42 research outputs found
Chern-Simons-like Theories of Gravity
In this PhD thesis, we investigate a wide class of three-dimensional massive
gravity models and show how most of them (if not all) can be brought in a
first-order, Chern-Simons-like, formulation. This allows for a general analysis
of the Hamiltonian for this wide class of models. From the Chern-Simons-like
perspective, the known higher-derivative theories of 3D massive gravity, like
Topologically Massive Gravity and New Massive Gravity, can be extended to a
wider class of models. These models are shown to be free of (possibly
ghost-like) scalar excitations and exhibit improved behavior with respect to
Anti-de Sitter holography; the new models have regions in their parameter space
where positive boundary central charge is compatible with positive mass and
energy for the massive spin-2 mode. We discuss the construction of several of
these improved models in detail and derive the necessary constraints needed to
remove any unphysical degree of freedom. We also comment on the AdS/LCFT
correspondence which arises when the massive spin-2 mode becomes massless and
is replaced by a logarithmic mode. Most of the results have been published
elsewhere, however, a special effort is made here to present the aspects of
Chern-Simons-like theories in a pedagogical and comprehensive way.Comment: 201 pages, 3 figures, PhD thesis defended at the University of
Groningen on September 26, 2014. Contains results previously obtained in
arXiv:1307.2774, arXiv:1401.5386, arXiv:1402.1688, arXiv:1404.2867,
arXiv:1405.6213 and arXiv:1410.616
Soft hairy warped black hole entropy
We reconsider warped black hole solutions in topologically massive gravity
and find novel boundary conditions that allow for soft hairy excitations on the
horizon. To compute the associated symmetry algebra we develop a general
framework to compute asymptotic symmetries in any Chern-Simons-like theory of
gravity. We use this to show that the near horizon symmetry algebra consists of
two u(1) current algebras and recover the surprisingly simple entropy formula
, where are zero mode charges of the current
algebras. This provides the first example of a locally non-maximally symmetric
configuration exhibiting this entropy law and thus non-trivial evidence for its
universality.Comment: 24pp, v2: added appendix C and minor edit
Most general flat space boundary conditions in three-dimensional Einstein gravity
We consider the most general asymptotically flat boundary conditions in
three-dimensional Einstein gravity in the sense that we allow for the maximal
number of independent free functions in the metric, leading to six towers of
boundary charges and six associated chemical potentials. We find as associated
asymptotic symmetry algebra an isl(2)_k current algebra. Restricting the
charges and chemical potentials in various ways recovers previous cases, such
as BMS_3, Heisenberg or Detournay-Riegler, all of which can be obtained as
contractions of corresponding AdS_3 constructions. Finally, we show that a flat
space contraction can induce an additional Carrollian contraction. As examples
we provide two novel sets of boundary conditions for Carroll gravity.Comment: 23 pp, invited for CQG BMS Focus Issue edited by Geoffrey Compere,
v2: added minor clarifications and ref
Stress tensor correlators in three-dimensional gravity
We calculate holographically arbitrary n-point correlators of the boundary
stress tensor in three-dimensional Einstein gravity with negative or vanishing
cosmological constant. We provide explicit expressions up to 5-point
(connected) correlators and show consistency with the Galilean conformal field
theory Ward identities and recursion relations of correlators, which we derive.
This provides a novel check of flat space holography in three dimensions.Comment: 6 pages, v2: corrected sign
Logistic growth on networks: exact solutions for the SI model
The SI model is the most basic of all compartmental models used to describe
the spreading of information through a population. Despite its apparent
simplicity, the analytic solution of this model on networks is still lacking.
We address this problem here, using a novel formulation inspired by the
mathematical treatment of many-body quantum systems. This allows us to organize
the time-dependent expectation values for the state of individual nodes in
terms of contributions from subgraphs of the network. We compute these
contributions systematically and find a set of symmetry relations among
subgraphs of differing topologies. We use our novel approach to compute the
spreading of information on three different sample networks. The exact
solution, which matches with Monte-Carlo simulations, visibly departs from the
mean-field results.Comment: 15 pages, 4 figures, accompanied by a software package at
https://doi.org/10.6084/m9.figshare.14872182.v4. v2: extended explanation and
incorporated supplemental material into the main text. Accepted for
publication in Phys.Rev.
Extended massive gravity in three dimensions
Using a first order Chern-Simons-like formulation of gravity we
systematically construct higher-derivative extensions of general relativity in
three dimensions. The construction ensures that the resulting higher-derivative
gravity theories are free of scalar ghosts. We canonically analyze these
theories and construct the gauge generators and the boundary central charges.
The models we construct are all consistent with a holographic c-theorem which,
however, does not imply that they are unitary. We find that Born-Infeld gravity
in three dimensions is contained within these models as a subclass.Comment: 35p, v2; minor changes, references adde
Supersymmetric Galilean conformal blocks
We set up the bootstrap procedure for supersymmetric Galilean Conformal (SGC)
field theories in two dimensions by constructing the SGC blocks in the
and two possible extensions of the Galilean
conformal algebra. In all analyzed cases, we present the bootstrap equations by
crossing symmetry of the four point function. In addition, we compute the
global SGC blocks analytically by solving the differential equations obtained
by acting with the Casimirs of the global subalgebras inside the four point
function. These global blocks agree with the general SGC blocks in the limit of
large central charge. We comment on possible applications to supersymmetric
BMS invariant field theories and flat holography.Comment: 43 pages, v2: references added and typos fixed, v3: refs added, minor
errors in the expression for the despotic blocks fixed. Matches published
versio
Emergent information dynamics in many-body interconnected systems
The information implicitly represented in the state of physical systems
allows one to analyze them with analytical techniques from statistical
mechanics and information theory. In the case of complex networks such
techniques are inspired by quantum statistical physics and have been used to
analyze biophysical systems, from virus-host protein-protein interactions to
whole-brain models of humans in health and disease. Here, instead of node-node
interactions, we focus on the flow of information between network
configurations. Our numerical results unravel fundamental differences between
widely used spin models on networks, such as voter and kinetic dynamics, which
cannot be found from classical node-based analysis. Our model opens the door to
adapting powerful analytical methods from quantum many-body systems to study
the interplay between structure and dynamics in interconnected systems.Comment: 7 pages, 3 figure
Logarithmic AdS Waves and Zwei-Dreibein Gravity
We show that the parameter space of Zwei-Dreibein Gravity (ZDG) in AdS3
exhibits critical points, where massive graviton modes coincide with pure gauge
modes and new `logarithmic' modes appear, similar to what happens in New
Massive Gravity. The existence of critical points is shown both at the
linearized level, as well as by finding AdS wave solutions of the full
non-linear theory, that behave as logarithmic modes towards the AdS boundary.
In order to find these solutions explicitly, we give a reformulation of ZDG in
terms of a single Dreibein, that involves an infinite number of derivatives. At
the critical points, ZDG can be conjectured to be dual to a logarithmic
conformal field theory with zero central charges, characterized by new
anomalies whose conjectured values are calculated.Comment: 20 page