Speaker: Prof. Nicholas Samios, Brookhaven National Laboratory
Speaker: Prof. Nicholas Samios, Brookhaven National Laboratory
Title: "Discovery of the Ω1-: 1964 Parity, Neutrinos, Heavy Ions, RBRC: T.D. Lee and Me."
Abstract:
In 1964 the BBC made a video of the discovery of Ω1- . This included interviews with Richard Feynman, Murray Gell-Mann, and myself. An edited version (27 minutes) will be shown. I will then briefly comment on this video. As noted in the title of my talk, I will then proceed to discuss several exciting areas of Physics that T.D. Lee and I had the pleasure of actively participating in and contributing to from 1955 to the present. These include parity violations in weak interactions, use of high energy neutrinos as a probe of weak interactions, the utilization of relativistic heavy ion beams to create a new form of matter sQGP (strongly interacting quark gluon plasma) and the creation of a new center for the study of non-perturbative QCD.
Speaker: Prof. Philip Kim, Columbia University
Title: "Spin and Pseudo-Spin in Graphene"
Abstract:
Graphene, a single atomic layer of graphite, has been provided physicists opportunities to explore an interesting analogy to the relativistic quantum mechanics. The unique electronic band structure of graphene lattice yields a linear energy dispersion relation where the Fermi velocity replaces the role of the speed of light and pseudo spin degree of freedom for the orbital wavefunction replaces the role of real spin in usual Dirac Fermion spectrum. The exotic quantum transport behavior discovered in these materials, such as unusual half-integer quantum Hall effect and Klein tunneling effect, are a direct consequence of the pseudo-spin rotation in graphene. Interacting systems with internal symmetries will tend to break those symmetries in order to lower their energy. In graphene, the strong Coulomb interactions and approximate spin-pseudo spin symmetry are predicted to lead to a variety of quantum Hall ferromagnetic ground states and excitations which manifest as integer quantum Hall plateaus appearing within a graphene. In this presentation I will discuss various experimental evidence support the importance of spin and pseudo-spin structures in graphene at the strong quantum limit.
Speaker: Prof. John Parsons, Columbia University
Title: "News from the LHC: Tightening the Noose on the Standard Model"
Abstract:
With the recent turn-on of CERN's Large Hadron Collider (LHC), particle physics has entered a new era in the exploration of physics at the TeV scale. The LHC, the world's highest energy particle accelerator, has been performing extremely well.The large data sample already recorded by the ATLAS detector at the LHC allows probes of TeV scale physics with unprecedented sensitivity. Recent ATLAS results will be discussed, including the race to discover, or else rule out, the Standard Model Higgs bosonas the origin of mass, as well as searches for new physics beyond the Standard Model.
Speaker: Prof. Tanya Zelevinsky, Columbia University
Title: "Precision Metrology with Ultracold Atoms and Molecules"
Abstract:
We will discuss ongoing and planned measurements with laser-cooled atoms in magneto-optical traps and in optical lattices of various dimensionalities. Progress toward ultracold bi-alkaline-earth molecules and a molecular lattice clock will be presented. We will describe the applications of this research to fundamental physics questions such as dark matter detection and stability of the electron-proton mass ratio.
Speaker: Prof. David Ceperley, University of Illinois at Urbana-Champaign
Title: "The phases of Hydrogen and Helium at High Pressure as revealed by simulations"
Abstract:
Hydrogen and helium account for much of the visible mass in the universe. Their properties are important for understanding the giant planets, Jupiter and Saturn, but experiments under the relevant conditions are challenging. Even though they are the simplest elements in the periodic table, calculating their properties is not simple since they are highly quantum systems. For example, it has long been an open question how hydrogen makes a transition from a molecular insulating state to an atomic metallic state. We have developed new simulation methods starting from “first principles” to treat such systems and using them, have studied molecular dissociation in liquid hydrogen and have observed clear evidence of an “extra” liquid-liquid phase transition for temperatures 600K < T <1500 K. We have performed a “random structure search” to determine the ground-state crystal structures of atomic metallic hydrogen from 500 GPa to 5 TPa. We also examined hydrogen–helium mixtures at Mbar pressures and high temperatures (4000 to 10000 K) and determined the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen: this could explain some of the observed differences between Jupiter and Saturn.
Speaker: Prof. Vladimir Falko, University of Lancaster, England
Title: "Strain-dependent topology of electron bands in bilayer graphene"
Abstract:
Electrons in bilayer graphene exhibit quite unusual properties: they can be viewed as `massive chiral fermions' with parabolic dispersion at intermediate energies and Berry phase 2π, in contrast to monolayer graphene, where electrons are Berry-phase π quasi-particles with linear dispersion. Here, we show that topology of the low-energy band structure of electrons in bilayer graphene critically depends on mechanical deformations of the crystal. Strain is naturally generated in suspended graphene devices, due to motion of the supporting contacts upon cooling, depending on the device geometry or preparation history. Strain determines the number of Dirac cones in the low-energy part of the spectrum, below the saddle point in the electron dispersion: two with the Berry phases in a strongly strained crystal instead of four (three with Berry phase π and one with -π) in an unperturbed crystal. In physics of metals, such change in topology of band structure is known as the Lifshitz transition. These spectral features are tracked down to the evolution of the Landau levels for electrons in a magnetic field and we predict their manifestation in the quantum Hall effect in strained bilayers. Finally, the electron-electron interaction in unperturbed bilayer graphene may lead to a correlated state with a spontaneously broken symmetry. Theoretical analysis based upon the renormalisation group approach which takes into account all possible symmetry-breaking interaction channels shows that the strongest instability in the electronic liquid in bilayer graphene develops into the state with anisotropic interlayer hopping of electrons which mimics the effect of uniaxial strain. As a result, the experimental consequences of the nematic phase transition of electrons would look similar to those of strain, however, in suspended graphene devices these would not depend on the device geometry or preparation history.
