Statistical Mechanics
Biorthogonal Conformal Dynamics in Non-Hermitian Quantum Quenches
Yifan Liu
Global quenches at one-dimensional critical points admit a boundary conformal field theory (BCFT) description in which Euclidean strip correlators are analytically continued to real time. We formulate this construction for interacting non-Hermitian critical systems, where a right ket alone does not specify the dynamical readout and the left covector is part of the microscopic quench protocol. Independent left and right preparations flowing to the same conformal boundary define the two temporal boundaries of a strip with generally complex one-sided extrapolation parameters; linear and antilinear
symmetry pairings are exploited to constrain this geometry. In the interacting Yang-Lee
spin chain, statically calibrated boundary data determine the biorthogonal dynamics of the complete-character return amplitude, a primary one-point function, and a spatial correlator. The imaginary part of the linear-paired extrapolation parameter predicts the temporal center of an independently evolved antilinear-paired one-point function at the $10^{-3}$ relative level; the same preparation phase controls local phase
evolution and the analytic-continuation path of boundary blocks. Further results test this formalism with a direct field-on quench, mixed left and right preparations, and a complex five-state Potts fixed point with complex primary dimensions. These results establish a BCFT framework for biorthogonal global quenches in interacting non-Hermitian critical systems, in which complex temporal-boundary data organize universal post-quench dynamics.
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Quantum Physics
The ebbs and flows of quantum learning and sensing
Matias Karjula, Teemu Ojanen, Tapio Ala-Nissila et al. (+1 more)
What is the relation between subsystem
quantum complexity and the emergence of computationally useful structure? We address this by studying a family of minimally tunable postvariational
quantum circuits, and show how spectral nonflatness and metrological response directly control the ensemble-typical information processing power. This unveils an intermediate "learning phase" that precedes the onset of
quantum chaos, characterized by pronounced nonflatness and sensitivity of readout states. The optimal information processing capacity improves with system size, while deep scrambling suppresses observable response. The results reveal how such features of random
quantum dynamics can be viewed as computational resources for scalable nonlinear computation.
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All authors Matias Karjula, Teemu Ojanen, Tapio Ala-Nissila, Moein N. Ivaki
Quantum Physics
A Zoology of Quantum Turing Patterns
Kazuki Ikeda
We explore
quantum Turing pattern zoology, where the same Lindblad equation supports a morphology atlas of stripes, spots, holes, labyrinths, and defects. The stable stripe species provides a quantitatively controlled case in which morphology and Gaussian witness loss separate parametrically. In particular, visible Turing stripes can remain after two Gaussian witness margins associated with the same $k_*$ mode cross zero in a completely positive Lindblad
lattice. The witness thresholds on the exact shell fall as $\mathcal{N}^{-1}$. The stripe nematic threshold tends to a nonzero value at fixed
lattice size, time window, and morphology criterion. The ratio of the morphology threshold to either witness threshold therefore grows with $\mathcal{N}$. Imaging and momentum-resolved covariance measurements probe these sectors separately.
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Mathematical Physics · Cross-listed from math.AP
The nested derivative criterion for determining elementary solutions to certain non-linear PDEs in one-dimensional space-time
Franceso Maltese
In this article, we have studied a particular criterion to establish if a particular class of nonlinear PDEs $\mathcal{O}_t u=\mathcal{O}_x u $ in unidimensional space-time $(x,t)$ admits elementary solutions respect to the spatial coordinate $x$, through the nested derivative method. Where a nested derivative is a generalization of the usual partial derivative of a order higher than one and, in terms of differentials operators, is a generalization of the Laguerre operator. This method, integrated with Liouville's
theorem and Galois theory and method by integrate by parts, establishes if solution of nested derivative equations admits elementary solutions respect with $x$. These solutions could help to study better evolutions of possible physical systems in space-time.
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High Energy Physics (Phenomenology)
Exploring chiral dynamics with low-energy electron- and positron-nucleon scattering
C. Weiss
Low-energy
lepton-nucleon scattering probes various expressions of the long-distance dynamics in the
baryon sector of QCD, governed by
chiral symmetry breaking and the $\Delta$ resonance. We discuss some specific studies that could be performed with combined electron- and positron-nucleon scattering at lab energies $E_{e\pm} \lesssim$ 500 MeV. They include: (a)
chiral dynamics in the low-$Q^2$ nucleon elastic form factors (peripheral charge and current densities); (b) two-
photon exchange effects in the target normal single-
spin asymmetry and beam charge asymmetry in elastic and inclusive scattering ($\Delta$ excitation); (c) nucleon generalized polarizabilities in virtual Compton scattering with beam charge asymmetry measurements.
