Papers

Hot subdwarf stars of spectral types O and B (sdO/B) in binaries form as products of substantial mass loss near the tip of the red giant branch and offer powerful constraints on binary-star evolutionary models. However, details of some formation channels remain missing. We present a comprehensive analysis of the short-period binary population in the 500 pc volume-limited sample of hot subdwarfs, enabled by precise Gaia DR3 parallaxes. Besides 45 known binaries within 500 pc, this work identifies 50 new single-lined radial-velocity variable systems, 34 with orbital solutions with periods between 0.07 and 22 days. We derive an overall short-period binary fraction of 34.7 (+2.8/-2.9)% for the full sample of 301 hot subdwarfs within 500 pc, corrected for orbital inclination and detection efficiency. The newly solved binaries predominantly occupy the 1-20 day range, a parameter space previously under-represented in the literature. We identify five new reflection-effect systems, three ellipsoidal modulation systems, a newly solved HW Vir system, and a new triple candidate. The sdB and sdO binary fractions are similar, while the sdOB class shows a fraction roughly half that of sdB/sdO stars, with periods over one day, suggesting a different evolutionary pathway. Underluminous hot subdwarfs below the canonical extreme horizontal branch show a binary fraction comparable to other sdB/sdO stars but host only white dwarf companions, which are more massive and mainly found at periods under one day. We provide the first volume-complete birthrate estimates for sub-populations, determining a Galactic merger rate of 2.5+-1.5x10^-5 yr^-1 for sdO/B binaries, explaining no more than ~12% of the eHe-sdO population. We also derive birthrates for two SN Ia progenitor channels, finding hot subdwarf binaries could account for up to 2.5 (+0.7/-0.5)% of the observed Galactic SN Ia rate.

Recent research grounded in experiments has connected neural ring models of vision to how animals navigate a complex landscape of attractive targets. In this paper we investigate the mathematical and biological implications of a three-stage model where animals pre-process visual stimuli to identify a discrete set of targets, process this input to select the dominant targets, and then post-process this information to navigate the landscape. Incorporating finite target sizes and a neural density allows consistent target acquisition and pursuit reflecting what is seen in nature. Mathematically, we show this model corresponds to an energy minimization problem, simplifying both its analysis and numerical implementation. Biologically, we argue that the model is physiologically motivated, reproduces experimental observations, and presents a fairly direct pathway to decoding neural geometry via empirical data. Our results also demonstrate an analysis pipeline for future model extensions and suggest specific avenues for experimental research to test and parameterize our quantitative framework.

We develop a moisture vorticity theory for the boreal summer quasi-biweekly oscillation (QBWO) in the tropics and analyze it with the aid of GPT-5.5. The model is formulated on a weak-temperature-gradient slow manifold, in which moisture anomalies diagnose the divergent circulation while the rotational circulation evolves through Rossby wave dynamics and vortex stretching. The key coupling is controlled by eddy advection of the background moisture gradient, with the projection $(\mathbf{k}\cdot\nabla\bar q)$ modifying propagation and the cross-gradient factor $(\mathbf{k}\times\nabla\bar q)_z$ controlling moisture extraction and growth. In the weak-coupling regime, which is relevant for the real-world situation, the QBWO is a Doppler-shifted Rossby mode whose growth or decay is determined by phase-coherent moisture extraction and subsequent vortex stretching; moisture damping weakens this feedback but does not introduce a sharp threshold in the minimal linear model. In terms of subtropical geographical locations, this renders the QBWO unstable over the Bay of Bengal with an intraseasonal growth rate and co-located vorticity and moisture anomalies, and it decays over relatively drier regions such as Central and West Africa with a quadrature relation between vorticity and moisture anomalies. The equations also admit a strong-coupling regime where the system approaches a moist-vortex limit. The theory interprets the QBWO as a Rossby-moisture-vorticity instability whose regional behavior depends on background moisture-gradient geometry, coupling strength, damping, and mean-flow advection.

Quantum Monte Carlo simulations confirm the existence of a bound state of a single He-3 atom at a free superfluid He-4 surface in three dimensions, localized within a ~10-A thick low-density He-4 surface layer, with a binding energy of approximately 4 K with respect to vacuum. As the temperature is raised above ~ 1 K the He-3 atom leaves the surface to dissolve into the superfluid. The situation is entirely different in two dimensions, as the He-3 atom is excluded from the superfluid and no surface bound state exists. Results are also presented for the a He-3 atom binding to nanoscale size He-4 clusters adsorbed on weak substrates, a physical system that may allow for the observation of some of the physics predicted for extended surfaces. It is shown that a He-3 bound state localized at the perimeter of sufficiently small (a few tens of atoms) clusters exists not just on Cs, as previously reported, but on all alkali substrates.

