Unirationality and rationality of Ueno-Campana manifolds
 
Fabrizio Catanese (University of Bayreuth)



Let E be either the anharmonic elliptic curve E_i, which admits complex multiplication by i, the 4-th root of 1, or the equianharmonic (or Fermat) elliptic curve E', which admits complex multiplication by eta, the 6-th root of 1. The Ueno-Campana manifolds are the minimal resolutions of singularities Y^n_m of the quotient of E^n by the diagonal action of a cyclic group of order m= 3,4, or 6 acting with a fixed point. These manifolds are well known in dimension n=1,2. For n geq 3, Ueno showed that Y^n_4 has Kodaira dimension 0 for n geq 4, and asked whether Y^3_4 is unirational. This was proven in a joint work with Oguiso and Truong, later Colliot Thelene showed, using our conic bundle realization, that Y^3_4 is indeed rational. Oguiso and Truong proved the rationality of Y^3_6, while Y^n_6 has Kodaira dimension 0 for n geq 6. Together with Oguiso, we proved the unirationality of Y^4_6, showing that it is birational to a diagonal cubic surface over the function field CC(x,y) admitting 27 rational points. Using a result of Segre, the surface is unirational, but it does not seem to be rational. The interest in the rationality of these manifolds stems from complex dynamics and entropy.



Torna alla pagina dei seminari