Spring 2016 - Donald R. Hamilton Colloquium Series
4:30 PM Jadwin A10 (the April 21 colloquium will be in McDonnell A02)
Thursday, February 11, 2016
Neuroscience Institute and Computer Science Department
"Structure and function of the retina"
The importance of determining and interpreting the structures of atoms, crystals, and proteins was established long ago. I will discuss current efforts to extend this paradigm to the brain, focusing on new discoveries concerning the structure of the retina gained through 3D electron microscopy, computer vision, and crowdsourcing. I will also describe how such structural information is helpful for understanding how the retina carries out the first steps of visual perception.
Host: N. Phuan Ong, Department of Physics, Princeton University
Thursday, February 25, 2016
Joseph Curtin, Joseph Curtin Studios
“Can Stradivari’s Sound Be Measured?”
A longstanding goal of violin research has been to establish objectively measurable parameters for violin quality. These would presumably substantiate one of the violin-world’s most passionately held beliefs: Violins made by Stradivari and his contemporaries in 18th Century Italy sound better than any made elsewhere or since. However, a team of researchers led by Claudia Fritz and Joseph Curtin have shown that, under double-blind conditions, neither professional violinists nor experienced listeners can tell Old Italian violins from new ones at better than chance levels. Moreover, players and listeners tend to prefer the new. Violin-maker, researcher, and MacArthur Fellow Joseph Curtin will discuss recent developments in violin science, and his own interest in measuring violin sound. He will also preview the team’s upcoming paper: “Objective parameters for violin quality.”
Thursday, March 3, 2016
Kerstin Perez, Haverford College
“In Search of Cosmic-Ray Antinuclei from Dark Matter”
Cosmic-ray antiprotons have been a valuable tool for dark matter searches since the 1970s. Recent years have seen increased theoretical and experimental effort towards the first-ever detection of cosmic-ray antideuterons, in particular as an indirect signature of dark matter annihilation or decay in the Galactic halo. In contrast to other indirect detection signatures, which have been hampered by the large and uncertain background rates from conventional astrophysical processes, low-energy antideuterons provide an essentially background-free signature of dark matter, and low-energy antiprotons are a vital partner for this analysis. I will discuss the currently planned or ongoing experiments that will be sensitive to antideuteron flux levels predicted for dark matter, focusing on the balloon-borne GAPS experiment, which exploits a novel detection technique utilizing exotic atom capture and decay to provide both a sensitive antideuteron search and a precision antiproton measurement in an unprecedented low-energy range. I will finish by looking ahead to the tantalizing prospect of cosmic antihelium measurements, as a probe of both cosmic-ray and dark matter physics.
Thursday, March 10, 2016
Dam Thanh Son, University of Chicago
"Surprises with Dirac fermions in condensed matter"
Starting with the discovery of graphene, the Dirac equation has appeared in many different contexts in condensed matter physics. In this talk I will describe two recent developments: the effects of chiral anomalies in Weyl and Dirac materials, and the Dirac nature of the composite fermion in the many-body physics of the half-filled Landau level.
Thursday, March 31, 2016
David Snoke, U. Pittsburgh
"Superfluids of light: Bose-Einstein condensation of polaritons in microcavities"
In specially designed solid microcavities, the photon properties can be altered to have effective mass and repulsive interactions; these new states are called "polaritons". The polaritons act like atoms, and because they are bosons, they can undergo Bose-Einstein condensation. The experiments on polariton condensation have shown truly remarkable progress in recent years, with new results showing superfluidity and quantized vorticity in a ring geometry. I will review the state of the art in the field, including results from our lab in Pittsburgh which show quantized vorticity, and measurements of the phase diagram for the polariton condensation.
Donald R. Hamilton Lecture
8:00 pm, Thursday, April 7, 2016
McDonnell Hall A-02
Gary Horowitz, UC-Santa Barbara
"Strange Views of Space and Time: From Einstein to String Theory"
Our understanding of space and time was revolutionized a hundred years ago by Einstein’s discovery of his special and general theories of relativity. We have recently undergone another dramatic change in our understanding of these fundamental concepts due to advances in string theory. I will describe these major developments in a nontechnical manner, and explain the strange views of space and time that we are presented with today.
Hosts: Frans Pretorius and Igor Klebanov, Princeton University
(lecture is free and open to the public)
Thursday, April 14, 2016Vladan Vuletic, MIT
Lester Wolfe Professor of Physics
"What does the Golden Ratio have to do with friction? An answer atom by atom"
Friction is the basic, ubiquitous mechanical interaction between two surfaces that results in resistance to motion and energy dissipation. To test long-standing atomistic models of friction processes at the nanoscale, we have implemented a synthetic nanofriction interface using laser cooled ions subject to the periodic potential of an optical standing wave. We show that stick-slip friction can be tuned from maximal to nearly frictionless via arrangement of the ions relative to the periodic potential, and that friction at the nanoscale can substantially differ from the simple phenomenological laws observed at the macroscale. We also establish a direct link between Aubry’s structural transition for an infinite chain in an incommensurate periodic potential, and the vanishing of friction in nanocontacts.
Thursday, April 21, 2016 **Location: McDonnell A02**
Speaker: Harald Hess, HHMI Janelia Research Campus
"Innovating Microscopy: From Atoms to Biology"
Microscopy has played important roles in revealing new insight in diverse fields of research ranging from physics to biology. It likewise is an important component of controlling nano-scale structures in the semiconductor industry. I will trace my own path of adapting various forms of scanned probe microscopy to image vortices, electrons, and quantum wells for basic physics research. A decade in industry taught the methodology and importance of high throughput imaging and massive data processing, (the Giga to complement the Nano). A lucky break allowed me and former Bell Labs colleague, Eric Betzig, to apply such lessons to biology with the innovation of photo-activated localization microscopy PALM and extensions. Recently electron microscopy where innovations in 3D high volume imaging are enabling neural tissue and cellular imaging with volume scales and resolution not previously accessed. How to extend and harness such data sets and translate them to biology remains a major challenge.
Host: Robert Austin, Department of Physics, Princeton University