1,098 research outputs found
Holographic studies of Einsteinian cubic gravity
Einsteinian cubic gravity provides a holographic toy model of a
nonsupersymmetric CFT in three dimensions, analogous to the one defined by
Quasi-topological gravity in four. The theory admits explicit non-hairy AdS
black holes and allows for numerous exact calculations, fully nonperturbative
in the new coupling. We identify several entries of the AdS/CFT dictionary for
this theory, and study its thermodynamic phase space, finding interesting new
phenomena. We also analyze the dependence of R\'enyi entropies for disk regions
on universal quantities characterizing the CFT. In addition, we show that
is given by a non-analytic function of the ECG coupling, and that the
existence of positive-energy black holes strictly forbids violations of the KSS
bound. Along the way, we introduce a new method for evaluating Euclidean
on-shell actions for general higher-order gravities possessing second-order
linearized equations on AdS. Our generalized action involves the very
same Gibbons-Hawking boundary term and counterterms valid for Einstein gravity,
which now appear weighted by the universal charge controlling the
entanglement entropy across a spherical region in the CFT dual to the
corresponding higher-order theory.Comment: 59 pages, 7 figures, 1 table; v4: typos fixe
Bounds on corner entanglement in quantum critical states
The entanglement entropy in many gapless quantum systems receives a
contribution from corners in the entangling surface in 2+1d. It is
characterized by a universal function depending on the opening
angle , and contains pertinent low energy information. For conformal
field theories (CFTs), the leading expansion coefficient in the smooth limit
yields the stress tensor 2-point function coefficient .
Little is known about beyond that limit. Here, we show that the
next term in the smooth limit expansion contains information beyond the 2- and
3-point correlators of the stress tensor. We conjecture that it encodes 4-point
data, making it much richer. Further, we establish strong constraints on this
and higher order smooth-limit coefficients. We also show that is
lower-bounded by a non-trivial function multiplied by the central charge
, e.g. . This bound for 90-degree corners is
nearly saturated by all known results, including recent numerics for the
interacting Wilson-Fisher quantum critical points (QCPs). A bound is also given
for the R\'enyi entropies. We illustrate our findings using O(N) QCPs, free
boson and Dirac fermion CFTs, strongly coupled holographic ones, and other
models. Exact results are also given for Lifshitz quantum critical points, and
for conical singularities in 3+1d.Comment: 10 + 8 pages, 6 figures, 1 + 2 tables. v2: refs added, minor change
Holographic torus entanglement and its RG flow
We study the universal contributions to the entanglement entropy (EE) of 2+1d
and 3+1d holographic conformal field theories (CFTs) on topologically
non-trivial manifolds, focusing on tori. The holographic bulk corresponds to
AdS-soliton geometries. We characterize the properties of these
regulator-independent EE terms as a function of both the size of the
cylindrical entangling region, and the shape of the torus. In 2+1d, in the
simple limit where the torus becomes a thin 1d ring, the EE reduces to a
shape-independent constant . This is twice the EE obtained by
bipartitioning an infinite cylinder into equal halves. We study the RG flow of
by defining a renormalized EE that 1) is applicable to general QFTs,
2) resolves the failure of the area law subtraction, and 3) is inspired by the
F-theorem. We find that the renormalized decreases monotonically when
the holographic CFT is deformed by a relevant operator for all allowed scaling
dimensions. We also discuss the question of non-uniqueness of such renormalized
EEs both in 2+1d and 3+1d.Comment: 22 pages, 11 figures, v2: minor changes, refs. adde
Universal entanglement for higher dimensional cones
The entanglement entropy of a generic -dimensional conformal field theory
receives a regulator independent contribution when the entangling region
contains a (hyper)conical singularity of opening angle , codified in a
function . In arXiv:1505.04804, we proposed that for
three-dimensional conformal field theories, the coefficient
characterizing the smooth surface limit of such contribution
() equals the stress tensor two-point function charge
, up to a universal constant. In this paper, we prove this relation for
general three-dimensional holographic theories, and extend the result to
general dimensions. In particular, we show that a generalized coefficient
can be defined for (hyper)conical entangling regions in the
almost smooth surface limit, and that this coefficient is universally related
to for general holographic theories, providing a general formula for
the ratio in arbitrary dimensions. We conjecture that
the latter ratio is universal for general CFTs. Further, based on our recent
results in arXiv:1507.06997, we propose an extension of this relation to
general R\'enyi entropies, which we show passes several consistency checks in
and .Comment: 22 pages, 3 figures, 2 tables; v3: minor modifications to match
published version, references adde
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