scholarly journals Induced and endogenous acoustic oscillations in granular faults

2018 ◽  
Vol 377 (2136) ◽  
pp. 20170389 ◽  
Author(s):  
L. de Arcangelis ◽  
E. Lippiello ◽  
M. Pica Ciamarra ◽  
A. Sarracino
Keyword(s):  
Disordered Systems ◽  
Statistical Physics ◽  
Friction Reduction ◽  
Granular Systems ◽  
Acoustic Oscillations ◽  
Frictional Properties ◽  
External Perturbations ◽  
Seismic Fault ◽  
Perturbation Frequency ◽  
Remote Triggering

The frictional properties of disordered systems are affected by external perturbations. These perturbations usually weaken the system by reducing the macroscopic friction coefficient. This friction reduction is of particular interest in the case of disordered systems composed of granular particles confined between two plates, as this is a simple model of seismic fault. Indeed, in the geophysical context frictional weakening could explain the unexpected weakness of some faults, as well as earthquake remote triggering. In this manuscript, we review recent results concerning the response of confined granular systems to external perturbations, considering the different mechanisms by which the perturbation could weaken a system, the relevance of the frictional reduction to earthquakes, as well as discussing the intriguing scenario whereby the weakening is not monotonic in the perturbation frequency, so that a re-entrant transition is observed, as the system first enters a fluidized state and then returns to a frictional state. This article is part of the theme issue ‘Statistical physics of fracture and earthquakes’.

Molecular dynamics simulation of frictional properties of Couette flow with striped superhydrophobic surfaces under different loads

2019 ◽  
Vol 21 (32) ◽  
pp. 17786-17791 ◽  
Author(s):  
Chengzhi Hu ◽  
Dawei Tang ◽  
Jizu Lv ◽  
Minli Bai ◽  
Xiaoliang Zhang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Critical Load ◽  
Couette Flow ◽  
Friction Reduction ◽  
Superhydrophobic Surfaces ◽  
Dynamics Simulation ◽  
Frictional Properties

There was a critical load (Pcrit), such that the friction-reduction of superhydrophobic surfaces appeared only when the load < Pcrit.

scholarly journals Universality of the SAT-UNSAT (jamming) threshold in non-convex continuous constraint satisfaction problems

2017 ◽  
Vol 2 (3) ◽  
Author(s):  
Silvio Franz ◽  
Giorgio Parisi ◽  
Maxime Sevelev ◽  
Pierfrancesco Urbani ◽  
Francesco Zamponi
Keyword(s):  
Constraint Satisfaction ◽  
Disordered Systems ◽  
Statistical Physics ◽  
Degrees Of Freedom ◽  
Universality Class ◽  
Constraint Satisfaction Problems ◽  
Worst Case ◽  
Average Case ◽  
Soft Spheres ◽  
Scaling Solution

Random constraint satisfaction problems (CSP) have been studied extensively using statistical physics techniques. They provide a benchmark to study average case scenarios instead of the worst case one. The interplay between statistical physics of disordered systems and computer science has brought new light into the realm of computational complexity theory, by introducing the notion of clustering of solutions, related to replica symmetry breaking. However, the class of problems in which clustering has been studied often involve discrete degrees of freedom: standard random CSPs are random (aka disordered Ising models) or random coloring problems (aka disordered Potts models). In this work we consider instead problems that involve continuous degrees of freedom. The simplest prototype of these problems is the perceptron. Here we discuss in detail the full phase diagram of the model. In the regions of parameter space where the problem is non-convex, leading to multiple disconnected clusters of solutions, the solution is critical at the SAT/UNSAT threshold and lies in the same universality class of the jamming transition of soft spheres. We show how the critical behavior at the satisfiability threshold emerges, and we compute the critical exponents associated to the approach to the transition from both the SAT and UNSAT phase. We conjecture that there is a large universality class of non-convex continuous CSPs whose SAT-UNSAT threshold is described by the same scaling solution.

scholarly journals New Trends in Statistical Physics of Complex Systems

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 906
Author(s):  
Antonio Scarfone
Keyword(s):  
Complex Systems ◽  
Disordered Systems ◽  
Statistical Physics

A challenging frontier in physics concerns the study of complex and disordered systems. [...]

Friction sensing mechanisms for perception and motor control: Passive touch without sliding may not provide perceivable frictional information

2021 ◽  
Author(s):  
Heba Khamis ◽  
Hafiz Malik Naqash Afzal ◽  
Jennifer Sanchez ◽  
Richard Martin Vickery ◽  
Michael Wiertlewski ◽  
...  
Keyword(s):  
Skin Surface ◽  
Friction Reduction ◽  
Initial Contact ◽  
Textured Surface ◽  
Conscious Perception ◽  
Flat Surfaces ◽  
Passive Touch ◽  
Frictional Properties ◽  
Tangential Forces ◽  
Exploratory Movements

Perception of the frictional properties of a surface contributes to the multidimensional experience of exploring various materials - we slide our fingers over a surface to feel it. In contrast, during object manipulation we grip objects without such intended exploratory movements. Given that we are aware of the slipperiness of objects or tools that are held in the hand, we investigated whether the initial contact between the fingertip skin and the surface of the object is sufficient to provide this consciously perceived frictional information. Using a two-alternative forced choice protocol we examined human capacity to detect frictional differences using touch, when two otherwise structurally identical surfaces were brought in contact with the immobilized finger perpendicularly or under an angle (20 or 30°) to the skin surface (passive touch). An ultrasonic friction reduction device was used to generate three different frictions over each of three flat surfaces with different surface structure: i) smooth glass, ii) textured surface with dome-shaped features, and iii) surface with sharp asperities (sandpaper). Participants (n = 12) could not reliably indicate which of two surfaces was more slippery under any of these conditions. In contrast, when slip was induced by moving the surface laterally by a total of 5 mm (passive slip), participants could clearly perceive frictional differences. Thus making contact with the surface, even with moderate tangential forces, was not enough to perceive frictional differences, instead conscious perception required a sufficient size slip.

scholarly journals The cavity method for community ecology

2017 ◽  
Author(s):  
Matthieu Barbier ◽  
Jean-François Arnoldi
Keyword(s):  
Community Ecology ◽  
Disordered Systems ◽  
Statistical Physics ◽  
Simple Technique ◽  
Cavity Method ◽  
Ecological Communities ◽  
Functional Responses ◽  
Theoretical Ecology ◽  
Systems Approaches ◽  
Volterra Systems

AbstractThis article is addressed to researchers and students in theoretical ecology, as an introduction to “disordered systems” approaches from statistical physics, and how they can help understand large ecological communities. We discuss the relevance of these approaches, and how they fit within the broader landscape of models in community ecology. We focus on a remarkably simple technique, the cavity method, which allows to derive the equilibrium properties of Lotka-Volterra systems. We present its predictions, the new intuitions it suggests, and its technical underpinnings. We also discuss a number of new results concerning possible extensions, including different functional responses and community structures.

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