Dilatonic (Anti-)de Sitter black holes and Weak Gravity Conjecture

Einstein-Maxwell-dilaton theory with non-trivial dilaton potential is known to admit asymptotically flat and (Anti-)de Sitter charged black hole solutions. We investigate the conditions for the presence of horizons as function of the parameters mass M, charge Q and dilaton coupling strength α. We observe that there is a value of α which separate two regions, one where the black hole is Reissner-Nordström-like from a region where it is Schwarzschild-like. We find that for de Sitter and small non-vanishing α, the extremal case is not reached by the solution. We also discuss the attractive or repulsive nature of the leading long distance interaction between two such black holes, or a test particle and one black hole, from a world-line effective field theory point of view. Finally, we discuss possible modifications of the Weak Gravity Conjecture in the presence of both a dilatonic coupling and a cosmological constant.

Horizon acoustics of the GHS black hole and the spectrum of AdS2

We uncover a novel structure in Einstein-Maxwell-dilaton gravity: an AdS2 × S2 solution in string frame, which can be obtained by a near-horizon limit of the extreme GHS black hole with dilaton coupling λ ≠ 1. Unlike the Bertotti-Robinson spacetime, our solution has independent length scales for the AdS2 and S2, with ratio controlled by λ. We solve the perturbation problem for this solution, finding the independently propagating towers of states in terms of superpositions of gravitons, photons, and dilatons and their associated effective potentials. These potentials describe modes obeying conformal quantum mechanics, with couplings that we compute, and can be recast as giving the spectrum of the effective masses of the modes. By dictating the conformal weights of boundary operators, this spectrum provides crucial data for any future construction of a holographic dual to these AdS2 × S2 configurations.

The layered phase of anisotropic gauge theories: A model for topological insulators

Topological insulators are materials where current does not flow through the bulk, but along the boundaries, only. They are of particular practical importance, since it is considerably more difficult, by “conventional” means, to affect their transport properties, than for the case of conventional materials. They are, thus, particularly robust to perturbations. One way to accomplish such changes is by engineering defects. The defects that have been the most studied are domain walls; however flux compactifications can also work. We recall the domain wall construction and compare it to the construction from flux compactification. A particular way of engineering the presence of such defects is by introducing anisotropic couplings for the gauge fields. In this case, a new phase appears, where matter is confined along layers and local degrees of freedom cannot propagate through the bulk. It is also possible to take into account the “backreaction” of the dynamics of the gauge fields on the defects and find that a new phase, the layered phase, where, while transport of local degrees of freedom is confined to surfaces, the topological properties can propagate through the bulk, constituting an example of anomaly flow. The anisotropy itself can be understood as emerging from a particular Maxwell-dilaton coupling.

Quasinormal modes of dilatonic Reissner–Nordström black holes

We calculate the quasinormal modes of static spherically symmetric dilatonic Reissner–Nordström black holes for general values of the electric charge and of the dilaton coupling constant. The spectrum of quasinormal modes is composed of five families of modes: polar and axial gravitational-led modes, polar and axial electromagnetic-led modes, and polar scalar-led modes. We make a quantitative analysis of the spectrum, revealing its dependence on the electric charge and on the dilaton coupling constant. For large electric charge and large dilaton coupling, strong deviations from the Reissner–Nordström modes arise. In particular, isospectrality is strongly broken, both for the electromagnetic-led and the gravitational-led modes, for large values of the charge.

Kalb–Ramond field localization in sine-Gordon braneworld models

In this paper, we investigate Kalb–Ramond field localization in two types of five-dimensional braneworld models given by sine-Gordon potentials. The sine-Gordon (SG) and double sine-Gordon (DSG) branes are generated by a real scalar field coupled to gravity minimally. In both scenarios, we employ two localization mechanisms. One is the well-known dilaton coupling and the other is based on a five-dimensional Stueckelberg-like action. With two mechanisms, we find that the massless zero mode of Kalb–Ramond field is localized on the SG and DSG branes. Also, it is shown that both the mechanisms can result in a volcano-like potential of the Kalb–Ramond massive modes. Furthermore, we study the effects of the dilaton coupling constant on the mass spectrum of the Kalb–Ramond field.

ON THE IMPLICATIONS OF A DILATON IN GAUGE THEORY

Some recent work on the implications of a dilaton in 4 d gauge theories are revisited. In part I of this paper we see how an effective dilaton coupling to gauge kinetic term provides a simple attractive mechanism to generate confinement. In particular, we put emphasis on the derivation of confining analytical solutions and look into the problem how dilaton degrees of freedom modify Coulom potential and when a confining phase occurs. In part II, we solve the semi-relativistic wave equation, for Dick interquark potential using the Shifted l-expansion technique (SLET) in the heavy quarkonium sector. The results of this phenomenological analysis proves that these effective theories can be relevant to model quark confinement and may shed some light on confinement mechanism.