Physics and Astronomy Calendar

Week of Monday, September 25th 2017

Tuesday, September 26th 2017
4:30 pm:
See Joint Quantum Materials & Condensed Matter Seminar on Thursday this week only.

Wednesday, September 27th 2017
Speaker:  Peter Abbamonte, University of Illinois, Urbana-Champaign
Subject: Bose condensation of excitons in a transition metal dichalcogenide

Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have been predicted to condense into either a superfluid or an insulating electronic crystal. But definitive evidence for a thermodynamically stable exciton condensate has never been achieved. In this talk I will describe our use of momentum-resolved electron energy-loss spectroscopy (M-EELS) to study the valence plasmon in the transition metal dichalcogenide semimetal, 1T‐TiSe2. Near the phase transition temperature, TC = 190 K, the plasmon energy falls to zero at nonzero momentum, indicating dynamical slowing down of plasma fluctuations and crystallization of the valence electrons into an exciton condensate. At low temperature, the plasmon evolves into an amplitude mode of this electronic crystal. Our study represents the first observation of a soft plasmon in any material, the first definitive evidence for exciton condensation in a three-dimensional solid, and the discovery of a new form of matter, “excitonium.”

Faculty Host: Martin Greven
7:00 pm:
2017 Misel Lecture in Memorial Hall, McNamara Alumni Center
Speaker: Wendy L. Freedman

Over the past few decades, astronomers have for the first
time identified the major constituents of the universe.
Unexpectedly, the universe hardly resembles what we
thought only a couple of decades ago. The universe is filled
with dark matter more abundant than ordinary matter and
dark energy that is causing a runaway acceleration. Theory
is not yet able to explain this unexpected universe. New
giant telescopes planned for the next decade are likely to
reveal more surprises. In her lecture, Professor Freedman
will describe these recent advances.

Thursday, September 28th 2017
08:00 am:
Untitled in Physics
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: Dr. Tejas M Gupte, University of Minnesota
Subject: To be announced.
Speaker: Matt Gomer
3:35 pm:
Speaker: Wendy Freedman, University of Chicago
Subject: A New Calibration of the Hubble Constant
Fall 2017 Misel Lecturer

The accuracy with which we can measure the Hubble
constant, Ho has been steadily increasing over the past
decade. The direct and traditional means to measure Ho
is based on measurement of distances and velocities to
galaxies in the local universe; for example, using Cepheid
variables and Type Ia supernovae. A model-dependent
Ho can be inferred from applying a cosmological model
to measurements of anisotropies in the cosmic microwave
background. Recently, these two precise techniques have
yielded values of Ho that disagree at more than 3-sigma.
This disagreement may be signaling errors in one or both
techniques. Alternatively, it could be signaling new physics
not currently included in the standard model of cosmology.
The Chicago-Carnegie Hubble Program is undertaking a
completely independent calibration of the Hubble constant
using red giant stars in the nearby universe. These stars
are proving to be both more precise and more accurate
than the traditional Cepheid variables. Moreover, with
the imminent launch of the James Webb Space Telescope
and new geometric parallaxes measured by Gaia, they will
provide a means of extending the distance scale beyond
the realm of Cepheids, and for measuring Ho to both a
precision and accuracy of 1%.

Friday, September 29th 2017
10:10 am:
Nuclear Physics Seminar in Tate 301-20
Subject: Organizational Meeting
Speaker: Kiel Howe (Fermilab)
Subject: TBA
Speaker: No colloquium this week
Subject: See the Misel lecture information for September 27th
Speaker: Amy Bix, Department of History - Iowa State University
Subject: Inviting Girls Into the Lab: the Rise of Diversity Advocacy in STEM, 1950-Present
Refreshments served at 3:15 p.m.

One of the biggest transformations in modern science and engineering isn't a particular discovery, invention, or technique, but a revolution in assumptions about who can and should enter those disciplines. For years, American efforts focused on steering more young white men into science and engineering. By the mid-1950s, some scientists and engineers began programs to open opportunities to broader groups of youngsters. Their advocacy fostered wide-ranging campaigns to expand STEM opportunities for K-12 female students, which came to command major support from scientific and technical organizations, corporations, government, community groups, educators, even celebrities. This talk explores when, how, and why evolving ideas about gender roles, education, and the nature of STEM generated the modern movement for STEM diversity and outreach.

4:40 pm:
Speaker: Yong-Zhong Qian, University of Minnesota
4:40 pm:

Saturday, September 30th 2017
12:00 pm:
School Picnic in Boom Island Park Shelter B

All members of the School and their families are invited to join a picnic at Boom Island Park Shelter B. I will also be sending out another reminder email to the department this week, but figured it couldn't hurt to try and get as much ad space as we can!

You can sign up for the picnic here.

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