Periods and motives in the spectral action of Robertson-Walker   spacetimes
  We show that, when considering the scaling factor as an affine variable, the coefficients of the asymptotic expansion of the spectral action on a (Euclidean) Robertson-Walker spacetime are periods of mixed Tate motives, involving relative motives of complements of unions of hyperplanes and quadric hypersurfaces and divisors given by unions of coordinate hyperplanes. 
Farzad Fathizadeh and Matilde Marcolli
math-ph math.AG math.DG math.MP