Minimizers with Vortices of the Ginzburg-Landau functional with Semi-Stiff Boundary conditions.

Minimizers with Vortices of the Ginzburg-Landau functional with Semi-Stiff Boundary conditions.

Thu, 07/06/2012
12:30 		Leonid V. Berlyand (Penn State University) OxPDE Lunchtime Seminar Add to calendar Gibson 1st Floor SR
Minimizers with Vortices of the Ginzburg-Landau functional with Semi-Stiff Boundary conditions.
We study minimizers of the Ginzburg-Landau (GL) functional
\[E_\epsilon(u):=\frac{1}{2}\int_A |\nabla u|^2 + \frac{1}{4\epsilon^2} \int_A(1-|u|^2)^2\]
for a complex-valued order parameter $ u $ (with no magnetic field). This functional is of fundamental importance in the theory of superconductivity and superuidity; the development of these theories led to three Nobel prizes. For a $ 2D $ domain $ A $ with holes we consider “semistiff” boundary conditions: a Dirichlet condition for the modulus $ |u| $, and a homogeneous Neumann condition for the phase $ \phi = \mathrm{arg}(u) $. The principal result of this work (with V. Rybalko) is a proof of the existence of stable local minimizers with vortices (global minimizers do not exist). These vortices are novel in that they approach the boundary and have bounded energy as $ \epsilon\to0 $. In contrast, in the well-studied Dirichlet (“stiff”) problem for the GL PDE, the vortices remain distant from the boundary and their energy blows up as $ \epsilon\to 0 $. Also, there are no stable minimizers to the homogeneous Neumann (“soft”) problem with vortices.
Next, we discuss more recent results (with V. Rybalko and O. Misiats) on global minimizers of the full GL functional (with magnetic field) subject to semi-stiff boundary conditions. Here, we show the existence of global minimizers with vortices for both simply and doubly connected domains and describe the location of their vortices.