arXiv subjects

Eran Bouchbinder

Publications and source records attributed to Eran Bouchbinder.

At least 19 recordsLinked to original sources

arXiv2026

Lab earthquakes confirm the theory of frictional slip pulses

Large natural earthquakes are typically mediated by frictional pulse-like rupture, which features a finite slipping zone. Recently, a comprehensive two-dimensional theory of frictional slip pulses has been developed. It predicts that pulses are categorically unstable rupture modes, whose evolution is intrinsically slow. Unsteady pulses satisfy an equation of motion expressed in terms of discrete observables, which is inherently related to their steady-state counterparts. The theory also predicts a transition from decaying to slowly growing pulses. Here, we perform extensive lab earthquake experiments to test the theory. The experiments confirm the theoretical predictions for pulse-like lab earthquakes over a range of prestress levels, rupture nucleation conditions and small-scale fault roughness amplitudes. Specifically, the predicted time-dependent dynamics are tested in a plane defined by the evolving pulse size and peak slip rate, along with measurements of the dimensionless growth rate of pulses, demonstrating their intrinsically slow unsteady nature. The predicted transition between decaying and growing pulses is also experimentally demonstrated. These results constitute major progress in understanding a dominant earthquake rupture mode.

physics.geo-ph↗

arXiv2026

Local micromechanics in a mean-field model of glasses reveal key properties of its non-equilibrium RSB phase

A recently formulated mean-field model of glasses features an equilibrium, zero-temperature Replica-Symmetry-Breaking (RSB) transition in some parameter range. In this range, the model's solution in the Replica-Symmetric phase is expressed in terms of an effective, self-consistent random potential for uncoupled degree of freedoms, where the transition to the RSB phase is characterized by the emergence of spectral-edge localized modes and a pseudogapped quartic vibrational spectrum, resulting in a finite spin-glass susceptibility. These properties are preserved in numerical solutions of the model under non-equilibrium conditions, i.e., upon an instantaneous quench. Inspired by recent advances in computer glasses, we define a micromechanical response function --- the linear response to local force monopoles --- in the framework of the mean-field model. We establish exact relations between the force monopole stiffness and global susceptibilities, which suggest a close correspondence between the non-equilibrium RSB phase of the model and the above-mentioned effective random potential description. As such, the obtained micromechanical observables constitute a concrete realization of the collective degrees of freedom of the model, offering a bridge between a glassy mean-field model and finite-dimensional glasses. We show that the model's vibrational spectrum can be computed solely from the monopole response statistics and, by employing a marginal stability criterion, we extract a characteristic frequency/stiffness scale of soft glassy modes, which is related to the boson peak in finite-dimensional, laboratory glasses.

cond-mat.dis-nn↗

arXiv2026

Breakdown of the classical rupture theory and earthquake propagation in the "forbidden" super-Rayleigh range

Earthquakes propagating faster than the shear wave-speed are commonly thought to undergo a super-shear transition upon which they discontinuously jump from the sub-Rayleigh regime to the super-shear one. The super-Rayleigh regime, i.e., the range of propagation speeds between the Rayleigh and shear wave-speeds, is regarded as "forbidden" by the two-dimensional classical rupture theory. Here, we revisit the assumptions underlying the classical theory and develop a rupture theory that takes into account the dependence of the fault strength (frictional resistance) on the slip rate. The theory quantitatively agrees with numerical simulations nearly up to the Rayleigh wave-speed. Yet, very close to the latter, two-dimensional rupture solutions change their character due to frictional rate nonlinearity and rupture continuously propagates through the "forbidden" super-Rayleigh range into the super-shear regime, without a sharp super-shear transition. These results demonstrate that frictional rate dependence, generically observed in experiments, can have profound implications for fast earthquake propagation.

physics.geo-ph↗

arXiv2026

Nonlinear phonon dispersion in disordered solids and non-Debye vibrational spectra

