Colloquium Archives (before June 2017)

More recent colloquia are posted on the Physics & Astronomy Colloquia page.

Dimitar Sasselov, Harvard-Smithsonian Center for Astrophysics Origins Institute

Topic: "Kepler and Habitability of Exoplanets"  (Video)

ABSTRACT: My talk will describe the NASA Kepler mission goals and current results in light of theoretical work on the structure and atmospheres of Super-Earth planets. The environments that are expected to develop on these classes of planets are evaluated from the potential for developing and sustaining a biochemistry - similar to terran or alternative to it.

Frank Wilczek, MIT, 2004 Nobel Prize of Physics, Author

Topic: "Anticipating a New Golden Age"  (Video)

ABSTRACT: Fundamental physics is poised to take a great leap forward in coming years. An extraordinary instrument - the Large Hadron Collider, or LHC - will enable us to see whether some gorgeous ideas about the ultimate laws of physics correctly describe reality. Nature has given us hints: Is she teaching, or teasing? In a multimedia presentation including rap video, spectacular images, some amazing ideas, and a few jokes, I'll demonstrate why this is an especially exciting time to be a physicist - or a curious person.

Hal Evans, University of Indiana

Topic: "The Little Bang: First Physics from the LHC"  (Video)

ABSTRACT: The recent history of the Large Hadron Collider at CERN in Geneva, Switzerland has been a alpine range of dizzying peaks and harrowing valleys. Befitting its massive size, both the successes and the failures of the LHC, and its four experiments, ALICE, ATLAS, CMS, and LHCb, have been on a grand scale. We have now entered a particularly exciting phase of the project, with first proton-proton collisions at high energy having been produced recently. I will review the long and eventful path that brought us to this hopeful stage, discuss our recent accomplishments, and speculate on future directions we might take. As a member of the ATLAS collaboration, I will illustrate our journey with recent results from first data collected with that experiment. One truth we've already discovered though is: expect the unexpected! Who knows what surprises await us between now and the time of this colloquium?

Armin Rest, CFA, Harvard University

Topic: "An Astronomical Time Machine: Light Echoes from Ancient Supernovae"  (Video)

ABSTRACT: Tycho Brahe's observations of a supernova in 1572 challenged the Church dogma that the celestial realm was unchanging. 438 years later we have once again seen the light that Tycho saw: some of the light from the 1572 supernova is reflected off dust clouds and is only now reaching Earth. These light echoes, as well as ones detected from other supernovae, give us a very rare opportunity in astronomy: direct observation of the cause (the supernova explosion) and the effect (the supernova remnant) of the same astronomical event. Furthermore, in some cases we can compare light echoes at different angles around a supernova remnant, and thus investigate possible asymmetry in the supernova explosion. I will discuss several examples where we are using this technique to "transport ourselves backwards in time" to study ancient supernova events.

Lorenza Viola, Department of Physics and Astronomy, Dartmouth College

Topic: "Untangling Entanglement: An Observer-Dependent Perspective"  (Video)

ABSTRACT: Entanglement is one of the most fundamental and yet most elusive properties of quantum mechanics. Not only does entanglement play a central role in quantum information science, it also provides an increasingly prominent bridging notion across different subfields of Physics --- including quantum foundations, quantum gravity, quantum statistical mechanics, and beyond. The property of a state being entangled or not is by no means unambiguously defined. Rather, it depends strongly on how we decide to regard the whole as composed of its part or, more generally, on the restricted ways in which we are able to observe and control the system at hand. I will argue how acknowledging the implications of such an operationally constrained point of view leads to a notion of "generalized entanglement," which is directly based on observables and offers added flexibility in a variety of contexts. Time permitting, I will survey some accomplishments of the generalized entanglement program to date, with an eye towards open problems.

Faculty Candidate Chandrasekhar Ramanathan, Department of Nuclear Science and Engineering, MIT

Topic: "Quantum Simulation With Nuclear Spins"  (Video)

Abstract: It has been almost three decades since Feynman showed that a quantum computer is required to efficiently simulate a quantum system. While building a quantum computer remains a grand challenge, recent advances in the control of quantum systems have led to a resurgence of interest in quantum simulations. In addition to providing insight into quantum phenomena, quantum simulators could help tackle problems in diverse areas such as condensed-matter physics, cosmology and quantum chemistry. Many quantum simulations require a more limited degree of control compared to a quantum computer. In this talk I will discuss how to build quantum simulators using nuclear magnetic resonance (NMR) techniques. While we can perform any small-scale simulation using liquid state NMR, the highly-coupled spin networks in solids allow us to perform a more limited set of large-scale analog quantum simulations. I will illustrate these ideas with experimental examples, and discuss the key challenges to developing large scale, general purpose quantum simulators.

Faculty Candidate Alexander Sushkov, Department of Physics, Yale University

Topic: "Why Does the Universe Have More Matter Than Anti-Matter? A Search for Violation of Parity and Time-Reversal Symmetries"  (Video)

Abstract: The 2008 Nobel Prize in physics was awarded to Nambu, Kobayashi, and Maskawa for their study of nature's broken discrete symmetries (charge conjugation C, parity P, and time reversal T). However what we know about the breaking of these symmetries is not enough to explain the apparent matter-antimatter asymmetry of the universe. One of the ways to study the breaking of parity and time-reversal symmetries is to search for the permanent electric dipole moment (EDM) of the electron. I will describe an experimental search for this EDM, based on a solid paramagnetic ferroelectric Eu_{0.5} Ba_{0.5} Ti O_3. We expect a preliminary improvement of the current EDM limit by a factor of 10, with the sensitivity gain originating from large densities n = 10^{22} cm^{-3}, and from large effective electric fields E = 10 MV/cm, due to the ferroelectric displacement of the ions in the crystal lattice field.

Faculty Candidate Jesse Berezovsky, School Of Engineering and Applied Science, Harvard University

Topic: "Imaging Coherent Electron Transport in Graphene"  (Video)

Abstract: The coherent flow of electrons through a graphene device is an intriguing physical problem, which must be understood for future quantum technologies. We have developed a low-temperature scanningnprobe technique for mapping the effect of a single movable scatterer on coherent transport in graphene. We obtain images of conductance vs. scatterer position that provide a spatial view of the interference of electron waves that create universal conductance fluctuations and weak localization.