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Monday 3 August

Earth and Planetary Astrophysics · Cross-listed from math.DS

Laskar's frequency map analysis revisited

Zhicheng Tong and Yong Li

In this paper, we establish the exponential convergence of Laskar's pioneering frequency map analysis, strictly improving upon classical polynomial bounds. By utilizing appropriately chosen weighting functions, we achieve such exponential rates in the analytic quasi-periodic regime for frequency vectors satisfying Diophantine or Brjuno nonresonance conditions. Furthermore, we extend the theoretical framework beyond the analytic quasi-periodic regime into the analytic almost periodic setting. By employing and generalizing Bourgain's framework, we accommodate a much broader class of anisotropic spatial structures. These results yield the first unified theory of exponential convergence for frequency map analysis, revealing the interplay among analyticity, spatial structures, nonresonance conditions, the choice of weighting functions, and convergence rates. This framework has important implications for applications in fields including celestial mechanics. Moreover, the novel techniques developed herein yield new insights into the study of weighted Birkhoff averages.
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Mathematical Physics

$q$-Deformed Topological Recursion: Quantum Curves and Non-perturbative Analysis

Fridolin Melong and Raimar Wulkenhaar

This work investigates the $q$-deformation of $(r,s)$-Airy structures and their realization via $q$-difference operators, providing a bridge between quantum spectral curves and integrable systems. We construct an all-order $q$-WKB solution for the matrix systems associated with the $q$-quantized curve $E_q(x,y)=0$. We demonstrate that the resulting non-perturbative connected $q$-amplitudes satisfy a set of shifted $q$-loop equations, which can be interpreted as the Ward identities of a $q$-deformed $\mathcal{W}(\mathfrak{gl}_r)$ algebra. Our main result provides a rigorous classification of admissible $(r,s,q)$ pairs and $q$-Casimir configurations that satisfy the $q$-topological type property. This ensures that the semi-classical expansion is uniquely governed by the $q$-topological recursion, offering new insights into the $q$-quantization of mirror curves and their underlying algebraic structures.
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Physics and Society

Microscopic dynamics of consensus formation in multi-agent LLM Naming Games

Cristiano De Nobili, Vijayasri Iyer, Alessandro Codello et al. (+1 more)

Decentralized populations of Large Language Model (LLM) agents can spontaneously reach consensus on shared conventions, yet the microscopic mechanisms by which their internal stochasticity shapes macroscopic ordering remain unexplored. We study a minimal LLM Naming Game in which the listener's decision is a single-token LLM call at decoding temperature $T$, replacing the inventory check of the deterministic Naming Game. Each interaction decomposes into an in-inventory and an out-inventory channel with conditional rates $\pi(T)\!\equiv\!P(\text{YES}\mid w\in P_j)$ and $\phi(T)\!\equiv\!P(\text{YES}\mid w\notin P_j)$, whose balance controls an ordering-disordering drift. A mean-field theory of the two-rate dynamics yields an analytical ordering condition that generalizes the consensus threshold of the stochastic Naming Game to a critical line in the $(\pi,\phi)$ plane. Across three open-weight architectures, consensus is always reached, but through three distinct listener regimes: permissive (repaint-noise dominated), near-deterministic, and conservative (missed-collapse dominated). The effective finite-size exponent $\beta(T)$ in $t_{\rm conv}\!\sim\!N^{\beta}$ shifts with temperature, and the temperature-sensitivity $\alpha$ in $t_c\!\sim\!e^{\alpha T}$ ranges from ${\approx}\,0.67$ to ${\approx}\,0$ across architectures. Decoding temperature thus emerges as an architecture-dependent control parameter for decentralized LLM populations, quantitatively characterized by the statistical-physics toolkit.
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All authors Cristiano De Nobili, Vijayasri Iyer, Alessandro Codello, Raffaella Burioni

Cosmology and Nongalactic Astrophysics

Testing Scale-Dependent Suppression of Structure Growth in the Linear Regime

Fernanda Oliveira, Miguel A. Sabogal, Felipe Avila et al. (+2 more)

We investigate recent reports of a suppression in the growth rate of cosmic structures inferred from analyses of the $[f\sigma_8](z)$ dataset. To address this issue, we explore the hypothesis that the evolution of matter clustering is more accurately described within the framework of scale-dependent modified gravity. We perform a joint analysis of $[f\sigma_8](z)$, cosmic chronometer $H(z)$ measurements, luminosity distance data, and CMB observations using Markov Chain Monte Carlo techniques to constrain the parameters of a scale-dependent cosmological model and investigate its impact on the evolution of $[f\sigma_8](z)$. Our results indicate that the suppression of the growth rate of large-scale structures is more pronounced during the matter-dominated era than in the dark-energy-dominated epoch. We find evidence for scale-dependent growth at a statistical significance of $2.2\, \sigma$. In addition, we constrain the $S_8$ parameter and find it to be consistent with the value inferred from the CMB observations of the Planck Collaboration. Overall, our analysis shows that $k$-dependent growth models provide a viable explanation for the observed clustering of matter without exacerbating the current cosmological tensions.
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All authors Fernanda Oliveira, Miguel A. Sabogal, Felipe Avila, Rafael C. Nunes, Armando Bernui

