Physics and Astronomy Colloquia

Academic Year 2012-2013

Dept. of Physics & Astronomy, Stony Brook University


Colloquium committee: Meigan Aronson (chair), Leonardo Rastelli, Dominik Schneble, Dmitri Tsybychev, Joanna Kiryluk, Alexandre Abanov, and Alan Calder
Coffee & Tea served at 3:45 pm.
Talk begins at 4:15 pm.
Location: Harriman 137 (bottom of square C4 on the campus map)

Fall 2012 colloquia

DateSpeakerTitleLocal Host
August 28 Abhay Deshpande
SBU
Proton, a laboratory for QCD: Current investigations and future opportunities
It was a remarkable discovery by the Experiments at CERN, SLAC and DESY, in the 1990s that the quarks (+ anti-quarks) contribute only ~30% of the nucleon spin. Where does the remaining spin of the nucleon come from? -- The RHIC Spin program was launched in 2001 to measure that remaining, (and possibly) large contribution from the gluons. It also promised an elegant way to measure the contributions from the anti-quarks. In the last 10 years the RHIC spin program has come of age and is now providing those answers. Not surprisingly there are surprises! The emerging picture of the proton spin structure reflects the the richness of QCD and frames the arguments for future experimental investigations. I will review the recent results from the RHIC Spin program, and present the characteristics and status of the future facility which will be needed to ultimately "solve" the nucleon spin puzzle.

[recorded movie]

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September 4 no colloquium—Labor Day Holliday
September 11 Tom Weinacht
SBU
Quantum Control and Time Resolved Spectroscopy
Intense ultrafast laser pulses can be used to capture and control the motion of atoms and molecules on their natural timescales. In this talk, I will discuss how time resolved spectroscopy can reveal surprising quantum dynamics such as the non-local relaxation of DNA bases exposed to ultraviolet radiation, or the dissociation of a molecule which depends on the phase of its wave function. I will also discuss examples of how shaped laser pulses can control molecular dynamics and lead to new forms of spectroscopy.

[recorded movie]

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September 18 Sriram Shastry
UCSC
A quantitative theory of very strong or extreme correlations
I provide an introduction to the newly developed ideas of extreme correlations. The problem of computing the dynamical response in the hole doped cuprate superconductors is a classic problem of this genre, where existing techniques have been either unreliable or just not powerful enough. The new scheme developed by us provides a quantitative method applicable in the overdoped to optimal doping regimes, and some initital results on photoemission lineshapes and optical conductivity are presented- and prospects for further work discussed.

[recorded movie]

Meigan Aronson
September 25 Christoph Paus
MIT
Unveiling the Mystery of Mass
One of the prime reasons the Large Hadron Collider (LHC) was built is to resolve the question how particles acquire their mass. While it is very simple to measure particle masses and we have a model -- the Standard Model of Particle Physics -- which explains quite accurately all presently available measurements the seemingly trivial mechanism of how particle acquire their mass remains a mystery. The Standard Model invokes a new scalar gauge field to resolve this mystery but we have until very recently not been able to find experimental evidence for its existence. On July 4, 2012, the CMS and ATLAS experiments have announced the discovery of a new Higgs-like particle at a mass of about 125 GeV.

We will review our knowledge about the Higgs boson before the LHC started, quickly touch on the newest from the Tevatron and discuss the discovery in this context. Finally, we will outline the steps required to complete the task and clearly identify the newly discovered particle as the Higgs boson.

[recorded movie]

Dmitri Tsybychev
October 2 Oleg Shpyrko
UCSD
X-ray Nanovision
Attempts to produce focusing x-ray optics date back to the days of Roentgen, however, it was not until the past decade that X-ray Microscopy has finally been able to achieve sub-100 nm resolution. In my talk I will briefly review the history of X-ray Microscopy tools that have been recently applied in a wide range of disciplines, ranging from physics, chemistry and biology to environmental sciences, geophysics and engineering. I will also introduce a novel x-ray microscopy technique developed, which relies on coherent properties of x-ray beams, and eliminates the need for focusing optics altogether, replacing it with a computational algorithm. We have applied this technique to image magnetic stripe domains in GdFe multilayer films, as well as to image the distribution of lattice strain in nanostructures. I will discuss applications of these novel x-ray imaging methods in context of new generation of fully coherent x-ray sources.

