Fall 2013 Colloquium Schedule

Colloquia are Wednesdays at 4:00 p.m. in DUAN G1B20, unless otherwise noted.

Coffee, tea and cookies will be available before regular colloquia beginning at 3:45 p.m. in DUAN G1B31.

Past Colloquia

August 28 — "Ultracold Polar Molecules"

  • Presenter: Deborah Jin, JILA, University of Colorado Boulder
  • Host: Murray Holland
  • Abstract: Gases of atoms can be cooled to temperatures close to absolute zero, where intriguing quantum behaviors such as Bose-Einstein condensation and superfluidity emerge.  A new direction in experiments is to try to produce an ultracold gas of molecules, rather than atoms.  In particular, polar molecules, which have strong dipole-dipole interactions, are interesting for applications ranging from quantum information to modeling condensed matter physics.  I will describe experiments that produce and explore an ultracold gas of polar molecules. 

September 4 — "Superposition, Entanglement, and Raising Schrödinger’s Cat"

  • Presenter: David Wineland, NIST, University of Colorado Boulder
  • Host: Jun Ye
  • Abstract: Research on precise control of quantum systems occurs in many laboratories throughout the world, for fundamental research, new measurement techniques, and more recently for quantum information processing. I will briefly describe experiments on quantum state manipulation of atomic ions at NIST, which serve as examples of similar work being performed with many other atomic, molecular, optical (AMO) and condensed matter systems across the world. This talk is in part the “story” of my involvement that I presented at the 2012 Nobel Prize ceremonies.

September 11 — "Distributed Information Processing in Materials that Think"

  • Presenter: Nikolaus Correll, University of Colorado, Boulder
  • Host: Tobin Munsat
  • Abstract: Materials that think are enabled by recent advances in smart polymers, desktop manufacturing systems and miniaturization of computers.  These materials tightly integrate sensing, actuation, computation and communication in a periodic, amorphous fashion, which might enable revolutionary new composites with fully programmable capabilities.  The challenges in creating materials that think lie at the intersection of material science engineering and computer science, and - from a CS perspective - require advances in distributed algorithms for signal processing, control and routing of information.  I illustrate these challenges and recent advances by our group using three experimental case studies, all using identical computational infrastructure: (1) a soft robotic skin that can locate and classify textures by locally sampling, processing and classifying vibrations and route relevant information to a CPU using multi-hop networking; (2) A modular building block for creating intelligent walls and facade systems that can recognize complex gestures; and (3) variable-stiffness composites that can assume arbitrary shapes using simple actuation and local feedback control.  Albeit serving different functions at different scales, material and computational properties can be designed using an unified mathematical framework based on abstracting the computer network as continuous amorphous medium.

September 18 — "Quantum Phases of Matter"

  • Presenter: Michael Hermele, University of Colorado Boulder
  • Host: Paul Beale
  • Abstract: Much of condensed matter physics is based on the idea that two different systems can be in the same phase of matter, with its own characteristic properties.  Some phases of matter are intrinsically quantum in nature, including metals, band insulators and fractional quantum Hall liquids.  In recent years, it has become clear that we lack a satisfactory understanding even of the most basic question: "What constitutes a distinct quantum phase of matter?" This colloquium will describe my recent contributions toward an answer.

September 25 — "Topological Soft Matter: From Mathematical Theorems to Self-Assembly"

  • Presenter: Ivan Smalyukh, University of Colorado Boulder
  • Host: Paul Beale
  • Abstract: Topologically nontrivial fields and vortices frequently arise in superstring and quantum field theories, plasmas, optics, elementary particles, cosmology, condensed matter and atomic systems, etc. Their complex structures are expected to follow predictions of topological theorems and mathematical theories, such as the knot theory, but are rarely accessible to direct experimental visualization. On the other hand, soft condensed matter systems, such as colloids and liquid crystals, offer complexity in degrees of freedom and symmetries that allow for probing analogous phenomena on completely different scales, ranging from kinetics of atoms in glasses to cosmic strings in the early Universe. In my lecture, I will show examples of how CU students extend these possibilities by developing soft matter model systems to probe the scale-invariant interplay of topologies of surfaces, fields, and defects. This combination of topology and self-assembly paradigms emerges as an interdisciplinary scientific frontier of topological soft matter, potentially enabling scalable fabrication of composite materials with unusual properties.