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Optics
Wavefront shaping of terahertz radiation using two-color flying-focus pulses with time-dependent focal velocities
A.L. Elliott, H. Markland, K.G. Miller et al. (+3 more)
Properly phased two-color
laser pulses drive photoionization currents that emit broadband THz radiation. With a conventional two-color pulse, the ionization front travels at a nearly constant superluminal velocity, generating THz radiation with conical wavefronts at a Cherenkov-like angle. Here we show that the dynamic intensity peak of a two-color ultrashort flying-focus pulse can be used to control the shape of the THz wavefronts. Simulations demonstrate that non-uniform motion of the intensity peak and the ionization front it drives result in a time-dependent emission angle that determines the wavefront shape. A decelerating intensity peak, in particular, enables the generation of THz radiation with
parabolic wavefronts that are well suited for collection and focusing.
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All authors A.L. Elliott, H. Markland, K.G. Miller, S.W. Jolly, J.J. Pigeon, J.P. Palastro
Quantum Physics
Vacuum viscosity and relativistic inertia: Motion of a massive object with charged internal degrees of freedom interacting with a classical field
Jen-Tsung Hsiang and Bei-Lok Hu
Our present investigation into a rather rudimentary problem is motivated by two classes of problems studied since the 70's, cosmological particle creation and its more accessible analog, the dynamical Casimir effect on the one hand, and
quantum friction a neutral atom moving along a dielectric surface would experience, on the other. The backreaction effects of produced particles being able to isotropize the expansion of the universe, or to slow down the moving mirror can be understood via the concept of
vacuum viscosity arising from fluctuations of the
quantum field. We want to track down the origin of this effect by asking the question whether a moving massive $M$ object with a charged internal degrees of freedom $\chi$ interacting with a free unbounded classical field $\phi$ at zero temperature would experience a viscous force, similar to the said precedents. Adopting a microphysics model for optomechanics which can treat the unequal tripartite $\chi$-$\phi$-$M$ interactions, we first perform a nonrelativistic calculation, which seems perfectly legitimate considering the needs of atomic physics, and found the answer to be yes, but a relativistic covariant calculation says no. We identify where the nonrelativistic framework is defective. The resolution of this latent yet real conflict is technically nontrivial but physically quite inspirational. It results in added enriched contents to Newton's first and second laws when the principles of special relativity are enforced, and rules to follow to get the correct nonrelativistic answer
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Quantum Physics
Reinforcement Learning to Harness Approximation Errors for Long-Time Quantum Simulation
Yu-Bo Shi, Markus Heyl, Roderich Moessner et al. (+2 more)
Accurate digital
quantum simulation at long times is limited by the accumulation of errors inherent to approximate simulation. Here we introduce RL-Trotter, a reinforcement-learning framework that treats unavoidable approximation errors as resources for error correction rather than merely imperfections to suppress. We show that low-dimensional information from conservation laws, such as the energy and energy variance, provides a sufficient learning signal to guide the
agent, which learns to adapt a single scalar—the next Trotter step size—without access to the target wave function. By optimizing the entire long-time
evolution rather than individual steps, RL-Trotter discovers self-correcting sequences in which later errors compensate for those accumulated earlier, increasing the accuracy of the long-time dynamics. The learned policies are intrinsically robust to measurement noise, substantially reducing measurement overhead. They also generalize to previously unseen, physically similar initial states and transfer from small, classically simulable systems to systems an order of magnitude larger. This enables a practical protocol based on classical pretraining followed by direct deployment or limited fine-tuning on
quantum hardware. Our results establish a broader perspective for
quantum algorithms: errors in approximate
evolution can be orchestrated into resources for accurate and resource-efficient
quantum dynamics.
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All authors Yu-Bo Shi, Markus Heyl, Roderich Moessner, Marin Bukov, Hongzheng Zhao
History and Philosophy of Physics
Minkowski's Geometric Explanation of Lorentz Contraction
Tilman Sauer
Hermann Minkowski's original explanation of relativistic length contraction using a space-time diagram and conic section geometry of a standard hyperbola is reconstructed on the basis of unpublished manuscript notes dated to the spring of 1908. The manuscript notes likely reflect Minkowski's preparation of a lecture to physics and mathematics teachers. They reveal Minkowski as an educator as well as a promoter of a mathematization of the physical sciences. I also comment on his interpretation of Einstein's work and on the use of
language in his popularization of mathematics.
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Quantum Physics
Boltzmann counting in Hilbert space
Raúl O. Vallejos, Isadora Veeren, Frederico Brito et al. (+1 more)
We introduce a
geometric entropy for
quantum preparations, defined as the logarithm of the
Hilbert-space volume of pure states compatible with a given set of constraints. This construction extends Boltzmann's counting perspective to the
quantum setting, where compatible states need not be orthogonal and the relevant notion of "number of states" is naturally replaced by a volume in state space. We analyze three classes of constraints: restriction to a subspace, fixed expectation values, and coarse-grained subsystem descriptions. For representative examples, including subspace projection,
spin expectation values, partial trace, and an imperfect detector map, we obtain explicit scaling laws and closed-form expressions for the associated volumes. The resulting framework provides a
geometric measure of
quantum ignorance at the level of the preparation and complements
entropy notions based on density
matrices and coarse graining.
