Physics and Astronomy Colloquia

Academic Year 2011-2012

Dept. of Physics & Astronomy, Stony Brook University


Colloquium committee: Meigan Aronson (spring chair), Axel Drees, Leonardo Rastelli, Dominik Schneble, Dmitri Tsybychev, Michael Zingale (fall chair)
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 2011 colloquia

(colloquia already given are listed here)

DateSpeakerTitleLocal Host
Sept. 6 Laszlo Mihaly
Stony Brook
Chair's Colloquium

[slides]

[recorded movie]

-
Sept. 13 Chang Kee Jung
Stony Brook
T2K Experiment: Negotiating the Gatekeeper of the Matter-Antimatter Asymmetry Mystery
Matter-antimatter asymmetry is one of the most outstanding mysteries of the universe that provided a necessary condition to our own existence. There have been various attempts to solve this mystery including 'Baryogenesis' hypothesis. However, the B-factory experiments during the last decades showed that the observed CP-violation in the quark sector is not big enough for baryogenesis to be a viable solution to the matter-antimatter asymmetry. This leads us to the 'Leptogenesis' hypothesis, in which CP-violation in the lepton section plays a crtical role to create the matter-antimater asymmetry at the onset of the Big Bang. Thus, experimental observation of CP-violation in the lepton sector could prove to be tantamount to one of the most important discoveries in our understanding of the universe.

Recently the T2K experiment published a result that indicates a non-zero θ13, the last unknown mixing angle in the lepton sector, at 2.5 sigma level of significance. In this talk I will present the details of this result and its importance to the possible future CP-violation measurements in the lepton sector. I will also describe the T2K experiment in some detail, and present other recent results.

[recorded movie]

Zingale
Sept. 20 Jiangyong Jia
Stony Brook
Sound of "little-bangs" measured by the ATLAS experiment at the LHC
I present recent ATLAS measurements of the harmonic flow--Fourier components of the azimuthal momentum anisotropy of particle production -- in "little bangs" of lead ions colliding at 1370 times of their rest mass energy, made possible by the Large Hadron Collider. I show how the amplitudes of the harmonic flow provide unprecedented insights on the initial density fluctuation and subsequent hydrodynamic evolution of the hot dense fireball created after the collision. I discuss some interesting connections to examples in other fields of physics.

[recorded movie]

Drees
Sept. 27 George Redlinger
BNL
Higgs and SUSY Searches at the LHC
While the Standard Model of particle physics has enjoyed remarkable success in matching the results of observations to ever greater precision, one prediction that is so far unconfirmed is the existence of the Higgs boson which breaks the electroweak symmetry. Furthermore, despite its success, the Standard Model suffers from a number of shortcomings. Supersymmetry is one of the leading candidates for physics beyond the Standard Model that potentially overcomes these shortcomings and provides a consistent picture of particle physics all the way up to Grand Unification energies. This talk will review the current status of searches for the Higgs boson and supersymmetry with the ATLAS experiment at the LHC.

[recorded movie]

Tsybychev
Oct. 4 Hirosi Ooguri
Caltech
Gravity's Hologram
At the Planck scale, where general relativity and quantum mechanics are unified, the hierarchical structure of nature is expected to terminate. Space and time do not exist beyond the Planck scale, and they should emerge from something more fundamental. Superstring theory has provided an insight into the emergence of space and time at the Planck scale. Hologram is a term in optics, and it means encoding geometric data of a 3-dimensional object on a 2-dimensional surface so that the 3-dimensional image can be reconstructed later. In superstring theory, all the phenomena in quantum gravity can be projected onto a screen located at boundaries of space, and they can be described using a quantum theory without gravity on the screen. Borrowing the terminology of optics, this idea is called gravity's hologram. I will discuss motivations and implications of this new description of quantum theory of gravity.

[recorded movie]

