Biological Physics
Multiflagellarity facilitates bacterial upstream motility
Ran Tao, Nathaniel C. Esteves, Wanho Lee et al. (+8 more)
Upstream swimming drives bacterial spreading and surface colonization. Many pathogens encounter fluid flows as they infect the intestines, lungs, and urinary tract, so how bacteria use their flagella to counter these flows matters for disease and treatment. Yet how morphology and flagellar arrangement govern motility against flow remains unknown. Here, we investigate the biophysical determinants of rheotaxis by combining microfluidics, directed
evolution, genetics, holography, and hydrodynamics simulations. Using upstream swimming competitions, we find that peritrichous E. coli and S. enterica rapidly outcompete monotrichous P. aeruginosa and V. cholerae, accumulating upstream at densities up to five orders of magnitude higher, even though Vibrio swims three times as fast. Motility selection experiments show that rheotaxis increases with flagellar number and length, confirmed by overexpressing the master regulator flhD/C. Three-dimensional holography and single-
cell tracking reveal that multiflagellarity stabilizes surface residence and promotes the weathervane effect that reorients
cells upstream, a mechanism further supported by simulations that fully resolve flagellar arrangement and fluid-structure interactions. These results establish multiflagellarity as a key facilitator of upstream
navigation, governed by near-wall residence and shear-driven reorientation rather than by swimming speed.
Read the full abstract ▾
All authors Ran Tao, Nathaniel C. Esteves, Wanho Lee, Lauren Altman, Liuni Chen, David Gao, Ling Li, Yongsam Kim, Jun Zhu, Sookkyung Lim, Arnold J. T. M. Mathijssen
Chaotic Dynamics
Decision-Related Cognitive Signatures from Fast-Slow Dynamics: A Low-Dimensional Observation-Operator Framework
Furkan Emre Isik and Ali Demirci
Repeated decisions exhibit temporal structures such as persistence, direction-dependent switching, recurrent alternation, and abrupt transitions. We examine the generative sufficiency of a two-dimensional fast-slow dynamical system. The system combines a cubic fast equation with linear slow feedback and is analyzed through its
equilibrium geometry, trace-determinant structure,
equilibrium-fold loci, candidate
Hopf boundaries, and singular critical
manifold. An explicit observation operator projects continuous trajectories to a scalar signal and applies a binary readout, separating latent state-space dynamics from observable behavior. The analysis establishes a unique-
equilibrium regime and, for suitable parameters, a three-
equilibrium wedge with a central saddle. The outer
equilibria are attracting only where their traces are negative. The analysis also identifies the simple-zero condition required for ordinary saddle-nodes, trace-zero positive-determinant spectral boundaries compatible with oscillatory instability, and the attracting and repelling branches of the critical
manifold. Prescribed nonautonomous sweeps numerically illustrate direction-dependent switching (T1), transient episodic recurrent switching (T2), and an abrupt localized regime shift (T3). The attracting-
equilibrium regime associated with prolonged state retention (T4) is characterized analytically. The resulting correspondence is intended as a test of generative sufficiency at the level of observable temporal organization, rather than as an identification or empirical validation of latent cognitive mechanisms.
Read the full abstract ▾
General Relativity and Quantum Cosmology
Curvture Regularization and Dynamical Vacuum Structure in Pseudo-Complex General Relativity
Fridolin Weber, Peter Otto Hess and Cesar Augusto Zen Vasconcellos
Whether classical spacetime remains welldefined at arbitrarily high
curvature is a central question. In general relativity, singularities signal the breakdown of the classical description, motivating modifications of spacetime's short-distance structure. Pseudocomplex general relativity (pcGR) extends spacetime geometry to pseudo-complex coordinates, naturally introducing two metric sectors, the physical metric g{\mu}{\nu} and an auxiliary field f{\mu}{\nu}. The magnitude of the pseudo imaginary component defines the invariant acceleration scale a0, a direct consequence of the pseudo-complex structure. The simultaneity condition, requiring both idempotent sectors to satisfy the pseudo-complex Einstein equations independently, fixes the auxiliary field algebraically, with no new propagating degrees of freedom, and sets a lower bound on the lapse that regularizes
curvature. The regularization is achieved through the combined effect of the lapse-gap condition e{\nu}(r) gt. a0, which ensures the radial metric component remains nondegenerate, together with the regularity conditions at the areal-radius origin, B(0) = 1 and B'(0) = 0, which emerge naturally from the pseudo-complex geometry. These conditions jointly eliminate the Schwarzschildtype
curvature divergence, rather than the gap condition acting alone.
Read the full abstract ▾
Soft Condensed Matter
Dynamically triggered snap-through
Gregory Kozyreff, Lucie Domino, Basile Radisson et al. (+1 more)
Snap-through is a sudden and large mechanical deformation that is usually triggered by driving a control parameter beyond a bifurcation threshold. Here, we study a buckled strip that undergoes a saddle-node bifurcation as one of its clamps is rotated. We show experimentally, theoretically, and numerically that the effective snapping threshold can be markedly lowered by speeding up the rotation. For actuation times that are short but nevertheless longer than the fundamental flexural period, the strip is observed to remain close to the instantaneous quasi-static
equilibrium for most of the loading process. This allows us to derive an energetic criterion that accurately estimates a dynamic instability threshold well below the saddle-node bifurcation point. On the other hand, very near the bifurcation point, the
evolution of the quasi-static
equilibrium undergoes a
geometric boost, which entrains the general motion of the beam. As a result, a slower actuation of the clamp than predicted by the energy argument suffices to produce snap-through. A distinct scaling is derived in that limit, based on the aforementioned boost and critical slowing down of the least stable vibration mode of the beam. More broadly, our results show how finite-rate forcing can trigger snap-through before the quasi-static instability threshold is reached
Read the full abstract ▾
All authors Gregory Kozyreff, Lucie Domino, Basile Radisson, Hadrien Bense
Astrophysics of Galaxies
Common Excitation Patterns of Star Formation, Active Galactic Nuclei, and Shocks in Seyfert Galaxies
Peixin Zhu, Lisa J. Kewley, Dominika Ł. Król et al. (+6 more)
The growth of
galaxies and their central supermassive black holes is closely connected, yet the net effect of active
galactic nuclei (AGN) feedback on host-
galaxy star formation remains uncertain. AGN may enhance, suppress, or have little measurable impact on
star formation, but distinguishing among these outcomes requires separating
star-formation and AGN photoionization from shock excitation, which is expected in AGN-driven
outflows but has been difficult to isolate. Here we apply a recently developed theoretical three-dimensional diagnostic diagram, designed to separate
star formation, AGN, and shock excitation, to VLT/MUSE IFU observations of nine nearby (z < 0.026) Type 2 Seyfert
galaxies. We find a common excitation pattern across the sample:
star-forming rings or arcs at projected radii of r~0.8-6 kpc, AGN-photoionized bicones extending to kpc scales, central fast-shock-dominated regions that often extend perpendicular to the AGN bicone, and pure-shock- dominated regions surrounding the central fast shocks and appearing locally within the
star-forming rings. Deep Chandra X-ray morphology independently supports this decomposition. The circumnuclear
star-forming rings are consistent with bar-driven resonances, although positive AGN feedback may also contribute. The central fast shocks are broadly consistent with AGN jet-ISM interactions, while AGN wind-ISM interactions may also play an important role in
galaxies with low-power jets. These results establish central shocks as a common feature of Seyfert
galaxies and demonstrate the importance of accounting for shock excitation in AGN feedback studies.