[recorded movie]

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October 9 Jim Misewich
Brookhaven National Laboratory
Low Dimensional Heterostructures and Control of Energy Pathways
Reduced dimensional materials, such as graphene, nanowires, and quantum dots, exhibit distinct and potentially useful physical properties. For example, quantum confinement effects in semiconductor nanoparticles can enhance exciton fission under appropriate conditions. Although exciton fission provides an intriguing possibility to transcend the Shockley-Queisser solar conversion efficiency limit, the issue of electron-hole separation and transport before recombination remains a challenge. In this talk we will examine some of the distinct transport and optical properties of low-dimensional materials and present recent data on 0d-1d heterostructures that offer a pathway for rapid exciton dissociation and transport.

[recorded movie]

Laszlo Mihaly
October 16 Sidney Nagel
University of Chicago
Jamming as the epitome of disorder
Solids always have some structural disorder. Yet we are customarily taught to understand solids by first considering the physics of perfectly ordered crystals. This may be an acceptable approach when a crystal has only a few defects but becomes increasingly untenable as the amount of disorder increases. For a glass, with no well-defined long-range order, a crystal is a terrible starting place for understanding the existence of the glass’s rigidity or its excitations. Is there an alternative – the opposite of a crystal – where order, rather than disorder is the perturbation? Jamming, as opposed to crystallization, is an alternate way of creating a rigid structure. It is an alternate paradigm for thinking about how many different types of fluids - from molecular liquids to macroscopic granular matter - develop rigidity. In contrast to crystals, at the jamming transition, the jammed solid is the epitome of disorder in that there exists no length scale over which one can do an appropriate average to recover the elastic constants.  At zero temperature, the jammed solid has a new class of normal-mode vibrations that dominates the low-frequency excitations. We have found that the properties of the jammed solid are highly unusual and provide a new way of thinking about disordered systems generally.  

[recorded movie]

Phil Allen
October 23 Alan Calder
SBU
Theory and Models of Type Ia Supernovae
Supernovae are spectacular explosions that signal the violent death of a star. Supernovae produce and disseminate heavy elements, trigger star formation, and in some cases may be used as distance indicators for cosmological studies. These fascinating events encompass a broad range of physics, and realistically modeling these requires the largest supercomputers. I will give an overview of supernovae and our theoretical understanding of these events and present results from our research into type Ia (thermonuclear) supernovae. Our models and statistical framework allow the systematic study of how properties of the host galaxy can influence the brightness of an event. I will present the results from ensembles of simulations addressing the influence of age and metallicity on the brightness of an event and compare our results to observed trends in brightness with age and composition of the host galaxy.

[recorded movie]

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October 30 CANCELED DUE TO STORM Lars Bildsten
UCSB
Diverse Energy Sources for Stellar Explosions
The theoretical community is beginning to appreciate (and predict) the potential diversity of explosive outcomes from stellar evolution while the supernovae surveys are finding new kinds of stellar explosions. I will speak about two new energetic mechanisms. The first is our recent work highlighting the importance of late-time energy deposition from rapidly rotating, highly magnetized neutron stars: magnetars. This provides a plausible explanation for those ultraluminous core collapse supernovae with radiated energies approaching 1e51 ergs. I will close with our theoretical work on helium shell detonations on accreting white dwarfs that predict a new class of supernovae; called ".Ia's". The first such candidate may well have been found by the Palomar Transient Factory. These helium detonations may also provide a new path to the ignition of Type Ia supernovae.
Alan Calder
November 6 Martin Savage
University of Washington
Nuclear Forces from Quantum Chromodynamics
A century of coherent experimental and theoretical investigations have uncovered the laws of nature that underly nuclear physics. Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED), both quantum field theories with a small number of precisely constrained input parameters, dominate the dynamics of the quarks and gluons - the underlying building blocks of protons, neutrons, and nuclei. While the analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they encounter difficulties when applied to low-energy nuclear structure and reactions, and dense systems. Expected increases in computational resources into the Exa-scale during the next decade will provide the ability to numerically compute a range of important strong interaction processes directly from QCD with quantifiable uncertainties using the technique of Lattice QCD. In this presentation, I will discuss the state-of-the-art Lattice QCD calculations of quantities of interest in nuclear physics, progress that is expected in the near future, and the expected impact on nuclear physics.

