1. Quantum Mechanics and the Geometry of Spacetime

    57:38

    from UK College of Arts & Sciences / Added

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    Juan Maldacena Institute for Advanced Study, Princeton

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    • LRSM Science Café: "Nanotube 'Noses': Putting Sniffer Dogs out of Business"

      57:13

      from Felice Macera / Added

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      Nicholas Kybert Physics & Astronomy University of Pennsylvania "Nanotube 'Noses': Putting Sniffer Dogs out of Business" As an all-surface material with environmentally-sensitive electrical properties, carbon nanotubes provide a unique platform for the fabrication of sensors that can detect subtle odor differences and trace chemical residues quickly and reproducibly. This talk will cover advances in scalable fabrication of the devices and their application to challenges ranging from the detection of traces of explosives to 'smelling' cancer. While these experiments are still being conducted in the research laboratory, the opportunities and potential real-world applications that could emerge from this work are wide-ranging and highly impactful.

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      • New Ideas for Axion Dark Matter Detection

        55:55

        from UK College of Arts & Sciences / Added

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        Dr. Peter Graham SLAC The axion is a well-motivated dark matter candidate, but is challenging to search for. We propose a new way to search for QCD axion and axion-like-particle (ALP) dark matter. Nuclei that are interacting with the background axion dark matter acquire time-varying CP-odd nuclear moments such as an electric dipole moment. In analogy with nuclear magnetic resonance, these moments cause precession of nuclear spins in a material sample in the presence of a background electric field. This precession can be detected through high-precision magnetometry. With current techniques, this experiment has sensitivity to axion masses below 10^-9 eV, corresponding to theoretically well-motivated axion decay constants around the grand unification and Planck scales. With improved magnetometry, this experiment could ultimately cover the entire range of masses below 10^-6 eV, just beyond the region accessible to current axion searches. A discovery in such an experiment would not only reveal the nature of dark matter and confirm the axion as the solution of the strong CP problem, but would also provide a glimpse of physics at the highest energy scales, far beyond what can be directly probed in the laboratory.

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        • Skype with Astronaut Andrew Feustel

          55:19

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          Dr. Ravat's AST/EES 310 class had the opportunity to speak with Dr. Andrew Feustel, NASA Astronaut and Mission Specialist for STS-125 and STS-134, on April 2nd, 2013. During this fascinating hour-long conversation, Dr. Feustel described what it is like to go into space, the importance of the scientific advances enabled by NASA, and recounted his experiences on the International Space Station and on the last human service mission to the Hubble Space Telescope.

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          • TITLE

            54:52

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            Dr. Geoff Greene University of Tennessee, Knoxville While neutrons within nuclei may be stable, the free neutron is unstable against beta decay and has a mean lifetime of ~15min. Free neutron beta decay is, perhaps, the simplest weak nuclear process as it is uncomplicated by many body effects that are present in the decay of nuclei. As a result, it can be directly understood in terms of rather simple fundamental weak interaction theory. Additionally, because free neutron decay is the "prototype" for all nuclear beta decays, the neutron lifetime is a fundamental parameter whose value is important not only in nuclear physics, but also in astrophysics, cosmology, and particle physics. I will give an introduction to the theory of weak nuclear decay and briefly discuss the importance of the neutron lifetime as a parameter in the Big Bang. A review of the experimental strategies for the measurement of the neutron lifetime will be given as well as a discussion of the puzzling discrepancy among the measurements with the lowest quoted uncertainty. Finally, I present a very new result recently obtained at the NIST Cold Neutron Research Facility in Gaithersburg Md.

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            • LRSM Science Café: Doug Durian "Grains of Physics"

              54:24

              from Felice Macera / Added

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              Doug Durian Physics, University of Pennsylvania "Grains of Physics" Sand is a problem. At the beach it's fun to scoop and pour, and to make sandcastles. But it's hard to walk on and it sticks everywhere, plus those sandcastles start crumbling right away. The beach can turn to quicksand, and sandy bluffs can collapse in avalanches. Similar problems arise in desert, lunar, and Martian environments. Industries struggle with processing food grains, pharmaceutical powders, minerals for making ceramics and concrete, as well as with coal and geologic formations holding oil and gas. In short, we need to deal with granular materials to secure our food, medicine, shelter, and energy. Unfortunately, lots of things still go wrong. At a basic level, we lack a good understanding of how "sand'' either flows or jams up under applied forces. This is a mechanics problem, and it is difficult because unexpected behaviors emerge for large collections of even the simplest objects like grains. I'll survey this background, explain why physicists have latched onto "sand" as a cutting-edge research topic, and describe some research from my own laboratory on impact cratering and intermittent avalanche flows.