Read the full abstract ▾
All authors Peixin Zhu, Lisa J. Kewley, Dominika Ł. Król, Giuseppina Fabbiano, Lars Hernquist, Ralph S. Sutherland, Anna Trindade Falcão, Martin Elvis, Riccardo Middei
Mathematical Physics
Sharp decay thresholds for eigenvalues of discrete Schrödinger operators on $\mathbb{Z}^2$
Shirshendu Ganguly and Wencai Liu
We study
eigenvalues of discrete Schrödinger operators $H=\Delta+V$ on $\mathbb{Z}^2$, where $\Delta$ is the uncentered
Laplacian, i.e., the un-normalized adjacency operator of $\mathbb{Z}^2$ and $V$ decays at infinity. By Weyl's
theorem, the essential spectrum of $H$ is $[-4,4]$. We determine the sharp decay thresholds for existence of
eigenvalues in three distinct spectral regimes. While it is natural to expect different behavior at the spectral edge $\lambda=\pm4$, and the bulk, there is a further distinction between the regular energies $0<|\lambda|<4$ and the interior critical energy $\lambda=0$ stemming from the reducibility of the corresponding
Fermi surface in the latter case. For every $0<|\lambda|<4$, we construct potentials $V$ satisfying $|V(n)|\leq C|n|^{-1}$ for which $\lambda$ is an
eigenvalue of $\Delta+V$, and prove absence of
eigenvalues when $|V(n)|\leq C|n|^{-1-\varepsilon}$ for some $\varepsilon>0$. At $\lambda=0$, the critical power changes and we construct potentials $V$ satisfying $|V(n)|\leq C|n| ^{-2}$ for which $0$ is an
eigenvalue of $\Delta+V$, as well as prove absence when $|V(n)|\leq C|n|^{-2-\varepsilon}$ for any $\varepsilon>0$. Finally, at each spectral edge, we show that, for every $K\geq3$, an
eigenvalue can be created by potentials supported on exactly $K$ sites, whereas a potential supported on at most two sites cannot create an edge
eigenvalue. The proofs combine Green-function expansions and moment cancellation,
Hilbert-space-valued iterations, discrete Carleman estimates, and a uniform Green-kernel estimate.
Read the full abstract ▾
Solar and Stellar Astrophysics
The JWST Proto-PAH Project: Detection of the methyl radical CH$_{3}$ in the highly evolved C-rich object SMP LMC 011
Jialu Li, D. A. García-Hernández, A. Manchado et al. (+17 more)
We report the first detection of the neutral methyl radical CH$_3$ in a highly evolved C-rich object, SMP LMC 011, using JWST MIRI/MRS. CH$_3$ is well fitted by an excitation temperature of $T_{\rm ex} \simeq$~190\,K and a column density of $N_{\rm tot}(\mathrm{CH_3}) \simeq 5.6\times10^{17}$ cm$^{-2}$. We also report the non-detection of ethane (C$_2$H$_6$), consistent with CH$_3$ reacting preferentially with unsaturated radicals rather than self-recombination, which may be inefficient in SMP LMC 011. Combined with the exceptionally large benzene column density of SMP LMC 011, this supports a methyl-addition route from benzene towards alkyl-substituted aromatics. We propose that the high CH$_3$ abundance is driven by the erosion of hydrogenated amorphous carbon (HAC)
dust grains in the dense warm
torus by UV
photons from the central
star and/or by shocks, which release CH$_3$ directly into the gas phase. These results establish CH$_3$ as a key reactive intermediate in the formation of complex hydrocarbons in C-rich circumstellar environments. Chemical models that incorporate methyl-addition reactions are needed for a better understanding of PAH formation pathways in evolved
stars. The potential detection of alkyl-substituted aromatics such as toluene (C$_7$H$_8$) and ethylbenzene (C$_8$H$_{10}$) in C-rich evolved
stars would provide direct confirmation of CH$_3$-driven aromatic growth in circumstellar environments.
