Quantum Physics
Sharp continuity of quantum conditional entropy
Mario Berta, Pablo Costa Rico, Gereon Kossmann et al. (+2 more)
We prove the sharp uniform continuity bound for
quantum conditional
entropy. If two bipartite states are at trace distance at most $\delta$ and $d=\dim A$, the optimal dimension-only modulus of continuity is $h_2(\delta)+\delta\log(d^2-1)$ up to $\delta=1-d^{-2}$ and $2\log d$ thereafter, where $h_2$ denotes the binary
entropy. When $\dim B\ge d$, this bound is tight for every $\delta\in[0,1]$. The key proof idea was developed with the assistance of ChatGPT 5.6 Sol, building on and adapting the tight classical proof of Alhejji & Smith [IEEE ISIT (2020)], which follows a conceptually different approach.
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All authors Mario Berta, Pablo Costa Rico, Gereon Kossmann, Ludovico Lami, Julius A. Zeiss
Quantum Physics
Stacking the Deck: Tunable Trainability in Stacked LCUs
Nikhil Khatri, Stefan Zohren and Gabriel Matos
Variational
quantum circuits have been central to many proposed near-term applications of
quantum computing, but a growing body of evidence suggests that trainability and
quantum advantage are fundamentally at odds: ansätze expressive enough to resist efficient classical simulation tend to exhibit barren plateaus, while structures that provably rule out barren plateaus typically render them classically simulable. We propose a stacked linear combination of
unitaries (S-LCU) as a variational ansatz which provides a tunable trade-off between barren plateaus and classical simulability. Using a diagrammatic analysis, we bound the loss-landscape variance of the Free
Fermion S-LCU, whose elements are fermionic Gaussian
unitaries. We prove a variance lower bound of $\Omega(1/(n k^{3l}))$, with a simulation cost of $O(k^{2l} n^3)$ using the best known classical
algorithm, compared to a
quantum gate complexity of only $O(lkn^2)$. The number of layers $l$ serves as a single dial that trades computational complexity against the rate of cost concentration. This offers practitioners a systematic method for constructing ansätze with a complexity-trainability trade-off that best suits their application and hardware.
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Materials Science
Growth and characterization of planar hexagonal Ge on CdS
Andrea Besana, Veronica Regazzoni, Marco Faverzani et al. (+13 more)
Hexagonal group-IV
semiconductors have attracted increasing interest owing to their unconventional electronic and optical properties compared to the cubic diamond phase. However, the stabilization of these metastable allotropes in planar
heterostructures remains a major challenge. In this work, we demonstrate the epitaxial growth of planar hexagonal germanium on non-basal $m$-plane CdS substrates by low-energy
plasma-enhanced chemical vapor deposition. The role of growth temperature in the formation and stabilization of the hexagonal phase is investigated. X-ray diffraction, scanning transmission electron microscopy, and polarization-resolved Raman spectroscopy reveal the formation of epitaxial hexagonal germanium with the expected
crystal symmetry. In particular, the Raman response exhibits the characteristic polarization selection rules of the E$_\text{2g}$
phonon mode of hexagonal Ge. Conversely, photoluminescence spectroscopy does not reveal any Ge-related emission feature. Combined transmission electron microscopy observations and atomistic modeling show that strain relaxation is governed by a limited set of dislocation mechanisms, which efficiently relieve most of the mismatch strain within a few nanometers from the interface and can involve localized cubic stacking insertions. At greater distances from the interface, the progressive loss of hexagonal order is increasingly dominated by stacking-fault disorder, particularly I3-type defects. These results establish CdS as a promising template for the planar stabilization of hexagonal Ge and provide insight into the defect mechanisms governing strain relaxation in metastable group-IV
heterostructures.
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All authors Andrea Besana, Veronica Regazzoni, Marco Faverzani, Fabrizio Rovaris, Emiliano Bonera, Sonia Freddi, Elisa Brugaletta, Mohamed Zaghloul, Fabio Pezzoli, Francesco Montalenti, Monica Bollani, Daniel Chrastina, Anna Marzegalli, Antonio M. Mio, Emilio Scalise, Giovanni Isella
Nuclear Theory
Two-neutrino double-weak decays of $^{126}$Xe and $^{134}$Xe from different many-body methods
C. Brase, L. Jokiniemi, E. Kauppinen et al. (+4 more)
We calculate the
nuclear matrix elements and corresponding half-lives for the two-
neutrino double-electron capture of $^{126}$Xe and the two-
neutrino double-beta decay of $^{134}$Xe. We use different many-body methods: the
proton-
neutron quasiparticle random-phase approximation, the
nuclear shell model, the microscopic interacting
boson model, and an effective field theory for heavy
nuclei. For both
nuclei, all our half-life predictions are generally consistent with each other when including theoretical uncertainties for each method. Interestingly, for all calculations the lower range of the predicted $^{134}$Xe half-life is shorter than $T^{2\nu}_{1/2} \approx 2\times10^{24}$\,y, which may be within the reach of next-generation experiments. For $^{126}$Xe, our results typically predict one order of magnitude longer half-lives than those for $^{134}$Xe.
