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VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170119T204121Z
DTSTART:20170123T180000Z
DTEND:20170123T190000Z
UID:event1700@bu.edu
URL:http://physics.bu.edu/events/show/1700
SUMMARY:Dissipation\, time asymmetry\, and flux for model biomolecular syst
ems
DESCRIPTION:Featuring Aidan Brown\, Simon Fraser University\n\nPart of the
Condensed Matter Theory Seminar Series.\n\nThermal fluctuations play a sign
ificant role in biomolecular systems\, notably by preventing them from alwa
ys proceeding in a preferred direction. With energy dissipation necessary t
o break detailed balance\, we can ask how best to dissipate energy such tha
t a system is driven in the preferred direction. First\, by considering a m
odel of microscopic energy storage\, the characteristics that allow time-re
versal symmetry to be efficiently broken at fixed energy dissipation are ex
amined. I find that an intermediate energy barrier produces unusually high
asymmetry. Second\, using a biased chemical reaction cycle\, I determine ho
w to optimize the distribution of free energy dissipation to various stages
of a cycle\, to maximize the rate of forward progress. My results show tha
t the flux-maximizing distribution of dissipation depends on the inherent t
imescales of different transition pathways\, as well as the total free ener
gy dissipation available.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170210T162753Z
DTSTART:20170210T203000Z
DTEND:20170210T213000Z
UID:event1723@bu.edu
URL:http://physics.bu.edu/events/show/1723
SUMMARY:Coupled spin-1/2 ladders as microscopic models for non-Abelian chir
al spin liquids
DESCRIPTION:Featuring Po-Hao Huang\, Boston University\n\nPart of the Conde
nsed Matter Theory Seminar Series.\n\nTopologically ordered states of matte
r have attracted a much interest in the past decade. The search for emerge
nt point-like non-Abelian anyons in two-dimensional electronic system is on
e of the most exciting problems in condensed matter physics\, since it open
s many possibilities in quantum computing. In this talk\, I will construct
a two- dimensional lattice model that is argued to realize a chiral spin l
iquid with Ising topological order. The logic of the construction is to pr
epare an array of one-dimensional spin ladders with Ising criticality\, the
n couple them into the two-dimensional chiral spin liquid with spin-spin in
teractions that breaks time-reversal symmetry. This coupled wire construct
ion takes advantage of describing the one-dimensional spin system by confor
mal field theory. I will discuss mainly the theoretical proposal while pro
vide some numerical evidence to support it.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170320T165034Z
DTSTART:20170327T190000Z
DTEND:20170327T200000Z
UID:event1750@bu.edu
URL:http://physics.bu.edu/events/show/1750
SUMMARY:Intermittent Many-Body Dynamics at Equilibrium
DESCRIPTION:Featuring Sergej Flach\, Institute for Basic Science\, Daejeon\
, South Korea\n\nPart of the Condensed Matter Theory Seminar Series.\n\nThe
equilibrium value of an observable defines a manifold in the phase space o
f an ergodic\nand equipartitioned many-body system. A typical trajectory pi
erces that manifold infinitely\noften as time goes to infinity. We use thes
e piercings to measure both the relaxation time of\nthe lowest frequency ei
genmode of the Fermi-Pasta-Ulam chain\, as well as the fluctuations of the
subsequent dynamics in equilibrium. We show that previously obtained scalin
g laws for\nequipartition times are modified at low energy density due to a
n unexpected slowing down of\nthe relaxation. The dynamics in equilibrium i
s characterized by a power-law distribution of\nexcursion times far off equ
ilibrium\, with diverging variance. The long excursions arise from\nsticky
dynamics close to regular orbits in the phase space. Our method is generali
zable to\nlarge classes of many-body systems.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170321T142957Z
