Komplexe elliptische Geschlechter und S^1-aequivariante   Kobordismustheorie (Complex elliptic genera and S^1-equivariant cobordism   theory)
  We introduce the universal complex elliptic genus phi_ell as the ring homomorphism from the complex cobordism ring Omega^U to the polynomial ring C[A,B,C,D] associated to the characteristic power series Q(x)=x/f(x), where f is the solution of the differential equation (f'/f)'=S(f'/f), S(y) = (y+A/2)^4-B/4*(y+A/2)^2+4C*(y+A/2)+B^2/64-2D. Formally, phi_ell arises as the index of the Dolbeault operator of the loop space of a manifold. For manifolds with vanishing first Chern class, phi_ell becomes a Jacobi form F(z,\tau) for the full Jacobi group Z^2 x PSL_2(Z). We prove the rigidity of phi_ell for S^1-actions on SU-manifolds. The kernel of phi_ell in the rational SU-cobordism ring is characterized as the ideal generated by manifolds with S^1-action of fixed type t (an integer) different from 0.   For z to be an N-division point on the elliptic curve determined by \tau, phi_ell specializes to the Level N genus phi_N. We introduce the cobordism ring Omega^{U,N} of stably almost complex manifolds with first Chern class divisible by N and characterize the kernel of phi_N by certain ideals in the rationalized ring Omega^{U,N}.   In Chapter 1, we construct a base sequence W_1, W_2, W_3, ... of the rational cobordism ring Omega^U on which phi_ell has the values A, B, C, D, and 0 for W_i with i>=5. In Chapter 2, phi_ell and phi_N are investigated and the main results are proven. Chapter 3 contains the further result that the level N genus is invariant under the blow up along a submanifold Y of a complex manifold X if the codimension of Y in X is congruent 1 modulo N. 
Gerald Hoehn