9 research outputs found
Analyzing Multi-Field Tunneling With Exact Bounce Solutions
We study multi-field tunneling using exact solutions for additive potentials.
We introduce a binomial potential with non-integer powers that could be
considered a generalization of the Fubini instanton potential. Using
scaling arguments, we show that for multi-field potentials taller and wider
barriers may still lead to a smaller bounce action.Comment: 16 pages, 2 figures, 1 tabl
Quantum information probes of charge fractionalization in large-N gauge theories
We study in detail various information theoretic quantities with the intent of distinguishing between different charged sectors in fractionalized states of large-N gauge theories. For concreteness, we focus on a simple holographic (2 + 1)-dimensional strongly coupled electron fluid whose charged states organize themselves into fractionalized and coherent patterns at sufficiently low temperatures. However, we expect that our results are quite generic and applicable to a wide range of systems, including non-holographic. The probes we consider include the entanglement entropy, mutual information, entanglement of purification and the butterfly velocity. The latter turns out to be particularly useful, given the universal connection between momentum and charge diffusion in the vicinity of a black hole horizon. The RT surfaces used to compute the above quantities, though, are largely insensitive to the electric flux in the bulk. To address this deficiency, we propose a generalized entanglement functional that is motivated through the Iyer-Wald formalism, applied to a gravity theory coupled to a U(1) gauge field. We argue that this functional gives rise to a coarse grained measure of entanglement in the boundary theory which is obtained by tracing over (part) of the fractionalized and cohesive charge degrees of freedom. Based on the above, we construct a candidate for an entropic c-function that accounts for the existence of bulk charges. We explore some of its general properties and their significance, and discuss how it can be used to efficiently account for charged degrees of freedom across different energy scales.Peer reviewe
Holographic constraints on Bjorken hydrodynamics at finite coupling
In large-N-c conformal field theories with classical holographic duals, inverse coupling constant corrections are obtained by considering higher-derivative terms in the corresponding gravity theory. In this work, we use type IIB supergravity and bottom-up Gauss-Bonnet gravity to study the dynamics of boost-invariant Bjorken hydrodynamics at finite coupling. We analyze the time-dependent decay properties of non-local observables (scalar two-point functions and Wilson loops) probing the different models of Bjorken flow and show that they can be expressed generically in terms of a few field theory parameters. In addition, our computations provide an analytically quanti fiable probe of the coupling-dependent validity of hydrodynamics at early times in a simple model of heavyion collisions, which is an observable closely analogous to the hydrodynamization time of a quark-gluon plasma. We find that to third order in the hydrodynamic expansion, the convergence of hydrodynamics is improved and that generically, as expected from field theory considerations and recent holographic results, the applicability of hydrodynamics is delayed as the field theory coupling decreases.Peer reviewe
The Volume Inside a Black Hole
The horizon (the surface) of a black hole is a null surface, defined by those
hypothetical "outgoing" light rays that just hover under the influence of the
strong gravity at the surface. Because the light rays are orthogonal to the
spatial 2-dimensional surface at one instant of time, the surface of the black
hole is the same for all observers (i.e. the same for all coordinate
definitions of "instant of time"). This value is 4*(pi)* (2Gm/c^2)^2 for
nonspinning black holes, with G= Newton's constant, c= speed of light, and m=
mass of the black hole.
The 3-dimensional spatial volume inside a black hole, in contrast, depends
explicitly on the definition of time, and can even be time dependent, or zero.
We give examples of the volume found inside a standard, nonspinning spherical
black hole, for several different standard time-coordinate definitions.
Elucidating these results for the volume provides a new pedagogical resource of
facts already known in principle to the relativity community, but rarely worked
out.Comment: 17 pages, 5 figure
Holographic zero sound at finite temperature in the Sakai-Sugimoto model
In this paper, we study the fate of the holographic zero sound mode at finite
temperature and non-zero baryon density in the deconfined phase of the
Sakai-Sugimoto model of holographic QCD. We establish the existence of such a
mode for a wide range of temperatures and investigate the dispersion relation,
quasi-normal modes, and spectral functions of the collective excitations in
four different regimes, namely, the collisionless quantum, collisionless
thermal, and two distinct hydrodynamic regimes. For sufficiently high
temperatures, the zero sound completely disappears, and the low energy physics
is dominated by an emergent diffusive mode. We compare our findings to
Landau-Fermi liquid theory and to other holographic models.Comment: 1+24 pages, 19 figures, PDFTeX, v2: some comments and references
added, v3: some clarifications relating to the different regimes added,
matches version accepted for publication in JHEP, v4: corrected typo in eq.
(3.18