Papers

We present an emulator of the halo mass function (HMF) based on Gaussian-process regression, that exploits the evolution mapping framework. This framework splits cosmological parameters into shape parameters ($\mathbf{\Theta}_\mathrm{s}$), which set the shape of the linear power spectrum, and evolution parameters ($\mathbf{\Theta}_\mathrm{e}$), which only rescale its amplitude, with their net effect entirely captured by the clustering amplitude, $\sigma_{12}$. The emulation acts in two steps: first, an emulator predicts the overall shape of the HMF given $\mathbf{\Theta}_\mathrm{s}$ and $\sigma_{12}$; then, a second emulator applies a small correction accounting for the residual dependence on the integrated growth history of density fluctuations. The emulator is trained on a suite of 100 simulations of flat $\Lambda$CDM cosmologies but, owing to evolution mapping, can be applied to predict the abundance of haloes in cosmologies with any extended space of $\mathbf{\Theta}_\mathrm{e}$, such as curvature, quintessence and dynamical dark energy. We test the emulator against independent $\Lambda$CDM runs and on an additional validation suite of dynamical dark energy simulations, achieving per cent-level accuracy over a wide range of masses and redshifts, with the performance only slightly degrading at early times, where the training data points are fewer. Compared to other state-of-the-art HMF emulators, its accuracy is higher in nearly all tested cases. Our results demonstrate the broad applicability of the evolution mapping framework to build very accurate emulators of statistics of the density field. The emulator is publicly available as part of the Aletheia emulator suite.

Language models leave a distinctive vocabulary in the prose they help write, and we measure how much of the astronomy literature now carries it. From the full text of 207,111 astro-ph papers spanning 2015 to mid-2026, we count those words in each paper and model the counts, in proportion to paper length, as a mixture of assisted and unassisted writing in a hierarchical Bayesian model. Papers from before 2020 calibrate the unassisted rate, and the 392 papers that disclose model use calibrate the assisted one. Our answer depends on how often these words would appear today if nobody used a model, a rate that must be modeled rather than observed, so we extend it past 2020 under three assumptions and report all three. For 2025 that gives $54^{+8}_{-8}\,(\mathrm{stat},\,95\%)\,^{+26}_{-0}\,(\mathrm{sys,\ background})$% of papers, the second error being the spread across the three. The estimate stays at or above 36% when we vary that choice, the calibration, and the requirement that adoption only rises. A word list built from the astro-ph corpus, keeping only words that rose across every subfield, leaves 2025 in the same range. Assisted writing is also getting harder to see, since authors adapt to the words that reveal it and the marker excess more than halves between 2023 and 2026. Our model allows for that fading, so it can separate a fainter trace from reduced use. More than half of recent astro-ph papers therefore carry a language-model trace, while only 0.81% of 2025 papers disclose it, one declaration for every $\sim$66 papers with a trace.

A new generation of space-based observatories can transform small-body science from the local Earth-Moon environment to the Solar System's dynamical frontier, where planetary control gives way to Galactic tides and stellar encounters. Mapping this frontier would reveal how planetesimals were scattered during giant-planet formation, how many primordial bodies survived in distant reservoirs, and whether large objects remain undiscovered in the inner Oort Cloud. At the same time, meter- to decameter-scale natural objects traversing the Earth-Moon system are frequent but poorly characterized. As human and robotic activity expands, their operational relevance depends not simply on abundance but on object size, encounter geometry, exposed infrastructure, warning time, and available response. Lunar impacts and impact-generated ejecta provide one class of events, while fading objects with unresolved Earth or lunar impact probabilities provide another. Here, we explore a two-layer small-body program combining a 4.0 m-diameter Nautilus Quattro Imaging (NQI) unit with an illustrative distributed cislunar layer of ~50 cm-class wide-field optical telescopes. The cislunar layer would characterize the nearby natural-object population, support rapid classification and selective custody of high-interest objects, and monitor lunar impacts and ejecta; the NQI deep-search layer would provide precise astrometry and synthetic tracking for faint-object recovery and distant-Solar-System surveys. Together, the two layers would constrain the small-impactor population, resolve fading planetary-defense targets, and survey the distant Solar System to Vmag ~30, enabling tests of the Kuiper-Belt-to-Oort-Cloud transition while advancing Earth-Moon space resilience.