Rastelli
Oct. 11 Ivan Bozovic
BNL
Peeling high-Tc superconductivity - one atomic layer at a time
Using a unique molecular beam epitaxy system we synthesize digitally (atomic-layer-by-layer) thin films, multilayers and superlattices of cuprates and other complex oxides. The constituent layers can be just one-unit-cell thick and the interfaces atomically perfect. Various heterostructures are designed to enable novel experiments that probe the basic physics of high-temperature superconductivity (HTS). In this talk, I will review our recent experiments on such films and superlattices. Some key questions in HTS physics -- about the dimensionality, relevant interactions, the roles of (in)homogeneity and fluctuations -- are answered as follows.
  1. In an isolated single CuO2 plane without holes, quantum spin liquid forms.1
  2. In a single CuO2 plane doped with holes, HTS can occur with Tc even higher than in the bulk.2
  3. HTS cuprate samples can have a very sharp and uniform SC gap.3
  4. HTS and anti-ferromagnetic phases separate on the scale of 1 Å in space and 1 eV in energy.1,4
  5. Pseudo-gap state mixes with the SC state on the 1,000 Å length scale ("Giant Proximity Effect")5
  6. In-plane charge excitations are strongly coupled to out-of-plane lattice vibrations.6
  7. Local pairs and vortices exist on the insulating side of the S-I quantum phase transition.7
  8. Strong phase fluctuations drive the SC transition, but 10-15 K above Tc they fade out.7

1 Suter et al., PRL 106, 237003 (2011).
2 Bozovic et al., PRL 89, 107001 (2002); Gozar et al., Nature 455, 782 (2008); Smadici et al., PRL 102, 107004 (2009), Logvenov et al., Science 326, 699 (2009), Butko et al., Adv. Mater. 21, 1 (2009), Zhou et al., PNAS 107, 8103 (2010).
3 Abbamonte et al., Science 297, 581 (2002); Shim et al., PRL 101, 247004 (2008).
4 Bozovic et al., Nature 422, 873 (2003).
5 Bozovic et al., PRL 93, 157002 (2004); Morenzoni et al., Nature Comm. 2, 272 (2011).
6 Gedik et al., Science 316, 425 (2007); Radovic et al., PRB 77, 092508 (2008)
7 Sochnikov et al., Nature Nanotech. 5, 516 (2010); Bilbro et al., Nature Physics (2011); Bollinger et al., Nature 472, 458 (2011).

[recorded movie]

Aronson
Oct. 18 Rick Van Kooten
Indiana
The Legacy of Run II of the Tevatron and Outstanding Anomalies
The Tevatron, the world's highest-energy proton-antiproton collider, shut down on Sept. 30, 2011. The Tevatron has informed some of the most important fundamental discoveries of our time, refined the Standard Model of particle physics, and shaped our understanding of matter, energy, space and time. The Run II program started in 2001 and highlights and milestones of the physics results since then will be described. An overview will be made of remaining significant discrepancies from Standard Model predictions, focusing on an anomalously large like-sign dimuon charge asymmetry observed by the D0 Collaboration that may be indicating a potential new source of CP violation beyond the Standard Model. The technique of using neutral meson particle-antiparticle oscillations to explore this CP violation is described and the measurement presented. Intriguing indications of a similar effect in separate analyses are shown as well as more far-fetched implications on CPT/Lorentz violation.

[recorded movie]

Tsybychev
Oct. 25 Christian Ott
Caltech
Stellar Collapse, Core-Collapse Supernovae, and the Formation of Stellar-Mass Black Holes
Core-collapse supernovae from massive stars are among the most energetic events in the universe. They liberate a mass-energy equivalent of ~15% of a solar mass in the collapse of their progenitor star's core. The majority (99%) of this energy is carried away by neutrinos, while (~1%) is transferred to the kinetic energy of the explosive outflow. A smaller, yet still tremendous amount of energy is emitted in electromagnetic and gravitational waves. Core-collapse supernovae are the birth sites of neutron stars and stellar-mass black holes; their explosions seed the universe with the ashes of nuclear burning from which planets form and life can spring.

I review our current understanding of core-collapse supernovae and discuss recent progress made and insight gained from new multi-dimensional computational models. These models are yielding new predictions for the signature of core-collapse supernovae in neutrinos and gravitational waves and I delineate how their observation from the next nearby core collapse event can shed light onto this still mysterious phenomenon.

[recorded movie]

Zingale
Nov. 1 Luis Orozco
Maryland
What we know about Francium
Francium is the heaviest alkali atom. There is much less than an ounce of francium at any given time in the whole Earth. It is the most unstable element of the first 103 in the periodic table, and its longest lived isotope lasts 20 minutes. Its atomic and nuclear structure makes it an ideal laboratory to study the weak interaction. Laser trapping and cooling in line with the superconducting LINAC accelerator at Stony Brook has opened the precision study of its atomic structure and will allow parity nonconservation measurements on its electronic levels. I will present our proposal and progress towards a measurement at TRIUMF, the National Canadian Accelerator in Vancouver, of the nuclear anapole moment in a chain of francium isotopes through parity non-conserving transitions in the ground state hyperfine manifold. These measurements should shed light on the nucleon-nucleon weak interaction.