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All authors Raúl O. Vallejos, Isadora Veeren, Frederico Brito, Fernando de Melo
Cosmology and Nongalactic Astrophysics
Testing Statistical Isotropy in the FRB Sky Distribution: A Selection-Function-Aware Framework
Bruno W. N. Ribeiro, Thais Lemos, Carlos A. P. Bengaly et al. (+5 more)
We perform a test of statistical isotropy in the Universe using the sky distribution of fast
radio bursts (FRBs), based on a compilation of $4066$ events detected by multiple surveys. Our method is based on the two-point angular correlation function $w(\theta)$ as in the Landy–Szalay
estimator, together with a tomographic absolute-anisotropy statistic, and estimates their observational uncertainties from complementary jackknife and bootstrap resampling. Both
estimators are confronted with hierarchical ensembles of isotropic mock catalogs that propagate the uncertainties of empirically reconstructed survey selection functions, as well as the Poisson fluctuations of the isotropic realizations. The significances are obtained from a covariance-aware, SVD-regularized $\chi^2$ statistic calibrated empirically against the mock ensemble, and we evaluate four nested scenarios that progressively incorporate a
Galactic-plane mask and the survey selection functions. As for our results, we find that the raw FRB sky is strongly inconsistent with isotropy;
Galactic masking alone reduces the tension by only a factor of $\sim 3$, whereas the selection functions reduce it by nearly four orders of magnitude, showing that the apparent anisotropy is driven by the highly non-uniform sky coverage of the contributing surveys, overwhelmingly dominated by CHIME. Only when both effects are combined we obtain that the observed distribution is fully consistent with statistical isotropy. This result is independently corroborated by the absolute-anisotropy
estimator, and is stable under variations of the analysis parameters. Therefore, we find that the FRB sky distribution is consistent with statistical isotropy, helping confirm one of the main predictions of the standard model scenario.
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All authors Bruno W. N. Ribeiro, Thais Lemos, Carlos A. P. Bengaly, Rodrigo Gonçalves, K. E. L. de Farias, Lázaro L. Sales, Amilcar R. Queiroz, Jailson Alcaniz
Quantum Physics
Preparation of Large Fock States in Resonators with High Probability
Lucas R. S. Santos, Ciro M. Diniz, Daniel Z. Rossatto et al. (+1 more)
Large Fock states are important resources for bosonic
quantum information and
quantum-enhanced metrology, but preparing them with high probability at large excitation numbers remains challenging, as deterministic methods become increasingly control-intensive, while measurement-based approaches typically suffer from low heralding probabilities. Here we propose a protocol that combines
quantum nondemolition
photon-number encoding with
quantum amplitude amplification to enable high-probability heralded generation of large Fock states. Starting from a cavity mode prepared in a coherent state,
Quantum Phase Estimation encodes
photon-number information into a multi-
qubit register, while
Quantum Amplitude Amplification boosts the probability of a desired target outcome before measurement. The scheme has an immediate implementation in dispersive
circuit-QED, but can be analogously adapted to other bosonic platforms with QND
photon-number readout, such as cavity-QED. With a register of up to eight
qubits, near-deterministic preparation of Fock states with hundreds of excitations is possible. We also show that the protocol can serve as the first stage of an extension toward generating a two-mode NOON state via a conditional beam-splitter operation.
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All authors Lucas R. S. Santos, Ciro M. Diniz, Daniel Z. Rossatto, Celso J. Villas-Boas
Quantum Physics
SAKE: Spectral Autodiff Kernel Expansion for Geometric Liouvillian Transport. A Differential-Geometric Framework for Response Transport in Quantum Dynamical Systems
Eric R. Bittner, Carlos Silva-Acuna, Hao Li et al. (+1 more)
We introduce the Spectral Autodiff Kernel Expansion (SAKE), a differentiable computational framework for transporting nonlinear spectroscopic response between neighboring
quantum dynamical models. Rather than recomputing multidimensional spectra independently for each
Hamiltonian or Liouvillian, SAKE constructs local transport expansions about a reference model by combining forward-mode automatic differentiation with Duhamel transport theory. Automatic differentiation generates first-, second-, and third-order derivatives of the parameter-dependent Liouvillian, which are assembled into a pathway transport operator that maps the nonlinear response of a reference model onto neighboring systems. The framework is validated for a four-level excitonic dimer possessing an $su(2)\times su(2)$
symmetry by comparing second- and third-order transported pathway operators with exact projected transport
matrices obtained from direct calculations. The third-order expansion accurately reproduces the projected transport operator and its associated pathway mixing. Beyond providing an efficient computational strategy, the transport operator reveals how coherent and dissipative perturbations redistribute amplitude among double-sided Feynman pathways, exposing mechanistic information that is not directly apparent from the nonlinear spectrum. SAKE thereby establishes a differentiable computational framework for nonlinear spectroscopy that supports efficient local parameter exploration, sensitivity analysis, and future inverse-design applications.
