On surfaces with $p_g=2$, $q=1$ and non-birational bicanonical map

Abstract

In the present note we show that any surface of general type with $p_g=2$,$q=1$ and non-birational bicanonical map has a pencil of curves of genus 2. Combining this result with previous ones, one obtains thatan irregular surface $S$ of general type with $χ(S)\geq 2$ and non-birational bicanonical map has a pencil of curves of genus 2.

Latex 2e, 10 pages. To appear in the Proceedings of the Conference in memory of Paolo Francia, Genova, September 2001