Supported by NSF and DOE of the USA and NRSEC of Canada.

[recorded movie]

Schneble
Nov. 8 Matt Strassler
Rutgers
Searching for Answers at The Large Hadron Collider
The Large Hadron Collider (LHC), the world's most powerful particle accelerator, has had a very successful year, collecting more than 100 times as much data as it did in its pilot run in 2010. The data is sufficient to allow particle physicists to begin addressing some long-standing profound questions about nature. In this talk I will introduce the LHC as a machine and as an enterprise, and explain briefly how science is done there. After outlining the profound questions that the LHC was meant to explore, I will provide a progress report on what has been learned this year, as well as describing the long road that lies ahead.
Rastelli
Nov. 15 Rouven Essig
Stony Brook
The Hunt for Dark Matter
Dark matter makes up 80% of the matter in our Universe, but we have yet to learn its identity. Astrophysical probes are becoming powerful enough to inform us on some of its fundamental properties and a wide array of experiments are probing its non-gravitational interactions with ordinary matter. In this talk, I will review the astrophysical evidence for dark matter and give a broad overview of current and future direct and indirect detection experiments, as well as collider probes. I will also discuss the implications for the properties of the dark matter particle if some of the available data and hints for dark matter at currently running experiments survive further scrutiny.

[recorded movie]

Zingale
Nov. 22 no colloquium—classes on a Thurs. schedule
Nov. 29 Meg Urry
Yale
The Growth of Supermassive Black Holes and Their Co-Evolution with Galaxies
Deep multi-wavelength surveys undertaken over the past decade have allowed us to trace the history of the growth of supermassive black holes at the centers of galaxies, out to very large distances (i.e., over much of the past ~12 billion years). We refer to these growing black holes as "active galactic nuclei," or AGN. We now know that most of this growth is heavily obscured by gas and dust, so most AGN are not visible in optical surveys. Instead, they are easily found with X-ray imaging. We also find that obscured AGN are more common in the young Universe and in low-luminosity AGN. Understanding where and when black holes grow allows us to address theorists' scenarios for "AGN feedback," a process whereby black hole growth releases energy that quenches star formation in the surrounding galaxy. By studying the host galaxies of AGN, we see evidence at that AGN at the epoch of peak black hole growth may indeed help quench star formation, even though in the local Universe, they do not (locally, star formation appears to turn off well before AGN reach their peak brightness). Finally, we find an intriguing dependence of AGN activity on host galaxy morphology. Most host galaxies are disk dominated and their black holes are not growing rapidly. These results suggest that, contrary to some popular theories, major mergers are not the way most galaxies acquire mass over cosmic time, nor do they induce the bulk of black hole growth.

[recorded movie]

Zingale
Dec. 6 Simon Mochrie
Yale
X-ray specs: How a liquid becomes a glass on heating and on cooling and other stories

[recorded movie]

Stephens

Spring 2012 colloquia

(colloquia already given are listed here)

DateSpeakerTitleLocal Host
Jan. 24 Emilio Mendez
BNL
Nanotechnology and the Energy Challenge
Since 1973—the year of the first major oil crisis—the world's energy consumption has doubled, but the portion of fossil fuels has barely changed. In 2008, 81% of the energy used still came from a combination of oil, coal, and natural gas. This large dependence on fossil fuels presents one of the world's biggest challenges because the earth's reserves are limited; their uneven distribution exarcebates geopolitical problems; and, most urgently, fossil-fuel burning is the main source of greenhouse gases that affect climate change. The answer to this challenge goes from reducing energy consumption and increasing efficiency to developing economical alternative sources.

In this talk, I will focus on the role that nanotechnology can play in addressing the energy challenge. In particular, I will concentrate on the research being conducted at the Center for Functional Nanomaterials (CFN) on novel materials and structures for catalysis, photovoltaics, and energy storage, and on the state-of-the-art facilities that make that research possible.

The CFN is one of the five Nanoscale Science Research Centers (NSRCs), distributed across the US and created by the Department of Energy to serve as hubs of nanoscience research with advanced facilities open to the scientific and technological communities. The NSRCs are part of the National Nanotechnology Initiative, launched by the US government in 2000 to capitalize on the enormous potential that nanoscience and nanotechnology offer to address major societal problems.

