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Black
Holes VIII
Theory and
Mathematical Aspects
May 10-14
2011
Niagara
Falls, Ontario, Canada
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Perturbations of large AdS black holes and the
fluid/gravity correspondence
Aida Ahmadzadegan
The canonical form of the perturbation metric of
anti-de Sitter black holes in four dimensions is derived by choosing the Regge-Wheeler gauge in the standard Schwarzschild
coordinates (t, r, ϑ, ϕ). By assuming the perturbations to be small, the differential equations
governing the perturbations are obtained from the equations δRν(h)=0. Then, by taking the limit of m>>R
where R is the radius of AdS space, the perturbation
metric and field equations of large AdS black holes
are found. Finally, under the shadow of AdS/CFT
correspondence, these perturbations can be compared to their corresponding
three-dimensional theory of fluid dynamics in the dual space.
Geometric Properties of Static EMdL Horizons
Shohreh Abdolrahimi
We study non-degenerate and degenerate (extremal)
Killing horizons of arbitrary geometry and topology within the
Einstein-Maxwell-dilaton model with a Liouville potential (the EMdL model) in
d-dimensional (d>=4) static space-times. Using Israel's description of a
static space-time, we construct the EMdL equations and the space-time curvature
invariants: the Ricci scalar, the square of the Ricci tensor, and the
Kretschmann scalar. Assuming that space-time metric functions and the model
fields are real analytic functions in the vicinity of a space-time horizon, we
study behavior of the space-time metric and the fields near the horizon and
derive relations between the space-time curvature invariants calculated on the
horizon and geometric invariants of the horizon surface. The derived relations
generalize the similar relations known for horizons of static four and
5-dimensional vacuum and 4-dimensional electrovacuum space-times. Our analysis
shows that all the extremal horizon surfaces are Einstein spaces. We present
necessary conditions for existence of static extremal horizons within the EMdL
model.
Particle Dynamics in Weakly Charged Extreme Kerr
Throat
Abdallah Al Zahrani
We discuss dynamics of a test charged particle
moving in a weakly charged extreme Kerr throat. Dynamical equations of the
particle motion are solved in quadratures. We show
explicitly that the Killing tensor of the Kerr spacetime
becomes reducible in the extreme Kerr throat geometry. Special types of motion
of particles and light are discussed.
Black holes in bigravity
Max Banados
Dynamical black holes: lessons from the
fluid-gravity correspondence
Ivan Booth
For stationary black holes it is universally agreed
that entropy is proportional to horizon area. It is not so clear what the
relationship is for dynamical black holes. In such spacetimes
the event horizon is teleologically defined while the
apparent horizon is non-unique. Thus even if one believes that entropy
continues to be well-defined and proportional to horizon area, there are many
possible areas to choose from. In this work I will review some recent work that
I have done with M. Heller, G. Plewa and M. Spalinski that examines this issue from the perspective of
the fluid-gravity correspondence. In this quasi-equilibrium regime the slowly
evolving black brane horizons on the gravity side are
dual to a perturbed fluid flow. The fluid manifestations of the various horizon
definitions can be compared and the black brane
mechanics is dual to hydro-thermodynamics. In particular, the uncertainty as to
which is the "correct" horizon can be interpreted as dual to the
inherent freedom in defining an entropy current.
Quasi-Topological Lifshitz Black Holes
Wilson Brenna
I will present some work on the mixture of
quasi-topological cubic curvature terms with an asymptotically Lifshitz metric,
in the context of a potential dual theory between condensed matter physics and
gravitation. Solutions for black holes with and without matter were found and
the resulting thermodynamics of these objects were studied. In addition, an
interesting relationship between quasi-topological gravity and Lovelock gravity
will be presented.