The recent 248-keV nuclear recoil candidate reported by LUX-ZEPLIN has renewed interest in endothermic inelastic dark matter, motivating us to examine its capture in primordial dark stars. Relative to the conventional elastic-capture picture in dark star evolution, endothermic capture adds two qualitative features. First, it opens only after the growing star crosses a compactness threshold, expressed as a kinematic radius $R_{\rm kin}\propto\mu_{\chi}M_\star/\delta$ set by the stellar mass, the dark-matter–nucleus reduced mass and the mass splitting. The accreting growth carries the star through the threshold, and the capture rate turns on quadratically above it. Second, although newly captured particles generically begin on nonthermal bound orbits, endothermic kinematics can keep this normally transient population spatially extended, turning it into a persistent reservoir rather than an intermediate step toward a thermal core. Following complete chains of state-changing collisions, we find that the reservoir compacts sharply and then stalls, because a ground state particle below a compactness-dependent orbital energy has no allowed up-scatter anywhere in the star. A percent-level radius contraction reopens the relaxation. These kinematic results do not depend on whether the excited state decays promptly or is long-lived. As a result, inelastic capture does not replenish a thermal annihilation core. The captured population forms an evolving orbital distribution that sets up the co-evolutionary dynamics between the star and the dark matter in the core and the reservoir, which we develop in a companion paper.

We extend the Dark Matter-Baryon Separability Condition to show that the same framework developed for dark matter deficient galaxies naturally admits a conjugate branch describing preferential baryonic depletion. Using the recently discovered almost-dark galaxy TTT J1237327+143535 as a worked example, we derive a family of dynamical consistency relations parameterized by the unknown progenitor ratio $\mu_i$, including thresholds for $\sigma_{\rm los}$, $M_{\rm dyn}$, the enclosed baryonic fraction and the dynamical mass to light ratio. We further connect the separability framework to the expected globular cluster population, providing an independent consistency test of the inferred halo mass. We also provide some bounds on the baryon ratio using the tidal properties of Virgo Cluster. Future measurements of stellar kinematics, gas content and globular clusters can therefore determine whether this galaxy occupies the positive separability branch and also test whether dark matter deficient and baryon depleted systems can be described within a common framework.

We present an implementation of a conditional-squeezing gate that squeezes a SQUID-terminated resonator mode along a direction determined by the state of a dispersively coupled qubit. This gate generalizes the controlled-squeezing gate [Phys. Rev. A 111, 042606 (2025)], and relies on a refocusing technique to suppress unwanted effects arising from slowly varying time-dependent terms in the Hamiltonian during the state-dependent parametric resonance required for the operation. As an application, we use the gate to encode an arbitrary qubit state into superpositions of single- and two-mode squeezed states of the resonator. These non-Gaussian states enable error-detectable encoding through parity measurements. We show that refocusing substantially improves the encoding fidelity, which is ultimately limited by Kerr nonlinearities and dissipation in realistic implementations. For experimentally optimistic values of the nonlinearities and decay rates, we obtain encoding fidelities above 0.99 for arbitrary input qubit states. Our results provide a route toward extending this scheme to the generation of higher-order superpositions of squeezed states (a class of rotation-symmetric bosonic codes) using a control qudit.

