Varying Constants in Brane World Scenarios
  Higher-dimensional theories imply that some constants, such as the gravitational constant and the strength of the gauge-couplings, are not fundamental constants. Instead they are related to the sizes of the extra--dimensional space, which are moduli fields in the four--dimensional effective theory. We study the cosmological evolution of the moduli fields appearing in brane world scenarios and discuss the implications for varying constants. 
Ph. Brax, C. van de Bruck, A.-C. Davis and C.S. Rhodes