Earth and Planetary Astrophysics

Ammonium salt formation and abundance in protoplanetary disks

Maxime Ruaud, Jean-Christophe Loison and Uma Gorti

Ammonium salts may represent an important reservoir of volatile species in Solar system primitive bodies, but the question of how and when these salts can form during the star formation process remains unknown. In this paper, we use thermo-chemical models to study the formation of ammonium salts during the protoplanetary disk stage. We show that ammonium salts form efficiently in the inner disk midplane (i.e. $r \lesssim 50 $ au), inside the comet forming region. In this region, our model predicts that almost all the available nitrogen is in the form of salts (i.e. mainly in ammonium cyanate) at the surface of grains after evolving for 10 Myrs. For sulfur, we show that almost all the available S is in the form of ammonium hydrosulfide in the inner disk midplane. We show that inside $r\sim 30$ au, ammonium salt formation is enhanced by a cosmic-ray-driven sink effect that progressively converts gas-phase CO and N$_2$ into carbon dioxide and salts, respectively, at the surface of grains on a timescale $\gtrsim 1$ Myr. This impacts the location of the CO and N$_2$ radial snowlines which both shift closer to the star as a function of time.
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Optics

Generalized Temporal Coupled Mode Theory (g-TCMT) applied to Coupled Resonator Optical Waveguides with Exchange Symmetry (CROWe)

Tianrui Li, Matthew P. Halsall and Iain F. Crowe

In this paper, we extend our generalized Temporal Coupled Mode Theory (g-TCMT) model, developed earlier [1], from a simple, dual-coupled micro-ring resonator (MRR) system to higher-order, n-serially coupled MRRs. By treating each pair of adjacent MRRs as a single `equivalent resonator', we demonstrate excellent agreement in spectral resonance position, between the g-TCMT and numerical results obtained using the transfer matrix method (TMM), for systems up to and including order n=4. The validity of this approach hinges on the existence, or otherwise, of exchange symmetry, and so we refer to these structures as Coupled Resonator Optical Waveguides with exchange symmetry (CROWe's). We explore the limitations of our approach with illustrative examples of strongly coupled systems of order n \geq 5. Finally, we explore the properties of such higher order CROWe's for applications in non-Hermitian photonics, i.e., in which gain in some of the component MRRs and loss in the others leads to Parity-Time (PT) symmetry.
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Mesoscale and Nanoscale Physics

Charge Tunable Optical Nonlinearity of Moiré Exciton-Polaritons

Zhijie Li, Kok Wee Song, Jens-Christian Drawer et al. (+16 more)

Transition metal dichalcogenides represent a versatile platform to study strong light-matter interactions based on excitons and electrons in ordered lattices. Twist-engineering of moiré structures further enables the manipulation of the polaritonic nonlinearities via engineering the exciton landscape on the nanoscale. In this work, we demonstrate in-situ control of the optical saturation-based nonlinearity of moiré exciton-polaritons by phase space restriction via charge doping. Strong exciton-photon coupling is established in a gate-controllable MoTe$_2$-MoSe$_2$ heterobilayer, embedded in a spectrally-tunable open cavity. A small gate voltage can effectively lower the necessary polariton density by one order of magnitude to achieve a similar nonlinear saturation effect as in the charge-neutral case. Our microscopic description successfully explains the observed phenomena in the framework of Pauli blocking for the moiré superlattices with charge preoccupation.
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All authors Zhijie Li, Kok Wee Song, Jens-Christian Drawer, Vita Solovyeva, Martin Esmann, Niklas Nilius, Muhammad Sufyan Ramzan, Caterina Cocchi, Falk Eilenberger, Takashi Taniguchi, Kenji Watanabe, Atanu Patra, Subhamoy Sahoo, Simon Betzold, Sven Höfling, Alexander Högele, Oleksandr Kyriienko, Christian Schneider, Bo Han

High Energy Physics (Experiment)

Construction, commissioning, and performance of the ENUBET demonstrator

F. Acerbi, I. Angelis, L. Bomben et al. (+75 more)

A final full-size prototype of the instrumented decay tunnel of ENUBET, referred to as the Demonstrator, was constructed and its performance was tested during the 2022, 2023 and 2024 beam test campaigns at the CERN East Area facility. We demonstrate the full scalability of this specialized longitudinal sampling calorimeter technology, based on iron absorbers and scintillator tiles readout by wavelength-shifting fibers and SiPMs. In addition, we evaluate the channel-by- channel response and the performance in terms of electron energy resolution, linearity, and particle identification capabilities, using charged particle beams with energies up to 5 GeV. A comparison with the predictions of a GEANT4 simulation of the prototype is also presented. The achieved energy resolution ($\sim 17$% at 1 GeV and 10% at 3 GeV) fully satisfies the requirements for positron identification. The results meet the requirements for neutrino monitoring through lepton identification in the decay tunnel and validate the ENUBET full simulation. Although some limitations have been identified, they can be readily addressed in future developments.
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All authors F. Acerbi, I. Angelis, L. Bomben, M. Bonesini, F. Bramati, A. Branca, C. Brizzolari, G. Brunetti, G. T. Burton, S. Capelli, M. Capitani, S. Carturan, M. G. Catanesi, S. Cecchini, N. Charitonidis, F. Cindolo, J. Cogan, G. Cogo, G. Collazuol, D. D'Ago, F. Dal Corso, C. Delogu, G. De Rosa, S. Dolan, A. Falcone, M. Feltre, C. Forza, A. Gola, D. Guffanti, L. Halić, F. Iacob, C. Jollet, A. Kallitsopoulou, B. Kliček, Y. Kudenko, Ch. Lampoudis, M. Laveder, P. Legou, S. Levorato, A. Longhin, L. Ludovici, E. Lutsenko, L. Magaletti, G. Mandrioli, S. Marangoni, A. Margotti, V. Mascagna, M. Mattiazzi, N. Mauri, J. McElwee, L. Meazza, A. Meregaglia, M. Mezzetto, L. Munteanu, M. Pari, T. Papaevangelou, E. G. Parozzi, L. Pasqualini, G. Paternoster, L. Patrizii, M. Perrin-Terrin, M. Pozzato, M. Prest, F. Pupilli, E. Radicioni, A. C. Ruggeri, G. Saibene, D. Sampsonidis, C. Scian, L. Silvestrin, G. Sirri, M. Stipčević, M. Tenti, F. Terranova, M. Torti, S. E. Tzamarias, E. Vallazza, C. Vallée