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All authors C. Brase, L. Jokiniemi, E. Kauppinen, B. Romeo, J. Kotila, J. Menéndez, A. Schwenk
Quantum Physics
CP-preserving channels
Indu Bala, Sourav Das and Swapan Rana
Completely positive (CP)
matrices are ubiquitous in modern science and technology with applications in optimization, graph theory, and
quantum entanglement. Recently, Johnston et al. [Linear
Algebra and its Applications, 2022] have cast CP
matrices into the framework of
quantum resource theories, where CP states serve as free states and CP-preserving channels act as free operations. This work addresses several questions raised in their work. Specifically, we provide the necessary and sufficient conditions of CP-preserving channels in small dimensions, which are necessary in higher dimensions, and discuss the resource quantification via the trace distance of non-negativity. By constructing an explicit counterexample, we demonstrate that the trace-distance measure of non-negativity violates strong monotonicity. We also provide an alternative proof that every CPDNN channel $\Phi:\MM_n\to \MM_2$ is CPCP. Additionally, we show that any unital CPDNN map $\Phi:\MM_2\to \MM_n$ is also CPCP.
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Strongly Correlated Electrons
Sign-optimized Quantum Monte Carlo
Julius S. Herz, Robin Schäfer, Matías G. Gonzalez et al. (+1 more)
The sign problem breaks the
polynomial scaling of
Quantum Monte Carlo methods. We alleviate it by rotation of the local basis of the
Hilbert space, such that the phase of off-diagonal
matrix elements of the rotated
Hamiltonian is minimized. These minima coincide with optima of the average sign. We
benchmark our method for frustrated Heisenberg antiferromagnets in one dimension and on the two-dimensional maple-leaf
lattice. Our approach reveals more efficient bases with improved sign in a large part of the parameter space for all models considered, enabling us to reach lower temperatures, on par with state-of-the-art numerical linked cluster expansions which we directly compare to.
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All authors Julius S. Herz, Robin Schäfer, Matías G. Gonzalez, David J. Luitz
Astrophysics of Galaxies
When galaxies cross cold fronts: wind tunnel simulations of ram pressure stripping
Elvis A. Mello-Terencio, Rubens E. G. Machado and Richards P. Albuquerque
Cluster collisions and mergers are among the most energetic phenomena in the low
redshift Universe. These interactions disturb the intracluster medium creating regions with density and temperature discontinuities, such as sloshing spirals. There is evidence that such environments can influence
galaxy evolution. This study aims to understand how a
galaxy that crosses an environment with discontinuities in density and temperature can be affected. To this end, a set of simulations was conducted using a wind tunnel setup into which a {MW-like mass}
galaxy was inserted. A total of eight models were created, namely two control runs and six with distinct density and temperature transitions along the tunnel, comprising simulations with low density and high density environments. Results show that
galaxies lose {considerably} more gas due to the higher density encountered when crossing denser and discontinuous regions in comparison to a constant density environment. The
star formation rate exhibits a brief enhancement when the
galaxy enters the denser section of the tunnel and {(u-i)} color index also undergoes slight changes, initially becoming bluer. However, even in the simulations with the most intense transitions, changes {in
star formation rate and color index} are not substantial, reaching at most 5% difference in relation to the control models. By the end of the simulation runs,
star formation rate and color index are similar to the control runs. These results suggest that crossing intracluster medium discontinuities can induce measurable effects in a
galaxy, but these are subtle and short-lived.
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Mesoscale and Nanoscale Physics
Skew scattering induced contribution to orbital Hall response
Dayana Joy, Vivek Pandey, Rhonald Burgos Atencia et al. (+1 more)
Our study provides the disorder-induced contribution to the orbital
Hall conductivity in three-dimensional Weyl semimetals with broken time-reversal
symmetry. Using the
quantum kinetic approach, we analyse the impact of side-jump and skew scattering contributions to the system. The dependence of the orbital
Hall conductivity on both disorder potential and the
Fermi energy is explicitly demonstrated. Furthermore, we demonstrate that the higher-order disorder contribution, especially from the third power of disorder potential, dominates the orbital
Hall conductivity under an oscillating electric field in a time-reversal
symmetry broken Weyl semimetal, suppressing other scattering mechanisms, including the side jump contributions. We can enhance the extrinsic orbital
Hall conductivity by tuning the strength of the disorder potential, applied energy, and choosing the system with appropriate Weyl node separation. Finally, our results are supported by numerical estimations and highlight potential experimental relevance for advancing orbitronics device technologies.