We present a joint observational analysis confronting viable $f(R)$ modified gravity theories, specifically the Hu & Sawicki and Starobinsky models, with background and large-scale structure (LSS) data. Utilizing Monte-Carlo Markov chain (MCMC) sampling across datasets including baryon acoustic oscillations (BAO), type Ia supernovae (SNeIa), cosmic microwave background (CMB) distance priors, and linear growth measurements ($f\sigma_8$, $f$, $\sigma_8$), we place tight constraints on the model parameters governing deviations from General Relativity. For the full dataset combination, we obtain $\log_{10} b_\mathrm{HS} = -6.325_{-1.138}^{+1.216}$ for the Hu & Sawicki model and $b_\mathrm{S} = (0.8\pm61.0)\times10^{-4}$ for the Starobinsky model. Model comparison based on the Akaike Information Criterion indicates that these $f(R)$ extensions are statistically favored over flat $\Lambda\text{CDM}$ ($|\Delta\text{AIC}| \ge 3.99$) for the combined data. However, when considering the Bayesian Information Criterion, the evidence for support is significantly reduced. Furthermore, we construct two-dimensional phase-space diagrams in the $(\mu, \gamma)$ and $(\mu, \Sigma)$ planes across several redshifts, establishing a novel diagnostic null-test allowing us to probe for deviations from $\Lambda\text{CDM}$, corresponding to the fixed point $(1,1)$ in both planes, using LSS observables. Should future weak-lensing and galaxy surveys provide data points with $\mu-1<0$ and $\gamma-1>1$ or $\Sigma-1 < 0 $, then the aforementioned models could be directly ruled out.

In 1054 AD a daytime star appeared in the constellation of Taurus, for three weeks, and it was reported in various sources from Europe to China/Japan: it was one of the few documented galactic supernovae of the last two millenia. This paradigm has been established about sixty years ago, as the comprehension of the physics of supernovae progressed with enough observational data. The Gamma-ray bursts were discovered in the same period, but only in the past few years have their observations become daily and their distances have been fully understood as cosmological. After the explosion, the exponential decay of the luminosity in gamma-rays and X-rays has been followed with telescopes onboard dedicated satellites. Also the exponential decay of the afterglow's optical and radio frequencies have been observed with the largest optical and radio telescopes. Within the binary-driven hypernova framework, successful in explaining all the observed phases of the Gamma-ray bursts, the universal exponential decay can be extended to 1000 years after the burst, to account for the present values of Gamma and X-rays as well as optical and radio frequencies of the Crab Nebula. Both the daytime visibility of the burst, and the simultaneous radiation plagues appeared in Constantinople and Cairo is a strong evidence of the presence of Gamma-rays in the lower atmosphere, coming from the same source originating the Crab nebula. The association to the daytime visibility of that star and the following plague meets exactly the etymology of the word dis-aster, bad star.

This study evaluates viscosity-dependent limitations in refined potential flow theory (RPT) applied to incompressible flow over an impulsively started circular cylinder. RPT adapts classical potential flow theory to account for viscous effects, flow fluctuations, and three-dimensional variables. By utilizing a quasi-irrotational viscous stream function, the framework solves the continuity and Navier-Stokes equations while satisfying both free-stream and no-slip boundary conditions.

Natural load-bearing patterns such as leaf venation, trabecular bone, and spider webs achieve high stiffness per unit mass, yet classical topology optimizers rarely reach such geometries, and few let engineers express structural design intent through natural language. This work treats a frozen text-to-image diffusion model as a training-free source of design knowledge and distills it into the physics loop of density-based topology optimization via score distillation sampling, so that a text prompt becomes an explicit, machine-interpretable representation of engineer intent. The prompt-induced generative gradient and the finite element sensitivity are combined at every iteration, letting physics decide which prompt-induced features survive. In 245 primary SDS runs spanning four geometric domains and two physics regimes, 38 of 49 prompt–domain combinations achieved statistically significant compliance reductions (up to $-31.5\%$ mechanical and $-23.0\%$ thermoelastic), outperforming gradient-based baselines. Cross-domain morphological analysis identifies a recurring structural signature of improvement: in most domains the generative prior suppresses dead-end branches in the rib skeleton, with endpoint–compliance correlation $r = +0.56$ to $+0.99$. A Heaviside projection with $\beta$-continuation resolves a pronounced intermediate-density tendency in this diffusion–physics coupling ($42.6\%$ to $<3\%$), and an automated skeleton-based pipeline converts optimized density fields into \rev{candidate geometry ready for computer-aided design. By retargeting the generative prior across domains, loading conditions, and physics objectives through a change of text prompt, with each new problem's physics setup specified separately, the framework uses a pretrained generative model as a reusable, training-free prior for engineering design.