Nuclear Experiment

Charm-quark collectivity from small to large systems with ALICE

Marcello Di Costanzo

In these proceedings, the elliptic flow ($v_2$) measurement of prompt charm hadrons in lead-lead (Pb-Pb) and oxygen-oxygen (OO) collisions at $\sqrt{s_{\mathrm{NN}}} = 5.36$ TeV, using the data collected during LHC Run 3 by the ALICE detector, is presented. The analysis is performed at midrapidity ($|y| < 0.8$) and hadronic decay channels are used to reconstruct the signal candidates. The $v_2$ coefficient is measured via the Scalar Product (SP) technique. The $v_2$ of prompt D$^0$, D$^+$, D$_\text{s}^+$ mesons, and $\Lambda_{\text{c}}^+$ baryons in semicentral Pb-Pb collisions is reported. These results achieve unprecedented precision and low-$p_{\text{T}}$ reach for the D mesons and highlight the first observation of the splitting of baryon and meson elliptic flow at intermediate $p_{\text{T}}$ in the charm sector. The prompt D-meson $v_2$ is also measured in peripheral Pb-Pb collisions and central OO collisions, probing the degree of thermal equilibration reached by charm quarks propagating in progressively smaller quark-gluon plasma media.
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Earth and Planetary Astrophysics

Dynamo generation reveals redox conditions during formation of differentiated planetesimals

Hannah R. Sanderson, James F. J. Bryson and Claire I. O. Nichols

In the early Solar System, an isotopic dichotomy existed between non-carbonaceous (NC) and carbonaceous (CC) planetesimals. Depending on the formation location of these planetesimals relative to condensation lines in the protoplanetary disk, NC and CC differentiated planetesimals could have had distinct redox states and water contents. However, the extent of these differences and the resulting accretion environments of NC and CC planetesimals are debated. Here, we use thermal evolution and dynamo generation models to explore the effect of planetesimal core size, a proxy for redox state, and mantle water content on planetesimal dynamo generation. We find that combinations of core size and water content consistent with different formation scenarios produce planetesimals with stark contrasts in both magnetic field strength and duration. By comparing our models to existing paleomagnetic data for NC planetesimals, we suggest these bodies formed with a small amount of water-ice and degassed efficiently during differentiation. Future paleomagnetic measurements could determine whether CC planetesimals degassed as efficiently as NC planetesimals and the number of planetesimal formation regions in the NC reservoir. Overall, we demonstrate that meteorite paleomagnetism combined with dynamo generation models provides novel insight into the accretion environments of planetesimals and the evolution of their water contents.
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Statistical Mechanics

Inhomogeneous Ising Model on 2D kagomé Lattice: Fermionic field approach

Shahane A. Khachatryan, Zhidong Zhang and Ara G. Sedrakyan

We investigate the two-dimensional inhomogeneous Ising model (2DIM) on the kagom'e lattice by mapping it onto a particular non-symmetric eight-vertex model and constructing the corresponding $R$-matrix. Using a fermionic representation, we evaluate the partition function and derive explicit expressions for the main thermodynamic quantities. In the thermodynamic limit, we obtain an exact equation for the critical surface determining the phase transition of the model. We also calculate the free energy, specific heat, and spontaneous magnetization in the ferromagnetic case. Furthermore, we show that when one or two coupling constants vanish, the model reduces, respectively, to the square-lattice and one-dimensional Ising models. In both limits, our results reproduce the corresponding exact critical couplings and free energies.
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Mesoscale and Nanoscale Physics

Band topology and symmetry-driven magneto-optical response in two-dimensional d-wave altermagnets with staggered spin-orbit coupling