A spacecraft closing on a target from three hundred kilometres to contact flies one guidance law across five orders of magnitude of range, and a controller that is provably safe at close range can lose that guarantee completely at long range while continuing to fly as though nothing were wrong. This paper derives the range at which the guarantee lapses and uses it as a design rule. The bound compares the prediction model's own linearisation error against the disturbance set the controller was built to reject, and needs only the sampling period, the orbit and that disturbance bound, so it can be evaluated before any simulation. On a Mars Sample Return approach it disqualifies the homing phase, where most of the propellant is spent, and clears the other two. Re-posing the disqualified phase in relative orbital elements restores the guarantee; re-posing a phase the rule already clears, in a frame two orders of magnitude more accurate, changes propellant by under a tenth of one per cent, and it is that second prediction that makes the rule falsifiable rather than descriptive. The constraint tightening also ties the prediction horizon to feasibility, so the horizon search limit becomes a mission parameter rather than a solver setting. Against a reimplementation of a published benchmark that reproduces its propellant to within one per cent, over five hundred dispersed Monte Carlo transfers per case on matched seeds, the controller saves 29% of the propellant on a circular target orbit and 40% on an eccentric one, docking inside the 0.20 m capture requirement on essentially every draw at a median miss near 5 cm. Two results run the other way: the saving is bought with time of flight and computation, and it comes from what the guarantee demanded of the terminal condition rather than from better disturbance rejection. Recursive feasibility and asymptotic stability are not claimed.

Specialization and task allocation enhance efficiency and innovation across diverse systems, from biological organisms to socioeconomic institutions. The evolution of task distribution and its influence on organizational productivity encapsulate the dynamics between task dependencies and adaptive strategies. We explore the organizational division of labor, inspired by the NK model of rugged landscapes, which is widely applied in evolutionary biology, and incorporate interdependencies among the attributes of technical experts within an organization. Our model considers two types of employees characterized by their task allocation strategies: specialists, who are permanently assigned to a single task, and generalists, who stochastically select a task at each time step. We investigate how the ruggedness of the productivity landscape, shaped by task interdependency, affects the organization's capacity to optimize labor division and meet market demands. Using group selection algorithms, we reveal the emergence of nonlinear adaptive dynamics, providing insights into how companies can adapt their strategies to meet market demands and foster innovation.

The Page–Wootters construction gives time a Hilbert space, representing it as an internal degree of freedom whose readings the rest of the system evolves with respect to. We ask whether such a clock degree of freedom can carry a topological invariant, and we propose a photonic architecture in which it does and in which the invariant can be measured. Signal–idler pairs from spontaneous four-wave mixing in a coupled microring array supply the clock–system partition, with the idler occupying a Rice–Mele band whose staggered coupling and detuning are cycled adiabatically around a gap-closing point. One cycle acts on that band as a rigid translation by \(C\) unit cells, times a geometric phase periodic in the crystal momentum, times a dynamical phase, an identity exact in the adiabatic limit and independent of the state on which it acts. The readout targets the winding of that geometric phase across the Brillouin zone. Reversing the traversal of the pump loop cancels the dynamical phase and isolates twice the geometric phase in a two-photon coincidence fringe, while energy anticorrelation lets a filter on the signal scan the clock momentum without touching the clock and supplies the phase reference relationally, in place of an external optical reference. The estimate is protected on two independent levels, by the gap against smooth deformation and by the digital character of the unwrapping against noise below a threshold. A parameter budget anchored to thin-film lithium niobate places the requirements within reach at a conservative operating point.

Ferroelectric and antiferroelectric phases of LiTaO$_3$ compete under different electric boundary conditions. First-principles density-functional calculations show that the high-symmetry reference structure supports two relevant unstable $\Gamma$ modes: a polar $A_{2u}$ mode at $181i$ cm$^{-1}$ that condenses into the ferroelectric (FE) phase, and an antipolar $A_{2g}$ mode at $103i$ cm$^{-1}$ that condenses into the antiferroelectric (AFE) phase. Under short-circuit conditions the FE phase is the global minimum, with a well depth of $\approx 144$ meV. Under open-circuit conditions the FE phase is destabilized by the unscreened depolarization field and the AFE phase becomes the ground state, with a well depth of $\approx 19$ meV. A weakly unstable longitudinal-optic mode at $48.3i$ cm$^{-1}$ yields a well of only $\approx 0.24$ meV and is thermodynamically irrelevant. Mapping the free energy versus electric displacement $D$ locates a second-order FE$\leftrightarrow$AFE transition at $D_c=0.051$ C/m$^2$, lower than the corresponding $0.07$ C/m$^2$ in LiNbO$_3$ and therefore more accessible experimentally.

