Resumen:
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In the context of modified and gauge invariant Electrodynamics theories minimally coupled with gravitation we look for the U(1) Lagrangian densities supporting electric and magnetic monopoles which provide sta Nordström black-hole solutions. We achieve a sufficient condition for general Lagrangian densities supporting this kind of solutions, and we propose a simple model which can be interpreted as a small correction to the usual Electrodynamics theory, which is proven to be correct in the asymptotic limit r ? ? . For these models we obtain their correspondent metrics, and then by employing the Euclidean Action approach we perform a thermodynam- ics analysis and study the existing phases depending on the sign of the heat capacity and the Helmholtz free energy. Thus, we obtain that modified Electrodynamics theories lead to ve different thermodynamics properties and, in some particular cases, to a new phase which does not appear in the usual theory.
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