We present a nonrecursive method to compute the small-time heat kernel asymptotic expansion. The Klein-Gordon operator in flat space-time coupled to electromagnetic fields is considered. We obtain closed-form expressions for the expansion coefficients up to the second order in time. Our approach can be regarded as an extension of the method described in [R.I. Nepomechie, Phys. Rev. D 31, 3291 (1985)], but unlike that work, our approach is valid for arbitrary space-time dependence of the heat kernel, i.e. for off-diagonal values. We verify that our results correctly reproduce small-time asymptotics of the heat kernel for a plane wave field and for constant electromagnetic fields.

We develop a vectorial lattice Boltzmann model with a space-time adaptive relaxation coefficient, combined with adaptive time-stepping for compressible Euler dynamics with generic equation of state. The model, due to special form of the relaxation coefficient devised here is shown to converge to the Euler limit with second-order accuracy in the absence of shocks under acoustic scaling. The solver is robust and able to properly capture compressible gas dynamics for both ideal and non-ideal equations of state, including the Bethe–Zel'dovich–Thompson regime. This is verified and demonstrated through a variety of configurations of increasing complexity.

We study metric-source responses of celestial Einstein amplitudes while retaining their momentum-conservation distribution. The consecutive opposite-helicity response is related to the simultaneous gravitational contact at arbitrary hard multiplicity. Their difference contains a Lorentz transformation that annihilates the conservation delta function, determining the normal recoil contribution and its relation to the undifferentiated coefficient. A six-graviton tree calculation evaluates both coefficients on a real scattering channel. For the summed homogeneous contact, momentum conservation cancels the leading angular singularities. Uniform bounds at coincident soft directions and hard punctures yield integrated endpoint estimates that determine the ordered Mellin residues after smooth source smearing. The mixed Mellin divisor also retains logarithms of soft–hard invariant ratios at generic conformal weight. In Weyl–Beltrami variables, the quadratic reference Ward response combines soft-leg, shadow-map and spin-frame terms into the transported metric Hessian, with a nonzero symmetric mixed susceptibility. Relative shadow primitives require boundary currents when represented across logarithmic cuts; their source variation fixes the accompanying contour contribution. Joint factorization and angular expansions organize the additional NMHV relative-contour terms into residue coefficients that distinguish metric integrability from matching to a specified source functional. An independent vacuum completion supplies the Euler response, which fixed-area harmonic combinations separate from local curvature terms at bounded derivative order.

Solar capture of inelastic dark matter does not by itself fix the annihilation signal. We consider a scalar low-energy model with a $B-3L_\tau$ current, motivated by the high-energy recoil candidate reported by LUX-ZEPLIN. For $m_\chi=840~\mathrm{GeV}$, a $320~\mathrm{keV}$ splitting, and a $160~\mathrm{MeV}$ mediator, the public LZ response gives 0.965 expected accepted events, while micrOMEGAs gives $\Omega h^2=0.11999834$. Finite-momentum nuclear responses leave iron as an important solar-capture target despite the near cancellation of its coherent charge at zero momentum transfer. The captured population remains extended after thermal nuclear motion, elastic and inelastic scattering, and excited-state decay are included, with $r_{\rm eff}=0.215R_\odot$. Same-state annihilation is open, but the inferred rate is only 0.0404 of the public IceCube $W^+W^-$-calibrated proxy and is smaller than the corresponding isothermal estimate by a factor of 628. For this benchmark, substantial solar capture is accompanied by a weak neutrino signal.

We investigate the influence of the Garfinkle-Horowitz-Strominger (GHS) dilaton black hole on different quantum resources of Dirac fields beyond the single-mode approximation. By employing the negativity to characterize quantum entanglement and the $l_1$-norm and the relative entropy of coherence to characterize quantum coherence, we demonstrate that these resources exhibit remarkably different responses to the gravitational field. Specifically, increasing the dilaton parameter continuously suppresses quantum entanglement, leaving only a finite residual amount in the strong-gravity regime, whereas quantum coherence is enhanced, indicating that the dilaton-induced spacetime affects nonlocal quantum correlations and local quantum superposition in fundamentally different ways. Furthermore, we show that an initially maximally entangled state does not always possess the largest negativity after propagating in the GHS dilaton spacetime; instead, under appropriate conditions, certain non-maximally entangled states can retain stronger entanglement than the maximally entangled one. These findings reveal the resource-dependent nature of gravitational effects in dilaton black hole backgrounds and provide new insights into the manipulation and protection of quantum resources for relativistic quantum information processing in curved spacetime.

