Speaker: Prof. Mikhail Lukin, Harvard University
Title: "Exploring new frontiers of quantum optical science"
In this talk we will discuss recent developments involving a new scientific interface between quantum optics, many body physics, nanoscience and quantum information science. Specific examples include
quantum manipulation of individual spins and photons using atom-like
impurities in diamond and control of light-matter interactions using sub-wavelength localization of optical fields. Novel applications of
these techniques ranging from novel approaches to quantum computation at
room temperature to implementation of quantum optical networks and
nanoscale magnetic sensing will be discussed.
Speaker: Dr. Neal Dalal, Canadian Institute for Theoretical Astrophysics, University of Toronto
Title: "The handwaver's guide to dark matter halos"
Dark matter halos are the endpoints of cosmological structure formation. They play a crucial role in many areas of astrophysics and cosmology, and are host to most of the `interesting' objects that we see around us, like galaxies and quasars. Our understanding of halos is based almost entirely on numerical experiments in N-body simulations, with relatively poor theoretical understanding of what determines halo properties. In my talk, I will try to give a simple way to understand many properties of halos, including their internal structure and their abundance. I will show how this approach opens new avenues for exploring our cosmology, with a focus on physics beyond the standard (cosmological) model.
Speaker: Dr. Brad Johnson, NASA
Title: "Revealing the History of the Universe with the CMB"
The CMB is an image of the universe, as it was 380,000 years after the Big Bang, that spans the entire sky. Details of the physical processes that operated in the early universe are captured in the angular intensity and polarization anisotropies. The "primordial anisotropies" encode information about the universe when the CMB formed. In particular, the primordial "B-mode" polarization anisotropy could contain a detectable gravity wave signal produced during the first second after the Big Bang. Experimental research now focuses on searching for and characterizing the forecasted B-mode signal. The "secondary anisotropies" are distortions in the primordial CMB signal that are produced by matter in the universe, so they contain information about the state of the universe between the observer today and the surface where the CMB photons last scattered. CMB photons traveling through the hot plasma in galaxy clusters are inverse Compton scattered, which produces a detectable signal called the thermal Sunyaev Zel'dovich (SZ) effect. The SZ signal can be used to study galaxy clusters and constrain the values of a collection of cosmological parameters. My talk will focus on three experiments. PIPER and EBEX are two balloon-borne experiments under construction that are designed to search for the B-mode polarization of the CMB, and APEX-SZ is a ground-based experiment that has detected approximately 40 galaxy clusters via the SZ signal.
Speaker: Prof. Igor Klebanov, Princeton University
Title: "String Theory and Strong Interactions"
String theory was originally invented to describe hadrons, but soon after Quantum Chromodynamics (QCD) emerged as the precise theory of the strong nuclear force. A quarter century later it was understood that string theory and certain gauge theories akin to QCD are in fact different descriptions of the same physics. I will review some of the basic relations between gauge theories and strings, and will motivate the exact gauge/string dualities by studying coincident D-branes. I will also discuss applications of these ideas to theories at finite temperatures and to theories which exhibit color confinement. The colloquium will also cover some of the recent progress, including calculation of the quantum entanglement entropy, understanding the exact dualities involving Chern-Simons gauge theories, and modeling of the cosmological inflation.
Speaker: Prof. Rene Ong, UCLA
Title: "Particle Astrophysics at the TeV Scale"
Our understanding of the TeV universe has progressed rapidly during the last few years as a result of new instruments and exciting discoveries. In particular,ground-based telescopes, such as VERITAS in southern Arizona, have discovered many astrophysical sources of TeV gamma rays, while at the same time carrying out sensitive searches for the annihilating particle dark matter. This talk will describe what we know about the TeV universe, as revealed by recent results from VERITAS. The future prospects for high-energy gamma-ray and neutrino astronomy will be summarized.
Speaker: Dr. Jonathan Sievers, University of Toronto
Title: "Cosmology from 17,000 Feet: Results from the Atacama Cosmology Telescope"
The Atacama Cosmology Telescope (ACT) is observing the Cosmic Microwave Background (CMB) from high in the Chilean Andes. The CMB provides a snapshot of the universe when it was only 400,000 years old, long before the formation of any stars or galaxies. The nearly uniform density (to a few parts per hundred thousand) means that well understood linear physics describes the physics of the CMB and lets us reliably tranform observations of the CMB into constraints on fundamental parameters of the cosmos. ACT provides a significant improvement to our knowledge of the CMB on small (few arcminute) scales. We present the results from the first full season of ACT data and what we learn from them, including better limits on the number of relativistic species, the initial power spectrum from inflation, early helium density, potential contributions to structure formation from cosmic strings, and the imprint of galaxy clusters on the CMB. We are currently upgrading ACT to have polarization sensitity, and expect it to be on the sky in 2012. We present some of what we expect to learn from ACTpol, including the summed mass of neutrino species to ~0.05 eV, the regime where we expect a detection.