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All authors Dayana Joy, Vivek Pandey, Rhonald Burgos Atencia, Pankaj Bhalla
High Energy Physics (Phenomenology)
The Operational Resistance of Neutrinos: Epistemic Maturity vs. Technological Utility
Neda Razzaghi
Neutrinos represent a quintessential dichotomy in contemporary physics because they are epistemically mature components of our physical theories yet remain remarkably resistant to broad technological deployment. This paper examines the underlying structural asymmetry between scientific reality and technological utility. We argue that epistemic maturity, characterized by precise measurement and theoretical integration, does not automatically confer technological operability. Operability requires the reproducible construction of a signal recovery chain, which, in the case of
neutrinos, is systematically hindered by their weak interaction cross sections. To formalize this limitation, we introduce a dimensionless operability index denoted as $\mathcal{O}$, which synthesizes the simultaneous constraints of source power, detector scaling, and information throughput. Through this diagnostic lens, we demonstrate that
neutrino based systems are not fundamentally impossible but are instead relegated to a regime of intrinsic engineering inefficiency. We conclude that
neutrinos should be understood as epistemically central yet operationally resistant entities, whose engineering value remains limited to niche, strategic applications rather than general purpose communication.
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Astrophysics of Galaxies
Too many quiescent late-type galaxies or a matter of misclassification?
J. L. Tous, S. I. Raimundo and H. Domínguez Sánchez
In the local Universe, the terms late-type and early-type are used to describe, respectively, disc
galaxies with spiral arms and more bulge-dominated systems lacking spiral structure. These morphologies are often associated with different
star formation levels, motivating the classical scenario where late-type and early-type
galaxies are seen, respectively, as
star-forming and "red and dead" systems. To build a comprehensive picture of
galaxy evolution, we must understand the relationship between morphology and
star formation, and be able to explain more exotic configurations, such as quiescence in late-type
galaxies. Large morphological catalogues are valuable tools to address these questions, but they must not be used blindly. We show that selecting quiescent
galaxies classified as late-type in these catalogues leads to a clear excess of edge-on systems, with unreliable morphologies, compared with the general
galaxy population in the Sloan Digital Sky Survey. Consequently, the fraction of quiescent late-type
galaxies in this survey could be overestimated by a factor of two. Conversely, S0
galaxies, considered early-type discs without spiral arms, are under-represented at high inclinations. We conclude that the excess of edge-on quiescent late-type
galaxies can be explained if most of these systems are misclassified edge-on S0
galaxies. We make recommendations to remove this bias.
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Accelerator Physics
A corrective agentic hybrid RAG and an operations-grounded evaluation for a scientific facility
Rajat Sainju, Dariusz Jarosz, Hairong Shang et al. (+5 more)
Scientific user facilities accumulate decades of operational knowledge that no single search index covers: electronic logbooks, technical documents, internal wikis, operations chat messages, maintenance records, and live control-system data. We present APS-RAG, Advanced
Photon Source
Retrieval Augmented Generation, a deployed platform that makes the institutional knowledge at the Advanced
Photon Source (APS) accessible to staff through natural-
language queries, along with an operations-grounded evaluation. The
retrieval engine fuses dense, sparse, and knowledge-graph (KG) channels with query-type-adaptive reciprocal-rank fusion, adds a corrective agentic loop, and runs a native-tool ReAct executor over a Model Context Protocol (MCP) tooling layer. We construct APS-Bench, a 50-question, question-answering (QA)
dataset with auditable gold answers. Every
retrieval-augmented variant numerically improves strict vital-nugget recall over a naive BM25 baseline (63.8%), with the full corrective Agentic GraphRAG scoring (70.3%). The cross-encoder reranker contributes significantly to answer quality: removing it and allowing the LLM to score relevance drastically reduces strict vital recall by 32.8%. The graph channel and corrective loop contribute positively as expected, but the performance gains are marginal. Additionally, we also compare the performance of open-source and closed-source LLMs in final answer synthesis. We release the APS-Bench construction methodology, the six-layer evaluation harness, and the underlying codebase, along with the '/aps-rag'
retrieval agent skill framework, to support reproduction and adoption at other facilities. Together, the deployed platform and its operations-grounded evaluation present a promising workflow for trustworthy, statistically grounded AI assistance in facility operations, transferable to other large scientific instruments.
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All authors Rajat Sainju, Dariusz Jarosz, Hairong Shang, Michael Prince, Ryan M. Aydelott, Mathew J. Cherukara, Yine Sun, Michael D. Borland
High Energy Physics (Phenomenology)
Electromagnetic structure of charged and neutral strange vector mesons
Parada T. P. Hutauruk
We investigate the electromagnetic form factors of the charged $K^{*+}(892)$ ($u\bar{s}$) and neutral $K^{0}(896)$ ($d\bar{s}$) strange vector
mesons within the covariant Nambu–Jona-Lasinio model, employing the Schwinger proper-time regularization scheme to regularize ultraviolet divergences while incorporating the QCD aspect of
quark confinement. To this end, we evaluate the charge (electric) $G_C(Q^2)$,
magnetic $G_M(Q^2)$, and quadrupole $G_Q(Q^2)$ form factors, as well as the charge radii, of the charged $K^{+}(892)$ and neutral $K^{0}(896)$ strange vector
mesons. We find the charge radii to be $\langle r^2 \rangle_{K^{+}} = 0.45~\mathrm{fm}^2$ and $\langle r^2 \rangle_{K^{0}} = -0.04~\mathrm{fm}^2$, respectively, while the corresponding
magnetic moments are $\mu_{K^{+}} = 2.67,\mu_N$ and $\mu_{K^{*0}} = 0.032,\mu_N$. These results are consistent with other theoretical calculations and
lattice QCD simulations.
