The Jeans instability in an unmagnetized, collisionless self-gravitating plasma characterized by a kappa or Lorentzian velocity distribution is investigated in the framework of kinetic and fluid approaches. We have examined the role of suprathermality on the instability threshold wave number and growth rates. The kinetic analysis, based on the linearized Boltzmann-Vlasov and Poisson equations, yields a $\kappa$-dependent dispersion relation and a modified critical Jeans wave number, which reduces to the classical results in the Maxwellian limit ($\kappa \to \infty$) showing their applicability in high-energy tails. Kinetic theory predicts enhanced growth rates and a wider unstable wave number range due to resonant wave-particle interactions in the suprathermal limit (lower $\kappa$ values). In contrast, the fluid description, which incorporates a $\kappa$-dependent equation of state, introduces a modified sound speed and predicts a stabilizing influence of suprathermal populations. Comparison of the two approaches shows that the enhanced growth rate of the kinetic Jeans instability due to suprathermality signifies the importance of kinetic effects in nonequilibrium astrophysical plasmas under specific conditions. The results are discussed in order to understand the role of suprathermality in the gravitational collapse of the warm-hot circumgalactic medium of the Milky Way.

High-density granular active matter is a useful model for dense animal collectives and could be useful for designing reconfigurable materials that can flow or solidify on command. Recent work has demonstrated key similarities and differences between the mechanical response of dense active matter and its sheared passive counterpart, yet a constitutive law that predicts precisely how dense active matter flows or fails remains elusive. Here we study the yielding transition in dense active matter in the limit of slow driving and large persistence times, across a wide range of material preparations. Under shear, materials prepared to be very low energy or “ultrastable” are brittle and well-described by elastoplastic constitutive laws. We show that under random active forcing, however, ultrastable materials are always ductile. We develop a modified elastoplastic model that captures and explains these observations, where the key parameter is the correlation length of the input active driving field. We also observe large parameter regimes where the plastic flow is surprisingly well-predicted by the input active driving field and not highly dependent on the structural disorder, suggesting new strategies for control.

Surface-initiated polymerization on anisotropic templates provides a useful framework for exploring polymerization-driven self-assembly under nonequilibrium conditions. Here, we investigate surface-initiated polymerization-coupled assembly on idealized Janus-polymer-grafted carbon nanotube (CNT) templates using dissipative particle dynamics coupled with a stochastic reaction model. The term “polymerization-coupled assembly” is used in a generic mechanistic sense to describe concurrent surface chain growth and assembly, rather than a direct implementation of a specific experimental PISA protocol. The polymerization exhibits effective first-order kinetics, while aggregation of solvophobic grafted chains leads to diffusion-induced retardation at later stages. By systematically varying the packing fraction $f_p$, aspect ratio $L/D$, and average grafted chain length $n$, we identify distinct nonequilibrium morphologies ranging from lamellar micelles to multilayer vesicles. Multivariate analysis reveals that packing fraction primarily controls assembly size and complexity, aspect ratio governs curvature and orientational ordering, and chain length modulates interlayer spacing and vesicle stability. We further uncover a characteristic “G”-shaped curling pathway during vesicle formation, highlighting the coupling between polymerization kinetics and anisotropic assembly pathways. The model is intended as a qualitative guide for future experiments on anisotropic polymer/CNT assemblies, not as a direct description of an existing experimental system.