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All authors Eric R. Bittner, Carlos Silva-Acuna, Hao Li, Simon Paiva-Ortega
Quantum Gases
Structural complexity of an SU(3) Fermi Hubbard model
Jiani Fu, Zewen Zhang and Eduardo Ibarra-García-Padilla
Two-dimensional
quantum gas microscopy provides an unparalleled tool to study
quantum many-body systems using ultracold atoms. For the SU(2)
Fermi Hubbard model (FHM), access to
spin-resolved projective measurements has been vital for quantifying correlation functions and mapping out the phase diagram. Recent progress in
quantum gas microscopy for experiments with ultracold alkaline-earth atoms, which are well described by the SU(N) FHM and are predicted to host exotic ground-state phases, calls for the development of theory-free numerical techniques to extract physical information from their projective measurements. To that end, we evaluate the multiscale structural complexity of snapshots of an SU(3) FHM in the square
lattice at $1/3$-filling. We employ mean-field theory to generate
spin-resolved density distributions and compute their structural complexity using rectangular coarse-graining windows. We demonstrate that these complexities are linked to relevant physical observables such as the
entanglement entropy, and are extremely sensitive for locating phase boundaries. The results presented here validate the structural complexity as an efficient and reliable tool for analyzing the outputs of SU(N)
quantum gas microscopes, offering a theory-free property, immediately accessible to experiments.
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Optics
Symmetry-guided modal control in elliptical femtosecond-laser-written photonic waveguides
Tadas Paulauskas, Ubaid Ur Rehman, Eimantas Dermauskas et al. (+1 more)
Few-mode photonic
circuits can increase functionality without multiplying waveguide paths, but bends and fabrication errors can mix their transverse modes. We investigate a strategy in which waveguide confinement and perturbation parity are engineered together in vertically elliptical, femtosecond-
laser-written glass waveguides. The intended modal basis comprises the even $1S$ mode and the vertically odd $2P_y$ mode. No window-converged $2P_x$ state is resolved for a lower-confinement (LC) design, whereas a higher-confinement (HC) design guides $2P_x$, which must therefore be isolated by
symmetry. In scalar beam-propagation calculations, the $1S$-$2P_y$ propagation-constant splitting predicts the optimized periods of a vertically modulated coherent modal splitter to within $1.0\%$. Horizontal S-bends remain parity-mismatched for $1S \leftrightarrow 2P_y$ coupling, while the
symmetry-allowed HC $1S \rightarrow 2P_x$ transfer reaches only $0.6\%$ at the largest displacement. At a displacement of $150~\mu\mathrm{m}$, the HC design retains approximately the same $2P_y$ power as the LC design retains at $40~\mu\mathrm{m}$. Thermal and
stochastic writing-error calculations reveal the resulting trade-off: stronger confinement improves modal-power retention, but writing jitter that breaks $x$-parity can populate the guided $2P_x$ mode. These results demonstrate how modal-basis engineering can shift part of the crosstalk-control burden from the trajectory to waveguide
symmetry, supporting joint path–mode degrees of freedom in
quantum photonic applications.
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All authors Tadas Paulauskas, Ubaid Ur Rehman, Eimantas Dermauskas, Valdemar Stankevic
Optics
Geometric Control of Cat States in High Harmonic Generation
Arti Gaharwar, Rocío Borrego-Varillas, Marcelo F. Ciappina et al. (+6 more)
High-harmonic generation (HHG) provides a powerful platform for exploring the interaction between intense
laser fields and matter on ultrafast timescales. Beyond its conventional description in terms of emitted radiation and electron dynamics, a fully
quantum treatment of HHG reveals that the nonlinear light-matter interaction can modify the
quantum state of the driving field itself, establishing correlations between the fundamental and harmonic modes. This perspective opens new possibilities for using HHG as a tool to engineer and control nonclassical states of light. In this work, we investigate the
geometric properties of optical Schroedinger cat states generated in HHG via conditioning and post-selection. By analyzing the coherent-state displacements induced by different structured driving fields, we characterize the resulting phase-space
evolution and the associated
geometric phases of the generated
quantum states. Particular emphasis is placed on how the polarization and spatial-mode structure of the driving light influence the geometry and
evolution of displaced coherent states. Our results demonstrate that structured light offers a versatile means of controlling the
geometric dynamics of HHG-generated cat states across the parameter space. Furthermore, we discuss the prospects for realizing genuinely topological optical cat states by exploiting more complex structured light configurations.
