Marginally Trapped Surfaces and AdS/CFT

It has been proposed that the areas of marginally trapped or anti-trapped surfaces (also known as leaves of holographic screens) may encode some notion of entropy. To connect this to AdS/CFT, we study the case of marginally trapped surfaces anchored to an AdS boundary. We establish that such boundary-anchored leaves lie between the causal and extremal surfaces defined by the anchor and that they have area bounded below by that of the minimal extremal surface. This suggests that the area of any leaf represents a coarse-grained von Neumann entropy for the associated region of the dual CFT. We further demonstrate that the leading area-divergence of a boundary-anchored marginally trapped surface agrees with that for the associated extremal surface, though subleading divergences generally differ. Finally, we generalize an argument of Bousso and Engelhardt to show that holographic screens with all leaves anchored to the same boundary set have leaf-areas that increase monotonically along the screen, and we describe a construction through which this monotonicity can take the more standard form of requiring entropy to increase with boundary time. This construction is related to what one might call future causal holographic information, which in such cases also provides an upper bound on the area of the associated leaves.Comment: 23 pages, 5 figure

A perturbative perspective on self-supporting wormholes

We describe a class of wormholes that generically become traversable after incorporating gravitational back-reaction from linear quantum fields satisfying appropriate (periodic or anti-periodic) boundary conditions around a non-contractible cycle, but with natural boundary conditions at infinity (i.e., without additional boundary interactions). The class includes both asymptotically flat and asymptotically AdS examples. Simple asymptotically AdS$_3$ or asymptotically AdS$_3 \times S^1$ examples with a single periodic scalar field are then studied in detail. When the examples admit a smooth extremal limit, our perturbative analysis indicates the back-reacted wormhole remains traversable at later and later times as this limit is approached. This suggests that a fully non-perturbative treatment would find a self-supporting eternal traversable wormhole. While the general case remains to be analyzed in detail, the likely relation of the above effect to other known instabilities of extreme black holes may make the construction of eternal traversable wormholes more straightforward than previously expected.Comment: Minor corrections (including fixing a factor of 2 in several formulas/plots

Traversable asymptotically flat wormholes with short transit times

We construct traversable wormholes by starting with simple four-dimensional classical solutions respecting the null energy condition and containing a pair of oppositely charged black holes connected by a non-traversable wormhole. We then consider the perturbative back-reaction of bulk quantum fields in Hartle-Hawking states. Our geometries have zero cosmological constant and are asymptotically flat except for a cosmic string stretching to infinity that is used to hold the black holes apart. Another cosmic string wraps the non-contractible cycle through the wormhole, and its quantum fluctuations provide the negative energy needed for traversability. Our setting is closely related to the non-perturbative construction of Maldacena, Milekhin, and Popov (MMP), but the analysis is complementary. In particular, we consider cases where back-reaction slows, but fails to halt, the collapse of the wormhole interior, so that the wormhole is traversable only at sufficiently early times. For non-extremal backgrounds, we find the integrated null energy along the horizon of the classical background to be exponentially small, and thus traversability to be exponentially fragile. Nevertheless, if there are no larger perturbations, and for appropriately timed signals, a wormhole with mouths separated by a distance $d$ becomes traversable with a minimum transit time $t_{\text{min transit}} = d + \text{logs}$. Thus $\frac{t_{\text{min transit}}}{d}$ is smaller than for the eternally traversable MMP wormholes by more than a factor of 2, and approaches the value that, at least in higher dimensions, would be the theoretical minimum. For contrast we also briefly consider a `cosmological wormhole' solution where the back-reaction has the opposite sign, so that negative energy from quantum fields makes the wormhole harder to traverse

Triplet lifetime in gaseous argon

MiniCLEAN is a single-phase liquid argon dark matter experiment. During the initial cooling phase, impurities within the cold gas ($<$140 K) were monitored by measuring the scintillation light triplet lifetime, and ultimately a triplet lifetime of 3.480 $\pm$ 0.001 (stat.) $\pm$ 0.064 (sys.) $\mu$s was obtained, indicating ultra-pure argon. This is the longest argon triplet time constant ever reported. The effect of quenching of separate components of the scintillation light is also investigated

Area/Entropy Laws, Traversable Wormholes, and the Connections Between Geometry and Entanglement

We study the relationship between the geometry of spacetime and quantum information. This is motivated by recent insights which suggest that geometry is an emergent phenomenon in quantum gravity, and in particular that geometry is built from quantum entanglement.Part I of this thesis is focused on the relationship between area and entropy. Area/entropy relations are ubiquitous in gravitating systems. One manifestation of this relationship comes from the AdS/CFT correspondence, which posits a duality between quantum gravity in asymptotically Anti-de Sitter space and certain quantum field theories that can be thought of as living on the boundary of the Anti-de Sitter spacetime. When the field theory has a large number of strongly coupled fields, the dual quantum gravity spacetime is described to good approximation by classical General Relativity. In this limit, the Hubeny-Rangamani-Takayanagi (HRT) formula relates the area of surfaces in the bulk spacetime to the entanglement entropy of associated subregions in the dual field theory.A second potential incarnation of the relationship between area and entropy comes in the form of black hole area laws and a more locally-defined generalization known as a holographic screens. We explore connections between these different notions of area and entropy by studying the properties of holographic screens in Anti-de Sitter space. We also study a (modified version) of HRT like surfaces attached to arbitrary boundaries (that need not be an Anti-de Sitter boundary). Part II of this thesis involves the study of traversable wormholes. Physicists have long believed that wormholes that could be crossed by an observer or signal would be impossible to build. In fact it can be shown that, with only classical matter, traversable wormholes cannot exist. While it remained possible that subtle quantum effects might be able to provide the negative energy needed to build them, there were no successful attempts at doing so. Recently, however, examples were constructed in AdS that relied on putting interactions in the dual, entangled quantum systems, and thus illustrated the intimate relation between quantum entanglement and spacetime geometry. Below, we describe a general method by which to construct traversable wormholes that can be applied to any spacetime, including asymptotically flat space. We explicitly construct several examples in AdS and in flat space, and generalize the result to construct multi-mouthed wormholes. We further use these multi-mouthed wormholes to study the entanglement structure of the spacetime they reside in

Marginally trapped surfaces and AdS/CFT

It has been proposed that the areas of marginally trapped or anti-trapped surfaces (also known as leaves of holographic screens) may encode some notion of entropy. To connect this to AdS/CFT, we study the case of marginally trapped surfaces anchored to an AdS boundary. We establish that such boundary-anchored leaves lie between the causal and extremal surfaces defined by the anchor and that they have area bounded below by that of the minimal extremal surface. This suggests that the area of any leaf represents a coarse-grained von Neumann entropy for the associated region of the dual CFT. We further demonstrate that the leading area-divergence of a boundary-anchored marginally trapped surface agrees with that for the associated extremal surface, though subleading divergences generally differ. Finally, we generalize an argument of Bousso and Engelhardt to show that holographic screens with all leaves anchored to the same boundary set have leaf-areas that increase monotonically along the screen, and we describe a construction through which this monotonicity can take the more standard form of requiring entropy to increase with boundary time. This construction is related to what one might call future causal holographic information, which in such cases also provides an upper bound on the area of the associated leaves