The LDA-1/2 method provides an efficient correction to semilocal density functional theory for improving ionization energies and band gaps, yet its application to molecular systems has remained limited. In this work, we present an all-electron finite-element implementation of LDA-1/2 within the NESSIE electronic-structure framework and apply it to the GW100 molecular benchmark set with systematically controllable numerical accuracy. The self-energy correction is constructed explicitly from neutral and half-ionized calculations for each molecule, avoiding the use of precomputed atomic correction potentials. The real-space finite-element formulation enables systematic convergence with respect to the discretization and provides a controlled assessment of LDA-1/2 performance. For the GW100 set, the present implementation yields a mean absolute error of 0.472 eV and a root-mean-square error of 0.645 eV relative to CCSD(T) reference ionization energies, substantially improving upon conventional LDA and the previously reported LAPW implementation of LDA-1/2, while achieving accuracy comparable to G0W0@PBE. Convergence tests show that third-order finite elements are sufficient to reach or approach chemical accuracy relative to higher-order calculations for the representative systems considered. The resulting corrected Hamiltonian also improves several lower lying valence states relative to LDA, although the improvement becomes less systematic away from the HOMO. This work provides accurate LDA-1/2 benchmark data for molecular systems and establishes a rigorous finite-element foundation for future molecular GW calculations.

We establish that vacuum entanglement entropy, regulated by weak spacetime curvature, imposes a fundamental lower bound on radial resolution for quantum excitations. From the area law, weak gravity introduces a natural UV regulator via the perturbative Green's function. Geometric projection yields a minimal radial scale $\Delta r_{\min} \propto r_s^2/R$, where $r_s$ is the Schwarzschild radius and $R$ the boundary radius. Consistency with the Compton wavelength defines a global mass scale $m_{\text{geo}} \equiv \hbar R/(c r_s^2)$. Particle masses satisfy $m = \alpha m_{\text{geo}}$, where $\alpha$ encodes vacuum structure. For Earth, $m_{\text{geo}} \approx 2.84 \times 10^{-32}$ kg. We determine $\alpha$ via spectral analysis of curvature-induced mode shifts, implemented in Python with $N=3000$ radial points and $n_{\text{modes}}=1000$. The calculation yields $\alpha(2) \approx 33$, matching the electron benchmark without adjustable parameters, ruling out exponential ansätze in favor of slow power-law growth $\alpha(l) \propto l^{1.27}$. Crucially, this resolution limit endows the quantum vacuum with the properties of a granular refractive medium. This elegantly explains a fundamental particle-wave asymmetry: massive excitations with $\lambda_C \ll \Delta r_{\min}$ propagate in the geometric optics limit, following macroscopic gradients as classical geodesics. Conversely, photons with $\lambda \ll \Delta r_{\min}$ interact directly with the medium's granularity, leading to phase decoherence and anomalous dispersion. This framework reframes mass as a probe of vacuum-imposed resolution limits, yielding distinct, falsifiable predictions for high-energy photon propagation.

In an optically thin setting, gravitational lensing around a black hole creates multiple delayed images of any localized source, appearing at different positions on the observer's screen. Even if particular sources cannot be singled out, this effect may be revealed in a black-hole movie (time-dependent image) by examining the two-point spatiotemporal correlation function of intensity fluctuations in the movie. Recently, the correlation function derived from a movie obtained by ray tracing of a general-relativistic magnetohydrodynamic simulation demonstrated the plausibility of this idea, even when the movie was blurred to angular resolutions corresponding to next-generation terrestrial very-long-baseline interferometric arrays. In this work, we further develop this method and study how some possible corruptions of the movie, motivated by real observational limitations, affect the ability to identify the extreme-lensing signatures by correlations. The effects are compared for both the original and blurred movies. We discuss the implications of our analysis for upcoming observations of M87* and Sgr A*, the two main targets of the Event Horizon Telescope and its future extensions. Our case study suggests that the types of data corruption we have explored, in themselves, do not preclude an identification of extreme-lensing effects in correlation measurements. We use our results to roughly estimate that, most importantly, for a successful correlation measurement, M87* may need to be continuously monitored for $\gtrsim 2$ years, while Sgr A* may need to be measured at a cadence $\gtrsim 1$ frame per minute. Finally, we outline a new analysis method that reduces the data in the complete correlation function—a large dataset defined on a five-dimensional configuration space—to a two-dimensional histogram that could be useful for black-hole parameter inference.

