323 research outputs found
Mixed global anomalies and boundary conformal field theories
We consider the relation of mixed global gauge gravitational anomalies and
boundary conformal field theory in WZW models for simple Lie groups. The
discrete symmetries of consideration are the centers of the simple Lie groups.
These mixed anomalies prevent to gauge them i.e, take the orbifold by the
center. The absence of anomalies impose conditions on the levels of WZW models.
Next, we study the conformal boundary conditions for the original theories. We
consider the existence of a conformal boundary state invariant under the action
of the center. This also gives conditions on the levels of WZW models. By
considering the combined action of the center and charge conjugation on
boundary states, we reproduce the condition obtained in the orbifold analysis.Comment: 24pages, 1 figure, references adde
Quantum Entanglement of Fermionic Local Operators
In this paper we study the time evolution of (Renyi) entanglement entropies
for locally excited states in four dimensional free massless fermionic field
theory. Locally excited states are defined by being acted by various local
operators on the ground state. Their excesses are defined by subtracting
(Renyi) entanglement entropy for the ground state from those for locally
excited states. They finally approach some constant if the subsystem is given
by half of the total space. They have spin dependence. They can be interpreted
in terms of quasi-particles.Comment: 29pages, 7 figure
Notes on Entanglement Entropy in String Theory
In this paper, we study the entanglement entropy in string theory in the
simplest setup of dividing the nine dimensional space into two halves. This
corresponds to the leading quantum correction to the horizon entropy in string
theory on the Rindler space. This entropy is also called the conical entropy
and includes surface term contributions. We first derive a new simple formula
of the conical entropy for any free higher spin fields. Then we apply this
formula to computations of conical entropy in open and closed superstring. In
our analysis of closed string, we study the twisted conical entropy defined by
making use of string theory on Melvin backgrounds. This quantity is easier to
calculate owing to the folding trick. Our analysis shows that the entanglement
entropy in closed superstring is UV finite owing to the string scale cutoff.Comment: 27 pages, no figures, latex, v2: typos corrected, references adde
EPR Pairs, Local Projections and Quantum Teleportation in Holography
In this paper we analyze three quantum operations in two dimensional
conformal field theories (CFTs): local projection measurements, creations of
partial entanglement between two CFTs, and swapping of subsystems between two
CFTs. We also give their holographic duals and study time evolutions of
entanglement entropy. By combining these operations, we present an analogue of
quantum teleportation between two CFTs and give its holographic realization. We
introduce a new quantity to probe tripartite entanglement by using local
projection measurement.Comment: 61 pages, 24 figures. v2: comments and refs added. v3: minor
correction
Quantum Dimension as Entanglement Entropy in 2D CFTs
We study entanglement entropy of excited states in two dimensional conformal
field theories (CFTs). Especially we consider excited states obtained by acting
primary operators on a vacuum. We show that under its time evolution,
entanglement entropy increases by a finite constant when the causality
condition is satisfied. Moreover, in rational CFTs, we prove that this
increased amount of (both Renyi and von-Neumann) entanglement entropy always
coincides with the log of quantum dimension of the primary operator.Comment: 5 pages, 3 eps figures, Revte
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