Read the full abstract ▾
All authors Jialu Li, D. A. García-Hernández, A. Manchado, Debayan Das, J. Cami, Els Peeters, G. C. Sloan, B. Aringer, J. Bernard-Salas, C. Bhatt, Nicholas Clark, Harriet L. Dinerstein, M. A. Gómez-Muñoz, Kathleen E. Kraemer, M. Matsuura, R. Sahai, N. C. Sterling, Kevin Volk, G. M. Wahlgren, A. A. Zijlstra
Quantum Physics
Li Gao and Jingyu Guo
We introduce the notion of the BKM coercivity constant and show that the positivity of this constant governs the exponential relative
entropy decay of the
semigroup. Indeed, we prove that the modified log-Sobolev constant is equivalent to the BKM coercivity constant up to a constant depending on the asymptotic conditional expectation. We also discover that the BKM coercivity constants for
matrix amplifications are already attained with a
qubit auxiliary system, which also coincides with the GNS spectral gap of the generating Lindbladian. As a corollary, we establish a criterion that the complete modified log-Sobolev inequality holds if and only if the GNS gap of the
semigroup is strictly positive. All the discussion above applies to
quantum Markov
semigroups that admit a faithful asymptotic conditional expectation as long-time equilibration, with no detailed balance condition assumed. As an application, we show the finite-dimensional Chen-Kastoryano-Gilyén Gibbs samplers always satisfy the complete modified log-Sobolev inequality.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Ce II-IV emission in kilonovae with R-matrix collision strengths and distorted wave recombination rates
Leo Patrick Mulholland, Niamh Ferguson, Luke J. Shingles et al. (+3 more)
We provide transition probabilities and Maxwellian-averaged collision-strengths for the electron-impact excitation of Ce ii - iv. These ions are potentially abundant in kilonovae (KNe) and feature both forbidden and allowed transitions in the infrared. These atomic data are obtained using the grasp$^0$ atomic structure code, interfaced with the non-perturbative darc R-
matrix close-coupling codes. We additionally use autostructure to produce dielectronic and radiative recombination rate coefficients for Ce ii - vi. Using this data, we calculate an approximate ionization balance including non-thermal ionization rates with deposition rates from realistic models. We find Ce ii - iv to be of roughly equal abundance, subject to ejecta conditions. We find that generally we need $\gtrsim$ 10$^{-3}$ M$_{\odot}$ of Ce in total to produce emission of comparable luminosity to the features in the spectrum of AT2023vfi. In particular, it is found that [Ce iv] 4.5 $\mu$m requires both strong ionization and weak recombination, as well as a production of Ce considerably stronger than that of the
solar abundance in order to have luminosity comparable to the apparent emission in this wavelength vicinity in \grb. %which is seemingly incompatible with the current understanding of the bulk composition of KNe. With such strict requirements on individual element masses, the detection of individual lanthanides on a line-by-line basis in the nebular phase seems unlikely - but lanthanides may remain important for cooling and early time analyses.
Read the full abstract ▾
All authors Leo Patrick Mulholland, Niamh Ferguson, Luke J. Shingles, Catherine A. Ramsbottom, Connor P. Ballance, Stuart A. Sim
Chemical Physics
Toward Predictive Hydride Bond Energetics with Neural-Network Wavefunctions
Aqsa Shaikh, Lubos Mitas, P. Ganesh et al. (+1 more)
Accurate prediction of transition-metal hydride (TM-H) bond dissociation energies (BDEs) remains challenging because of strong electron correlation, relativistic effects, and
nuclear quantum contributions. Here, we assess the performance of neural-network variational Monte Carlo (NN-VMC) based on the Psiformer ansatz for systems with increasing complexity (LiH, OH, TiH and NiH), and compare it against CCSDT(Q)/CBS as well as available theoretical and experimental data. Throughout this study, both NN-VMC and ab initio calculations employ a common ccECP
Hamiltonian to enable tractable and consistent comparisons. To reduce finite-training errors, we introduce complementary zero-variance and infinite-step extrapolation schemes. For LiH and OH systems, NN-VMC yields total energies that differ within sub-milli Hartree compared to CBS extrapolated ab initio results and the BDE differences remain under 2$\sigma$. In case of Ti and TiH, the variational NN-VMC energies at the end of training are already consistent with CCSD(T)/CBS, while post-training extrapolation systematically closes the gap towards the CCSDT(Q)/CBS results. In contrast, NiH provides a stringent test of wavefunction expressivity, where increasing the number of determinants in NN-wavefunction ansatz improves the recovered correlation energy. The comparison of NiH BDE reveals that, while the existing theoretical predictions cluster into distinct high and low BDE groups, the broad scatter in available experimental data prevents a definitive assessment of the most accurate theoretical approach. This work demonstrates that NN-VMC with ccECPs
Hamiltonian provides a competitive framework for quantitative prediction of main-group and early TM-H energetics, while identifying late TM-H as an important
benchmark for future developments in neural-network wavefunctions and electronic structure theory.
Read the full abstract ▾
All authors Aqsa Shaikh, Lubos Mitas, P. Ganesh, Jaron T. Krogel
Statistical Mechanics
Bridging Control, Inference, Transport, and Thermodynamics: From Theory to Applications in Learning
Emmy Blumenthal, Nikolas Claussen, Benjamin Eysenbach et al. (+4 more)
The last decade has seen the development of powerful methods for learning complex structure from high-dimensional data. These advances have brought to the foreground fundamental connections between subdisciplines of physics, applied mathematics, and machine learning. In this review, we bring together some of these ideas, often expressed in different
languages, to highlight a conceptual thread that links five distinct fields: control theory, optimal transport, probabilistic inference, non-
equilibrium thermodynamics, and machine learning. A common theme is the optimization of free-energy-like functionals under dynamical or statistical constraints. We offer a guided tour through this thread and present selected applications in reinforcement learning, variational inference, and generative modeling. The review does not assume prior familiarity with these topics, and begins with principles originating from physics.
Read the full abstract ▾
All authors Emmy Blumenthal, Nikolas Claussen, Benjamin Eysenbach, Catherine Ji, Gautam Reddy, Colin Scheibner, Benjamin Sorkin
High Energy Astrophysical Phenomena
Impact of uncertainties on the cosmic optical and infrared backgrounds on the propagation of astroparticles
Lucas Gréaux, Antonio Condorelli, Leonel Morejon et al. (+2 more)
When propagating through the universe, gamma rays at very-high energy (VHE, E > 100 GeV) and ultra-high energy
cosmic rays (UHECRs, E > 1 EeV) can interact with the optical, infrared and microwave
photon fields that permeate the universe. These interactions result in a characteristic absorption imprint in the spectra of extragalactic gamma-ray sources at VHE, and in a change in the mass-composition of UHECRs. The study of both VHE gamma rays and UHECRs therefore requires precise knowledge of the intensity of the
cosmic photon fields. In this work, we explore the impact of the current uncertainties on the optical and infrared
photon fields on the propagation of astroparticles. We restrict the range of available models to those best matching the recent measurements, and compare the different reconstructions resulting from these models. We find that the knowledge on the
cosmic background light is no longer the dominant source of uncertainties in understanding the phenomenology of astroparticle sources in the low
redshift universe (z < 0.1), enabling robust spectral and composition inference with the next generation of both gamma-ray and UHECR measurements.