Recent advances in topological phases have highlighted the role of symplectic (Krein-space) topology in the classification of bosonic Bogoliubov-de Gennes (BBdG) systems. In this work, we construct a BBdG realization of Hopf topology, which we dub the symplectic Hopf insulator, starting from a microscopic Bose-Hubbard generalization of the Moore-Ran-Wen model with weak on-site interactions treated within a Bogoliubov approximation. The resulting BBdG system admits a symplectic Hopf invariant, which we show to be integer-quantized for isolated bands. We establish that this topology is intrinsically delicate, requiring exactly two bosonic modes per unit cell, while remaining robust against weak interactions over a range of mass parameters. Upon terminating the three-dimensional insulator at a boundary, we find topologically protected in-gap surface states at finite excitation energy, whose protection is itself delicate. Our results establish the symplectic Hopf insulator as a robust yet delicate topological phase in weakly interacting bosonic systems lying beyond the tenfold-way classification.

Strong turbulence induces spatial variations in beam intensity that hinder the reconstruction process of many commonly deployed adaptive optics (AO) systems that use gradient-based wavefront sensors (WFS), such as the Shack-Hartmann wavefront sensor (SHWFS) and pyramid wavefront sensor. The nonlinear curvature WFS (nlCWFS) uses Fresnel diffraction to extract wavefront phase and amplitude information, suggesting that it may be able to operate under challenging turbulence conditions. In this work, we investigate nlCWFS reconstruction accuracy as a function of turbulence strength and relative flux by modeling high spherical-wave Rytov number ($R_{sw}$) environments where scintillation and branch points impact sensing performance. We present open-loop as well as static and dynamic closed-loop results benchmarked against a comparable Shack-Hartmann WFS (SHWFS). In static and weak-to-moderate scintillation regimes, the nlCWFS consistently outperforms the SHWFS by leveraging amplitude-phase coupling inaccessible to gradient-based sensors. However, dynamic closed-loop simulations reveal a crossover behavior at higher scintillation strengths, where deep intensity nulls and proliferating branch points degrade the performance of Gerchberg-Saxton-based nlCWFS reconstruction, while the SHWFS degrades more gradually due to its insensitivity to such topological phase structure. These results highlight the regime-dependent advantages of the nlCWFS and emphasize the need for branch-point-tolerant reconstruction algorithms to fully realize its potential in strong-turbulence, low-flux conditions.

Violations of Bell's inequalities offer a definitive signal of non-classical (quantum) behavior in local deterministic systems. Yet, in many physical settings where quantum mechanics is expected to play an important role, one cannot construct a Bell-type test using the available observables. Cosmology offers one concrete example, where cosmic structure may have originated from quantum vacuum fluctuations yet all observations are effectively classical. Nevertheless, recent work suggests that quantum and classical time evolution may still be differentiated by the pattern of statistical correlations of these observables. In this paper, we explore and generalize the use of correlations as Bell-type test of the nature of time evolution. We show that quantum vacuum fluctuations of closed systems undergoing Hamiltonian evolution produce unique correlations that are not mimicked by classical Hamiltonian systems. Correlations in the quantum vacuum are generally time-independent and are controlled by the energy gap between the ground and exited states. Classical systems exhibit apparent poles at physical frequencies that do not arise in the quantum vacuum. As one approaches the poles, the evolution becomes dominated by a resonant Hamiltonian giving rise to time dependent correlations that eventually decay through dephasing. Finally, we show that this behavior is distinct from other signals of quantum evolution, including applications to quantum optics, quantum walks, and quantum search.

