Focus areas

The following topics are a rough guide for potential fields of discussion. They are not exclusive and other topics are very welcome.

Universality in avalanche dynamics

Much effort has been invested to classify different systems exhibiting avalanche dynamics into universality classes regarding the underlying nature of disorder, symmetries of the system, and the specific features of the interaction kernel (short or long ranged, strictly positive or with altering signs). This session aims at clarifying the conditions under which universality can be expected and explores reasons for non-universal features in avalanche dynamics such as the presence of inertia, transient phenomena and other situations where avalanches still play a dominant role for the overall dynamics.

Mixing of avalanches

When a slowly driven system responds by intermittent bursts of activity, instability may arise not only to one but to several mechanisms simultaneously. This mixing of avalanches leads to ’order parameter coupling’ and several catastrophic events can also occur simultaneously (depinning, yield, porous collapse etc). In case of crystalline plasticity, for instance, where two types of fluctuations coexist, i.e. avalanches as well as „non-critical” (mild) fluctuations, the mixed dynamics can give rise to non-universal exponents. In this session we discuss the latest results of this newly emerging field.

Precursors of catastrophic events

Forecasting failure has an utmost importance to mitigate the consequences of the collapse of engineering constructions and of natural catastrophes like landslides, earthquakes, volcanic eruptions, rock and snow avalanches. One possible solution of the problem is to identify precursors of the imminent large event in time series of avalanches. The session is dedicated to discuss the experimental and theoretical efforts of the search of avalanche precursors in a large variety of systems.

Avalanches in transient dynamics

Some first works are now concentrating on avalanches in transient dynamics instead of being interested in the stationary state dynamics. In many cases this dynamics appear not to be critical, but they are nevertheless in some situations still governed by avalanche type events. This session will concentrate on the specific role of initial conditions and parameter dependence on the avalanches in the transient dynamical regimes, a topic very important for applications where transient dynamics are ubiquitous.

Experimental methods to investigate avalanche phenomena

Experimental studies on avalanche phenomena are dominated by the use of acoustic emission (AE) techniques. Different „imaging” methods such as image correlation, diffusing wave spectroscopy, … can give a more direct quantification of strain fields and avalanches, though generally at a lower sampling rate compared to AE, complementing one another. Recently, the ferroics community has been increasingly using depolarisation currents to obtain information about the intermittent propagation of phase fronts. In martensites the application of stress drop techniques is essential. The session will concentrate on the advantages and limitations of experimental methods, and in particular on their effect on the outcome of measurements.

Models of avalanche dynamics

The development of mesoscopic models, such as fiber bundle models, spring block models, discrete element and mesoscopic elasto-plastic models, ferroelastic and spin models, birth-death processes and various other coarse grained descriptions can help in understanding better the basic mechanisms in avalanche dynamics. This session will focus on recent advances in these modeling approaches to reveal their strength and weaknesses for the understanding of avalanche phenomena.

Yielding transition

The yielding transition has been quite controversial with respect to its belonging in a specific universality class, especially the belonging to the depinning universality class has been shown to be questionable. Depending on the observables considered and the dynamical regime of interest the reasoning can be very different. This session is to identify the necessary numerical (and experimental) tests needed to converge the understanding of this strongly debated topic.

Multi-ferroic switching

Multi-ferroics are materials which exhibit more than one of the ferroic properties (ferromagnets, ferroelectrics, ferroelastics) in the same phase, and their magnetization, polarization, or deformation are switchable by an external magnetic or electric fields, or by external stress. A newly emerging field of avalanche phenomena is the study of the switching behaviour of multi-ferroics, in particular ferroelectrics, which can be described by the depinning transition up to some extent. This session will focus on the recent experimental and theoretical achievements of the study of the avalanche dynamics accompanying multiferroic switching, and on avalanches related to topological defects in (multiferroic) materials such as domain walls, vortices, skyrmions, hopfions, etc.

Other systems exhibiting avalanche dynamics

Beyond the above examples there exists a large variety of systems exhibiting avalanche dynamics, as in the case of neural networks, in social sciences, or in solar flare dynamics. This session aims to promote knowledge transfer between such widely different fields and to enhance understanding of avalanches in a broader framework.