THE BOSTON AREA PHYSICS CALENDAR
Week of February 16 - February 22, 1997
 
The Boston Area Physics Calendar is published weekly during 
the academic year by the Department of Physics and Astronomy 
at Tufts University.  You may send your announcements by 
e-mail (bapc@tuhepa.phy.tufts.edu) or FAX:(617-627-3878).  
We cannot accept announcements by telephone.  Entries should 
reach us no later than 11:00am on the Monday preceding the week 
of the event. ENTRIES RECEIVED AFTER THE DEADLINE WILL NOT 
BE PUBLISHED.

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Monday, February 17, 1997
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Monday, February 17, 4:00 p.m.

Worcester Polytechnic Institute
Colloquium 
Olin Hall, Room 107
``Linear Birefringence of Artificial Crystals''
DR. LOK C. LEW YAN VOON
Worcester Polytechnic Institute 
Refreshments will be served in Olin 118 at 3:40 p.m


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Tuesday, February 18, 1997
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Tuesday, February 18,  12:00 p.m. 

Massachusetts Institute of Technology
Seminar on Modern Optics and Spectroscopy 
Marlar Lounge (37-252)
Ronald E. McNair Building
``Making Molecules at MicroKelvin''
WILLIAM C. STWALLEY
University of Connecticut 


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Tuesday, February 18, 3:45 p.m.

Harvard University/The Center for Astrophysics
CfA/Tufts/MIT Joint Cosmology Seminar 
Phillips Auditorium
``A Matter--Antimatter Universe?''
PROFESSOR ANDREW COHEN
Boston University 


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Tuesday, February 18, 3:45 p.m.

Northeastern University
The Center for Interdisciplinary Research on Complex Systems (CIRCS)
CIRCS Seminar 
Dana Research Center, Room 114
``Cellular and Network Oscillations in the Hippocampal Region''
JOHN WHITE
Department of Physiology
Boston University 


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Tuesday, February 18, 4:00 p.m.

Brandeis University
Martin Weiner Lecture Series, Physics Colloquium 
Physics Building, Abelson 131
``Gamma-Ray Astronomy with the Imaging
Compton Telescope (COMPTEL) Aboard the
Compton Gamma-Ray Observatory''
PROFESSOR GREG STACY
University of New Hampshire 
Refreshments in Room 333 at 3:30 p.m.


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Tuesday, February 18, 4:15 p.m.

Massachusetts Institute of Technology
LNS Colloquium 
Kolker Room 26-414
``LSND Neutrino Oscillation Results''
DR. WILLIAM LOUIS
LANL 
Refreshments will be served at 3:45 p.m.


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Wednesday, February 19, 1997
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Wednesday, February 19, 12:15 p.m.

Harvard University
High Energy Physics Seminar 
High Energy Phyics Building, Third Floor Seminar Room
``LNSD Neutrino Oscillation Results''
PROFESSOR WILLIAM C. LOUIS
Los Alamos National Labolatory


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Wednesday, February 19, 4:00 p.m.

Massachusetts Institute of Technology
Physics of Computation Seminar 
Room NE43-518, 545 Technology Square
``Nuclear Magnetic Resonance Spectroscopy: an experimentally
accessible paradigm for quantum computing''

Abstract:

We introduce a new physical mechanism that is capable of computa-
    tion,  namely  Nuclear  Magnetic  Resonance Spectroscopy, or NMR.
    It is based on the fact that the spin 1/2 nuclei of each molecule
    in  a  liquid  sample  are largely isolated from the spins in all
    other molecules. This makes it possible to describe the state  of
    the spins by a reduced density matrix of size 2^n, where n is the
    number of spins in one molecule, rather than 2^N where  N~10^23
    is  the total number of spins in the sample.  It also effectively
    makes each molecule into an independent quantum computer,  with a
    decoherence  time  of  order  seconds.  Finally, by identifying a
    manifold of statistical spin states that transform like true pure
    states,  we  show  that  one  can  utilize quantum parallelism in
    weakly polarized macroscopic liquids. We call a computer based on
    these principles an Ensemble Quantum Computer, or EQC. 

    In this talk we present experimental results that show  how  this
    approach  enables us to easily implement the usual controlled-NOT
    or quantum XOR gate on single states  as  well  as  on  "coherent
    superpositions".  We  also  describe  an  NMR pulse sequence that
    directly implements the universal  Toffoli  gate.  Scaling  these
    experiments  to  molecules with as many as ten inequivalent spins
    is straightforward.  A variety of  experimental  difficulties, in
    particular  the  limited signal-to-noise of NMR experiments, make
    scaling much past ten spins challenging. Nevertheless, the avail-
    ability  of  this  experimentally accessible paradigm for quantum
    computing should be of considerable utility in further developing
    the  theory  and methods that will be needed to solve significant
    problems by either  quantum computing,  or  by  ensemble  quantum
    computing. 

    This is joint work with David Cory, Amr Fahmy and Mark Price.

TIMOTHY F. HAVEL (BCMP)
Harvard Medical School
Refreshments will be served at 3:45 p.m.


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Wednesday, February 19, 4:00 p.m.

University of Massachusetts, Lowell
Spring Colloquia 
Olney 428
``Multiscale Modeling of Solid Plasticity''
PROFESSOR VASILY BULATOV
Massachusetts Institute of Technology
Refreshments will be served at 3:30 p.m.
Contact Prof. Albert Altman [altmana@woods.uml.edu] for more information.


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Wednesday, February 19, 4:30 p.m.

