Topological terms and the Misner string entropy

We examine the thermodynamics of Euclidean dyonic Taub-Nut/Bolt-AdS4 black holes for a variety of horizon geometries to understand how gauge field regularity conditions influence the thermodynamic relations. We find several distinct features that distinguish the NUT-charged case from its dyonic Reissner-Nordstrom counterpart. For the Nut solution, the gauge field vanishes at the horizon and so regularity is ensured. For the Bolt solution we find that the norm of the gauge field is required to vanish at the horizon in order to satisfy both regularity and the first law of thermodynamics. This regularity condition yields a constraint on the electric and magnetic charges and so reduces cohomogeneity of the system; for spherical horizons, the regularity condition removing the Misner string singularity further reduces cohomogeneity. We observe that bolt solutions with increasing electric charge have positive heat capacity, but upon turning on the magnetic charge to make the solution dyonic, we find that the properties of the uncharged one are retained, having both positive and negative heat capacity. We also study the extremal Bolt solution, finding that Misner string disappears at the horizon in the zero temperature limit. We find that the extremal solution has finite-temperature-like behaviour, with the electric potential playing a role similar to temperature.

Section: Jhep03(2021)039supporting

confidence: 79%

Complement to thermodynamics of dyonic Taub-NUT-AdS spacetime

Mann

Zayas

Park

2021

“…Another illustrative example is given by the addition of both Gauss-Bonnet and Chern-Pontryagin invariants to the 4D Einstein-AdS gravity. The direct application of NW procedure leads to a charge which is identically vanishing for globally (anti-)self dual solutions, feature that is shared by the total action [34,35]. This reasoning opens the possibility of zero action/zero charges for the whole class of spaces, and not only for a particular solution.…”

Section: Jhep07(2021)156mentioning

confidence: 93%

Noether-Wald charges in six-dimensional Critical Gravity

Anastasiou

Araya

Corral

et al. 2021

Self Cite

It has been recently shown that there is a particular combination of conformal invariants in six dimensions which accepts a generic Einstein space as a solution. The Lagrangian of this Conformal Gravity theory — originally found by Lu, Pang and Pope (LPP) — can be conveniently rewritten in terms of products and covariant derivatives of the Weyl tensor. This allows one to derive the corresponding Noether prepotential and Noether-Wald charges in a compact form. Based on this expression, we calculate the Noether-Wald charges of six-dimensional Critical Gravity at the bicritical point, which is defined by the difference of the actions for Einstein-AdS gravity and the LPP Conformal Gravity. When considering Einstein manifolds, we show the vanishing of the Noether prepotential of Critical Gravity explicitly, which implies the triviality of the Noether-Wald charges. This result shows the equivalence between Einstein-AdS gravity and Conformal Gravity within its Einstein sector not only at the level of the action but also at the level of the charges.

“…In a complementary manner, in Euclidean configurations, adding topological terms to the action shows that the NUT parameter contributes to the mass [49]. Moreover, from a thermodynamic point of view Misner strings are sources of entropy [50,51]. Lastly, we mention that from an astrophysical point of view, NUT parameters have observable effects on the apparent horizon's shadow [52].…”

Section: Jhep09(2021)104mentioning

confidence: 80%

Nonlinear extensions of gravitating dyons: from NUT wormholes to Taub-Bolt instantons

Flores-Alfonso

Linares

Maceda

2021

Recent work has shown the existence of a unique nonlinear extension of electromagnetism which preserves conformal symmetry and allows for the freedom of duality rotations. Moreover, black holes and gravitational waves have been found to exist in this nonlinearly extended electrovacuum. We generalise these dyonic black holes in two major ways: with the relaxation of their horizon topology and with the inclusion of magnetic mass. Motivated by recent attention to traversable wormholes, we use this new family of Taub-NUT spaces to construct AdS wormholes. We explore some thermodynamic features by using a semi-classical approach. Our results show that a phase transition between the nut and bolt configurations arises in a similar way to the Maxwellian case.