[recorded movie]

Joanna Kiryluk
November 13 Derek Teaney
SBU
The Quark-Gluon Plasma in Experiment and Asymptopia
I will first review the experimental evidence for the Quark-Gluon Plasma in heavy ion collisions with a focus on the observed collective flow and hydrodynamic simulations of this macroscopic response. After this review, I will describe efforts to understand these experimental results using weak coupling ideas from non-abelian plasma physics, and strong coupling ideas from the AdS/CFT correspondence.
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November 20 Krishna Kumar
University of Massachusetts
Electrons are not Ambidextrous: New Insights from a Subatomic Matter of Fact
For a little over a hundred years, subatomic forces in Nature have been studied by bombarding fast moving elementary particles on quasi-stationary nuclear matter. The most precise and detailed information on fundamental forces and the size and shapes of atomic nuclei and their constituents have come from using accelerated electron beams. Over the past thirty years, significant new discoveries about subatomic matter have been made by exploiting an intrinsic quantum property of elementary particles known as "spin", which manifests itself as a left- or right-handedness when particles move at relativistic speeds. There is a tiny difference (of order parts per million) between the probabilities for scattering left- and right-handed electrons off subatomic matter, which can be used to gain unique new insights into the size of nuclei, the nature of constituent quarks as well as those that bubble in and out of existence inside protons and neutrons, and to search for new forces that might have shaped the evolution of the early universe. I will describe the experimental technique to measure the tiny left-right probability difference in electron scattering, report on the nuclear and particle physics implications of recent measurements, and motivate the need for new and more precise experiments.

[recorded movie]

Joana Kiryluk
November 27 Marivi Fernandez-Serra
SBU
Quantum mechanics in the anomalous properties of water
Surprising as it might seem, the understanding of the structure of liquid water is still an open subject, one that has kept theorists and experimentalists busy for the last 50 years. One of the reasons for this is the fact that water is a liquid with a large number of thermodynamical anomalies, and no single theoretical model is capable of explaining them all, or of reproducing all experimental measurements conducted to probe its structure. Advanced computational modeling needs to be developed to simulate the structure and dynamics of liquid water. I will show how recent advances within the framework of density functional theory have allowed us to to understand the physics behind some of the anomalies of water. In all cases, we need to invoke quantum mechanics to explain why water is such a complex liquid. I will show how van der Waals interactions are the main reason why ice floats in water, and how nuclear zero-point effects play an important role in the structure of water.

[recorded movie]

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December 4 Barton Zwiebach
MIT
Einstein's gravity versus String Gravity
Gravity in string theory is a generalized version of Einstein's theory with some universal features that call for a reformulation of the key geometrical concepts. For example, In addition to the metric tensor, string theory contains an antisymmetric tensor and a dilaton that allow for extra symmetries. A new branch of mathematics, Generalized Geometry, suggests a framework that finds a realization in the recent Double Field Theory formulation of string gravity. I will describe the main ideas, the progress, and the mysteries that remain in the search for a proper description of string gravitation.

[recorded movie]

Leonardo Rastelli

 

 

 

 

Spring 2013 colloquia

DateSpeakerTitleLocal Host
Jan. 29 Laszlo Mihaly
Stony Brook
Chair's Colloquium
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Feb. 5 Chandra Varma
University of California, Riverside
Higgs Bosons in Superconductors
Spurred by some strange experimental observations in some superconductors, the theory of a new collective mode in superconductors and how it can be experimentally found very easily under certain circumstances was provided in 1981. It was called the .Amplitude Mode. to distinguish it from the .Phase Modes. which provide Josephson e.ects and which in homogeneous superconductors are at the energies of plasmons. Nambu and Higgs pointed out that the amplitude mode is really the Higgs mode of a U (1) .eld coupled to fermions, i.e the model treated by Higgs and others in 1964. Recently the amplitude or Higgs mode is also discovered in the cuprate superconductors, where its various cousins may also be found. I will tell the story of the above and related developments as well as comment, as a very interested outsider and an enthusiast, on the Higgs being discovered at LHC from the point of view of the Higgs in superconductors and the phenemenology as well as the microscopic theory of superconductivity.