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All authors Arti Gaharwar, Rocío Borrego-Varillas, Marcelo F. Ciappina, Anna G. Ciriolo, Javier Rivera-Dean, Philipp Stammer, Paraskevas Tzallas, Emilio Pisanty, Maciej Lewenstein
Materials Science
Effects of the surface on double surface Fermi arcs in a realistic tight-binding model of Na$_3$Bi (100)
Vasilios K. Passias and Lucas K. Wagner
Na$_3$Bi is a topological Dirac semimetal (TDSM) that can support double surface
Fermi arcs (DSFAs), which are important for its material classification and their potential use in spintronic devices. However, it is unclear how the surfaces affect realistic Na$_3$Bi (100) systems. To investigate the effects of diverse surfaces on DSFAs, we consider first principles derived tight-binding models of two Na$_3$Bi (100) terminations. On the stoichiometric termination, we find DSFAs as expected. On the non-stoichiometric structure there are DSFAs on one termination and two loops that retain many of the properties of DSFAs. Thus, the local properties such as
spin momentum locking and hybridization with the Dirac points appear to be more robust than their global connectivity. That is, the surface can reshape the arc fingerprint without destroying the arc-like physics.
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Quantum Physics
Counterexamples to the fractional coloring conjecture for triply efficient shadow tomography
Jędrzej Stempin, Santiago Llorens and Felix Huber
Fractional graph colorings are useful for the Shadow
tomography of Pauli observables. In practice, it is desirable that any experimentally interesting set of Pauli operators has a small fractional chromatic number $\chi_{f}$ for its anticommutation graph.
Conjecture 13 in King, Gosset, Kothari, and Babbush [PRX
Quantum 6, 010336 (2025)] states that if $B_\epsilon(\varrho)$ is the set of Pauli observables having expectation value magnitude at least $\epsilon$ in some given
quantum state $\varrho$, then the fractional chromatic number of the anticommutation graph $G$ induced by $B_\epsilon(\varrho)$ is $O(\epsilon^{-2})$. In other words, it asserts that there exists a constant $C$ such that $\chi_{f} \cdot \epsilon^2 \leq C$ on all states and graphs. If the
conjecture were true, it would imply that there exists a triply efficient Pauli shadow
tomography algorithm for any subset $S$ of Pauli observables, provided that there is also an efficient fractional coloring
algorithm for the set $B_\epsilon$. Here we show that the
conjecture is false by constructing a family of states and observables for which no finite $C$ satisfying the bound exists. We also give a more general construction relying on the commutation index or $\beta$ number of a graph. The key ingredient in the proofs can be seen as an instance of the amplification trick, where fractional chromatic numbers, $\beta$ numbers, and expectation values are amplified through lexicographic graph products.
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Medical Physics · Cross-listed from eess.IV
Flow Matching-Based PET Image Reconstruction
Fumio Hashimoto, Ziqian Huang, Tatsuya Yokota et al. (+1 more)
Generative models have shown strong potential for positron emission
tomography (PET) image reconstruction. Although
diffusion model-based reconstruction methods have demonstrated promising performance, they often require many reverse sampling steps with data-consistency updates incorporated into the sampling process. Flow matching offers an attractive alternative because it can directly estimate clean images from intermediate states, allowing data-consistency refinement to be separated from flow propagation. In this work, we proposed flow matching-based PET image reconstruction methods. We first established PET-FlowDPS by incorporating Poisson likelihood guidance with an expectation-maximization (EM)-based preconditioner into the FlowDPS framework. We then proposed a model-based PET reconstruction method that used a pretrained flow matching model as a prior, in which the flow-based prior, PET data refinement, and
stochastic propagation were interpreted within an approximate
Bayesian framework. Experimental results using [$^{\text{18}}\text{F}$]FDG
brain PET
datasets showed that the proposed method achieved better bias-variance trade-offs across different dose levels compared with other reference methods. These results demonstrated the potential of flow matching as a generative prior for quantitative PET image reconstruction.
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All authors Fumio Hashimoto, Ziqian Huang, Tatsuya Yokota, Kuang Gong
Superconductivity
Josephson transport in YBa${}_{2}$Cu${}_{3}$O${}_{7}$ weak links created by focused-helium-ion-beam irradiation: Analysis based on diffusive-SNS-junction model
Tetsuro Misawa, Shigeyuki Ishida, Hiroshi Eisaki et al. (+3 more)
Fabrication of YBCO weak links by focused helium ion beam irradiation is a promising approach for realizing high-temperature superconducting Josephson junction devices. Although empirical dose-characteristic relationships have been established, the underlying transport mechanisms remain unclear. In this study, we perform a detailed investigation of the transport properties of YBCO weak links fabricated using a helium ion microscope (HIM) and provide a unified phenomenological description of the observed behavior based on the theory of SNS junctions with a diffusive metallic interlayer. We demonstrate that the temperature dependence of the critical current $I_{\mathrm{c}}$ and the $I_{\mathrm{c}}R_{\mathrm{n}}$ product are well described by diffusive SNS junction models over a wide temperature range. Analyses show that the observed dose dependences of $I_{\mathrm{c}}$ and $I_{\mathrm{c}}R_{\mathrm{n}}$ cannot be explained solely by variations in the effective Thouless energy $E_{\mathrm{T}}$. The discrepancy suggests reduced interface transparency and a reduction in the density of states, leading to a decrease in the effective number of conducting channels contributing to transport. This interpretation is also consistent with the observed exponential increase in $R_{\mathrm{n}}$ with irradiation dose. These results provide a
diffusion-based framework for understanding Josephson transport and guiding junction design in helium-ion-irradiated YBCO weak links.
