Spring 2016 Seminar
Talks are 12:00 noon on Mondays in Olin Science 268, unless otherwise noted.
February 1, 2016
Eigenstate Thermalization, or Why Statistical Mechanics Works
Abstract: A gas at equilibrium in a container can be
described by its temperature and pressure - two numbers,
even though there are about a trillion trillion particles in
it, each with its own position and velocity. We call this
description the thermodynamic or statistical description and
it works due to the high probability of the gas being in
this state amongst all other states.
“Ergodicity” plays a central role in ensuring
this, and for classical systems can be understood via
chaos. However, quantum systems do not exhibit chaos in the
standard sense, and time evolution is fully reversible. So
how exactly then does a quantum gas forget its initial
conditions and reach a state that can be described by
statistical mechanics? In this talk, we'll set up the
question, and look at a resolution of this problem, which
only became known a little over twenty years ago.
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February 15, 2016
The 2015 Nobel Prize in Physics: The Discovery of Neutrino Oscillations
Abstract: The 2015 Nobel Prize in Physics 2015 was
awarded jointly to Takaaki Kajita and Arthur B. McDonald
“for the discovery of neutrino oscillations, which shows
that neutrinos have mass.” First hypothesized in 1930 by
Wolfgang Pauli, and first detected in 1956, neutrinos barely
interact with other matter, and for many years were
suspected of having no mass. The seeming insignificance of
such a particle is belied by the fact that the 2015 Nobel
prize was the fourth awarded for experimental work on
neutrinos. The work recognized with the most recent prize
dates back to the 1960's when experiments indicated that
there are only about half as many solar neutrinos arriving
on earth as we would expect. This talk will provide some
history of neutrino research, with a specific focus on this
“solar neutrino problem,” a theoretical treatment of
neutrino oscillations, and a survey of more recent
experiments that have shown that neutrinos have non-zero
mass.
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February 29, 2016
“Trash in the Ocean Causes Global Warming” and Other Strange Myths: Adventures in Studying Public Understanding of Science
Abstract: In a democratic society such as ours,
public understanding of science is especially important for
the creation and support of scientifically sound policy. Yet
in society, the media, and even in our own classrooms, we
see examples of poor scientific understanding every
day. This becomes a particularly large problem with
politically charged and potentially catastrophic issues such
as climate change and vaccine safety. In this talk I will
first touch on some of my previous research examining
undergraduate student opinion, knowledge, and understanding
of climate change. I will then move into a discussion of the
work being conducted here at Bucknell with the research
project “The Production of Public Understanding of
Science.” Rooted in recent philosophical work on the
importance of understanding as opposed to knowledge, we
strive in this project to identify the ways in which the
public learns about and understands science, and the ways in
which science can be better communicated, with an emphasis
on how to navigate persistent sociological, political, and
psychological barriers to acquisition.
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March 7, 2016
Quantum Computing and the Taming of Schrödinger's Cat
Abstract: We have blurred the line between physics
and information theory. If a system is both small enough and
isolated enough, it behaves according to the weird laws of
quantum mechanics. One of the beautiful behaviors of a
quantum system is that it can exist in a
“superposition” of multiple discrete states at
the same time. Schrödinger, who didn't much like quantum
mechanics or pets, compared this to a cat both dead and
alive. In the last two decades, physicists, including the
2012 Nobel laureates, have learned to control single atoms
and their quantum nature. The precision of this work is so
superb that we can input, store, process and output these
superpositions at will. The overlap of this language with
computer science is no accident, as the atom provides us
with the ultimate computing platform. The state of these
systems is a piece of information, and by manipulating the
system a calculation is performed.
In this talk we will discuss the fundamentals of quantum
computation, what it can do for us, and what technical
challenges must be overcome. We will discuss the
state-of-the art in quantum computation, in both neutral
atom and ion trap experiments. We use these atomic physics
systems to tame Schrödinger's cat, and to teach it some
great tricks.
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March 28, 2016
Radio Glaciology: A Window into the Physical Processes of Ice Sheets
Dustin Schroeder '07, Department of
Geophysics, Stanford University
Abstract: Radio echo sounding is a uniquely
powerful geophysical technique for studying the interior of
ice sheets, glaciers, and icy planetary bodies. It can
provide broad coverage and deep penetration as well as
interpretable ice thickness, basal topography, and
englacial radio stratigraphy. However, despite the long
tradition of glaciological interpretation of radar images,
quantitative analyses of radar sounding data are rare and
face several technical challenges. These include
attenuation uncertainty from unknown ice temperature and
chemistry, clutter and losses from surface and volume
scattering, and a lack of problem-specific radar
theory. However, there is rich, often underexploited,
information in modern radar sounding data, which is being
collected over terrestrial and planetary ice at an
unprecedented rate. The development and application of
hypothesis-driven analysis approaches for these data can
place observational constraints on the morphologic,
hydrologic, geologic, mechanical, thermal, and
oceanographic configurations of ice sheets and
glaciers. These boundary conditions – and the physical
processes which they express and control – are filling a
fundamental gap our ability to understand and predict the
evolution, stability, and sea level contributions of marine
ice sheets.
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FRIDAY, April 22, 2016
Listening to the Universe with Gravitational Waves
Abstract: This past February, scientists from the
Laser Interferometer Gravitational-wave Observatory (LIGO)
announced they had detected gravitational waves produced by
the collision and merger of two black holes over one billion
years ago. For a brief moment, the energy released by this
event outpaced the combined output of every star in the
visible universe. Despite that tremendous energy, it took an
entirely new type of instrument to detect it; no
conventional telescope could have made this observation.
The historic achievement of LIGO represents more than 40
years of effort to realize a gravitational-wave detector and
the birth of a new kind of astronomy. In this talk, I will
give an overview of this new field: the astrophysical
sources that populate it, existing and planned instruments
for observing them, and the science applications. Particular
emphasis will be given to future space-based gravitational
wave instruments such as the Laser Interferometer Space
Antenna (LISA).
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