Random Matrices and the Expected Topology of Quadric Hypersurfaces

Let XR be the zero locus in RP n of one or two independently and Weyl distributed random real quadratic forms. Denoting by XC the complex part in CP n of XR and by b(XR) and b(XC) the sums of their Betti numbers, we prove that: (1) lim n→∞ Eb(XR) n = 1. In particular for one quadric hypersurface asymptotically Smith’s inequality b(XR) ≤ b(XC) is expected to be sharp. The methods we use combine Random Matrix Theory, Integral Geometry and spectral sequences.