All solids, whether crystalline or disordered, support elastic wave propagation with a linear dispersion relation in the long-wavelength limit. These waves, corresponding to low-frequency phonons, feature a vibrational density of states that follows Debye's classical model. Deviations from Debye's predictions with increasing frequency can emerge from phonon dispersion nonlinearity and from non-phononic vibrational modes, which exist in non-crystalline solids due to structural disorder. Both nonlinear phonon dispersion in disordered solids and its relative contribution to non-Debye anomalies, most notably manifested by the controversial boson peak, remain poorly understood. Here we show that nonlinear phonon dispersion in a broad range of disordered solids, including elastic networks and various glasses, emerge from a mesoscopic, disorder-induced lengthscale, which also controls wave attenuation. We subsequently use analysis and large-scale computer simulations to quantitatively determine the relative contributions of nonlinear phonon softening and non-phononic vibrations to the onset of non-Debye anomalies and to the boson peak. We show that the relative magnitude of the two contributions strongly depends on the strength of disorder of the solid, e.g., controlled by the thermal history upon glass formation, and that for realistic laboratory glasses both pieces of physics significantly contribute to the boson peak. These findings constitute basic progress in understanding disordered solids.

cond-mat.soft↗

arXiv2026

Large dilatational hyperelasticity of glasses en route to cavitation failure

Materials deform elasto-plastically and fail under various loading conditions, typically quantified by the stress triaxiality, which is the ratio between the dilatational (hydrostatic) stress and the deviatoric (shear-like) one. We show that the elasto-plastic deformation of glasses approaching failure qualitatively differ for large and small stress triaxiality levels. Specifically, in the former limit, glasses reveal a strong hyperelastic (nonlinear elastic) response with minute plasticity, largely independently of the quenching rate across the glass transition. Yet, glassy disorder gives rise to significant elastic (reversible) nonaffine deformation, accompanied by the formation of micro-cavities. A small fraction of the latter is irreversible, i.e., survives unloading prior to the onset of failure, and may serve as nucleation sites for failure in the form of large-scale cavitation, involving a topological transition accompanied by the formation of an internal free surface, upon which the glass loses a significant fraction of its load-bearing capacity. These results are contrasted with glass behavior in the limit of vanishing stress triaxiality and their universality across different glass formers is demonstrated. Finally, the implications of our findings for understanding glass deformation and failure under realistic stress conditions are discussed.

cond-mat.soft↗

arXiv2025

Active flow-driven DNA remodeling generates millimeter-scale mechanical oscillations

In living systems, DNA undergoes continuous and rhythmic mechanical remodeling through condensation, looping, and disentangling to regulate gene expression, segregate chromosomes, and guide morphogenesis. Here, we demonstrate a purely mechanical route to rhythmic DNA reorganization in a minimal active composite of microtubules, kinesin motors, and DNA. We embed a DNA polymer in an active turbulent microtubule-kinesin fluid, creating a self-morphing material. The active flows stretch and entangle the DNA, forming a self-organized viscoelastic network that resists active stresses and affects flow over large length scales. This mechanical feedback loop progressively amplifies velocity correlations and drives a nonequilibrium phase transition tuned by DNA contour length: from disordered flow to synchronized, millimeter-scale oscillations with vortices. We rationalize the phase transition with an active-gel model that predicts a growing length scale and an oscillatory instability emerging from the interplay between activity, orientational order, and self-generated viscoelasticity, rather than chemical signaling. The dependence of the oscillation frequency on system size and activity quantitatively agrees with experiment. Thus, flow-driven DNA remodeling provides a minimal physical route to autonomous, system-spanning oscillations in three dimensions and suggests design principles for programmable soft matter that coordinates, actuates, and reshapes itself.

cond-mat.soft↗

arXiv2025

An equation of motion for unsteady frictional slip pulses

Frictional sliding, e.g., earthquakes along geological faults, are mediated either by frictional crack-like ruptures, where interfacial (fault) slip is accumulated during the entire sliding event, or by frictional pulse-like ruptures, featuring a finite length over which slip is accumulated. Our basic understanding of slip pulses, which are believed to dominate most crustal earthquakes, is still incomplete. Here, building on recent progress, we present an analytic equation of motion for rate-and-state frictional slip pulses, which are intrinsically unstable spatiotemporal objects, in terms of a single degree of freedom. The predictions of the equation are supported by large-scale simulations of growing pulses and reveal the origin of the slow development of their instability, which explains the dynamic relevance of pulses in a broad range of natural and manmade frictional systems.

physics.geo-ph↗

arXiv2025

Yielding and memory in a driven mean-field model of glasses

Glassy systems reveal a wide variety of generic behaviors, which lack a unified theoretical description. Here, we study a mean-field model, recently shown to reproduce the universal non-phononic vibrational spectra of glasses, under oscillatory driving forces. The driven mean-field model, featuring a disordered Hamiltonian structure, naturally predicts the salient dynamical phenomena in cyclically deformed glasses. Specifically, it features an oscillatory yielding transition, characterized by an absorbing-to-diffusive transition in the system's microscopic trajectories and large-scale hysteresis. The model also reveals dynamic slowing-down from both sides of the transition, as well as mechanical and thermal annealing effects that mirror their glass counterparts. Finally, we demonstrate a non-equilibrium ensemble equivalence between the driven post-yielding dynamics at fixed quenched disorder and quenched disorder averages of the non-driven system, along with memory formation.

