Speaker
Description
We consider the Ginzburg-Landau energy $E_\epsilon$ for $\mathbb{R}^M$-valued maps defined in a cylinder $B^N\times (0,1)^n$ satisfying the degree-one vortex boundary condition on $\partial B^N\times (0,1)^n$ in dimensions $M\geq N\geq 2$ and $n\geq 1$. The aim is to study the radial symmetry of global minimizers of this variational problem. We prove the following: if $N\geq 7$, then for every $\epsilon>0$, there exists a unique global minimizer which is given by the non-escaping radially symmetric vortex sheet solution $u_\epsilon(x,z)=(f_\epsilon(|x|) \frac{x}{|x|}, 0_{\mathbb{R}^{M-N}})$, $\forall x\in B^N$ that is invariant in $z\in (0,1)^n$. If $2\leq N \leq 6$ and $M\geq N+1$, the following dichotomy occurs between escaping and non-escaping solutions: there exists $\epsilon_N>0$ such that
$\bullet$ if $\epsilon\in (0, \epsilon_N)$, then every global minimizer is an escaping radially symmetric vortex sheet solution of the form $R \tilde u_\epsilon$ where $\tilde u_\epsilon(x,z)=(\tilde f_{\epsilon}(|x|) \frac{x}{|x|}, 0_{\mathbb{R}^{M-N-1}}, g_{\epsilon}(|x|))$ is invariant in $z$-direction with $g_\epsilon>0$ in $(0,1)$ and $R\in O(M)$ is an orthogonal transformation keeping invariant the space $\mathbb{R}^N\times \{0_{\mathbb{R}^{M-N}}\}$;
$\bullet$ if $\epsilon\geq \epsilon_N$, then the non-escaping radially symmetric vortex sheet solution $u_\epsilon(x,z)=(f_\epsilon(|x|) \frac{x}{|x|}, 0_{\mathbb{R}^{M-N}})$, $\forall x\in B^N, z\in (0,1)^n$ is the unique global minimizer; moreover, there are no bounded escaping solutions in this case.
We also discuss the problem of vortex sheet $\mathbb{S}^{M-1}$-valued harmonic maps.
