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Partial differential equations (PDEs): Existence and uniqueness, regularity, boundary conditions, linear and non-linear operators, stability, soliton theory, integrable PDEs, conservation laws, qualitative dynamics.

8 votes

First eigenvalue of the Laplacian on a regular polygon

For $N \geq 5$ it is still not known if the $N$-gon which minimizes the first eigenvalue under area constraint (which exists), is the regular one. I have done some numerical computations which suggest …
Beni Bogosel's user avatar
  • 2,222
7 votes

A long-lasting conjecture of Pólya & Szegő

Together with D. Bucur we propose a strategy which could prove the conjecture for a fixed $n \geq 5$ using a finite number of certified numerical computations. Our paper can be found here: On the poly …
Beni Bogosel's user avatar
  • 2,222
6 votes
1 answer
636 views

Eikonal equation - Snell's law

I am interested in equations of the form $|\nabla d|= F(x)$, where $F(x)$ is piecewise constant and $d(x) = 0$ on $\Gamma_D$, a subset of the boundary. In particular, like in the figure, one can consi …
Beni Bogosel's user avatar
  • 2,222
5 votes
1 answer
507 views

$C_0$-semigroups applications

My graduation thesis was about stability theorems for $C_0$-semigroups (see the Wikipedia article for the definitions: http://en.wikipedia.org/wiki/C0-semigroup). I would like to know if there is som …
Beni Bogosel's user avatar
  • 2,222
2 votes
0 answers
114 views

Reference request – a priori estimate – mixed boundary condition

I am interested in finding references regarding estimates of the form $$ \| D^2 u\|_{L^2(\Omega)} \leq C(\|f\|_{L^2(\Omega)}+\|g\|_{S} )$$ where $\|D^2 u\|_{L^2(\Omega)}^2 = \sum\limits_{i,j \in \{1,2 …
Beni Bogosel's user avatar
  • 2,222
2 votes
0 answers
175 views

A limit involving a regularizing kernel

I am studying the following article by Benoit Perthame: http://www.mendeley.com/research/uniqueness-error-estimates-first-order-quasilinear-conservation-laws-via-kinetic-entropy-defect-measure/# Some …
Beni Bogosel's user avatar
  • 2,222
2 votes
1 answer
878 views

Weak divergence implies weak differentiability of components?

Suppose $\Omega$ is an open set in $\Bbb{R}^N$ and $\sigma : \Omega \to \Bbb{R}^N$ is a field with all components belonging to $L^2(\Omega)$. We say that $\sigma$ has weak divergence if there exists …
Beni Bogosel's user avatar
  • 2,222
2 votes

First eigenvalue of the Laplacian on a regular polygon

Some recent activity on the problem: Results regarding the Hessian matrix with respect to vertex coordinates, numerical local minimality estimates and analytical bounds on the diameter of the optimal …
Beni Bogosel's user avatar
  • 2,222
1 vote

Spectrum of Dirichlet Problem for Laplacian on a Parallelogram

This may not be what you wish for, but here is a list of the first $10$ eigenvalues calculated numerically for the rhombus with sidelength $1$: $$\begin{array}{c}24.8982\\ 52.6379\\ 71.7085\\ …
Beni Bogosel's user avatar
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