Modified Gravity (MOG), Dark Matter and Black Holes
According to the standard model of cosmology 96% of the matter and energy in the universe is invisible. The dark matter particles comprising the invisible material have so far not been detected. The dark energy responsible for the acceleration of the universe is still a controversial issue. A modified gravity theory is presented that can potentially fit current cosmological and astrophysical data. The black holes and their shadows predicted by MOG can differ from the predictions of Einstein gravity.
Non-singular black holes from new 2D gravity
I outline the construction of a two-dimensional action that is an extension of spherically symmetric Einstein-Lanczos-Lovelock gravity. The action contains arbitrary functions of the areal radius and the norm squared of its gradient, but the field equations are second order and obey the Birkhoff's theorem. In complete analogy with spherically symmetric Einstein-Lanczos-Lovelock gravity, the field equations admit the generalized Misner-Sharp mass as the first integral that determines the form of the vacuum solution. The arbitrary functions in the action allow for vacuum solutions that describe a larger class of interesting non-singular black-hole spacetimes than previously available.
Scanning New Horizons: Entanglement & Holography
I will give a brief review introducing the two topics in the title: quantum entanglement and the holographic description of gravity. Then I will describe some facets of the interesting interplay that has emerged in combining these two ideas.
So...What can Relativity do for you?
We will explore the most applied side of Relativistic Quantum Information, and how understanding gravity and quantum field theory has provided new perspectives and imaginative ideas for quantum technologies. From new metrological schemes to quantum simulation, computing and communication.
Spacetime geometry on three scales: black holes, gravitational waves & cosmology
General Relativity is 40 years older than Robb, so by the time Robb entered the field, the low-hanging fruit had already been picked. Indeed, the three most dramatic predictions of General Relativity — Black Holes, Gravitational Waves, and Cosmological Expansion — were all made in the very early days of GR. Nevertheless, with over 350 publications to his name, Robb has had remarkable success at picking the high-up fruit. This speaks both to the richness of the theory and to Robb's ability to find new ways to probe it.
For this talk, I thought I would go back to those three early predictions and tie them together with the following question: Can we use gravitational waves, produced by black holes, to measure cosmological expansion? That is, can we use ripples of geometry produced by purely geometric objects to measure the large-scale geometry of the universe? I think this might be possible by using pulsar timing arrays to observe gravitational waves from supermassive black hole binaries at cosmological distances, and directly inferring the curvature of the universe from those observations. If this can be done, we would have a new way of measuring cosmological expansion based solely on geometry which could supplement the existing cosmic distance ladder.
Neutron Stars and General Relativity
Neutron stars are tiny and dense, which means that their escape velocity and rotational velocities can be a significant fraction of the speed of light. As a result, general relativity is a key aspect of the description of their structure. Relativity is also important when considering what light emitted by a neutron star is detected in a telescope. In this talk I'll review some of the aspects of general relativity that are important for understanding neutron stars and their observations.
A 125 GeV Higgs Mass in the Conformal Standard Model
The conformal Standard Model provides a natural framework for addressing aspects of the hierarchy problem. Electroweak symmetry-breaking in this framework occurs via loop corrections (the Coleman-Weinberg mechanism). This symmetry-breaking mechanism requires a large Higgs self-coupling to balance the effect of the large top-quark Yukawa coupling. Results for the Higgs mass prediction in the conformal Standard Model are presented, including evidence for asymptotic convergence to a mass of approximately 125 GeV, consistent with the experimentally-determined value.
The range of horizon dynamics
Multiboundary wormholes: more adventures in three dimensions
As I learned in Waterloo, lower-dimensional models provide a very useful laboratory for studying quantum gravity. I will describe one recent manifestation: geometries with multiple asymptotic regions can be easily constructed, and these provide an ideal laboratory for studying the connection of geometry to entanglement.
Symmetry protection beyond band theory
The null-boundary contribution to the varied gravitational action-functional
The variation of the Ricci scalar integrated over a spacetime region receives four kinds of contributions from the lightlike portion of the region's boundary. I will describe these contributions and attempt to characterize them geometrically in relation to the possibility of a gravitational path integral of Schwinger-Kel'dysh type.
Lower Dimensional Black Hole Chemistry
The connection between black hole thermodynamics and chemistry is extended to the lower-dimensional regime by considering the rotating and charged BTZ metric in the (2+1)-D and a (1+1)-D limits of Einstein gravity, with many intriguing results. It is shown that Q≠0 BTZ black holes violate the Reverse Isoperimetric Inequality and are thus super-entropic. The inequality can be maintained, however, with the addition of a new thermodynamic work term associated with the mass renormalization scale. In the (1+1)-D case, the requirement of positive entropy implies a lower bound on the mass of associated black holes. Lastly, promoting an associated constant of integration to a thermodynamic variable allows one to define a "rotation" in one spatial dimension. Some (3+1)-D Mann-related anecdotes will also be interspersed, which will be shown to provide hilarity to the talk.
Relevant paper: arXiv:1509.05481
Cosmological non-Constant Problem
I will discuss why I think the (lack of) gravitational signatures of quantum vacuum fluctuations today, might be our most important clue towards understanding the particle physics beyond standard model.
Robb's dark side chemistry
I will describe Robb as a dark side chemist who likes to keep a tight rein on little black holes by putting them under the pressure of negative dark energy. Poor black holes, their mass being interpreted as chemical enthalpy, have to follow Robb's strong will and undergo various chemical-type phase transitions, demonstrating, for example, the Van der Waals behavior, reentrant phase transitions, or triple points.
Based on ArXiv:1404.2126.