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METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
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:20171020T103724Z
LAST-MODIFIED:20170906T184607Z
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\, University of Cambridge \nHosted by
: Claudio Rebbi\n\nPart of the Condensed Matter Theory Seminar Series.\n\nI
n the ﬁrst part we present a slave-particle meanﬁeld study of the mixed
boson+fermion quantum dimer model introduced by Punk\, Allais\, and Sachde
v [PNAS 112\, 9552 (2015)] to describe the physics of the pseudogap phase i
n cuprate superconductors. Our analysis naturally leads to four charge e fe
rmion pockets whose total area is equal to the hole doping p\, for a range
of parameters consistent with the t−J model for high temperature supercon
ductivity. Here we ﬁnd that the dimers are unstable to d-wave superconduc
tivity at low temperatures. The region of the phase diagram with d-wave rat
her than s-wave superconductivity matches well with the appearance of the f
our fermion pockets. In the superconducting regime\, the dispersion contain
s eight Dirac cones along the diagonals of the Brillouin zone. \n\nIn the s
econd part we present an approach for studying systems with hard constraint
s such that certain positive semideﬁnite operators must vanish. The diﬃ
culty with mean-ﬁeld treatments of such cases is that imposing that the c
onstraint is zero only in average is problematic for a quantity that is alw
ays non-negative. We reformulate the hard constraints by adding an auxiliar
y system such that some of the states to be projected out from the total sy
stem are at ﬁnite negative energy and the rest at ﬁnite positive energy
\, we dubbed this method the soft constraint. This auxiliary system comes w
ith an extra coupling that we are free to vary and that parametrizes a whol
e family of mean-ﬁeld theories. We argue that this variational-type param
eter for the family of mean-ﬁeld theories should be ﬁxed by matching a
given experimental observation\, with the quality of the resulting mean-ﬁ
eld approximation measured by how it ﬁts other data. We test these ideas
in the well-understood single-impurity Kondo problem\, where we ﬁx the pa
rameter via the TK (Kondo temperature) obtained from the magnetic susceptib
ility value\, and score the quality of the approximation by its predicted W
ilson ratio. We also study a continuum version of the soft constraint metho
d. To show its usefulness we study the Laughlin fractional quantum Hall sta
tes at ﬁlling fraction ν = 1 2m+1. We produce the Landau Ginzburg Cherns
Simons theory for hard core bosons(arising in this formulation of the Laug
hlin functions0 for these ﬁlling fractions. We handle the hard core const
raint explicitly and show that to leading order it is equivalent to a theor
y of soft core bosons with an eﬀective density density interaction betwee
n the particles of the form of a Coulomb interaction coming from the electr
ons in the original theory and an eﬀective interaction coming from the ha
rd core constraint that can be tuned by hand which we denote by λ(q\,ω).
We show that we can use this eﬀective interaction to reproduce the known
spectra of both inter Landau level and intra Landau level neutral excitatio
ns for the Laughlin states as well as the energy gap to charged excitations
and the electromagnetic response tensor.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170906T184620Z
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\nHosted by: Claudio Rebbi\n\nPart of the Condensed Matter Theory S
eminar Series.\n\nI will review recent progress on the understanding of man
y-body localization\, i.e.\, the phenomenon of absence of thermalization in
interacting\, disordered quantum systems. After discussing the restricted
domain of existence of strict many body-localization and the role of rare e
vents\, I will present a real space renormalization group analysis which of
fers a microscopic scenario for the unusual dynamical phase transition whic
h occurs as a localized system is tuned into an ergodic regime. While the t
ransition is associated with a diverging time scale for thermalization\, mo
st spatial correlators remain short range at the critical point. The latter
goes hand in hand with the discontinuous evolution of expectation values o
f local observables. These features distinguish the transition sharply from
standard critical phenomena.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170906T184708Z
DTSTART:20170811T150000Z
DTEND:20170811T170000Z
UID:event1782@bu.edu
URL:http://physics.bu.edu/events/show/1782
SUMMARY:Out-of-equilibrium states and quantum annealing speed up in non-con
vex optimization and learning problems
DESCRIPTION:Featuring Riccardo Zecchina\n\nPart of the Condensed Matter The
ory Seminar Series.\n\nQuantum annealers aim at solving non-convex optimiza
tion problems by exploiting cooperative tunneling effects to escape local m
inima. A key challenge is to identify classes of non-convex optimization pr
oblems for which this scheme can induce an exponential speed up compared t
o thermal annealing. We show that this happens for a wide class of optimiza
tion problems which are also central to machine learning. Their energy land
scape is exponentially dominated by local minima that trap classical therma
