statistically meaningful reverberation-mapped sample spanning $10^4-10^6\,M_\odot$, we aim to constrain the local IMBH mass distribution and place observational constraints on competing black hole seed formation scenarios. The future Multi-Channel Imager aboard the Chinese Space-station Survey
Telescope provides a particularly promising platform for achieving these goals.
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All authors Hengxiao Guo, Jiancheng Wu, Wenwen Zuo, Ruining Tian, Xuechen Zheng, Meicun Hou, Paulina Lira, Philip G. Edwards, Vivian U, Shu Wang, Mar Mezcua, Luis C. Ho, Minfeng Gu, Tao An, Samuzal Barua, Colin J. Burke, Zhen-yi Cai, Xuheng Ding, Haicheng Feng, Alok C. Gupta, ShaSha Li, Wanling Liu, Wen-juan Liu, Ru-sen Lu, Dragana Ilić, Andjelka B. Kovačević, Yu Pan, Luka Č. Popović, Wenke Ren, Paula Sánchez-Sáez, Jamie Stevens, Jingbo Sun, Mouyuan Sun, Chizhuo Wang, Junxian Wang, Rongfeng Shen, Xuebing Wu, Yong Shi, Zhefu Yu, Zhenya Zheng, Ling Zhu
Mathematical Physics · Cross-listed from math.AP
Inverse Semiclassical Scattering at Fixed Energy
François Nicoleau
We investigate inverse scattering at a fixed energy for semiclassical Schrödinger operators with smooth potentials. For compactly supported potentials satisfying a natural virial condition, we prove that, under the sharp condition, $\liminf_{h\to0}\|S_1(\lambda,h)-S_2(\lambda,h)\|<2$ implies $V_1=V_2$, provided the fixed energy $\lambda$ lies above both potentials. We then consider radial short-range repulsive potentials. Under a monotonicity assumption on the radial force, we show that the semiclassical differential cross section at a fixed energy, up to $o(1)$ as $h\to0$, determines the potential in the classically accessible region. Finally, we obtain an analogous
rigidity result for nontrapping compactly supported perturbations of the Euclidean metric under a strict convexity assumption.
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Astrophysics of Galaxies
Empirical Near-Infrared Spectral Templates from SPHEREx: Disentangling AGN and Host-Galaxy Emission
Wenke Ren, Hengxiao Guo, Zhenya Zheng et al. (+9 more)
SPHEREx conducts the first all-sky near-infrared spectral survey over 0.75-5.0 $\mu$m, spanning the transition from host-
galaxy starlight to AGN-heated
torus emission and enabling spectroscopic identification of active
galactic nuclei (AGNs). We develop a data-driven framework combining weighted non-negative
matrix factorization with forward modeling to learn empirical rest-frame templates from 2,777 normal
galaxies and 1,064 AGNs in the North Ecliptic Pole (NEP) field. The resulting 14-component dictionary contains seven
galaxy templates spanning
stellar-population continua and nebular emission and seven AGN templates capturing emission lines and warm and hot
torus continua, providing an additive, operational decomposition. Inferred near-infrared host fractions correlate with independent SDSS spectral and HSC imaging decompositions (at Pearson $r=0.68$ and $r=0.59$), comparable to the SDSS-HSC correlation ($r=0.66$) and supporting the reliability of the AGN-host separation. In the NEP deep field, the same templates recover
redshifts with $|z_{\rm fit}-z_{\rm spec}| < 0.01$ for 93.0% of
galaxies and 93.5% of AGNs and distinguish
galaxies, narrow-line AGNs, and broad-line AGNs with 81.3% accuracy. At all-sky depth, classification retains 72.9% accuracy. The near-infrared coefficients also flag questionable DESI spectral classifications and
redshifts, showing how SPHEREx complements optical spectroscopy. Learned directly from survey spectrophotometry and extending beyond the $K$ band, this empirical dictionary fills a long-standing gap in near-to-mid-infrared templates and provides a data-driven foundation for population-scale studies of AGN activity and its connection to host
galaxies across the SPHEREx all-sky survey.
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All authors Wenke Ren, Hengxiao Guo, Zhenya Zheng, Minfeng Gu, Wenwen Zuo, Junxian Wang, Weida Hu, Zhen-Bo Su, Shi-Jiang Chen, Lin Long, Jiaqi Lin, Chi-Zhuo Wang
Instrumentation and Methods for Astrophysics
Simulation of the electron escape ratio for keV alpha-particle ionization tracks in liquid helium
Zihuai Hu, Junhui Liao, Zhuo Liang et al. (+6 more)
The electron escape ratio for 5.3 MeV alpha-particle ionization tracks in
liquid helium under varying external electric fields has been measured in several experiments. However, to the best of our knowledge, the corresponding ratio for keV-scale alpha tracks in the same medium has not yet been reported. In this article, we demonstrate for the first time that this ratio can be accurately characterized using COMSOL-based simulations. Our simulation framework was developed in two stages. In Stage I, we aimed to verify consistency between our simulated results and published experimental data for 5.3 MeV alpha particles. Following successful verification in Stage I, we proceeded to Stage II, in which the 5.3 MeV track was replaced by 2, 5, and 10 keV tracks. Our simulated results reveal that (a) keV-scale tracks exhibit electron escape ratios approximately 1.5-2.5 times higher than that of the 5.3 MeV track, and (b) the escape ratios for all track energies (2, 5, 10 keV, and 5.3 MeV) exhibit a linear dependence on the ion number density at the simulation's T0, but not on the electron number density.
