Program 2021

The idea of this summer school is to create a friendly learning atmosphere, to enable open communication between students and lecturers, and create opportunities for students to make lasting contacts with peers at other universities.

Topics for 2021:

Katia Bertoldi, Harvard University
Physics of Flexible Meta-Materials. Mechanical metamaterials exhibit properties and functionalities that cannot be realized in conventional materials. Originally, the field focused on achieving unusual values for mechanical properties that characterize the linear response, such as density, Poisson’s ratio or compressibility, but more recently, new classes of metamaterials that exploit nonlinearities have emerged. These systems exhibit exotic functionalities, such as pattern and shape transformations in response to mechanical forces, unidirectional guiding of motion and waves, and reprogrammable stiffness or dissipation. In this short course, I will give an overview of different kinds of flexible metamaterials, focusing on both their staic and dynamic response. We will also discuss some basic theoretical and computational models that give insight into their behaviors.
Ajay Gopinathan, University of California Merced
Collective Motion in Soft and Biological Matter. Collective motion is an emergent phenomenon that we see in nature, where groups of motile individuals, each possessing only limited, local information, nevertheless come together and display coordinated motion on the group scale. This phenomenon is displayed by systems ranging from soft active matter with purely physical interactions, such as active nematics of microtubules and actin, self-propelled colloids or driven granular matter, to living systems with interactions governed by chemical, auditory and optical sensing such as cells, insects, fish and birds. The fact that collective motility can arise from such disparate interactions and exists across scales from microns to kilometers suggests common underlying principles leading to universal behavior. In this short course, I will give an overview of different kinds of systems that exhibit collective motion with a focus on the important underlying physical interactions and emergent function (for biological systems). We will also discuss some basic theoretical and computational models that give insight into the emergence of collective states and their properties across these different systems. Finally we will discuss new features introduced by the presence of confinement, disorder in the environment and heterogeneity among individuals and their implications for control in active matter and function in biology. 
Wim van Saarloos, Leiden University Non-equilibrium Pattern Formation. In nature, and more specifically in soft matter, there are many examples where a homogeneous system out of equilibrium spontaneously forms patterns with a characteristic scale. Think of cloud patterns, the formation of patterns on the skin of an animal or the wings of a butterfly, or of the emergence of the first structures during morphogenesis. Excitable media, from chemical reactions to nerve propagation or models for the response in the brain, almost invariably exhibit various types of dynamical patterns. Fluid dynamics is also full of examples connected with the classical Rayleigh-Taylor, Rayleigh-Bénard and Kelvin-Helmholtz instabilities. These give rise to the flapping of a flag in the wind with a characteristic frequency, or the formation of convection patterns in fluids heated from below.

In this course I will give an introduction to general framework for describing and analyzing non-equilibrium pattern formation in systems described by continuum equations. After giving an introductory overview of the variety of pattern forming structures mentioned above, we will discuss how many patterns originate from a finite wavelength instability of the dynamical equations for the case under consideration. Above the threshold for such an instability, the system typically exhibits a variety of possible stable patterns with different wavelengths. This brings up the issue of pattern selection, the question which pattern or wavelength is ‘selected’ in practice depending on the nature of the transition, the boundary conditions, the history of the dynamics, etc. The so-called amplitude equation approach, which can be developed just above the onset of the instability, helps to unify the common features in various pattern forming systems and to unravel some of these questions. Connections with the Ginzburg-Landau theory of phase transitions and with bifurcation theory are discussed along the way.

Format:  Due to the covid-19 situation, the 2021 Summer School will be held as a 4-day online event running from Tuesday morning, June 1 to Friday evening, June 4, 2021. Three lecturers will give mini-courses composed of three or four 80-min lectures, plus additional time for discussion. The lectures will be interspersed with opportunities for student presentations, and some online social activities. The Summer School will tentatively run from 10:00am to 4:00pm, Eastern time each day to enable remote participants from as many areas as possible.  The detailed daily schedule will be posted soon, under the “Schedule 2021” tab.

Sound bites: All participants are encouraged to present a short “sound bite” describing the research they are involved in or going on in their research groups.  These sound bites do not need to report new or finished research results, and can be less formal than talks you would present at a regular conference.  We will have several sessions of these sound bites, where you can find out about what is happening at other universities.