Harvard University
Joint Theory Seminar 
Jefferson 256
``Composite Model Building with Supersymmetry''
DR. MARTIN SCHMALTZ
Boston University


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Wednesday, February 19, 5:00 p.m.

Harvard University/Center for Astrophysics
Joint Atomic Physics Seminar 
Jefferson Laboratory, Room 356
``Atom Interferometers and Atomic Coherence''

Abstract:

Recent experimental demonstrations of optical elements for atoms include
mirrors, lenses and diffraction gratings made from both light and matter,
the latter using nanofabrication technology. Our work in this area has
enabled us to construct a three grating atom interferometer in which the
atom wave is sent on both sides of a stretched metal foil before recombining. 

Atom interferometers can be used to make fundamental tests of quantum
mechanics. We recently studied the loss of atomic coherence due to scattering
a single photon from the atom in the interferometer, then showed how to
regain this coherence by observing only a subset of the scattered atoms. This
showed that the coherence is not truly lost, but only becomes entangled with
the state of the scattered photon by the elastic scattering. This experiment
implies limitations to making interferometers for complex particles that
interact with radiation while in transit through the interferometer. 

Atom interferometers allow qualitatively new and more accurate measurements of
atomic and molecular properties. We put a gas on one side of the foil to
determine the index of refraction of several gases for sodium atom waves.
This gave qualitatively new information about atomic scattering. Recently we
have used this interferometer to conduct similar experiments with sodium
molecules. Putting an electric field on one side of the foil allowed us to
measure the electric polarizability of sodium with unprecedented accuracy. 

Atom interferometers make good inertial sensors as we recently demonstrated
by rotating our interferometer and showing that it detects rotational motion
with the same overall sensitivity as a commercial laser gyroscope.\par

I shall also address the limitations to making interferometers for complex
particles that arise because the particles are bigger than their deBroglie
wavelength, possess many unselected internal states, or are trained to make
measurements while in transit through the interferometer. 

DR. DAVID E. PRITCHARD
Massachusetts Institute of Technology
Tea will be served at 4:30 p.m.


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Thursday, February 20, 1997
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Thursday, February 20, 12:00 p.m.

Harvard University
Colloquium 
Pierce Room 100F
``Alchemy in Two Dimensions: Building a Junction Between 
Distinct Quantum Hall States''
DR. DMITRI CHKLOVSKII
Harvard University


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Thursday, February 20, 4:00 p.m.

Harvard-Smithsonian Center for Astrophysics
Scientific Colloquium 
60 Garden Street (Phillips Auditorium)
``Parsec-Scale Herbig-Haro Outflows from Young Stars''

Abstract:

 Herbig-Haro (HH) objects are collisionally excited nebulae powered
by outflows from young stars.  They have become ``Rosetta stones''
in the study of astrophysical jets and in the investigation of
star formation.  Large format CCDs and IR arrays used on small
telescopes are revolutionizing our understanding of how stars form,
the outflows they produce, and the impact of these flows on the ISM.
Many HH flows have punched out of their host molecular clouds
and are exciting shocks many parsecs from their driving sources.
HH objects provide a fossil record of recent YSO jet ejection velocity
variations, may power the lower velocity bipolar molecular outflows,
may be a major source of turbulence, chemical rejuvenation,
and cloud disruption in the ISM, and an important agent in the
regulation of the gravitational collapse of clouds. 

DR. JOHN BALLY
Center for Astrophysics and Space Astronomy
University of Colorado
Tea will be served at 3:30 p.m.


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Thursday, February 20, 4:00 p.m.

Harvard University
Duality Seminars 
Jefferson 356
``Manifest Electromagnetic Duality in Closed Superstring Field Theory''
PROFESSOR NATHAN BERKOVITS
IFT at University of Estadual Paulista, BRAZIL


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Thursday, February 20, 4:15 p.m.

Massachusetts Institute of Technology
Physics Colloquium 
MIT Room 10-250
``The QCD Vacuum Structure and Phase Transitions''
PROFESSOR EDWARD SHURYAK
SUNY (State University of New York) at Stony Brook and MIT
Refreshments will be served in MIT Room 26-110 at 3:45 p.m.


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Friday, February 21, 1997
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Friday, February 21, 12:00 p.m.

Massachusetts Institute of Technology
NFL Friday Seminar 
MIT room 12-132
``Random Matrix Model for Type-II Superconductors''
DR. SAFI R. BAHCALL
University of California, Berkeley


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Friday, February 21, 2:00 p.m.

Harvard University
Joint Seminar for the History of 20th Century Science 
Science Center, Lecture Room D
(Please note new time and location of meeting)
``The Sokal Affair: A Reassessment''
PROFESSOR ALAN SOKAL, NYU
PROFESSOR EVELYN FOX KELLER, MIT
PROFESSOR PETER GALISON, HARVARD


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Friday, February 21, 2:00 p.m.

Harvard University
Special Theoretical Physics Seminar 
Jefferson Laboratory 356
``What Can We Learn about the Cosmic Microwave Background''
DR. MARTIN WHITE
Enrico Fermi Institute
University of Chicago


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Friday, February 21, 4:00 p.m.

Harvard University
Division of Engineering and Applied Sciences
 Friday Condensed Matter Seminar 
Pierce Hall, Room 209
``Spider Silk: What Accounts for Its Unusual Strength?''
LYNN JELINSKY
Cornell University
Refreshments will be served following the seminar in the 
Brooks Room.
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A Friendly Reminder:

The Deadline for the February 23 - February 29, 1997 Issue is: 

MONDAY, February 17, 1997 at 11:00 a.m.

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