l annealers\, while quantum annealing converges efficiently to rare dense r
egions of optimal solutions. For non convex problems\, these will not in g
eneral correspond to configuration dominating the Gibbs measure.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
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:20171020T103724Z
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\nHosted by: Anatoli
Polkovnikov\n\nPart of the Condensed Matter Theory Seminar Series.\n\nEntr
opy is a fundamental concept in statistical mechanics. In this talk\, I inv
estigate two aspects of entropy. First\, we reveal a universal behavior of
entanglement entropy of the pure quantum states which are in thermal equili
brium states. Second\, we characterize thermodynamic entropy as a Noether i
nvariant under a non-uniform time translation. \n\nIn the first part\, we f
ocus on the size dependence of the entanglement entropy of the pure quantum
states which can fully describe thermal equilibrium as long as one focuses
on local observables. The thermodynamic entropy can also be recovered as t
he entanglement entropy of small subsystems. When the size of the subsystem
increases\, however\, quantum correlations break the correspondence and ma
ndate a correction to this simple volume-law. The elucidatione of the size
dependence of the entanglement entropy is thus of essential importance in l
inking quantum physics with thermodynamics\, and in analyzing recent experi
ments on ultra-cold atoms. In this talk\, we derive an analytic formula of
the entanglement entropy for a class of pure states called cTPQ states repr
esenting thermal equilibrium. We find that our formula applies universally
to any sufficiently scrambled pure state representing thermal equilibrium\,
i.e.\, general energy eigenstates of non-integrable models and states afte
r quantum quenches. Our universal formula can be exploited as a diagnostic
tool for chaotic systems; we can distinguish integrable models from chaotic
modelsand detect many-body localization with high accuracy. \n\nIn the sec
ond part\, we investigate a thermally isolated quantum many-body system wit
h an external control represented by a time-dependent parameter. We formula
te a path integral in terms of thermal pure states and derive an effective
action for trajectories in a thermodynamic state space\, where the entropy
appears with its conjugate variable. In particular\, for quasi-static opera
tions\, the symmetry for the uniform translation of the conjugate variable
emerges in the path integral. This leads to the entropy as a Noether invari
ant.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
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:20171020T103724Z
LAST-MODIFIED:20170828T185042Z
DTSTART:20170830T130000Z
DTEND:20170830T140000Z
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:20171020T103724Z
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:20171020T103724Z
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:20171020T103724Z
LAST-MODIFIED:20170827T143849Z
DTSTART:20170907T160000Z
DTEND:20170907T180000Z
UID:event1802@bu.edu
URL:http://physics.bu.edu/events/show/1802
SUMMARY:Special Systems Biology Seminar: A Conversation About Climate Chang
e
DESCRIPTION:Featuring Charles DeLisi\, Metcalf Professor of Science and Eng
ineering \, Dean Emeritus\, College of Engineering - Boston University\n\nT
he complexity and uncertainties of climate science leave an enormous openin
g for political controversy\, and amplify the environmental and economic co
nsequences associated with possible courses of action---which range from do
ing nothing\, to the Gore proposal to reduce emissions 90% by 2050. \n\nCon
troversy notwithstanding\, scientists have uncovered some hard facts\, and
have also drawn plausible inferences\, with varying levels of confidence\,
about the past and future climate of our planet. Before opening the meetin
g to conversation\, \nI’ll spend about thirty minutes briefly reviewing w
hat’s known about the contribution of human activity to changes in greenh
ouse gases\, average global temperature\, sea levels\, the predicted conseq
uences of allowing change to continue unabated\, and the confidence levels
of the predictions. I’ll also briefly indicate proposed mitigation strate
gies\, including my own views about the potential use of biotechnology for
regulating atmospheric carbon dioxide and other greenhouse gases.
LOCATION:LSE 103\, 24 Cummington Mall\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
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:20171020T103724Z
LAST-MODIFIED:20170911T162601Z
DTSTART:20170912T190000Z
DTEND:20170912T200000Z
UID:event1826@bu.edu
URL:http://physics.bu.edu/events/show/1826
SUMMARY:Constructing Ultra-Slow Glasses in Lattice Models for Reversible Co
mputing
DESCRIPTION:Featuring Lei Zhang\n\nPart of the Preliminary Oral Exam.\n\nEx
amining Committee: Andrei Ruckenstein\, Claudio Chamon\, Michael El-Batano
uny\, Richard Brower\n\nAbstract:\n\nWe construct a two-dimensional lattice
model that lacks any finite temperature phase transition and yet displays
relaxation times that grow as a double exponential of the inverse temperatu
re. The model has bulk translational invariance\, only broken by the presen
