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The Laplacian matrix is the representation of a graph in matrix form.

7 votes
1 answer
510 views

Eigenvalues of the Laplacian on surfaces with boundary

Here, $\lambda_1(\Sigma,g)$ denotes the first eigenvalue of the Laplacian associated to the metric $g$ with Dirichlet ($=0$) boundary condition. …
Eduardo Longa's user avatar
7 votes
0 answers
122 views

Steklov eigenvalue for circle valued functions

Let $(M,g)$ be a compact Riemannian manifold with boundary. It is well known that the first positive Steklov eigenvalue $\sigma_1$ of $M$ has the following variational characterization: $$\sigma_1(M,g …
Eduardo Longa's user avatar
4 votes
0 answers
161 views

Upper bound for the first eigenvalue of the Laplacian on surfaces with boundary

\Lambda(\Sigma) := \sup \{ \lambda_1(\Sigma,g) \operatorname{Area}(\Sigma,g) : g \text{ is a smooth Riemannian metric on $\Sigma$} \}$$ where $\lambda_1(\Sigma,g)$ denotes the first eigenvalue of the Laplacian
Eduardo Longa's user avatar
3 votes
0 answers
78 views

Dirichlet-to-Neumann map is analytic

Let $M^n$, $n \geq 2$, be a compact smooth manifold with boundary and let $I \ni t \mapsto g_t$ be an analytic (with respect to t) $1$-parameter family of Riemannian metrics on $M$. For each $t \in I$ …
Eduardo Longa's user avatar
2 votes
1 answer
210 views

Are these the only first eigenfunctions on a hemisphere?

It is well known that the first positive eigenvalue of the Laplacian on the closed unit sphere is $2$, and the associated eigenfunctions are the coordinate functions $x,y,z$ restricted to the sphere. … I wonder if the functions $x$ and $y$ generate the first eigenspace of the Laplacian the upper hemisphere with Neumann boundary condition. …
Eduardo Longa's user avatar
2 votes
0 answers
93 views

Dimension of Laplacian eigenspaces along a smooth 1-parameter family of metrics

For a smooth 1-parameter family $g_t$, $t \in (-\varepsilon, \varepsilon)$, of Riemannian metrics on $M$ with $g_0 = g$, let $\lambda_k(t)$, $k=0,1,2, \dots$ be the eigenvalues of the Laplacian $\Delta …
Eduardo Longa's user avatar
2 votes
1 answer
159 views

Maximizing the first Neumann eigenvalue on disks

Let $D^2$ be a smooth disk and for any Riemannian metric in $D$, let $\mu_1(g)$ be the first positive Neumann eigenvalue of the Laplacian on $(D, g)$. …
Eduardo Longa's user avatar
1 vote
1 answer
83 views

Infimum of the normalized Laplacian eigenvalues

The spectrum of the Laplacian operator $\Delta_g = -\operatorname{div} \nabla$ consists of an increasing and diverging sequence of positive eigenvalues: $$0 = \lambda_0(M,g) < \lambda_1(M,g) \leq \lambda …
Eduardo Longa's user avatar