Talks

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration has recently reported evidence for the background of low-frequency gravitational waves using an array of rapidly rotating, highly stable radio pulsars distributed across the galaxy. Each pulsar emits a radio beam that passes our line of sight and is observed as regular, pulsed emission. We measure the times of arrival of pulses and compare with a model that includes: the rotational motion of the pulsar, orbital motions, and interstellar propagation delays; random timing noise from pulsars themselves and from the interstellar medium; and finally a correlated gravitational-wave signal recently reported on in a suite of papers. I will highlight our recent results, including implications for the dynamics of supermassive black hole binary at the centers of merging galaxies, searches for individual supermassive black hole binary systems, and searches of gravitational wave signals from new physics. I will end by highlighting future prospects for radio facilities that will advance our look into this newly opened window to the Universe.

---

Zoom link

The Sunyaev-Zel’dovich Effect—the Doppler boost of low-energy Cosmic Microwave Background photons scattering off free electrons—is an excellent probe of ionized gas residing in distant galaxies. Its two main constituents are the kinematic SZ effect (kSZ), where electrons have a non-zero line-of-sight (LOS) velocity and which probes the electron line-of-sight momentum, and the thermal SZ effect (tSZ), where electrons have high energies due to their temperature, and which probes the electron integrated pressure. These two effects provide complementary information to constrain the thermodynamic profile of gas residing in distant galaxies, which can be further used to understand feedback processes, a necessary ingredient to describe the evolution of the large-scale structure in our Universe. Both tSZ and kSZ can be measured in cross-correlation with large-scale structure. In this talk, I will discuss my past and ongoing measurements of the SZ-galaxy cross-correlation with unWISE galaxies, where to measure the kSZ effect I use the projected-fields estimator. unWISE is a galaxy catalog containing over 500 million galaxies on the full sky and consists of three subsamples of mean redshifts z=0.5, 1.1, 1.5, whose halo occupation distribution I have already constrained. If time permits, I will also present my work on mitigating foregrounds in the SZ cross-correlations, particularly the Cosmic Infrared Background (CIB).

--- 

Zoom link

The principle of information causality, proposed as a generalization of no signaling principle, has efficiently been applied to outcast beyond quantum correlations as unphysical. In this talk, we show that this principle, when utilized properly, can provide physical rationale toward structural derivation of multipartite quantum systems. In accordance with the no signaling condition, the state and effect spaces of a composite system can allow different possible mathematical descriptions, even when descriptions for the individual systems are assumed to be quantum. While in one extreme, namely, the maximal tensor product composition, the state space becomes quite exotic and permits composite states that are not allowed in quantum theory, the other extreme - minimal tensor product composition - contains only separable states, and the resulting theory allows only Bell local correlation. As we show, none of these compositions is commensurate with information causality, and hence cannot be the bona-fide description of nature. Information causality therefore promises an information-theoretical derivation of self duality of the state and effect cones for composite quantum systems.

---

Zoom link

Artificial Intelligence and big data are dramatically transforming the way we work, live and connect. Innovators have begun designing AI solutions to advance society at a rapid pace, but often new technologies bring both promise and risk. How can we trust AI and safeguard society from unintended consequences to ensure a safe and human-centred digital future?

Join the University of Waterloo in partnership with the Perimeter Institute for the TRuST Scholarly Network’s Conversations on lecture series where technology leaders from UWaterloo, Google and NASA will discuss how AI is transforming society and if we should trust these technologies.

The recent breakthrough in the detection of gravitational waves (GWs) from merging black hole (BH) and neutron star (NS) binaries by advanced LIGO/Virgo has generated renewed interest in understanding the formation mechanisms of merging compact binaries, from the evolution of massive stellar binaries and triples in the galactic fields, dynamical interactions in dense star clusters to binary mergers in AGN disks. I will review different aspects of the dynamical formation channels, and discuss how observations of spin-orbit misalignments, eccentricities, masses and mass ratios in a sample of merging binaries by aLIGO can constrain these formation channels. The important roles of space-borne gravitational wave detectors will also be discussed.

---

Zoom link