College of Arts and Sciences

We are investigating modifications of general relativity that are operative at the largest observable scales. In this context, we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory in a weakly coupling regime on a Minkowski background. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below. This result opened a new window of opportunity for consistent modified Friedmann cosmologies. In our recent work it is shown that a brane with FRW symmetries necessarily acts as a source of cylindrically symmetric gravitational waves,

Continue reading… The Universe as a Cosmic String – Florian Niedermann

The existence of the Standard Model (SM) Higgs implies that a gravitational wave (GW) background is generated by the decay products of the Higgs, soon after the end of inflation. Theoretically, all Yukawa and SU(2)L gauge couplings of the SM are imprinted as features in the GW spectrum. However, in practice, the signal from the most strongly coupled species dominate, rendering inaccesible the information on the other species. This background could be used for inferring properties of particle physics, including beyond the SM, at energies way above the reach of LHC. To measure this background, however, new high frequency GW detection technology is required.

Continue reading… Imprints of the Standard Model in the Sky? – Daniel G. Figueroa

Continue reading… New Ideas for Dark Energy and Also for Dust Discrimination in B-mode Maps – Marc Kamionkowski

I will describe theoretical motivation for the existence of parity violating (helical) intergalactic magnetic fields and recent and growing observational evidence for such fields.

Continue reading… Intergalactic Magnetic Fields – Tanmay Vachaspati

I will reiew recent and substantial progress in modeling the cosmic web. This progress, which results from merging two different and decades old literature streams, leads to a number of new and interesting insights about how the biased tracers we will observe in the next generation of large scale structure datasets can better constrain cosmological models.

Continue reading… Peaks and Troughs in Large Scale Structure – Ravi K. Sheth

The large scale structure of matter and galaxies contains important information on the evolution of the Universe. Baryon acoustic oscillations (BAO), which is one of the most promising large scale features, can provide an excellent standard ruler that enables us to measure the cosmological distance scales, and therefore dark energy properties. I would like to first discuss the ongoing joint analysis of BOSS galaxy and lya BAO results and, second, future 21cm BAO surveys focused on the effect of foregrounds.

Continue reading… High Precision Cosmology with BAO Surveys: BOSS and Future 21cm BAO Surveys – Hee-Jong Seo

The universe, or at least the 5% of it that we understand, is described rather well by the Standard Model of particle physics. Yet even this non-dark sector of the universe conceals a great mystery: // where has all the anti-matter gone? // In this lecture, I will describe the problem and the best solution that we have for it. One of the crucial ingredients of that solution is the prediction of new sources of time-reversal violation. The most sensitive probe of such time-reversal violation is, oddly enough, to be found in small asymmetries in the shape of the electron’s charge distribution.

Continue reading… The Shape of the Electron, and Why It Matters – Amar Vutha

Galaxy imaging and redshift surveys, designed to measure gravitational lensing and galaxy clustering, remain the most powerful probes of large-scale structure. Such surveys constitute a significant fraction of current and next-generation projects in the cosmology community (e.g. DES, HSC, LSST, eBOSS, DESI, EUCLID, WFIRST). The statistical power of these experiments requires significantly improved understanding of astrophysical and observational effects. In this talk, I will focus on two important astrophysical processes which contribute systematic uncertainty but also contain a potential wealth of information. First, correlations in the intrinsic shapes and orientations of galaxies, termed “intrinsic alignments” (IA), are an important systematic in weak lensing.

Continue reading… Precision Cosmology with Galaxy Surveys: Understanding Intrinsic Alignments and Redshift-space Distortions – Jonathan A. Blazek

In search for a candidate that could explain the current acceleration of the Universe, a lot of attention has been given recently to Galileon theories, or in their generalized form, Horndeski theories. They are interesting as they represent the most general scalar tensor theories that do not lead to equations of motion containing more than two derivatives. This restriction is generally thought to be of great importance, as generically, higher order derivatives lead to ghost instabilities. I will present a new class of scalar tensor theories that are broader than Horndeski and, as such, do bring higher order derivatives. However,

Continue reading… Healthy Theories Beyond Horndeski – Jerome Gleyzes

In this talk I will discuss some recent progress in our understanding of the spin-2 sector, focussing on theories with two or more dynamical such fields. In particular I will highlight the existence of several dualities in such models (generalisations of `Galileon dualities’), their decoupling limit phenomenology as well as the form of their interactions with other matter fields.

Continue reading… Interacting Spin-2 Fields – Johannes Noller