14 research outputs found
Counting paths with Schur transitions
In this work we explore the structure of the branching graph of the unitary
group using Schur transitions. We find that these transitions suggest a new
combinatorial expression for counting paths in the branching graph. This
formula, which is valid for any rank of the unitary group, reproduces known
asymptotic results. We proceed to establish the general validity of this
expression by a formal proof. The form of this equation strongly hints towards
a quantum generalization. Thus, we introduce a notion of quantum relative
dimension and subject it to the appropriate consistency tests. This new
quantity finds its natural environment in the context of RCFTs and fractional
statistics; where the already established notion of quantum dimension has
proven to be of great physical importance.Comment: 30 pages, 5 figure
Spinning probes and helices in AdS
We study extremal curves associated with a functional which is linear in the
curve's torsion. The functional in question is known to capture the properties
of entanglement entropy for two-dimensional conformal field theories with
chiral anomalies and has potential applications in elucidating the equilibrium
shape of elastic linear structures. We derive the equations that determine the
shape of its extremal curves in general ambient spaces in terms of geometric
quantities. We show that the solutions to these shape equations correspond to a
three-dimensional version of Mathisson's helical motions for the centers of
mass of spinning probes. Thereafter, we focus on the case of maximally
symmetric spaces, where solutions correspond to cylindrical helices and find
that the Lancret ratio of these equals the relative speed between the
Mathisson-Pirani and the Tulczyjew-Dixon observers. Finally, we construct all
possible helical motions in three-dimensional manifolds with constant negative
curvature. In particular, we discover a rich space of helices in AdS which
we explore in detail.Comment: 28 pages, 5 figure
On the Shape of Things: From holography to elastica
We explore the question of which shape a manifold is compelled to take when
immersed in another one, provided it must be the extremum of some functional.
We consider a family of functionals which depend quadratically on the extrinsic
curvatures and on projections of the ambient curvatures. These functionals
capture a number of physical setups ranging from holography to the study of
membranes and elastica. We present a detailed derivation of the equations of
motion, known as the shape equations, placing particular emphasis on the issue
of gauge freedom in the choice of normal frame. We apply these equations to the
particular case of holographic entanglement entropy for higher curvature three
dimensional gravity and find new classes of entangling curves. In particular,
we discuss the case of New Massive Gravity where we show that non-geodesic
entangling curves have always a smaller on-shell value of the entropy
functional. Then we apply this formalism to the computation of the entanglement
entropy for dual logarithmic CFTs. Nevertheless, the correct value for the
entanglement entropy is provided by geodesics. Then, we discuss the importance
of these equations in the context of classical elastica and comment on terms
that break gauge invariance.Comment: 54 pages, 8 figures. Significantly improved version, accepted for
publication in Annals of Physics. New section on logarithmic CFTs. Detailed
derivation of the shape equations added in appendix B. Typos corrected,
clarifications adde
Graph duality as an instrument of Gauge-String correspondence
We explore an identity between two branching graphs and propose a physical
meaning in the context of the gauge-gravity correspondence. From the
mathematical point of view, the identity equates probabilities associated with
, the branching graph of the unitary groups, with probabilities
associated with , the branching graph of the symmetric groups. In
order to furnish the identity with physical meaning, we exactly reproduce these
probabilities as the square of three point functions involving certain
hook-shaped backgrounds. We study these backgrounds in the context of LLM
geometries and discover that they are domain walls interpolating two AdS spaces
with different radii. We also find that, in certain cases, the probabilities
match the eigenvalues of some observables, the embedding chain charges. We
finally discuss a holographic interpretation of the mathematical identity
through our results.Comment: 34 pages. version published in journa
Renormalized Entanglement Entropy for BPS Black Branes
We compute the renormalized entanglement entropy (REE) for BPS black
solutions in , 4d gauged supergravity. We find that this quantity
decreases monotonically with the size of the entangling region until it reaches
a critical point, then increases and approaches the entropy density of the
brane. This behavior can be understood as a consequence of the REE being driven
by two competing factors, namely entanglement and the mixedness of the black
brane. In the UV entanglement dominates, whereas in the IR the mixedness takes
over.Comment: 6 pages, 4 figures; v2: Typos fixed, citation and clarifying text
added, version accepted in Physical Review
Quantum corrections to extremal black brane solutions
We discuss quantum corrections to extremal black brane solutions in N=2 U(1)
gauged supergravity in four dimensions. We consider modifications due to a
certain class of higher-derivative terms as well as perturbative corrections to
the prepotential. We use the entropy function formalism to assess the impact of
these corrections on singular brane solutions and we give a few examples. We
then use first-order flow equations to construct solutions that interpolate
between quantum corrected fixed points of the associated potentials.Comment: 30 pages, 10 figures; v2: references added, as well as a discussion
about how to obtain the attractor equations by extremizing an effective
potential, coincides with published versio