Abstract: After recalling the Rost nilpotence property and its meaning, I will show that for 3-dimensional smooth projective varieties over a field of characteristic 0, one has only 'to care' about 0-cycles. Using the Brown-Gersten-Quillen spectral sequence, one can get one's hands on the zero cycles of a 3-dimensional toric model allowing a proof of Rost nilpotence for such varieties.

Abstract: I shall prove the Harer-Zagier formula and Wigner's semicircle law for random matrices. We shall then move to evaluation of matrix integrals via graphs on surfaces.