arXiv subjects

Alex Flournoy

Publications and source records attributed to Alex Flournoy.

8 recordsLinked to original sources

arXiv2022

Behavior of a Chiral Condensate Around Astrophysical-Mass Schwarschild and Reissner-Nordstr\"om Black Holes

In this work, we develop a perturbative method to describe the behavior of a chiral condensate around a spherical black hole whose mass is astrophysically realistic. We use the inverse mass as the expansion parameter for our perturbative series. We test this perturbative method in the case of a Schwarzschild black hole, and we find that it agrees well with previous numerical results. For an astrophysical-mass Schwarzschild black hole, the leading order contribution to the condensate is much larger (in most of space) than the next-to-leading order contribution, providing further evidence for the validity of the perturbative approach. The size of the bubble of restored chiral symmetry is directly proportional to the size of the black hole. Next, we apply this perturbative method to a Reissner-Nordstr\"om (RN) black hole. We find that, as the charge-to-mass ratio increases, the bubble of restored chiral symmetry becomes larger relative to the black hole. This effect is particularly pronounced for near-extremal RN black holes. The case of an extremal RN black hole provides an interesting counterexample to the standard thermal explanation for the formation of a bubble of restored chiral symmetry around a black hole.

hep-th↗

arXiv2022

On the Stability of a Wormhole in the Maximally-Extended Reissner-Nordstr\"om Solution

We consider the stability of the maximally-extended Reissner-Nordstr\"om solution in a Minkowski, de Sitter, or anti-de Sitter background. In a broad class of situations, prior work has shown that spherically symmetric perturbations from a massless scalar field cause the inner horizon of an RN black hole to become singular and collapse. Even if this is the case, it may still be possible for an observer to travel through the inner horizon before it fully collapses, thus violating strong cosmic censorship. In this work, we show that the collapse of the inner horizon and the occurrence of a singularity along the inner horizon are sufficient to prevent an observer from accessing the white hole regions and the parallel universe regions of the maximally extended RN space-time. Thus, if an observer passes through the inner horizon, they will inevitably hit the central singularity. Throughout this article, we use natural units where c = G = 4 {\pi} {\epsilon}_0 = 1.

gr-qc↗

arXiv2019

Thermodynamic phase transitions from dynamical compact dimensions

We perform a double quotient of global AdS$_4$ and study its thermal properties. We find that a double quotient yields a spacetime with an expanding compact dimension. Studying the entanglement of the dual CFT we find that, at early times, the spacetime has thermal properties which disappear after a critical time. For slow expansion, this critical time depends on the expansion rate as expected, but becomes much more sensitive with more rapid expansion rates.

hep-th↗

arXiv2018

Holographic Entanglement Entropy and the (3+1)-dimensional Topological Black Hole

We investigate the Holographic Entanglement Entropy proposal in the context of the (3+1)-dimensional topological black hole. In contrast to the well-studied (2+1)-dimensional case, the maximal extension for this black hole includes only a single exterior region with its conformal boundary. This immediately raises a puzzle as to how one can view the purification of the dual conformal field theory state in terms of a thermofield double in the usual manner. Motivated by this puzzle, we calculate the horizon area for these black holes and discover that the result is observer dependent. This observer dependence poses a potential issue in applying the holographic entropy proposal. Investigating this we find that, although this observer dependence does not carry over to the holographic entanglement entropy, there is an indication of a coordinate system which is best adapted for the holographic calculation. These coordinates only cover two regions of the spacetime which exactly correspond to the regions of the CFT on which particle modes are well defined and so we see that the holographic calculation in the spacetime is capable of predicting regions of the CFT where particles cannot exist.

hep-th↗

arXiv2016

Connecting Through Obstruction; Relating Gauge Gravity and String Theory

In this article we provide a more detailed account of the geometry and topology of the composite bundle formalism introduced by Tresguerres in Phys. Rev. D 66 (2002) 064025 [1] to accommodate gravitation as a gauge theory. In the first half of the article we identify a global structure required by the composite construction which not only exposes how the ordinary frame and tangent bundle expected in general relativity arise but provides the link or connection between these ordinary bundles and the gauge bundles of the composite bundle construction. In the second half of the article we discuss implications of this method of constructing gravity as a fiber bundle for the global structure of spacetime. We find that the underlying manifold of the composite bundle construction is expected to admit, not only a spin structure but also a string structure. As a consequence of our work we are able to extend past work on global structures of physically reasonable spacetime manifolds. It has been shown that in four spacetime dimensions, that if an oriented, Lorentzian, four dimensional manifold is stably casual that it is parallizable, and hence admits a spin structure which allows for chiral spinors. We may now add to this that such a manifold also admits a string structure.

gr-qc↗

arXiv2015

Background-Independence from the Perspective of Gauge Theory

We consider two concepts often discussed as significant features of general relativity (particularly when contrasted with the other forces of the Standard Model): background independence and diffeomorphism invariance. We remind the reader of the role of backgrounds both as calculational tools and as part of the formulation of theories. Examining familiar gauge theory constructions, we are able to pinpoint when in the formulation of these theories they become background independent. We then discuss extending the gauge formulation to gravity. In doing so we are able to identify what makes general relativity a background independent theory. We also discuss/dispel suggestions that "active" diffeomorphism invariance is a feature unique to general relativity and we go on to argue against the claim that this symmetry is the origin of background independence of the theory.

gr-qc↗

arXiv2006

Nongeometry, Duality Twists, and the Worldsheet

In this paper, we use orbifold methods to construct nongeometric backgrounds, and argue that they correspond to the spacetimes discussed in \cite{dh,wwf}. More precisely, we make explicit through several examples the connection between interpolating orbifolds and spacetime duality twists. We argue that generic nongeometric backgrounds arising from duality twists will not have simple orbifold constructions and then proceed to construct several examples which do have a consistent worldsheet description.

hep-th↗

arXiv2004

Constructing Nongeometric Vacua in String Theory

In this paper we investigate compactifications of the type II and heterotic string on four-dimensional spaces with nongeometric monodromies. We explicitly construct backgrounds which contain the "Duality Twists" discussed by Dabholkar and Hull. Similar constructions of nongeometric backgrounds have been discussed for type II strings by Hellerman, McGreevy, and Williams. We find that imposing such monodromies projects out many moduli from the resulting vacua and argue that these backgrounds are the spacetime realizations of interpolating asymmetric orbifolds.

hep-th↗