Read the full abstract ▾
All authors Lucas Gréaux, Antonio Condorelli, Leonel Morejon, Karl-Heinz Kampert, Jonathan Biteau
Statistical Mechanics
Modulated structures in discrete approximations to a three-dimensional cholesteric model on a recursive lattice
William de Castilho
We study finite-state approximations to a
chiral nematic
lattice model whose local directors are embedded in three-dimensional orientational space. The model analyzed here is formulated in terms of a rotated quadrupolar interaction, which provides a direct angular chirality parameter $\Delta$ and reduces to the usual planar
chiral-nematic form for directors confined to the xy plane. On a rooted Cayley tree, the statistical problem is written as a nonlinear recursion for branch partition functions. In the infinite-coordination limit, with $rJ_Q$ fixed, the recursion becomes a softmax map for the state probabilities. We analyze Cartesian three-state, planar four-state, and non-planar four-state discretizations. The first supports ordered and period-two attractors, whereas the planar four-state discretization displays a sequence of commensurate and longer-period modulated attractors. Its disordered fixed point loses stability at $t=9/16$ through a complex-conjugate pair with phase $q=\pm 2\Delta$, so a modulated critical mode is selected for every nonzero chirality. The non-planar four-state set is intrinsically anisotropic and, when the stated model is reconstructed directly, supports prominent period-three as well as period-two and higher-period cycles. Because attractor stability does not by itself establish global thermodynamic stability, the diagrams reported here are interpreted as attractor/stability diagrams rather than
equilibrium phase diagrams.
Read the full abstract ▾
Materials Science
High-Temperature Hydrogen Sensors Based on Gallium Oxide Heterojunction Diodes
William A. Callahan, Kingsley Egbo, Anna Sacchi et al. (+5 more)
Long-term, high temperature operation of Ga2O3 devices is a crucial hurdle that must be overcome before widespread adoption of the technology can be achieved, but is largely absent from the overall body of work. Demonstrations up to this point show devices are either limited by material or dopant instability that leads to performance degradation with time. Herein, Ga2O3-based hydrogen sensors employing Pt Schottky and Cr2O3/Ga2O3 p-n diodes (Mg- and N-doped) were fabricated and evaluated for long-term stability at 600C for 800-1,800 hours, with cyclic exposure to N2 and low-concentration H2 (500-1,500 ppm). Transient current density (measured at -0.1 V) and periodic J-V characterization were used to track performance. Despite gradual declines in sensor signal and sensitivity, devices distinguished hydrogen concentrations throughout weeks of operation. Degradation was architecture-dependent: Cr2O3:Mg degraded gradually, consistent with known Mg migration; the Pt Schottky diode showed dramatic changes after 1,000 hours; and Cr2O3:N showed the lowest but most stable performance before failing at 800 hours. Thermionic emission and Lambert W-based modeling confirmed hydrogen exposure reduces interfacial barrier height via a
proton-induced dipole mechanism common to both diode types. TEM of aged Pt Schottky diodes revealed Pt grain growth and microvoid formation as key degradation mechanisms. TOF-SIMS confirmed nitrogen dopants remain confined to the Cr2O3:N layer, supporting N-doping as a stable, lower-performance alternative to Mg-doping
Read the full abstract ▾
All authors William A. Callahan, Kingsley Egbo, Anna Sacchi, Michelle Smeaton, Michael Walker, Anna Staerz, Ryan O'Hayre, Andriy Zakutayev
Astrophysics of Galaxies
Rubin Observatory Reveals a Dust-Shrouded Halo Globular Cluster in Ophiuchus
Aashay Pai, William Cerny, Andrew B. Pace et al. (+9 more)
We present the discovery of the Milky Way satellite Rubin-GC1 (Rubin J1628-1735) using data from the NSF-DOE Vera C. Rubin Observatory's Early Data Preview 2. The system was discovered in the direction of the
Galactic bulge with $(l, b) \sim (359^{\circ}, 21^{\circ})$ in a region of high
stellar density and a foreground reddening of $E(B-V) \approx 0.7$. We simultaneously fit the morphology and isochrone parameters of Rubin-GC1, determining that it is a faint ($M_V = -2.4^{+0.5}_{-0.7}$) and compact ($r_{1/2} = 5^{+1}_{-1}$ pc) Milky Way satellite at a distance of $D_\odot = 31^{+3}_{-3}$ kpc; its
stellar population is intermediate-age ($\tau=9.2^{+1.2}_{-0.7}$ Gyr) and moderately metal-rich ($\mathrm{[Fe/H]_{iso}}=-0.73^{+0.04}_{-0.04}$). Together, these properties suggest Rubin-GC1 is most likely a
star cluster in the faint tail of the luminosity function of globular clusters surrounding the Milky Way. We identify a distinct proper motion signature from Rubin-GC1 in
Gaia DR3, and from a comparison of the system's 5D phase space information to $N$-body models of the Sagittarius
dwarf spheroidal
galaxy's
tidal stream, we determine that Rubin-GC1 is likely an accreted cluster associated with the Sagittarius leading arm. The discovery of Rubin-GC1 highlights the potential of Rubin to uncover faint, resolved satellites in
dust-shrouded regions of the Milky Way, including remnants of the
accretion events that have shaped the
Galaxy's hierarchical assembly.