Speaker: Prof. Matias Zaldarriaga, Institute for Advanced Study
Title: "Relics from the Bang"
Abstract:
Clues about what led to the hot big bang are encoded in the properties of the structures that can be observed in the late universe. I will summarize what current data tells us and what we might be able to learn in the future. I will speak about the theory behind these observations.
Speaker: Prof. Ozgur Sahin, Columbia University
Title: "Probing Mechanics of Biological Systems"
Abstract:
Biological systems harness mechanical phenomena to serve critical functions on the molecular, cellular, and organismic levels. Beyond the variety in length scales, the mechanical processes are enriched further by the broad range of time scales involved. We will first present experimental methods developed in our group to access forces and displacements on the nanoscale with a temporal resolution around one microsecond. We applied these methods to understand mechanical behavior of biological systems under extremes like short durations, distances, and high pressure levels. We will demonstrate some of the biological imaging methods that have come of this work, as well as new biologically-based approaches to energy conversion from the natural environment.
Speaker: Prof. David Spergel, Princeton University
Title: "The Cosmic Microwave Background as a Probe of the Early Universe and Novel Physics"
Abstract:
Cosmologists are making increasingly accurate measurements of the
microwave background temperature and polarization fluctuations. These
measurements probe both the physics of the very early universe and the
basic properties of the universe today. I will begin by reviewing the
WMAP observations, then describe recent results from the Atacama
Cosmology Telescope and finally look forward to upcoming results from
Planck and upcoming ground based experiments.
These CMB measurements rigorously test our standard cosmological model
and provide an accurate determination of basic cosmological parameters
(the curvature of the universe,its matter density and composition).
When combined with other astronomical measurements, the WMAP
measurements contain the properties of the dark energy and the mass of
the neutrino. The observations also directly probe the physics of
inflation: the current data imply that the primordial fluctuations were
primarily adiabatic
and nearly scale invariant.
Many key cosmological questions remain unanswered: what happened during
the first moments of the big bang? what is the dark energy? what were
the properties of the first stars? I will discuss the role of on-going
and future CMB observations in addressing these key cosmological
questions and describe how the combination of large-scale structure,
supernova and CMB data can be used to address these questions.
Speaker: Prof. Rafael Lang, Purdue University
Title: "Direct Search for Dark Matter"
Abstract:
A colorful variety of experiments attempts to find out what all that Dark Matter in the Universe is made of, resulting in a buzzing field of research. The talk will review what a variety of astrophysical observations tell us (and don't tell us) about the Nature of Dark Matter. The basic principles for the direct detection of Weakly Interacting Massive Particles (WIMPs) in laboratory-scale detectors will be presented. Various experimental techniques will then be explained together with the current status and data from running detectors, as well as prospects for the near future. As will become clear, the direct detection of Dark Matter is in an extremely exciting phase, with realistic prospects to clarify one of the largest mysteries of contemporary physics within the next few years.
Speaker: Dr. Boris Kayser, Fermilab
Title: "Neutrino Oscillation – A Quantum Mechanical Adventure"
Abstract:
Neutrino oscillation, through which we have discovered that neutrinos have nonzero masses, involves quantum mechanics in an essential way. We will present a new treatment of the quantum mechanics of neutrino oscillation, and of neutral particle-antiparticle oscillation, that avoids quantum-mechanical puzzles such as Einstein-Podolsky-Rosen correlations. Then we will review what has been learned from the neutrino oscillation data, including recent news and surprises. We will conclude by commenting on where we go from here, focusing on the search for results that could point to a central role of neutrinos in the creation of the observed matter-antimatter asymmetry of the universe.
Speaker: Prof. Gustaaf Brooijmans, Columbia University
Title: "The Next Step in the Hunt for the Higgs Boson"
Abstract:
From a particle physics point of view, the past thirty years can rightfully be considered as the golden age of the Standard Model. Both the theoretical and experimental knowledge of the structure of the strong and electroweak interactions have reached impressive levels of precision, and the agreement between experimental results and theoretical predictions is stunning. The crucial open question is whether a physical Higgs boson exists. In this colloquium, the reasons a Higgs boson is needed in the Standard Model will be reviewed together with a short history of past searches for evidence for its existence. Then the most recent results obtained at the CERN LHC will be presented, showing how close we are to finally answering this question.