ce of the boundaries. The lattice model is associated to a reversible circu
it that can multiply or factorize integers\, depending on the boundary cond
itions. When the lattice model reaches its ground state\, all computations
are performed without error. The ultra-slow (double exponential in inverse
temperature) glassy dynamics is associated with the difficulty of the syste
m to heal computational errors that cost little energy but flip a volumetri
c number of bits in the system.\n\n![Lei](/resources/event-image/1826/af5ae
ef_small)
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170906T183707Z
DTSTART:20170913T150000Z
DTEND:20170913T160000Z
UID:event1816@bu.edu
URL:http://physics.bu.edu/events/show/1816
SUMMARY:Correlations in driven-dissipative quantum systems
DESCRIPTION:Featuring Michiel Wouters\, University of Antwerp\nHosted by: A
natoli Polkovnikov\, Dries Sels\n\nPart of the Condensed Matter Theory Semi
nar Series.\n\nRecent advances in experimental platforms for photonic quant
um simulators (microcavity polaritons and superconducting circuits) have sp
urred the interest in the theory of driven-dissipative quantum systems. The
long time steady state of such systems is not given by a Boltzmann-Gibbs d
istribution\, but has to be found by solving a Lindblad master equation. \n
\nIn this talk\, I will discuss two topics: for weakly interacting systems\
, the imprint of Landau-Beliaev scattering on the steady state distribution
of a 1D photonic Hubbard model in the weakly interacting regime and the fa
ilure of the truncated Wigner approximation to capture this feature. For st
rongly interacting systems\, I will present results obtained within the Gut
zwiller approximation to the quantum trajectories of a dissipative XYZ mode
l. We show that a ferromagnetic to paramagnetic phase transition\, that is
missing within a mean field treatment\, is recovered within our approach.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170901T145009Z
DTSTART:20170913T180000Z
DTEND:20170913T190000Z
UID:event1817@bu.edu
URL:http://physics.bu.edu/events/show/1817
SUMMARY:Numerical Signatures of Conformal Field Theory
DESCRIPTION:Featuring Pranay Patil\n\nPart of the Preliminary Oral Exam.\n\
nAbstract: Conformal Field theory has important consequences for quantum ph
ase transitions and dynamical response of lattice models and as it is not a
lways possible to analytically determine if a lattice model has a low energ
y conformal description\, we need to find numerical signatures which can re
liably help us identify a CFT. Here we look at how entanglement entropy and
correlation functions fare as candidates for CFT signatures using some exa
mples of established CFTs such as the 2d classical Ising model and 1d Heise
nberg chain. We also explore some interesting properties of the 1d Heisenbe
rg chain using these numerics.\n\nDissertation committee: Anders Sandvik\,
Claudio Chamon\, Emanuel Katz\, Alex Sushkov \n\n![Pranay](/resources/event
-image/1817/00307ec_small)
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170912T161810Z
DTSTART:20170915T160000Z
DTEND:20170915T173000Z
UID:event1833@bu.edu
URL:http://physics.bu.edu/events/show/1833
SUMMARY:"Resonant x-ray spectroscopy of topological semimetals"
DESCRIPTION:Featuring Stefanos Kourtis\, Boston University\, Physics Depart
ment\n\nPart of the Condensed Matter Theory Seminar Series.\n\nAngle-resolv
ed photoemission spectroscopy (ARPES) has so far been the definitive method
for the characterization of materials as topological Weyl or Dirac semimet
als\, via direct visualization of band touchings in the bulk and nontrivial
states at the boundary. However\, the unconventional and potentially usefu
l properties of these materials are a consequence of a singular Berry curva
ture distribution\, which cannot be resolved in ARPES. Furthermore\, contro
l over the number and position of Weyl nodes -- the most important property
from an application standpoint -- can only be achieved with sizable electr
omagnetic fields\, which curtail the resolving power of ARPES\, thereby ren
dering the band structure inaccessible to this technique. We show how reson
ant x-ray scattering (RXS) offers a viable path for (a) deducing the band s
tructure of materials in arbitrarily large magnetic fields and (b) visualiz
ing the Berry curvature distribution in momentum space via polarization con
trol of incoming and outgoing x-ray beams. By low-energy modeling of specif
ic material candidates based on ab initio band structure calculations\, we
derive the corresponding RXS spectra and highlight the salient features ste
mming from topological nontriviality. The proposed measurements are within
the resolving capabilities of current instrumentation.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170907T140232Z
DTSTART:20170918T160000Z
DTEND:20170918T180000Z
UID:event1828@bu.edu
URL:http://physics.bu.edu/events/show/1828
SUMMARY:Physics Department Annual BBQ
DESCRIPTION:\nPart of the Departmental Seminars.\n\nPlease join the Physics
Department for our annual BBQ on Monday\, September 18th from 12:00PM-2PM
at the SCI Front Plaza\, 590 Commonwealth Avenue. The BBQ food will include
hot dogs\, hamburgers\, veggie burgers\, chips\, watermelon\, and cookies.
Refreshments will be provided.\n\nWe look forward to seeing you there!
