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January 17
Thermal gravity, black holes and cosmological entropy
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Brian Murray
UO Physics Graduate Student
Taking seriously the interpretation of black hole entropy as the
logarithm of the number of microstates, we argue that thermal
gravitons may undergo a phase transition to a kind of black hole
condensate. The phase transition proceeds via nucleation of black
holes at a rate governed by a saddlepoint configuration whose
free energy is of order the inverse temperature in Planck units.
This result was previously obtained by Euclidean path integral
methods. Whether the universe remains in a low entropy state as
opposed to the high entropy black hole condensate depends sensitively
on its thermal history. Our results may clarify an old observation of
Penrose regarding the very low entropy state of the universe.
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January 31
Gravitational Limits on Spontaneous Lorentz Violation and Vector-Tensor Theories
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Alejandro Jenkins
California Institute of Technology
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February 7
Startups for Physicists
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Steve Hsu
ITS
20 years ago research and development was concentrated at
corporate labs like Bell, IBM, Xerox PARC, etc. Today, innovation is more
likely to be found at small, venture capital backed companies founded by
creative risk takers. The odds have never been greater that you, a
scientist or engineer, might someday work at (or found!) a startup
company. This talk is an introduction to this important and dynamic part
of our economy. (Originally presented at the Caltech Entrepreneur's Club.)
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February 21
Dynamical Horizons: a Tool for Studying the Formation of Black Holes
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Jim Isenberg
ITS
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February 28
What do we expect at the LHC?
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Jing Jiang
ITS
As the LHC is coming on-line in less than two years, a lot of excitement
is generated among particle physicists. In this general talk, I will
discuss what questions we expect to answer at the LHC. Will we understand
the electroweak symmetry breaking? Will supersymmetry be found? Or will
anything be found at all? I will also describe how well the LHC answer
these questions and what the signatures of various models might be.
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March 7
Twin Higgs Theories
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Zacharia Chacko
University of Arizona
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March 6-10
UltraMini Workshop on Electroweak Symmetry Breaking
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Click this link for more information
The purpose of the workshop is to bring together a very small number of exceptionally active physicists for a concentrated week of talks, collaboration, and stimulated discussion with each other and with physicists within ITS. By bringing several visiting physicists together at the same time, we expect everyone to benefit from more lively, productive, and extended interactions that are not often possible with regular seminars (and the typical "jet in, jet out" style that has become all so common).
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April 4
Liu-Yau quasi-local mass in spherical gravity
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Niall O'Murchadha
Host: Jim Isenberg
University of Cork
Ireland
Liu and Yau recently introduced a new quasi-local mass in GR. It
is a function on a 2-surface in a 4-manifold. They showed that it was
positive. It is the maximum of the Brown-York energy over all 3-slicings
containing the given 2-surface. The Liu-Yau mass has unpleasant features, it
looks much more like an energy than a mass. In particular it is unboundedly
large on any solution of the Einstein equations, including Minkowski space!
In spherical symmetry, however, it has a natural physical interpretation.
Consider a regular spherical 3-slice filling the interior of the given
2-slice. Take the integral of the energy density of the interior. The
Liu-Yau mass of the boundary is the minimum of this total energy content
over all regular fillings. No other quasi-local mass gives such interior
information.
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April 18
Multi-Electron Collision Dynamics: A Key to Exploring Ionization
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Agapi Emmanouilidou
School of Physics
Georgia Institute of Technology
We explore the role of electron-electron collisions in
multi-ionization
processes using novel classical and semiclassical methods. Our method
gives remarkable agreement with measurements of triple ionization by
single photon absorption in lithium but it also reveals mechanisms: We
find that the four-body Coulomb ionization proceeds through a sequence
of
electron-electron collisions which involve three-body Coulomb
subsystems.
Surprising configurations of three electron escape show up for small
excess energies. We conclude by discussing how our novel classical
methods
can describe multi-ionization in atoms and molecules when driven by
intense ultra short (attosecond) pulses, one of the most exciting
developments in AMO physics in the last years.
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April 25
Surface acoustic wave induced zero resistance states
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Malcolm Kennett
Seminar room: 331 Klamath Hall at 4:00; cookies in 472 Willamette at 3:45.