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All authors Tetsuro Misawa, Shigeyuki Ishida, Hiroshi Eisaki, Yukinori Morita, Shinichi Ogawa, Chiharu Urano
Statistical Mechanics
Fluctuation-Controlled Asymmetric Kinetics in Metal-Insulator Transitions
Tapas Bar, David Pesquera, Timm Swoboda et al. (+5 more)
We report asymmetric kinetics in thermally driven metal-
insulator transitions (MITs) in 1T-TaS$_2$. Using combined transport, calorimetric, and Raman measurements, we show that the transition proceeds via burst-like avalanches during cooling, while remaining continuous during heating. Although bulk transport is masked by percolative conduction, local probes and thermal measurements reveal intrinsic asymmetry in the transformation pathways. Using controlled nonequilibrium thermal perturbations generated by pulsed Joule heating, we demonstrate that the phase-ordering dynamics remains strongly athermal during cooling, whereas during heating fluctuations progressively overcome nucleation barriers, leading to a smooth transformation. The distinct responses to thermal perturbations indicate different degrees of athermality of the two hysteresis branches, which govern the transformation pathways and give rise to the observed kinetic asymmetry. These results establish a general framework in which the degree of athermality controls pathway selection in first-order phase transitions.
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All authors Tapas Bar, David Pesquera, Timm Swoboda, Arnau Villalobos-Martin, Cristian Rodriguez-Tinoco, Pol Lloveras, Marianna Sledzinska, Javier Rodriguez-Viejo
Applied Physics
Mid-infrared distributed-feedback lasing from black phosphorus under nanosecond excitation
Julien Brodeur, Laure Sène and Stéphane Kéna-Cohen
Mid-infrared (MIR) light sources compatible with silicon photonics are highly desirable for environmental sensing and free-space optical communications. Conventional GaSb-based
quantum-well and interband-cascade
lasers, however, rely on complex epitaxial
heterostructures, complicating their integration with silicon photonic platforms. Here, we demonstrate a room-temperature MIR surface-emitting distributed-feedback (DFB)
laser using black phosphorus (b-P) as the active gain medium. By deterministically integrating exfoliated b-P flakes onto lithographically patterned SiO$_2$ gratings, we obtain narrowband emission with a full width at half maximum below 3 nm under 1064 nm optical excitation. The lasing wavelength is tunable from 3.79 to 4.05$~\mu\text{m}$ through the b-P flake thickness, covering a technologically important region of the mid-infrared. Room-temperature thresholds as low as $(0.25 \pm 0.07)\ \text{mJ/cm}^2$ are achieved under nanosecond excitation. Upon cooling to 110 K, the threshold decreases tenfold to $(0.015 \pm 0.005)\ \text{mJ/cm}^2$. These results establish planar b-P DFB cavities as a promising platform for heterogeneously integrated MIR
lasers based on van der Waals
semiconductors.
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Cosmology and Nongalactic Astrophysics
Non-minimal Unimodular Inflation
Manda Malekpour, Kourosh Nozar, Fateme Rajabi et al. (+1 more)
We study an extension of the unimodular cosmological inflation in the context of the non-minimal coupling of a generic scalar field with gravitational sector. We consider the non-minimal coupling of the scalar field and
gravity as the only source of energy-momentum tensor in this setup. Without introducing new particles other than those already existing in electroweak theory, the generic scalar field's non-minimal coupling is responsible for the generation of the seeds of perturbations for structure formation and the observed
Cosmic Microwave Background anisotropies in this scenario. We calculate inflation parameters in both the Jordan and Einstein frames, and then we study
primordial spectral indices for slow-roll parameters in Einstein's frame at the first and second orders. The numerical results of this model are consistent with the Planck2018 and BICEP/Keck joint data sets in some subspaces of the model parameters space. By considering a sufficient amount of inflation, we estimate the strength of the non-minimal coupling parameter, $\xi$, to find appropriate new constraints on the values of this parameter. By comparing the numerical values of the inflation observables in two frames and also with observation, we comment on the issue of frames in this framework.
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All authors Manda Malekpour, Kourosh Nozar, Fateme Rajabi, Narges Rashidi
Biological Physics
Growth phases of an active tissue: determinate, indeterminate, and proportionate
Jigyasa Watwani, K. Vijay Kumar and Vishal Vasan
Growth may cease at a target size or continue throughout life: the determinate and indeterminate phenotypes. We develop an active viscoelastic continuum model of a tissue growing along one axis, in which
cell division and death generate active stresses. We find two asymptotic states: one in which the tissue reaches a relative size fixed by its material parameters, and one in which it elongates linearly without bound. Which state is realised is set by the ratio of active stress to elastic modulus. The transition originates in a bound on the elastic stress the tissue can support: a sufficiently large activity can never be balanced. In a tissue made of parts with different material properties, the growing phase settles into fixed length proportions, set by the mechanical impedances of the parts rather than inherited; matching impedances to initial lengths preserves the proportions the tissue began with. Determinate, indeterminate and proportionate growth thus appear as regimes of one continuum mechanical framework.
