Events at Physics |
Events on Thursday, February 4th, 2016
- R. G. Herb Condensed Matter Seminar
- TBD
- Time: 10:00 am - 11:00 am
- Place: Chamberlin 5310
- Speaker: Ivar Martin, Argonne National Laboratory
- Abstract: TBD
- Host: Vavilov
- R. G. Herb Condensed Matter Seminar
- TBD
- Time: 10:00 am - 11:00 am
- Place: Chamberlin 5310
- Speaker: Ivar Martin, Argonne National Laboratory
- Abstract: TBD
- Host: Vavilov
- R. G. Herb Condensed Matter Seminar
- Dynamics of interacting disordered quantum spin systems
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Ivar Martin, Argonne National Laboratory
- Abstract: Localized paramagnetic electrons are believed to be the cause of magnetic flux noise that plagues superconducting qubits; however, how such interacting spins generate frequency dependent noise of the 1/f form is not well understood due to the complexity of the full quantum mechanical treatment of interacting spin system. In this talk I will describe a dynamical real space renormalization group (RG) procedure that allows to calculate directly various dynamical quantities in a strongly disordered Heisenberg spin systems. Using this approach we generally find the dynamics that correspond to (anomalous) spin subdiffusion, with a powerlaw low-frequency magnetic noise, which appears to be consistent with what is observed in superconducting circuits.
- Host: Vavilov
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Forging the Heaviest Elements
- Time: 2:30 pm - 3:30 pm
- Place: 5310 Chamberlin Hall
- Speaker: Rebecca Surman, Notre Dame
- Abstract: While the origins of the light (hydrogen, helium) and intermediate mass(carbon through iron) elements found in our solar system are well understood, we still don't know where roughly half of the elements heavier than iron were made. From the solar system abundance pattern of these nuclei, we can tell they were synthesized via rapid neutron captures in the r-process of nucleosynthesis. Exactly where the appropriate astrophysical conditions for the r-process exist, however, is still uncertain. Here we will discuss the two most popular potential astrophysical sites---core-collapse supernovae and neutron star mergers---and describe how progress in open issues in neutrino and nuclear physics may be the key to unlocking this longstanding mystery.
- Host: Balantekin
- Special Cosmology Seminar
- Design and Deployment of the first Multichroic Polarimeter array on the Atacama Cosmology Telescope
- Time: 3:30 pm - 4:00 pm
- Place: 5280 Chamberlin Hall
- Speaker: Rahul Datta, University of Michigan
- Abstract: The polarization of the Cosmic Microwave Background (CMB) provides a unique window into the physics of inflation, an alternative means to measure the neutrino mass sum, and enables a multitude of other astrophysical studies. Measurements of the inflationary B-mode signal requires instruments capable of mapping the CMB at multiple frequency bands with unprecedented sensitivity and excellent control over systematics. Feedhorn-coupled detectors with sensitivity to multiple spectral bands within a single focal plane element offer an avenue to achieve these goals. The Atacama Cosmology Telescope Polarimeter (ACTPol) instrument is optimized to make arcminute resolution measurements of CMB polarization, CMB lensing, and other secondary anisotropies. I will present the design of a feedhorn-coupled multichroic detector array encompassing the 90 and 150 GHz frequency bands and the ancillary technology needed to implement this array in the ACTPol experiment. This receiver, deployed in January 2015, represents the first multichroic detector array deployed for a CMB experiment and is now the most sensitive ACTPol array. I will also present the preliminary on-sky performance of this array. I shall conclude with a brief discussion about the ongoing work on the detection of polarized point sources in the ACTPol CMB maps and their impact on the estimation of the E-mode polarization power spectrum.
- Host: Kam Arnold