Abstract:
This paper is devoted to the proper-time method and describes a model case that reflects the subtleties of constructing the heat kernel, is easily extended to more general cases (curved space, manifold with a boundary), and contains two interrelated parts: an asymptotic expansion and a path integral representation. We discuss the significance of gauge conditions and the role of ordered exponentials in detail, derive a new nonrecursive formula for the Seeley–DeWitt coefficients on the diagonal, and show the equivalence of two main approaches using the exponential formula.
Keywords:path integral, Wilson line, ordered exponential, Fock–Schwinger gauge, Laplace operator, heat kernel, Seeley–DeWitt coefficient, proper time method.