- Open Access
Functorial properties of Schwinger-DeWitt expansion and Mellin-Barnes representation
Phys. Rev. D 113, 045005 – Published 4 February, 2026
DOI: https://doi.org/10.1103/l112-5cz3
Abstract
We consider integral kernels for functions of a minimal second-order differential operator on a curved spacetime. We show that they can be expanded in a functional series, analogous to the DeWitt expansion for the heat kernel, by integrating the latter term-by-term. This procedure leads to a separation of two types of data: all information about the bundle geometry and the operator is still contained in the standard heat kernel coefficients (we call this property “off-diagonal functoriality”), while information about the function is encoded in some new scalar functions and , which we call basis and complete massive kernels, respectively. These objects are calculated for operator functions of the form as multiple Mellin-Barnes integrals. The article also discusses subtle issues such as the validity of the term-by-term integration, the regularization of IR divergent integrals, and the physical interpretation of the resulting expansions.
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