Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session S9: Invited Session: Cosmic Microwave Background B Modes and Inflation |
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Sponsoring Units: DAP DPF Chair: Lloyd Knox, University of California, Davis Room: Key 5 |
Monday, April 13, 2015 1:30PM - 2:06PM |
S9.00001: Measurements of B-mode Polarization at degree angular scales with the BICEP2, Keck, and Planck Invited Speaker: John Kovac The theory of cosmic inflation postulates that the initial conditions of our observable universe arose from quantum fluctuations during a very early burst of exponential expansion. The BICEP / Keck Array experiments are a series of cosmic microwave background (CMB) polarimeters specifically designed to search for gravitational waves predicted by inflation by looking for the faint B-mode patterns they would imprint on degree-scale CMB polarization. Observing from the South Pole between 2010 and 2012, the BICEP2 telescope made maps of unprecedented sensitivity at degree angular scales over 2\% of the sky, In March 2014 the BICEP2 team reported a high signal-to-noise detection of B-mode polarization at 150 GHz, at a level well above typical predictions of galactic foreground models for that region of sky, and consistent with a large contribution from inflationary gravitational waves. However, later last year high-frequency results reported by the Planck satellite indicated levels of polarized emission from galactic dust potentially high enough to account for the entire BICEP2 signal. In a recently published joint analysis that combines data from BICEP2, the Keck Array, and the Planck satellite, we find that there is not currently significant evidence for a gravitational wave signal, and we set the tightest constraints yet on its possible level. The outlook for continued progress using ultra-deep maps at multiple frequencies is strong. I will describe our current results and the continuing hunt for inflationary gravitational waves both with the BICEP / Keck Array experimental program and with future efforts. [Preview Abstract] |
Monday, April 13, 2015 2:06PM - 2:42PM |
S9.00002: Models of Polarized Emission from Interstellar Dust Grains Invited Speaker: Bruce Draine Nonspherical aligned dust grains produce strong linearly-polarized thermal emission at submm and microwave frequencies, with polarized fractions exceeding 20\% in some parts of the high-latitude sky. Observations of emission, absorption, and scattering by dust, together with our knowledge of the abundances of elements out of which dust grains can be formed, impose many constraints on dust modelers. The dust is in large part composed of amorphous silicates, but with a substantial component of carbonaceous materials, including nanoparticles of polycyclic aromatic hydrocarbons. The smallest particles radiate thermally in the mid-IR following single-photon heating, and also produce rotational emission at microwave frequencies. This rotational emission may account for the so-called Anomalous Microwave Emission. Iron contributes about 25\% of the total mass of interstellar dust, but what form the Fe is in is largely unknown; much of the Fe could be in ferromagnetic or ferrimagnetic materials that could emit magnetic dipole radiation at microwave frequencies. I will review the observational constraints on dust models, the current state of our physical models, and prospects for further progress. [Preview Abstract] |
Monday, April 13, 2015 2:42PM - 3:18PM |
S9.00003: The Theory of Inflation Invited Speaker: Sarah Shandera I will discuss the importance of measurements or improved constraints of primordial tensor modes for theories of the primordial universe. In particular, I will review the implications of the amplitude of the tensor fluctuations for inflation and discuss what an era of B-mode cosmology could teach us about particle physics near the Planck scale. [Preview Abstract] |
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