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Ovidiu Savin

Publications and source records attributed to Ovidiu Savin.

85 records · Page 5Linked to original sources
arXiv2011

Local and global minimizers for a variational energy involving a fractional norm

We study existence, unicity and other geometric properties of the minimizers of the energy functional $$ \|u\|^2_{H^s(Ω)}+\int_ΩW(u)\,dx, $$ where $\|u\|_{H^s(Ω)}$ denotes the total contribution from $Ω$ in the $H^s$ norm of $u$ and $W$ is a double-well potential. We also deal with the solutions of the related fractional elliptic Allen-Cahn equation on the entire space $\mathbb{R}^n$. The results collected here will also be useful for forthcoming papers, where the second and the third author will study the $Γ$-convergence and the density estimates for level sets of minimizers.

math.AP↗
arXiv2011

C^{2,α}$ regularity of flat free boundaries for the thin one-phase problem

We prove $C^{2,α}$ regularity of sufficiently flat free boundaries, for the thin one-phase problem in which the free boundary occurs on a lower dimensional subspace. This problem appears also as a model of a one-phase free boundary problem in the context of the fractional Laplacian $(-Δ)^{1/2}$.

math.AP↗
arXiv2011

$Γ$-convergence for nonlocal phase transitions

We discuss the $Γ$-convergence, under the appropriate scaling, of the energy functional $$ \|u\|_{H^s(Ω)}^2+\int_ΩW(u)dx,$$ with $s \in (0,1)$, where $\|u\|_{H^s(Ω)}$ denotes the total contribution from $Ω$ in the $H^s$ norm of $u$, and $W$ is a double-well potential. When $s\in [1/2,\,1)$, we show that the energy $Γ$-converges to the classical minimal surface functional -- while, when $s\in(0,\,1/2)$, it is easy to see that the functional $Γ$-converges to the nonlocal minimal surface functional.

math.AP↗
arXiv2011

Density estimates for a variational model driven by the Gagliardo norm

We prove density estimates for level sets of minimizers of the energy $$\eps^{2s}\|u\|_{H^s(Ω)}^2+\int_ΩW(u)\,dx,$$ with $s \in (0,1)$, where $\|u\|_{H^s(Ω)}$ denotes the total contribution from $Ω$ in the $H^s$ norm of $u$, and $W$ is a double-well potential. As a consequence we obtain, as $\eps \to 0$, the uniform convergence of the level sets of $u$ to either a $H^s$-nonlocal minimal surface if $s\in(0,\frac 1 2)$, or to a classical minimal surface if $s \in[\frac 1 2,1)$.

math.AP↗
arXiv2011

Density estimates for a nonlocal variational model via the Sobolev inequality

We consider the minimizers of the energy $$ \|u\|_{H^s(Ω)}^2+\int_ΩW(u)\,dx,$$ with $s \in (0,1/2)$, where $\|u\|_{H^s(Ω)}$ denotes the total contribution from $Ω$ in the $H^s$ norm of $u$, and $W$ is a double-well potential. By using a fractional Sobolev inequality, we give a new proof of the fact that the sublevel sets of a minimizer $u$ in a large ball $B_R$ occupy a volume comparable with the volume of $B_R$.

math.AP↗
arXiv2009

$C^{1,\al}$ regularity of solutions to parabolic Monge-Ampére equations

We study interior $C^{1, \al}$ regularity of viscosity solutions of the parabolic Monge-Ampére equation $$u_t = b(x,t) \ddua,$$ with exponent $p >0$ and with coefficients $b$ which are bounded and measurable. We show that when $p$ is less than the critical power $\frac{1}{n-2}$ then solutions become instantly $C^{1, \al}$ in the interior. Also, we prove the same result for any power $p>0$ at those points where either the solution separates from the initial data, or where the initial data is $C^{1, β}$.

math.AP↗
arXiv2008

Minimizers of Convex Functionals Arising in Random Surfaces

We investigate regularity of minimizers in two dimensions for certain classes of non-smooth convex functionals. In particular our results apply to the surface tensions that appear in recent works on random surfaces and random tilings of Kenyon, Okounkov and others

math.AP↗
arXiv2007

On Monge-Ampere equations with homogeneous right hand side

We study the regularity and behavior at the origin of solutions to the two-dimensional degenerate Monge-Ampere equation with homogeneous right hand side of degree alpha, alpha>-2. We show that when alpha > 0, solutions admit only two possible behaviors near the origin, radial and non-radial. We also show that the radial behavior is unstable. For alpha<0 we prove that solutions admit only the radial behavior near the origin.

math.AP↗