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Quantum Physics
Squeezed- and coherent-state quantum key distribution over a deployed hybrid fibre-free-space channel
Adnan A.E. Hajomer, Huy Q. Nguyen, Ivan Derkach et al. (+14 more)
Quantum networks will combine optical fibre with free-space links, yet continuous-variable
quantum key distribution (CV-QKD) has been developed predominantly for one medium or the other, while operation across concatenated fibre-free-space channels remains largely unexplored. The two media impose contrasting requirements: fibre transmission is stable and permits long processing intervals, whereas atmospheric propagation imposes transmittance fluctuations that degrade security and must be resolved on short timescales. Here we demonstrate a locally generated local oscillator CV-QKD with both Gaussian-modulated coherent and squeezed states over a deployed hybrid channel comprising a 620-m free-space link and 2 km of deployed fibre, with a total loss up to 20 dB. Rather than adapting the optics to each medium, we move channel adaptation to the post-processing, through a unified adaptive post-processing framework coupling transmittance-based clustering, residual-fading mitigation by covariance-
matrix averaging or de-fading, and rate-adaptive blind reconciliation, which alone recovers up to 19% additional key. The same adaptive-processing principle is applied to both protocols, while accounting for their different security analyses and statistical requirements, yielding asymptotic secret-key rates of 0.42 Mbit per sec for the coherent-state protocol and 0.93 Mbit per sec for the squeezed-state protocol under the respective channel conditions, and establishing squeezed-state CV-QKD over a deployed atmospheric channel. These results show that adaptation to the transmission medium can largely be transferred to the data-processing layer, providing a route towards heterogeneous
quantum networks spanning fibre, terrestrial free-space and satellite links.
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All authors Adnan A.E. Hajomer, Huy Q. Nguyen, Ivan Derkach, Andreas B. Kidmose, Edoardo Rossi, Mattia Sabatini, Yoann Pietri, Marco Avesani, Francesco Vedovato, Michael Hentschel, Radim Filip, Giuseppe Vallone, Vladyslav Usenko, Tobias Gehring, Soren Forchhammer, Paolo Villoresi, Ulrik L. Andersen
General Relativity and Quantum Cosmology
Effective Field Theory for Freezing Gravity with Minimally Coupled Matter
Zhibang Yao
Freezing
gravity (FG), a phantom-crossing dark energy model, was recently proposed in the absence of matter. In this work, we study FG minimally coupled to a perfect fluid through a detailed cosmological perturbation analysis and derive the conditions for the absence of ghost and gradient instabilities. The ghost stability conditions are obtained analytically without taking the high-$k$ limit, yielding the ghost-free range of scales and a finite cutoff when it exists. In the branch where a finite cutoff is already present in
vacuum, we find that matter coupling lowers it relative to its
vacuum value. Moreover, in the high-$k$ regime, the gradient stability condition guarantees a positive effective gravitational coupling for cold dark matter. We further show that two characteristic properties of FG persist in the presence of matter. First, the background and perturbation sectors remain separated, in the sense that they are controlled by independent sets of parameters, allowing FG to realize arbitrary background evolutions, including phantom crossing, while maintaining stable perturbation dynamics. Second, the scalar degree of freedom of FG becomes non-dynamical in the large-scale limit at linear order, while propagating with a finite speed of sound on small scales. Whether this behavior persists to arbitrarily high orders in perturbation theory, thereby avoiding the potential strong-coupling issue, requires further investigation through a nonlinear perturbation analysis. To make contact with large-scale structure and gravitational
lensing observables, we also derive the effective gravitational coupling and gravitational slip within the quasi-static regime and express our results in terms of the EFT parameters.
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General Relativity and Quantum Cosmology
Analyzing Quasi-normal modes spectrum in asymptotically de Sitter black bounces and their optical appearance
G. Alencar, Albert Duran-Cabacés, A. Lima et al. (+2 more)
This work explores asymptotically de Sitter black-bounce spacetimes, obtained as a regular extension of the Schwarzschild-de Sitter geometry via the Simpson-Visser prescription. The resulting family of solutions provides a smooth interpolation between regular black holes, extremal configurations, and traversable wormholes within a single geometrical framework. In particular, we verify the regularity of the spacetime by showing that (some of)
curvature invariants, including the Kretschmann and
Ricci scalars, remain finite at the origin for any non-vanishing value of the regularization parameter $a$, ensuring geodesic completeness. An analysis of the effective stress-energy tensor reveals a violation of the null energy condition, which can be consistently interpreted in terms of a composite source involving a phantom scalar field coupled to nonlinear electrodynamics. Subsequently, we investigate the observational signatures of these geometries by studying: i) null geodesic propagation and ii) constructing the associated optical appearance. In particular, we determine the shadow radius and characterize the structure of
photon rings through numerical ray-tracing procedure. Finally, we compute the spectrum of axial gravitational perturbations using a pseudospectral approach, obtaining the quasinormal mode frequencies and their overtones. Our results show a non-trivial interplay between the cosmological constant and the regularization scale $a$, which imprints itself on both the light-ring structure and the quasinormal spectrum. These features suggest potential observational discriminants that could distinguish these regular spacetimes from their singular counterparts in future gravitational-wave and high-resolution electromagnetic observations.