cond-mat.dis-nn↗

arXiv2025

The strain-stiffening critical exponents in polymer networks and their universality

Disordered athermal biopolymer materials, such as collagen networks that constitute a major component in extracellular matrices and various connective tissues, are initially soft and compliant but stiffen dramatically under strain. Such network materials are topologically sub-isostatic and feature strong rigidity scale separation between the bending and stretching response of the constituent polymer fibers. Recently, a comprehensive scaling theory of the athermal strain-stiffening phase transition has been developed, providing predictions for all critical exponents characterising the transition in terms of the distance to the critical strain and of the small rigidity scales ratio. Here, we employ large-scale computer simulations, at and away from criticality, to test the analytic predictions. We find that all numerical critical exponents are in quantitative agreement with the analytically-predicted ones. Moreover, we find that all predicted exponents remain valid whether the driving strain is shear, i.e., volume-preserving, or dilation, and independent of the degree of the network's sub-isostaticity, thus establishing the universality of the strain-stiffening phase transition with respect to the symmetry of the driving strain and the network's topology.

cond-mat.soft↗

arXiv2024

A steady-state frictional crack in a strip

The analogy between frictional cracks, propagating along interfaces in frictional contact, and ordinary cracks in bulk materials is important in various fields. We consider a stress-controlled frictional crack propagating at a velocity $c_{\rm r}$ along an interface separating two strips, each of height $H$, the frictional counterpart of the classical problem of a displacement-controlled crack in a strip, which played central roles in understanding material failure. We show that steady-state frictional cracks in a strip geometry require a nonmonotonic dependence of the frictional strength on the slip velocity and, in sharp contrast to their classical counterparts, feature a vanishing stress drop. Here, rupture is driven by energy flowing to its edge from behind, generated by an excess power of the external stress, and to be accompanied by an increase in the stored elastic energy, in qualitative contrast to the classical counterpart that is driven by the release of elastic energy stored ahead of the propagating edge. Finally, we derive a complete set of mesoscopic and macroscopic scaling relations for frictional cracks in a strip geometry and demonstrate that the stress singularity near their edges is proportional to $(\Delta{v}/c_{\rm r})\sqrt{H}$, where $\Delta{v}$ is the slip velocity rise accompanying their propagation.

cond-mat.mtrl-sci↗

arXiv2024

Unsteady slip pulses under spatially-varying prestress

It was recently established that self-healing slip pulses under uniform prestress $\tau_b$ are unstable frictional rupture modes, i.e., they either slowly expand/decay with time t. Furthermore, their dynamics were shown to follow a reduced-dimensionality description corresponding to a special $L(c)$ line in a plane defined by the pulse propagation velocity $c(t)$ and size $L(t)$. Yet, uniform prestress is rather the exception than the rule in natural faults. We study the effects of a spatially-varying prestress $\tau_b(x)$ on 2D slip pulses, initially generated under a uniform $\tau_b$ along a rate-and-state friction fault. We consider periodic and constant-gradient prestress $\tau_b(x)$ around the reference uniform $\tau_b$. For a periodic $\tau_b(x)$, pulses either sustain and form quasi-limit cycles in the $L-c$ plane or decay predominantly monotonically along the $L(c)$ line, depending on the instability index of the initial pulse and the properties of the periodic $\tau_b(x)$. For a constant-gradient $\tau_b(x)$, expanding/decaying pulses closely follow the $L(c)$ line, with systematic shifts determined by the sign and magnitude of the gradient. We also find that a spatially-varying $\tau_b(x)$ can revert the expanding/decaying nature of the initial reference pulse. Finally, we show that a constant-gradient $\tau_b(x)$, of sufficient magnitude and specific sign, can lead to the nucleation of a back-propagating rupture at the healing tail of the initial pulse, generating a bilateral crack-like rupture. This pulse-to-crack transition, along with the above-described effects, demonstrate that rich rupture dynamics merge from a simple, nonuniform prestress. Furthermore, we show that as long as pulses exist, their dynamics are related to the special $L(c)$ line, providing an effective, reduced-dimensionality description of unsteady slip pulses under spatially-varying prestress.