We consider the general principles for when deterministic energy harvesting (DEH) is possible. DEH means absorbing energy from a fluctuating source without entropy being absorbed. We show that the symmetry structure of the source–harvester dynamics gives a general route beyond existing examples to identify DEH capable source states. Any continuous symmetry with a conserved Noether charge induces a source-side orbit of states that all implement the same deterministic harvester transition, provided the harvester boundary states are symmetry invariant. Consequently, one DEH capable source state with nonzero asymmetry between charge sectors can generate infinitely many simultaneously DEH capable source states. A Jaynes-Cummings model, a three-spin XX chain, and an SU(2) model illustrate the construction. We further extend Noether's theorem to generalised probabilistic theories and thereby generalise our main result. We further establish an asymmetry bound for harvesting, showing that source asymmetry cannot increase on average, while DEH saturates the bound exactly preserving asymmetry.

Galaxy morphology and kinematics encode complementary information about the assembly history of galaxies, but the extent to which they evolve in tandem remains unclear. Tadpole galaxies, characterized by their distinct head-tail morphology and pronounced asymmetry, provide an ideal laboratory for investigating whether strongly asymmetric galaxies can exhibit ordered galaxy-scale kinematics. In this work, we present a detailed analysis of the ionized-gas kinematics of 20 morphologically selected tadpole galaxies at redshifts $z=0.4 - 1.5$ in the Hubble Ultra Deep Field, using deep VLT/MUSE spectroscopy together with HST and JWST imaging. In 13 out of 20 galaxies, the 2D velocity maps derived from the MUSE [O\,ii] $\lambda\lambda3726,3729$ emission show evidence for ordered motion, characterized by moderate velocity gradients along the kinematic major axis, while the remaining systems show no clear evidence for galaxy-scale ordered kinematics. In 16 galaxies, the [O\,ii] and rest-frame optical emission, probed by HST/F775W, have spatially coincident centroids, with projected offsets of $<2$~kpc. The morpho-kinematic position angles are also generally well aligned, with a median misalignment of $\Delta{\rm PA}\sim12^{\circ}$. Despite the strongly asymmetric tadpole morphologies, these results indicate that a substantial fraction of these systems retain coherent galaxy-scale gaseous kinematics, suggesting that morphological asymmetry need not imply a globally disordered dynamical state. Together, our analyses suggest that morphological and kinematic settlement does not occur simultaneously and these tadpole galaxies might represent a transient evolutionary phase towards the combined morpho-kinematic settlement process.

Consider a one-dimensional branching Brownian motion. Let $W_\infty(\beta)$ denote the limit of the additive martingale in the subcritical regime $\lvert \beta\rvert < \beta_c$ and $Z_\infty$ be the limit of the derivative martingale at criticality. Madaule (Stochastic Process. Appl. 126 (2016), no. 2, 470–502) established the following convergence \[ \frac{W_\infty(\beta)}{\beta_c-\beta}\xrightarrow[\beta\nearrow \beta_c]{\mathbb{P}} 2Z_\infty. \] The goal of this paper is twofold: firstly, we strengthen this result into an almost sure convergence; secondly, we describe the fluctuations occurring in this convergence by proving \[ \frac{1}{\beta_c-\beta}\left( \frac{W_\infty(\beta)}{\beta_c-\beta} - 2 Z_\infty +2(\beta_c-\beta)\log(\beta_c-\beta) Z_\infty\right) \xrightarrow[\beta\nearrow \beta_c]{(d)} S, \] where, conditionally on $Z_\infty$, $S$ follows a spectrally negative 1-stable distribution with scale and shift parameters proportional to $Z_\infty$. Furthermore, these results are extended to the setting of complex additive martingales and the fluctuations to a multi-dimensional convergence.

Point particles are generically ill defined in fully nonlinear general relativity, although they are naturally well defined in linear perturbation theory. In a previous paper, two of us showed how they can be rigorously defined from matched asymptotic expansions at second order in perturbation theory on a generic background spacetime. Here we show how the resulting field equations can be recast in a more practical, more fully “skeletonized” form. We also show that this form of the field equations enables simple derivations of equations of motion. Finally, we show how calculations in second-order perturbation theory can bypass the use of singular “punctures” and make rigorous use of off-the-shelf regularization methods such as Blanchet and Damour's Hadamard regularization, opening new avenues to second-order self-force calculations in black hole binaries.

