Vortrag mit dem Titel: The negative Pell equation and the Cohen-Lenstra heuristic
For a (squarefree) integer d the negative Pell equation is given by: X^2 - d Y^2 = -1.
It is easy to see that this equation has no solution over the integers, if d is negative or d is congruent to 3 modulo 4. In this talk we ask for how many d`s is this equation solvable. This question is related to the behavior of the class group of the quadratic field generated by a square root of d. The distribution of those class groups is described by the Cohen-Lenstra heuristics.