Meysam Bagheri Tagani Carmine Autieri and Wojciech Brzezicki

Altermagnets combine compensated collinear magnetic order with momentum-dependent spin splitting, providing a route to transverse electronic and optical responses without a net ferromagnetic moment. We develop a strictly periodic four-band tight-binding model for a two-dimensional d-wave altermagnet and distinguish the roles of three spin orbit coupling (SOC) channels: uniform Rashba SOC, a sublattice-staggered Rashba interaction, and bond-staggered SOC. In the absence of SOC, the d-wave kinetic anisotropy produces spin-polarized Dirac points on orthogonal Brillouin-zone boundaries, related by the altermagnetic fourfold spin-group symmetry. Uniform Rashba SOC mixes the spin sectors and shifts these nodes but preserves the antiunitary symmetry that forbids an integrated Hall response. The sublattice-staggered Rashba term breaks this symmetry and activates transverse optical response, whereas the bond-staggered SOC provides the mass that gaps the boundary nodes. Their combined action generates strong Berry-curvature hot spots and, within a narrow parameter window, an isolated lower two-band manifold with Chern number C=-2. For the representative parameters considered here it is possible to stabilize a Chern insulator phase. Using covariant-velocity Kubo calculations, we show that large optical Hall conductivity and circular dichroism extend well beyond the nonzero-Chern region and are controlled by SOC-induced avoided crossings and symmetry breaking. We further find that carrier doping strongly modifies the resonant and dc Hall responses through Pauli blocking and the occupation of Berry-curvature hot spots, enabling gate-controlled sign reversals. These results identify the complementary roles of distinct interfacial SOC mechanisms in producing topology and tunable magneto-optical activity in compensated two-dimensional magnets.
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Mesoscale and Nanoscale Physics

Time reversal symmetry broken quantum spin hall effect in pseudospin-1 Dirac-Rashba system

Puspita Parui and Bheema Lingam Chittari

The Quantum spin Hall (QSH) phase is conventionally understood to be protected by time-reversal symmetry (TRS). Here, we theoretically investigated the fate of the QSH phase in a pseudospin-1 fermionic $\alpha-\mathcal{T}_3$ system in the presence of a TRS-breaking ferromagnetic exchange field and spin-nonconserving Rashba spin-orbit coupling. Despite broken TRS, the QSH phase survives over a finite parameter regime and is characterised by a non-zero projected spin-Chern number $C_\sigma (\sigma = \uparrow, \downarrow)$, protected by a spin-spectral gap. In the absence of Rashba coupling, the QSH phase remains robust up to an $\alpha$-dependent critical exchange field. Rashba SOC qualitatively reshapes the phase diagram by driving transitions into two distinct quantum anomalous Hall (QAH) phases: a $C=2$ phase, irrespective of $\alpha$-values, and a $C=1$ phase for $\alpha \neq 0,1$, which is further identified as a valley-polarized QAH phase arising from a single valley. Rotating the magnetization to in-plane gaps out the first-order helical edge states and gives rise to second-order topological insulator (SOTI) phases that host localized corner states in suitable finite geometry. We further identify a topological phase transition between two different SOTI phases, mediated by nanoribbon edge states at an exchange field equal to $\alpha$. These results establish spin-resolved topology in a higher pseudospin system as well as the $\alpha-\mathcal{T}_3$ lattice as a versatile platform for engineering and controlling multiple topological phases through magnetic exchange and spin-orbit coupling.
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Mesoscale and Nanoscale Physics

Complete Structural Determination of Mesostructural Dodecagonal Quasicrystalline Particles

Xueliang Zhang, Xi Wang, Nobuhisa Fujita et al. (+2 more)

Quasicrystals have revolutionized our understanding of order in solids by demonstrating exotic structural and physicochemical properties with diverse potential applications. Despite the development of various theoretical models and experimental techniques to describe quasicrystal structures, the precise determination of local three dimensional (3D) arrangements of constituent atoms, or of secondary building units such as clusters or micelles, remains elusive. This challenge is particularly acute in self assembled soft matter quasicrystalline systems, where the complex assembly of molecular groups introduces additional defects and structural modulations. Herein, we report the first complete structural determination of self-assembled mesostructural dodecagonal quasicrystalline particles. Employing advanced electron tomography, combined with dedicated structural tracing and processing workflows, the 3D coordinates of all nodal sites were extracted. This approach reveals that the actual structure deviates from the conventionally assumed tetrahedral close packing geometry, exhibiting diverse coordination environments and displacive fluctuations. We identified and quantified rotational intergrowths arising from node exchange, as well as various defects and disorder, with these features discernible only through 3D analysis. Additionally, we propose a simplified two-layer stacking of isomorphic hexagonal model to form dodecagonal quasicrystal. This work advances our understanding of soft-matter dodecagonal quasicrystals and paves the way for detailed structural elucidation of self-assembled systems.
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All authors Xueliang Zhang, Xi Wang, Nobuhisa Fujita, Osamu Terasaki, Lu Han

Medical Physics

Cardiovascular Digital Twins from Physics Based to Data Driven Approaches

Emmanuel Lwele and Francis Chikweto

Cardiovascular digital twins aim to create patient-specific computational models that evolve with clinical data to support diagnosis, prognosis, and therapy optimisation. Mechanistic models provide physiological interpretability but remain computationally demanding, whereas data-driven approaches improve scalability yet risk limited robustness. Emerging physics-informed, graph-based, and hybrid methods integrate physical constraints with relational learning across vascular networks. We review modelling paradigms, data assimilation frameworks, validation challenges, and translational pathways toward clinically deployable cardiovascular digital twins.
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Other Condensed Matter

Coherent migration of the single excitation injected into finite-length segment of the biomolecular chain