LOCATION:SCI Plaza\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170907T183607Z
DTSTART:20170918T173000Z
DTEND:20170918T183000Z
UID:event1799@bu.edu
URL:http://physics.bu.edu/events/show/1799
SUMMARY:Market Bubbles: Collective Behavior in the Financial Market
DESCRIPTION:Featuring Chon Kit Pun\n\nPart of the Preliminary Oral Exam.\n\
nExamining Committee: William Klein\, Harvey Gould\, Kirill Korolev\, Chris
topher Grant\, Alex Sushkov\n\nAbstract:\n\n\nFrom the stock bubbles in the
1920s\, which eventually led to the Great Depression in the 1930s\, to the
recent boom and bust of the real estate bubbles in 2007-2009\, market bubb
les have been the main source of instability in the financial market. While
speculators and momentum traders are blamed to have driven the price away
from the reasonable level during the formation of a bubble\, value investor
s like the fund managers may sometimes fail to correct the price and instea
d join 'riding the bubble'\, which help growing the bubble further.\n\nIn t
his talk I will present an agent-based model of how the collective behavior
of traders give rise to a bubble. In this model traders learn which assets
to invest by using the Experience Weighted Attraction (EWA) learning algor
ithm\, which has its root in both behavioral psychology and game theory and
has seen applications in social science and economics. I will show that wh
en traders tend to invest in the `winning' asset\, memory and liquidity pla
y an important role in the formation\nof bubbles. The discussion of the res
ult will be emphasized on the implication to the real market\, and on the c
omparison with statistical physics.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170919T145442Z
DTSTART:20170922T160000Z
DTEND:20170922T173000Z
UID:event1836@bu.edu
URL:http://physics.bu.edu/events/show/1836
SUMMARY:"Interfering directed paths & the sign phase transition"
DESCRIPTION:Featuring Christopher Baldwin\, Boston University\, Physics Dep
artment\n\nPart of the Condensed Matter Theory Seminar Series.\n\nWe consid
er the problem of interfering directed paths in disordered media\, and disc
uss the physical contexts in which this problem arises. An important proper
ty of the path sum is the statistics of its sign. The average sign may tend
to zero ("sign-disordered") or remain finite ("sign-ordered") at long dist
ance\, depending on dimensionality and the concentration of negative scatte
ring sites x. We discuss the analogy with a dynamical out-of-equilibrium Is
ing field. We further show that the sign-ordered phase is always unstable f
or any non-zero x in 2D by identifying rare destabilizing events\, and pres
ent numerical evidence that it is stable in 3D. These results have conseque
nces for several different physical systems\, which we conclude by describi
ng.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170911T151308Z
DTSTART:20170925T150000Z
DTEND:20170925T163000Z
UID:event1829@bu.edu
URL:http://physics.bu.edu/events/show/1829
SUMMARY:"Lieb-Schultz-Mattis Theorem and its generalizations from the Persp
ective of the Symmetry Protected Topological Phase"
DESCRIPTION:Featuring Cenke Xu \, University of California - Santa Barbara\
nHosted by: Anders Sandvik\n\nPart of the Condensed Matter Theory Seminar S
eries.\n\nWe ask whether a local Hamiltonian with a featureless (fully gapp
ed and\nnondegenerate) ground state could exist in certain quantum spin sys
tems. \nWe address this question by mapping the vicinity of certain quantum
critical point (or gapless phase) of the d−dimensional spin system under
study to the boundary of a (d+1)−dimensional bulk state\, and the lattic
e symmetry of the spin system acts as an on-site symmetry in the field theo
ry that describes both the selected critical point of the spin system\, and
the corresponding boundary state of the (d+1)−dimensional bulk. If the c
orresponding bulk state is a trivial state instead of a bosonic symmetry pr
otected topological (SPT) state\, then a featureless ground state of the sp
in system is allowed; if the corresponding bulk state is indeed a nontrivia
l SPT state\, then it likely excludes the existence of a featureless ground
state of the spin system. From this perspective we identify the spin syste
ms with SU(N) and SO(N) symmetries on one\, two and three dimensional latti
ces that permit a featureless ground state. We also verify our conclusions
by other methods\, including an explicit construction of these featureless
spin states.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170908T135842Z
DTSTART:20170927T150000Z
DTEND:20170927T160000Z
UID:event1830@bu.edu
URL:http://physics.bu.edu/events/show/1830
SUMMARY:"Iterative Compression-Decimation Scheme for Tensor Network Optimiz
ation"
DESCRIPTION:Featuring Zhicheng Yang\, Boston University\, Physics Departmen
t\n\nPart of the Condensed Matter Theory Seminar Series.\n\nMotivated by st
atistical physics models connected to computation problems\, we devise a te
nsor network technique that is suited to problems with or without translati
on invariance and with arbitrary boundary conditions. We introduce a compre
ssion-decimation algorithm as an efficient iterative scheme to optimize ten
sor networks that encode generalized vertex models on regular lattices. The
algorithm first propagates local constraints to longer ranges via repeated
contraction-decomposition sweeps over all lattice bonds\, thus achieving c
ompression on a given length scale. It then decimates the lattice via coars
e-graining tensor contractions. Repeated iterations of these two steps allo
w us to gradually collapse the tensor network while keeping the tensor dime
nsions under control\, such that ultimately the full tensor trace can be ta
ken for relatively large systems. As a benchmark\, we demonstrate the effic
iency of the algorithm by computing the ground state entropy density of the
planar ice model and the eight-vertex model. We then apply it to reversibl
e classical computational problems based on a recently proposed vertex mode
l representation of classical computations [Nat. Commun. {\bf8}\, 15303 (20
17)]. Our protocol allows us to obtain the exact number of solutions for co
mputations where a naive enumeration would take astronomically long times\,
suggesting that the algorithm is a promising practical tool for the soluti
