tt *-Geometry on the Big Phase Space

The big phase space, the geometric setting for the study of quantum cohomology with gravitational descendants, is a complex manifold and consists of an infinite number of copies of the small phase space. The aim of this paper is to define a Hermitian geometry on the big phase space. Using the approach of Dijkgraaf and Witten (Nucl Phys B 342:486–522, 1990), we lift various geometric structures of the small phase space to the big phase space. The main results of our paper state that various notions from tt ^*-geometry are preserved under such liftings.