19 research outputs found
Exact time dependence of causal correlations and nonequilibrium density matrices in holographic systems
We present the first exact calculations of the time dependence of causal
correlations in driven nonequilibrium states in (2+1)-dimensional systems using
holography. Comparing exact results with those obtained from simple prototype
geometries that are parametrized only by a time dependent temperature, we find
that the universal slowly varying features are controlled just by the pump
duration and the initial and final temperatures only. We provide numerical
evidence that the locations of the event and apparent horizons in the dual
geometries can be deduced from the nonequilibrium causal correlations without
any prior knowledge of the dual gravity theory.Comment: 6 pages + 3 pages supplemental material, 7 figures (colour), v2:
corrected typos, changed colour coding in Fig. 1, v3: to be published in PRD,
Fig. 3 split into Figs. 3 and 4, Fig. 5 added, extended introductio
Entanglement on linked boundaries in Chern-Simons theory with generic gauge groups
We study the entanglement for a state on linked torus boundaries in
Chern-Simons theory with a generic gauge group and present the asymptotic
bounds of R\'enyi entropy at two different limits: (i) large Chern-Simons
coupling , and (ii) large rank of the gauge group. These results show
that the R\'enyi entropies cannot diverge faster than and ,
respectively. We focus on torus links with topological linking number
. The R\'enyi entropy for these links shows a periodic structure in and
vanishes whenever , where the integer
is a function of coupling and rank . We highlight that the
refined Chern-Simons link invariants can remove such a periodic structure in
.Comment: 31 pages, 5 figure
Proposal for measuring out-of-time-ordered correlators at finite temperature with coupled spin chains
Information scrambling, which is the spread of local information through a
system's many-body degrees of freedom, is an intrinsic feature of many-body
dynamics. In quantum systems, the out-of-time-ordered correlator (OTOC)
quantifies information scrambling. Motivated by experiments that have measured
the OTOC at infinite temperature and a theory proposal to measure the OTOC at
finite temperature using the thermofield double state, we describe a protocol
to measure the OTOC in a finite temperature spin chain that is realized
approximately as one half of the ground state of two moderately-sized coupled
spin chains. We consider a spin Hamiltonian with particle-hole symmetry, for
which we show that the OTOC can be measured without needing sign-reversal of
the Hamiltonian. We describe a protocol to mitigate errors in the estimated
OTOC, arising from the finite approximation of the system to the thermofield
double state. We show that our protocol is also robust to main sources of
decoherence in experiments.Comment: 17 pages, 6 figures + References + Appendi