[recorded movie]

Meigan Aronson
Feb. 12 Tom Crawford
Chicago
Probing Fundamental Physics with the Oldest Light in the Universe
Since the discovery of the cosmic microwave background (CMB) in 1965, CMB measurements have been a cornerstone of our standard cosmological model, providing key support for the Hot Big Bang model, demonstrating the need for dark matter, and showing that the universe is spatially flat. We are now entering an era in which measurements of the small-scale temperature anisotropy and the polarization anisotropy of the CMB can go beyond constraining the standard Lambda-CDM cosmological model and shed light on fundamental physical quantities such as the number and mass of relativistic species and the energy scale of inflation. I will focus on recent results from, and future prospects for, the 10-meter South Pole Telescope (SPT). Results from the recently completed 2500 square-degree SPT-SZ survey provide intriguing hints of effects beyond the standard cosmological paradigm and, in conjunction with geometrical probes such as Supernovae Ia, have the power to test General Relativity. The newly installed polarimeter on the SPT is delivering data that should provide unprecedently tight constraints on the mass of the neutrinos and an upper limit on (or even detection of) the inflationary gravity-wave background (and hence the energy scale of inflation). Future upgrades to the instrument will result in yet more constraining power and new discoveries.

[recorded movie]

Alan Calder
Feb. 19 Matt Dawber
SBU
Building new ferroelectric materials layer by layer
One approach to developing the functional materials of the future is to build them up layer by layer using deposition techniques that allow control of thickness on the scale of angstroms. In my laboratory we use this approach to design artificial superlattice structures based on ferroelectric perovskite oxides in which the competing behaviors of the parent materials we use interact in just the right way to produce new or enhanced functional responses. Comprehensive experiments in our laboratory and at synchrotron x-ray facilities then close the loop between structure and functional properties. Within a relatively small class of parent materials we have demonstrated that this approach can be used to engineer quite different behaviors, from improper ferroelectricity, to polarization rotation, to self poled ferroelectrics with anisotropic transport. When we build materials layer by layer the whole can truly be greater than the sum of the parts.

[recorded movie]

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Feb. 26 Alex Kamenev
University of Minnesota
Dynamics of mobile impurities in superfluids
Motion of external particles in a superfluid environment is an old subject, which attracted attention of many great physicists. I will review parts of this history and focus on recent experiments performed with cold atomic condensates. These novel superfluids made possible to investigate motion of impurities in one-dimensional quantum liquids. It allowed to address some subtle issues associated with exact integrability, Josephson physics, Casimir effect, etc.

[recorded movie]

