Abstract:We de ne two parabolic ows on almost complex manifolds, which coincide with the pluriclosed ow and the Hermitian curvature ow respectively on complex manifolds. We study the relationship between these parabolic evolution equations on compact almost Hermitian manifolds.Keywords: almost Hermitian metric, pluriclosed ow, Hermitian curvature ow MSC: 53C44 (primary); 53C55; 32W20 (secondary)
IntroductionIn [5] and [7], Streets and Tian introduced a parabolic evolution equation of pluriclosed metrics with a pluriclosed initial metric on a Hermitian manifold, which is called the pluriclosed ow. In this paper, we would like to show that some of their results hold for almost Hermitian cases as well. Let (M, J) be a compact almost complex manifold and let g be an almost Hermitian metric on M. Let {Zr} be an arbitrary local ( , )-frame around a xed point p ∈ M and let {ζ r } be the associated coframe. Then the associated real ( , )-form ω with respect to g takes the local expression ω = √ − g rk ζ r ∧ ζk. We will also refer to ω as to an almost Hermitian metric. We would like to de ne a parabolic ow of almost Hermitian metrics with an almost pluriclosed initial metric ω on (M, J). We say a metric ω is almost pluriclosed if ω is an almost Hermitian metric and ∂∂-closed (cf. De nition 1.1). We will call it the almost pluriclosed ow (APF): g(t) are the L -adjoint operators with respect to metrics g(t), and P(ω) is one of the Riccitype curvatures of the Chern curvature. One has with an arbitrary ( , )-frame {Zr} with respect to g, P ij =where Ω is the curvature of the Chern connection ∇ on (M, g, J) and O(∂ω) means an expression which only depends on at most rst derivatives of ω. The rst goal of this paper is to prove that the operator ω → Φ(ω) is a strictly elliptic operator for an almost pluriclosed metric ω, which means that the equation (APF) with an almost pluriclosed initial metric is a strictly parabolic equation. Hence the short-time existence and the uniqueness of the solution (APF) follows from the standard parabolic theory since the manifold is supposed to be compact. This ow (APF) coincides with the pluriclosed ow if J is integrable and also the initial metric is pluriclosed (cf.
73We will also refer to the associated real ( , )-form ω as an almost pluriclosed metric. Theorem 1.1. Given a compact almost Hermitian manifold (M, ω , J) with almost pluriclosed metric ω , there exists a unique solution ω(t) to (APF) with initial condition ω for t ∈ [ , ε) for some ε > . Moreover, if ω( ) is almost pluriclosed, the metric ω(t) is almost pluriclosed for all t ∈ [ , ε).We denote by S one of the Ricci-type curvatures of the Chern curvature, which is locally given by S ij = g kl Ω klij. The second goal of this paper is to prove that a solution of the almost pluriclosed ow with initial almost pluriclosed metric ω is equivalent to a solution of the following parabolic ow starting at the initial almost pluriclosed metric ω on a compact almost complex manifold with an almost pluriclosed Hermitian metric, we will call...