Read the full abstract ▾
All authors Aashay Pai, William Cerny, Andrew B. Pace, Alex Drlica-Wagner, Peter S. Ferguson, Marla Geha, Chin Yi Tan, Sasha N. Campana, Burçin Mutlu-Pakdil, Alexander H. Riley, Nora Shipp, Guy S. Stringfellow
Quantum Physics
Generation of entanglement and magic via continuous homodyne monitoring of a qubit pair
Debmalya Das, Giuseppe Magnifico and Maria Maffei
Continuous weak measurements of
quantum systems are of great relevance in
quantum foundations and applications. They can be achieved by probing the
quantum system of interest by repeatedly measuring an auxiliary system weakly coupled to it. Here we study two
qubits coupled in different points to a common one-dimensional electromagnetic field and simultaneously monitored in the right- and left-propagating output channels by homodyne detection. Using a collision-model description, we derive an analytical
Stochastic Master Equation (SME) governing the resulting diffusive
quantum trajectories, including the interference between the two measurement channels. For nonlinear functions of the
quantum state, such as
entropies, averages over
quantum trajectories generally differ from the corresponding quantities evaluated on the unconditional state. Through this mechanism, we show that continuous monitoring generates
entanglement, absent in the unconditional dynamics, and enhances
quantum magic in the
qubit pair during the decay. Both resources can be tuned through the optical phase accumulated between the
qubits and the phases of homodyne local oscillators. Our results establish continuous homodyne monitoring of multiple emitters as a tunable mechanism for generating
quantum resources.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Up/down-conversion of infrared light by few-layer graphene polytypes
Patrick Johansen Sarsfield, Takaaki V. Joya, Takuto Kawakami et al. (+2 more)
Optical nonlinearity of materials with broken inversion
symmetry enables two-
photon processes where an incoming pair of
photons can generate an up-converted
photon with the combined frequency, or a high-energy
photon can be split into a correlated pair of down-converted
photons. Here, we identify few-layer
graphene films that offer up/down-conversion capability in the infrared spectral range. For mixed stacking tetralayers (ABCB), which are non-centrosymmetric 2D
crystals, we find highly efficient nearly resonant up/down-conversion of [$\omega_1,\omega_2$]
photon pairs into/from a
photon with $0.7$eV$<\Omega=\omega_1+\omega_2<1.1$eV. We also note that a pronounced second-order nonlinearity in the spectral range of $0.7$eV$<\Omega<0.9$eV can be promoted in rhombohedral tri- and tetralayers by asymmetrical encapsulation. Potentially, for fibers coated with few-layer
graphene, this opens the door for “in fiber" production of
photon pairs with correlated polarizations.
Read the full abstract ▾
All authors Patrick Johansen Sarsfield, Takaaki V. Joya, Takuto Kawakami, Mikito Koshino, Vladimir Falko
Quantum Physics
Probing Residual Noise at a Decoherence Sweet Spot in a $^{28}$Si/SiGe Spin Qubit
Shinwoo Lee, Hanseo Sohn, Jaemin Park et al. (+7 more)
In $^{28}$Si/SiGe
spin qubits with micromagnets, the longitudinal stray field gradient transduces charge noise into
qubit frequency noise and limits coherence. We compare two neighboring
qubits in the same device with 800 ppm residual $^{29}$Si, one near a decoherence sweet spot where the gradient is locally minimized and the other at a position with a larger gradient. At the sweet spot, $T_2^*$ reaches 67 $\mu\mathrm{s}$ and the Carr-Purcell-Meiboom-Gill coherence time reaches 4.6 ms, whereas $T_2^*$ is 5.2 $\mu\mathrm{s}$ at the neighboring
qubit. Near 1 Hz, the frequency noise power spectral density at the sweet spot is nearly two orders of magnitude lower than at the neighboring
qubit. The magnitude and low-frequency decay of the residual spectrum are compatible with the prediction for $^{29}$Si
nuclear spin noise, and the weak interqubit correlation indicates that local noise becomes important for dephasing at the sweet spot. Despite a finite correlation with the charge sensor, sweet-spot operation strongly reduced the transduction of charge noise, bringing the residual frequency noise close to the level predicted for $^{29}$Si
nuclear spin fluctuations.
Read the full abstract ▾
All authors Shinwoo Lee, Hanseo Sohn, Jaemin Park, Hyeongyu Jang, Jonginn Yun, Jun Yoneda, Lucas E. A. Stehouwer, Davide Degli Esposti, Giordano Scappucci, Dohun Kim
Nuclear Theory
Neutron Skin Effects on Particle Emission in Heavy-Ion Collisions: A Topic Review with Astrophysical and Nuclear Structure Connections
Bao-Jun Cai, De-Qing Fang and Yu-Gang Ma
The
neutron skin, defined by the difference between
neutron and
proton root-mean-square radii, is a characteristic manifestation of isospin asymmetry and an important probe of the isovector
nuclear interaction. This focused review examines how
neutron skins influence particle emission and collective dynamics in heavy-ion collisions, from the
Fermi-energy regime to ultra-relativistic energies. By modifying the initial
neutron and
proton density profiles, the
neutron skin affects the isospin composition and geometry of the participant region, pre-
equilibrium emission, particle production, fragment formation, and collective flow. We review
neutron-to-
proton and $\rm{t}/^3\rm{He}$ yield ratios, light clusters, pion ratios, bremsstrahlung
photons, isoscaling and fragment momentum distributions, and
neutron-
proton differential flow and momentum observables, emphasizing their interplay with the
symmetry energy and transport dynamics. At high energies,
neutron skins also modify the initial geometry, eccentricities, multiplicities, and anisotropic flows in isobar and heavy-
nucleus collisions. We discuss the challenge of disentangling these effects from deformation, surface diffuseness, shell structure, clustering, and model dependence. Broader connections to parity-violating electron scattering, dipole responses, coherent elastic
neutrino-
nucleus scattering, SRC-induced
proton skins in momentum space, and
neutron-
star observables are also explored. Finally, we highlight opportunities from radioactive beams, improved collision experiments, microscopic many-body and transport calculations, and
Bayesian inference. Combining multiple reaction systems and observables with complementary
nuclear-structure and astrophysical information will be essential for quantitatively constraining
neutron skins and the density dependence of the
symmetry energy.