D. Chevizovich, V. Matic, Z. Przulj et al. (+1 more)

We study the migration of a single excitation excited at a structural element of a finite molecular segment, which is a part of a long biomolecular chain. The excitation cannot leave the segment and is locally coupled to thermal vibrations of the lattice, forming a self-trapped state corresponding to a nonadiabatic polaron. The time-dependent probability distribution of finding the excitation at the nodes of the segment is calculated, with particular emphasis on the role of the initial excitation position. A formal analogy is observed between the present model and continuous-time quantum walk models on finite chains with reflecting boundaries. The results reveal an asymmetry in the probability distribution for nodes symmetrically positioned with respect to the initially excited site, which arises solely from the asymmetric placement of the initial excitation within the finite segment. The only exception occurs when the initially excited node is located at the center of the segment, where the probability distribution becomes symmetric. The complex interference pattern and the absence of well-defined revivals stem from the non-equidistant spectrum of mode frequencies, leading to progressive dephasing of the constituent modes. As a result, the initially well-localized probability maximum fragments into one dominant maximum accompanied by several secondary maxima of lower intensity. These findings highlight the importance of boundary conditions and initial-state geometry in controlling quantum transport in finite molecular systems.
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All authors D. Chevizovich, V. Matic, Z. Przulj, S. Galovic

Quantum Physics

Unconditionally successful quantum Time-Marching algorithm via LCU for nonlinear Burgers equation

Niccolo Fonio, Giuseppe Di Molfetta and Pierre Sagaut

Most recently proposed quantum algorithms for solving linear and nonlinear partial differential equations rely on non-unitary operations. These operations are typically implemented probabilistically, requiring postselection and thus increasing the computational cost. We show that quantum lattice gas algorithms enable unconditionally successful quantum simulation of nonlinearities, yielding, to our knowledge, the first quantum algorithm for Burgers equation whose time steps can be concatenated without probabilistic failure. The key idea is to exploit the correspondence between the stochasticity of quantum measurement in the linear combination of unitaries framework and the intrinsic randomness of the classical lattice gas algorithm. In doing so, we identify general properties that characterize probabilistic classical algorithms amenable to this time-marching formulation, and illustrate the approach with an additional application.
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Plasma Physics

Hybrid Kinetic-MHD Simulations of Drift-Orbit Effects on the Stability and Non-Linear Dynamics of Runaway Electron Beams

Shi-Jie Liu, Hao-Wei Zhang, Hannes Bergstroem et al. (+2 more)

During tokamak disruptions, the Ohmic current may be replaced by a non-inductive runaway electron (RE) current, affecting resistive stability. Previous studies suggest that, in the linear phase, the presence of REs acts destabilizing for tearing modes (TM) compared to a scenario with Ohmic current. In the non-linear regime, this translates to larger saturation amplitudes. These results are based on the assumption of zero drift-orbit deviation from the magnetic flux surfaces corresponding to the low-energy limit. This work investigates the importance of this kinetic effect by studying the linear and non-linear TM dynamics in RE beams with different RE energies, providing a clear picture of finite-orbit-width (FOW) effects. We use a hybrid fluid-kinetic model in the 3D non-linear magnetohydrodynamic (MHD) code JOREK, treating REs kinetically with a full-f Monte Carlo approach in self-consistent interaction with the MHD mode dynamics. The study shows that the presence of REs modifies the characteristics of the instability in several ways. First, we find that the major-radial displacement of drift orbits from flux surfaces induces an $m=1$ perturbation to the equilibrium current, introducing additional mode coupling between $(m,n)$ instabilities and the $(m\pm1,n)$ sidebands. Second, we find that increasing RE energy has a stabilizing effect on the MHD modes because REs cannot support narrow current sheets on rational flux surfaces owing to the drift-orbit displacement. This counteracts the destabilizing effect that REs have on TMs in the low-energy limit. For the scenario investigated, the stabilizing effect dominates over the additional mode coupling, reducing the development of stochastic magnetic regions with increasing RE energy and thereby lowering radial particle transport. Overall, we find that FOW effects can substantially alter the MHD stability and non-linear dynamics of RE beams.
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All authors Shi-Jie Liu, Hao-Wei Zhang, Hannes Bergstroem, Matthias Hoelzl, the JOREK Team

Materials Science · Cross-listed from math.DG

The Primitive and Diamond surfaces locally minimize the variance of Gauss curvature

Hao Chen

We prove that the Schwarz' Primitive (P) and Diamond (D) surfaces are local minimizers of the variance of Gaussian curvature among local deformations within the moduli space of triply periodic minimal surfaces of genus 3 (TPMSg3s). Our approach interprets the branch values of the Gauss map as a configuration of eight points on the sphere and expresses the variance of Gaussian curvature as the product of two integrals involving exponentials of Green's functions. We then show that the Hessian of this functional is positive definite at the cubic configuration when restricted to antipodal deformations, thereby establishing the local minimality of the P and D surfaces. Along the other deformation directions, the Hessian is positive definite except for a two-dimensional eigenspace with slightly negative eigenvalues, leaving promising hope that the Gyroid is also a local minimizer.
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Quantum Physics

Better accuracy with fewer qubits: Single-particle basis set optimization for quantum chemistry on quantum computers

