Heat trace and heat content asymptotics for Schrödinger Operators of stable processes/fractional Laplacians
Let V be a bounded and integrable potential over Rd and 0 < α ≤ 2. We show the existence of an asymptotic expansion by means of Fourier Transform techniques and probabilistic methods for the following quantities [special characters omitted] and [special characters omitted] as t ↓ 0. These quantities are called the heat trace and heat content in Rd with respect to V, respectively. Here, p((α)/ t)(x, y) and p( HV/t)(x, y) denote, respectively, the heat kernels of the heat semigroups with infinitesimal generators given by (-Δ)(α/2) and HV = (-Δ)(α/2) + V. The former operator is known as the fractional Laplacian whereas the latter one is known as the fractional Schrödinger Operator. The study of the small time behaviour of the above quantities is motivated by the asymptotic expansion as t ↓ 0 of the following spectral functions for smooth bounded domains Ω ⊂ R d, [special characters omitted] where p(Ω,α/ t)(x, y) is the transition density of a stable process killed upon exiting Ω. The function Z((α)/Ω)/)(t) is known as the heat trace and a second order expansion is provided in  for all 0 < α ≤ 2 for R-smooth boundary domains. In  the result is extended to bounded domains with Lipschitz boundary. As for the spectral function Q((α)/Ω)( t), it is called the spectral heat content and has only been widely studied for the Brownian motion case. In fact, a third order asymptotic expansion is provided in  for α = 2. In this work, we will state a conjecture about the second order small time expansion. These expansions differ accordingly to the ranges 1 < α < 2, α = 1 and 0 < α < 1.
Banuelos, Purdue University.
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