Talks

Neutron stars are a celestial gift to scientists. These incredibly dense collapsed stars act as very precise cosmic beacons that help shed light on some of the most challenging problems in modern physics.

In her Feb. 3 talk at Perimeter Institute, astrophysicist Victoria Kaspi will explore these strange objects, explain how astronomers are using them to study issues ranging from the origins of the universe to the very nature of matter, and even let the audience hear the cosmic symphony they create.

Fathoming interplay between symmetry and topology of many-electron wave-functions has deepened understanding of quantum many body systems, especially after the discovery of topological insulators. Topology of electron wave-functions enforces and protects emergent gapless excitations, and symmetry is intrinsically tied to the topological protection in a certain class. Namely, unless the symmetry is broken, the topological nature is intact. We show novel interplay phenomena between symmetry and topology in topological phase transitions associated with line-nodal superconductors. The interplay may induce an exotic universality class in sharp contrast to that of the phenomenological Landau-Ginzburg theory. Hyper-scaling violation and emergent relativistic scaling are main characteristics, and the interplay even induces unusually large quantum critical region. We propose characteristic experimental signatures around the phase transitions in three spatial dimensions, for example, a linear phase boundary in a temperature-tuning parameter phase-diagram. 

Radio pulsars are Nature's most perfect clock and hence are useful for precision work on a wide variety of physical and astrophysical topics, ranging from sensitive tests of relativistic gravity to constraining the equation of state of ultradense matter. I will describe current ongoing surveys for radio pulsars using the two largest radio telescopes in the world, and how these surveys are also valuable for searching for Fast Radio Bursts, a newly recognized astrophysical phenomenon of unknown origin. 

The discovery of postquantum nonlocality, i.e. the existence of nonlocal correlations stronger than any quantum correlations but nevertheless consistent with the no-signaling principle, has deepened our understanding of the foundations quantum theory. In this work, we investigate whether the phenomenon of Einstein-Podolsky-Rosen steering, a different form of quantum nonlocality, can also be generalized beyond quantum theory. While postquantum steering does not exist in the bipartite case, we prove its existence in the case of three observers. Importantly, we show that post-quantum steering is a genuinely new phenomenon, fundamentally different from postquantum nonlocality. Our results provide new insight into the nonlocal correlations of multipartite quantum systems.