[recorded movie]

Aronson
Jan. 31 Eugenie Reich
Science Journalist
Fraud in Physics: The Schon Affair at Bell Labs
In 2002, physicists were shocked to learn that a staff physicist at Bell Labs in New Jersey, Jan Hendrik Schon, had faked numerous experiments reported on in top journals. In this talk I give an analysis of the case arising from the interviews and documents I obtained for my 2009 book, "Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World". In the talk I will describe Schon's first few manipulations of data as a graduate student at the University of Konstanz, and the escalation of his fraudulent claims in the environment of Bell Laboratories. I also describe how his papers were handled by editors at the journals Nature and Science
Aronson
Feb. 7 Igor Klebanov
Princeton
String theory and the Strong Interactions
String theory was originally invented to describe hadrons, but Quantum Chromodynamics (QCD) has 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 discuss applications of these ideas to theories at finite temperatures and to theories which exhibit color confinement. I will also cover some of the recent progress, including calculation of the quantum entanglement entropy and formulation of exact gauge/gravity dualities involving Chern-Simons theories. I will tie these ideas to the "F-theorem" recently conjectured for quantum field theories in three space-time dimensions.

[recorded movie]

Rastelli
Feb. 14 Subir Sachdev
Harvard
Quantum entanglement and the phases of matter
In many modern materials, electrons quantum-entangle with each other across long distances, and produce new phases of matter, such as high temperature superconductors. We face the challenge of describing the entanglement of 10^{23} electrons, which is being being met by many ideas. A promising recent approach uses string theory. This theory was originally constructed as a unification of the quantum field theory of elementary particles with Einstein's theory of gravitation. Unexpectedly, the "dualities" of string theory have given us a new perspective on long-range entanglement in quantum models which describe electrons in modern materials in easily accessible laboratory environments.
Rastelli
Feb. 21 Lars Hernquist
Harvard
Cosmology on a Moving Mesh
Understanding the formation and evolution of galaxies in a cosmological context using numerical simulations remains an elusive goal. In this talk, I describe a new approach to modeling the hydrodynamics of galaxy formation in which the equations of motion are solved on a moving mesh. The use of a moving mesh makes the scheme fully Lagrangian, unlike popular particle-based codes which are quasi-Lagrangian in nature, and mitigates against advection errors when a spatially fixed grid is used. I present results from an initial study comparing results for a moving mesh with those obtained using a smoothed particle hydrodynamics solver. This preliminary work suggests that the new approach offers promise for resolving the long-standing problems which have plagued this field for nearly two decades.

[recorded movie]

Zingale
Feb. 28 Wolfgang Ketterle
MIT
Superfluid gases near absolute zero temperature
What is the benefit of realizing superfluidity in a gas a million times more dilute than air? Such systems consist of well-separated atoms which can be observed and manipulated with the control and precision of atomic physics, and which can be treated with first-principles calculations. One such form of superfluidity occurs when a gas of bosons undergoes Bose-Einstein condensation (BEC). A richer situation is realized with ultracold fermions. Fermions have to form pairs before they can become superfluid. By continuously changing the interaction strength using a scattering resonance we were able to study superfluidity for varying pair size, connecting the BEC limit with the case of BCS Cooper pairs, which are larger than the interatomic spacing. These studies illustrate a new approach to condensed-matter physics where many-body phenomena are realized in dilute atomic gases

[recorded movie]

Schneble
Mar. 6 Vivien Zapf
Los Alamos
Magneto-electric coupling in organo-metallic materials
There is a vast world-wide effort underway to discover new materials where magnetization couples to electric polarization and vice versa. The goal is to create devices with important functionalities, for example to couple the spins in ‘spintronics’ with conventional circuits based on electrical charge, to create new kinds of hybrid magnetic-electric memories that overcome existing Moore’s law limitations, to design very sensitive solid-state magnetic sensors, etc. Thus there is both a scientific challenge to find new magneto-electric coupling mechanisms, and a materials challenge to discover new classes of compounds that can exhibit them. Here we present some of the first examples of magneto-electric coupling in organo-metallics. Organo-metallics are single crystalline solids that contain magnetic transition-metal ions and organic ligands that can be electrically polarizable. The crystal structures can be quite complex, and most importantly, flexible for design. We explore coupling mechanisms based on non-coplanar arrangements of spins that break the necessary symmetries to couple to electric polarization.

[recorded movie]

Aronson
Mar. 13 Chris Jacobsen
Northwestern/Argonne
X-ray imaging in real life
Hierarchical structures fill our body, our planet, and our devices. X-rays provide a unique tool to image this hierarchy: they can penetrate into real materials and environments, they can reveal trace elements, and they can measure chemical states and crystalline lattice rearrangements. There are interesting problems over many time and length scales, ranging from watching explosives at work to understanding the dynamics of zinc in oocyte fertilization. Future directions in nanoscale imaging look towards complexity: that of a material's environment, and that of the data, so that one can learn from x-ray imaging in real life.

