This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.
Stars orbiting in the halo of our galaxy, the Milky Way, are a window into the distribution of dark matter. In particular, tidally disrupted star clusters, which produce thin stellar streams, are optimal tracers of matter. Based on a Fisher-information calculation, we expect that the current data on the known Milky Way streams should constrain the radial profile and the shape of the inner halo to a precision of a few percent. In addition, stellar streams retain a detailed record of the matter field on small scales.
In galaxy redshift surveys, the line-of-sight velocity information is encoded in the observed redshift as a Doppler component that radially distorts the galaxy positions. The linear component of such `Redshift-Space Distortions' (RSD) is directly proportional to the growth rate of structure, f(z), and motivates the interest in RSD as a powerful way to constrain gravity. However, the non-linear evolution of the density and velocity fields requires the use of sophisticated theoretical models to extract reliable cosmological information from quasi-linear scales.
Gravitational lensing has long served as a unique probe of the growth of structure, which is sensitive on large scales to the properties of dark energy and gravity. In particular, lensing is instrumental in forming the statistic E_G, which is constructed to measure the growth rate of structure in a way independent of galaxy clustering bias. Me
One of the most important discoveries of the 20th century has been the finding of neutrino oscillations. That phenomena implies that neutrinos are massive and shows the existence of physics beyond the standard model. Fundamental questions associated to this discovery are: what are the absolute neutrino masses? and what is their hierarchy? In this talk I will discuss how to use cosmological observables to answer these questions. I will first show one of the predictions of the Big Bang theory: the existence of a cosmic neutrino background.
I will first outline an effective field theory for cosmology (EFTC) that is based on the Standard Model coupled to General Relativity and improved with Weyl symmetry. Any version of quantum gravity (QG), including string theory, must include the same improvement, otherwise QG will not be geodesically complete.
Burst phenomena are ubiquitous in astrophysics. Understanding the origin of bright and rapid bursts, like FRBs, is an important goal of contemporary astrophysics. We apply Dicke's superradiance, a coherent quantum mechanical radiation mechanism, to explain these burst phenomena. We show that bursts lasting from a few milliseconds (FRBs) to a few years (e.g. OH masers) can be produced by very large groups of entangled atoms/molecules. This is in contrast with the common assumption that, in the interstellar medium, the atoms/molecules in a radiating gas act independently from each other.
Axions are attractive candidates for theories of large-field inflation that are capable of generating observable primordial gravitational wave backgrounds. These fields enjoy shift-symmetries that protect their role as inflatons from being spoiled by coupling to unknown UV physics. This symmetry also restricts the couplings of these axion fields to other matter fields. At lowest order, the only allowed interactions are derivative couplings to gauge fields and fermions.
The next frontiers in cosmic microwave background (CMB) science include a detailed mapping of the CMB polarization anisotropy, with goals of detecting the inflationary B-mode signal and reconstructing high-fidelity maps of the matter distribution via CMB lensing, as well as a first detection of CMB spectral distortions. At this level of precision (~nK), Galactic and extragalactic foregrounds may be the ultimate limiting factor in deriving cosmological constraints. I will discuss biases due to foregrounds in CMB lensing measurements, including the first calculation of the lensing bias due
Gravitational lensing of the cosmic microwave background has emerged as a powerful cosmological probe, made possible by the development and characterization of nearly-optimal estimators for extracting the lensing signal from temperature and polarization maps. One can ask whether similar tools can be applied to upcoming "intensity maps" of emission lines at other wavelengths (e.g. 21cm). In this talk, I will present recent work in this direction, focusing in particular on the impact of gravitational nonlinearities on standard quadratic lensing estimators.
The lensing convergence measurable with future CMB experiments will be highly correlated with the clustering of galaxies that will be observed by imaging surveys such as LSST. I will discuss prospects for using that cross-correlation signal to constrain local primordial non-Gaussianity, the amplitude of matter fluctuations as a function of redshift, halo bias, and possibly the sum of neutrino masses. A key limitation for such analyses and large-scale structure analyses in general is that the mapping from initial conditions to observables is nonlinear for wavenumbers k>0.1h/Mpc.