Upcoming Thesis Defenses

TD

The Shape of Soft Matter: Geometry and Defects by Francesco Serafin

Jul 23, 2019, 2:00 PM-4:00 PM

Room 202/204 Physics Bldg.

Advisor: Prof. Mark Bowick

How does shape emerge at macroscopic scales from the spontaneous self-organization of building blocks at smaller scales? In this talk, I will address this question in the context of closed soft two-dimensional membranes with internal order. Soft matter represents a good arena to identify simple universal mechanisms for shape selection. In fact, a distinctive property of soft materials is that they can undergo dramatic changes in geometric conformation at relatively low energetic cost. Thus, shape itself becomes a statistically fluctuating degree of freedom, and in some cases it can be found as the ground state of an appropriate free energy functional.

The building blocks of soft materials typically have lower symmetry than elementary point particles and exhibit rich patterns of spontaneous ordering as the free energy of the system is lowered. Order is frustrated if the membrane’s topology is non-trivial, and topological defects are forced to exist even in the ground state. I will argue that the presence of defects in closed 2-dimensional membranes with liquid-crystalline order enable to predict the existence of surprisingly sharp, faceted yet extremely soft polyhedral ground-state shapes.