# Heat coefficient $a_4$ for non minimal Laplace type operators

1 CPT - E2 Géométrie, Physique et Symétries
CPT - Centre de Physique Théorique - UMR 7332
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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Journal articles
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https://hal.archives-ouvertes.fr/hal-01974457
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Submitted on : Friday, October 22, 2021 - 5:37:04 PM
Last modification on : Monday, November 15, 2021 - 12:48:07 PM

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### Citation

Bruno Iochum, Thierry Masson. Heat coefficient $a_4$ for non minimal Laplace type operators. Journal of Geometry and Physics, Elsevier, 2019, 141, pp.120-146. ⟨10.1016/j.geomphys.2019.03.002⟩. ⟨hal-01974457⟩

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