Subimal Deb and V. S. Prasannaa

In spite of recent advances, quantum computers are expected to be sufficiently noisy in the coming few years to the extent of limiting quantum chemical calculations to relatively small number of orbitals. However, even with reasonable quality single particle basis sets, small active spaces with limited orbitals can result in a significant fraction of correlation energy being lost, motivating the design of moderate quality qubit-efficient basis sets for quantum algorithms. We begin by reoptimizing the existing minimal basis sets using a genetic algorithm-inspired approach in conjunction with aggressive refinement strategies, and generate modified minimal basis sets (MSTO-kG basis; k = 2-11) for atoms from H through F. The ground state energies of H through F using our MSTO bases at FCI level of theory yield ground state energies that are comparable or sometimes even lower than those obtained using 6-31G basis sets. In the case of Li, the MSTO bases surpass the performance of cc-pVQZ bases. Thus, we obtain better atomic energies with same number of qubits relative to STO bases, and better/comparable energies with fewer qubits relative to higher quality bases. In the case of molecules, H2 performs poorly; a finding that is consistent with an earlier work in literature. For other molecules, Li2, C2, LiH, BeH and BeH2, the FCI results (except C2 for which we employ CISD) from our bases are comparable to/outperform those from 6-31G basis. Finally, we compare the resources required between different bases and find that MSTO bases yield better energies than the competing basis sets while incurring fewer qubits and two-qubit gates with VQE, QPE, and HHL. The logical T-gate counts are also found to be considerably lower for QPE and HHL respectively. Overall, our work paves way for more accurate yet less qubit-hungry quantum chemical calculations using near-term quantum computers.
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Instrumentation and Methods for Astrophysics

Pollux UV & FUV polarimeters: first lab results

Adrien Girardot, Ninon Demelier, Coralie Neiner et al. (+6 more)

Pollux is a high-resolution spectropolarimeter proposed by a European consortium for the Habitable Worlds Observatory (HWO). Its design covers a broad spectral range from the far-ultraviolet (FUV) to the near-infrared (97-1\,750 nm), with polarimetric channels relying on \ch{MgF2} birefringent optics in the mid- and near-UV (MUV-NUV), and on an innovative all-reflective polarimeter in the FUV, where no birefringent material is available. To validate these polarimeters, whose required polarimetric precision is $10^{-3}$, a dedicated vacuum ultraviolet test bench has been developed, with two configurations: one for the MUV-NUV range (120-290 nm) and one for the FUV range (98-120 nm). We present the first laboratory results obtained with this bench. On the MUV-NUV configuration, the full optical chain has been integrated: a first polarised spectrum of the deuterium lamp was acquired, the polarisation generation subsystem was validated against Mueller matrix predictions, and a first end-to-end polarimetric measurement was performed. On the FUV configuration, the windowless deuterium plasma source has been characterised, the alignment strategy of the K-mirror modulator has been implemented, and the mirror-based analyser has been manufactured and tested, showing a polarisation extinction ratio of 10 at 120 nm. These results demonstrate the operation of the bench and pave the way for the characterisation of the polarimetric precision of the Pollux polarimeters, increasing the Technology Readiness Level of UV spectropolarimetry for HWO.
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All authors Adrien Girardot, Ninon Demelier, Coralie Neiner, Jean-Michel Reess, Juan Ignacio Larruquert, Paloma Lopez-Reyes, Anejandro Garcia Canas, Nuria Gutierrez Luna, Ana Iglesias Moreno

Materials Science

Transient Ferromagnetism in Ultrafast Phase Transitions in Perovskites under XUV Irradiation: A Comparative Study of SrTiO3 and KTaO3

Aldo Artimez Pena and Nikita Medvedev

We study ultrafast structural and electronic responses of strontium titanate and potassium tantalate to intense femtosecond irradiation using the XTANT3 multiscale code. It is found that at threshold doses of 0.7 eVatom in STO and 0.9 eVatom in KTO, a superionic state thermally forms with selective melting of the oxygen subsystem while metallic sublattices remain ordered. This state persists up to 1.6 eVatom STO and 1.5 eVatom KTO, above which complete disorder occurs. Analysis of the transient electronic density of states suggests that the B site d orbitals govern the divergent behaviour of the two materials: the compact Ti 3d orbitals in STO produce a narrow conduction band and large intraatomic exchange parameter, driving a transient ferromagnetic instability on 1 ps timescales, whereas the more spatially extended Ta 5d orbitals in KTO yield a broader conduction band and smaller exchange parameter, keeping KTO paramagnetic. These results suggest d orbital spatial extent as a structural parameter that influences phase transition sequences, and magnetic response under extreme electronic excitation, with implications for the ultrafast optical control of electronic and magnetic properties in perovskite based optoelectronic devices. Landau Devonshire analysis shows that irradiation at 0.3 eVatom transiently deepens the polar potential well in unstrained and strained STO and KTO, with the effect amplified approximately 2 fold in strained STO and 6 fold in strained KTO with respect to the unstrained cases.
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Optics

Deep Inverse-Designed Nanophotonic Processors with Structural Nonlinearity from Repeated Phase Encoding