on of a plethora of problems in physics and computer science.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170928T130857Z
DTSTART:20170928T140000Z
DTEND:20170928T150000Z
UID:event1842@bu.edu
URL:http://physics.bu.edu/events/show/1842
SUMMARY:Exploring Strain Physics in 2D Systems
DESCRIPTION:Featuring Jason Christopher\n\nPart of the Departmental Seminar
s.\n\nDissertation Committee: Bennett Goldberg\, Anna Swan\, David Bishop\
, David Campbell\, Kenneth Lane \n\nAbstract: Two dimensional (2D) materia
ls can withstand an order of magnitude more strain than their bulk counterp
arts which can be used to dramatically change electrical\, thermal and opti
cal properties or even cause unconventional behavior such as generating pse
udo-magnetic fields (PMF). In this seminar I will discuss the origin of PMF
s and several experimental methods I am pursuing to experimentally realize
controllable PMFs using micro-electromechanical systems (MEMS) and neon ato
m intercalation.\n\n![Jason](/resources/event-image/1842/e76821b_small)
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170925T130542Z
DTSTART:20170928T193000Z
DTEND:20170928T203000Z
UID:event1837@bu.edu
URL:http://physics.bu.edu/events/show/1837
SUMMARY:SOLUTIONS TO LINEAR PROBLEMS IN ABERRATED OPTICAL SYSTEMS
DESCRIPTION:Featuring William Shain\n\nPart of the PhD Final Oral Exams.\n\
nExamining Committee: Bennett Goldberg\, Jerome Mertz\, David Campbell\, St
eve Ahlen\, Thomas Bifano\n\nAbstract:\n\nOne of the greatest challenges in
understanding any physical system is extracting as much information as pos
sible. In optics\, the laws that govern the interaction of a system with li
ght are frequently linear: Maxwell’s equations lead to linear wave equati
ons\, and in general one can write the evolution of the quantities of inter
est as a linear propagation in space and time. This linearity imposes a con
straint on how one recovers information about an object of interest; for ex
ample\, one can expand the field-of-view by taking multiple images (reducin
g the total framerate) or by lowering the numerical aperture (reducing the
resolution). In each case\, one aspect of information is sacrificed for ano
ther. Therefore\, one can efficiently probe a system through optical means
by carefully choosing what aspects of the light are measured\, depending on
the problem of interest. This can be attained through direct manipulation
of the optical propagator\, by using a Spatial Light Modulator to perform p
hysical linear transformations on the light field. In this thesis\, I demon
strate the usefulness of a MEMS Deformable Mirror (DM) in implementing the
necessary linear transformation\, and apply the methodology to three system
s of interest: recovering imaging capabilities in porous rock\, expanded im
aging of neuronal activity in brain tissue\, and high-throughput particle i
dentification in label-free flow cytometry. In each case\, I show how caref
ul control of the light travelling through the microscope allows for optimi
zed recovery of the desired information.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170912T160128Z
DTSTART:20171004T150000Z
DTEND:20171004T160000Z
UID:event1832@bu.edu
URL:http://physics.bu.edu/events/show/1832
SUMMARY:"Stability of quantum statistical ensembles with respect to local m
easurements"
DESCRIPTION:Featuring Walter Hahn\, Skolkovo Institute of Science and Techn
ology\, Moscow\nHosted by: Anatoli Polkovnikov\n\nPart of the Condensed Mat
ter Theory Seminar Series.\n\nWe introduce a stability criterion for quantu
m statistical ensembles describing macroscopic systems. An ensemble is call
ed "stable" when a small number of local measurements cannot significantly
modify the probability distribution of the total energy of the system. We a
pply this criterion to lattices of spins-1/2\, thereby showing that the can
onical ensemble is nearly stable\, whereas statistical ensembles with much
broader energy distributions are not stable. In the context of the foundati
ons of quantum statistical physics\, this result justifies the use of stati
stical ensembles with narrow energy distributions such as canonical or micr
ocanonical ensembles.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171006T140420Z
DTSTART:20171006T160000Z
DTEND:20171006T173000Z
UID:event1820@bu.edu
URL:http://physics.bu.edu/events/show/1820
SUMMARY:"Diabatic approach to creating ground states of certain critical mo
dels"
DESCRIPTION:Featuring Kartiek Agrawal\, Princeton University\nHosted by: An
atoli Polkovnikov\n\nPart of the Condensed Matter Theory Seminar Series.\n\
nWe propose a spatio-temporal quench protocol that allows for the fast prep
aration of ground states of gapless models with Lorentz invariance. Assumin
g the system initially resides in the ground state of a corresponding massi
ve model\, we show that a supersonically-moving ‘front’ that locally qu
enches the mass\, leaves behind it (in space) a state arbitrarily close to
the ground state of the gapless model. Importantly\, our protocol takes tim
e O (L) to produce the ground state of a system of size ∼ Ld (d spatial d
imensions)\, while a fully adiabatic protocol requires time ∼ O( L2) to p
roduce a state with exponential accuracy in L. We provide proof-of-concept
by solving the proposed quench exactly for a system of free bosons in arbit
rary dimensions\, and for free fermions in d = 1. We also discuss the role
of interactions and UV effects on the free-theory idealization\, before num
erically illustrating the usefulness of the approach using simulations on c
lassical phonons and on the quantum Heisenberg spin-chain with a mass induc
ed by local magnetic fields.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171002T180812Z
DTSTART:20171013T160000Z
DTEND:20171013T173000Z
UID:event1821@bu.edu
URL:http://physics.bu.edu/events/show/1821
SUMMARY:"Coherent optical control and nonlinear probing of strongly correla
ted materials"
DESCRIPTION:Featuring Roman Mankowsky\, Paul Scherrer Institute \nHosted by
: Wanzheng Hu\n\nPart of the Condensed Matter Theory Seminar Series.\n\nMid
-infrared optical pulses can resonantly drive selected vibrational modes in
solids to deform their crystal structure. In strongly correlated materials
\, this method has been used to melt electronic and magnetic order\, drive
insulator-to-metal transitions\, and transiently induce superconductivity.