cond-mat.mtrl-sci↗

arXiv2024

Elementary processes in dilatational plasticity of glasses

Materials typically fail under complex stress states, essentially involving dilatational (volumetric) components that eventually lead to material decohesion/separation. It is therefore important to understand dilatational irreversible deformation -- i.e., dilatational plasticity -- en route to failure. In the context of glasses, much focus has been given to shear (volume-preserving) plasticity, both in terms of the stress states considered and the corresponding material response. Here, using a recently-developed methodology and extensive computer simulations, we shed basic light on the elementary processes mediating dilatational plasticity in glasses. We show that plastic instabilities, corresponding to singularities of the glass Hessian, generically feature both dilatational and shear irreversible strain components. The relative magnitude and statistics of the strain components depend both on the symmetry of the driving stress (e.g., shear vs.~hydrostatic tension) and on the cohesive (attractive) part of the interatomic interaction. We further show that the tensorial shear component of the plastic strain is generally non-planar and also extract the characteristic volume of plastic instabilities. Elucidating the fundamental properties of the elementary micro-mechanical building blocks of plasticity in glasses sets the stage for addressing larger-scale, collective phenomena in dilatational plasticity such as topological changes in the form of cavitation and ductile-to-brittle transitions. As a first step in this direction, we show that the elastic moduli markedly soften during dilatational plastic deformation approaching cavitation.

cond-mat.soft↗

arXiv2024

Testing the Heterogeneous-Elasticity Theory for low-energy excitations in structural glasses

Understanding the statistical mechanics of low-energy excitations in structural glasses has been the focus of extensive research efforts in the past decades due to their key roles in determining the low-temperature mechanical and transport properties of these intrinsically nonequilibrium materials. While it is established that glasses feature low-energy nonphononic excitations that follow a nonDebye vibrational density of states, we currently lack a well-founded theory of these fundamental objects and their vibrational spectra. A recent theory -- that builds on the so-called Heterogeneous-Elasticity Theory (HET) and its extensions -- provides explicit predictions for the scaling of the low-frequency tail of the nonphononic spectrum of glasses, the localization properties of the vibrational modes that populate this tail, and its connections to glass formation history and to the form of the distribution of weak microscopic (interatomic) stresses. Here, we employ computer models of structural glasses to quantitatively test these predictions. Our findings do not support the HET's predictions regarding the nature and statistics of low-energy excitations in glasses, highlighting the need for additional theoretical developments.

cond-mat.soft↗

arXiv2024

Experimental evidence for the $\omega^4$ tail of the nonphononic spectra of glasses

It is now established that glasses feature low-frequency, nonphononic excitations, in addition to phonons that follow Debye's vibrational density of state (VDoS). Extensive computer studies demonstrated that these nonphononic, glassy excitations follow a universal non-Debye VDoS ${\cal D}_{\rm G}(\omega)\!\sim\!\omega^4$, at low frequencies $\omega$. Yet, due to intrinsic difficulties in disentangling ${\cal D}_{\rm G}(\omega)$ from the total VDoS ${\cal D}(\omega)$, which is experimentally accessible through various scattering techniques, the $\omega^4$ tail of ${\cal D}_{\rm G}(\omega)$ lacked direct experimental support. We develop a procedure to extract ${\cal D}_{\rm G}(\omega)$ from the measured ${\cal D}(\omega)$, based on recent advances in understanding low-frequency excitations in glasses, and apply it to available datasets for diverse glasses. The resulting analysis shows that the $\omega^4$ tail of the nonphononic vibrational spectra of glasses is nontrivially consistent with a broad range of experimental observations. It also further supports that ${\cal D}_{\rm G}(\omega)$ makes an additive contribution to ${\cal D}(\omega)$.