Azka Maula Iskandar Muda and Uğur Teğin

Passive nanophotonic scattering regions implement linear optical transformations, and cascading input-independent regions alone does not create functional depth because the resulting transformations collapse into a single linear operator. Here, we introduce repeated phase encoding between inverse-designed passive transformations to generate an input-conditioned multilayer optical map without interlayer photodetection. Each re-encoding introduces additional phase-dependent optical pathways, producing structural nonlinearity with respect to the encoded variables while every scattering region remains passive and linear in the optical field. Under a controlled MNIST depth sweep, classification accuracy increases from 83.53% with one layer to 93.61% with seven layers, whereas the input-independent passive control saturates at 86.34%. The depth trend also persists in a time-multiplexed CIFAR-10 patch model. We further realize three jointly trained $16\times16$ transformations, each independently implemented as an inverse-designed nanophotonic region, with relative complex transmission errors of 7.63%, 7.59%, and 8.80%. The reconstructed electromagnetic stack reaches 91.79% accuracy after phase calibration, compared with 91.95% for its surrogate model. These results establish repeated input encoding as a route to functional depth in compact inverse-designed nanophotonic processors.
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Quantum Physics

Field-Free Transverse Aharonov–Bohm Phase Gate for an Orbital $l$-Qubit

Ju Gao and Fang Shen

The Aharonov–Bohm (AB) effect is usually read out through phase differences associated with spatially distinct electron paths. We show that confined orbital modes provide a same-path alternative: a core-confined magnetic flux writes opposite propagation phases on the co-propagating modes $|\pm l\rangle$ of a straight annular electron guide while the transported electron-wave support remains field free. In a spin-resolved Dirac treatment, the phase is carried by the overlap of the field-free vector potential $A_\phi$ with the mode's azimuthal conserved-current texture. The spin-dependent radial-gradient current becomes a boundary term that cancels when the complete finite-wall evanescent tail is retained, leaving the spin-independent orbital phase $\Delta\phi_{ln}\propto l\Phi L_{\rm int}\langle\rho^{-2}\rangle_{ln}/v_z$. The matched $|\pm l\rangle$ modes therefore realize a same-path $R_z(2\delta_l)$ gate, with differential internal-mode readout and common-mode phase rejection. For $a=75\,\mathrm{nm}$, $R=95\,\mathrm{nm}$, $L_{\rm int}=1\,\mathrm{mm}$, $E_z=10\,\mathrm{meV}$, and $|l|=10$, the gate angle is $2.315\,\mathrm{rad/G}$ and $R_z(\pi)$ occurs at $1.357\,\mathrm{G}$. Finite-barrier, mode-spacing, disorder-mismatch, and readout-visibility checks quantify the main implementation constraints. More broadly, the result connects a mode-resolved AB energy shift to a measurable propagation operation and shows how the spatially distributed conserved current of a Dirac wave can become an operational quantum-control resource.
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Quantum Physics

Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits

Fabrizio Berritta, David Pahl, Lukas Pahl et al. (+15 more)

Parasitic two-level-system (TLS) defects are a major source of energy relaxation and temporal instability in superconducting quantum processors. Our sub-second adaptive spectroscopy reveals telegraphic switching of TLSs with a characteristic timescale of a few seconds and spectral diffusion with diffusivity $D \approx 0.9~\mathrm{MHz}^2/\mathrm{s}$. These timescales are about $3 \times 10^2$ times faster than what is observed in conventional nonadaptive spectroscopy, which typically requires hours of measurement time. We resolve such fast dynamics on a field-programmable gate array (FPGA)-based controller that enables measurement of frequency- and time-resolved relaxations with sub-second temporal resolution in flux-tunable superconducting qubits. We observe similar defect dynamics across multiple qubits in independently fabricated devices measured in different laboratories. We correlate TLS-induced fluctuations with gate-level errors using randomized benchmarking. Our results reveal a previously inaccessible regime of frequency-resolved TLS dynamics and redefine the timescales relevant to TLS-aware characterization and calibration of superconducting quantum processors.
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All authors Fabrizio Berritta, David Pahl, Lukas Pahl, William P. Banner, Gabriel Cutter, Jan A. Krzywda, Spencer Weeden, Shravan Patel, Paul Buttles, Stanislav Eilhart, Michael Gingras, Bethany M. Niedzielski, Robert McDermott, Mollie E. Schwartz, Kyle Serniak, Max Hays, Jeffrey A. Grover, William D. Oliver

Atmospheric and Oceanic Physics

Crucial role of subsurface ocean variability in tropical cyclone genesis

Cong Gao, Lei Zhou, I.-I. Lin et al. (+4 more)

The upper ocean provides thermal energy to tropical cyclones. However, the impacts of the subsurface ocean on tropical cyclogenesis have been largely overlooked. Here, we show that the subsurface variabilities associated with the variation in the 26 {\deg}C isothermal depth have pronounced impacts on tropical cyclogenesis over global oceans. The sea surface wind stress and its curl before tropical cyclogenesis are large enough to perturb the ocean interior down to more than one hundred meters due to entrainment and upwelling. The 26 {\deg}C isothermal depth can fluctuate by tens of meters to significantly modify the upper ocean heat content. Consequently, sea surface temperature anomalies under nascent tropical cyclones are induced, and tropical cyclogenesis is modulated. Our results substantiate an unexpected relation between ocean interior variations and tropical cyclogenesis.
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All authors Cong Gao, Lei Zhou, I.-I. Lin, Chunzai Wang, Shoude Guan, Fei-Fei Jin, Raghu Murtugudde

Classical Physics

Wave Scattering at temporal interfaces with spatial-translation-symmetry mismatch

Cong Chen, Kaijun Yi, Guoliang Huang et al. (+1 more)