Private communication over a noisy quantum channel requires reliable transmission to the receiver and secrecy from the environment. Whether two channels with zero private capacity can jointly enable private communication is a longstanding open problem in quantum information theory. Here we resolve this problem by exhibiting a four-level channel and a qubit erasure channel with half erasure probability, each with zero private capacity, whose joint use achieves more than 0.0001903 private bits per product use. The encoding gives the receiver a linear information gain with at most quadratic environmental leakage, enabling privacy through a fixed joint measurement and classical coding. This superactivation, impossible for independent classical memoryless wiretap channels, shows that a channel's private capacity alone does not determine its value for secure communication. The initial activation example was identified through interactions with large language models, and the result has been formalized in Lean 4.

The Jarzynski relation enables the estimation of equilibrium free energy differences from non-equilibrium, finite-time switching simulations. These estimates usually converge poorly because rare trajectories dominate the exponential work average. Here, we numerically determined and explored the sequence of intermediate Hamiltonians connecting initial and final states that minimize the mean squared error (MSE) of the Jarzynski estimator and thereby enhance convergence. For discrete-time Markov models, an exact tilted-master-equation representation of the MSE in the large-sample limit, combined with automatic differentiation, enables efficient gradient-based minimization over all intermediate energies. We applied our approach to three model systems of increasing complexity: a two-state model, a double-well potential, and a shifted potential well. In all three systems, the optimal intermediate Hamiltonians jump at the initial and final times. Extensive Monte Carlo simulations show that optimal intermediates can reduce the MSE by more than an order of magnitude compared with linear and logarithmic interpolation, most strongly for large changes in the energy landscape. Remarkably, they need not dissipate less work than intermediates yielding larger errors. Our results suggest heuristics for more efficient non-equilibrium free energy calculations of realistic molecular systems: optimal intermediate Hamiltonians jump at the initial and final times; for barrier-crossing problems, the barrier should be lowered rapidly and raised again later; and minimizing dissipation does not guarantee faster convergence.

We determine the optimal sample complexity of low-rank quantum state tomography when each measurement may act jointly on at most $t$ samples. For sufficiently small $\varepsilon$, estimating an unknown state on $\mathbb{C}^d$ of rank at most $r$ to trace norm error $\varepsilon$ with constant success probability requires, and is achievable with, $$\Theta\left(\frac{dr}{\varepsilon^2}\mathop{\mathrm{max}}\left\{1,\frac{r}{\sqrt{t}}\right\}\right)$$ samples. The lower bound allows the protocol to choose each joint measurement adaptively using all previous classical outcomes; the matching upper bound is nonadaptive. Thus joint measurements on at most $t$ samples improve the complexity of algorithms making single-sample measurements by at most a factor $\sqrt{t}$. Further, measuring order $r^2$ samples jointly is necessary and sufficient to attain the unrestricted collective rate. For the lower bound, we vary the support of a state with fixed uniform spectrum and bound the Fisher information trace of every joint measurement on $t$ samples. The adaptive Fisher chain rule and the van Trees inequality then give the trace norm lower bound. For the upper bound, we construct and analyze a nonadaptive tomography protocol based on a Gaussian joint measurement. An explicit second moment identity and a conditional Gaussian law outside the state's support give a rank-dependent error analysis, yielding the matching rate.

Interactions of two solitary waves having an up and a down orientation in the modified Korteweg-de Vries equation are shown to produce rogue-like waves. For waves that asymptotically vanish, the maximum ratio between the net peak-to-trough height of the interaction profile and the height of the tallest incoming wave is 2.41 when the waves have approximately equal speeds, and this ratio decreases to 2 when the speed ratio is 2.25. For waves that approach a non-zero constant at infinity, the same ratio is always greater than 2.41 and reaches a maximum of 2.65 when the speed ratio of the waves is 6.32.