cond-mat.dis-nn↗

arXiv2024

Enumerating low-frequency nonphononic vibrations in computer glasses

In addition to Goldstone phonons that generically emerge in the low-frequency vibrational spectrum of any solid, crystalline or glassy, structural glasses also feature other low-frequency vibrational modes. The nature and statistical properties of these modes -- often termed `excess modes' -- have been the subject of decades-long investigation. Studying them, even using well-controlled computer glasses, has proven challenging due to strong spatial hybridization effects between phononic and nonphononic excitations, which hinder quantitative analyses of the nonphononic contribution ${\cal D}_{\rm G}(\omega)$ to the total spectrum ${\cal D}(\omega)$, per frequency $\omega$. Here, using recent advances indicating that ${\cal D}_{\rm G}(\omega)\!=\!{\cal D}(\omega)-{\cal D}_{\rm D}(\omega)$, where ${\cal D}_{\rm D}(\omega)$ is Debye's spectrum of phonons, we present a simple and straightforward scheme to enumerate nonphononic modes in computer glasses. Our analysis establishes that nonphononic modes in computer glasses indeed make an additive contribution to the total spectrum, including in the presence of strong hybridizations. Moreover, it cleanly reveals the universal ${\cal D}_{\rm G}(\omega)\!\sim\!\omega^4$ tail of the nonphononic spectrum, and opens the way for related analyses of experimental spectra of glasses.

cond-mat.soft↗

arXiv2024

Size selection of crack front defects: Multiple fracture-plane interactions and intrinsic lengthscales

Material failure is mediated by the propagation of cracks, which in realistic 3D materials typically involve multiple coexisting fracture planes. Multiple fracture-plane interactions create poorly understood out-of-plane crack structures, such as step defects on tensile fracture surfaces. Steps form once a slowly moving, distorted crack front segments into disconnected overlapping fracture planes separated by a stabilizing distance $h_{\rm max}$. Our experiments on numerous brittle hydrogels reveal that $h_{\rm max}$ varies linearly with both a nonlinear elastic length $\Gamma(v)/\mu$ and a dissipation length $\xi$. Here, $\Gamma(v)$ is the measured crack velocity $v$-dependent fracture energy and $\mu$ is the shear modulus. These intrinsic lengthscales point the way to a fundamental understanding of multiple-crack interactions in 3D that lead to the formation of stable out-of-plane fracture structures.

cond-mat.mtrl-sci↗

arXiv2024

Facet formation in slow three-dimensional fracture

Cracks develop various surface patterns as they propagate in three-dimensional (3D) materials. Facet formation in nominally tensile (mode-I) fracture emerge in the slow, non-inertial regime and oftentimes takes the form of surface steps. We show that the same phase-field framework that recently shed basic light on dynamic (inertial) tensile fracture in 3D, also gives rise to crack surface steps. Step formation is shown to be an intrinsically nonlinear phenomenon that involves two essential physical ingredients: finite-strength quenched disorder and a small, mesoscopic anti-plane shear (mode-III) loading component (on top of the dominant tensile, mode-I loading component). We quantify the interplay between disorder (both its strength and spatial correlation length) and mesoscopic mode I+III mixity in controlling step formation. Finally, we show that surface steps grow out of the small-scale, background surface roughness and are composed of two overlapping crack segments connected by a bridging crack, in agreement with experiments.

cond-mat.mtrl-sci↗

arXiv2024

A finite geometry, inertia assisted coarsening-to-complexity transition in homogeneous frictional systems

The emergence of statistical complexity in frictional systems, manifested in broad distributions of various observables, is not yet understood. We study this problem in velocity-driven, homogeneous (no quenched disorder) unstable frictional systems of height $H$. The latter are described at the continuum scale within a realistic rate-and-state friction interfacial constitutive framework, where elasto-frictional instabilities emerge from rate-weakening friction. For large $H$, such frictional systems were recently shown to undergo continuous coarsening until settling into a spatially periodic traveling solution. We show that when the system's height-to-length ratio becomes small, coarsening is less effective and the periodic solution is dynamically avoided. Instead, and consistently with previous reports, the system settles into a stochastic, statistically stationary state. The latter features slip bursts, classified into predominantly non-propagating small bursts and propagating large bursts, which are non-trivially distributed. The statistical distributions emerge from dynamically self-generated heterogeneity, where both the non-equilibrium history of the interface and wave reflections from finite boundaries, mediated by material inertia, play central roles. Specifically, the dynamics and statistics of large bursts reveal a timescale $\sim\!H/c_{\rm s}$, where $c_{\rm s}$ is the shear wave-speed. We discuss the robustness of our findings against variations of the frictional parameters, most notably affecting the magnitude of frictional rate-weakening, as well as against different interfacial state evolution laws. Finally, we demonstrate a reverse transition in which statistical complexity disappears in favor of the spatially periodic traveling solution. Overall, our results elucidate how relatively simple physical ingredients can give rise to the emergence of slip complexity.

cond-mat.mtrl-sci↗