Low frequency gravitational wave telescopes
Latham Boyle
Astrophysical Black Hole Mergers
Manuela Campanelli
The field of numerical relativity experienced a
phenomenal growth spurt during the past five years. The field transformed
from one in which the two-body problem, that is the merger of black-hole
binaries, was impossible to solve to one where simulations of merging
black-holes are routine. This led to an explosion of exciting new
results. Among the most remarkable of them are the discovery that a merging
black-hole binary can recoil up to 4000 km/s, the orbital hang-up effect, and
the simulation of extreme mass-ratio and extreme spin binaries. The detection
gravitational wave signals from these sources will constitute a major
breakthrough, opening a new window on the universe. I will cover the
latest achievements and highlight the field's next challenges with emphasis on
applications to gravitational wave astrophysics, with both current and future
generation detectors, and electromagnetic observations.
The field of Status of LIGO, and a
Search for Sub-Solar Mass BHs
Kipp Cannon
I'll present a status update on LIGO and the global
network of ground-based laser interferometer gravitational-wave antennas,
including a timeline for the upgrade to Advanced LIGO and what that means. Next
I'll describe work I'm doing to lay the groundwork for the detection of binary
neutron star mergers with Advanced LIGO. Finally, I'll explain how to
determine if the gravitational-wave emission of some source might be detectable
in a gravitational-wave antenna..
Lifshitz spacetimes: a cautionary tale
Keith Copsey
There has been significant interest in the last
several years in studying possible gravitational duals, known as Lifshitz spacetimes, to anisotropically scaling field theories by adding matter to
distort the asymptotics of an asymptotically anti-de
Sitter spacetime and a significant amount of work has
been done constructing black hole solutions with these asymptotics.
I'll discuss some unexpected fundamental problems these spacetimes
have, including the apparent absence of a well-defined ground state for the flat-section
case and the fact that generic perturbations to all these spacetimes,
including ones with black holes, evolve to violate the desired boundary
conditions. I'll also discuss the rather peculiar behavior
of the mass of a numer of asymptotically Lifshitz solutions, including neutral black holes whose
mass is independent of their size.
What can quasinormal modes tell us about the short scale analytic
structure of black holes?
Ramin Daghigh
We analytically calculate the quasinormal modes
of a quantum-corrected black hole in the infinite damping limit.
This calculation reveals the existence of a deep connection between the short
scale analytic structure of black hole spacetimes and the highly damped
quasinormal modes.
Some aspects of quantum gravity phenomenology
Saurya Das
We explore potential experimental signatures of
various theories of quantum gravity on some low energy systems. We also discuss
experiments which may be able to test Modified Newtonian Dynamics (MOND).
Cauchy Horizon Stability in the Self-Similar LTB
Spacetime
Emily Duffy
We undertake a rigorous study of the behaviour of
even parity linear perturbations in the naked self-similar Lemaitre-Tolman-Bondi spacetimes.
Should such perturbations diverge on the Cauchy horizon, this would support the
hypothesis of cosmic censorship for this spacetime.
We use a combination of energy methods and asymptotic analysis to determine the
growth and asymptotic behaviour of the perturbations as they evolve through the
spacetime. We first determine the behaviour of a kind
of average of the perturbations, and use this to produce a hypothesis as to the
form of the perturbations as the Cauchy horizon is approached. Finally, we use
this hypothesis to determine the pointwise asymptotic
behaviour of the perturbations as the Cauchy horizon is approached. Finally, we
use the perturbed Weyl scalars to give a physical
interpretation of these results. We briefly discuss the behaviour of odd parity
perturbations of the same spacetime.
Self-similar
cylindrical spacetimes coupled to a scalar field
Condron Eoin
We investigate self-similar scalar field solutions
to the Einstein equations in whole cylinder symmetry and consider the cosmic
censorship hypothesis in the context of this class of spacetimes.
In self-similar spacetimes the Einstein equations
reduce to a set of ODEs. Furthermore, due to self-similarity, the scalar field
potential must have an exponential form. We discuss the number of degrees of
freedom at an arbitrary point. We show the existence and uniqueness of
solutions where initial data is taken along the axis of symmetry. We prove
that, depending on the choice of parameters and intial
data for the problem, one of the following outcomes arise:
(i) The solution extends to null infinty, which
coincides with the past null cone of the origin.
