September 28, 2018

Will Farr: The New Field of Gravitational Wave Astronomy

Forty years in the making, the field of gravitational wave astronomy opened with a bang in September 2015 with the first-ever detection of the gravitational waves from a merging pair of black holes. These extreme objects contain 30 to 40 times as much mass as the sun, but are about the size of Manhattan; they slammed into each other at about half the speed of light! The energy generated by the collision outshone, for a moment, all the stars in the universe; here on earth, the signal was sufficiently strong to move person-sized mirrors in the LIGO instruments a distance that is a tiny fraction of an atomic nucleus. Thanks to work by thousands of scientists around the world, the LIGO instruments were able to detect such a tiny displacement, and record the gravitational wave. Subsequently, LIGO (and its European partner, Virgo) has announced five more black hole mergers and, last August, the merger of two neutron stars. This latter event involved city-sized atomic nuclei, again slamming into each other at a large fraction of the speed of light; the result of the explosion was apparent in both gravitational waves *and* by a flash of gamma rays, followed by a glow that faded over hundreds of days that was observed by thousands of astronomers using traditional telescopes around the world. Thanks to these observations, we now know that events like this one are responsible for producing a sizable fraction of the elements heavier than iron---gold, for example---in the universe. This talk will describe the how the LIGO detectors make such phenomenally sensitive measurements, go over some of the highlights from the past two years' observations and talk about the very bright future of this new field.

Will Farr is a new Associate Professor of Physics at Stony Brook; he also leads the gravitational wave astronomy group at the Flatiron Institute's Center for Computational Astronomy in Manhattan. Until this fall, he was a Senior Lecturer at the University of Birmingham, working in that institution's Institute for Gravitational Wave Astronomy.

October 26, 2018

George Sterman: Imaging Fundamental Processes

The contemporary theory of fundamental forces can be pictured as just a handful of particle species, acting among themselves according to a few simple rules. This theory can in principle account for the richness of the visible universe. It results from a centuries-long process of speculation and investigation, culminating in the language of quantum field theory. Yet every successful theoretical framework defines its own limitations, and suggests new questions and criteria. Looking back and ahead, I will give a perspective on our current theories, and on how future developments may be influenced by evolving ideas in theoretical physics, by high energy experiments at accelerators, and by exquisite observations of the faintest cosmic signals.

George Franklin Sterman is a theoretical physicist and the Director of the C. N. Yang Institute for Theoretical Physics at Stony Brook University where he holds the rank Distinguished Professor. George Sterman's research focuses on quantum field theory and its applications in quantum chromodynamics. He authored a textbook entitled An Introduction to Quantum Field Theory in 1993.[ George Sterman was awarded the 2003 J.J. Sakurai Prize for Theoretical Particle Physics "For developing concepts and techniques in QCD, such as infrared safety and factorization in hard processes, which permitted precise quantitative predictions and experimental tests, and thereby helped to establish QCD as the theory of the strong interactions."[5] He received a Guggenheim Fellowship in 1985, is a Fellow of the American Physical Society and has served as an Associate Editor for Physical Review Letters.

November 30, 2018

Christopher J. Johnson: From Molecules to Clouds – How do Atmospheric Particles Form from Thin Air?

Atmospheric particles, including familiar objects such as dust or smoke, have a significant impact on Earth’s climate and human health. Despite their ubiquitous presence, they remain mysterious, primarily due to their extreme chemical complexity. Among the most mysterious are so-called new particles, which form directly out of thin air and can grow into rain droplets or snowflakes. These new particles, which are too small to see with a microscope, can typically only be studied indirectly, and so fundamental questions like how they interact with water remain unsolved. I will discuss the origins of these particles and how they are expected to impact climate, and my research group’s experiments to figure out how and why they grow. We have constructed an instrument that gives us to control, exactly select, and grow particles, as well as powerful analysis techniques to determine why they grow. The key advance for this work is the use of ion traps, which allow us to float particles in a precisely-defined atmosphere and follow their growth one molecule at a time. Using this capability, we are starting to determine some of the structural transformations occurring as the particles mature and the role of water in the mechanism of growth.

Chris Johnson is an Assistant Professor in the Department of Chemistry at Stony Brook University. His research interests revolve around understanding how weak molecular forces give rise to large-scale behavior in nanometer sized particles. He received a B.S. in Physics from Butler University in Indianapolis, IN, and a Ph.D. in Physics from the University of California, San Diego. Following three years of postdoctoral research in the Chemistry Department at Yale University, he joined the faculty at Stony Brook University in 2014.