The interaction between a quantum system and its environment can be characterized by the spectral density function: knowing its structure is important for optimizing applications of quantum technologies such as quantum sensing protocols. In this work, we present the first experimental demonstration of a machine learning-based reconstruction of reaction-coordinate spectral density parameters from NV centre Rabi dynamics. Unlike the previous work, we recover all spectral density parameters rather than only the central frequency, and benchmark the performance of the neural network against the Cramér-Rao bound and maximum likelihood estimator. Our results demonstrate that the model predicted by the neural network can reliably reproduce the NV dynamics over the estimation window, and can produce estimates for some parameters with variances comparable to that of maximum likelihood.

The growing scientific literature contains decades of experimental and computational results that could support data-driven and physics-based modeling, yet much of this infor- mation remains locked in publications and is not readily usable for large-scale analysis or sci- entific software. Building structured databases from the literature is particularly challenging whenrelevantstudiesmustfirstbediscoveredamonglargecollectionsofpapersandreported quantities must be extracted with enough scientific context to remain usable. We present LitCurate, an open-source framework for building scientific databases from the literature using large language models within an auditable, stage-wise curation workflow. LitCurate integratesliteraturediscovery, relevancescreening, full-textprocessing, andstructuredinfor- mation extraction while retaining intermediate results and provenance, allowing researchers to inspect and revise individual stages rather than treating automated curation as a black- box process. We apply LitCurate to construct an equation-of-state database of lower-mantle and lower-mantle-relevant high-pressure mineral phases from experimental and theoretical studies, comprising 1,334 entries from 205 papers. The resulting dataset links reported equation-of-state parameters to mineral phases, compositions, equation formulations, meth- ods, and parameter constraints, and labels values as source-reported or citation-reported when provenance can be determined. The records are available through a searchable web application. By connecting scientific literature to traceable, machine-readable data, LitCu- rate provides a reusable approach for transforming accumulated literature into resources for scientific analysis and computational modeling.

We derive the late-time ramp of the finite-temperature spectral form factor in the double-scaled SYK model directly from cactus diagrams, which is introduced as a multi-trace generalization of chord diagram in Ref \cite{Berkooz:2020fvm}. Although single-trace observables admit an exact chord-diagram description, multi-trace sums are obstructed by the chord-intersection weights $q_{IJ}$, which cannot be averaged independently to $q$. Our key idea is that the non-analytic contribution responsible for the ramp is controlled by the large-order tail of the Cactus-diagram expansion and is insensitive to finite changes in its low-order analytic terms. Decomposing the contribution with $n$-cross-trace-pairings Cactus diagram into two buds $B_n$ and a kernel $\mathcal K_n$, we determine their large-$n$ asymptotics with fixed $0\leq q<1$ and resum the resulting tail. For $\beta_L=\beta+it$ and $\beta_R=\beta-it$, we obtain \begin{equation*} Z_s^{\mathrm{sing}}(\beta+it,\beta-it) =s_p c_N \frac{|t|}{2\pi} \int_{E_{min}}^{E_{max}} e^{-2\beta E} dE+O(1), \qquad s_p=\begin{cases}2,&4\mid p,\\1,&4\nmid p.\end{cases} \end{equation*} This result reproduces the linear ramp predicted by random matrix theory, including its temperature dependence and symmetry factor, and agrees with the semiclassical predictions. It provides a direct microscopic origin of the ramp within the general $q$-deformed quantum algebra. While the plateau lies beyond the scope of the present analysis and calculation.

Quantum DeepONet accelerates neural-operator inference by evaluating an orthogonally parameterized network on a quantum computer, reproducing in ideal simulation the accuracy of its classical counterpart at asymptotically lower inference cost. Its trunk network, however, receives query coordinates with limited spectral structure, requiring the network to learn oscillatory features through its nonlinearities. We propose Quantum SEDONet (Spectral-Embedded Deep Operator Network), which assigns each trunk coordinate a spectral basis according to its boundary condition: Fourier features for periodic coordinates and Chebyshev features for bounded, non-periodic coordinates. The basis is selected per coordinate rather than per problem, allowing both representations within a single problem. Under unary amplitude encoding, the embedding incurs no additional qubits or circuit depth when its dimension remains within the network width, while increasing the parameter count by only a few percent. Across four benchmarks, Quantum SEDONet reduces the mean relative L2 error by 54.1% for the antiderivative, 49.6% for advection, 36.0% for Burgers, and 36.2% for a mixed-boundary channel Poisson problem. Quantum and classical evaluation paths agree to within 10^-8 throughout. The channel Poisson problem simultaneously uses Fourier features in the periodic direction and Chebyshev features in the bounded direction, demonstrating coordinate-wise boundary-matched spectral embedding without additional quantum-resource cost.

