Singularities of Green functions of the products of the Laplace type operators

The structure of diagonal singularities of Green functions of partial differential operators of even order acting on smooth sections of a vector bundle over a Riemannian man ifold is studied. A special class of operators formed by the products of second-order operators of Laplace type defined with the help of a unique Riemannian metric and a unique bundle connection but with different potential terms is investigated. Explicit simple formulas for singularities of Green functions of such operators in terms of the usual heat kernel coefficients are obtained.Comment: 12 Pages, LaTeX, 30 KB, No Figures, submitted to Physics Letters B, Discussion of the Huygence principle is remove

Smith theory, L2 cohomology, isometries of locally symmetric manifolds and moduli spaces of curves

We investigate periodic diffeomorphisms of non-compact aspherical manifolds (and orbifolds) and describe a class of spaces that have no homotopically trivial periodic diffeomorphisms. Prominent examples are moduli spaces of curves and aspherical locally symmetric spaces with non-vanishing Euler characteristic. In the irreducible locally symmetric case, we show that no complete metric has more symmetry than the locally symmetric metric. In the moduli space case, we build on work of Farb and Weinberger and prove an analogue of Royden's theorem for complete finite volume metrics.Comment: 24 page

Covariant algebraic calculation of the one-loop effective potential in non-Abelian gauge theory and a new approach to stability problem

We use our recently proposed algebraic approach for calculating the heat kernel associated with the Laplace operator to calculate the one-loop effective action in the non-Abelian gauge theory. We consider the most general case of arbitrary space-time dimension, arbitrary compact simple gauge group and arbitrary matter and assume a covariantly constant gauge field strength of the most general form, having many independent color and space-time invariants (Savvidy type chromomagnetic vacuum) and covariantly constant scalar fields as a background. The explicit formulas for all the needed heat kernels and zeta-functions are obtained. We propose a new method to study the vacuum stability and show that the background field configurations with covariantly constant chromomagnetic fields can be stable only in the case when more than one independent field invariants are present and the values of these invariants differ not greatly from each other. The role of space-time dimension is analyzed in this connection and it is shown that this is possible only in space-times with dimensions not less than five $d\geq 5$.Comment: 14 pages, LATeX, University of Greifswald (1994