Reference for a Heat Process in a Wedge

I would like to ask about an explicit suggestion/reference for the following type of heat processes:

Roughly, assume we have a "wedge" $W$ of the following form - a domain in $\mathbb{R}^n$ with a tip at 0, having some hyperplanes (passing through 0) as sides and, say, the piece of the unit cyllinder/sphere as a bottom. In particular, in the case of $\mathbb{R}^2$ this "wedge" is a sector, i.e. the domain bounded by two rays, shot from 0, and the sphere.

To consider a simple special case, consider the sectorial domain $W = \{ (r, \theta) : r \geq 0, \theta \in [0, \alpha]\}$ in $\mathbb{R}^2$.Consider the following Dirichlet heat equation: $$\partial_t u - \Delta u = 0, x\in W;$$ $$u(t,x) = 0, x\in \partial W, t>0;$$ $$u(0,x) = -1, x\in W.$$

It may seem silly (as this heat process seems rather classical), but I was not able to find a neat explicit reference and formula (even for dim 2). It would help to have a heat kernel expansion (of course depending on the vertex angle $\alpha$). In general, I am looking for references to heat equations with Dirichlet boundary conditions on Euclidean cones.

Many thanks in advance!

• Once you know the eigenfunction of the Laplacian on $W$, you can do a spectral decomposition and everything then follows. – Fan Zheng Dec 14 '15 at 15:10
• Yes, I am aware of that. My point is just to have a neat reference and only use the final result, instead of deriving everything behind the Bessel functions. – Boggie Georgiev Dec 14 '15 at 15:56

1 Answer

Lemma 1 of Brownian motion in cones by Banuelos and Smits gives the Dirichlet heat kernel for generalized cones in $\mathbb{R}^n$ in terms of Bessel functions and spherical harmonics. The paper references page 379 of Conduction of Heat in Solids by Carslaw and Jaeger as a source of a more explicit formula in $\mathbb{R}^2$.