Talks

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.

In this talk, I will describe some of the recent progress on computing holographic correlators using analytic bootstrap techniques combined with supersymmetric localization.  From taking a certain flat space limit of the holographic correlators, one can obtain scattering amplitudes of gravitons in string theory, and one can then reproduce some of the known results for these scattering amplitudes.  I will focus mostly on the case of the 4d {\cal N} = 4 super-Yang-Mills theory, but I will also mention related work in the 3d ABJM theory.

 Python is a widely used programming language for scientific
computing, data analysis, and machine learning. This tutorial will
feature an introduction for those with little or no background.

Non minimal couplings of scalar fields to gravity are a generic feature of Lagrangian formulations of gravity. Although challenging to probe at low energies and small curvature, such couplings can play a crucial role in cosmological setups. We focus on their impact in the production of scalar dark matter and its interplay with inflationary physics. We show how the standard non-thermal production mechanism of scalar dark matter, the misalignment mechanism, is modified, and explore how alternative scenarios like production from inflationary fluctuations become viable. We study potentially observable features of these scenarios, such as the enhancement of dark matter substructure at small scales and the generation of an isocurvature component in the fluctuations of the CMB.

A massive U(1)' gauge boson known as a “dark photon” or A', has long been proposed as a potential explanation for the muon g − 2 anomaly. Recently, experimental results have excluded this possibility for a dark photon decaying visibly and invisibly. I revisit this idea and consider a model where A' couples to inelastic dark matter, leading to a semi-visible decay mode. I show that for large mass splittings between the dark sector states this decay mode is enhanced, weakening the invisibly decaying dark photon bounds. As a consequence, A' resolves the g −2 anomaly in a region of parameter space the thermal dark matter component of the Universe is readily explained.