Cells in many tissues repel like neighbors over extended ranges, yet standard jamming models ignore this diversity. We introduce chromatic percolation—the percolation of like-type particles driven by extended-range homotypic repulsion in multitype assemblies—and map its relation to mechanical jamming. Using large-scale two-dimensional simulations, we vary the number of particle types and the packing fraction to chart a phase diagram with a mechanical jamming line (J-line) and a geometric percolation line for homotypic clusters (P-line). The jamming threshold increases with diversity and approaches the achromatic limit at large diversity, showing that more diverse systems pack more densely before becoming rigid. Despite this shift, the critical behavior at jamming is unchanged across diversity: residual energy and pressure follow the standard jamming scalings, indicating that the interaction potential—rather than diversity—sets the universality. Homotypic clustering underlies chromatic percolation. At low packing fraction, homotypic contacts dominate, the P- and J-lines nearly coincide, and rigidity and homotypic connectivity arise together. At high packing fraction, heterotypic contacts carry mechanical stability while homotypic connectivity lags; the P-line separates from the J-line and appears as a distinct geometric transition. These results reveal how particle diversity tunes where rigidity onsets while preserving how systems jam. They offer testable predictions for tissues with type-specific interactions and for programmable colloids, and they suggest design routes to materials with tailored mechanical response by controlling diversity and interaction range.

We study underdamped Brownian motion under Poissonian resetting, where we apply two different full resetting procedures. The first one resets both position and velocity to zero, while the second one resets the displacement to zero but takes the velocity after resetting to follow a Maxwell distribution. In both cases, the marginal probability density function (PDF) of the displacement in the stationary state shows exponential tails for large displacements, but the singularities at the mode of the PDF are very different and specific for the corresponding resetting prescription: in the first case, one has $p\left(x\right)\sim {\left|x\right|}^{-1/3}$, while in the second one, one gets $p\left(x\right)\sim -\text{ln}\left|x\right|$. The convergence of the PDF to a stationary one is investigated by examining its excess kurtosis as a function of time. Applying two sets of initial conditions for the second resetting procedure, we show that the behavior of the excess kurtosis for short times is highly sensitive to these.

In even spatial dimensions, solutions of the wave equation violate Huygens' principle, producing a persistent wake tail inside the light cone rather than a sharply localized propagating front. This intrinsic tail complicates refocusing. Here, we examine how the wake-tail structure of the two-dimensional wave equation affects refocusing, using the analytically tractable example of a pulse generated by a source localized in both space and time. Two idealized concentration strategies are considered. A spatial mirror reflects the outgoing pulse and produces refocusing, but the redirected signal is broadened, with the wake tail preserving its causal ordering behind the propagating front. A second strategy employs a time mirror generated by abrupt temporal modulation of the phase velocity, producing temporal reflection and transmission. This mechanism introduces an anticausal response of the wake tail, reversing its temporal ordering in a time-reversal-like manner; however, the pulse still undergoes distortion and wake-tail contributions persist through secondary radiation at the refocus point. These results demonstrate the fundamental connection between Huygens' principle and wave concentration, showing that the wake-tail structure intrinsic to two-dimensional propagation imposes a fundamental limit on perfect refocusing, even under idealized conditions.

We present an analytical model for the frequency response of a gas microbubble oscillating near a spherical inclusion of arbitrary size and mechanical nature (rigid, fluid, or viscoelastic) immersed in a viscous compressible fluid. The model considers both radial and nonspherical oscillations in the linear regime and predicts how their resonance frequencies and oscillation amplitudes are altered by the bubble size, material properties, and distance to the nearby sphere. As a key application, we demonstrate that scanning the frequency response of a bubble near a viscoelastic object, such as an erythrocyte-like particle mimicking a biological cell, offers a way to recover its mechanical properties through inverse modeling, opening new possibilities for high-resolution elastography at the microscale.

