This series consists of talks in areas where gravity is the main driver behind interesting or peculiar phenomena, from astrophysics to gravity in higher dimensions.
Horava's proposal to use Lifshitz propagators for gravitons above certain energy scales may provide a viable theory of quantum gravity without further need of UV completion. In my talk, I will address the question of whether the complete lack of Lorentz invariance above a certain energy scale is a big problem for any realistic construction. I will argue that it is not, provided that the onset of Lifshitz scaling for gravitons occurs at momentum scale much lower than the Planck mass.
This talk will discuss the formation, structure and interaction of null singularities for
the Einstein equations, as well as what this all means for the singular boundary
of generic space times within black hole regions.
The equation of state of matter at and above nuclear densities remains a major theoretically uncertain prediction of QCD. Observations of the mass-radius relationship of neutron stars constrain, and can directly measure, the dense matter equation of state. I will discuss how measurements of neutron star radii have already constrained the dEOS, and how future work will directly measure the dEOS, providing an important constraint on models of the strong force.
There exist evidences that magnetic field in
the vicinity of astrophysical black holes plays an important role. In
particular it is required for explanation of such phenomenon as jet formation.
Study of such problems in all their complexity requires 3D numerical
simulations of the magnetohydrodynamics in a strong gravitational field. Quite
often when dealing with such a complicated problem it is instructive to
consider first its simplifications, which can be treated either analytically,
The modelling of gravitational wave sources is of timely interest given the exciting prospect of a first detection of gravitational waves by the new generation of detectors. The motion of a small compact object around a massive black hole deviates from a geodesic due to the action of its own field, giving rise to a self-force and the emission of gravitational waves. The self-force program has recently achieved important results using well-established methods.
Hydrodynamics of relativistic plasmas received,
within the last 10 years, a lot of attention. The reason for it, on one hand,
is the quest for theoretical understanding of the quark-gluon plasma created in
heavy ion collisions and, on the other, advances in holographic duality and
black hole physics in anti-de Sitter spacetimes. I will describe recent
progress in answering foundational issues in hydrodynamics of strongly coupled
systems, i.e. questions about its applicability and the character of
will review recent work in two very different topics. First, I will discuss the
quasinormal mode spectrum of nearly extremal Kerr black holes, where a
bifurcation of the frequency spectrum is observed. In addition, collective
oscillations of many modes is possible, resulting in a power-law rather than
exponentially decaying ringdown. Next, I will discuss a recent proposal for how
tidally induced, multimode coupling of normal modes in neutron stars can
destabilize the stars. Such an instability could hamper gravitational wave
Pulsars have enormous magnetic fields whose energy density
dwarfs the rest mass density of their plasma magnetosphere. In this
regime of a plasma, the particles drop out of the description, leaving a set of
equations for the electromagnetic field alone. This non-linear,
deterministic system is known as force-free electrodynamics, and turns out to
have some beautiful and bizarre features. I will give a pedagogical
introduction to these equations and their role in astrophysics and then discuss
I describe recent work with with Stefan Hollands that establishes a new criterion for the dynamical stability of black holes in $D \geq 4$ spacetime dimensions in general relativity with respect to axisymmetric perturbations: Dynamic stability is equivalent to the positivity of the canonical energy, $\mathcal E$, on a subspace of linearized solutions that have vanishing linearized ADM mass, momentum, and angular momentum at infinity and satisfy certain gauge conditions at the horizon. We further show that $\mathcal E$ is related to the second order variations of mass, angular momentum, an