Colloquia are held on Mondays at 4:00pm (Refreshments at 3:30pm) in Barus & Holley 168
April 21, 2014 - Ian Fisher (Stanford University)
"Electronic nematic phases in high temperature superconductors"
In recent years, anisotropic electronic phases have been discovered in a variety of strongly correlated quantum materials. Borrowing language from the field of soft condensed matter physics, such phases are referred to as electronic nematic phases when they break a discrete rotational symmetry of the crystal lattice without further breaking translational symmetry. The physical origin of electronic nematic order is unclear, as are the implications for other broken symmetry states, including superconductivity, motivating the development of tools and techniques that probe electronic nematicity. In this talk I'll outline a new technique that measures an associated quantity, the nematic susceptibility, which provides important insight to nematic fluctuations in a material. Measurements of this quantity directly reveal the presence of an electronic nematic phase transition in a family of high temperature superconductors, and an associated quantum phase transition near optimal doping (i.e. the doping that yields the maximum critical temperature of the superconductor). I'll explain the possible significance of this observation.
January 27, 2014- George Zweig (MIT)
"Concrete Quarks - The Beginning of the End" (Video)
A short history of the physics of strongly interacting particles is presented. Events leading to the discovery, and eventual acceptance, of concrete quarks are described.
February 10, 2014 - Joao Guimaraes de Costa (Harvard University)
"A Closer Look at the Higgs Boson with the Large Hadron Collider"
Scientists at CERN have been exploring the high energy frontier with the Large Hadron Collider since March 2010. The substantial dataset accumulated thus far, albeit at lower energy than initially foreseen, already yielded a Nobel prize award for the discovery of the Higgs Boson.
The new boson, discovered in 2012 by the ATLAS and CMS collaborations, has been shown to behave very much like the long-sought-after Higgs Boson, and hence it completes the discovery of the Standard Model of Particle Physics. Remarkably, no other deviations from the Standard Model have been found, neither in precision measurements nor in direct searches for new particles. The LHC will resume operations in 2015, after a 2-year shutdown, with increased center of mass energy, and thus, with increased potential for new discoveries. In this talk, I will review recent measurements at the LHC, with a focus on the study of the properties of the newly discovered boson, and will briefly discuss what we expect to learn from the future LHC data.
February 24, 2014 - David Pine (New York University)
"Colloids with directional interactions"
We have developed new kinds of colloidal particles with either geometrical or chemical patches that give rise to directional interactions. These interactions allow colloids to interact with each other more like atoms, which in turn are used to build up structures that are not possible with isotropic interactions. These directional interactions are being developed to make self-replicating colloidal motifs and new colloidal crystals.
March 3, 2014 - Raymond Brock (Michigan State)
"That Spin 0 Boson at CERN Changes Everything: The Future of the Energy Frontier in Particle Physics"
I’ll argue that the "Higgs Boson" discovery requires us to think differently about planning for the future of Particle Physics. While the decades-long confirmation of the Standard Model itself an historic episode in the history of physics, as a model of nature it is unhelpful as a clear guide to the future. I’ll review the features of the Standard Model that make it superb, I’ll point out why it’s frustrating, and I’ll describe the hints that motivate us in the coming decades. Last year the particle physics community went through a self-study of future opportunities. I’ll review some of the “Snowmass Workshop” especially as it pertains to the future of collider physics.
March 10, 2014 - Joshua Winn (MIT)
"Spin-Orbit Interactions for Exoplanets"
In the Solar system, the planets follow orbits that are aligned with
the Sun's equatorial plane to within a few degrees. But what about
planets around other stars? Recently we have measured the spin-orbit angles of about 50 stars with exoplanets, using a technique first theorized in the 19th century, as well as several new techniques based on data from the NASA Kepler spacecraft. Many exoplanetary systems have good alignment, as in the Solar system -- but there are also many surprises. I will discuss these results and their implications for theories of planet formation, and tidal spin-orbit interactions. I will also describe the Transiting Exoplanet Survey Satellite, a NASA mission that will improve upon Kepler by discovering exoplanets around stars that are brighter, closer to the Earth, and easier to study.
March 17, 2014 - Raul Jimenez (University of Barcelona)
"Large scale structures, their statistics, neutrino masses and fundamental Physics"
Mapping the large scale structure of the Universe has provided us with an exquisite 3D view of the development and growth of structure since the Big Bang. Now that we have a well established standard cosmology model (LCDM), it is possible to learn fundamental physics from the statistics of large scale structures. In this talk I will describe how we can learn about neutrino physics (in particular about the absolute mass scale and its hierarchy), axion physics, dark energy and dark matter. In summary: the Universe provides an outstanding tool to learn about how nature has decided to extend the standard model of particle physics; I will discuss new developments on this front as well.
March 31, 2014 - Igor Herbut (Simon Fraser University)
"Fundamental physics with two-dimensional carbon"
The two-dimensional form of carbon, also known as graphene, has been hailed as wonder material promising, and already delivering, many useful applications. This is not the only reason, however, why many theoretical physicists have been fascinated with this new material over the last ten years. The reason is also that the electronic structure of graphene provides an unusually simple and affordable playground for studies of some of the basic concepts of modern quantum physics. In this lecture I will attempt to give an elementary discussion of three of these: 1) Mott-insulator (or "Higgs") quantum phase transition, and the emerging relativity, 2) the spontaneous braking of "chiral" symmetry, and the "Dirac masses" of graphene, and 3) the Jackiw-Rebbi zero-modes, topological defects, and their (Clifford) algebras.
April 7, 2014 - Arthur O. Williams Lecture: Robert Meyer (Brandeis University) (Note: Lecture will be held in BH 166)
"Ancient Roman Technology: The Stability of Vaulted Masonry Structures” (poster)
In imperial Rome, the use of vaulted structures, arches, domes and other forms of vaults, built of stone and concrete, was developed to a degree never seen before. Bridges and aqueducts were built throughout the empire. Vast spaces could be enclosed with an economy of material, for use as temples, baths, meeting places, markets, and palaces. This lecture seeks to develop an understanding of the principles determining the stability of some of these structures, which served as the basis for later developments, including the great cathedrals of the Middle Ages and the Renaissance.
April 14, 2014 - Juan Restrepo (University of Arizona)
"Estimation Challenges in Climate and the Geosciences"
Accounting for uncertainties has also led us to alter our expectations of what is predictable and how such predictions compare to nature: in effect, to take on a more Bayesian approach to scientific research as well as to embrace more seamlessly the statistical and deterministic realms.
I will enumerate a few important geoscience problems that live in the realm of the deterministic and the statistical and describe, briefly, our Group's approach and progress on these. Among these I will choose a time series analysis project to provide more details on the methods we use to pursue this Bayesian research program.