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Nuclear Theory
Light clusters in warm magnetized stellar matter: equation of state and thermodynamic response
Luigi Scurto, Stefano Burrello and Maria Colonna
Finite-temperature equations of state (EOSs) with a controlled treatment of composition-dependent effects are becoming increasingly important for modeling proto-
neutron stars and binary
neutron star merger remnants, where warm matter may coexist with strong
magnetic fields. At sub-saturation densities, light
nuclear clusters may also emerge with sizeable abundances. For beta-equilibrated matter, with or without
neutrino trapping, an interplay between
magnetic fields and light-cluster formation naturally arises in determining the matter composition: charge neutrality and weak
equilibrium transmit the effects of Landau quantization to the baryonic sector, modifying the
equilibrium charge content; at the same time, light-cluster formation also favors the increase of the
proton fraction by binding
protons into
nuclear clusters. In this work, we investigate this interplay within a generalized relativistic mean-field framework, in which light clusters up to alpha particles are included as explicit degrees of freedom and their in-medium dissolution is described through phenomenological binding-energy shifts. We show that the formation and subsequent dissolution of light clusters, combined with
magnetic-field effects, leave characteristic signatures in the matter pressure, the isothermal squared speed of sound, and the heat capacity, leading to significant modifications of the thermodynamic stiffness of the EOS and of the heat-storage properties of warm
stellar matter. Furthermore, we investigate the impact of the isovector terms of the EOS, namely its
symmetry energy, on these features. These results provide microscopic insights relevant to modeling the hydrodynamic and thermal
evolution of proto-
neutron stars and
neutron star merger remnants, while establishing a baseline for the development of more comprehensive finite-temperature EOSs for compact-
star applications.
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Quantum Physics
Exact and Fixed-Point Grover Search with Qudits
Tanay Roy
Grover's
algorithm provides a quadratic speedup for searching unstructured databases and is traditionally implemented with
qubits in
Hilbert spaces whose dimensions are powers of two. With the advent of
quantum platforms utilizing qudits—
quantum systems with more than two levels—there is a need to generalize Grover search to these architectures, including heterogeneous systems with qudits of varying dimensions. Here, we present a unified framework for qudit-based Grover search, detailing the construction of oracles and
diffusion operators with and without ancilla
qubits and generalizing deterministic and fixed-point search variants that ensure exact or bounded success probabilities. We analyze phase-matching techniques and provide explicit
circuit decompositions suitable for diverse hardware platforms. We also compare the corresponding trajectories on the Bloch sphere to provide an intuitive visualization of how the different phase choices amplify the target state. These results facilitate flexible, hardware-oriented protocols for implementing Grover search on qudit processors, potentially reducing
circuit depth and enhancing success probabilities, thereby offering a practical toolkit for
quantum computation and sensing applications leveraging multilevel
quantum systems.
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Quantum Physics
Geometric bounds on multiparameter Heisenberg scaling in optical metrology with limited squeezed resources
Atmadev Rai, Paolo Facchi and Vincenzo Tamma
The simultaneous estimation of multiple parameters is a central task in
quantum metrology, distributed sensing, and the calibration of large photonic interferometers. A fundamental question is how many independent parameter combinations can inherit Heisenberg scaling from a given number of squeezed probes in a multimode Gaussian network. Here, we answer this question for arbitrary passive linear optical networks. For a $p$-parameter, $M$-channel interferometer probed by $k$ single-mode squeezed states and at least one coherent state in the remaining channels, we show that the rank of the Heisenberg-scaling coefficient of the
quantum Fisher information
matrix is bounded by $n_{\rm HS}\le \min\{p,k(k+3)/2\}$, which corresponds to the maximum number of independent combinations of parameters that can be estimated with Heisenberg-scaling sensitivity. The bound separates into two geometrically distinct contributions. The covariance contribution of the
quantum Fisher information, which describes squeezing-enhanced fluctuations, provides at most $k(k+1)/2$ parameter combinations estimable at Heisenberg-scaling sensitivity, while the first-moment contribution provides at most $k$ additional independent parameter combinations with Heisenberg-scaling sensitivity. We identify the conditions for saturating these bounds and construct a passive family of interferometers that saturates these bounds.
