Upper bounds for regularized determinants

Abstract

Let $E$ be a holomorphic vector bundle on a compact Kähler manifold $X$. If we fix a metric $h$ on $E$, we get a Laplace operator $Δ$ acting upon smooth sections of $E$ over $X$. Using the zeta function of $Δ$, one defines its regularized determinant $det'(Δ)$. We conjectured elsewhere that, when $h$ varies, this determinant $det'(Δ)$ remains bounded from above. In this paper we prove this in two special cases. The first case is when $X$ is a Riemann surface, $E$ is a line bundle and $dim(H^0 (X,E)) + dim(H^1 (X,E)) \leq 2$, and the second case is when $X$ is the projective line, $E$ is a line bundle, and all metrics under consideration are invariant under rotation around a fixed axis.