Physics and Astronomy Calendar

Week of Monday, November 20th 2017

Monday, November 20th 2017
12:15 pm:
Speaker: Allison Noble, MIT, Kavli Institute
Subject: Dissecting z>1 Galaxy Clusters: Studying Star Formation from the Outskirts to the Core

Understanding the influence of environment on baryonic processes is a fundamental goal in studies of galaxy evolution, and galaxy clusters offer ideal laboratories with which to examine environmental effects on their constituent members. Clusters continually evolve and build up mass through the accumulation of galaxies, resulting in distinct galaxy populations based on their accretion history. I will discuss using cluster phase space (line-of-sight velocity versus projected clustercentric radius) as a way to probe the accretion histories of cluster galaxies to study environmental effects on star formation at z~1. I will also present recent ALMA observations of massive gas reservoirs in z=1.6 cluster galaxies. The raw fuel of star formation, molecular gas is typically absent in low-redshift cluster galaxies; with these new ALMA data, we are witnessing the first direct evidence that gas-rich galaxies are located indistinguishably in both the field and clusters at high-redshift.

Faculty Host: Lawrence Rudnick

Tuesday, November 21st 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Aaron Breneman, University of Minnesota
Subject: Observations directly linking relativistic electron microbursts to whistler mode chorus: Van Allen Probes and FIREBIRD II

We present observations that provide the strongest evidence yet
that discrete whistler mode chorus packets cause relativistic electron microbursts.
On Jan 20th, 2016 near 1944 UT the low Earth orbiting CubeSat FIREBIRD
II observed energetic microbursts (near L=5.6 and MLT=10.5) from its lower
limit of 220 keV, to 1 MeV. In the outer radiation belt and magnetically conjugate,
Van Allen Probe A observed rising-tone, lower band chorus waves with
durations and cadences similar to the microbursts. No other waves were observed.
This is the first time that chorus and microbursts have been simultaneously observed
with a separation smaller than a chorus packet. A majority of the microbursts
do not have the energy dispersion expected for trapped electrons bouncing between
mirror points. This confirms that the electrons are rapidly (nonlinearly)
scattered into the loss cone by a coherent interaction with the large amplitude
(up to ∼900 pT) chorus. Comparison of observed time-averaged microburst flux
and estimated total electron drift shell content at L=5.6 indicate that microbursts may represent a significant source of energetic electron loss in the outer radiation

12:20 pm:
Speaker: Alexander Kuntsevich, P. N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, Russia
Subject: Spin magnetization and entropy measurements in two-dimensional systems

We apply recharging technique to measure derivatives dS/dn and dM/dn (S and and M are the entropy and the magnetization per unit area, n is the carrier density) in two-dimensional gated systems. In particular, we demonstrate that 2D metal-to-insulator transition is accompanied by formation of spin droplets. We also detect fingerprints of these droplets in transport properties of the system. Entropy measurements reveal signatures of electron-electron interactions in both Fermi liquid (T<< E_F) and correlated plasma (T~E_F) regime. In the quantum Hall effect gaps, entropy decreases significantly. In the Fermi-liquid regime (high densities)S goes to zero as temperature decreases as S \propto T, thus independently checking the 3rd law of thermodynamics.

Wednesday, November 22nd 2017
Speaker: Hajime Muramatsu, University of Minnesota
Subject: Leptonic Decays of Charmed Mesons at BESIII

BESIII now holds the world's largest e+e- annihilation samples taken at Ecm = 3.773 and 4.178 GeV which produce copious charmed mesons, D0, D+, and Ds+. In this talk, I would like to report our on-going studies on D+ -> l nu and
Ds -> l nu (l = mu and tau). These allow us to determine the elements of the CKM matrix within the standard model, to test the unitarity of the second rows of the CKM matrix, probe lepton universality, as well as to calibrate the LQCD calculations of the decay constants, fD(s)+.

Thursday, November 23rd 2017
10:10 am:
Biophysics Seminar in 120 PAN
There will be no seminar this week (Thanksgiving Break)
Speaker: No Journal Club - Thanksgiving holiday
3:35 pm:
Speaker: There will be no colloquium this week due to Thanksgiving

Friday, November 24th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
There will be no seminar this week (Thanksgiving Break)
12:20 pm:
There will be no seminar this week (Thanksgiving Break)
Speaker: No colloquium - Thanksgiving Holiday
There will be no seminar this week (Thanksgiving Break)
4:40 pm:
There will be no seminar this week (Thanksgiving Break)

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