Fall 2008 Physics Colloquium Schedule

University of Colorado Department of Physics

Colloquia are Wednesdays at 4 PM, Duane G1B20 unless otherwise noted

Coffee, tea, and cookies before regular colloquia at 3:45 PM in Duane G1B31

Upcoming Colloquia:

August 27

Ian McNulty, Argonne National Laboratory
Host: Margaret Murnane
Title: A perfect storm: lensless x-ray imaging at the nanometer scale
Abstract: The confluence of three recent technical breakthroughs has resulted in a "perfect storm" in nanometer-resolution x-ray imaging. Brilliant sources of coherent x-rays, megapixel array detectors, and powerful numerical phase retrieval methods have engendered a rapidly advancing new capability for imaging the internal structure of three-dimensional objects, unhampered by the limitations of x-ray lenses. Third-generation synchrotron sources have mainly fueled this progress until now. The next generation of coherent pulsed x-ray sources - both large-facility and laboratory scale - is promising for x-ray nanoscopy in the femtosecond regime, where ordering during magnetic phase transitions could be frozen in time and organelles within intact biological cells could be studied without radiation damage artifact. This talk reviews advances in lensless x-ray coherent diffraction imaging and considers exciting new directions in the materials, condensed matter, energy, and life sciences this technique may take in the near future.

September 3

Jed Buchwald, Caltech
Host: Allan Franklin
Title: The Newtonian Origins of Experimental Error
Abstract: In the mid-1750s the English mathematician Thomas Simpson tried to convince astronomers that it was a good idea to average multiple measurements. He had much work to do, because neither astronomers nor physicists were in the habit of combining multiple measurements to produce a best final value. How then did experimenters and observers work with discrepant data before statistical methods became common at the beginning of the 19th century? We will first tour the worlds of Tycho Brahe, Robert Hooke, Ren? Descartes and Johannes Hevelius to see how they worked with data. And then we turn to the young Isaac Newton, who developed an altogether novel way with measurements, the very way that became ever after the foundation of experimental method, for it was Newton who first decided that bad numbers could be put together to generate good ones.

September 10

Steve Olsen, University of Hawaii
Host: David Bartlett
Title: The XYZ exotic(?) Mesons
Abstract: There has been considerable interest in recent years in the possible existence of hadrons that do not fit into the quark-antiquark meson or three-quark baryon arrangements prescribed by the Constituent Quark Model of Gell-Mann and Zweig. This revival of interest was initially stimulated by numerous claims for observation of pentaquark baryon states. In addition, the BES e+e- collider experiment in China as well as the BaBar and Belle e+e- B-factory experiments have reported observation of a umber of mesons --most notably the X(1835), X(3872), Y(4260) & the Z(4430)-- that do not match neatly to expectations for conventional quark-antiquark mesons. While the evidence for the existence of pentaquark baryons now seems pretty dubious, the existence of at least the the X & Y of the XYz mesons is experimentaly well established. For these states, the main question, and the subject of this talk, is whether or not they are elements of some new type of spectroscopy or, instead, evidence of deficiencies in our basic understanding of how quarks combine together to form hadrons.

September 17

David Wineland, NIST
Host: Dan Dessau
Title: Quantum information processing and quantum metrology with trapped ions
Abstract: Over the last decade or so, there has been an explosion of activity in quantum information processing (QIP). Arguably, Shor's algorithm for efficiently factoring large numbers stimulated much of the interest; however experimentally, this application remains a distant goal. Nearer-term possibilities include practical quantum communication and quantum simulation. Also, we can apply some simple QIP procedures to metrology; examples where entanglement can lead to improved detection sensitivity in interferometry and spectroscopy are discussed in the context of trapped ions. If we can eventually apply some of these techniques to large numbers of ions, we might realize a direct analog of Schroedinger's cat, a bizarre situation in which Prof. Schroedinger's cat is simultaneously dead and alive.

September 24

Barry Zink, University of Denver
Host: Kyle McElroy
Title: Electron and Phonon Transport in Thermoelectric Thin Films and Nanostructures
Abstract: Energy solutions for the coming decades require broad-based investigation into a range of technologies. Clean, high-efficiency energy technologies are likely to involve devices that employ more than one route to energy conversion. For example, adding a thermoelectric generator to a solar cell could improve the efficiency of overall energy production by converting unused thermal energy to electric energy. Though recent years have seen significant advances, the new developments in materials that will allow thermoelectric devices to fully realize their potential for energy conversion remain elusive. Nanoscale engineering of materials, made possible by modern tools for patterning and manipulation of matter at small length scales, has shown early promise and may lead to rapid improvement in thermoelectrics. A fairly wide range of fundamental studies reveal that the electronic, vibrational, and magnetic excitations in such systems can behave much differently than in bulk, equilibrium phases, but some measurements that are particularly important for thermoelectrics remain very challenging for systems such as thin films and nanowires. This talk will briefly introduce the challenges of thermal measurements of small samples, consider the fascinating physics of such systems, and describe our current work toward identifying potential breakthroughs in thermoelectric materials through direct experimental studies of electronic, vibrational, and magnetic excitations in small structures and novel materials.

October 1

Paul Chaikin, New York University
Host: Ivan Smalyukh
Title: Toward Self-Replication with Colloids
Abstract: We want to make a non-'biokleptic' system which can self-replicate. The idea is to design colloids with specific and reversible and irreversible interactions, introduce seed motifs, and cycle the system in such a way that a copy is made. Repeating the cycle would double the number of offspring in each generation leading to exponential growth. We're not there yet! We use colloidal particles with bound DNA sequences for reversible recognition. DNA allows us to independently fine tune the strength and the temperature dependence of the interparticle interactions. They now "work" - recognize, cycle and can be permanently attached as well. So the talk will be on where we are, how we got there and where we're going.

October 8

B. Lee Roberts, Boston University
Host: John Cumalat
Title: Muon (g-2) - A Probe of the Standard Model and Beyond
Abstract: Since the experiments of Stern and Gerlach, magnetic moments of "elementary" particles have been important in our quest to understand subatomic physics. The first "QED loop calculation" was done by Schwinger to explain the larger than expected hydrogen hyperfine structure. The definitive measurement of the electron's anomaly by Kusch and Foley followed and agreed well with Schwinger's calculation of a_e = (a/2 p). The muon's anomaly, which is sensitive to a broad range of physics beyond the standard model, will be discussed in a historical context, following the intellectual development of modern physics through the 20th century. Experiment E821 at Brookhaven will be described, as well as possible improvements, which are highly desirable since the present value of the muon anomaly, appears to differ from the standard-model value.

October 15

Joseph Fowler, Princeton University
Host: Eric Zimmerman
Title: The Atacama Cosmology Telescope: Mapping the Microwave Background to Understand Cosmic Inflation and Structure Formation
Abstract: Mapping the primordial cosmic microwave background (CMB) has proven to be an unrivaled tool for learning about cosmic history over a wide range of timescales. Measurements made to date have contributed greatly to our current age of "precision cosmology", but future observations at finer angular scales still promise new features. The epoch when massive galaxy clusters formed can be probed through the Sunyaev-Zel'dovich effect, while the immensely earlier era of inflation influences the same maps through the slope of their spatial power spectrum. Gravitational lensing of the CMB itself might even be within reach of current instruments.
The Atacama Cosmology Telescope (ACT) has just begun observing the microwave sky at 140 through 280 GHz with over 3000 detectors. ACT exemplifies many of the technical challenges involved in measuring sky brightness with parts-per-million accuracy, along with the technical advances from sites like NASA-Goddard and NIST that propel the latest CMB experiments.

October 22

Young S. Lee, Massachusets Institute of Technology
Host: Michael Hermele
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October 29

Jorge Piekarewicz, Florida State University
Host: Jim Shepard
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November 5

Kevin Lesko, Lawrence Berkeley Laboratory
Host: Eric Zimmerman
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November 12

Hassan Jawahery, University of Maryland
Host: Jim Smith
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November 19

Jamie Nagle, University of Colorado
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November 26: No colloquium: Thanksgiving Break

December 3

Paul Goldbart, University of Illinois
Host: Michael Hermele
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December 10

Michelle Wang, Cornell University
Host: Meredith Betterton
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Colloquia that have already occurred:

Colloquium schedules from previous semesters can be found here

Contact:

Eric D. Zimmerman