A magnetic field that acts identically on two quantum dots is not expected to move charge between them. Nevertheless, we show that a uniform Zeeman field can strongly reconfigure and even reverse the single-electron charge polarization of an asymmetric open double quantum dot. Using a symmetry-preserving Green's-function equation-of-motion approach, we identify regimes where the preferred dot occupation reverses while the system remains in the single-electron charge sector. Two distinct mechanisms produce this behavior. Unequal gate levels produce different occupation responses because the Zeeman-shifted resonances lie at different positions relative to the reservoir chemical potential, whereas unequal onsite interactions distinguish the dots through their many-body addition spectra. Coulomb blockade stabilizes the single-electron sector, causing the reservoir-mediated response to appear as spatial charge redistribution rather than a change in total occupation. Our results establish a mechanism for magnetic control of charge polarization at fixed electrostatic detuning.

I explore Conway's Game of Life (GoL) on six composite Archimedean lattices. On the Kagome lattice, on which small gliders and puffers appear particularly frequently across inputs, I use the output of a symmetry-constrained evolutionary search algorithm to construct a novel glider gun. The glider gun comprises four interacting bouncers and stably emits a small glider every 276th generation. Serving as an extension of classical GoL, I also propose cells with a phase degree of freedom and an associated local phase rule, which on the Kagome lattice is demonstrated to host phase-periodic gliders. This enables the possibility of phase-sensitive and interference-based computations.

Classical Ae stars (CAe) are main sequence, A-type stars with H${\alpha}$ emission but no signature of dust; they are thought to be the cool extension of the classical Be (CBe) stars to lower stellar masses. We investigate the use of H${\alpha}$ and the CaII IR triplet observed at low spectroscopic resolution ($R=1800$) as diagnostics for the circumstellar disks of the CAe stars. Using a sample of 159 CAe stars from the LAMOST survey (DR5), we find that circumstellar disk masses and star/disk viewing inclination angles can be reliably determined from low resolution H${\alpha}$ profiles. The CAe disk mass distribution agrees well with the previous range found for late-type CBe stars, although there is an apparent increase in disk mass for the latest CAe spectral sub-types (A3 and A4) which we attribute to selection effects. Over the spectral range A2 through B6, the average disk-to-star mass ratio for the CAe and CBe stars is consistent with $\log_{10}(M_{\rm disk}/M_*)=-9.1$. A minority of the CAe sample ($\sim$16%) also show emission in the CaII IR triplet. The observed emission is well within the range predicted by the disk models, and there is statistical evidence that the CaII emitters have systematically larger H${\alpha}$ disk masses.

Identifying the smallest set of elements whose removal dismantle a complex network, known as the network dismantling problem, is a fundamental task with many practical applications. Whereas network dismantling has been extensively studied over the past decade, most work has focused on developing efficient algorithms for large but finite networks. By contrast, the physics of the network dismantling process, namely how the network structural connectivity is affected by the removal of nodes or edges, remains largely unexplored in the thermodynamic limit. Here, we shed light on this understudied aspect of network dismantling by introducing an adaptive biased percolation process able to optimally dismantle a network. Through a systematic analysis of synthetic network models, we find that the proposed percolation process displays a universal phase transition, characterized by the abrupt and simultaneous disappearance of both the giant connected component and the largest 2-core, across networks with markedly different degree distributions. Simulations on real networks further support this universality, indicating that the physics of network dismantling is insensitive to a broad range of topological properties. Together, these results suggest that a topology-agnostic theory could be developed to explain the critical behavior of network dismantling.