Free Electron Lasers have been key in identifying the lattice dynamics unde
rlying these transitions.\n\nIn this talk\, I will first review nonlinear p
hononics and discuss its role in the phenomenon of light-induced supercondu
ctivity. I will then present recent studies\, in which resonant lattice exc
itation was used to control the polarization of ferroelectric materials on
femtosecond timescales. These studies are a first step toward ultrafast rev
ersible switching. In the last part of the lecture\, I will focus on the ex
citation of highly nonlinear lattice dynamics\, a new technique which allow
ed us to reconstruct the interatomic lattice potential of a solid and bench
mark first principle calculations.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170925T150524Z
DTSTART:20171016T163000Z
DTEND:20171016T173000Z
UID:event1840@bu.edu
URL:http://physics.bu.edu/events/show/1840
SUMMARY:"Physicochemical Conditions for Self-Replication"
DESCRIPTION:Featuring Sumantra Sarkar\, Massachusetts Institute of Technolo
gy\nHosted by: Robert Marsland\n\nPart of the Biophysics Seminars.\n\n
LOCATION:CILSE 106C\, 610 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170913T200604Z
DTSTART:20171018T150000Z
DTEND:20171018T160000Z
UID:event1814@bu.edu
URL:http://physics.bu.edu/events/show/1814
SUMMARY:"Cluster Synchronization of Chaotic Systems in Large Networks"
DESCRIPTION:Featuring Louis Pecora\, United States Naval Research Laborator
y\nHosted by: David Campbell\n\nPart of the Condensed Matter Theory Seminar
Series.\n\nSynchronization of two chaotic systems is a well-known phenomen
on\, although it still seems like an oxymoron. But when many oscillators (c
haotic or not) are linked together in a network causing them to interact\,
they can synchronize to other oscillators in the network\, but not necessar
ily all of them. The network can break up into clusters of synchronized sy
stems where the oscillators in the same cluster synchronize\, but not to os
cillators in other clusters even though all clusters are interconnected and
influence each other. I show that such patterns of synchronization can be
related to the symmetries of the network. One can use computational group
theory to find all the symmetries and hence\, clusters. Such symmetries ca
n be huge in number (e.g. 10^66 symmetries in a network of 100 oscillators)
\, but can be found in short time. I'll show how to analyze such systems\,
determine the stability of the cluster patterns\, and find interesting patt
erns of desynchronization bifurcations. I'll show how one can generate such
patterns in an electro-optical system. The methods I present will include
the construction of synchronization patterns that do not arise from symmetr
ies\, but can be built up from symmetry clusters make symmetries the fundam
ental concept in many cluster patterns.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171017T174315Z
DTSTART:20171020T160000Z
DTEND:20171020T170000Z
UID:event1847@bu.edu
URL:http://physics.bu.edu/events/show/1847
SUMMARY:"Kibble-Zurek Dynamics of a Driven Dissipative System: Universality
Beyond the Markovian Regime"
DESCRIPTION:Featuring Tamiro Villazon\, Boston University\, Physics Departm
ent\n\nPart of the Condensed Matter Theory Seminar Series.\n\nPhase transit
ions in open systems provide a rich avenue for the study of many-body non-e
quilibrium phenomena. These systems exhibit unique properties depending on
the detailed nature of their system-bath interactions\, which may nontrivia
lly alter their critical dynamics\, and which in turn are amenable to study
by slow ramps across the critical point. In this talk\, I will discuss Kib
ble-Zurek dynamics in a paradigmatic two-mode driven-dissipative system of
a pair of non-degenerate parametrically coupled\, optomechanical oscillator
s. I will detail the key theoretical aspects of the model and it's predicti
ons on universality\, which have been confirmed in experiments by our colla
borators in the Vengalattore group at Cornell University.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171011T143333Z
DTSTART:20171023T163000Z
DTEND:20171023T173000Z
UID:event1825@bu.edu
URL:http://physics.bu.edu/events/show/1825
SUMMARY:"On Growth and Form of Range Expansions at Liquid Interfaces"
DESCRIPTION:Featuring Severine Atis\, Harvard University\nHosted by: Kirill
Korolev\n\nPart of the Biophysics Seminars.\n\nTransport phenomena shape a
nd constantly reorganize materials at every scale. In presence of hydrodyna
mical flows\, the Lagrangian advection of individual particles strongly inf
luences their dispersion\, segregation and clustering. Range expansions of
living cells resting on liquid substrates is of great importance in underst
anding the organization of microorganism populations. However\, combining g
rowth dynamics of an expanding assembly of cells with hydrodynamics leads t
o challenging problems\, which involve the coupling of nonlinear dynamics\,
stochasticity and transport. In this talk\, I will present laboratory expe
riments\, combined with numerical modelling\, focused on the collective dyn
amics of genetically labelled microorganisms undergoing division and compet
ition in the presence of a variety of flows. We have created an extremely v
iscous medium that allows us to grow cells on a controlled liquid interface
over macroscopic scales. I will show that an expanding population of micro
organisms can itself generate a radial flow\, leading to an accelerated pro
pagation and fragmentation of the initial colony. I will show how the dynam
ics and morphology of these microbial populations is affected by the fluid
dynamics triggered by this metabolically generated flow. I will conclude by
discussing the potential influence of transport and mixing on evolutionary
dynamics\, and how the control of cell assemblies on liquid interfaces can
lead to a wide range of phenomena at the intersection between cellular bio
logy and physics.
