Phase transition of charged Black Holes in Brans–Dicke theory through geometrical thermodynamics

• Published in: The European physical journal. C, Particles and fields Vol. 76; no. 7; p. 1
• Main Authors: Hendi, S. H., Panahiyan, S., Panah, B. Eslam, Armanfard, Z.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 13-07-2016; Springer; Springer Nature B.V
• Subjects: Analysis; Astronomy; Astrophysics and Cosmology; Black holes; Elementary Particles; Hadrons; Heavy Ions; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article - Theoretical Physics; String Theory; Thermodynamics; Black Hole Solution; Order Phase Transition; Black Hole; Heat Capacity; Divergence Point
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-016-4235-1

In this paper, we take into account black hole solutions of Brans–Dicke–Maxwell theory and investigate their stability and phase transition points. We apply the concept of geometry in thermodynamics to obtain phase transition points and compare its results with those, calculated in the canonical ensemble through heat capacity. We show that these black holes enjoy second order phase transitions. We also show that there is a lower bound for the horizon radius of physical charged black holes in Brans–Dicke theory, which originates from restrictions of positivity of temperature. In addition, we find that employing a specific thermodynamical metric in the context of geometrical thermodynamics yields divergencies for the thermodynamical Ricci scalar in places of the phase transitions. It will be pointed out that due to the characteristic behavior of the thermodynamical Ricci scalar around its divergence points, one is able to distinguish the physical limitation point from the phase transitions. In addition, the free energy of these black holes will be obtained and its behavior will be investigated. It will be shown that the behavior of the free energy in the place where the heat capacity diverges demonstrates second order phase transition characteristics.