(ii) The solution becomes singular.
(iii) The solution extends to a regular past null cone.
This last case requires the extension of the solution beyond the past null cone
of the origin. We join the regions either side of this hypersurface
using the spacetime junction conditions. The
behaviour of solutions in the region beyond the past null cone is then
discussed. This is a joint work with Dr. Brien Nolan.
Scalar-tensor/f(R) black holes and the
thermodynamics of spacetime
Valerio Faraoni
Hawking's theorem approximately stating that
“Brans-Dicke black holes are the same as those of general relativity'” seems to
conflict with the failure of the Jebsen-Birkhoff theorem in scalar-tensor and
metric f(R) gravity and with certain analytical solutions of these theories.
This apparent contradiction is clarified and Hawking's theorem extended. The
latter is compatible with the thermodynamics of spacetime idea that GR is a
state of thermodynamical equilibrium in a wider spectrum of gravitational
theories.
Collapse in Modified Gravity
Andrei Frolov
Brane Holes
Valeri Frolov
Black holes and branes
are extended relativistic objects. Their interaction results in many
interesting effects which we discuss in this talk. We assume that branes are thin and neglect their gravitational field. In
this approximation the branes are described by Nambu-Goto action. The problem of the brane--black-hole
interaction in this approximation is reduced to finding minimal surfaces in the
gravitational black hole background. I plan to discuss the following subjects:
(1) Dynamics of a cosmic string interacting with a black hole; (2) Energy
mining from black holes by cosmic strings; (3) Critical phenomena in
black-hole--black string systems; (4) Information mining from black hole
interior though extra dimensions in brane holes.
Holographic description
of Kerr-Bolt-(A)dS Spacetimes
Masoud Ghezelbash
We show that there exists a holographic 2D CFT
description of a Kerr-Bolt-AdS-dS spacetime. We first consider the wave
equation of a massless scalar field propagating in extremal Kerr-Bolt-AdS-dS
spacetimes and find in the "near region", the wave equation in
extremal limit could be written in terms
of the $SL(2,R)$ quadratic Casimir.
This suggests that there exist dual CFT descriptions
of these black
holes. In the probe limit, we compute the
scattering amplitudes of the scalar
off the extremal black holes and find perfect agreement
with the CFT
prediction. Furthermore we study the holographic description of the generic
four dimensional
non-extremal Kerr-Bolt-AdS-dS black holes. We find that if
focusing on
the near-horizon region, for the massless scalar scattering in the
low-frequency limit, the radial equation could still be rewritten as the
$SL(2,R)$ quadratic Casimir, suggesting the existence of dual 2D description.
We read the temperatures of the dual CFT from the conformal coordinates and
obtain the central charges by studying the near-horizon geometry of
near-extremal black holes. We recover the macroscopic entropy from the
microscopic counting. We also show that for the superradiant scattering,
the retarded Green's functions
and the corresponding absorption cross sections
are in perfect match with CFT prediction.
Extremal black holes and condensed matter
Sean Hartnoll
The holographic correspondence connects low
temperature phases of exotic matter to the physics of near extremal
black holes in asymptotically anti-de Sitter spacetime.
I will discuss various superradiant instabilities of
such black holes and describe what this may teach us about quantum critical
condensed matter systems.
How often does the Unruh-DeWitt detector click
beyond four dimensions?
Lee Hodgkinson
We analyse the response of an
arbitrarily-accelerated Unruh-DeWitt detector coupled to a massless scalar
field in Minkowski spacetimes
of dimensions up to six, working within first-order perturbation theory and
assuming a smooth switch-on and switch-off. We express the total transition
probability as a manifestly finite and regulator-free integral formula. In the
sharp switching limit, the transition probability diverges in dimensions
greater than three but the instantaneous transition rate remains finite up to
dimension five. In dimension six, the instantaneous transition rate diverges in
the sharp switching limit for generic trajectories but remains finite for
trajectories in which the scalar proper acceleration is constant, including all
stationary trajectories. Implications for investigating the detector response
in curved spacetimes via Global Embedding Spacetime (GEMS) methods are discussed.