LOCATION:CILSE 106C\, 610 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170927T145841Z
DTSTART:20171023T180000Z
DTEND:20171023T190000Z
UID:event1841@bu.edu
URL:http://physics.bu.edu/events/show/1841
SUMMARY:Christopher Kachulis - TBA
DESCRIPTION:Featuring Christopher Kachulis\n\nPart of the Departmental Semi
nars.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171018T193831Z
DTSTART:20171024T153000Z
DTEND:20171024T163000Z
UID:event1848@bu.edu
URL:http://physics.bu.edu/events/show/1848
SUMMARY:"Exciting dynamics in multiple time dimensions"
DESCRIPTION:Featuring Ivar Mar\, Argonne National Lab\n\nPart of the Conden
sed Matter Theory Seminar Series.\n\nExternally driving a dynamical system\
, be it quantum or classical\, effectively increases the number of its time
dimensions. In this talk I will describe how these extra time dimensions
can be harnessed to synthesize topological insulators purely in time domain
\, describe their possible applications for energy conversion and quantum e
ngineering\, and point out connections to localization and chaos.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171011T140140Z
DTSTART:20171025T150000Z
DTEND:20171025T163000Z
UID:event1823@bu.edu
URL:http://physics.bu.edu/events/show/1823
SUMMARY:"Nearly deconfined spinon excitations in the square-lattice spin-1/
2 Heisenberg antiferromagnet"
DESCRIPTION:Featuring Hui Shao\, Beijing Computational Science Research Cen
ter\nHosted by: Anders Sandvik\n\nPart of the Condensed Matter Theory Semin
ar Series.\n\nWe study the spin excitation spectrum of the spin-1/2 square-
lattice\nHeisenberg antiferromagnet with QMC and an improved stochastic\na
nalytic continuation method. The spectra are in excellent agreement\nwith r
ecent neutron scattering experiments on Cu(DCOO)2·4D2O\, where a\nbroad sp
ectral-weight continuum at wavevector q = (\pi\,0) was\ninterpreted as deco
nfined spinons. Our results show a similar\nreduction of the magnon weight
and a large continuum. Upon turning on\nthe Q interaction in the J-Q model\
, we observe a rapid reduction of\nthe magnon weight to zero\, well before
the system undergoes a\ndeconfined quantum phase transition into a non-magn
etic spontaneously\ndimerized state. Based on these results\, we re-interpr
et the picture\nof deconfined spinons at (\pi\,0) in the experiments as nea
rly\ndeconfined spinons—a precursor to deconfined quantum criticality. We
\nalso introduce an effective model of the excitations (one magnon or\ntwo
spinons) which can reproduce the reduction of magnon weight and\nlowered ex
citation energy at (\pi\,0) in the Heisenberg model\, as well\nas the rapid
loss of the (\pi\,0) magnon with increasing Q in the J-Q\nmodel.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171010T163114Z
DTSTART:20171027T154500Z
DTEND:20171027T173000Z
UID:event1844@bu.edu
URL:http://physics.bu.edu/events/show/1844
SUMMARY:Physics Department Annual Pumpkin Drop
DESCRIPTION:\nJoin us on Friday\, October 27th for our 13th Annual Pumpkin
Drop!\n\nThe main event starts at 12:30pm in front of the Metcalf Science C
enter (SCI\, 590 Commonwealth Ave)\, but show up early to guess the weight
of the largest pumpkin and snack on some Halloween treats!\n\nYou can also
enter our costume contest for your chance at a prize! Extra points will be
awarded for creativity and detail. Enter to win at the contest table by 11:
45pm.\n\nThe Pumpkin Fall will be at 12:30pm.