This experimental work reinvestigates the breakdown voltage in air for electrode gaps ranging from $0.10$ to $6.00\mu \mathrm{m}$. Rarely addressed in the literature of the field, a special focus is placed on varying the gas humidity and its direct impact on the breakdown voltage. For short distances ($<2\mu \mathrm{m}$), the results confirm significant deviations from the predictions of Paschen's law, with a linear increase of the breakdown voltage. The statistical approach of [B. Disson et al., Phys. Rev. E 112, 015202 (2025)] reveals breakdown characteristics in dry air ($T_{\mathrm{dew}}<-40{}^{\circ }\mathrm{C}$) to be very analogous to the previous results obtained in argon gas. There are—at least—two competing elementary mechanisms responsible to trigger the breakdown: the electrons produced by field emission (FE-mechanism) and the Townsend avalanche (A-mechanism). Breakdowns following the FE-mechanism occur systematically around the electric field value of $E_{\text{FE}}=0.86\mathrm{V}/\mathrm{n}\mathrm{m}$, which is very close to the value measured in argon. Unexpectedly, the gradual increase of humidity in air causes a counterintuitive evolution of the breakdown voltages. While in macroscopic discharges, water molecules in the gas are known to elevate the breakdown voltages compared to dry gas, the admixture of ${\mathrm{H}}_2\mathrm{O}$ drastically reduces the breakdown voltages in microgaps, e.g., $0.86$ to $0.26\mathrm{V}/\mathrm{n}\mathrm{m}$ for dew points of $T_{\mathrm{dew}} <-40{}^{\circ }\mathrm{C}$ and $10{}^{\circ }\mathrm{C}$, respectively. The water layers adsorbed by the surface of the electrodes as well as the formation of a Taylor cone under the effect of the high electric field are discussed. This supports the analysis to understand whether ${\mathrm{H}}_2\mathrm{O}$ enhances the FE-mechanism and A-mechanism or if this is an additional contribution leading to the breakdown. More generally, this study sheds light on the crucial role of humidity in microgap breakdowns and calls into question measurements results reported in the literature where humidity conditions are not documented.

We analyze the behavior of the linear phase of the Rayleigh-Taylor instability (RTI) in the presence of a foam. Such a problem may be relevant, for example, to some inertial confinement fusion (ICF) scenarios such as foams within the capsule or lining the inner hohlraum wall. The foam displays three different phases: by order of increasing stress, it is first elastic, then plastic, and then fractures. Only the elastic and plastic phases can be subject to a linear analysis of the instability. The growth rate is analytically computed in these two phases, in terms of the microstructure of the foam. In the first, elastic, phase, the RTI can be stabilized for some wavelengths. In this elastic phase, a homogenous foam model overestimates the growth because it ignores the elastic nature of the foam. Although this result is derived for a simplified foam model, it is likely valid for most of them. Besides the ICF context considered here, our results could be relevant to many fields of science.

We address issues related to the presence of defects at finite-temperature topological transitions, in particular when defects are modeled in terms of further variables associated with a quenched disorder, corresponding to the limit in which the defect dynamics is very slow. As a paradigmatic model, we consider the classical three-dimensional lattice ${\mathbb{Z}}_2$ gauge model in the presence of quenched uncorrelated disorder associated with the plaquettes of the lattice, whose topological transitions are characterized by the absence of a local order parameter. We study the critical behaviors in the presence of weak disorder. We show that they belong to a topological universality class that differs from those of known statistical models, and in particular different from that of the lattice ${\mathbb{Z}}_2$ gauge models without disorder, in agreement with the Harris criterium for the relevance of uncorrelated quenched disorder when the pure system undergoes a continuous transition with positive specific-heat critical exponent.

Supratransmission is examined in nonlinear lattices with purely nonlinear coupling, extending the phenomenon to systems that lack a linear passband. In contrast to standard lattices with mixed linear-nonlinear interactions, the present model has no linear spectrum, so energy propagation arises entirely from nonlinear effects. Asymptotic analysis yields a discrete $p$-Schrödinger equation that provides an accurate description in the weak- and intermediate-coupling regimes and offers qualitative insight into the strong-coupling regime. Perturbation provides analytical approximations for the critical driving amplitude, explicitly showing its dependence on the driving frequency, coupling strength, and the nonlinearity exponent $p$. The analysis identifies a nontrivial dependence of the critical amplitude on $p$, with distinct trends in different coupling regimes. Numerical continuation and direct simulations validate the theory in regimes where the asymptotic reduction is applicable and show good agreement across a wide range of parameters. The results establish supratransmission in fully nonlinear lattices and clarify the associated energy-transport mechanisms, with relevance to mechanical lattices, tunable metamaterials, and nonlinear optical arrays.