We present a new age determination of 24 globular clusters (GCs) dynamically associated with the main accretion events experienced by the Milky Way (MW), as part of the Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) project's effort to trace the Galaxy's assembly history. We used deep and homogeneous archival Hubble Space Telescope data, and applied the CARMA isochrone-fitting code to derive homogeneous estimates of age, metallicity, reddening, and distance modulus for systems dynamically associated with Gaia-Sausage-Enceladus (GSE), the Sagittarius dwarf galaxy (Sag), the Helmi streams (H99), and the Sequoia galaxy (Seq). These 24 new determinations are supplemented by 11 previously studied GSE clusters to construct the complete age-metallicity relation (AMR) of the GSE system. We find that each progenitor system describes a well-defined AMR, with a distinct slope and extent reflecting its individual star-formation efficiency and chemical enrichment history. By fitting analytical AMR models within a Markov chain Monte Carlo framework, we quantify the stellar mass and accretion time for each progenitor galaxy. This results in the first detailed merger tree obtained from strictly homogeneous chronological information, according to which the Low-energy-Kraken-Heracles (LKH) system is the first merger experienced by the MW that brought GCs in, followed by Sequoia, H99, GSE, and finally Sgr. The most significant events in terms of stellar mass are LKH, GSE, and Sgr, which together contribute a total of approximately 2.5 x 10^9 solar masses. This corresponds to more than 95% of the stellar mass accreted by the MW from mergers massive enough to host GCs.

The Local Bubble (LB) extends approximately 100–200~pc from the Sun and contains $10^6$~K plasma and warm photoionised gas. Yet the Local Leo Cold Cloud (LLCC) and the Local Ribbon of Cold Clouds lie only 11–24~pc away, well inside the LB, at temperatures near 20~K. How such cold material forms and survives in this hotter environment remains uncertain, and explanations based on colliding warm clouds are difficult to test observationally. We investigate whether LLCC-like gas can assemble locally in a feedback-driven environment or must be imported as pre-existing cold material, and whether it can survive for several Myr. We use magnetohydrodynamic simulations from the SILCC Project including self-consistent star formation, stellar winds and supernovae, ionising and far-ultraviolet radiation, non-equilibrium chemistry, and cosmic-ray transport. We identify cold diffuse gas with $T<100$~K and $0<n_\mathrm{H_2}\leq2$~cm$^{-3}$ and use Lagrangian tracers to reconstruct its assembly, cooling, survival, and dispersal. The simulations produce cold diffuse gas in warm–hot, feedback-driven surroundings, where non-thermal pressure support is crucial. Cosmic-ray pressure remains nearly continuous across cold-gas interfaces and establishes a pressure floor, while magnetic pressure partly offsets the external thermal-pressure excess. The structures persist in the cold diffuse phase for a median of 2.5~Myr, and most of their material remains cold after they lose spatial coherence. The gas can assemble locally from nearby cold and thermally unstable warm material, developing filamentary or sheet-like morphologies. Cooling to $\sim20$~K is driven not by adiabatic expansion but by non-adiabatic cooling. The LLCC therefore need not have entered the LB as an already-formed cold cloud. LLCC-like gas can instead assemble and cool non-adiabatically in situ.

This study continues our ongoing research on contact binary systems by presenting a detailed analysis of 10 targets. Ground-based observations from six different observatories were conducted and used together with TESS data for the analysis process. Photometric data from our observations were reduced with the recently developed AutoWISP pipeline, yielding high-quality light curves with reliable precision for analysis. An investigation of orbital period variations identifies long-term trends in six of the ten analyzed binaries, including three that also display cyclic variations. Four targets show essentially constant orbital periods. The secular trends are attributed to mass transfer. The cyclic modulations in three systems are caused by either magnetic activity cycles or the Light-Travel Time Effect (LTTE) of a third body, while that in the remaining system is solely due to the LTTE. The BSN application was used to model the photometric light curves of the 10 target binaries. Iterative fitting and MCMC refinement provided robust estimates of the system parameters, while starspot modeling was applied for systems showing O'Connell-effect asymmetries. We refine the empirical orbital period-mass relationship for short-period contact binaries by analyzing a homogeneous dataset of systems and deriving an updated primary-mass calibration based on the spectroscopic subset. Using this calibrated relation, the fundamental parameters of the studied systems were subsequently estimated.

We consider that the very early Universe was well described by an Emergent Universe, whose geometry was that of a static and classically stable Einstein Universe, which is possible in certain Two Measures Theories (TMT). These solutions do not have a big bang, but rather they extend to arbitrarily early times. The TMT we consider are theories with spontaneously broken scale invariance and contain a dilaton field, crucial for the implementation of the scale invariance, that after the symmetry breaking acquires a nontrivial effective potential, which we study in the Einstein frame. Using the conserved quantity associated with the dilaton, we recast the cosmological evolution in terms of an effective potential $V(\dot{\phi})$, which exhibits a divergent barrier separating the static solution from the subsequent expanding evolution. Quantizing the corresponding minisuperspace Hamiltonian, we evaluate the tunneling probability in the WKB approximation. The tunneling action is well defined and finite once the branch of the square root is fixed by requiring a consistent semiclassical interpretation of the tunneling probability. We find that the barrier gives rise to a logarithmic contribution to the tunneling exponent, yielding a power-law rather than the usual exponential dependence of the tunneling probability, which for the parameter values considered is close to unity. The Universe thus emerges with a finite scale factor into a superinflationary phase that develops into slow-roll inflation. This quantum creation of an inflationary Universe does not represent a quantum creation of spacetime, which exists before the tunneling.