October 2 — "Manybodypedia, Cluster-by-Cluster"

  • Presenter: Mackillo Kira, Universität Marburg, Germany
  • Host: Steven Cundiff
  • Abstract: Several seemingly unrelated research efforts are approaching the same central question: how does the quantum physics of interacting many-particle systems control macroscopic phenomena? This would be easy to answer if one only were able to solve the many-body Schrödinger equation exactly, a task that seems unsolvable for decades to come. The number of theoretic approaches and experimental setups are steadily increasing, which also makes the knowledgebase scattered. Therefore, it seems that one should start a thorough learning process, pedia, to combine and develop common many-body knowhow.
    In this talk, I present a tutorial “manybodypedia” by comparing semiconductors, atom condensates, and degenerate Fermi gases. I analyze them with correlated clusters that rigorously identify the elementary particle configurations, quasi-particles, within many-body systems. It turns out that the clusters also reformulate quantum optics in a form suitable for many-body investigations. The clusters can therefore be viewed as the “alphabets” combining the knowhow in quantum-optics and various many-body studies. As a synthesis of these concepts, I introduce the quantum-optical spectroscopy that produces unprecedented access to unexplored many-body physics.

October 9 — "Fierce Competition in a Correlated World"

  • Presenter: Kyle McElroy
  • Host: Paul Beale
  • Abstract: One of the most important states of matter we see around us is the Landau-Fermi liquid. In fact, this is the state of matter electrons have in metals and semiconductors which we rely on so much in our technology. Over the last several decades we have seen that introducing strong correlations and destroying this traditional conducting state leads to new and dramatic macroscopic states of matter. One playground for these new behaviors is doped Mott insulators, where Coulomb repulsion localizes electrons and competes with the itinerancy of introduced carriers. Such competition leads to strong atomic scale variation in the electronic properties which are a key component in understanding the resulting macroscopic phenomena.
    We have developed microscopic techniques for measuring the electronic structure on the atomic scale. With these probes we have investigated several materials in which atomic scale disorder plays a huge role in the electronic structure. I will discuss several examples where these probes have let us uncover the true microscopic nature of these macroscopic phases that are hidden on the bulk scale.

October 16 — "Crystallization Mechanisms in Biominerals"

  • Presenter: Pupa Gilbert, University of Wisconsin - Madison
  • Host: Meredith Betterton
  • Abstract: Biominerals include mollusk shells and the skeletons of algae, sponges, corals, sea urchins and most other animals. The function of biominerals are diverse: mechanical support, attack, defense, grinding, biting, and chewing, gravitational and magnetic field sensing, light focusing, and many others. The exquisite nanostructure of biominerals is directly controlled by the organisms, which have evolved to master the chemico-physical aspects of mineralization. By controlling the inorganic precursor nanoparticle size, packing, and phase transitions, organisms efficiently fill space, produce tough and hard structures, with micro- or macroscopic morphology optimized for their functions. Specifically, this talk will show the complex architecture of mollusk shell nacre, or mother-of-pearl, and how it is formed by animal-controlled self-assembly.
    Biominerals Representation

October 23 — "Black Holes–the Harmonic Oscillators of the 21st Century"

  • Presenter: Andrew Strominger, Harvard University
  • Host: Oliver DeWolfe
  • Abstract: In the twentieth century, many problems across all of physics were solved by perturbative methods which reduced them to harmonic oscillators. Black holes are poised to play a similar role for the problems of  twenty-first century physics. They are at once the  simplest and most complex objects in the physical universe. They are maximally complex in that the number of possible microstates, or entropy, of a black hole is believed to saturate a universal bound. They are maximally simple in that, according to Einstein's theory, they are featureless holes in space characterized only by their mass, charge and angular momentum. This dual relation between simplicity and complexity, as expressed in black holes, has recently been successfully applied to problems in a disparate variety of physical systems. I will give an introduction to the subject intended for a general audience.

October 30 — "Assessing the Cumulative Impact of Humans on the Landscape"

  • Presenter: James Syvitski, University of Colorado Boulder
  • Host: Tobin Munsat
  • Abstract: Humans are changing the Earth’s biophysical system — atmospheric and ocean climatology and chemistry, extent of snow cover, permafrost and sea-ice, glacier, ice-sheet and ocean volume, and indeed the hydrological cycle.  Some changes are truly global, represented by similar temporal trends — atmospheric greenhouse gases, global surface temperatures, nitrogen fluxes to the coastal zone, and species extinctions. 

    Striking is the extent and rate at which humans have modified Earth’s land surface; as just one example, humans are now the largest force in the movement of sediment — greater than ice, wind and water.  The traces of humanity (e.g. petroleum wells, geotechnical boreholes, mining-exploration holes, and deep-water wells) will last millions of years.  Historical deforestation and land clearing have greatly impacted soil erosion, hill slope failure and downstream sedimentation. 

    In this talk, I will discuss how, by any measure, we have entered a new geological era (labeled the Anthropocene), unique to the history of our planet. Some of these changes have crept up on us; others have gone unrecognized until recently. Global sustainability involves facing our risks both global and local and aligning governance with stewardship.

November 6   — "Poincaré's Tangle: The Topology of Chaos in State Space"

  • Presenter: Richard Kautz, NIST
  • Host: David Bartlett
  • Abstract: In 1889, while investigating the notorious problem of three gravitationally attracting bodies, Henri Poincaré discovered a tangled topological structure that we now recognize as the mathematical heart of chaotic motion. Poincaré would later write of his discovery, "One is struck by the complexity of this picture, which I do not even attempt to draw." Using the driven pendulum as an example and graphics as our primary tool, we will explore the topology of state space, where the trajectories of a system are visible as the streamlines of a flow. Saddle orbits within a flow are the keys to its topology and led Poincaré and his successors to understand that the trajectories of seemingly simple systems can be entwined in infinitely complex patterns. In 1960 Steve Smale introduced the horseshoe map as perhaps the simplest example of a state-space tangle and applied symbolic dynamics to demonstrate how chaos can be "as random as a series of coin flips."

November 13 — "Brilliant Blunders: From Darwin to Einstein – Colossal Mistakes by Great Scientists That Changed Our Understanding of Life and the Universe"

  • Presenter: Mario Livio, Hubble Space Telescope Science Institute
  • Host: Tobin Munsat
  • Abstract: Charles Darwin, William Thomson (Lord Kelvin), Linus Pauling, Fred Hoyle, and Albert Einstein were all brilliant scientists. Each made groundbreaking contributions to his field—but each also stumbled badly. For example, Darwin’s theory of natural selection shouldn’t have worked, according to the prevailing beliefs of his time. Not until Gregor Mendel’s work was known would there be a mechanism to explain natural selection. How could Darwin be both wrong and right? Astrophysicist Fred Hoyle dismissed the idea of a “Big Bang” origin to the universe. And Albert Einstein, whose name is synonymous with genius, speculated incorrectly about the forces that hold the universe in equilibrium—and that speculation opened the door to brilliant conceptual leaps. These scientists expanded our knowledge of life on earth, the evolution of the earth itself, and the evolution of the universe, despite and because of their errors. In this talk, I will discuss how the scientific process advances through error. Mistakes are essential to progress.

November 20 — "Mission 'Impossible': Exploring the Properties of Hot QCD Matter"

  • Presenter: Berndt Mueller, Duke University
  • Host: Paul Romatschke
  • Abstract: This lecture presents an overview of the status of the investigation of the properties of the quark-gluon plasma using relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). My lecture will focus on the insights that have been gained to date by the comparison experimental data from both facilities with theoretical calculations, highlight some of the present challenges, and end with an outlook on the experimental investigations that are planned for the next decade.

November 27 — Fall Break; No Colloquium

December 4 — "The National Solar Observatory — The Coming Decade of Discovery"

  • Presenter: Mark Rast, LASP, University of Colorado Boulder
  • Host: Tobin Munsat
  • Abstract: The move of the headquarters of the National Solar Observatory to the Boulder campus is underway, as is the construction of the four meter Advanced Technology Solar Telescope (ATST). This talk will focus on how these events promise, over the coming years, to transform solar physics and how it is taught at the university. The mission of the National Solar Observatory is to advance our knowledge of the Sun in the contexts of both stellar astrophysics and solar influences. The ATST will contribute by providing diffraction limited spectropolarimetric observations of the solar photosphere, chromosphere, and corona, resolving for the first time the fundamental interactions between solar magnetic fields and the dynamic plasma on scales below 0.1 arcsec. The aim is to elucidate the magnetohydrodynamic underpinnings of the solar dynamo as well as the reconfiguration of magnetic fields during flare and coronal mass ejection events. Since research in solar physics requires a knowledge base that is both wide-ranging and carefully focused, it poses challenges to effective graduate education. We will describe these and ongoing efforts to address them through a distributed program.

December 11 — "Science with 800,000 Collaborators: Tales from the Zooniverse"

  • Presenter: Chris Lintott, University of Oxford, UK
  • Host: Paul Romatschke
  • Abstract: The Zooniverse is the world's largest and most successful scientific crowdsourcing platform, engaging more than 800,000 volunteers in tasks including classifying galaxies, discovering planets and mapping star formation in the Milky Way. This talk will present highlights from the last six years, including the serendipitous discovery of galaxy-scale light echoes, and explain how an unusual set of bulgeless spiral galaxies identified by Galaxy Zoo volunteers is informing models of galaxy formation and feedback. The talk will also set out the future for this massively distributed effort in the world of future facilities such as the LSST and SKA.

For more information about colloquia this semester, contact: Tobin Munsat.