DTSTART:20170329T180000Z
DTEND:20170329T190000Z
UID:event1751@bu.edu
URL:http://physics.bu.edu/events/show/1751
SUMMARY:Higher Rank Quantum Spin Liquids: From Fractons to Emergent Gravity
DESCRIPTION:Featuring Michael Pretko\, MIT\n\nPart of the Condensed Matter
Theory Seminar Series.\n\nQuantum spin liquids are well described in the la
nguage of gauge theory. To date\, most theoretical effort has focused on t
he study of models with a familiar vector gauge field. However\, there exi
st stable spin liquids with more complicated gauge structure. In this talk
\, I will focus on three-dimensional spin liquid phases described by symmet
ric tensor ("higher spin") gauge fields. I will show that these models pos
sess exotic conservation laws which restrict the gauge charges to exist in
lower-dimensional subspaces\, as opposed to propagating in three-dimensiona
l space. Some charges are even restricted to a zero-dimensional subspace a
nd are totally immobile\, in a manifestation of the fracton phenomenon. As
a special case\, I will discuss rank 2 symmetric tensor spin liquids\, whi
ch provide us with toy models for emergent gravity.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170330T180716Z
DTSTART:20170405T183000Z
DTEND:20170405T193000Z
UID:event1746@bu.edu
URL:http://physics.bu.edu/events/show/1746
SUMMARY:Time-reversal and reflection symmetry in (2+1)-dimensional topologi
cal phases
DESCRIPTION:Featuring Meng Cheng\, Yale University\n\nPart of the Condensed
Matter Theory Seminar Series.\n\nAbstract: There has been immense progress
recently in the understanding of interacting topological phases of matter
in the presence of symmetry. I will discuss recent developments for the cas
e of time-reversal / reflection symmetry-enriched topological (SET) phases.
I will derive a simple formula for the ground state degeneracy of such SET
s on non-orientable manifold. I then use these results to develop an unders
tanding of anomalies associated with time-reversal / reflection SETs. If ti
me permits\, I will discuss explicit constructions of time-reversal/reflect
ion SETs\, including anomalous ones.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:TENTATIVE
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170320T133010Z
DTSTART:20170410T180000Z
DTEND:20170410T190000Z
UID:event1747@bu.edu
URL:http://physics.bu.edu/events/show/1747
SUMMARY:TBD
DESCRIPTION:Featuring Sayan Choudhury\n\nPart of the Condensed Matter Theor
y Seminar Series.\n\n
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170411T130625Z
DTSTART:20170414T150000Z
DTEND:20170414T160000Z
UID:event1758@bu.edu
URL:http://physics.bu.edu/events/show/1758
SUMMARY:Shortcuts to adiabaticity using flow-fields
DESCRIPTION:Featuring Ayoti Patra\, Maryland\n\nPart of the Condensed Matte
r Theory Seminar Series.\n\nAdiabatic invariants â€“ quantities that are pr
eserved under the slow driving of a systemâ€™s external parameters â€“ are
important in classical mechanics\, quantum mechanics and thermodynamics. Sh
ortcuts to adiabaticity are strategies for preserving adiabatic invariants
even under rapid driving. One such strategy utilizes an auxiliary counterdi
abatic term to suppress the non-adiabatic excitations arising due to rapid
driving. I will describe a unified framework for obtaining counterdiabatic
terms using flow-fields. In the flow-fields approach\, an appropriate inte
grated function (IF) is first defined. The flow-field parameters namely the
velocity and acceleration are derived from the IF. Counterdiabatic terms c
an then be constructed using simple equations involving the flow-field para
meters. I will illustrate that the flow-fields framework provides 'shortcut
s' for quantum\, classical as well as stochastic systems.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170411T141554Z
DTSTART:20170419T183000Z
DTEND:20170419T193000Z
UID:event1748@bu.edu
URL:http://physics.bu.edu/events/show/1748
SUMMARY:Chiral Floquet Phases
