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Jun 24, 2011 at 16:58 comment added roy smith yes, Beauville's theory (and earlier partial steps by Masiewicki) shows that double covers with an even number of ramification points do yield a ppav once one identifies those points in pairs. But this does not help solve the ramified torelli problem since the torelli results for Beauville pryms are so generic, that the injectivity does not specialize. for covers that become singular so as to be still unramified however one can use induction on the normalization once that normalization becomes generic. Bob Friedman and I took this inductive approach to generic torelli for plane septics.
Jun 24, 2011 at 4:44 comment added Dan Petersen Thanks for the insight, this seems like a useful perspective. I guess another way of saying this is that you are identifying $R_{g,2}$ with a boundary stratum of the space $\overline{R}_{g+1}$ of admissible covers, and hence the two-pointed prym map with the restriction of the ordinary prym map in genus g+1.
Jun 23, 2011 at 22:38 history edited roy smith CC BY-SA 3.0
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Jun 23, 2011 at 22:16 history edited roy smith CC BY-SA 3.0
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Jun 23, 2011 at 22:00 history answered roy smith CC BY-SA 3.0