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Astrophysics of Galaxies
Laboratory spectroscopy, theoretical characterization, and astronomical search for syn-propenethial (CH2CHCHS)
Germán Molpeceres, Carlos Cabezas, Marcelino Agúndez et al. (+5 more)
We report the laboratory characterization of the higher-energy isomer of propenethial, syn-CH2CHCHS. While the lower-energy isomer, anti-CH2CHCHS, was detected in the interstellar medium during the QUIJOTE line survey of TMC-1, we report the non-detection of the syn isomer in the same source, deriving an upper limit to its column density of 1.5 $\times$ 10$^{10}$ cm$^{-2}$. A subsequent theoretical investigation into the origin of this non-detection reveals that the most plausible formation pathway for CH2CHCHS is highly isomer-specific, producing nearly 95% of the anti isomer. This predicted branching ratio allows us to infer an even lower effective upper limit for the abundance of the syn isomer. In addition, calculations of tunneling-mediated unimolecular isomerization in the gas phase show that syn-CH2CHCHS converts to the lower-energy anti isomer on timescales of the order of 10$^{3}$ years. Overall, we conclude that the detection of syn-CH2CHCHS is highly challenging in both cold and warm interstellar environments. These results underscore the importance of electronic-structure and kinetic effects in determining isomer abundances across diverse interstellar environments.
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All authors Germán Molpeceres, Carlos Cabezas, Marcelino Agúndez, María Mallo, Yasuki Endo, Lucie Kolesniková, Gisela Esplugues, José Cernicharo
General Relativity and Quantum Cosmology
Test-particle dynamics in a noncommutative deformation of Einstein-Rosen waves
Diego Henrique Carvalho dos Santos, José André Lourenço, Davi C. Rodrigues et al. (+1 more)
We investigate phenomenological effects induced by a noncommutative deformation of Einstein–Rosen gravitational-waves within the framework of the Riemannian geometry of noncommutative surfaces developed by Chaichian et al. Considering a noncommutative structure between the radial and axial coordinates, we study perturbatively the motion of nonrelativistic test particles in the corresponding deformed geometry. We show that the deformation generates a coupling between the radial and longitudinal sectors, while the radial dynamics remains unaffected by the noncommutative deformation at the perturbative order considered. The induced longitudinal response is governed by a spectrally weighted functional of the gravitational-wave profile, implying that longitudinal observables depend on higher-order spectral moments than their commutative radial counterparts. As a consequence, noncommutative effects exhibit enhanced sensitivity to the ultraviolet structure of the gravitational configuration. We analyze separately monochromatic Einstein–Rosen waves and the localized Weber–Wheeler pulse. In the monochromatic case, the noncommutative correction induces a quasi-periodic longitudinal motion, whereas for the Weber–Wheeler pulse it produces an impulsive longitudinal response analogous to a gravitational velocity
memory effect. In addition, we derive an explicit analytical expression in commutative General Relativity for the residual radial velocity generated by the Weber–Wheeler pulse at large radial distances in the perturbative regime.
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All authors Diego Henrique Carvalho dos Santos, José André Lourenço, Davi C. Rodrigues, Etevaldo dos Santos Costa Filho
Lattice Field Theory
Analytic decomposition of two-body electroweak processes with left-hand cuts
André Baião-Raposo, Raúl A. Briceño, Nicolas Lang et al. (+2 more)
We derive an on-shell representation for electroweak $2+J\to2$ transition amplitudes involving two
hadrons in both the initial and final state for systems where there are left-hand singularities generated by light-particle exchange, e.g. one-pion exchange. The derivation treats the insertion of the electroweak current perturbatively, keeping only the leading-order contribution in the external field, while the hadronic interactions are treated to all orders, including one-particle exchange effects. We find that, in such processes, the amplitude can have logarithmic singularities, as well as one-particle pole singularities, due to these exchanges. We isolate those contributions, as well as previously identified triangle singularities. The result is expressed in terms of the purely hadronic amplitude, exchange-current kernels, triangle functions, and a class of short-distance transition functions that are real and smooth below unaccounted-for thresholds. While we consider only transitions with spinless particles, this work is an important step toward constraining form factors of systems involving nucleons or vector
mesons in the heavy
quark sector, where the one-pion-exchange singularity is quite close to threshold.
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All authors André Baião-Raposo, Raúl A. Briceño, Nicolas Lang, Felipe G. Ortega-Gama, Bianca Pol
Quantum Physics
Quantum-Limited Symbol-Blind Channel Estimation for Coherent State Discrimination
Hongxu Chen, Renzhi Yuan, Haifeng Yao et al. (+1 more)
Residual dispersion breaks temporal-mode matching in
photon-starved coherent links. For equiprobable $M$-ary PSK coherent states in a known spectral mode, with unknown symbols and carrier phase, we establish the
quantum limit for blind joint estimation of group delay and second-order dispersion: after eliminating the common phase, it is $4N_s\mathbf{C}$, set by the covariance of the centered generators alone. A multi-output
quantum pulse gate with
photon-number-resolving detection locally attains it and supports reception below the standard
quantum limit under turbulent fading.
