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
The ground-based gravitational-wave telescopes LIGO and Virgo approach the era of first detections. Gravitational-wave observations will provide a unique probe for exploring strong-field general relativity and compact-binary astrophysics. In this talk, I describe recent predictions regarding the distributions of black-hole and neutron-star binary mergers, and progress on solving the inverse problem of turning gravitational-wave observations into astrophysical information.
Gravitational radiation promises to teach us many new
things about the universe and the world around us, but all attempts to observe
gravitational waves have so far been unsuccessful. I will discuss some of the challenges we need
to overcome in our quest to detect this elusive form of energy, and how
tackling these challenges is opening new windows on fundamental physics. I will show, specifically, how novel data
analysis strategies have been used to combat detector noise in searches for
In this talk, I will discuss about the notion of quantum renormalization group, and explain how (D+1)-dimensional gravitational theories naturally emerge as dual descriptions for D-dimensional quantum field theories. It will be argued that the dynamical gravitational field in the bulk encodes the entanglement between low energy modes and high energy modes of the corresponding quantum field theory.
Removing the mystery from quantum mechanics, the Bohmian perspective – a way of describing the motion of quantum particles, and applying this to spacetime singularities (where gravity becomes infinite) like those inside a black hole.
The bimodality of gamma-ray burst (GRB) durations points
to distinct progenitor classes for the long- and short-duration GRBs. While the
progenitors of long-duration GRBs are now known to be massive stars, the
progenitors of short-duration GRBs remain unidentified. In this talk I will
discuss the discovery of short GRB afterglow and their host galaxies, detailed
studies of their environments from parsec to galactic scales, and studies of
their energetics and beaming. Taken together, these observations point to the
Gamma Rays at 130 GeV and How They Might Come from Dark
I'll discuss the exciting (but somewhat controversial)
new discovery of a sharp gamma ray feature at 130 GeV from near the galactic
center and review some other evidence that might link it to annihilation of
dark matter. I will then explain the challenges in understanding how dark
matter might produce this signal and explain a model or two that overcome these