Real bundle automorphisms, Cauchy Riemann operators and orientability of moduli spaces

Abstract

This paper consists in a very brief English summary of the results appearing in French in two previous articles. We omit the proofs and focus on explaining our approach and theorems. This paper is not intended to be published. Questions are welcome. In our work, we considered a complex vector bundle $N$ equipped with a real structure $c_N$ over a real curve of arbitrary genus. We computed the sign of the action of an automorphism of $(N,c_N)$ on the orientations of the determinant line bundle over the space of Cauchy-Riemann operators on $(N,c_N)$. We first considered the automorphisms lifting the identity on the curve (in the first article). In this case, we obtained the sign as a product of two terms. The first one computes the signature of the permutations induced by the automorphisms acting in the $Pi{n}^{\pm }$ structures on the real part of $(N,c_N)$. The second one comes from the action of the automorphisms of $(N,c_N)$ on the bordism classes of real $Spin$ structures on the curve. We then studied the general case in the second article. As an application of these results, we computed the first Stiefel-Whitney class of the moduli space of real pseudoholomorphic curves in many cases.