Read the full abstract ▾
Strongly Correlated Electrons
Chiral Antiferromagnetism from Momentum-Space Resonance in a 2D Semiconductor
R. Okuma, T. Ikenobe, Y. Fujisawa et al. (+28 more)
Understanding the principles governing the emergence of
chiral quantum phases is a fundamental challenge, not only for uncovering new mechanisms of
quantum-state formation but also for realizing
giant electronic responses and transport phenomena arising from chirality and
topology. While
Fermi-surface instabilities in metals can stabilize complex ordered states through multiple competing scattering channels, their microscopic origin is often obscured by the complexity of the underlying electronic structure, limiting the development of general microscopic design principles. Here, we introduce a complementary strategy based on the simplicity of
semiconductor band extrema. Using the layered van der Waals
semiconductor GdGaI, whose low-energy electronic structure consists of simple electron and hole valleys, we discover the spontaneous emergence of an intertwined
chiral triple-$q$
antiferromagnetic state accompanied by a cooperative reconstruction of the electron-hole band edges, beyond the conventional expectation of a single-$q$ ground state. This collective reconstruction generates substantial momentum-space Berry
curvature, giving rise to a pronounced spontaneous anomalous
Hall effect despite the semiconducting character and negligible net magnetization. Remarkably, this
chiral state is realized within an atomically well-defined ($\approx2a$), topologically nontrivial
magnetic texture, showing that such collective
quantum states can emerge at an exceptionally small length scale from a simple two-dimensional
magnetic semiconductor. More broadly, our results introduce a remarkably simple design concept for
chiral quantum matter: using simple
semiconductor band extrema as building blocks for resonance-like interplay in momentum space, providing a route to Berry
curvature, topological transport, and emergent
quantum phases.
Read the full abstract ▾
All authors R. Okuma, T. Ikenobe, Y. Fujisawa, K. Yamagami, H. C. H. Wu, T. Nakamura, Y. Ihara, H. Ishikawa, H. Suwa, H. Ishizuka, Y. Akagi, T. Kaneko, C. H. Hsu, Y. Obata, N. Tomoda, M. Dronova, K. Nagasawa, H. Saito, D. Ueta, H. Sagayama, J. Yamaura, M. Arita, K. Yogendra, S. Ideta, K. Kindo, T. Nakajima, S. J. Blundell, T. Kondo, K. Shimada, Y. Okamoto, Y. Okada
Accelerator Physics
Simulation study of accelerator-based muography using the GeV-scale forward muon component at SHINE
Jiangtao Wang, Yinghe Wang, Si Chen et al. (+7 more)
Muography exploits the penetrating power of
muons to image the interior of large dense objects, but
cosmic-ray sources provide only ~1 {cm}^{-2} {min}^{-1} predominantly from above, limiting imaging speed and accessible geometries. Electron-driven
muon production has recently been demonstrated with
laser-wakefield accelerators, but shot-to-shot fluctuations hinder systematic studies required for quantitative accelerator muography. Using Geant4 Monte Carlo simulations, we model the full experimental setup at Shaft 2 of the Shanghai High repetition rate XFEL and Extreme light facility (SHINE), from a 3 GeV, 50 pC, 50 Hz commissioning electron beam interacting with a
muon target through 25 m of beamline structures and a 3 m-thick concrete isolation wall. Approximately 0.28 effective reconstructed single-
muon events per bunch, with residual kinetic energies below 1.2 GeV after traversing the wall, reach the downstream muography test area (~14 s^{-1}). The wall absorbs most charged background particles below ~1 GeV, while residual
neutrons can be discriminated by their characteristic detector energy deposition. Scattering-
tomography simulations show that $3\times 10^{5}$ effective
muon events, accumulated in approximately 6 h at the commissioning rate, yield a Structural Similarity Index above 0.9, demonstrating the feasibility of quantitative accelerator-based muography using SHINE's electron-driven GeV-scale forward
muon source. At the 8 GeV/50 kHz
benchmark, the projected
muon intensity exceeds $5 \times 10^{4}$ {\mu}/s, corresponding conservatively to approximately one
muon per bunch at the detector. This exceeds the
cosmic-ray flux by orders of magnitude, while SHINE's superconducting linac provides a stable, controlled platform for developing electron-on-target muography.
Read the full abstract ▾
All authors Jiangtao Wang, Yinghe Wang, Si Chen, Rongbing Deng, Kim Siang Khaw, Jun Kai Ng, Qisheng Tang, Dong Wang, Wenzhen Xu, Jia Cheng Yap
Chemical Physics
Exchange-Correlation Potentials and Energies from Inverse Generalized Kohn-Sham Calculations
Vishal Subramanian, Bikash Kanungo, Vaibhav Khanna et al. (+2 more)
The Kohn-Sham (KS) formulation of density functional theory (DFT) is a map from the many-electron problem to an effective single-electron problem that is governed by a local multiplicative potential. The generalized-Kohn-Sham (GKS) formalism extends it to permit any single-electron operator—nonlocal, local non-multiplicative, local multiplicative, or any combination of them. Doing so expands the scope and ease of modeling the exchange-correlation (XC) functional in DFT, which encodes the complicated many-electron interactions into a mean-field of the electron density. However, unlike KS theory, development of XC functionals in GKS theory has been hindered by the absence of corresponding exact XC potentials and energies. We present the exact XC potentials and energies for atoms and molecules by solving the inverse GKS problem, using highly accurate correlated ab initio densities. Our approach is validated across weakly and strongly correlated systems. We further examine a common, yet untested, assumption that KS and GKS correlation potentials and energies are similar, finding instead that they differ substantially in strongly correlated systems. Overall, this work offers a powerful tool to model next-generation of XC functionals within the GKS formalism of DFT.
