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BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170728T165201Z
DTSTART:20170801T193000Z
DTEND:20170801T203000Z
UID:event1775@bu.edu
URL:http://physics.bu.edu/events/show/1775
SUMMARY:Investigating Effects of Morphology and Flagella Dynamics on Swimmi
ng Kinematics of Different Helicobacter Species Using Single Cell Imaging
DESCRIPTION:Featuring Maira Constantino\n\nPart of the PhD Final Oral Exams
.\n\nExamining Committee: Rama Bansil\, Shyam Erramilli\, Kirill Korolev\,
Karl Ludwig\, Kevin Black\n\nAbstract:\n\nThis work explores the effects o
f body shape and configuration of flagella on motility of Helicobacter pylo
ri\, a helical-shaped bacterium that inhabits the viscoelastic gastric muco
sa and causes gastritis\, ulcers and gastric cancer. Although it is well kn
own that different shapes produce different hydrodynamic drag thus altering
the speed and that helical shapes generate additional thrust this has not
been quantitatively established for flagellated bacteria. Using fast time-r
esolution and high-magnification two-dimensional phase-contrast microscopy
to simultaneously image and track individual helical-shaped H. pylori and i
ts rod-shaped isogenic mutant in broth and mucin solutions\, the shape as w
ell as rotational and translational speed can be determined. Henry Fu and M
ehdi Jabbarzadeh used the experimental data to validate the method of regul
arized Stokeslets by directly comparing the observed speeds to numerical ca
lculations. The results show that due to relatively slow body rotation rate
s\, the helical shape makes at most a 15% contribution to speeds. In order
to explore the effects of flagella configuration on motility\, three membe
rs of the Helicobacter species were examined: H. suis (bipolar\, multiple f
lagella)\, H. cetorum (bipolar\, single flagellum) and H. pylori (unipolar\
, multiple flagella). Due to the large number of flagella in each pole\, th
e flagellar bundle of H. suis could be visualized while it swam in broth an
d mucin. Results show that regardless of media\, the flagella bundles can a
ssume one of two configurations interchangeably: extended away from the bod
y or wrapped around it. H. suis predominantly swims with the lagging flagel
la extended behind the body and the leading flagella wrapped around it\, bu
t cases where both bundles are extended or both are wrapped have also been
observed. Using the same experimental technique described earlier\, the res
ults show that bipolar bacteria gain a speed advantage over unipolar bacter
ia. In addition\, the effects of pH on motility of H. suis in broth and muc
in were investigated. Similarly to previous findings on H. pylori\, the res
ults show that H. suis swims faster in mucin than broth at same pH and that
it stops swimming in mucin at pH4 due to gelation.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170801T174843Z
DTSTART:20170808T190000Z
DTEND:20170808T200000Z
UID:event1780@bu.edu
URL:http://physics.bu.edu/events/show/1780
SUMMARY:Pseudoparticle approach to strongly correlated systems
DESCRIPTION:Featuring Garry Goldstein\n\nPart of the Condensed Matter Theor
y Seminar Series.\n\nIn the ﬁrst part we present a slave-particle meanﬁ
eld study of the mixed boson+fermion quantum dimer model introduced by Punk
\, Allais\, and Sachdev [PNAS 112\, 9552 (2015)] to describe the physics of
the pseudogap phase in cuprate superconductors. Our analysis naturally lea
ds to four charge e fermion pockets whose total area is equal to the hole d
oping p\, for a range of parameters consistent with the t−J model for hig
h temperature superconductivity. Here we ﬁnd that the dimers are unstable
to d-wave superconductivity at low temperatures. The region of the phase d
iagram with d-wave rather than s-wave superconductivity matches well with t
he appearance of the four fermion pockets. In the superconducting regime\,
the dispersion contains eight Dirac cones along the diagonals of the Brillo
uin zone. \n\nIn the second part we present an approach for studying system
s with hard constraints such that certain positive semideﬁnite operators
must vanish. The diﬃculty with mean-ﬁeld treatments of such cases is th
at imposing that the constraint is zero only in average is problematic for
a quantity that is always non-negative. We reformulate the hard constraints
by adding an auxiliary system such that some of the states to be projected
out from the total system are at ﬁnite negative energy and the rest at
nite positive energy\, we dubbed this method the soft constraint. This au
xiliary system comes with an extra coupling that we are free to vary and th
at parametrizes a whole family of mean-ﬁeld theories. We argue that this
variational-type parameter for the family of mean-ﬁeld theories should be
ﬁxed by matching a given experimental observation\, with the quality of
the resulting mean-ﬁeld approximation measured by how it ﬁts other data
. We test these ideas in the well-understood single-impurity Kondo problem\
, where we ﬁx the parameter via the TK (Kondo temperature) obtained from
the magnetic susceptibility value\, and score the quality of the approximat
ion by its predicted Wilson ratio. We also study a continuum version of the
soft constraint method. To show its usefulness we study the Laughlin fract
ional quantum Hall states at ﬁlling fraction ν = 1 2m+1. We produce the
Landau Ginzburg Cherns Simons theory for hard core bosons(arising in this f
ormulation of the Laughlin functions0 for these ﬁlling fractions. We hand
le the hard core constraint explicitly and show that to leading order it is
equivalent to a theory of soft core bosons with an eﬀective density dens
ity interaction between the particles of the form of a Coulomb interaction
coming from the electrons in the original theory and an eﬀective interact
ion coming from the hard core constraint that can be tuned by hand which we
denote by λ(q\,ω). We show that we can use this eﬀective interaction t
o reproduce the known spectra of both inter Landau level and intra Landau l
evel neutral excitations for the Laughlin states as well as the energy gap
to charged excitations and the electromagnetic response tensor.
