275,208 research outputs found
Entanglement in a fermion chain under continuous monitoring
We study the entanglement entropy of the quantum trajectories of a free
fermion chain under continuous monitoring of local occupation numbers. We
propose a simple theory for entanglement entropy evolution from disentangled
and highly excited initial states. It is based on generalized hydrodynamics and
the quasi-particle pair approach to entanglement in integrable systems. We test
several quantitative predictions of the theory against extensive numerics and
find good agreement. In particular, the volume law entanglement is destroyed by
the presence of arbitrarily weak measurement.Comment: 18 pages, 8 figures, 2 new figure
Chemical Potential in the First Law for Holographic Entanglement Entropy
Entanglement entropy in conformal field theories is known to satisfy a first
law. For spherical entangling surfaces, this has been shown to follow via the
AdS/CFT correspondence and the holographic prescription for entanglement
entropy from the bulk first law for Killing horizons. The bulk first law can be
extended to include variations in the cosmological constant , which we
established in earlier work. Here we show that this implies an extension of the
boundary first law to include varying the number of degrees of freedom of the
boundary CFT. The thermodynamic potential conjugate to in the bulk is
called the thermodynamic volume and has a simple geometric formula. In the
boundary first law it plays the role of a chemical potential. For the bulk
minimal surface corresponding to a boundary sphere, the thermodynamic
volume is found to be proportional to the area of , in agreement with
the variation of the known result for entanglement entropy of spheres. The
dependence of the CFT chemical potential on the entanglement entropy and number
of degrees of freedom is similar to how the thermodynamic chemical potential of
an ideal gas depends on entropy and particle number.Comment: 18 pages; v2 - reference adde
Volume Law for the Entanglement Entropy in Non-local QFTs
In this paper, we present a simple class of non-local field theories whose
ground state entanglement entropy follows a volume law as long as the size of
subsystem is smaller than a certain scale. We will confirm this volume law both
from numerical calculations and from analytical estimation. This behavior fits
nicely with holographic results for spacetimes whose curvatures are much
smaller than AdS spaces such as those in the flat spacetime.Comment: 18 pages, 3 figures; v2, added reference
No-Bang Quantum State of the Cosmos
A quantum state of the entire cosmos (universe or multiverse) is proposed
which is the equal mixture of the Giddings-Marolf states that are
asymptotically single de Sitter spacetimes in both past and future and are
regular on the throat or neck of minimal three-volume. That is, states are
excluded that have a big bang or big crunch or which split into multiple
asymptotic de Sitter spacetimes. (For simplicity, transitions between different
values of the cosmological constant are assumed not to occur, though different
positive values are allowed.) The entropy of this mixed state appears to be of
the order of the three-fourths power of the Bekenstein-Hawking A/4 entropy of
de Sitter spacetime. Most of the component pure states do not have rapid
inflation, but when an inflaton is present and the states are weighted by the
volume at the end of inflation, a much smaller number of states may dominate
and give a large amount of inflation and hence may agree with observations.Comment: 18 pages, LaTeX, updated with a few new qualifications and reference
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