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All authors G. Alencar, Albert Duran-Cabacés, A. Lima, Ángel Rincón, Diego Sáez-Chillón Gómez
Physics and Society
Climate change and human mobility will shape dengue emergence risk in Europe
Charley Presigny, Paolo Baglioni, Pietro Rotondo et al. (+3 more)
The risk of local arbovirus outbreaks in Europe is expected to increase due to
climate change, as suggested by the multiplication of arbovirus outbreaks in the last decades. Europe has historically been a non-endemic region, making it vital to pinpoint which populations are potentially exposed -and under which conditions- so we can build truly robust epidemic preparedness capabilities. We introduce an integrated, multi-scale model that fuses a mechanistic transmission engine with a vector abundance framework, all embedded in a mobility-driven metapopulation system capturing human, vector, and air-traffic movement. To this end, we combine
climate and population projections with mobility data to estimate and map dengue emergence risk in Europe throughout the 21st century. Additionally, we introduce a dedicated migration model that explores how
climate-driven population redistribution could alter these risk estimates.Assuming the
climate avoids major tipping points, model-derived risk indicators increase substantially under most emissions scenarios. While the spatio-temporal risk will remain largely driven by importation, our results indicate a gradual transition toward an environment-driven regime, particularly under the worst-case emissions scenario. To better anticipate and manage recurrent arbovirus outbreaks, our findings highlight the need to integrate mobility pathways and
climate-driven population redistribution into predictive models of vector-borne disease emergence in temperate regions.
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All authors Charley Presigny, Paolo Baglioni, Pietro Rotondo, Michele Allegra, Annalisa Barla, Manlio De Domenico
Quantum Physics
Shadow models of a quantum model for cloud cover and the influence of finite sampling noise
Hedwig Keller, Mierk Schwabe and Veronika Eyring
Quantum computing is a quickly growing field that is promising various advantages compared to conventional computing. However, currently stand-alone
quantum applications are scarce and hybrid (
quantum-classical) computing is needed, especially in
quantum machine learning (QML). Due to current limitations of
quantum computing hardware and the coupling between HPC and
quantum devices, integrating a trained (QML) model in classical applications is challenging. In this case, it is helpful to couple so-called shadows of the QML model instead, i.e., classical models that imitate the input-output relations of QML models such that
quantum resources are only needed during the training stage. Here we consider constructive shadowing processes without an explicit training or regression stage to avoid rendering the QML model redundant, and apply them to a previously developed QML model for cloud cover [1] to allow for an efficient coupling to a
climate model. We compare classical interpolation methods to an approximation of the
quantum Fourier model, the representation of the
circuit as a partial
Fourier series. The encoding strategy in [1] allows the use of the discrete
Fourier transform to efficiently reconstruct the
circuits classically. Truncating the partial
Fourier series further reduces the size of the shadow models. Both methods have the effect of mitigating finite sampling noise under certain conditions, which yields a motivation to use shadow models also beyond the era of limited hardware availability. Further, we compute the shadow models on the
quantum system Euro-Q-Exa, based on the IQM Radiance system with superconducting
qubits, where error mitigating effects can also be observed, albeit it is still difficult to distinguish them from errors connected to the calibration of the system.
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Chemical Physics
Nonzero-temperature vibronic spectra of polyatomic molecules from a zero-temperature classical trajectory
Davide Barbiero and Jiří J. L. Vaníček
By combining coherence thermofield dynamics with the single-Hessian approximation, we enable simulations of low- to medium-resolution vibronic spectra of weakly anharmonic systems at nonzero temperatures, at negligible additional cost relative to zero-temperature calculations. Single-Hessian coherence thermofield Gaussian wavepacket dynamics is exact in any harmonic potential, provided that the reference Hessian is that of the final surface. When applied to Morse systems of increasing anharmonicity and varying temperature, this method successfully captures excited-state anharmonicity and key temperature-dependent spectral features, including hot bands and broadening. By combining the method with on-the-fly ab initio dynamics, we demonstrate its utility by computing the absorption spectra of naphthalene, aminocoumarin C450, and phenyl radical, and the photoelectron spectrum of SeO$_{2}^{-}$ . Within the ab initio single-Hessian approximation, after the zero-temperature spectrum is obtained at the cost of classical molecular dynamics (on the order of hours), all nonzero-temperature spectra are computed in seconds.
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