Euclidean Methods and the entropy function
  We review results of articles hep-th/0607056, hep-th/0610163 and 0704.1405 [hep-th]. Here we focus on establish the connection between the entropy functional formalism of Sen and the standard Euclidean formalism taken at zero temperature. We find that Sen's entropy function $f$ (on-shell) matches the zero temperature limit of the Euclidean action. Moreover, Sen's near horizon angular and electric fields agree with the chemical potentials that are defined from the zero-temperature limit of the Euclidean formalism. Connection with the Dual CFT thermodynamics is briefly discussed. 
Pedro J Silva