LOCATION:SCI SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170801T175116Z
DTSTART:20170810T150000Z
DTEND:20170810T160000Z
UID:event1781@bu.edu
URL:http://physics.bu.edu/events/show/1781
SUMMARY:The many body localization transition: A dynamical phase transition
triggered by a quantum avalanche
DESCRIPTION:Featuring Marcus Muller\, Paul Scherer Institute\, Villigen Swi
tzerland\n\nPart of the Condensed Matter Theory Seminar Series.\n\nI will r
eview recent progress on the understanding of many-body localization\, i.e.
\, the phenomenon of absence of thermalization in interacting\, disordered
quantum systems. After discussing the restricted domain of existence of str
ict many body-localization and the role of rare events\, I will present a r
eal space renormalization group analysis which offers a microscopic scenari
o for the unusual dynamical phase transition which occurs as a localized sy
stem is tuned into an ergodic regime. While the transition is associated wi
th a diverging time scale for thermalization\, most spatial correlators rem
ain short range at the critical point. The latter goes hand in hand with th
e discontinuous evolution of expectation values of local observables. These
features distinguish the transition sharply from standard critical phenome
na.
LOCATION:SCI SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170724T132556Z
DTSTART:20170811T161500Z
DTEND:20170811T181500Z
UID:event1779@bu.edu
URL:http://physics.bu.edu/events/show/1779
SUMMARY:Statistical Physics\, Financial and Complex Systems and Networks
DESCRIPTION:Featuring Asher Mullokandov\n\nPart of the PhD Final Oral Exams
.\n\nExamining Committee: H.E. Stanley\, William Skocpol\, Kirill Korolev\,
Irena Vodenska\, Raj Mohanty
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170814T133931Z
DTSTART:20170816T150000Z
DTEND:20170816T160000Z
UID:event1783@bu.edu
URL:http://physics.bu.edu/events/show/1783
SUMMARY:Entanglement entropy of finite-temperature pure quantum states and
thermodynamic entropy as a Noether invariant
DESCRIPTION:Featuring Sho Sugiura\, University of Tokyo\n\nPart of the Cond
ensed Matter Theory Seminar Series.\n\nEntropy is a fundamental concept in
statistical mechanics. In this talk\, I investigate two aspects of entropy.
First\, we reveal a universal behavior of entanglement entropy of the pure
quantum states which are in thermal equilibrium states. Second\, we charac
terize thermodynamic entropy as a Noether invariant under a non-uniform tim
e translation. \n\nIn the first part\, we focus on the size dependence of t
he entanglement entropy of the pure quantum states which can fully describe
thermal equilibrium as long as one focuses on local observables. The therm
odynamic entropy can also be recovered as the entanglement entropy of small
subsystems. When the size of the subsystem increases\, however\, quantum c
orrelations break the correspondence and mandate a correction to this simpl
e volume-law. The elucidatione of the size dependence of the entanglement e
ntropy is thus of essential importance in linking quantum physics with ther
modynamics\, and in analyzing recent experiments on ultra-cold atoms. In th
is talk\, we derive an analytic formula of the entanglement entropy for a c
lass of pure states called cTPQ states representing thermal equilibrium. We
find that our formula applies universally to any sufficiently scrambled pu
re state representing thermal equilibrium\, i.e.\, general energy eigenstat
es of non-integrable models and states after quantum quenches. Our universa
l formula can be exploited as a diagnostic tool for chaotic systems; we can
distinguish integrable models from chaotic modelsand detect many-body loca
lization with high accuracy. \n\nIn the second part\, we investigate a ther
mally isolated quantum many-body system with an external control represente
d by a time-dependent parameter. We formulate a path integral in terms of t
hermal pure states and derive an effective action for trajectories in a the
rmodynamic state space\, where the entropy appears with its conjugate varia
ble. In particular\, for quasi-static operations\, the symmetry for the uni
form translation of the conjugate variable emerges in the path integral. Th
is leads to the entropy as a Noether invariant.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170816T125347Z
DTSTART:20170817T190000Z
DTEND:20170817T200000Z
UID:event1776@bu.edu
URL:http://physics.bu.edu/events/show/1776
SUMMARY:Continuum limits of Quantum Walks
DESCRIPTION:Featuring Michael Manighalam\n\nPart of the Preliminary Oral Ex
