76 research outputs found
The Information Metric on the moduli space of instantons with global symmetries
In this note we revisit Hitchin's prescription \cite{Hitchin} of the Fisher
metric as a natural measure on the moduli space of instantons that encodes the
space-time symmetries of a classical field theory. Motivated by the idea of the
moduli space of supersymmetric instantons as an emergent space in the sense of
the gauge/gravity duality, we extend the prescription to encode also global
symmetries of the underlying theory. We exemplify our construction with the
instanton solution of the sigma model on .Comment: 5 pages, no figures, sorr
The open string membrane paradigm with external electromagnetic fields
We study the effective geometry felt by the fluctuations of open strings
living on the worldvolume of probe D-branes in the presence of background
electromagnetic fields. This is captured by an effective action consisting of a
Maxwell term and a topological term, with the role of the metric played by the
open string metric. Studying generalized Eddington-Finkelstein coordinates for
stationary but non-static manifolds, we consider an open string membrane
paradigm to obtain a generic formula for the DC transport coefficients,
including the effect of external electromagnetic fields present on the
worldvolume of the probe branes. We show that the previously studied singular
shell, present when a critical electric field strength is turned on, behaves as
a horizon for the open string degrees of freedom. The results of this analysis
can be used to define a membrane paradigm for a very general class of
spacetimes with non-diagonal metrics.Comment: 31 pages, 3 figures, v2: Appendix added, minor correction
Entanglement entropy of -vacua in de Sitter space
We consider the entanglement entropy of a free massive scalar field in the
one parameter family of -vacua in de Sitter space by using a method
developed by Maldacena and Pimentel. An -vacuum can be thought of as a
state filled with particles from the point of view of the Bunch-Davies vacuum.
Of all the -vacua we find that the entanglement entropy takes the
minimal value in the Bunch-Davies solution. We also calculate the asymptotic
value of the R\'enyi entropy and find that it increases as increases.
We argue these feature stem from pair condensation within the non-trivial
-vacua where the pairs have an intrinsic quantum correlation.Comment: 23 pages, 6 figures. Two figures and references adde
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