477 research outputs found
Entanglement Entropy: A Perturbative Calculation
We provide a framework for a perturbative evaluation of the reduced density
matrix. The method is based on a path integral in the analytically continued
spacetime. It suggests an alternative to the holographic and `standard' replica
trick calculations of entanglement entropy. We implement this method within
solvable field theory examples to evaluate leading order corrections induced by
small perturbations in the geometry of the background and entangling surface.
Our findings are in accord with Solodukhin's formula for the universal term of
entanglement entropy for four dimensional CFTs.Comment: 28 pages, 3 appendices, 5 figure
Entanglement Entropy for Relevant and Geometric Perturbations
We continue the study of entanglement entropy for a QFT through a
perturbative expansion of the path integral definition of the reduced density
matrix. The universal entanglement entropy for a CFT perturbed by a relevant
operator is calculated to second order in the coupling. We also explore the
geometric dependence of entanglement entropy for a deformed planar entangling
surface, finding surprises at second order.Comment: 18 pages + appendice
Universality of fast quenches from the conformal perturbation theory
We consider global quantum quenches, a protocol when a continuous field
theoretic system in the ground state is driven by a homogeneous time-dependent
external interaction. When the typical inverse time scale of the interaction is
much larger than all relevant scales except for the UV-cutoff the system's
response exhibits universal scaling behavior. We provide both qualitative and
quantitative explanations of this universality and argue that physics of the
response during and shortly after the quench is governed by the conformal
perturbation theory around the UV fixed point. We proceed to calculate the
response of one and two-point correlation functions confirming and generalizing
universal scalings found previously. Finally, we discuss late time behavior
after the quench and argue that all local quantities will equilibrate to their
thermal values specified by an excess energy acquired by the system during the
quench.Comment: published version, refs added, minor typos corrected, 38 pages, no
fgiure
On fast quenches and spinning correlators
We study global quantum quenches in a continuous field theoretic system with
UV fixed point. Assuming that the characteristic inverse time scale of the
smooth quench is much larger than all scales inherent to the system except for
the UV-cutoff, we derive the universal scaling behavior of the two-point
correlation functions associated with Dirac fields and spin-1 currents. We
argue that in certain regimes our results can be recovered using the technique
of operator product expansion.Comment: 28 pages, no figure
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