Colloquium

Can we learn about New Physics with astronomical and astro-particle data? Understanding how this is possible is key to unraveling one of the most pressing mysteries at the interface of cosmology and particle physics: the fundamental, particle nature of the dark matter.
I will discuss some of the recent puzzling findings in astro-particle and astronomical observations that might be related to signals from dark matter. I will first review the status of explanations to the cosmic-ray positron excess, emphasizing how we might be able to discriminate between astrophysical sources and dark matter. 
I will then discuss the evidence for an X-ray line at 3.5 keV, and present new results on systematic effects and on the role of previously underestimated astrophysical lines.
Finally, I will discuss a reported excess of gamma rays from the central regions of the Galaxy.  I will address the question of whether we are possibly observing a signal from dark matter annihilation, how to test this hypothesis, and which astrophysical mechanisms constitute the relevant background.

 

The spatially-indirect exciton condensates (SIXC) is an interesting ordered electronic state in which coherence is spontaneously established between particles localized in separate two-dimensional layers. I will discuss some of the properties SIXCs, commenting on their counterflow superfluidity, their collective excitations, and on similarities and differences relative to superconductors, easy-plane ferromagnets and anti-ferromagnets, and the standard model of particle physics.  Finally I will discuss the prospects of achieving SIXC states at elevated temperatures in multi-layer 2D material systems.   

In the last few years there has been significant interest in the possible applications of gauge-gravity duality to condensed matter systems. In this talk I will discuss recent applications of these holographic techniques to strongly correlated systems out of equilibrium. I will argue that insights from general relativity, hydrodynamics and quantum field theory may be combined to yield quantitative predictions for quantum transport.

Over Twenty-five years into the internet era, over twenty years into the WorldWideWeb era, fifteen years into the Google era, and a few years past the Facebook/Twitter era, we've yet to converge on a new long-term methodology for scholarly research communication. I will provide a sociological overview of our current metastable state, and then a technical discussion of the practical implications of literature and usage data considered as computable objects, using arXiv as exemplar. From the physics standpoint, there is a surprising amount of statistical mechanics in text-mining and machine learning.

It has become a platitute to say that black holes are fascinating objects—but they really are, in part because they challenge our understanding of the fundamental reversibility of physical processes.

In the first part of the talk, I will review some of the classical ways black holes behave as dissipative systems, such as the "hair loss” phenomenon and the monotonic growth of horizon area. In the second part, I will explain how quantum mechanics (more precisely, the coupling of black holes to the quantum vacuum) affects the classical picture at late times, notably through particle creation and evaporation. I will argue that techniques from two-dimensional field theory can help bring clarity to the associated “information loss”

problem, and perhaps also point to new, unexpected predictions. My approach will be as model-independent as possible; that is, rather than investigating a particular scenario for black hole evaporation, I will aim to derive generic consequences from basic assumptions regarding the reversibility of black hole evaporation.

Modern physics rests on two basic frameworks, quantum theory and general relativity. Quantum gravity aims to unify these two frameworks into one consistent theory. One can expect that such a formulation delivers in particular a novel understanding of space and time as quantum objects.

I will give an introduction to some basic concepts in quantum gravity research and present possible models of quantum space time.

There is an analogy between the propagation of fields in the vicinity of astrophysical black holes and the that of small excitations in fluids and superfluids. This analogy allows one to test, challenge and verify, in tabletop experiments, the elusive processes of black hole mass and angular momentum loss.

I will first present a brief overview on analogue black hole experiments, and then discuss in more detail some of my earlier and more recent experimental and theoretical results on the subject.

The discovery of the Higgs boson at the Large Hadron Collider marks the culmination of a decades-long hunt for the last ingredient of the Standard Model. At the same time, this discovery has started a new era in the search for more fundamental physics. In this talk, I will discuss what we have learned from the Higgs discovery about the mechanism of electroweak symmetry breaking and the implications for the existence of additional Higgs bosons. I will then highlight the future prospects of the Higgs boson in shedding light on New Physics and in particular on the nature of Dark Matter.

Galileons are higher-derivative effective field theories with curious properties which have attracted much recent interest among cosmologists.  I will review their origins, their properties, their generalizations, and some recent developments.

Thanks to the spectacular observational advances since the 1990s, a `standard model' of the early universe has now emerged. However, since it is based on quantum field theory in curved space-times, it is not applicable in the Planck era. Using techniques from loop quantum gravity, the theory can be extended over the 12 orders of magnitude in density and curvature from the onset of inflation all the way back to the Planck regime, providing us with a possible completion of the standard model.

Contrary to a wide-spread belief, the resulting pre-inflationary dynamics can have observational consequences for the longest wave length modes of cosmological perturbations. Thus, there is now an an interesting interplay between fundamental theory and observations. The talk will provide a broad overview of these results addressed to non-experts.

Web-links:

Viewpoint: A glance at the earliest universe; APS Physics Spotlighting Exceptional Research: http://physics.aps.org/articles/v5/142

U tube video

http://www.youtube.com/watch?v=IFcQuEw0oY8&feature=c4-overview&list=UUtOgK

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In holographic duality a gravitational spacetime emerges as an equivalent description of a lower-dimensional conformal field theory (CFT) living on the asymptotic boundary. Traditionally, the dimension not present in the CFT is interpreted in terms of its Renormalisation Group flow. In this talk I exploit the relation between boundary entanglement entropies and bulk minimal surfaces to define a quantitative framework for the holographic Renormalisation Group, in which quantum information theory plays a fundamental role. I will provide operational, quantitative, information-theoretic characterizations of several geometric concepts in asymptotically AdS3 spacetimes, including the radial direction and lengths of bulk curves.

Perhaps the biggest conceptual benefit of the information-theoretic framework for holographic Renormalisation Group is a quantitative correspondence between holography and the Multi-Scale Entanglement Renormalisation Ansatz (MERA). I also discuss prospects for understanding the near-horizon structure of black holes.

After 50 years of dreaming about it, space-based microlensing observations are now underway.  A 2014 100-hr Spitzer Pilot Program generated "microlens parallaxes" for dozens of lenses, opening the prospect of measuring the Galactic distribution of planets.  This program will be expanded 8-fold in 2015.  Analogous observations by Kepler will measure the mass function of free-floating planets.

WFIRST microlensing observations will, as advertised, "complete the planetary census" but they will do an immense amount of astrophysics as well.  I discuss how microlensing's take off builds on rapid, ongoing, ground-based developments.