Cosmology & Gravitation

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

Seminar Series Events/Videos

May 2 2017 - 11:00am
Room #: 400
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May 16 2017 - 11:00am
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May 30 2017 - 11:00am
Room #: 400
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Tuesday Apr 11, 2017
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A number of ground based CMB surveys that will survey large fractions of the sky to high sensitivity are currently in the planning stages.  I will give an overview of what can be learned from these surveys about the Universe since recombination, focussing on gravitational lensing science.  I will also discuss some new CMB observables that would be accessible with even more futuristic surveys.

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Tuesday Mar 28, 2017

Cosmology has seen great progress thanks to precision measurements and is bound to greatly benefit from upcoming Large Scale Structure and Cosmic Microwave Background data. I will point out a number of interesting directions. In particular, I discuss how the microphysics of inflation may be tested in galaxy surveys through “fossil” signatures originating from squeezed primordial correlations.

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Tuesday Mar 21, 2017
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I will describe the Dark Energy Spectroscopic Instrument (DESI), an instrument currently being built to carry out a large galaxy redshift survey.  DESI is the next step beyond the SDSS and BOSS surveys, mapping over 30 million galaxies.  I will focus in particular on the amazing engineering challenges of the DESI instrument itself, which includes a 5,000-robot army and 250 kilometers of fiber optics.  I will conclude by briefly describing the work I am personally involved in: a large imaging survey that will measure the galaxies from which DESI will select targets for

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Thursday Mar 16, 2017
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Modified gravitation known as Scalar-Tensor- Vector-Gravity (STVG) and MOG and its consequences for dark matter and dark energy in astrophysics and cosmology and black holes is reviewed. A variable speed of light (VSL) cosmology is compared to inflation.

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Thursday Mar 09, 2017
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Current constraints on spatial curvature demonstrate it to be dynamically negligible at late times. However, neglecting it as a cosmological parameter would be premature, as it offers a valuable test of eternal inflation models and probes novel large-scale structure phenomena.

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Tuesday Mar 07, 2017
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Pulsars are some of physics and astrophysics’ most exotic objects, and they have already earned two Nobel Prizes. We currently know of about 2500 of them in our Galaxy, but a small subset, the millisecond pulsars (MSPs), are truly remarkable. These systems are notoriously hard to detect, yet their numbers have more than doubled in the past 5 years via surveys using the world’s most sensitive

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Thursday Feb 23, 2017
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Despite varying speed of light theories (VSL) should be considered as another type of alternative gravity theories with an extra scalar degree of freedom, their formulation causes the problems in view of breaking the light principle and relativity principle. Besides, there are a couple of physical contexts in which c plays the crucial role and it is uncertain that it has the same meaning everywhere. During my talk I will discuss some basic theoretical formulations of varying c theories and discuss their benefits as well as problems.

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Tuesday Feb 21, 2017
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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.

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Tuesday Jan 31, 2017
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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.

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Thursday Jan 19, 2017
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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.

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