Talks

The discrete time-translation symmetry of a periodically-driven (Floquet) system allows for the existence of novel, nonequilibrium interacting phases of matter. A well-known example is the discrete time crystal, a phase characterized by the spontaneous breaking of this time-translation symmetry. In this talk, I will show that the presence of *multiple* time-translational symmetries, realized by quasiperiodically driving a system with two or more incommensurate frequencies, leads to a panoply of novel non-equilibrium phases of matter, both spontaneous symmetry breaking ("discrete time quasi-crystals") and topological. In order to stabilize such phases, I will outline rigorous mathematical results establishing slow heating of systems driven quasiperiodically at high frequencies. As a byproduct, I will introduce the notion of many-body localization (MBL) in quasiperiodically driven systems.

I will describe an example in which ER=EPR can be understood as a worldsheet string duality, by finding the Lorentzian continuation of the FZZ duality. The result is that string perturbation theory around the thermofield double state in a disconnected spacetime with a condensate of entangled folded strings is equivalent to string theory in a connected two sided black hole spacetime. Important ingredients are the Lorentzian interpretation of time winding vertex operators, and string theory with target space Schwinger-Keldysh contours. I will also discuss a related conjecture in AdS3-Rindler.

The core Python language is not particularly powerful or fast for numerical computing.  Fortunately, there is a large "numerical python" library, "numpy", that is a standard part of any Python-using scientist's toolkit.  I will present numpy, the associated "scientific python" library, "scipy", and the popular "matplotlib" plotting library.

I will talk about compact hyperkahler manifolds, which generalize the famous K3 surface to the higher dimensions. Given a compact simple hyperkahler manifold $M$, I will describe how the structure of cohomology algebra H*(M) is related with the so(b_2+2) Lie algebra action and the second cohomology group. I will explain how this is applied to the generalization of Kuga-Satake construction which allows us to assign for K3-type Hodge structure a Hodge structure of weight one (i.e. complex torus).

Advanced LIGO and Advanced Virgo are currently in the middle of their third observing run, and releasing open public event alerts for the first time. The LIGO-Virgo collaboration has issued 29 un-retracted candidate event alerts as of September 20th, 2019, potentially adding dozens more known compact binary object mergers to the eleven confident LIGO-Virgo detections from the first two Advanced-era observing runs. I’ll review novel LIGO-Virgo results to date, and discuss the challenges of extracting interesting new physics from noisy detector data. Finally, I'll summarize future prospects for astrophysics, cosmology, and tests of general relativity with gravitational waves, and the roadmap to future gravitational wave detectors on Earth and in space.

Advances in biotech, cyber-technology, robotics, and space exploration could, if applied wisely, allow a bright future – even for 10 billion people – by the end of this century.

But there are dystopian risks we ignore at our peril.

These risks are of two kinds: those stemming from our ever-greater collective “footprint” on the Earth, and those enabled by technologies so powerful that even small groups can, whether by error or design, cause global catastrophe.

Martin Rees, the UK Astronomer Royal, will explore this unprecedented moment in human history during his Perimeter Institute public lecture on October 2, 2019. A former president of the Royal Society and master of Trinity College, Cambridge, Rees is a cosmologist whose work also explores the interfaces between science, ethics, and politics.

In his October 2 talk – which kicks off the 2019/20 season of the Perimeter Institute Public Lecture Series – Rees will discuss the outlook for humans (or their robotic envoys) venturing to other planets. Humans, Rees argues, will be ill-adapted to new habitats beyond Earth, and will use genetic and cyborg technology to transform into a “post-human” species.

Rees’ talk at Perimeter will cover themes from his 2018 book, On the Future: Prospects for Humanity. Rees is an acclaimed thinker, author, and speaker who belongs to numerous scientific academies around the world. His past books include Before the Beginning, Our Final Century?, Just Six Numbers, Our Cosmic Habitat, and Gravity’s Fatal Attraction.

Hypermassive neutron stars (HMNS) can be briefly formed after a binary neutron star merger and are likely to be highly deformed and strongly oscillating. These oscillations may be seen as modulation of the associated short gamma-ray burst and could provide observational evidence for the HMNS phase. I will discuss the prospects for their detection and the important physical information that can be gained by their observation.