Speaker: Prof. Jonas Zmuidzinas, Caltech
Title: "Submillimeter Astronomy and Cosmology"
Located between the radio and infrared, the submillimeter wavelength band is one of the last to be opened up for astronomical observation and discovery. It is now understood that around half of the electromagnetic energy produced by stars and galaxies since the Big Bang lies in the submillimeter, and that extremely luminous galaxies undergoing huge bursts of star formation may be quite bright at submillimeter wavelengths but invisible to the most powerful optical-infrared telescopes. I will trace the development of the science and technology of submillimeter astronomy from its humble beginnings on the fringes of science in the 1960s and 1970s to the present day, when the largest space telescope ever launched – the Herschel Space Observatory - and the largest ground-based astronomy project in the world – the Atacama Large Millimeter/Submillimeter Array (ALMA) - are both devoted to submillimeter astronomy. The next major step for the field will be the Cornell-Caltech Atacama Telescope (CCAT), a 25 meter submillimeter telescope equipped with wide-field cameras and multi-beam spectrometers that will enable deep and broad surveys of the submillimeter universe. Boosted by a strong endorsement in the 2010 Decadal Survey report, construction of CCAT is expected to commence a few years from now.
Speaker: Prof. Nima Arkani-Hamed, Institute for Advanced Study
Title: "Space-Time, Quantum Mechanics and Scattering Amplitudes"
Scattering amplitudes in gauge theories and gravity have extraordinary properties that are completely invisible in the textbook formulation of quantum field theory using Feynman diagrams. In this
usual approach, space-time locality and quantum-mechanical unitarity
are made manifest at the cost of introducing huge gauge redundancies in
our description of physics. As a consequence, apart from the very
simplest processes, Feynman diagram calculations are enormously
complicated, while the final results turn out to be amazingly simple, exhibiting hidden infinite-dimensional symmetries. This strongly
suggests the existence of a new formulation of quantum field theory
where locality and unitarity are derived concepts, while other physical
principles are made more manifest. The past few years have
seen rapid advances towards uncovering this new picture, especially for
the maximally supersymmetric gauge theory in four dimensions. These developments have interwoven and exposed connections between a
remarkable collection of ideas from string theory, twistor theory and
integrable systems, as well as a number of new mathematical structures
in algebraic geometry. In this talk I will review the current state of
this subject and and describe a number of ongoing directions of research.
Speaker: Prof. Dam Thanh Son, University of Washington
Title: "Viscosity, quark gluon plasma, and string theory"
Viscosity is a very old concept which was introduced to physics by Navier in the 19th century. However, in strongly coupled systems viscosity is extremely difficult to compute from first principles. In this talk I will describe some recent surprising developments in string theory which allow one to compute the viscosity for a class of strongly interacting fluids not too dissimilar to the quark gluon plasma. I will describe efforts to measure the viscosity and other physical properties of the quark gluon plasma created in heavy ion collisions.
Speaker: Prof. Elena Aprile, Columbia University
Title: "The Search for Dark Matter with the XENON100 Experiment"
The XENON100 experiment is designed to search for interactions of dark matter Weakly Interacting Massive Particles (WIMPs) in a liquid xenon time projection chamber. Featuring a large target mass and an extremely low background, XENON100 is the most sensitive dark matter direct detection experiment in operation today. Located deep underground at the Gran Sasso National Laboratory, in Italy, XENON100 has recently reported results on the elastic scattering of dark matter WIMPs with nucleons, based on 100 days of data acquired in 2010. The recent findings, the status of the experiment and the work towards the next generation XENON1T experiment will be presented.
**Special Seminar at 1:00 PM in 428 Pupin Hall**
Speaker: Prof. Michael Norman, Argonne National Laboratory
Title: "AdS/CFT - Playing the Devil's Advocate"
AdS/CFT is a conjectured duality between weak coupling gravity in anti de Sitter space and a strong coupling field theory on the boundary of this space. It has been suggested that a variety of phenomena in condensed matter physics might be explained by this approach. We will take a serious look at several of these, including the presence of Fermi arcs in the pseudogap phase, the peak-dip-hump lineshape in the superconducting state, and the origin of cuprate superconductivity. In all of these cases, I will argue that AdS/CFT has not shed much light, nor is likely to, on the basic issues being debated.
Speaker: Prof. Roderich Moessner, Max Plank Institute for Complex Systems, Dresden, Germany
Title: "Magnetic Monopoles in Spin Ice"
Fractionalisation is a counterintuitive phenomenon, in which an 'elementary' particle appears to break into two independent entities. A celebrated example of this is spin-charge separation, in which an electron's magnetic (spin) and electric (charge) degrees of freedom appear to become independent.Spin ice materials such as Dy2 Ti2 O7 and Ho2 Ti2 O7 provide a rare instance of fractionalisation in three dimensions: their elementary excitations carry a fraction of the magnetic moment of the microscopic spin degrees of freedom, and they can be thought of as magnetic monopoles.The peculiar nature of these excitations leads to unique signatures in the properties of spin ice materials in and out of equilibrium. These include unusual neutron scattering structure factors, dynamical arrest and long lived non-equilibrium metastable states, as well as a response to external magnetic fields that promotes spin ice as a magnetic analogue of an electrolyte. This talk reviews several of these striking phenomena, and discusses open questions and future perspectives.
*** Please note that the Colloquium has been moved to 329 Pupin Hall***