Oberseminar WiSe 2009/10 Zusammenfassung des Vortrags von J. Cerviño (Essen)
In the theory of positive definite quadratic forms, the theta series is an important invariant with respect to the orthogonal group. The theta series determines the isometry class for small dimensions (n =1,2,3), but not for n >3. In this talk, I will introduce the so-called theta-invariants as 'true' generalisation of theta series. I will apply these invariants to a well-known problem of Conway and Sloane in dimension 4.
(Joint work with G. Hein)