Black Holes with only One Killing Vector
Gary Horowitz
I will describe black holes with only one Killing
field. The solutions are five dimensional AdS black holes with scalar hair. The
black holes are neither stationary nor axisymmetric, but are invariant under a
single Killing field which is tangent to the null generators of the horizon.
Some of these solutions can be viewed as putting black holes into rotating
boson stars. Others are related to the endpoint of a superradiant instability.
For given mass and angular momentum (within a certain range) several black hole
solutions exist.
The Wilson loop in AdS/CFT and
Confinement
Viqar Husain
One of the "dictionary" entries in the
AdS/CFT correspondence is the calculation of the Wilson loop observable in
Yang-Mills theory from the gravity side. An interesting aspect of this is the
possible association of black hole and other spacetimes with phases of
Yang-Mills theory. I will describe some metrics which exhibit a Coulomb to
confinement transition in the Yang-Mills theory.
Effective quantum gravitational collapse
Andreas Kreienbuehl
We present a class of Hamiltonian deformations of
the massless Einstein-Klein-Gordon system in spherical symmetry for which the
Dirac constraint algebra closes. The system may be regarded as providing effective
equations for quantum gravitational collapse. We analyze these equations
numerically and find interesting deviations from Choptuik's
classical findings.
Near-horizon geometries in supergravities
with hidden symmetry
Hari Kunduri
Associated to every stationary extremal black hole is a unique near-horizon geometry. These spacetimes are more tractable to analyze and crucially, retain properties of the black hole which are intrinsic to the event horizon. We consider the classification of near-horizon geometries in a general two-derivative theory of gravity coupled to abelian gauge fields and uncharged scalars in four and five dimensions, with one and two commuting rotational symmetries respectively. Assuming that the theory of gravity may be cast as a 3d non-linear sigma model, we show that the functional form of any such near-horizon geometry may be determined. We apply this to five dimensional minimal supergravity and the near-horizon geometries of the yet to be found extremal black rings.
Quantum Corrected Black Hole
Dynamics
Gabor Kunstatter
More on McVittie's Legacy
Kayll Lake
Recently Kaloper, Kleban and Martin reexamined the
McVittie solution and argued, contrary to a very widely held belief, that the solution
contains a black hole in an expanding universe. Here we corroborate their main
conclusion and go on to examine, in some detail, a specific solution that
asymptotes to de Sitter space and contains a Schwarzschild - de Sitter black
hole. We show that the null and weak energy conditions are satisfied and that
the dominant energy condition is satisfied almost everywhere. The solution is
understood here by way of a systematic construction of a conformal diagram
based on a detailed numerical integration of the null geodesic equations..
Black holes and membranes, from jets to naked
singularities
Luis Lehner
Analogies between a black holes and membranes have
long been exploited to understand certain properties of black holes. This talk
will review two dynamical scenarios: Jets induced by black holes and the final
fate of unstable black strings where the analogy sheds light into the dynamics
and hints of further interesting behavior.
Graviationally Collapsing K-essence Matter
Danielle Leonard
In
recent years, a number of different models seeking to explain accelerated
cosmological expansion have emerged. One such model is k-essence, which invokes
a massive scalar field with a non-linear kinetic energy term. The dynamical behaviour of this field
is purported to cause accelerated expansion. K-essence has faced criticism, due in part to the fact that
the theory allows the speed of perturbations in k-essence - `sound speed' - to
exceed the speed of light. I shall
describe numerical simulations of the gravitational collapse of k-essence
matter which were undertaken to determine whether such matter behaves in a
physically reasonable manner. The
simulations were carried out in Painlev\'{e}-Gullstrand coordinates. The results of these simulations will
be presented. I will show that the
chosen model of k-essence exhibits atypical behaviour under gravitational
collapse with respect to the formation of apparent horizons and sonic horizons.