Physics Department,
Simon Fraser University,
Burnaby, Canada
Recent experiments using microwaves to illuminate high quality two
dimensional electron gases (2DEGs) in a weak magnetic field, have shown
very striking effects: zero resistance states and magnetoresistance
oscillations. I will discuss the related situation when a two dimensional
electron gas is driven by surface acoustic waves (SAWs). SAWs introduce
resistance oscillations due to geometric commensurability as well as
temporal commensurability (as is seen with microwaves). We predict that
SAWs can also give rise to zero resistance states and that the nature of
these states depends crucially on whether the disorder in the 2DEG is
short- or long-range. Finally, I will explore the implications of our
results for current and future experiments on two dimensional electron
gases.
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May 2
Why is finding no jet important?
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Rudi Hwa
ITS
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May 9
Bifurcations in Molecules and Some Analogies with Phase Transitions in Pulsars and Nuclei
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Mike Kellman
Chemistry, UO
I will discuss recent work with V. Tyng on bifurcations in vibrating molecules, with testable consequences called "moment of inertia backbending". Time permitting, I will discuss analogies between bifurcation analysis of dynamical systems, and the Landau theory of phase transitions. I will discuss and analogous backbending effects in two systems: rotating nuclei undergoing phase transitions; and a proposed backbending effect in rotating stars undergoing nuclear-quark matter transition.
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May 16
Continuous transition between two meta-stable states in the ferromagnetic phase
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Leiming Chen
UO
I will talk about a ferromagnet in an anisotropic system, i.e. the
underlying crystal field. It is shown that by applying and varying
an external field to such a system can create a continuous transition
between two meta-stable states in the ferromagnetic phase. The
critical behavior of this transition is found to be in the
universality class of the XY model.
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May 18
The ILC: A Detector Physicist Describes Accelerator Physics to Theorists
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George Gollin
Joint HEP/ITS seminar (host: Jim Brau)
time: 12:00 - 1:30pm
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May 30
On the origin of probability in quantum mechanics
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Steve Hsu
U of O
Attempts to derive the Born rule, either in the Many Worlds
or Copenhagen interpretation, are unsatisfactory for systems with only
a finite number of degrees of freedom. In the case of Many Worlds this
is a serious problem, since its goal is to account for apparent
collapse phenomena, including the Born rule for probabilities,
assuming only unitary evolution of the wavefunction. For finite number
of degrees of freedom, observers on the vast majority of branches
would not deduce the Born rule. However, discreteness of the quantum
state space, even if extremely tiny, may restore the validity of the
usual arguments.
This talk should be accessible to anyone with a basic understanding of
quantum mechanics.
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June 6
Monte Carlo Event Generators
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Philip Stephens
High Energy Physics Group
Cambridge University
Cambridge, UK
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August 9
Searching for micro-black holes at the LHC
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Roberto Casadio
Special time: 2:00 PM
INFN
Abstract: In models with extra spatial dimensions the fundamental scale of gravity could be as low as 1TeV and black holes may then be produced at the LHC. I will give a somewhat critical overview of theoretical issues involved in the phenomenological description of their detection and conclude by showing some possible modifications induced by quantum gravity effects near the fundamental scale of gravity.
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September 26
The quest for a proof of Poincare's conjecture
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Jim Isenberg
ITS
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October 3
Emergent Photons and Landau Forbidden Transitions in Quantum Magnets
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Ashvin Vishwanath
Condensed Matter Theory Group
Dept. of Physics
University of California, Berkeley
Host: Belitz
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Oct 10
How to build an ion-trap quantum computer that factors a 128-bit number in a day
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Steven van Enk
Department of Physics
University of Oregon
I'll discuss what it takes to build a quantum computer. Starting from the basics I'll explain quantum error correction, fault-tolerant quantum computing, and how quantum communication between distant qubits is needed as well.
I'll end with a discussion of an architecture for a large-scale ion-trap quantum computer.
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October 17
What is the Nature of Cosmic Singularity?
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Adam Clausen
Doctoral Student, ITS
Abstract:The singularity theorems of Hawking state that generic spacetimes will have a singularity.
The exact nature of this singularity is unknown, yet there exist unproven conjectures that aim to answer this question.
I'll report on analytic progress to prove these conjectures in model spacetimes.
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October 24
Quasiclassical Approximations for the Modes of Weakly Perturbed Systems
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Romanas Narevich
NeoPhotonics Corporation
San Jose, CA
Special quantum states exist which are quasiclassical quantizations of regions of phase space that are weakly chaotic. In a weakly chaotic region, the orbits are quite regular and remain in the region for some time before escaping and manifesting possible chaotic behavior. Such space regions are characterized as being close to periodic orbits of an integrable reference system. The states are often rather striking, and can be concentrated in spatial regions. I will review some methods to characterize such regions and find analytic formulas for the special states and their energies.