In dense stellar environments such as globular clusters and active galactic nucleus (AGN) disks, stellar-mass black holes (sBHs) may frequently collide with massive stars. We investigate this process using semi-analytic models, three-dimensional hydrodynamical simulations, and one-dimensional stellar evolution calculations, focusing on collisions between sBHs and a $100\,M_\odot$ main-sequence star. We find that gas drag retains the BH within the stellar envelope unless the impact velocity exceeds $\sim2\sqrt{G(M_\star+M_\bullet)/R_\star}$. The post-collision outcome depends primarily on the BH-to-star mass ratio. For $M_\bullet\gtrsim30\,M_\odot$, the retained envelope is either quasi-spherical or disc-like, but remains dynamically unstable because of shock heating. In contrast, for $M_\bullet\lesssim10\,M_\odot$, the collision forms a “black hole star” (BH*): a quasi-hydrostatic, extended stellar envelope surrounding the embedded BH. These results agree with our analytic prediction that BH* formation necessarily requires $M_\bullet\lesssim0.2\,M_\star$. Follow-up MESA calculations further show that, for these low-mass BHs, the shock-heated remnant thermally relaxes without triggering runaway expansion. We discuss several astrophysical implications of BH*s, including their evolution, the possibility of gravitational-wave events from BH binaries assembled within a stellar envelope, and repeated star–sBH collisions as a pathway for rapid BH growth in dense stellar systems. This mechanism may contribute to the formation of massive BHs in high-redshift nuclear star clusters and may be relevant to the origin of the “little red dots” discovered by JWST.

The rapidly accumulating discoveries of binary stellar-mass black-hole (sBH) coalescences, detected by LIGO, have opened a new window into the formation and evolution of compact binaries. In particular, residual orbital eccentricity may provide a distinctive signature of their formation channels. Here, we investigate a scenario in which high-eccentricity compact binaries form through the sequential capture of multiple sBHs by massive main-sequence stars, using a combination of hydrodynamical and semianalytic few-body simulations. We find that sBHs with $M_\bullet\lesssim 0.2\,M_{\star}$ can be captured by massive stars and settle into a quasi-hydrostatic black-hole star (BH*) through gas dynamical friction. A subsequent encounter with a second sBH can then produce a compact binary embedded within the stellar envelope. Our hydrodynamical simulations show that through captures with small impact parameter, some binaries are born with high eccentricity ($e\gtrsim 0.5$), with its orbital frequency already entering the LISA band. Our semianalytic models further demonstrate that gas dynamical friction can pump the eccentricity to $e_{\rm 10\,Hz}>0.9$ before gravitational-wave emission eventually circularizes the binary during the final stage of coalescence. Once formed, the binary can merge quickly in $\sim 10$ hours. This channel may operate in dense stellar environments, such as star clusters and active galactic nucleus (AGN) disks. The same mechanism can also be applied to Thorne-Żytkow objects. A high-eccentricity binary in the LIGO band could therefore provide a distinctive signature of this formation scenario.

We develop a positive-geometric formulation of tree-level Yang-Mills correlators in de Sitter space at three and four points through their helicity-stripped representatives on the cosmological Grassmannian. In its Pfaffian (or spinor) embedding, physical singularities become natural geometric boundaries. At three points, the Yang-Mills correlator is the canonical form of the non-negative orthant in the Grassmannian. At four points, the Mandelstam divisors partition the Pfaffian-positive domain of the Grassmannian into four positive geometries. Requiring factorization into three-point forms, together with the correct flat-space limit, uniquely selects an oriented union of two of these regions, whose canonical form reproduces the reduced color-ordered Yang-Mills correlator. The full color-ordered correlator, on the other hand, arises from a uniquely fixed signed linear combination of homology cycles. Thus, the broader homological formulation of positive geometry is essential for capturing the complete four-point result. Our construction provides a concrete starting point for a geometric description of higher-point cosmological correlators.