Ricci solitons and a static Anti de Sitter space-time with
Schwarzschild boundary metric
James Lucetti
We define Ricci DeTurck solitons, including a
non-positive cosmological term, on manifolds with boundaries or asymptotic
regions. In particular we consider asymptotically hyperbolic manifolds and
static manifolds whose Lorentzian continuations contain Killing horizons, and
show that in all these cases any soliton must in fact be an Einstein metric. We
also discuss Ricci DeTurck flow as a means to find such solutions, and in
particular show it is well defined on static manifolds with extremal horizons.
We give an example of such a flow in the class of five dimensional, static,
axisymmetric metrics, which contain an extremal Poincare horizon and are
asymptotically Anti de Sitter with a Schwarzschild boundary metric, and present
strong numerical evidence that it converges to an Einstein metric in the same
class. We comment on the AdS/CFT interpretation of this space-time.
Quantum Black Hole
Instabilities
Robert Mann
In recent years several proposals have emerged that
purport to describe how the interior of a black hole will be modified due to
quantum effects. These approaches typically involve removal of the classical
curvature singularity at the core via an effective quantum pressure. I show first how the cosmological
vacuum is unstable to pair production of
such quantum black holes and of a new class of solitons. I then show that such quantum black
holes have generically unstable interiors, developing singularities that such interior quantum effects
are unable to deter.
Rigid Quasilocal
Frames and a Resolution to Ehrenfest's Paradox
Paul McGrath
We introduce the concept of a rigid quasilocal frame (RQF), which opens up the possibility of
rigid motion in both special and general relativity with the full six time-dependent
degrees of freedom we have in Newtonian space-time. Additionally, as a proof of
principle we present a quasilocal resolution to Ehrenfest's paradox, in which a rigid body at rest can
never be brought into uniform rotation, afforded by the RQF formalism.
Periastron advance in black hole binaries
Abdul Mroue
By evolving simulations of eccentric binary black
holes with unequal mass ratios, we accurately estimate the periastron
advance from the orbital frequency. We compare these numerical results to the
analytical estimates of the periastron advance
computed from the post-Newtonian approximations, the effective-one-body
formalism and the gravitational self-force prediction.
Black Holes in the Vanishing
Dimensions Framework
Jonas Mureika
There is increasing evidence to suggest
the universe was lower-dimensional at earlier epochs, becoming two-dimensional
in the post-big bang quantum gravity regime. I discuss the associated
implications for primordial black hole physics, including evolution and decay
modes in the pre-(3+1)-D eras. In
particular, consideration is given toward present-day abundances and their
consequential cosmological signatures in this novel scenario.
Holographic Entanglement Entropy
Robert Myers
Black Holes in Randrum-Sundrum II
Don Page
We report preliminary evidence for
large static spherically symmetric black hole vacuum solutions in the
Randall-Sundrum II extra-dimensional gravitational model in which we live on a brane
(plus time) in a (4+1)-dimensional bulk universe with a negative cosmological
constant. The vacuum Einstein equations are satisfied in the bulk, with
the Israel junction conditions satisfied on the brane with its stress-energy
tensor proportional to the intrinsic metric on the brane. This brane
metric is a small deviation away from the Schwarzschild metric, with the
relations between the mass, area, Hawking temperature, and entropy having
fractional corrections of the order of the inverse of the product of the square
of the mass and the bulk cosmological constant, with coefficients for which we
have on May 6 first obtained highly tentative numbers.
Exotic Hairy Black Holes
Chris Pagnutti
n this talk we will discuss a model
of black holes in asymptotically Anti de Sitter spacetime coupled to scalar
fields. These black holes display
an exotic type of second order phase transition with the symmetry breaking
occurring at high temperatures. We
calculate the critical exponents describing the phase transition, which are of
the mean-field type.