DESCRIPTION:Featuring Adrian Po\, Harvard University\n\nPart of the Condens
ed Matter Theory Seminar Series.\n\nPeriodically driven quantum systems\, a
ka Floquet problems\, have been recently identified as a prime platform for
the study of topologically nontrivial quantum dynamics. Absent the notion
of ground state(s)\, many-body localization plays a crucial role in the def
inition of such Floquet phases. Strikingly\, some of the discovered phases
are intrinsically dynamical\, in the sense that they do not admit static co
unterparts. In this talk\, I will describe our results on the study of chir
al phases in this context. First\, I will discuss an analog of the integer
quantum Hall phases\, where instead of charge or heat\, quantum information
is pumped along the edge in a unidirectional manner. Next\, I will present
an extension of this phase into one featuring intrinsic topological order\
, where the pumping of emergent Majorana fermions along the edge is\, surpr
isingly\, accompanied by a necessary dynamical anyon transmutation in the b
ulk
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170418T131720Z
DTSTART:20170426T150000Z
DTEND:20170426T160000Z
UID:event1745@bu.edu
URL:http://physics.bu.edu/events/show/1745
SUMMARY:Competition between Bose glass and superfluid phases in quantum ant
iferromagnets
DESCRIPTION:Featuring Sylvain Capponi\, Toulouse university & BU\nHosted by
: Anders Sandvik\n\nPart of the Condensed Matter Theory Seminar Series.\n\n
Building on recent NMR experiments [1]\, we theoretically investigate the h
igh magnetic field regime of the disordered quasi-one-dimensional S=1 antif
erromagnetic material DTNX. The interplay between disorder\, chemically con
trolled by Br-doping\, interactions\, and the external magnetic field\, lea
ds to a very rich phase diagram. Beyond the well-known antiferromagneticall
y ordered regime\, analog of a Bose condensate of magnons\, we unveil a res
urgence of phase coherence at higher field\, induced by the doping [2]. Suc
h a ``mini-condensation'' contrasts with previously reported Bose-glass phy
sics in the same regime and should be accessible to future experiments.\n\n
In a second part\, I will discuss recent findings regarding the one-dimensi
onal superfluid-Bose glass transition at T=0 in S=1/2 XXZ chain [3]. As a f
unction of interaction and disorder strength\, we identify a Berezinskii-Ko
sterlitz-Thouless critical line with two different regimes. At small attrac
tion where critical disorder is weak compared to the bandwidth\, the critic
al Luttinger parameter K takes its universal Giamarchi-Schulz value 3/2. Co
nversely\, a non-universal K>3/2 emerges for stronger attraction where weak
-link physics is relevant. In this strong disorder regime\, the transition
is characterized by self-similar power-law distributed weak links with a co
ntinuously varying characteristic exponent.\n\nRefs:\n[1] A. Orlova et al.\
, Phys. Rev. Lett. 118\, 067203 (2017)\n[2] M. Dupont\, S. Capponi\, N. Laf
lorencie\, Phys. Rev. Lett. 118\, 067204 (2017)\n[3] E. Doggen\, G. LemariÃ
©\, S. Capponi\, N. Laflorencie\, arXiv:1704.02257
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170427T154602Z
DTSTART:20170503T150000Z
DTEND:20170503T160000Z
UID:event1752@bu.edu
URL:http://physics.bu.edu/events/show/1752
SUMMARY:Glassy dynamics as a consequence of the equilibrium liquid to solid
transition
DESCRIPTION:Featuring Zohar Nussinov\, WUSTL\n\nPart of the Condensed Matte
r Theory Seminar Series.\n\nWe will review the underpinning of the micro-ca
nonical ensemble and the\nmore refined (and explicitly quantum) "Eigenstate
Thermalization\nHypothesis". We will then find and apply a simple corollar
y of these to\nanalyze the evolution of a liquid upon supercooling to form
a structural\nglass. Simple\ntheoretical considerations lead to a predictio
ns for general properties of\nsupercooled liquids. Amongst other things\, a
collapse of the viscosity of\nglass formers is predicted from this theory.