Multispecies ecosystems modeled by generalized Lotka-Volterra equations exhibit stationary population abundances, where a large number of species often coexist. Understanding the precise conditions under which this is at all feasible and what triggers species extinctions is a key, outstanding problem in theoretical ecology. Using standard methods of random matrix theory, I show that distributions of species abundances are Gaussian at equilibrium, in the weakly interacting regime. One consequence is that feasibility is generically broken before stability, for large enough number of species. I further derive an analytical expression for the probability that $N_e=0,1,2,...,$ species go extinct and conjecture that a single-parameter scaling law governs species extinctions. These results are corroborated by numerical simulations in a wide range of system parameters.

Accurate and efficient simulation of open quantum systems remains a significant challenge, particularly for non-Markovian dynamics. We demonstrate the profound utility of expressing the environmental correlation function as a sum of damped sinusoidals within master equations. While not strictly required, this decomposition offers substantial benefits, crucially reducing the cost of Lamb-shift and decay-rate calculations without sacrificing accuracy. Furthermore, this approach enables straightforward calculation of Lamb-shift corrections, bypassing the need for complex principal value integration. We show that these Lamb-shift effects are demonstrably non-negligible in heat transport scenarios and are needed for an accurate description. Unlike in the Gorini-Kossakowski-Lindblad-Sudarshan (GKLS) master equation, the noncommuting nature of the Lamb shift with the Hamiltonian in non-Markovian descriptions, coupled with GKLS's inaccuracies at early times, brings the necessity of non-Markovian descriptions for finite-time thermodynamics. In the weak-coupling regime, our master equation formulations with exponential decomposition achieve accuracy comparable to numerically exact methods. This methodology significantly simplifies and accelerates the simulation of non-Markovian dynamics in open quantum systems, offering a more reliable and computationally tractable alternative akin to a global master equation.

Inspired by the intrinsic organization observed in various biological and physical processes, which manifests through interacting subsystems connected by networks, where particles often compete for limited resources, we study a four-lane network system with a branching-merging geometry under resource-constrained conditions. The particle inflow in the network is regulated by the total number of particles considered in the system, quantified by a filling factor, while conflict between the particle flow at the merging point of the network is captured through a friction parameter. Utilizing mean-field approximations, we obtained the analytical expressions for the stationary-state attributes of the resource-constrained network, such as lane densities, flux, stationary phases, and phase boundaries. The analysis of systems' stationary-state behavior is facilitated by the construction of phase diagrams in the parameter space of the entry-exit rate for two distinct friction regimes. All theoretically obtained findings are validated by the extensive stochastic Monte Carlo simulations based on the Gillespie algorithm under the random sequential update. For a low friction regime, the system can exhibit up to five possible stationary phases, and its phase diagram features a metastable region corresponding to the passage lanes. In this region, the possible stationary phase exhibited by these lanes sensitively depends on the lanes' initial configuration or density, which is corroborated by spatiotemporal plots. In contrast, for a higher friction regime, the system stops exhibiting metastable behavior, and now the phase diagram becomes richer, supporting up to 11 possible stationary phases. In both regimes, the topology of the phase diagrams exhibits non-monotonic behavior in terms of complexity as well as the number of stationary phases as the reservoir feeds more particles to the network system. Lastly, the influence of the boundary rates and the friction parameter is investigated on the position and height of the shock, along with the examination of the finite-size effects, providing an additional insight into the underlying phase transitions of the system.

We investigate energy supratransmission in a boundary-driven two-dimensional nonlinear Schrödinger equation with a central hole. Harmonic forcing with azimuthal modulation generates standing-wave states whose existence and stability depend on the driving amplitude, the inner radius, and the imposed azimuthal charge. Bifurcation analysis shows that small inner radii produce strongly confined states with higher destabilization thresholds, whereas larger radii yield broader profilesand smoother transitions between stable and unstable branches. The cubic-quintic and saturable models exhibit similar qualitative behavior but differ quantitatively in their critical amplitudes and parameter dependence. A variational approximation captures the dependence of the critical drive on the azimuthal charge and nonlinear parameters, and clarifies how the nonlinear response shapes the stationary states near the turning point. Time-dependent simulations show that supratransmission occurs through the emission of localized pulses, with nonzero azimuthal charge triggering symmetry breaking and producing two-dimensional localized excitations (pearls). Isosurface plots provide a complementary view of the resulting radial and angular excursions. These results establish a quantitative framework for supratransmission in two-dimensional geometries and are relevant to driven nonlinear systems in optics, Bose-Einstein condensates, and structured media.