Minimum-cost orders of commuting phase terms can produce substantially different routed circuits. On the same 36-term instances, three orders with identical support cost 74 yield mean routed depths of 228.6, 233.8, and 256.7. We exploit this degeneracy under fixed placement and maintained-parity lowering: Stage 1 attains the support optimum, and Stage 2 selects minimum routed depth among 24 equal-cost orders. For distinct pair supports, we characterize orders attaining the support lower bound through Hamiltonian paths of the support line graph and count optima exactly through 20 terms. On synthetic 16-qubit assignment-Ising instances, selection reduces depth by 12.83% under a different SABRE routing seed, with lower depth in all 20 instances. The selected orders lie a median 1.57 pool standard deviations below the pool mean, consistent with ordinary best-of-24 selection; the useful feature is that candidate rankings persist across routing seeds. Depth reductions extend to 48 terms and a random-MaxCut generator, whereas evaluation with BasicSwap reverses the gain. A 40-instance IBM Heron study measures a 0.59% error reduction on the executed stabilizer-probe panel, but the primary confidence interval across instances includes zero. Plateau selection therefore improves routed depth in the tested SABRE pipeline while preserving the logical support optimum.

Inferring elastic constants from resonant ultrasound spectra is a nonlinear and typically overdetermined inverse problem based on finite spectral data. We formulate the Rayleigh-Ritz inverse problem as a constrained inverse-isospectral problem on the set of physically admissible elasticity tensors. This induces effective low-dimensional variables for the inverse map on the admissible elasticity manifold: length and elastic scales, aspect-ratio coordinates, scale-free spectral features, and stability-respecting elastic ratios. We use these variables to construct a physics-informed learning pipeline in which a regression model acts only on reduced spectral and geometric features, while scale recovery and final elastic-constant reconstruction are imposed analytically. For the full cubic benchmark, the reconstructed constants have MAE values of $20.37(35.15)$, $24.30(41.33)$, and $2.13(3.66)~\mathrm{GPa}$ for $C_{11}$, $C_{12}$, and $C_{44}$. In the fixed-geometry benchmark, the corresponding cubic MAPE values are $4.14(3.87)\%$, $8.31(8.50)\%$, and $2.44(2.86)\%$, while the isotropic values are $4.0(3.6)\%$ and $0.4(0.3)\%$ for the bulk and shear moduli. The inverse problem then becomes a constrained regression problem in variables adapted to the geometry, scaling, crystal symmetry, and thermodynamic stability of Hookean elasticity.

The fracture response of body-centered-cubic tungsten is governed by competition between crack-tip instability and dislocation-mediated plastic accommodation. Molecular dynamics (MD) simulations are used to examine edge-cracked polycrystalline W and W-Re under displacement-controlled Mode-I tension from 300-1800 K at a strain rate of 5 x 10^8 s^-1. Heating pure W reduces the instability stress, effective specimen stiffness, and pre-instability volumetric work density, while the instability strain remains comparatively scattered. A normalized work-loss metric derived from the pre-instability work gives a broad sigmoid crossover marker, T*_MD ~ 870 K, characteristic of the simulated geometry and high-rate loading conditions. Among the available W-Re compositions, W-10Re shows greater pre-instability deformation and work accumulation than pure W across most temperatures, while the maximum-stress response remains strongly temperature- and composition-dependent. Changes in retained dislocation character and near-tip activity indicate that Re modifies the crack-tip plastic-accommodation pathway rather than producing a simple strength increase. Common-state analysis further shows that Re alters the retained 1/2<111> line character and the temporal distribution of near-tip dislocation activity without uniformly increasing the local dislocation population. These coupled mechanical and defect-structure changes provide atomistic indicators of a high-rate ductile-to-brittle transition (DBT), but not a direct prediction of experimental DBTT. A separate OpenDiS/pydis calculation demonstrates source-like bow-out and heterogeneous dislocation-network development in crack-free polycrystalline W, providing mesoscale context without implying direct quantitative MD-DDD coupling.

We study the quench dynamics of graphene, without and with a staggered mass, following the sudden switch-on of circularly polarized light where coupling to a fermionic bath is also considered. Using an armchair nanoribbon, we compute the period-averaged bond current near the edge at successive stroboscopic times. For the isolated system, the current oscillates around a dc value which, we analytically show, equals the Floquet band currents weighted by their projected occupations; a nonzero dc current signals an induced topological phase. When coupled to a bath with a finite coupling, the current and conductance initially increase and then saturate, indicating a nonequilibrium steady state. In the limit of vanishingly small coupling, the period-averaged conductance becomes quantized after summing over bath chemical potentials shifted by integer multiples of the driving frequency, revealing the number of edge modes crossing the zero-quasienergy gap and the Floquet zone boundary gap. We support these results by computing the two-terminal conductance of a finite-size tight-binding model under a three-step driving protocol; the bond conductance after applying the sum rule corroborates our findings.