[recorded movie]

Stephens
Mar. 20 Mark Newman
Michigan
Epidemics, Erdos numbers, and the Internet: The physics of networks
There are networks in almost every part of our lives. Some of them are familiar and obvious: the Internet, the power grid, the road network. Others are less obvious but just as important. The patterns of friendships or acquaintances between people form a social network; the species in an ecosystem join together to form a food web; the workings of the body's cells are dictated by a metabolic network of chemical reactions. As large-scale data on these networks and others have become available in the last few years, a new science of networks has grown up, drawing on ideas from physics, math, computer science, biology, and other fields to shed light on systems ranging from bacteria to the whole of human society. This talk will examine some new discoveries regarding networks, how those discoveries were made, and what they can tell us about the way the world works.

[recorded movie]

Aronson
Mar. 27 Natalie Batalha
San Jose State
Kepler's Year-Three Transit Census
Humankind's speculation about the existence of other worlds like our own turned into a veritable quest with the launch of NASA's Kepler spacecraft in March 2009. The mission is designed to survey a slice of the Milky Way Galaxy to identify planets via transit photometry. The last year of science operation has been a year of milestones in terms of exoplanet characterization: rocky, Earth-size, circumbinary, Habitable Zone, and even invisible planets have made headlines. However, the real work lies in the large sample statistics of the catalogs of viable planet candidates -- statistics that will drive us toward a determination of eta-earth. The Kepler team recently released its third catalog, consisting of 2,321 viable candidates associated with 1,790 stars. Dr. Batalha will describe some of the milestone discoveries that have marked the last year, the make-up of the new catalog, and the strategies moving forward. Now entering its fourth year of operation, Kepler is honing in on the answer to the question that drives the mission: are potentially habitable worlds abundant in our galaxy.
Zingale
Apr. 3 no colloquium—Spring Break
Apr. 10 Chris Monroe
JQI/Maryland
Quantum Networks of Trapped Atomic Ions
Trapped atomic ions are standards for quantum information processing, with each atom storing a quantum bit (qubit) of information in appropriate internal electronic states. The Coulomb interaction mediates entangling quantum gate operations through the collective motion of the ion crystal, which can be driven through state-dependent optical dipole forces. Scaling to larger numbers of trapped ion qubits can be accomplished by either physically shuttling the individual atoms through advanced microfabricated ion trap structures or alternatively by mapping atomic qubits onto photons for the entanglement over remote distances. Such a quantum network will have impacts on quantum information processing, quantum simulation of models from condensed matter, quantum communication, and the quest for building ever larger entangled quantum states and perhaps entangling atoms with other physical platforms such as quantum dots or macroscopic mechanical systems. Work on these fronts will be reported, including quantum simulations of magnetism with N=16 atomic qubits and the uses of entanglement of matter over macroscopic distances.
Schneble
Apr. 17 Sol Gruner
Cornell
X-ray Detectors: State-of-the-art & Future Possibilities
The state-of-the-art of quantitative imaging x-ray detectors is described, as motivated by specific scientific imaging problems. We then consider upcoming technologies that may be applied to imaging detectors to advance the state-of-the-art with respect to pixel size and functionality, spatial resolution, time resolution, analog dynamic range, and energy resolution. We look into our crystal ball and ask what is likely feasible on a decade time scale, given adequate R&D, given current physical limits of materials and technology.

[recorder movie]

Stephens
Apr. 24 Dan M. Stamper-Kurn
Berkeley
Magnetism in quantum gases
With quantum gases, one can explore magnetic ordering and dynamics in regimes inaccessible in solid-state systems. For example, in degenerate spinor Bose gases, magnetization of the atomic spin is established parasitically along with Bose-Einstein condensation, allowing minute spin-dependent energies to dictate the magnetic ordering of the gas. In addition, the extreme isolation of the atomic system allows for systems to created far out of equilibrium, allowing the dynamics of symmetry breaking to probed in real time. A second cold-atom "material," in which atoms are confined within the periodic potential of an optical lattice, bears a stronger resemblance to condensed-matter systems. I will present recent progress to explore the effects of geometric frustration with cold atoms that are confined in a two-dimensional kagome optical lattice. [recorded movie]
Schneble
May 1 graduate director
Graduate Awards Colloquium