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              • The Proton's Weak Charge

                53:33

                from UK College of Arts & Sciences / Added

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                Dr. David Armstrong College of William and Mary The Proton's Weak Charge One of the highest priorities of present-day experimental particle and nuclear physics is to search for indications of physics which is not contained in the Standard Model. Precision measurements of quantities that are robustly predicted within the Standard Model are an important class of such searches. An example is a measurement of the proton's weak charge. The weak charge is the strength of the proton's vector coupling to the weak neutral current, and its value is a firm prediction of the Standard Model. Thus an experimental test of the prediction is well motivated as a search for new physics. A recently completed experiment at Jefferson Lab, Qweak, has the goal of making the first precision measurement of the weak charge, using parity-violating electron scattering from hydrogen at very low momentum transfer. The result from the first subset of data will be presented, as well as an overview of the data analysis for the full data set and prospects for the final result, which will provide a sensitivity to new physics at the multi-TeV scale.

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                • Rapid Arctic warming and extreme weather events in mid-latitudes: Are they connected?

                  50:14

                  from UK College of Arts & Sciences / Added

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                  Dr. Jennifer Francis Rutgers University In this presentation, I will discuss the hypothesis proposed by Francis and Vavrus (2012) that links rapid Arctic warming (so-called Arctic amplification) to changes in the large-scale atmospheric circulation in the northern hemisphere that favors more persistent weather patterns and a higher likelihood of extreme weather events such as droughts, cold spells, flooding, heavy snows, and heat waves. This hypothesis has been a topic of considerable controversy in recent months, particularly regarding its relationship to the unusual weather conditions that persisted in the winter of 2013/2014. I will discuss various aspects of this linkage, what we know and don't know, and present new related research.

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                  • Galaxy Build-up at Cosmic Dawn: New Insights from Ultra-Deep Hubble and Spitzer Observations

                    49:41

                    from UK College of Arts & Sciences / Added

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                    Dr. Pascal Oesch Space Telescope Science Institute Thanks to ultra-deep observations with the WFC3/IR camera on Hubble the frontier of galaxies has recently been pushed out to z~9-12, only ~450 Myr from the Big Bang. From several large Hubble programs such as the HUDF09, CANDELS, or CLASH, we were able to identify large samples of more than 200 galaxies at z~7-8, and we are now starting to build up the sample sizes of z~9-11 galaxy candidates. In particular, the recent HUDF12 campaign further increased the depth of the WFC3/IR dataset over the Hubble Ultra-Deep Field (HUDF), and enabled us to detect a sample of nine very faint z>8 galaxy candidates in the HUDF. Additionally, the newly completed CANDELS data over GOODS-North now revealed four relatively bright z~9-10 sources, which are in tension with the previous UV LF determination from the GOODS-South field, indicating that star-formation in the early universe might have been very stochastic. Using all z>8 candidates in and around both GOODS fields, we infer that the cosmic star-formation rate density in galaxies with SFR>0.7Msol/yr decreases rapidly at z>8, dropping by an order of magnitude from z~8 to z~10. With complementing, ultra-deep Spitzer IRAC data, we are additionally able to infer the stellar mass densities out to z~8-10. In this talk I will highlight recent progress in exploring the high redshift frontier and in understanding the growth of galaxies in the first two billion years. In particular, I will present current constraints on the UV luminosity function of galaxies at z>8, and I will demonstrate the power of combining deep Hubble and Spitzer data to directly track the star-formation and mass build-up of z>=4 galaxies.

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                    • Samir Mathur

                      46:22

                      from UK College of Arts & Sciences / Added

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                      Samir Mathur presenting at Great Lakes Strings 2013.

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