Temporal interfaces enable wave manipulation through broken time-translation symmetry, but conventional formulations generally assume that spatial-translation symmetry is preserved across the interface. Here we consider temporal interfaces between periodic media with mismatched spatial symmetries. It is discovered that the reciprocal-lattice vectors of the pre- and post-switching media enter a generalized quasi-momentum-matching condition, giving rise to reciprocal-lattice-assisted wave-vector conversion. We then develop a multichannel temporal-scattering theory and validate it in one- and two-dimensional elastic lattices. A single incident Bloch mode can thereby excite multiple post-interface Bloch modes with distinct wave vectors and frequencies, a response inaccessible at conventional temporal interfaces. These results establish symmetry mismatch as a new degree of freedom for simultaneous control of wave vector and frequency in time-modulated periodic media.
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All authors Cong Chen, Kaijun Yi, Guoliang Huang, Gengkai Hu

Quantum Physics

Efficient re-sampling in quasi-probability decompositions

Sara Santos, Stefan Woerner, Vincenzo Savona et al. (+1 more)

Near-term quantum devices are limited by noise and hardware constraints, motivating algorithmic approaches that trade circuit complexity for increased sampling overhead. Quasi-probability decompositions (QPDs), for example, allow replacing non-local operations by multiple circuits with local operations, but the associated sampling overhead generally scales exponentially and limits their practicality. In this work, we introduce a reweighting strategy for QPDs for circuits with the same variational structure across parameter settings, reusing samples and thereby reducing the sampling overhead. We first demonstrate this approach by estimating fidelities between parameterized quantum states, a key primitive in variational time evolution and quantum kernel methods. Importantly, this setup allows controlling the exponential QPD sampling overhead while preserving the structure of the state-encoding ansatz. We then apply the method to estimate the real part of the quantum geometric tensor using the simultaneous perturbation stochastic approximation and find that, in the presence of realistic hardware noise, our method outperforms other standard estimation techniques. These results highlight the potential of reweighting strategies to extend the applicability of QPD-based methods in variational quantum algorithms.
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All authors Sara Santos, Stefan Woerner, Vincenzo Savona, Julien Gacon

High Energy Astrophysical Phenomena

Accretion-induced spin-up: Implications for mass constraints of AMXPs

Xiaoyu Lai

We investigate the influence of the global structure of accreting millisecond X-ray pulsars (AMXPs) on accretion-induced spin-up, using three equations of state (EoS) models representing neutron stars, quark stars, and strangeon stars. By applying the classical accretion torque formalism, and deriving the accretion rate and magnetic field from observations of three AMXPs — XTE J1751-305, SAX J1808.4-3658, and IGR J00291+5934 — we derive mass contours in the plane of luminosity versus spin-up rate. Our results show that the inferred masses are broadly consistent across the three EoS models, indicating that the method is insensitive to the specific EoS and can serve as an evolutionary channel for constraining the masses of pulsar-like compact stars. Notably, we find that SAX J1808.4-3658 and IGR J00291+5934 are constrained to very low masses, while XTE J1751-305 yields a mass consistent with the typical range for pulsars. Our analysis suggests that future improvements in distance and spin-up measurements would refine these mass constraints, which could offer crucial evidence to distinguish different EoS models. This paper also presents the idea that using EoS-specific parameters could yield new insights.
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Quantum Physics

Characterizing the nitrogen-vacancy center singlet transition and its phonon sideband for absorption-based room-temperature magnetometry

Tobias Probst, Florian Schall, Sebastian Heuft et al. (+9 more)

Magnetometry with nitrogen-vacancy (NV) centers in diamond has shown great promise in recent years. In particular, absorption-based magnetometry techniques, employing a cavity to enhance the absorption length, can improve the contrast and sensitivity compared to conventional techniques based on reading out the NV$^-$ triplet fluorescence. The absorption techniques rely on magnetic-field-dependent absorption at the NV$^-$ singlet zero phonon line at 1042$\,$nm and its phonon sideband. In a cavity-enhanced spectroscopy approach, we study pump-laser- and microwave-induced cavity signal changes at room temperature over a spectral range of 680-1050$\,$nm. Through normalization, we eliminate the cavity-enhancement effect and provide quasi-single-pass values for the absorption and optically detected magnetic resonance (ODMR) contrast. The highest contrast is found at 1042$\,$nm, but multiple points of high contrast are found at the peaks of the phonon sideband. Additionally, cavity-enhanced ODMR contrasts in the range of 50-80$\,\%$ are presented. We further measure the broadband singlet absorption cross section at room temperature with a novel method through microwave-induced signal changes. This method is insensitive to pump-laser-induced signal changes by other defects and quantifies the room-temperature absorption strength of the singlet transition and its entire phonon sideband. We determine the absorption cross section at 1042$\,$nm to be $\sigma^{\,\bigstar}_{1042}=(0.89\pm0.14)\cdot 10^{-21}\,\text{m}^2$ or $\sigma^{\,\blacktriangle}_{1042}=(2.9\pm0.5)\cdot 10^{-21}\,\text{m}^2$. depending on the employed 532$\,$nm NV$^-$ absorption cross section.
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All authors Tobias Probst, Florian Schall, Sebastian Heuft, Janina J. Schindler, Lukas Lindner, Sven Mägdefessel, Rüdiger Quay, Philipp Reineck, Alexander M. Zaitsev, Takeshi Ohshima, Matthias Weidemüller, Jan Jeske