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Register a new userNon-equilibrium thermodynamical framework for rate- and state-dependent friction
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Rate- and state-dependent friction law for velocity-step and healing are analysed from a thermodynamic point of view. Assuming a logarithmic deviation from steady-state a unification of the classical Dieterich and Ruina models of rock friction is proposed.
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The dynamics of sliding friction is mainly governed by the frictional force. Previous studies have shown that the laboratory-scale friction is well described by an empirical law stated in terms of the slip velocity and the state variable. The state variable is a function of time, representing the physicochemical details of the sliding interface. Since this law is purely empirical, there has been no unique equation for time evolution of the state variable. Major equations known to date have their own merits and drawbacks. To shed light on this problem from a new aspect, here we investigate the feasibility of periodic motion without the help of radiation damping. Assuming a patch on which the slip velocity is perturbed from the rest of the sliding interface, we prove analytically that three major evolution laws fail to reproduce periodic motion without radiation damping. Furthermore, we propose two new evolution equations that can produce periodic motion without radiation damping. These two equations are scrutinized from the viewpoint of experimental validity and the relevance to slow earthquakes.
A geometric approach to the friction phenomena is presented. It is based on the holographic view which has recently been popular in the theoretical physics community. We see the system in one-dimension-higher space. The heat-producing phenomena are most widely treated by using the non-equilibrium statistical physics. We take 2 models of the earthquake. The dissipative systems are here formulated from the geometric standpoint. The statistical fluctuation is taken into account by using the (generalized) Feynmans path-integral.
While studying systems driven out of equilibrium, one usually employs a drive that is not directly coupled to the degrees of freedom of the system. In contrast to such a case, we here unveil a hitherto unexplored situation of state-dependent driving, whereby a direct coupling exists between the two. We demonstrate the ubiquity of such a driving, and establish that it leads to a nontrivial steady-state that is qualitatively opposite to what is observed in other driven systems. Further, we show how state-dependent driving in a many-body system can be effectively captured in terms of a single-particle model. The origin of this description may ultimately be traced to the fact that state-dependent driving results in a force that undergoes repeated resetting in time.
We study the conformational dynamics within homo-polymer globules by solvent-implicit Brownian dynamics simulations. A strong dependence of the internal chain dynamics on the Lennard-Jones cohesion strength {epsilon} and the globule size NG is observed. We find two distinct dynamical regimes: a liquid- like regime (for {epsilon} < {epsilon}s) with fast internal dynamics and a solid-like regime (for {epsilon} > {epsilon}s) with slow internal dynamics. The cohesion strength {epsilon}s of this freezing transition depends on NG. Equilibrium simulations, where we investigate the diffusional chain dynamics within the globule, are compared with non-equilibrium simulations, where we unfold the globule by pulling the chain ends with prescribed velocity (encompassing low enough velocities so that the linear-response, viscous regime is reached). From both simulation protocols we derive the internal viscosity within the globule. In the liquid-like regime the internal friction increases continuously with {epsilon} and scales extensive in NG. This suggests an internal friction scenario where the entire chain (or an extensive fraction thereof) takes part in conformational reorganization of the globular structure.
We derive the exact formula for thermal-equilibrium spacing distribution of one-dimensional particle gas with repulsive potential V(r)=r^(-a) (a>0) depending on the distance r between the neighboring particles. The calculated distribution (for a=1) is successfully compared with the highway-traffic clearance distributions, which provides a detailed view of changes in microscopical structure of traffic sample depending on traffic density. In addition to that, the observed correspondence is a strong support of studies applying the equilibrium statistical physics to traffic modelling.
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