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All authors Hongxu Chen, Renzhi Yuan, Haifeng Yao, Mugen Peng
High Energy Physics (Phenomenology)
Next-to-leading order corrections to radiative pion pair production via dispersion relations
Carlo M. Carloni Calame, Marco Ghilardi, Andrea Gurgone et al. (+5 more)
We compute the next-to-leading order corrections to the radiative return process $e^+ e^- \to \pi^+ \pi^- \gamma$ using a dispersive representation of the pion form factor for the calculation of loop integrals. We compare our results with those of the factorised scalar QED approach, as well as with previous predictions obtained by us in the generalised vector
meson dominance model. We show the numerical impact of the structure-dependent corrections on various observables of interest for radiative return experiments at flavour factories. Following recent input from the literature, we include in our calculation also corrections due to neutral pseudoscalar poles and we provide a first estimate of such contributions. We also investigate additional mechanisms contributing to final-state radiation at center-of-mass energies around the $\phi$-
meson resonance, such as radiative $\phi$ decays, presenting numerical results that are relevant for the KLOE experiment. These novel features are implemented in the Monte Carlo event generator BabaYaga@NLO, which can now be used to evaluate the impact of the modelling of pion-
photon interaction in radiative return measurements.
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All authors Carlo M. Carloni Calame, Marco Ghilardi, Andrea Gurgone, Guido Montagna, Mauro Moretti, Oreste Nicrosini, Fulvio Piccinini, Francesco P. Ucci
Mathematical Physics · Cross-listed from math.PR
The Yang-Mills measure on surfaces via Morse theory
Reda Chhaibi, Nguyen Viet Dang, Yannick Guedes Bonthonneau et al. (+2 more)
We introduce a Morse theoretical approach to the construction of the Yang–Mills measure on the space of connections of a compact Riemannian surface. This provides a direct continuous version of this measure which was previously obtained through
lattice approximations by Chevyrev in the case of the flat
torus and by one of the authors and Nohra for general compact Riemannian surfaces. The starting point is the new notion of a Morse gauge together with the resolution of random cohomological equations associated to Morse–Smale vector fields. This is achieved by improving exponential convergence to
equilibrium results for Morse–Smale gradient flows that were obtained by two of the authors in the context of the study of Ruelle spectra and by Jia, Stewart and Sverak in the context of simplified models from fluid mechanics. Combining these random solutions with the data given by the Morse complex, we introduce a free Yang-Mills measure on space of connections and, using classical tools from
stochastic differential equations, we show how to make sense of holonomies for random connections along a large class of curves. Finally, by setting a proper conditioning of this free measure through these random holonomies, we define the Yang–Mills measure and we compute its partition function together with the law of random holonomies with respect to this measure, recovering the formulas from the works of Migdal, Witten and Lévy.
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All authors Reda Chhaibi, Nguyen Viet Dang, Yannick Guedes Bonthonneau, Gabriel Rivière, Tat Dat Tô
Quantum Physics
Experimental Side Channel Analysis of Protocol Stages in Quantum Identity Authentication
Marwan Elawady, Lance Young, Contessa Wilburn et al. (+4 more)
Quantum networks can enable distributed computing and sensing. To realize these capabilities securely,
quantum identity authentication is essential. Without authentication at the
quantum layer, malicious repeaters may retain
entanglement instead of performing swapping, enabling man-in-the-middle attacks (MitM) between communicating parties. Authentication mitigates this threat by
embedding authentication
qubits within data
qubits at positions and bases based on a secret key shared a priori. While prior work analyzes security and MitM detection guarantees, physical layer side channel analysis remains unexplored. If an attacker infers protocol stages, it can avoid authentication
qubits and extract data
qubits, rendering authentication ineffective. To this end, we carry out experimental studies using a
quantum communication testbed. A beam splitter is used to tap a portion of the optical signal, allowing the observer to collect side channel data without disrupting the
quantum state. We evaluate two sampling settings, where 30% or 10% of the signal is diverted. The collected side channel data includes
photon arrival timing and optical power data obtained using a single-
photon detector and a power meter. Using this
dataset, we extract and engineer features that capture both timing dynamics and signal intensity variations. We then train machine learning models to classify protocol stages based solely on side channel observations. Our results show that protocol-stage inference is feasible with high accuracy, reaching 98% (F1-score 97%) at 30% sampling and 96% (F1-score 94%) at 10% sampling. These findings reveal an overlooked vulnerability and highlight the need for robust designs against side channel inference attacks.