Read the full abstract ▾
All authors Vishal Subramanian, Bikash Kanungo, Vaibhav Khanna, Paul M. Zimmerman, Vikram Gavini
Atomic Physics
Absolute frequency measurement of the $^{40}$Ca$^{+}$ clock transition using a GNSS link to the SI second
M. Guevara-Bertsch, M. K. Joshi, M. I Hussain et al. (+2 more)
We report the absolute frequency measurement of the $4s$ $ ^{2}S_{1/2}\leftrightarrow 3d$ $^{2}D_{5/2}$ $^{40}$Ca$^{+}$ clock transition with respect to the SI second. To perform this measurement, a link between our laboratory in Innsbruck and the clocks realizing the Coordinated Universal Time at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig was installed and characterized using the Global
Navigation Satellite System GNSS. The comparison between our clock and the ones at PTB was done using the Precise Point Positioning technique. After the evaluation of the systematic shifts, the measured transition frequency is 411 042 129 776 401.2$\pm$0.6 Hz with a fractional uncertainty of 1.5 $\times$ 10$^{-15}$. The stability of the clock measurements was also corroborated by comparing two different calcium ion clock experiments, which share the clock
laser source at our institute. Furthermore, after careful evaluation of the trap-drive induced ac
magnetic fields, we estimate ac Zeeman shifts on the $D_{5/2}$ sublevels and reevaluate the Landé g-factor of the $3d$ $^{2}D_{5/2}$ level to be g$_{5/2}= 1.200329(1)$.
Read the full abstract ▾
All authors M. Guevara-Bertsch, M. K. Joshi, M. I Hussain, R. Blatt, C. F. Roos
Quantum Physics
Limits on the atomic description of four-wave mixing
Irvin F. Ángeles-Aguillón, Nieves Arias-Téllez, Pablo Yanes-Thomas et al. (+2 more)
The limits of the well-established single-atom model for describing
photon-pair generation via four-wave mixing in a diamond configuration in atomic ensembles are experimentally tested. Using a cold-atom source, biphotons are generated and detected through polarization analyzers that resolve the emitted light into horizontal and vertical components in the laboratory frame. The pump
lasers driving the first and second excitation transitions are horizontally and vertically polarized, respectively. To predict single-
photon counts and coincidence rates in all polarization channels, the first- and second-order correlation functions are calculated directly using a comprehensive model that accounts for all Zeeman sublevels of the relevant hyperfine states. Furthermore, the population dynamics with and without the re-pump
laser of the magneto-optical trap are compared, revealing substantial differences in the populations of the Zeeman sublevels. This motivates the inclusion of two additional hyperfine levels and their corresponding Zeeman sublevels in the final model. The resulting density
matrix is used to calculate expectation values of the far-field electric-field operators and compare them with experimental measurements over a range of pump-
laser powers. Excellent agreement with the measured
photon counts is obtained over most of this range. For the coincidence measurements, good agreement is found when the polarization of the
photon generated by the first (second) decay is parallel to that of the first (second) pump beam. In contrast, the model consistently underestimates the experimental coincidence rates for the opposite polarization configuration. These findings indicate that effects beyond the internal level dynamics of individual atoms, most notably collective phenomena, are required to fully account for
photon coincidences generated by four-wave mixing in atomic ensembles.
Read the full abstract ▾
All authors Irvin F. Ángeles-Aguillón, Nieves Arias-Téllez, Pablo Yanes-Thomas, Alejandro Kunold, Daniel Sahagún-Sánchez
Quantum Physics
Instantiating Microcrypt: Obstacles and opportunities via tailored state certification
Jose Carrasco, Jens Eisert, Soumik Ghosh et al. (+3 more)
Recent work has introduced the
Hamiltonian phase state (HPS) assumptions, which postulate that
Hamiltonian phase states can be used to instantiate pseudorandom and one-way state generators. Additionally, it has been conjectured that these assumptions can be true, even if one-way functions do not exist. This is exciting, because if true, then the HPS assumptions provide a route to the instantiation of Microcrypt. In this work we falsify this
conjecture, by proving that if the HPS assumptions are true, then one-way functions exist. While this removes the possibility of instantiating genuine Microcrypt cryptography with
Hamiltonian phase states, it shows that the HPS assumptions provide novel inherently
quantum assumptions for the construction of classical cryptography. Technically we achieve this via a method for the construction of one-way puzzles from one-way state generators and tailored "measure first, ask later" state certification protocols. This generalizes prior constructions of one-way puzzles from one-way state generators via classical shadows and allows us to relate properties of the one-way puzzle to properties of the state certification protocol used in the construction. Specifically, if the state certification protocol admits efficient classical post-processing then one obtains an efficiently verifiable one-way puzzle, and if the state certification protocol can be efficiently classically simulated in a certain sense, then one obtains a classical one-way puzzle, which implies one-way functions. The latter observation allows us to prove that the HPS assumptions imply one-way functions, by exploiting properties of state certification protocols for phase states. The former observation provides a new toolbox for the construction of efficiently verifiable one-way puzzles by exploiting tailored state certification protocols for pseudorandom and one-way state generators.
Read the full abstract ▾
All authors Jose Carrasco, Jens Eisert, Soumik Ghosh, Dominik Hangleiter, Nicky Kai Hong Li, Ryan Sweke
Soft Condensed Matter
Collective adaptation to time-dependent targets for active Brownian particles
Gerhard Jung and Eric Bertin
We consider a minimal model of active
agents which collectively learn to reach a target macroscopic state via a decentralized adaptation process.
Agents are modeled as active Brownian particles which randomly reorient to a given direction through tumbling events. An average target state is encoded into a reward function evaluated by each
agent.
