Cosmology

Since the discovery of the first exoplanets in the early 1990s, we have detected more than 4,000 worlds beyond our solar system. Many of these are similar in size to our Earth, leading to an obvious question: could any be habitable?

For now, we typically only know the size and orbit of these planets, but nothing about their surface conditions. Although we cannot know for sure if these worlds could support life, we can use models to speculate on what we might find there.

In her Nov. 6 talk at Perimeter Institute, astrophysicist and author Elizabeth Tasker will take audiences for a speculative stroll through a few of the alien worlds we’ve discovered in the galaxy, and ponder whether someone else may already call them home.

Elizabeth Tasker is an astrophysicist at the Japan Aerospace Exploration Agency (JAXA). Her research explores the formation of stars and planets using computer simulations. She is particularly interested in how diverse planets might be and what different conditions might exist beyond our Solar System. Elizabeth is also a keen science communicator and writer for the NASA NExSS “Many Worlds” online column. Her popular science book, The Planet Factory, was published in Canada last April.

The influx of new and high-quality cosmological data from upcoming cosmic microwave background (CMB) and large-scale structure surveys will provide unique and exciting opportunities to study the fundamental constituents of the Universe in the upcoming few years. In particular, measurements of second-order effects in the CMB will become observationally significant for the fist time as surveys will achieve the necessary precision. Such second-order effects include weak gravitational lensing by large-scale structure; the integrated Sachs-Wolfe and Rees-Sciama effects, which describe the redshift effect on CMB photons due to evolving gravitational potentials along the line of sight; and the Sunyaev-Zel'dovich effect where CMB photons Compton scatter with free electrons in galaxy clusters and the intergalactic medium. In parallel, surveys of the 21cm hydrogen line will achieve sufficient accuracy for cosmological inference. In this talk I will describe how these new cosmological probes provide opportunities to study old fundamental problems. I will focus on two new probes: the moving lens effect on the CMB (Hotinli 2019, PRL) and the velocity acoustic oscillations (`so-called' VAOs) in the 21cm hydrogen. I will describe how these observables can be utilised to constrain a class of early Universe models.

Ghostly neutrino particles continue to bring surprises to fundamental physics, from their existence to the phenomenon of neutrino oscillation which implies that their masses are nonzero. Their exact masses, among the most curious unknowns beyond the Standard Model of particle physics, can soon be probed by the joint analysis of upcoming cosmological surveys including LSST, Euclid, WFIRST, Simons Observatory, and CMB-S4. In this talk, I will first discuss ongoing work studying the effects of massive neutrinos. I will then turn the focus to my major efforts of modeling the challenging nonlinear regime of cosmic structures (<10 Mpc) where neutrino effects are the strongest. Finally, I will draw a roadmap to pin down the neutrino mass over the next decade.