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All authors Marwan Elawady, Lance Young, Contessa Wilburn, Blaine Keyton, Carrie Houston, Mohamed Shaban, Muhammad Ismail
Statistical Mechanics · Cross-listed from q-bio.PE
From Local Payoffs to Global Instabilities: A Spectral Cartography of Spatiotemporal Chaos in Canonical 2x2 Evolutionary Games
Ozgur Aydogmus
We develop a motif-based framework for spatiotemporal chaos in spatial evolutionary games and use it to map the dynamical phase diagram in the payoff plane. Using Boolean linearization of the imitate-the-best rule, we derive analytical instability thresholds for local motifs including invaders, cooperative pairs, stripe interfaces, and cooperative cores. These thresholds are obtained from payoff balance at contested motif interfaces and recover classical invasion thresholds of spatial evolutionary games, which emerge here as boundaries of the chaotic phase. Combining the Derrida slope with the asymptotic Hamming distance, we obtain a four-region cartography: ordered, transient-chaotic, sustained-chaotic, and subcritical-chaotic dynamics. The phase diagram is organized by density-dependent motif selection: different initial cooperator densities activate different instability mechanisms, yet a small set of motif-instability lines consistently bounds the sustained-chaos region across densities. This cartography reveals a subcritical chaotic phase (Derrida slope $s<1$ but asymptotic Hamming distance $d_\infty>0$), where infinitesimal perturbations decay while finite-amplitude perturbations sustain chaos. The motif-based framework is anchored by an exact
benchmark: for homogeneous backgrounds, the Boolean Jacobian yields an exact correspondence between the Derrida slope and spectral radius, linking damage spreading to deterministic instability.
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Nuclear Theory
Emergence of the halo in $^{11}$Li from full nuclear many-body dynamics
Yilong Yang and Pengwei Zhao
The two-
neutron halo nucleus $^{11}$Li is a paradigmatic
quantum many-body system whose large spatial extent and weak binding have long challenged a microscopic description from first principles. Using a neural-network variational Monte Carlo approach, we present an ab initio demonstration that the
halo structure of $^{11}$Li emerges directly from the underlying
nuclear interactions and full many-body dynamics. The calculation employs an essential
nuclear Hamiltonian constrained solely by few-body observables and reproduces the binding and separation energies of Li isotopes, as well as the isotopic trend of their matter radii. We identify a correlation between the
halo size in $^{11}$Li and the splitting of $P$-wave
neutron-alpha scattering phase shifts, establishing the crucial role of
neutron-alpha
spin-orbit interactions in
halo formation. Dineutron correlations are found to arise naturally from the many-body wave function without assuming a preformed core-plus-valence-
neutron structure. These results provide a microscopic understanding of
halo formation in $^{11}$Li and establish a link between few-body scattering observables and emergent many-body structure.
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Chemical Physics
Recommended Second Virial Coefficients for Nitrogen and Oxygen
Robert Hellmann, Giovanni Garberoglio and Allan H. Harvey
We provide recommended values for the second virial coefficient, $B(T)$, and its uncertainty, for molecular nitrogen and oxygen. The temperature range covered is $20-3000$ K for nitrogen and $20-2000$ K for oxygen. The recommendations are based on tuning previously published state-of-the-art ab initio pair potentials so that the $B(T)$ calculated from the potentials match selected high-accuracy experimental data; for nitrogen the tuning utilizes values of $B$ derived from literature density data with greatly reduced uncertainty by analyzing the data with the aid of ab initio calculated higher virial coefficients.
Quantum effects on $B$ are fully included with the path-integral Monte Carlo method. The resulting $B(T)$ have uncertainties similar to those of the best experimental data, but cover a much wider temperature range.
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High Energy Physics (Theory)
Krylov complexity and spectral density of BMN matrix model
Dibakar Roychowdhury
We use Krylov complexity as a typical diagnostic of
quantum many body dynamics in the context of BMN
matrix model at large mass gap. We calculate several physical entities, for example, the moments and return amplitudes at large mass deformation. We calculate them for both spread complexity of states as well as Krylov growth of operators in the
matrix model. We propose a general expression for the moments at any given order $n$. We also discuss orthogonal
polynomials for spread as well as operator Krylov complexity. In the context of the Krylov operator growth we further compute the spectral function and the density of states. A careful analysis of the spectral function near the resonance reveals various IR divergences in addition to the physical collective modes. These collective modes appear to be exceptionally stable due to large mass gap. On the other hand, the UV of the theory appears to be extremely damped due to higher scattering rates. We carefully diagnose these IR divergences near resonance which reveals that these collective modes are in fact non-propagating and should be thought of as
diffusion modes or relaxation modes with infinite relaxation time. We also calculate the Krylov variance and Krylov
entropy for the
matrix model and in particular at early time. The linear early time growth of the Krylov
entropy confirms the onset of
quantum chaos in the
matrix model at large mass gap.