Deformations of Lifshitz Holography
in Higher Dimensions
Miok Park
(n+1)-dimensional Lifshitz spacetime
is deformed by logarithmic expansions in the way to admit a marginally relevant
mode in which z is restricted by n=z+1. According to the holographic principle, the deformed spacetime is assumed to be dual for quantum critical
theories, and then thermodynamics of generic black holes in the bulk describe
the field theory with a dynamically generated momentum scale L. This is a basically UV-expanded theory considered in higher dimensions
of the Lifshitz holography from the previous works.
By finding the proper counterterms, the renormalized
action is obtained and by performing the numerical works, the free energy and
energy density is expressed in terms of $T L2$.
Aspects of Lifshitz Holography
Amanda Peet
The AdS/CFT
Correspondence has rightly been a central focus of the string theory community since
it was invented, both for theorists primarily interested in gravity and for
those focused elsewhere. Holography for field theories with
non-relativistic symmetry have attracted a good deal of attention
lately, including Lifshitz field theories describing
quantum phase transitions in some condensed matter systems. In the context of
an Einstein-Maxwell-dilaton theory, we construct
gravitational backgrounds which are candidate holographic duals to Lifshitz theories in various dimensions. We explore the thermodynamics
of these gravitational backgrounds analytically and numerically, showing that
the holographic gravity-based equation of state matches with Lifshitz QFT expectations.
Binary black hole simulations for gravitational
wave science
Harald Pfeiffer
Binary black holes are one of the prime science
targets for gravitational wave detectors like LIGO. I will summarize recent
work by the Caltech-Cornell-CITA collaboration to simulate these sources, and
to apply the simulation results to gravitational wave data-analysis.
Critical Analysis of Dynamical Surface Gravity
in Spherically Symmetric Black Hole Formation
Mathias Pielahn
We present a critical analysis of dynamical surface
gravity in a general spherically symmetric setting using Painleve-Gullstrand
coordinates. We do both an analytic and numerical study of several definitions
that have been proposed in the past as well as a new definition based on PG
co-ordinates. The numerical analysis is done using a specific dynamical model:
spherically symmetric scalar field collapse with a modifed
short distance gravitational potential designed to resolve the classical
singularity. The modification does not significantly afiect
the behaviour of the solution near the outer horizon but permits the evolution
to proceed longer than would otherwise be possible. Although all proposed
definitions of surface gravity asymptotically converge to the standard Killing
vector definition for Schwarzschild black holes, there are somewhat surprising difierences in the rate of convergence. We also discuss
some possible restrictions that one might impose on viable definitions of
dynamical surface gravity, including those that arise in the context of extremal horizons. These restrictions allow us in principle
to rule out several of the definitions considered.
Electromagnetic self-force as a cosmic censor
Eric Poisson
Hubeny identified a scenario in which a charged particle falling toward a
near-extreme Reissner-Nordstrom black hole can penetrate
the black hole and drive it beyond the extremal
limit, thereby giving rise to an apparent violation of cosmic censorship. A
version of this scenario, relevant to a Kerr black hole and involving a
particle with orbital and/or spin angular momentum, was recently examined
byJacobson and Sotiriou (following up on earlier work
by Hod); here also the black hole is driven beyond
the extremal limit. The Hubeny
analysis was inconclusive, however, because in her scenario the particle
crosses the horizon with a near-vanishing acceleration; the test-body
acceleration is of the same order of magnitude as the acceleration produced by
the particle's own electromagnetic self-force, which
was neglected in the analysis. In this talk we report on our computation of the
electromagnetic self-force acting on a charged particle falling radially toward
a Reissner-Nordstrom black hole, and we reveal
whether the self-force acts as a cosmic censor by preventing the particle from
reaching the event horizon.
Gauss-Bonnet Black Holes and Heavy Fermion Metals
Razieh Pourhasan
Using classical gravity we propose a holographic
dual to a CM model proposed by Castro Neto et al. describing the low
temperature behaviour of some strange metals.
Static isolated horizons: SU(2)
invariant phase space, quantization, and black hole entropy
Daniele Pranzetti
We study the classical field theoretical
formulation of static generic isolated horizons in a manifestly SU(2) invariant formulation. After the definition of an
effective theory describing the boundary geometry, a quantization of the
horizon degrees of freedom is proposed. By defining a statistical mechanical
ensemble where only the area of the horizon is fixed macroscopicallystates with
fluctuations away from spherical symmetry are allowedwe show that it is
possible to obtain agreement with the Hawking's area law without fixing the Immirzi parameter to any particular value: consistency with
the area law only imposes a relationship between the Immirzi
parameter and the level of the Chern-Simons theory
involved in the effective description of the horizon degrees of freedom.
Possible observation sequences of Brans-Dicke wormholes
Kristina Rannu
А flux from an accretion on the wormhole in the
Brans-Dicke model was considered. The key idea is the
search of possibilities to distinguish a Brans-Dicke
wormhole from other objects basing on observational astronomical data on disk
accretion.
Holography for non-relativistic theories
Simon Ross
I will discuss the construction of a holographic dictionary
for theories with non-relativistic conformal symmetry, relating the field
theory to the dual spacetime. I will focus on the
case of Lifshitz spacetimes,
giving a definition of asymptotically locally Lifshitz
spacetimes and discussing the calculation of field
theory observables.
Singularities from Exotic Differentiable Structures
Kristin Schleich
5 dimensional spacetimes can have Cauchy surfaces
with exotic differentiable structures. This feature, not present in lower dimensional
spacetimes, has important consequences for their global structure. In
particular, asymptotically flat spacetimes with a Cauchy surface with
nontrivial Seiberg-Witten invariants, hence with an exotic differentiable
structure, that satisfy the dominant energy condition must contain a trapped
surface. Therefore, such spacetimes are singular.
Tomimatsu-Sato geometries and the Kerr-CFT
Sanjeev Seahra
The delta=2 Tomimatsu-Sato
geometries are solutions of the vacuum Einstein field equations that involve a
naked singularity, closed timelike curves, and two
disjoint Killing horizons. I describe how, despite these pathologies, the near
horizon geometry appears to admit a Kerr-CFT like
description with a central charge and temperature consistent with the Cardy formula. Implications for the wider Kerr-CFT
programme are discussed.
Spin Optics in a Stationary Space-time
Andrey Shoom
We study propagation of circularly polarized beams
of light in a stationary space-time. For this purpose we consider and study
spin-dependent corrections and post-geometric optics approximation for an
electromagnetic wave propagating in a stationary space-time.
Theory and phenomenology of higher-dimensional
black holes
Dejan Stojkovic
One of the few robust predictions of quantum
gravity is the formation of black holes in particle collisions at energies
higher than Planck energies. If recently proposed theories with large extra
dimensions and TeV scale gravity are true, then there
is the possibility of testing quantum gravity in accelerators (LHC) or
experiments with cosmic rays (AUGER, Ice Cube). But theory and phenomenology of
multi-dimensional black holes is very complicated, which makes identification
of signals quite uncertain. For this purpose, in collaboration with Oxford
University ATLAS group, we have created Black Max, a very comprehensive event
generator which contains almost everything we know about the multi-dimensional
black holes to date. The generator is based on a
phenomenological valid models, where serious problems that often
accompany models with strong gravity are not present. Black Max is interfaced
with the ATLAS Monte Carlo programs Herwig and Pythia and is now official software at CERN.
Locally Stable
Kaluza-Klein Bubbles
Sean Stotyn
I present a new 2-parameter family of static
topological solitons in 5D minimal supergravity which are endowed with magnetic
charge and mass. The solitons are asymptotically R4x S1,
where the radius of the S1 has a lower bound R>R_{min}.
Setting up initial data on a Cauchy slice at a moment of time symmetry, I
demonstrate that these solitons correspond to a perturbatively stable
``small" static bubble as well as an unstable ``large" static bubble.
The energetics of the magnetic black string are then discussed and it is
shown that the locally stable bubble is the end point of a phase transition for
an appropriate range of black string parameters.
