Black Holes VIII

Theory and Mathematical Aspects

May 10-14 2011

Niagara Falls, Ontario, Canada









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.