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All authors Zihuai Hu, Junhui Liao, Zhuo Liang, Guangpeng An, Zhaohua Peng, Jian Zheng, Lifeng Zhang, Lei Zhang, Yuanning Gao
Optics
Multidimensional Light Detection with Symmetry-engineered Heterojunctions
Yucai Lin, Yaoqiang Zhou, Ruijuan Tian et al. (+11 more)
Miniaturised multidimensional light detection, encompassing full-Stokes polarimetry and spectroscopy in ultracompact footprints, is attracting growing interest for its potential to capture a comprehensive set of light properties in portable platforms. Although significant progress has been made in miniaturised schemes for independent polarisation and spectral detection, achieving simultaneous high-dimensional light detection remains an outstanding challenge that limits their development toward full integration. We overcome this limitation by breaking the rotational and inversion
symmetries in a
symmetry-engineered van der Waals heterojunction to realise an ultracompact multidimensional photodetector. The dual
symmetry breaking gives rise to non-trivial
quantum geometric and topological features, enabling simultaneous broadband polarisation- and spectrum-resolved light detection, in contrast to previous van der Waals material-based devices, which could detect only one of these modalities. Our device, with an effective area of only 10 micron x 10 micron, reconstructs full-Stokes polarisation with overall root-mean-square errors below 0.05 and resolves spectral peaks separated by 0.4 nm, capabilities not previously achieved in single-pixel detectors. By unifying high-fidelity polarimetry and sub-nanometre spectroscopy in a single electrically tunable junction, our work eliminates the need for cascaded detection architectures and establishes a foundation for multidimensional detector arrays for integrated photonics,
quantum information processing, and precision imaging.
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All authors Yucai Lin, Yaoqiang Zhou, Ruijuan Tian, Faisal Ahmed, Andreas C. Liapis, Youqiang Huang, Yawei Dai, Yuwei Chen, Weiwei Cai, Zongyin Yang, Weida Hu, Tawfique Hasan, Luojun Du, Zhipei Sun
Solar and Stellar Astrophysics
Electron acceleration by turbulent reconnection in solar flares
Zining Ren, Xin Cheng, Yulei Wang et al. (+1 more)
Solar flares can release
magnetic energy explosively in the corona and produce high-energy particles on short timescales. However, how and where these particles are accelerated remains an open question. Here, we investigate the acceleration and transport of electrons during self-developed three-dimensional turbulent reconnection of
solar flares by solving Parker's transport equation in the framework of high-resolution MHD simulations. We find that thermal electrons at both the
flare current sheet and loop top are rapidly accelerated up to ~90keV, with energy spectra exhibiting a power-law feature. Although the population of accelerated electrons at the
flare loop top is larger than that at the current sheet, their spectral indices are similar, close to the values usually observed. More importantly, the acceleration is achieved by
turbulence-driven compression structures of various scales rather than the supposed termination shock, particularly at the
flare loop top. A portion of compression structures even forms shocks. These results highlight the critical role of turbulent reconnection in accelerating electrons, thereby shedding new light on the acceleration and transport of particles in other high-energy phenomena.
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All authors Zining Ren, Xin Cheng, Yulei Wang, Mingde Ding
High Energy Physics (Phenomenology)
Macroscopic Coherent Axion Production by Reverse Parametric Fluorescence
Zhan Bai, Baifei Shen, Liangliang Ji et al. (+1 more)
We propose a macroscopically coherent laboratory source of
axion-like particles (ALPs) through the
axion–electron coupling \(g_{ae}\). Two counterpropagating optical modes drive reverse parametric fluorescence in a
crystal, where two pump
photons are converted into a relativistic ALP through virtual ionic transitions, while the medium returns to its initial state. Phase matching enables emission amplitudes from many ions to add coherently without preparing material coherence. The pump frequencies determine the ALP energy, making the source continuously tunable. The production rate scales with the product of the two pump powers and the square of the source length. Resonant absorption followed by fluorescence completes the detection scheme. For
benchmark crystal and
laser parameters, a one-year operation gives a reach of \(g_{ae}\simeq2.8\times10^{-11}\), substantially improving the sensitivity of purely laboratory-based searches for low-mass ALPs.
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All authors Zhan Bai, Baifei Shen, Liangliang Ji, Ruxin Li