This collapse indeed occurs\nover 16 decades of relaxation times for all k
nown types of glass formers.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170502T152157Z
DTSTART:20170508T180000Z
DTEND:20170508T190000Z
UID:event1763@bu.edu
URL:http://physics.bu.edu/events/show/1763
SUMMARY:Topological Phase Transitions: From Duality Web to Symmetric Mass G
eneration
DESCRIPTION:Featuring Yi-Zhuang You\, Harvard University\n\nPart of the Con
densed Matter Theory Seminar Series.\n\nTopological phases of matter is an
active research area of condensed matter physics. Among various topics\, th
e symmetry protected topological (SPT) phases\, which are generalizations o
f topological insulators\, have attracted enormous theoretical interest in
the last few year. Much progress has been made in classifying and character
izing SPT phases. Yet another interesting topic is to study the phase trans
itions between different SPT phases. In this talk\, I will present a lattic
e model for (2+1)D bosonic SPT phases\, which is free of the sign problem a
nd can be explored by quantum Monte Carlo simulations. It turns out that th
e model demonstrates a rich phase diagram with exotic topological quantum p
hase transitions. In particular\, I will focus on two of these transitions
and report our on-going progress to understand them both theoretically and
numerically.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170508T133144Z
DTSTART:20170510T190000Z
DTEND:20170510T200000Z
UID:event1767@bu.edu
URL:http://physics.bu.edu/events/show/1767
SUMMARY:Stochastic Neural Networks for Machine Learning the Many-Body Probl
em
DESCRIPTION:Featuring Roger Melko\n\nPart of the Condensed Matter Theory Se
minar Series.\n\nCondensed matter physicists have a sophisticated array of
numerical\ntechniques that they use to study classical and quantum many-bod
y models. \nIn parallel\, the machine learning community has developed a ve
ry successful\nset of algorithms with the goal of classifying\, characteriz
ing and\ninterpreting complex sets of data\, such as images and natural lan
guage\nrecordings. We briefly show that standard neural networks architectu
res for\nsupervised learning can identify phases and phase transitions in a
variety\nof condensed matter Hamiltonians\, directly from raw state config
urations\nsampled with standard Monte Carlo and treated like images. Then\
, we show\nhow we can use such Monte Carlo configurations to train a stocha
stic variant\nof a neural network\, called a Restricted Boltzmann Machine (
RBM)\, for use in\nunsupervised learning applications. We demonstrate how
RBMs\, once trained\,\ncan be sampled much like a physical Hamiltonian to p
roduce configurations\nuseful for estimating physical observables\, as well
as other applications.\nFinally\, we explore the representational power of
RBMs\, and comment on their\napplication to the simulation of quantum syst
ems.
LOCATION: \, \,
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170515T161618Z
DTSTART:20170516T180000Z
DTEND:20170516T193000Z
UID:event1770@bu.edu
URL:http://physics.bu.edu/events/show/1770
SUMMARY:Qauntum chaos\, (diffusive) transport and random matrixes
DESCRIPTION:Featuring Anatoly Dymarsky\, UKY\nHosted by: Anatoli Polkovniko
v\n\nPart of the Condensed Matter Theory Seminar Series.\n\nAbstract: I wil
l discuss prospects and limitations of using random matrix models to descri
be transport in quantum chaotic systems
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20170625T203303Z
LAST-MODIFIED:20170601T181936Z
DTSTART:20170607T150000Z
DTEND:20170607T160000Z
UID:event1773@bu.edu
URL:http://physics.bu.edu/events/show/1773
SUMMARY:Out-of-time-order correlators in disordered quantum systems
DESCRIPTION:Featuring David J. Luitz\n\nPart of the Condensed Matter Theory
Seminar Series.\n\nOut-of-time-order correlators (OTOC) are used\nto study
the propagation of local information in isolated quantum systems.\nI will
discuss recent results using large scale exact time-evolution\nfor up to L=
31 spins 1/2 and show that for\nweakly disordered nonintegrable systems inf
ormation propagates behind\na ballistically moving front\, while the entang
lement entropy growths\nlinearly in time. For stronger disorder the motion
of the information\nfront is algebraic and sub-ballistic with a disorder st
rength\ndependent exponent which depends on the strength of the disorder\,\
nsimilarly to\nthe sublinear growth of the entanglement entropy. The\ndynam
ical exponent associated with the information front coincides\nwith the exp
onent of the growth of the entanglement entropy for both\nweak and strong d
isorder and the temporal\ndependence of the OTOC is characterized by a fast
nonexponential\ngrowth\, followed by a slow saturation after the passage o
f the\ninformation front. Finally\, I will mention the implications of this
\nbehavioral change on the growth of the entanglement entropy.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR