Events - Weekly
|Sunday, February 19|
|Monday, February 20|
Biophysics Seminar - Joseph Loparo, Harvard Medical School “Bridging the gap: Single-molecule studies of DNA double strand break repair”
Non-homologous end joining (NHEJ) is the primary repair pathway for double-strand breaks in human cells, yet we lack a detailed understanding of how broken DNA ends are brought together, enzymatically processed, and joined. To better understand these questions, we have developed single-molecule assays to visualize NHEJ in Xenopus egg extracts. Egg extract is a powerful system to study NHEJ because it contains the complete soluble proteome and robustly carries out efficient repair in a manner that depends on all of the core NHEJ factors. Using single-molecule colocalization and FRET assays to watch the association of DNA ends in real time, we recently showed that the NHEJ machinery passes through at least two distinct synaptic states (Graham et al. Mol Cell 2016). DNA ends are initially tethered >50 Å apart in a relatively unstable “long-range” complex that depends on the NHEJ factors Ku and DNA-PKcs. DNA-PKcs kinase activity and the NHEJ factors responsible for ligation (XLF, XRCC4, and LIG4) are then required to transition to a stable “short-range” complex in which the ends are brought into close alignment prior to ligation. In this talk I will describe how we are extending these studies to better understand how the NHEJ machinery assembles on DNA ends and how DNA end processing is regulated to maximize the fidelity of repair.
Joseph Henry Room · 12:00 p.m.– 1:00 p.m.
New quantum phases of matter in strongly correlated and spin-orbit-coupled metals - John Harter, Caltech
Strong interactions between electrons are known to drive metallic systems toward a variety of well-known symmetry-broken phases, including superconducting, electronic liquid crystalline, and charge- and spin-density wave ordered states. In contrast, the electronic instabilities of correlated metals with strong spin-orbit coupling have only recently begun to be explored. In this talk, I will discuss a new class of parity-breaking Fermi liquid instabilities enabled by spin-orbit coupling. These instabilities are distinguished by the spontaneous development of a lattice-locked spin texture on the Fermi surface, generalizing the notion of itinerant ferromagnetism. I will argue that nonlinear optical spectroscopy is an ideal experimental tool to search for these phases in quantum materials, and I will discuss our recent experimental discovery of one such phase--multipolar electronic nematic order--in a strongly spin-orbit-coupled metallic pyrochlore.
Jadwin 303 · 1:00 p.m.– 2:00 p.m.
|Tuesday, February 21|
Next-generation atomic clocks - G. Edward Marti, JILA
Abstract: The accuracy of atomic clocks has improved a thousandfold over the last 15 years, driven by improvements in ultrastable lasers, quantum control, and our understanding of atomic interactions. The latest generation of optical lattice clocks are accurate enough to measure general relativity's gravitational redshift at the centimeter scale, to test physics beyond the Standard Model, and to reveal new emergent properties of quantum materials. In this talk, I will discuss the principles behind state-of-the-art optical lattice clocks and describe a clock that reaches a record accuracy of 1 mHz on an optical transition at 429 THz, a fractional frequency accuracy of 2 parts in 10^18. I will also discuss a next-generation clock that probes degenerate fermions in a three-dimensional optical lattice. By controlling atomic interactions and light shifts, this apparatus achieved a record atom-light coherence time of six seconds, reaching sub-100 mHz spectroscopic features. Finally, if time allows, I will discuss prospects for improved accuracy in a cryogenic strontium clock and for tests of fundamental physics with clocks.
Jadwin 303 · 1:30 p.m.– 2:30 p.m.
Special Seminar | Yakir Aharonov, Chapman University | "Time Symmetric Formulation of Quantum Theory"
PCTS Seminar Room · 3:00 p.m.– 4:30 p.m.
Pheno & Vino Seminar, Matthew Klimek, U. Texax, "Multidimensional phase space methods for mass measurements and decay topology determination"
The lack of conclusive evidence for new physics so far at the LHC suggests that future discoveries may manifest themselves with small numbers of signal events. In this case, it will be crucial to use analysis techniques that extract as much information as possible from a limited number of events. Collider events with multi-stage cascade decays fill out the kinematically allowed region in phase space with a density that is enhanced at the boundary. The boundary encodes all available information as regards the spectrum and is well populated even with moderate signal statistics due to this enhancement.
I will discuss the improvement in the precision of mass measurements for cascade decays with one invisible particle that is possible when the full boundary information is used, as well as the possibility of determining decay topologies with this information.
Jadwin 303 · 4:00 p.m.– 5:30 p.m.
|Wednesday, February 22|
HET Seminar | Leonard Susskind, Stanford University | “Black Holes and Quantum Complexity”
Bloomberg Lecture Hall - Institute for Advanced Study · 11:00 a.m.–12:00 p.m.
Spec. Condensed Matter Seminar, Yakir Aharonov, Chapman Univ. "Novel properties of pre- and-post selected quantum systems"
PCTS Seminar Room · 2:00 p.m.– 3:30 p.m.
|Thursday, February 23|
Hamilton Colloquium: Yakir Aharonov, Chapman University; Professor Emeritus, Tel Aviv University, Israel; "Non-local phenomena in Quantum Mechanics"
I discuss in my talk a reformulation of quantum mechanics in which each quantum system at any time is described by two Hilbert space vectors rather than one. One of the vectors propagates from a past boundary condition towards the present and the other propagates back to the present from a future boundary condition. I will show that this reformulation uncovers a host of fascinating new phenomena, some of which will be described in detail within this talk. Finally, I will show that this new reformulation suggests a novel solution to the notorious problem of the Quantum Measurement.
Jadwin A10 · 4:00 p.m.– 5:00 p.m.
|Friday, February 24|
Gravity Group Seminar, Cyrille Doux (APC, France)
Cosmic microwave background lensing and Lyman-α forest bispectrum
Cosmic microwave background (CMB) gravitational lensing probes the matter density field integrated along the line of sight and traces large-scale fluctuations, while the Lyman-α forest in the spectra of quasars traces small-scale fluctuations in the neutral hydrogen density field. For each Lyman-α forest in SDSS-III/BOSS DR12, we correlate the one-dimensional power spectrum with the cosmic microwave background lensing convergence on the same line of sight from Planck. This measurement constitutes a position-dependent power spectrum, or a squeezed bispectrum, and quantifies the nonlinear response of the Lyman-α forest power spectrum to a large-scale overdensity. In this talk, I will present this theoretical approach, the measurement, and the possible use of this new observable in the future as an independent test of our understanding of the relation between intergalactic gas and dark matter.
Joseph Henry Room · 12:00 p.m.– 1:00 p.m.
HET Seminar | Leonard Susskind, Stanford University | “The Second Law of Quantum Complexity”
Bloomberg Lecture Hall - Institute for Advanced Study · 1:45 p.m.– 2:45 p.m.
The Science of Memory: A Live Radio Event
Art and science mesh together in this free, live-radio event featuring Princeton Laptop Orchestra. Scientific American opinion editor Mike Lemonick and Princeton neuroscientist Sabine Kastner will take the stage together, sharing their encounters with a local artist and pilot who lost her ability to form memories. Meanwhile, PLOrk will break up the interview with their inventive compositions--one of which will be based on real data from the brain. Two WPRB radio DJs and Princeton graduate researchers Stevie (physics) and Brian (plasma physics) will host the show, using the unique format of their science show on WPRB Princeton, These Vibes Are Too Cosmic.
This event is open to the public, and is sponsored by the Princeton Council on Science and Technology. Friday, February 24th, 2017 at 7:30pm at Taplin Auditorium in Fine Hall.
Taplin Auditorium · 7:30 p.m.– 8:30 p.m.
|Saturday, February 25|