am.\n\nExamining Committee: Mark Kon\, Alex Sushkov\, Chris Laumann\, Claud
io Rebbi\n\n\nThe quantum analog of a random walk is known as the quantum w
alk. Just as random walks have been used in computer science\, quantum walk
s have been used in many areas of quantum computing. Quantum walks have bee
n shown to match the Grover’s search algorithm speedup over classical ora
cle search algorithms\, to provide exponential speedup compared to any clas
sical algorithms in various graph traversal problems\, and more generally t
o be universal quantum computational primitives. \n\nTwo-state quantum walk
s exist as canonical discretizations of the Dirac equation\, as demonstrate
d originally by Feynman; these walks can be shown rigorously to recapture t
he Dirac equation in their continuum limit. Since their original use\, much
work has been done investigating the properties of continuum limits of qua
ntum walks. The goal of my PhD research is to address the question of wheth
er (or not) quantum scattering can be used as a universal quantum computer\
, and I plan primarily to approach this problem by connecting theorems abou
t quantum walks and their universality to scattering theory via continuum l
imits. \n\nIn this talk I will present results I have obtained about contin
uum limits of some quantum walks on the integers which are interesting in t
heir own right\, and may also give an entrée into the larger question of c
ontinuum limits of walks on graphs. In particular I will give an overview
of quantum walks and their relationships to the Dirac and Schrodinger equat
ions\, motivation for computational universality of scattering theory\, and
discuss my various results on continuum limits of quantum walks.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170821T155811Z
DTSTART:20170830T120000Z
DTEND:20170830T160000Z
UID:event1800@bu.edu
URL:http://physics.bu.edu/events/show/1800
SUMMARY:Comprehensive Exams - Part 1
DESCRIPTION:Featuring Ami Katz\n\nPart of the Comprehensive Exams.\n\n
LOCATION:SCI B58\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170814T154723Z
DTSTART:20170831T120000Z
DTEND:20170831T160000Z
UID:event1793@bu.edu
URL:http://physics.bu.edu/events/show/1793
SUMMARY:Incoming Graduate Students Orientation
DESCRIPTION:Featuring Kevin Black/Mirtha Cabello\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170821T155945Z
DTSTART:20170901T130000Z
DTEND:20170901T160000Z
UID:event1801@bu.edu
URL:http://physics.bu.edu/events/show/1801
SUMMARY:Comprehensive Exams - Part 2
DESCRIPTION:Featuring Ami Katz\n\nPart of the Comprehensive Exams.\n\n
LOCATION:SCI B58\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170815T205644Z
DTSTART:20170911T170000Z
DTEND:20170911T180000Z
UID:event1798@bu.edu
URL:http://physics.bu.edu/events/show/1798
SUMMARY:COUPLED WIRE CONSTRUCTION OF NON-ABELIAN CHIRAL SPIN LIQUIDS
DESCRIPTION:Featuring Po-Hao Huang\n\nPart of the PhD Final Oral Exams.\n\n
Dissertation Committee: Claudio Chamon\, Andrei Ruckenstein\, Anatoli Polk
ovnikov\, Emanuel Katz\, Michael El-Batanouny\n\nAbstract:\n\nTopologically
ordered states of matter have attracted much interest in the past decade.\
nThe search for emergent point-like non-Abelian anyons electronic systems i
s one of the\nmost exciting problems in condensed matter physics\, since it
opens many possibilities for\ntopological quantum computing. In this talk\
, I will construct two-dimensional non-Abelian\ntopologically ordered state
s by strongly coupling arrays of one-dimensional quantum wires\nvia interac
tions. In our scheme\, all charge degrees of freedom are gapped\, so the co
n-\nstruction can use either quantum wires or quantum spin chains as buildi
ng blocks\, with\nthe same end result. Hence\, the resulting non-Abelian sp
in liquid states have vanishing\nquantum Hall conductivities\, but nonzero
thermal ones. The construction gaps the degrees\nof freedom in the bulk\, w
hile leaving decoupled states at the edges that are described by\nconformal
eld theories (CFT) in (1 + 1)-dimensional space and time. We prescribe\, i
n\nparticular\, how to arrive at all the edge states described by the unita
ry CFT minimal\nmodels with central charges c < 1.
LOCATION:SCI TBA\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170823T061129Z
LAST-MODIFIED:20170821T153201Z
DTSTART:20170918T173000Z
DTEND:20170918T183000Z
UID:event1799@bu.edu
URL:http://physics.bu.edu/events/show/1799
SUMMARY:Chon Kit Pun _TBA
DESCRIPTION:Featuring Chon Kit Pun\n\nPart of the Preliminary Oral Exam.\n\
n
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR