Chaotic inflation with variable space dimension

Abstract

Assuming the space dimension is not constant but decreases during the expansion of the Universe, we study chaotic inflation with the potential m 2 φ 2 /2. We write down field equations in the slow-roll approximation and define slow-roll parameters by assuming the space dimension to be a dynamical parameter. The dynamical character of the space dimension shifts the initial and final value of the inflaton field to larger values, producing delayed chaotic inflation. We obtain an upper limit for the space dimension at the Planck length. This result is in agreement with previous works on the effective time variation of the Newtonian gravitational constant in a model Universe with variable space dimensions. We present some cosmological consequences and calculate observable quantities including the spectral indices, their scale-dependence, and the mass of the inflaton field.