Host: Jens Nöckel
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October 31
Global Warming: Fact or Fiction
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Greg Bothun
Department of Physics, UO
This talk will focus on a) theoretical expectations involving changing
atmospheric greenhouse gas concentrations and climate forcing;
b) whether or not a data-driven case can really be made that climate
change is upon us and c) the physical plausibility that non-linear
tipping points exist in the coupled ocean-atmosphere climate system.
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November 14
Transport Properties of Correlated Electrons in Ultra High Magnetic Fields
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Ronjay Saha
Postdoctoral Fellow
University of Oregon
The effective dimensionality of charge carriers in a bulk metal may be reduced from 3D to 1D by applying a strong magnetic field.
It has recently been shown that this reduction leads to the formation of a strongly correlated state, which shows Luttinger liquid like behavior.
This effect is most pronounced in the ultra-quantum-limit (UQL) when only the lowest Landau level remains occupied.
In this talk I will discuss the effect of dilute impurities on the transport properties of this system. In the first part of the talk I will show
that the localization behavior for this system is "intermediate" between a 3D and a 1D system. In the second part I will discuss
the electron-electron interaction corrections to the conductivity, which in UQL exhibits power law scaling with temperature with a field dependent exponent.
Finally if time permits I will show some recent experiments on graphite which can be qualitatively understood using the above theory.
However the finer details of the experimental results are not captured within the above theory.
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November 21
Multi-electron collisions on an attosecond time scale in photoionization processes:
from three to four electron escape
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Agapi Emmanouilidou
ITS
We have recently developed a classification scheme that groups the paths the three electrons in the ground state of lithium follow to escape to the
continuum when a single photon is absorbed. These collision sequences occur at an attosecond time scale and thus with the advancement of ultra short laser pulses we should be able to observe them experimentally. How
general is this collision scheme? Our current studies on four electron escape by single photon absorption aim to answer that question.
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Jan 23
Genetic Algorithms and Co-Evolutionary Computing
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Melanie Mitchell
Portland State University and Santa Fe Institute
Abstract:
Genetic algorithms (GAs) are a class of machine learning methods based on ideas from natural genetics and evolution. Applications of GAs range from automated engineering design and prediction to modeling of evolutionary processes. In this talk I will introduce genetic algorithms and their applications, and will talk in detail about my own research on designing "cellular array" architectures for decentralized, distributed computing. I will also describe a variation of genetic algorithmsuss these results and our investigations into the reasons for the striking success of co-evolution.
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Feb 13
Voids of Dark Energy
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Sourish Dutta
Abstract:
The present-day acceleration of the Universe is one of the greatest mysteries of modern cosmology. In the framework of general relativity, the expansion could be caused by either a "cosmological constant", or a dynamical dark energy component (DDE). In this talk I will describe a novel theoretical approach to distinguishing between these two possibilities, namely, via the clustering properties of DDE. By following the dynamical evolution of matter perturbations in a cosmic mix of matter and DDE, we find the very interesting result that the DDE tends to form voids in the vicinity of gravitationally collapsing matter. I will discuss these voids in detail, in particular the physics behind their formation and possible observational implications.
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Feb 20
Breaking news about radiating black holes
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Piero Nicolini
University of Trieste
Abstract:
Black holes are conventionally defined as objects with a gravitational field so powerful that even electromagnetic radiation cannot escape their pull. Against this classical background, there is the quantum mechanical description for which black holes can emit radiation. This gives black holes a central role in different fields of physics, including, not only General Relativity, but also Quantum Field Theory and Thermodynamics. The understanding of black hole physics is also a key knowledge to test Planck scale physics and the onset of quantum gravity. To this purpose, a new approach to black hole physics has been recently proposed and some of the new intriguing features are presented.
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Feb 27
Minimal surfaces in Riemannian and Lorentzian Geometry
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Paul Allen
Department of Mathematics
University of Oregon
Abstract:
The Minimal Surface Problem is perhaps the oldest problem in Geometric
Analysis, dating back to work in 1849 of the Belgian physicist J.
Plateau, whose name is associated with the problem. In its simplest
form, the classical Plateau Problem asks if a given closed curve can be
realized as the boundary of a surface which is stable with respect to
area. I will discuss the variational approach to this problem, which
was resolved 3D Euclidean space by Douglas-Rado in the 1930's. I will
then discuss some natural generalizations of this problem in Riemmanian
and Lorentzian geometries, concluding with remarks about some recent
work of J. Isenberg, L. Andersson, and myself.