Higher Dimensional Choptuik
Scaling in Painleve Gullstrand Coordinates
Timothy Taves
Whether or not a collapsing scalar field forms a
black hole depends on parameters in the initial configuration of the
field. Any one of these
parameters, say A, may be varied to find the smallest (or possibly the largest
depending on the parameter) value of this parameter which will form a black
hole. This is known as the critical value, A*. The relationship between |A*-A|
and the mass of the black hole is known as Choptuik
scaling and has been investigated in various coordinate systems, including Painleve-Gullstrand (PG). This talk investigates Choptuik scaling in higher dimensional (>4) spacetimes in PG coordinates and compares the results with
similar work done in null coordinates.
Experimental Black Hole Thermal Emission
W. Unruh
A group at UBC has recently shown that an analog
white hole horizon emits thermal quantum radiation with a temperature given by
the properties of that horizon. This talk will describe that experiment and the
theory behind it.
A
group Effective source Approach to Self-force Calculations
Ian Vega
Numerical evaluation of the self-force on a point
particle is made difficult by the
use of delta functions as sources.
In this talk, I shall discuss an alternative method that avoids delta
functions altogether, using instead a finite and extended ``effective
source'' for a point particle. I shall also highlight recent progress in an ongoing effort to apply this
method to the oustanding case of
particles moving along generic geodesics of a Kerr background.
Penetration of dynamical horizons
Jeffrey Winicour
I will discuss simulations of binary black holes mergers in which, after
the common outer horizon has formed, the marginally outer trapped surfaces
(MOTS) corresponding to the individual black holes continue to approach and
eventually penetrate each other. This has very interesting consequences
according to recent results in the theory of dynamical horizons. In particular,
the penetration cannot continue to completion unless the two MOTS coalesce into a single MOTS. This would be an extremely dramatic
event in the case of a large and small black hole. I will present results of
simulations in which
the small MOTS has halfway penetrated the large one.
Black holes with su(N)
gauge fields and superconducting horizons
Elizabeth Winstanley
We study black holes in su(N) Einstein-Yang-Mills theory in asymptotically anti-de Sitter space with planar horizons. Solutions with a non-trivial gauge field exist only below a critical temperature. We find that non-abelian su(3) solutions are thermodynamically favoured over both non-abelian su(2) solutions and planar Reissner-Nordstrom black holes.
3D Gravity and Black Holes
Don Witt
Jang’s equation and MOTS/MITS are discussed in the context of 3D gravity. The results on existence of solutions are first established and then applied to black holes in 3d gravity. Finally, implications for black holes and gravity in other dimensions are considered.
Black hole initial data in Gauss-Bonnet gravity
Hirotaka Yoshino
Gauss-Bonnet (GB) gravity modifies general relativity by including
higher-curvature terms, and such correction arises in the low-energy limit of
the heterotic string theory. Developing the GB
version of numerical relativity is an interesting issue in the context of TeV scale gravity and the AdS/CFT
correspondence. Although the extension of the ADM formalism has been done by
Torii and Shinkai, no simulation has been performed
up to now. The first step is to prepare the "initial data" by solving
constraint equations, and recently I succeeded in numerical generation of the
initial data of black hole systems. In this talk, I explain the method and the
obtained results, and assess whether the Penrose inequality is satisfied in GB
gravity.
Some recent
conclusions regarding the tunneling of Hawking radiation
Alexandre Yale
Half a decade ago, a novel technique was proposed to calculate Hawking
radiation as the tunneling of quantum fields through an event horizon.
This research area quickly exploded in popularity, with hundreds of papers
algorithmically (re)calculating the Hawking temperature for every known
spacetime and for various types of particles. The field's popularity grew
once again two years ago as these calculations were extended to higher orders in
hbar: dozens of black holes were thus revisited, in just as many new
papers. In this talk, we will review recent results which show how to
concisely perform these calculations in full generality: for an arbitrary free
field emitted from a generic black hole, to every order.