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Optics
Universal Statistics of Energy and Information Flow in Random Electromagnetic Fields
Yuchen Ke, Nandini Bhattacharya, Stefan Rotter et al. (+1 more)
We establish a universal statistical description for the local flow of energy and information in random electromagnetic fields. The longitudinal Poynting flux, written as a Hermitian quadratic form of the transverse electric and
magnetic field components, follows a probability distribution that is completely determined by four
eigenvalues of an electromagnetic covariance
matrix. These flux
eigenvalues quantify forward transport, optical backflow, and polarization mixing, and reduce to the known paraxial and isotropic limits in the appropriate regimes – including strongly nonparaxial fields, where no universal description was known so far. Full-vector simulations of continuous and discrete disordered media confirm this universality. The same framework applies to the recently introduced Fisher-information flux, with the fields replaced by their sensitivity to a parameter, thereby unifying the statistics of local energy and information transport in random light and revealing the reversal of information flow across a parameter-dependent object.
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All authors Yuchen Ke, Nandini Bhattacharya, Stefan Rotter, Fabian Maucher
Fluid Dynamics
A Modified Moving Reference Frame Method for Propeller Resolution
Denis Andreev, Georgios Bletsos, Antonios Kritikos et al. (+2 more)
Accurate resolution of propeller-hull interaction is essential for predicting the self-propulsion point in ship CFD, yet motion-resolving methods such as sliding interfaces (SI) are computationally expensive, while the classical Moving Reference Frame (MRF) approach cannot capture unsteady interaction effects. Partially rotating grid methods bridge this gap by splitting the propeller rotation into a grid-resolved and an MRF component, but the abrupt transition between the rotating and stationary domains introduces discontinuities in the velocity field. This work presents a modified MRF (mMRF) formulation in which the reference-frame rotation rate is scaled by a spatially varying function that decays smoothly from unity near the propeller to zero at the domain interface, restoring velocity and pressure continuity across the boundary. The governing equations are derived and implemented in the RANS solver FreSCo$^+$, verified against the analytical Taylor–Couette solution, and applied to open-water propeller and Japan Bulk Carrier self-propulsion simulations at model scale. Both MRF and mMRF reproduce the principal integral propulsion quantities ($n$, $K_{\mathrm{T}}$, $K_{\mathrm{Q}}$, $1-t$, $1-w_{\mathrm{T}}$, $\eta_{\mathrm{R}}$) accurately, but the mMRF markedly reduces interface discontinuities and non-physical artifacts in the local flow field, particularly at large MRF fractions, at essentially the same computational cost.
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All authors Denis Andreev, Georgios Bletsos, Antonios Kritikos, Niklas Kühl, Thomas Rung
Quantum Physics
Experimental Protocol Fingerprinting in Quantum Networks via Physical Layer Side Channel Analysis
Lance Young, Contessa Wilburn, Carrie Houston et al. (+4 more)
Quantum communication is a key enabler of next-generation networks, leveraging
quantum entanglement to enable a new class of information exchange. While prior work has focused on the theoretical analysis of communication protocols, their exposure to physical layer side channel analysis remains largely unexplored. In classical systems, side channel analysis has been shown to reveal sensitive information without accessing the underlying data, raising the question of whether similar risks exist in
quantum networks. In this work, we investigate whether different
quantum communication protocols exhibit distinguishable signatures that can be inferred through passive side channel observations. We consider a threat model in which an observer accesses only a fraction of the optical signal without directly measuring the encoded
quantum states. Under this setting, we experimentally examine four representative protocols, namely
entanglement distribution,
quantum gate sequences, heralded
quantum key distribution, and
quantum identity authentication, realized on a polarization entangled
photon link. Observable physical layer features, including single
photon detection statistics and optical power measurements, are collected and used to construct protocol fingerprints. We develop a data-driven framework for protocol identification based on these observations. Our results show that protocol identity can be inferred with accuracy reaching up to 96% under 30:70 sampling configuration/optical tapping, while remaining distinguishable at 10:90 with accuracy ranging from 70-89%. Bell inequality measurements confirm that the sampling/tapping process preserves
entanglement, validating the non-destructive nature of the observation model. These findings demonstrate that side channel analysis can expose protocol-level information without disrupting
quantum correlations, introducing new security considerations.
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All authors Lance Young, Contessa Wilburn, Carrie Houston, Blaine Keyton, Marwan Elawady, Mohamed Shaban, Muhammad Ismail
Materials Science
A General Model of Interfacial Chemical Equilibrium in Phase-Field Method
Yanzhou Ji and Long-Qing Chen
We report a new approach to interfacial
equilibria among multiple solution phases in the phase-field method. It employs auxiliary non-conserved variables to describe the composition differences among different phases, and their temporal
evolution is driven by the differences among different chemical diffusional potentials. It is reduced to the Wheeler-Boettinger-McFadden (WBM) model of equal interfacial chemical compositions and to the Kim-Kim-Suzuki (KKS) model of equal interfacial chemical
diffusion potentials as two limiting cases. It can directly incorporate thermodynamic databases without any further approximations and simplifications. It is generally applicable to a wide range of problems involving composition
evolution and chemical
equilibria, including processes such as interdiffusion between two ordered phases not sharing any common composition range, which would pose difficulty to the existing treatments using WBM and KKS models.
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