Discrete Ricci curvature serves as a fundamental geometric tool for quantifying the structural characteristics of complex networks, effectively capturing the richness of their connection patterns. Building on this theoretical framework, this paper proposes an improved discrete Ricci curvature algorithm enhanced by information entropy optimization. Through a systematic analysis of the correlation between curvature and node degree in representative network models, we study the intrinsic relationship between Ricci curvature and community structure. Experimental results on multiple real-world networks and the Lancichinetti–Fortunato–Radicchi benchmark model demonstrate that the proposed algorithm adaptively optimizes key parameters, leading to significant improvements in both the accuracy and robustness of community detection. Moreover, it consistently outperforms existing methods across various network scales and mixing parameters.

Biomolecular condensates are cellular phase-separated droplets that usually exhibit a viscoelastic mechanical response, a behavior rationalized by modeling the complex molecules that make up a condensate as stickers and spacers, which assemble into a network-like structure. Condensates usually exhibit a solidification over a long period of time (days), a phenomenon described as aging. The emergence of such a long timescale of evolution from microscopic processes, as well as the associated microscopic reorganization leading to aging, remains mostly an open question. In this article, we explore the connection between the mechanical properties of the condensates and their microscopic structure. We propose a minimal model for the dynamics of stickers and spacers and show that entropy maximization of spacers leads to an attractive force between stickers. Our system displays a surprisingly slow relaxation toward equilibrium, reminiscent of glassy systems and consistent with the liquid-to-solid transition observed. To explain this behavior, we study the clustering dynamics of stickers and successfully explain the origin of glassy relaxation.

Granular segregation is a widespread phenomenon observed in various industrial applications, geophysical processes, and daily life events. It can be driven by multiple mechanisms, and numerous models have been proposed to elucidate this behavior. However, most of these models are phenomenological and qualitative, lacking a unified theoretical framework based on statistical mechanics. Using x-ray tomography, we experimentally investigate granular segregation phenomena in a mixture of particles with different densities under quasistatic cyclic shear. Our findings demonstrate that in regions where particles have sufficient accumulated strain for structural relaxation, their steady-state height distributions can be quantitatively characterized by minimizing an effective free energy based on a segregation temperature that captures the competition between the mixing entropy and gravitational potential energy. We find this temperature coincides with Edwards’ compactivity within error under various pressures and cyclic shear amplitudes. Therefore, we find that granular segregation in quasistatic conditions can be fundamentally explained by an effective granular thermodynamic framework including real energy terms based on the Edwards statistical ensemble.

The work dissipated in pulling a polymer chain with internal friction is numerically calculated by considering a sequence of $N$ spring-dashpots tethered at one end and being pulled at the other using a harmonic trap via linear and symmetric protocols. The variation of the dissipation with the chain length, pulling trap stiffness, and the internal friction parameter are examined in detail for both the protocols. While the dissipation increases with $N$ for chains without internal friction, the relationship between the dissipation and $N$ for chains with internal friction depends on the pulling trap stiffness. For chains with internal friction, the dissipation decreases (increases) with $N$ as the the pulling trap stiffness is increased (decreased), keeping all other parameters constant. Therefore, unlike in the case of a single-mode spring-dashpot ($N=1$) for which a simple relationship exists between the damping coefficient of the dashpot and the dissipated work [as shown in Phys. Rev. Res. 2, 013331 (2020)], the same is not true for the general case of $N>1$ due to the stiffness-dependent dissipative response of bead-spring-dashpot chains.