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Mar 6
New topological phases in quantum mechanics
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Roman Buniy
ITS
Abstract:
Gaussian linking of a semiclassical path of a charged particle with a magnetic flux tube is responsible for the Aharonov-Bohm effect, where one observes interference proportional to the magnitude of the enclosed flux. We construct quantum mechanical wave functions where semiclassical paths can have second order linking to two magnetic flux tubes, and show there is interference proportional to the product of the two fluxes. It is straightforward to generalize this idea to higher order linkings. Such effects are due to nonuniqueness of the action in classical mechanics, where an infinite sequence of higher order topological terms is allowed.
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Mar 13
Measuring Dark Energy with Quasar Pairs
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Chris Impey
Dept. of Astronomy
University of Arizona
Abstract:
Dark energy is the largest and most mysterious component of the
universe, driving the accelerating expansion but representing new
and unknown microscopic physics. A new approach to measuring dark
eneegy is presented based on observations of quasar pairs as probes
of the z = 2 intergalactic medium. The test is purely geometric and
unlike the case of supernovae, does not require any assumptions about
standard candles or evolution. Early resultsindicate consistency with
the expectations of the "concordance"cosmology.
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Mar 20
AdS/CFT
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SJ Sin
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April 10
From Brownian motion to elliptic flow: the conflict continues 100 years
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Tom Trainor
brown bag lunch, 12:30 pm
University of Washington
Abstract:
100 years ago Einstein and Perrin provided convincing evidence for
molecular matter based on the study of Brownian motion. Their triumph
ended a long period of intense conflict between "continuists" such as
Mach and Ostwald and "discontinuists," particularly Boltzmann, about
the structure of ordinary matter. Today, the RHIC heavy ion facility at
Brookhaven National Laboratories has been used to create a new form of
matter in which QCD quarks and gluons are temporarily liberated from
hadrons. An azimuthal correlation structure called elliptic flow has
been used to claim certain hydrodynamic properties for this "quark
matter," that it approximates a "perfect liquid" with hypothesized
connection to string theory and duality. But is that "continuist"
conclusion justified? I will present detailed parallels between the
two problems and show how the novel mathematical techniques developed
to describe Brownian motion are also essential for heavy ion
collisions. Surprising new results emerge that may mirror the
conceptual transition in 1905-09.
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May 1
Introducing Mathematica 6.0
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Oyvind Tafjord
Institute of Theoretical Science and Wolfram Research, Inc
Abstract:
I will give an overview of the major new version of Mathematica about to be released. The talk will be aimed both at new and old users of Mathematica, emphasizing ways in which it can be useful in everyday research and teaching. Version 6.0 includes several revolutionary new features, from interactive dynamical results and greatly improved graphics to load-on-demand real-world data. The range of tasks that can be done in Mathematica 6.0 is quite astounding, so I invite everybody to come and be amazed.
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May 15
What does the field look like inside your laser? General theory for multi-mode open cavities
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A. Douglas Stone
Joint seminar with Oregon Center for Optics
Yale University
Department of Applied Physics
Abstract:
There is great current interest in novel lasing structures based for example on micro-cavities, random media, quantum dots or photonic bandgap defect states. In these systems the passive cavity resonances are often complex and how they relate to the actual non-linear lasing modes is unclear. In fact there is little theory even of conventional multi-mode lasing above threshold where spatial hole burning and mode-mode interactions are important. Recently we have developed an appropriate “ab initio” theory for treating these non-linear effects to all orders within a self-consistent treatment of the Maxwell-Bloch equations for an open cavity. The theory allows us to predict the emission pattern and output power of the lasing mode(s) far above threshold. The appropriate basis to use is the biorthogonal solutions of the passive cavity with only outgoing waves at infinity, and a general lasing mode is a superposition of these and not described by a single cavity resonance as is usually assumed. Applications of this theory to standard edge-emitting lasers and to random lasers will be discussed. The theory should be useful in designing laser cavities with desirable modal and emission properties.
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May 29
Theoretical models to bridge time (length) scales in polymer dynamics
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Marina G. Guenza
UO Chemistry
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June 5
Stalking the Lipid “Raft”: Thermodynamics and Phase Behavior of Model Lipid Bilayers
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Marcus Collins
Dept. of Chemistry
University of Washington
Abstract:
While biologists have accumulated substantial evidence suggesting that lipids and proteins in cell membranes laterally segregate on the scale of ten to one hundred nanometers, it has never been fully clear what physical mechanisms lead to such separation, or even whether it is possible. Biophysicists have focused on the equilibrium coexistence of liquid phases in these two dimensional membranes, but as of yet have failed to connect these studies to the biological “raft” which must have somewhat different properties. Among other things, these “rafts” would need to form in a lipid bilayer whose sides are not constructed from the same lipids. Model studies have shown that bilayers formed of lipids from the outer half of cellular bilayers tend to self-segregate, while those formed from lipids of the inner half do not. Thus, we have a theoretically simple but experimentally challenging question: when we form a bilayer whose two halves are chemically distinct, what happens? After reviewing the history of the problem, I will discuss recent experiments in which I have shown that the interactions between the two halves of the bilayer are very strong, giving rise to novel phase behavior not seen in symmetric bilayers. I will briefly discuss current projects to determine the nature of this interaction. Finally, I will discuss the prospects of equilibrium phase separation and our lab’s most recent studies of critical phenomena in lipid membranes to understand what is possible—and what isn’t—in the cell.
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July 12
Matter under free-electron laser light
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Jan M. Rost
Location: 240 Willamette (OCO)
Max Planck Institute for the Physics of Complex Systems
Dresden, Germany
Novel light sources, the X-ray free electron lasers
being built at SLAC in Stanford and at DESY in Hamburg,
will provide light pulses with properties of lasers and synchrotrons
at the same time: short in duration and wavelength, coherent and
extremely bright.
Understanding the coupling of light and matter in this new parameter regime
is only at its infancy. Starting from a perspective of strong laser pulses
at infrared frequencies, the talk will discuss pulses of successively
shorter wavelength and introduce the mechanisms how they interact with rare
gas clusters. Thereby, first experiments from the free electron laser in
Hamburg will be interpreted.
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9/25
Continued fractions and local densities of states
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Chris Nex
Cambridge University
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10/02
Interpretation of Quantum Mechanics, PART 1
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John Sipe
3:30 to 5:30 pm, WIL 240
Toronto
Prof. Sipe will give two lectures of two hours each on the interpretation of quantum mechanics. They are especially designed to be of interest to graduate students.
These lectures are sponsored by the graduate students seminar, ITS, and OCO.For the abstract, see the following entry.
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10/03
Interpretation of Quantum Mechanics, PART 2
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John Sipe
3:30 to 5:30 pm, WIL 240
Department of Physics
University of Toronto
Introduction
"Philosophy 101"
Operational quantum mechanics
Realist talk
Hidden variable theories I: von Neumann's "proof"
Hidden variable theories II: Contextuality
Orthodoxy
The decoherence strategy
Copenhagen quantum mechanics
Addendum: Bell's inequalities
Bohm-deBroglie quantum mechanics
Relative state interpretations
Modal interpretations
Consistent histories quantum mechanics
Collapse theories
Wrap-up
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10/09
Cold atom physics
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Thomas Pattard
Physical Review A
Abstract:
Recent advances in trapping and cooling of neutral atomic gases have permitted
achieving ultralow temperatures far below 1K. With this, a wealth of new
research fields has opened up, not at all limited to the realization of Bose
Einstein condensation and related questions. In this talk, I will introduce
one of these research topics, namely the physics of ultracold neutral
plasmas and Rydberg gases.
The fact that ultracold plasmas are many orders of magnitude colder than
"conventional" plasmas leads to some remarkable properties, akin to conditions
realized in exotic astrophysical environments. Rydberg gases, on the other hand,
are closely related not only experimentally but also, as it turns out, conceptually.
In addition, they are of significant current interest because of the possibility
to study strongly interacting many-body systems in a highly controllable and
customizable environment, and because of potential applications in quantum
information processing schemes.
A theoretical description of these systems relies on methods and concepts from various
fields of physics, from plasma physics over atomic physics, nonequilibrium thermodynamics
to condensed matter physics. On the other hand, this also means that the study of cold
plasmas and Rydberg gases can provide new stimulus for all of these fields.
