Thermodynamics Of dilaton-axion black holes

Considering a generalised action for Einstein Maxwell theory in four dimensions coupled to scalar and pseudo-scalar fields, the thermodynamic properties of asymptotically flat black holes solutions in such a background are investigated. Bekenstein-Hawking area-entropy law is verified for these class of black holes. From the property of specific heat, it is shown that such black holes can be stable for certain choice of the parameters like charge, mass and the scalar vacuum expectation value. The possibility of a black hole phase transition is discussed in this context.