Agents can tune one of the parameters of their microscopic dynamics, called `policy' (e.g., speed or reorientation direction), to optimize their reward function thanks to information exchange with neighboring
agents. We describe the
evolution of the policy distribution across the
agent population with a kinetic theory, under the assumption that the adaptation process is slow with respect to the physical dynamics. The adaptation process is illustrated on several learning protocols with either fixed or time-dependent target velocities. A characteristic learning time $\tau$ combining teaching and mutations emerges from the dynamics. For time-oscillating targets at angular frequency $\omega$, the collective dynamics oscillates in time, with an oscillation amplitude and phase shift determined by the product $\omega \tau$. An unlocking transition to a non-adaptable state is also observed for a rotating target velocity.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Cosmological Signatures of Curvature-Coupled Dark Energy
Abdolali Banihashemi, Farbod Hassani, Alessandro Casalino et al. (+2 more)
We study a
curvature-coupled dark energy model that can modify cosmological
evolution both before recombination and during the late-time accelerated era. The model belongs to the class of scalar-tensor theories, in which a quintessence field is non-minimally coupled to the
Ricci scalar. We specify the model through a shifted quartic coupling, $f(\varphi)=\alpha(\varphi^2-\varphi_{\rm today}^2)^2$, and an inverse power-law potential, $V(\varphi)=\Lambda\varphi^{-\sigma}$, where $\varphi_{\rm today}$ is a constant fixed by requiring the effective Planck mass to recover its present-day normalization. We implement the model in a modified version of $\mathtt{hi\_class}$ and compute its background and linear cosmological predictions. This specific form of non-minimal coupling allows an effective crossing of the phantom divide at late times while naturally suppressing deviations from standard
gravity today and satisfying local
gravity constraints. At the same time, the scalar field can modify the expansion history before recombination, shifting the acoustic scale in the direction required to alleviate the $H_0$ tension, while remaining dynamically relevant as dark energy at low
redshift. For the parameter choices studied here, we find tens-of-percent deviations from $\Lambda$CDM in the expansion history, matter clustering, and metric-potential spectra. The modified
evolution of the gravitational potentials leaves characteristic signatures in relativistic observables, with weak-
lensing power suppressed by $\mathcal{O}(20$-$40\%)$ at low multipoles and order-unity changes in the late Integrated Sachs-Wolfe signal. Together, these results reveal a broad, scale-dependent phenomenology that motivates both a full parameter-space analysis and an extension of the present linear treatment to a dedicated non-linear $N$-body implementation.
Read the full abstract ▾
All authors Abdolali Banihashemi, Farbod Hassani, Alessandro Casalino, David F. Mota, Emilio Bellini
Applied Physics · Cross-listed from cs.CE
Block-modular grey-box identification of a short-stroke seawater-pump power take-off for wave energy: loss decomposition and multi-regime validation
Mahdi Tayyebati, Amir Hamza Siddiqui, Mian Masoud et al. (+2 more)
Physically interpretable power take-off models support wave-energy development at every stage. For the seawater-pump class, few have been identified on a real machine and validated at the system level. This paper presents a block-modular grey-box model of a short-stroke seawater pump, identified from bench data alone. The pump decomposes into chamber, relief valve, piston seal and tip check valve, each structured by component physics, and the few parameters are identified block by block from terminal pressure, displacement, force and discharged-mass measurements, with a closed-cycle mass balance that decouples the degenerate seal and valve losses and closes to within 1% of the inflow. Over the sinusoidal campaign, the pressure-energised piston seal carries 84% of the lost mass and 97% of the lost energy, and the pump delivers about four-fifths of its input as high-pressure flow. Generalisation is demonstrated rather than assumed. With parameters fixed on ramps and sinusoids, the model reproduces 360 s sea-state records in free run to about 10% of range, captures 80% of several thousand peaks within 5 bar, transfers to a re-sprung valve on cracking strokes once its crack pressure is identified, follows thousand-cycle endurance records that drift below 0.1 bar, and reproduces the force and cycle-mean absorbed power, 0.1 to 5.7 kW, to a 4% median error. A practical-identifiability and uncertainty analysis confirms the terminal data resolve the retained parameters; thirty-seven repeated records set the experimental floor. The result is a compact, physically labelled model for design, energy assessment and model-based control of seawater-pump power take-offs.
Read the full abstract ▾
All authors Mahdi Tayyebati, Amir Hamza Siddiqui, Mian Masoud, Kristian Glejbøl, Christian Berggreen
Quantum Physics
Higher-order quantum thermodynamics: equilibrium and causal structure
Simon Milz, Kyrylo Simonov, Zoltán Zimborás et al. (+3 more)
Quantum thermodynamics is traditionally formulated as a theory of
equilibrium states and state transformations. Recent advances in higher-order
quantum transformations, which describe physical scenarios beyond states and channels and provide a systematic framework for causal order, raise the question of how
equilibrium should be defined and preserved in this more general setting. Starting from the Gibbs state as the unique
equilibrium state, we identify
equilibrium preservation as its natural higher-order extension. We show that, while this principle can in general give rise to distinct classes of transformations, all such distinctions disappear when
equilibrium preservation is required completely, namely under arbitrary ancillary extensions. Remarkably, every transformation satisfying this condition is causally ordered, making causal order an emergent consequence of thermodynamic
equilibrium. We establish this result for arbitrary higher-order maps and use the resulting framework to introduce free-energy-like quantities for
quantum channels. Our findings reveal a fundamental connection between thermodynamic
equilibrium and causal structure, providing a foundation for a fully fledged theory of higher-order
quantum thermodynamics.
Read the full abstract ▾
All authors Simon Milz, Kyrylo Simonov, Zoltán Zimborás, Tamal Guha, Saptarshi Roy, Giulio Chiribella
General Relativity and Quantum Cosmology
Analysis of GWTC-3 with multiple quasicircular models
N. Manning and R. O'Shaughnessy
The interpretation of gravitational wave sources depends on the specific choice of model used to interpret signals. Previous analyses of GWTC-3 event candidates using SEOBNRv4PHM, IMRPhenomXPHM, and NRSur7dq4 have sometimes arrived at notably different conclusions about event properties. Subtle analysis settings and code differences can also produce notable differences. We revisit 60 publicly available events from the first three observing runs, released across GWTC-1, GWTC-2, GWTC-2.1, and GWTC-3, using a consistent analysis framework and three waveform models: two state-of-the-art time-domain models with higher-order modes (SEOBNRv5PHM and IMRPhenomTPHM) and one older frequency-domain model without higher-order modes (IMRPhenomPv2). The two state-of-the-art models agree well overall, although about 20% of events have a visible difference in at least one one-dimensional marginal posterior. By contrast, the older model often arrives at qualitatively different conclusions for key events across the mass spectrum. We also identify a bug in published LVK GWTC-2.1 SEOBNRv4PHM results and in a later reprocessing of GW200105. At the adopted sampling rates, the model's Nyquist-frequency restriction excluded part of the allowed parameter space and artificially truncated the mass-ratio posterior away from equal mass for seven low-mass events. These results emphasize the need to use multiple state-of-the-art waveform models and carefully validated analysis settings to characterize uncertainty in gravitational-wave source properties.
Read the full abstract ▾