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Published online by Cambridge University Press: 23 January 2023
We describe the small-time heat kernel asymptotics of real powers $\operatorname {\Delta }^r$,
$r \in (0,1)$ of a non-negative self-adjoint generalized Laplacian
$\operatorname {\Delta }$ acting on the sections of a Hermitian vector bundle
$\mathcal {E}$ over a closed oriented manifold M. First, we treat separately the asymptotic on the diagonal of
$M \times M$ and in a compact set away from it. Logarithmic terms appear only if n is odd and r is rational with even denominator. We prove the non-triviality of the coefficients appearing in the diagonal asymptotics, and also the non-locality of some of the coefficients. In the special case
$r=1/2$, we give a simultaneous formula by proving that the heat kernel of
$\operatorname {\Delta }^{1/2}$ is a polyhomogeneous conormal section in
$\mathcal {E} \boxtimes \mathcal {E}^* $ on the standard blow-up space
$\operatorname {M_{heat}}$ of the diagonal at time
$t=0$ inside
$[0,\infty )\times M \times M$.
This work was partially supported from the project PN-III-P4-ID-PCE-2020-0794 funded by UEFSCDI.