Cosmology & Gravitation

This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Tuesday Feb 21, 2017
Speaker(s): 

We are currently entering the era of precision CMB polarization observations. The most exciting scientific targets are a possible detection of primordial gravitational waves and a measurement of the sum of the neutrino masses. The former depends on the extensive landscape of early Universe models, while the latter has been forecasted to present a clear, and reachable, scientific target. First, if large angular B modes are detected, we should firmly establish that these are sourced by primordial gravitational waves.

Collection/Series: 
Scientific Areas: 

 

Tuesday Jan 31, 2017
Speaker(s): 

Astrophysical black hole candidates, although long thought to have a horizon, could be horizonless ultra-compact objects. This intriguing possibility is motivated by the black hole information paradox and a plausible fundamental connection with quantum gravity. In this talk I will consider the asymptotically free quadratic gravity as the UV completion of general relativity. Using a classical theory that captures its main features, we find that sufficiently dense matter produces a novel horizonless solution, the 2-2-hole.

Collection/Series: 
Scientific Areas: 

 

Thursday Jan 19, 2017
Speaker(s): 

I will present a recent analysis of the Planck 2015 data that is complete in the reionization observables from large angle CMB polarization measurements using principal components (PC). By allowing for an arbitrary ionization history, this technique tests the robustness of total optical depth inferences from the usual instantaneous reionization assumption. A reliable measurement of the total optical depth is important for the interpretation of many other cosmological parameters such as the dark energy and neutrino mass.

Collection/Series: 
Scientific Areas: 

 

Tuesday Jan 17, 2017
Speaker(s): 

CHIME is a new interferometric telescope at radio frequencies 400-800 MHz.  The mapping speed (or total statistical power) of CHIME is among the largest of any radio telescope in the world, and the technology powering CHIME could be used to build telescopes which are orders of magnitude more powerful.  This breakthrough sensitivity has the power to revolutionize radio astronomy, but meeting the computational challenges will require breakthroughs on the algorithmic side.  I'll give a status update on CHIME, with an emphasis on new algorithms being developed to search for fast radio bursts a

Collection/Series: 
Scientific Areas: 

 

Wednesday Jan 11, 2017
Speaker(s): 

Measurements of the cosmic microwave background (CMB) have proven to be a powerful probe of the physics of our universe. CMB observations are helping to address fundamental questions, such as the nature of dark energy and dark matter, and are being used to probe the physics of inflation at energies a trillion times higher than the Large Hadron Collider. Recent measurements led to several exciting first detections, including CMB lensing, massive galaxy clusters, the large-scale velocity field, and the “B-mode” component of the polarization field.

Collection/Series: 
Scientific Areas: 

 

Tuesday Dec 13, 2016
Speaker(s): 

Inflation is proposed as a means of explaining why the Universe is currently so homogeneous on larger scales, solving both the horizon and flatness problems in early universe cosmology. However, if inflation itself requires homogeneous conditions to get started, then inflation is not a solution to the horizon problem. Most work up until now has focussed on a dynamical systems approach to classifying the stability of inflationary models, but recently Numerical Relativity (NR) has been used to simulate the actual evolution of the inflaton field, leading to new insights.

Collection/Series: 
Scientific Areas: 

 

Tuesday Nov 29, 2016
Speaker(s): 

I will discuss the potential for the LISA space-based interferometer to detect the stochastic Gravitational Wave (GW) background produced from different mechanisms during inflation. In particular, I will present the GW contributions from particle production during inflation, inflationary spectator fields with varying speed of sound, effective field theories of inflation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes.

Collection/Series: 
Scientific Areas: 

 

Tuesday Nov 08, 2016
Speaker(s): 

I discuss the phenomenology of models of inflation with periodic particle production. Particle production occurs as the mass of heavy particles goes through non-adiabatic modulations as the inflaton field rolls. I show that this process can lead to significant emission of scalar and gravitational waves during inflation, with distinct observational signatures.

Collection/Series: 
Scientific Areas: 

 

Tuesday Nov 01, 2016

We argue that moduli stabilization severely constrains the evolution following transitions between weakly coupled de Sitter vacua and can induce a strong selection bias towards inflationary cosmologies. We carefully discuss gravitational vacuum decays and resolve a naive sign ambiguity in the exponential of the decay rate. Equipped with this clear understanding of vacuum decay we then turn towards constraints on the cosmological evolution after transitions in weakly coupled flux compactifications.

Collection/Series: 
Scientific Areas: 

 

Tuesday Oct 25, 2016
Speaker(s): 

If heavy fields are present during inflation, they can leave an imprint in late-time cosmological observables. The main signature of these fields is a small amount of distinctly shaped non-Gaussianity, which if detected, would provide a wealth of information about the particle spectrum of the inflationary Universe. Here we investigate to what extent these signatures can be detected or constrained using futuristic 21-cm surveys. This part of my talk is based on 1610.06559.

Collection/Series: 
Scientific Areas: 

Pages