Sasha Abanov
Mar. 5 Andrei Nomerotski
BNL
Fast imaging : from galloping horses to celestial cinematography with LSST
We will review recent advances in science enabled by rapid progress in time resolved imaging. Examples will include two extremes: imaging mass spectrometry with demand of 1 ns resolution and Large Synoptic Survey Telescope, which will be imaging half of the Universe every three days for ten years unveiling mysteries of Dark Energy and Dark Matter.
Dmitri Tsybychev
Mar. 12 Laszlo Mihaly
Stony Brook
Chair's Colloquium
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Mar. 19 no colloquium—Spring Break
Mar. 26 Francis Halzen
Wisconsin
Particle Astrophysics with High Energy Neutrinos
Construction and commissioning of the cubic-kilometer IceCube neutrino detector and its low energy extension DeepCore have been completed. The instrument detects neutrinos over a wide energy range: from 10 GeV atmospheric neutrinos to 1010 GeV cosmogenic neutrinos. We will discuss initial results based on a subsample of the more than 300,000 neutrino events recorded during construction. We will emphasize the measurement of the atmospheric neutrino spectrum, the search for the still enigmatic sources of the Galactic and extragalactic cosmic rays, and for the particle nature of dark matter. We will also discuss the first observation of PeV-energy neutrinos.
Joanna Kiryluk
Apr. 2 Michael Peskin
SLAC
Beyond the Higgs Boson: What have we learned about Particle Physics from the Large Hadron Collider?
The big news from particle physics in 2012 was the discovery at the CERN Large Hadron Collider of a new particle with many properties of the long-sought Higgs Boson. The Higgs Boson had been predicted by the unified theory of weak and electromagnetic interactions, so, potentially, this discovery fills a recognized gap in our understanding. But there are more mysteries about weak interactions and physics at the 100 GeV - 1 TeV mass scale. About these, the LHC has also given us much information, but all of it negative, exclusions of previously possible solutions. In this lecture, I will give my best understanding of where we are in the search for new particles and forces related to the weak interaction. I will review the questions we are asking about physics in the hundred GeV region. I will discuss the power and also the difficulties of LHC measurements. There are many alternatives for the route forward. I will discuss three of these and their implications for the future of particle physics.
Dmitri Tsybychev
Apr. 9 Andreas Karch
University of Washington
Recent Progress in Applications of the Gauge/Gravity Correspondence
I'll give a brief overview of the basic philosophy behind applying the gauge/gravity correspondence (or holography for short) to problems in nuclear and condensed matter physics. Recent progress regarding viscosities, energy loss, non-Landau phase transitions and non-Fermi liquids will be reviewed.
Leonardo Rastelli
Apr. 16 Giorgio Gratta
Stanford
EXO and the quest for Majorana Neutrino Masses
With the definitive evidence for neutrino oscillations collected in the last decade, we now believe that neutrino masses are non-zero. Oscillation measurements, however, only measure mass differences and give us little information about the absolute values of neutrino masses. The hypothetical phenomenon of neutrino-less double-beta decay can probe the neutrino mass scale with exquisite sensitivity. This process, if observed, would also imply that neutrinos, unlike all other spin-1/2 particles, have only two component wave functions and that lepton number is not a conserved quantity. Following the well known principle that there is no free lunch in life, interesting half-lives for neutrino-less double-beta decay exceed 10^25 years (or ~10^15 times the age of the Universe) making experiments rather challenging. I will describe the EXO program that is developing the tools to search for this rare decay and discuss the recent measurements by EXO-200 that recently discovered the 2-neutrino double-beta decay in 136Xe and substantially improved the limit on Majorana neutrino masses.
Joanna Kiryluk
Apr. 23 Jun Ye
JILA / Univ. of Colorado Boulder
Ultracold molecules - New frontiers in quantum & chemical physics
Molecules cooled to ultralow temperatures provide fundamental new insights to molecular interaction dynamics in the quantum regime. In recent years, researchers from various scientific disciplines such as atomic, optical, and condensed matter physics, physical chemistry, and quantum science have started working together to explore many emergent research topics related to cold molecules, including cold chemistry, strongly correlated quantum systems, novel quantum phases, and precision measurement. Complete control of molecular interactions by producing a molecular gas at very low entropy and near absolute zero has long been hindered by their complex energy level structure. We have recently developed a number of technical tools to laser cool and magneto-optically trap polar molecules, as well as to cool molecules via evaporation. Another recent experiment has brought polar molecules into the quantum regime, in which ultracold molecular collisions and chemical reactions must be described fully quantum mechanically. We control chemical reaction via quantum statistics of the molecules, along with their long-range and anisotropic dipolar interactions. Further, molecules can be confined in reduced spatial dimensions and their interactions are precisely manipulated via external electric fields. Those efforts have started to yield observations on strongly interacting and collective quantum effects in an ultracold gas of molecules.
Dominik Schneble
Apr. 30 Randall G. Hulet
Rice University
Quantum Simulation with Atoms in Optical Lattices
Some of the most complex and vexing problems in electronic materials are modeled by extremely simple Hamiltonians. High-temperature superconductors, for example, may arise from magnetic interactions in a Mott insulating state, described by the simple Hubbard model. The Hubbard model stipulates that particles (electrons in the case of superconductors) are distributed in a square lattice where they can hop from site to site with a tunneling energy t, and where they may interact with occupied nearest neighbor sites with interaction energy U. No one knows whether this simple “hydrogen-atom” model actually gives rise to the d-wave pairing underlying the cuprate superconductors, as the model, while simple to describe, is not solvable using digital computers. I will discuss two experiments that use ultracold atoms in an optical lattice as stand-ins for the electrons in ionic lattices: 1) the Hubbard model in 3D; and 2) the polarized spin-½ Fermi gas in 1D. In the first experiment, we are searching for the anti-ferromagnetic Mott insulating state that is expected to exist above the superconducting transition when there is exactly one-atom per lattice site. We have used Bragg scattering of near-resonant light to characterize the lattice, and will use a spin-sensitive variant of this tool to detect magnetic correlations. In the second experiment, we have used an optical lattice in two-dimensions to create a bundle of 1D tubes containing an imbalanced two spin-state mixture of 6Li fermions. The phase diagram of this system contains three phases: a fully-paired superfluid, a fully-polarized ferromagnet, and a partially polarized state that is predicted to be the exotic FFLO superfluid state, for which the pairs have non-zero center of mass momentum.
Schneble/Abanov
May 7 graduate director
Graduate Awards Colloquium
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