We report the observation of positive magnetoresistance in high-mobility GaAs Corbino devices. Over a broad intermediate-temperature range, the resistance exhibits a quadratic dependence on perpendicular magnetic field. We analyze the data within hydrodynamic theories of magnetotransport in the Corbino geometry, which describe the crossover between the diffusive and viscous regimes, including finite-slip boundary conditions appropriate for current-penetrable contacts. The extracted relaxation rates are consistent with an approximately $T^2$ temperature dependence of the electron-electron scattering contribution. The extracted viscous relaxation parameters are consistent with those obtained from Hall-bar measurements. Comparison with theory indicates that the observed magnetoresistance is predominantly governed by the bulk hydrodynamic response, while finite slip modifies the Stokes–Ohm crossover quantitatively and the field-dependent boundary voltage provides a separate correction. These results show that Corbino magnetotransport can serve as a complementary bulk-sensitive probe of viscous electron flow.

In a quantum walk, the first-detection return probability (FDRP) characterizes salient features, determining whether the quantum walk is transient or recurrent. We study the FDRP of quantum walks on a chain where the initial site is stroboscopically monitored by a detector and the walker performs long-range hopping between sites. We assume that the hopping strength decays with the distance $d$ as $d^{-\alpha}$ and $\alpha\geq 0$ and show that the power-law exponent $\alpha$ critically determines the behavior of the FDRP. The value $\alpha=1$ separates recurrent ($\alpha<1$) from transient ($\alpha>1$) quantum walks through a continuous phase transition in the total detection probability. For $\alpha<1$, strong long-range hopping induces localization, resulting in unit total detection probability. Instead, for $\alpha>1$ the long-range walk is transient and the return probability decays algebraically as a function of time as $t^{-\beta}$. The associated decay exponent $\beta$ features nonanalytic points as a function of $\alpha$. Such singularities are not exclusively determined by the low-energy spectrum, but are caused by the interference between infrared and ultraviolet energy modes induced by projective measurements, signalling the emergence of critical behavior intrinsic to the non-unitary dynamics. These dynamics are solely controlled by tuning the long-range exponent $\alpha$ and can thus be experimentally probed in atomic and molecular systems.

Information causality (IC) was introduced as a physical principle constraining correlations in non-signaling theories. Whether it can recover the exact quantum correlation boundary, beyond Uffink's inequality, has remained an open question. Here, we combine its generalized formulation for correlated inputs with a new communication protocol to derive quantum Bell inequalities that exactly characterize the quantum correlations in the simplest bipartite Bell scenario, with two binary measurements. In particular, we derive the Tsirelson-Landau-Masanes criterion directly from IC. Thus, the generalized IC implies macroscopic locality, while we also present macroscopically local correlations that violate the generalized IC. This establishes that generalized IC is a strictly stronger principle in this scenario. Together with our earlier result that generalized IC implies a nontrivial communication complexity principle, these findings strengthen the role of information causality in explaining the limits of quantum nonlocality and provide a systematic route to deriving tighter bounds on the set of quantum correlations in more general Bell scenarios.

We detect a candidate fifth planet in the HR 8799 system, directly imaged with the JWST/NIRISS Aperture Masking Interferometer (AMI). The detected source lies just above a $3\sigma$ contrast curve at a contrast of $\sim2\times10^{-4}$ in the F380M filter at a projected separation of $\sim150$ mas, corresponding to a few-to-several Jupiter mass planet at an orbital radius of $\sim 7$au. The separation of the candidate is compatible with absolute proper-motion constraints from Gaia and Hipparcos assuming it is bound, while its orbital position lies near a stable orbital solution of a fifth planet in a 3:1 mean motion resonance with planet e. This detection was made possible by a new JWST/NIRISS AMI data pipeline that reaches the photon noise limited potential of AMI by accounting for the optical and electronic systematics that limited sensitivity in prior analyses. Confirmation of this candidate would make HR 8799 the first directly imaged five-planet system and provide insight into the orbital dynamics and the dynamical evolution of planetary systems with widely-separated gas giants.