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10/10
Editors are from Mars, Referees are from Venus, and Authors are from Earth
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Thomas Pattard
4 pm Wednesday
Physical Review A
Abstract:
When you try to publish your work in a peer-reviewed journal such as the Physical Review, it often appears that editors, referees and authors all speak different languages and pursue different goals (a ``me versus them'' feeling). Indeed, the pressure to ``publish or perish'' in the modern academic world sometimes seems incompatible with the idea of conveying actual and useful information to the reader of a journal, who wants to stay up-to-date with current developments in her/his field of interest. On the other hand, a significant part of this feeling is rooted in miscommunication that could easily be avoided by a better mutual understanding of the needs of authors, referees, editors and readers.
In this talk, I will try to give some insight into the publishing process from the perspective of an editor. I will give a short overview of APS publishing, and the workflow associated with the handling of a typical manuscript. This will lead us to the question of what we are looking for in a paper / referee report / cover letter, and how the communication between all involved parties can be improved. Using examples from actual communication we receive, I will try to give a few hints that might actually make you a better author and/or referee. On the other hand, editors are aware of the fact that all parties involved in this process are less than perfect, and I expect you to try to make us ``good'' editors. After the talk, I will be open to any criticism or suggestions you might have to improve the relationship between authors and editors, and the quality of our journals.
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10/16
Quantum Fields on the Moyal Plane
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A.P. Balachandran
Syracuse University
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10/23
Curved space, monsters and black hole entropy
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Steve Hsu
ITS
Abstract:
We use curved space to construct objects of extremely high entropy —
potentially higher than that of a black hole of equal mass. Due to
their pathological properties, we refer to these objects as monsters.
However they seem to be legitimate physical configurations and should
be part of the Hilbert space of gravity. Our results suggest that the
relation between black hole entropy and the number of microstates of
the hole is more subtle than perhaps previously appreciated.
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10/30
Parton showers with quantum interference
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Dave Soper
ITS
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11/06
Liquidity traps, learning, and stagnation
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George Evans
UO Dept of Economics
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11/20
Disentangling the Strong Interactions in Quark Jets
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Christopher Lee
U.C. Berkeley
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11/27
How I Learned to Stop Worrying and Love Photon Wave Mechanics
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Michael Raymer
Oregon Center for Optics
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April 8
Solubility
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Bob Mazo
ITS
Abstract:
To clarify the title: this talk will not deal with the solution of equations but with phenomena like "What happens when you put sugar in your coffee?" I shall talk primarily about the salting out effect, the decrease (usually) of the solubility of a solute in a solvent when a third component is added. After a brief discussion of the physical factors affecting solubility, I shall discuss a formal theory of the salting out effect,based on the fluctuation theory of solutions. Then I shall indicate how application of this formal theory to experimental rresults enables one to draw conclusions about the microscopic structure of a solution. If time permits, I shall discuss what happens when the system is near the critical point of the solvent, where fluctuations are very large.
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April 15
Glauber, Einstein, and Bohr-Kramers-Slater: Old Wine, New Bottle
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Howard Carmichael
Physics Colloquium
University of Aukland
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April 22
Maximum Entropy and Maximally Broken Time-Reversal Symmetry
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Roger Haydock
ITS
Getting the most out of moments
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April 29
Wheeler, Einstein, and Mach's Principle (with an experimental test of Mach's Principle)
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Jim Isenberg
ITS
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May 6
Protein local dynamics
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Marina Guenza
ITS
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May 20
Heat content and heat trace asymptotics with singular initial temperature distributions
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Peter Gilkey
ITS
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May 27
WMAP 5 Year Data Analysis: What is New?
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Greg Bothun
331 Klamath Hall
UO Physics
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July 8
GRAVITATIONAL VACUUM ENERGY IN OUR RECENTLY ACCELERATING UNIVERSE
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Sidney Bludman
Friday 4pm
Departamento de Astronomia
Universidad de Chile
Santiago, Chile
Abstract:
We review current observations of the homogeneous cosmological expansion history which, because they measure only kinematic variables, cannot determine the dynamics driving the recent accelerated expansion. The minimal fit to the data, the flat L CDM model, consisting of cold dark matter and a cosmological constant, interprets 4 L geometrically as a classical spacetime curvature constant of nature, avoiding any reference to quantum vacuum energy. (The observed Uehling and Casimir effects measure forces due to QED vacuum polarization, but not any quantum material vacuum energies.) An Extended Anthropic Principle, that Dark Energy and Dark Gravity be indistinguishable, selects out flat L CDM. Prospective cosmic shear and galaxy clustering observations of the growth of fluctuations, in principle, will test whether 'dark energy' is static or moderately dynamic and distinguish Dark Energy from Dark Gravity.
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