Heat coefficient $a_4$ for nonminimal Laplace type operators

Abstract : Given a smooth hermitean vector bundle $V$ of fiber $\mathbb{C}^N$ over a compact Riemannian manifold and $\nabla$ a covariant derivative on $V$, let $P = -(\lvert g \rvert^{-1/2} \nabla_\mu \lvert g \rvert^{1/2} g^{\mu\nu} u \nabla_\nu + p^\mu \nabla_\mu +q)$ be a nonminimal Laplace type operator acting on smooth sections of $V$ where $u,\,p^\nu,\,q$ are $M_N(\mathbb{C})$-valued functions with $u$ positive and invertible. For any $a \in \Gamma(\text{End}(V))$, we consider the asymptotics $\text{Tr} \,a \,e^{-tP} \sim_{t \downarrow 0} \,\sum_{r=0}^\infty a_r(a, P)\,t^{(r-d)/2}$ where the coefficients $a_r(a, P)$ can be written as an integral of the functions $a_r(a, P)(x) = \text{tr}\,[a(x) \,\mathcal{R}_r(x)]$. This paper revisits the previous computation of $\mathcal{R}_2$ by the authors and is mainly devoted to a computation of $\mathcal{R}_4$. The results are presented with $u$-dependent operators which are universal (i.e. $P$-independent) and which act on tensor products of $u$, $p^\mu$, $q$ and their derivatives via (also universal) spectral functions which are fully described.
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Contributor : Thierry Masson <>
Submitted on : Tuesday, January 8, 2019 - 6:04:19 PM
Last modification on : Friday, April 5, 2019 - 6:27:11 PM

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  • HAL Id : hal-01974457, version 1
  • ARXIV : 1901.01391

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Bruno Iochum, Thierry Masson. Heat coefficient $a_4$ for nonminimal Laplace type operators. Journal of Geometry and Physics, Elsevier, 2019, 141, pp.120-146. ⟨hal-01974457⟩

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