LOCATION:SCI Plaza\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170912T170528Z
DTSTART:20171027T160000Z
DTEND:20171027T173000Z
UID:event1835@bu.edu
URL:http://physics.bu.edu/events/show/1835
SUMMARY:Condensed Matter Seminar TBA
DESCRIPTION:Featuring Kin Chung Fong\, Raytheon BBN Technologies and Harvar
d University\nHosted by: Scott Bunch\n\nPart of the Condensed Matter Theory
Seminar Series.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:TENTATIVE
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170925T134805Z
DTSTART:20171103T160000Z
DTEND:20171103T173000Z
UID:event1838@bu.edu
URL:http://physics.bu.edu/events/show/1838
SUMMARY:Biophysics/Condensed Matter Seminar
DESCRIPTION:Featuring Ben Machta\, Yale University\nHosted by: Robert Marsl
and\n\nPart of the Biophysics Seminars.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170920T140016Z
DTSTART:20171110T170000Z
DTEND:20171110T183000Z
UID:event1819@bu.edu
URL:http://physics.bu.edu/events/show/1819
SUMMARY:Condensed Matter Seminar TBA
DESCRIPTION:Featuring Yue Cao\, Brookhaven National Laboratory\nHosted by:
Karl Ludwig\n\nPart of the Condensed Matter Theory Seminar Series.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20171013T200332Z
DTSTART:20171113T170000Z
DTEND:20171113T180000Z
UID:event1846@bu.edu
URL:http://physics.bu.edu/events/show/1846
SUMMARY:Magnetic Field Effects in Low-Dimensional Quantum Magnets
DESCRIPTION:Featuring Adam Iaizzi\n\nPart of the PhD Final Oral Exams.\n\nE
xamining Committee: Anders Sandvik\, David Campbell\, Robert Carey\, Shyam
Erramilli\, Claudio Chamon\n\nAbstract:\n\nWe present a comprehensive study
of a low-dimensional spin-half quantum antiferromagnet\, the J-Q model\, i
n the presence of an external (Zeeman) magnetic field using numerical \nm
ethods\, chiefly stochastic series expansion quantum Monte Carlo with dire
cted loop updates and \nquantum replica exchange. The J-Q model is a many
-body Hamiltonian acting on a lattice of \nlocalized spin-half degrees of f
reedom; it augments the Heisenberg exchange with a \nfour-spin interaction
of strength Q. This model has been extensively studied at zero field\, whe
re \nthe Q term drives a quantum phase transition from a Neel-like state
to a valence-bond solid (a nonmagnetic state consisting of a long-range-
ordered arrangement of local singlet bonds \nbetween sites). This transiti
on is believed to be an example of deconfined quantum criticality\, \nwhere
the excitations are spinons—exotic spin-half bosons. We study the J-Q m
odel in the presence \nof a magnetic field in both one and two dimensions.
In one dimension\, there is metamagnetism above \na critical coupling rati
o (Q/J )min. Metamagnetism is a first-order quantum phase transition \ncha
racterized by discontinuities in the magnetization as a function of field (
magnetization jumps). \n We derive an exact expression for (Q/J)min = 2/9\
, and show that the metamagnetism is caused by \nthe onset of attractive in
teractions between magnons (flipped spins on a polarized\nbackground). We
predict that the same mechanisms will produce metamagnetism in the unfrus
trated \nantiferromagnetic J1-J2 model with anisotropy. Below (Q/J)min\,\n
the saturation transition is continuous and we show that it is governed by
the expected zero-scale-factor universality. In two dimensions\, we also f
ind metamagnetism above a \ncritical coupling ratio (Q/J)min=0.417\, caused
by the same mechanism as in the one-dimensional \ncase. In two dimension
s we also show evidence of an anomalous temperature dependence of specific
\nheat arising from field-induced Bose-Einstein condensation of spinons at
the deconfined quantum \ncritical point.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170906T204726Z
DTSTART:20171113T173000Z
DTEND:20171113T183000Z
UID:event1827@bu.edu
URL:http://physics.bu.edu/events/show/1827
SUMMARY:Biophysics Seminar TBA
DESCRIPTION:Featuring Zak Frentz\, Columbia University\nHosted by: Robert M
arsland\n\nPart of the Biophysics Seminars.\n\n
LOCATION:CILSE 106C\, 610 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170906T184026Z
DTSTART:20171115T160000Z
DTEND:20171115T173000Z
UID:event1824@bu.edu
URL:http://physics.bu.edu/events/show/1824
SUMMARY:Condensed Matter Seminar TBA
DESCRIPTION:Featuring Pierre Hohenberg\nHosted by: David Campbell\n\nPart o
f the Condensed Matter Theory Seminar Series.\n\n
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170912T162826Z
DTSTART:20171128T173000Z
DTEND:20171128T183000Z
UID:event1834@bu.edu
URL:http://physics.bu.edu/events/show/1834
SUMMARY:Biophysics Seminar TBA
DESCRIPTION:Featuring Carlos Castro \, Ohio State University \nHosted by: M
aria Kamenetska\n\nPart of the Biophysics Seminars.\n\n
LOCATION:CILSE 109C\, 610 Commonwealth Avenue\, 02215
STATUS:TENTATIVE
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170929T173130Z
DTSTART:20171204T173000Z
DTEND:20171204T183000Z
UID:event1843@bu.edu
URL:http://physics.bu.edu/events/show/1843
SUMMARY:Biophysics Seminar TBA
DESCRIPTION:Featuring Ksenia Bravaya \, Boston University\, Chemistry Depar
tment\n\nPart of the Biophysics Seminars.\n\n
LOCATION:CILSE 106C\, 610 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20171020T103724Z
LAST-MODIFIED:20170906T184111Z
DTSTART:20171215T170000Z
DTEND:20171215T183000Z
UID:event1822@bu.edu
URL:http://physics.bu.edu/events/show/1822
SUMMARY:Condensed Matter Seminar TBA
DESCRIPTION:Featuring Xi Dai\, Hong Kong University of Science and Technolo
gy\nHosted by: Wanzheng Hu\n\nPart of the Condensed Matter Theory Seminar S
eries.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR