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.
January 17 — "Can Evolutionary Dynamics Be Understood Quantitatively?"
- Presenter: Daniel Fisher, Stanford University
- Host: Leo Radzihovsky
- Abstract: The basic laws of evolution have been known for more than a century and there is overwhelming evidence for the facts of evolution. Yet little is understood quantitatively about the dynamical processes that drive evolution: by physicists' standards the theory of evolution is far from fully-fledged. Huge advances in DNA sequencing technology and laboratory experiments have enabled direct observations of evolution in action and, together with theoretical developments, opened up great opportunities for dramatically advancing our understanding. This talk will focus on framing questions and on recent progress addressing some of these.
January 24 — "Zen and the Art of Atomic Physics"
- Presenter: Eric Hudson, University of California, Los Angeles
- Host: John Bohn
- Abstract: In the Ten Bulls tradition, the fifth stage of Zen is reached when the practitioner has caught and tamed the wild bull. This is roughly the state of atomic physics. The atom has been tamed. It can be prepared in a single quantum state, its evolution coherently controlled, and its entanglement generated at will. As such, many new quantum-assisted technologies and fundamental physics measurements have resulted and a quantum revolution is well underway that promises to touch almost every aspect of our lives. By the seventh stage of Zen, the Bull has transcended and is no more. This again may be paralleled in atomic physics as the atom is being replaced with richer quantum systems such as molecules, whose internal degrees of freedom provide new opportunities for quantum science and technology.
In this talk, I will briefly review the science and technology that have come from atom taming and then discuss our efforts to tame other bulls: polar molecular ions and atomic nuclei.
- Presenter: Jonathan Lunine, Cornell University
- Host: Sascha Kempf
February 7 — "Dirac, Jordan, and von Neumann: Hilbert space and transformation theory"
- Presenter: Michel Janssen, University of Minnesota
- Host: Allan Franklin
- Abstract: In early 1927, Paul Dirac and Pascual Jordan, independently of one another, published their versions of a general formalism tying the various forms of the new quantum theory together and giving the theory's statistical interpretation in full generality. This formalism has come to be known as the Dirac-Jordan (statistical) transformation theory. A few months later, in response to these publications by Dirac and Jordan, John von Neumann published his Hilbert space formalism for quantum mechanics. The relation between the two formalisms can be captured in terms of a metaphor of arches and scaffolds that I have argued fits a number of instances of theory change in physics. What is unclear in this case is whether the story is best told with Hilbert space playing the role of the arch built on transformation theory as a scaffold to be dismantled once the arch could support itself, or with transformation theory playing the role of the arch and Hilbert space providing the scaffold built to prevent the arch from collapsing under the weight of its serious mathematical deficiencies. Either way, a narrative for this episode in the history of quantum mechanics based on the arches-and-scaffolds metaphor illustrates the promise of borrowing ideas from the approach to evolutionary biology known as evodevo for reconstructing genealogies of theories rather than species.
- Presenter: Yury G. Kolomensky, University of California, Berkeley
- Host: Eric Zimmerman
- Presenter: Jonas Zmuidzinas, Caltech
- Host: Jason Glenn
February 28 — "Command of Swimming Bacteria by Liquid Crystals"
- Presenter: Oleg Lavrentovich, Kent State University
- Host: Joe MacLennan
- Abstract: Self-propelled bacteria are marvels of nature. If we can control their dynamics, we could use it to power microsystems of the future. Unfortunately, bacteria swim mostly randomly in isotropic liquids such as water. It is difficult to control their dynamics by factors other than transient gradients of nutrients; visual, acoustic and tactile communication channels that humans use to control large animals are not effective. To establish communication, we replace water with a water-based lyotropic liquid crystal, which couples propulsion of bacteria to the orientational order of the medium. The long-range orientational order of the liquid crystal can be designed as uniform or be pre-patterned into various structures by a plasmonic photoalignment technique . The preimposed patterns of liquid crystal orientation allow one to gain a significant control over the dynamics of bacteria, namely, their trajectories, polarity of swimming, spatial variation of concentration , and run-and-tumble behavior . Topological defects of integer strength serve either as attractors or repellents of bacteria, while defect pairs and patterns with broken left-right symmetry pump the bacterial flows along a preselected polar axis. The study of bacteria-liquid crystal system might result in approaches to harness the energy of collective motion for micro-robotic, biomechanical, and sensing devices, as well as micro-mixing and transport of micro-cargo. The work is supported by NSF grants DMR-1507637 and DMS-1729509.
- Presenter: Sae Woo Nam, NIST
- Host: John Price
- Presenter: Krister Shalm, NIST
- Host: John Price
- Presenter: John Miao, University of California, Los Angeles
- Host: Margaret Murnane
March 28 — Spring Break; No Colloquium
- Presenter: Carlton Caves, University of New Mexico
- Host: Scott Diddams
- Presenter: Alain Aspect, Institut d’Optique Graduate School, Palaiseau
- Host: Jun Ye
- Presenter: Jun Ye, JILA, University of Colorado Boulder
- Presenter: Dan Goldman, Georgia Tech
- Host: Meredith Betterton
- Presenter: Colin Broholm, Johns Hopkins University
- Host: Dmitry Reznik
For more information about colloquia this semester, contact: John Price.