Seminars 2017
Seminar
Friday, November 17
Entanglements in heterogeneous polymers
Institut LaueLangevin, Grenoble
Abstract
The dynamics of polymer melts and concentrated
solutions depend strongly of the molecular weight of
the polymer chains. The main effect of increasing
molecular weight is the apparition of topological
constraints between the chains called entanglements.
These constraints dramatically change physical
properties such as viscosity, dynamics, rheology and
the mechanical behavior. Despite its importance, there
are still open fundamental questions about the physics
of entanglements. Due to many technical issues,
building appropriates and practical approaches to
simulate entanglements that help to tackle these open
problems is a longstanding challenge. In this work, we
show how a novel and promising coarsegraining for
simulating entangled polymers can be successfully used
to study topological constraints in heterogeneous
systems like polymer melts under strong confinement
(thin films) and nanostructured block copolymers, both
important regarding basic research and technological
applications.
The seminar will take place at 13:00 in classroom
2.0.D14 (Edificio Sabatini) Universidad Carlos III
Seminar
Friday, November 3
Summation of divergent series: An invention of the
devil or a blessing for physics?
Instituto de Estructura de la Materia (CSIC)
Abstract
Divergent series play an interesting and important role
in Physics. The purpose of the talk is to review the
main summation methods for these objects and explain
their main features. Special attention will be devoted
to abstract summation. Other issues related to the use
of series in Physics (in particular the conditionally
convergent ones) will be discussed.
The seminar will take place at 13:00 in classroom
2.0.D14 (Edificio Sabatini) Universidad Carlos III
Seminar
Tuesday, October 31
Fluctuations in stochastic systems with memory
Queen Mary University of London
Abstract
I will give a gentle introduction to the effects of
longrange temporal correlations in stochastic particle
systems, focusing particularly on fluctuations about
the typical behaviour. Specifically, in the first part
of the talk, I will discuss how longrange memory
dependence can modify the large deviation principle
describing the probability of rare currents and lead,
for example, to superdiffusive behaviour. In the second
part, I will describe a more interdisciplinary project
incorporating the psychological "peakend" heuristic
for human memory into a simple discrete choice model
from economics. Along the way, I will attempt to
indicate connections between different approaches, as
well as mentioning recent work on the implementation of
the "cloning" procedure for evaluation of large
deviations in nonMarkovian processes.
The seminar will take place at 14:00 in classroom
2.0.D14 (Edificio Sabatini) Universidad Carlos III
Seminar
Monday, September 18
Harnessing symmetry to control quantum transport
Universidad de Granada
Abstract
Controlling transport in quantum systems holds the key
to many promising quantum technologies. Here we review
the power of symmetry as a resource to manipulate
quantum transport, and apply these ideas to engineer
novel quantum devices. Using tools from open quantum
systems and large deviation theory, we show that
symmetrymediated control of transport is enabled by a
pair of twin dynamic phase transitions in current
statistics, accompanied by a coexistence of different
transport channels. By playing with the symmetry
decomposition of the initial state, one can modulate
the importance of the different transport channels and
hence control the flowing current. Motivated by the
problem of energy harvesting we illustrate these ideas
in open quantum networks, an analysis which leads to
the design of a symmetrycontrolled quantum thermal
switch. We review an experimental setup recently
proposed for symmetrymediated quantum control in the
lab based on a linear array of atomdoped optical
cavities, and the possibility of using transport as a
probe to uncover hidden symmetries, as recently
demonstrated in molecular junctions, is also discussed.
Overall, these results demonstrate the importance of
symmetry not only as a organizing principle in physics
but also as a tool to control quantum systems.
[1] D. Manzano and P.I. Hurtado. ArXiv:1707.07895 (2017).
The seminar will take place at 13:00 in classroom
2.3.B03 (Edificio Sabatini) Universidad Carlos III
Seminar
Tuesday, September 12
Topological properties of a dense atomic lattice gas
University of Nottingham
Abstract
We investigate the existence of topological phases in a
dense twodimensional atomic lattice gas. The coupling
of the atoms to the radiation field gives rise to
dissipation and a nontrivial coherent longrange
exchange interaction whose form goes beyond a simple
powerlaw. The farfield terms of the potential  which
are particularly relevant for atomic separations
comparable to the atomic transition wavelength  can
give rise to energy spectra with onesided divergences
in the Brillouin zone. The longranged character of the
interactions has another important consequence: it can
break the standard bulkboundary relation in
topological insulators. We show that topological
properties such as the transport of an excitation along
the edge of the lattice are robust with respect to the
presence of lattice defects and dissipation. The latter
is of particular relevance as dissipation and coherent
interactions are inevitably connected in our setting.
The seminar will take place at 12:00 in classroom
2.0.D14 (Edificio Sabatini) Universidad Carlos III
Seminar
Tuesday, May 9
TightBinding Model Realized with Coupled Acoustic
Resonators
Hong Kong University of Science and Technology
Abstract
Tightbinding model is a simple yet powerful method
that can be used to study electronic band structures in
solidstate physics. The method considers only the
hopping, or the coupling, among the most adjacent
atomic wavefunctions. In this talk, I will show that
tightbinding model can be faithfully reproduced by
using coupled acoustic resonators. Based on such a
convenient platform, we are able to experimentally
investigate novel physics that arises therein. Two
examples will be discussed. As the first example, we
consider a 4by4 nonHermitian matrix, and study the
complex behaviors of the eigenfrequencies, including
formation and coalescence of multiple exceptional
points upon the variation of system parameters [1].
Second, we construct a SuSchriefferHeeger (SSH)
dimerized chain using the similar acoustic cavities.
Band inversion, together with a change in (quantized)
Zak phase can be realized. An interface system can be
constructed using two SSH chains with different Zak
phases. By coupling two of such interface systems
together; we obtain a new system with a fivesite unit
cell. For such a system, a specific separation of the
5by5 Hamiltonian into a topological subspace and a
nontopological subspace can be found. By tuning the
system parameters, the topological interface state,
which exists in the topological subspace, can be
embedded into a band continuum, which resides in the
nontopological subspace. This gives rise to a new type
of bound states in the continuum [2].
[1] Ding, K., Ma, G., Xiao, M., Zhang, Z.Q. and
Chan, C. T. Emergence, coalescence, and topological
properties of multiple exceptional points and their
experimental realization. Phys. Rev. X 6, 021007
(2016).
The seminar will take place at 13:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III
Seminar
Wednesday, May 3
Identification of cancer related genes using a
comprehensive map of human gene expression
UC3M
Abstract
The development of highthroughput techniques for gene
expression profiling over the last two decades has
rapidly led to the accumulation of vast amounts of
datasets, which are available in public repositories.
This has enabled largescale metaanalyses of combined
data to provide new biological insights, including the
identification of new cancer genes. We compiled a human
gene expression dataset from over 40000 microarrays.
After strict quality control and data normalisation the
data was quantified in an expression matrix of $\sim
20,000$ genes and $\sim 28,000$ samples, where we
identified groups like normal tissues, neoplasmic
tissues, cell lines and incompletely differentiated
cells. Several unsupervised analyses of the data
confirmed a global structure of the gene expression,
which was consistent with earlier analyses, but with
more details revealed due to the increased resolution.
We suggested a suitable mixedeffects linear model for
gene expression, which was used to further investigate
it in solid tissue tumours, and to compare these with
the respective healthy solid tissues. Our analysis
identified 1285 genes with a systematic expression
change in cancer. The list was significantly enriched
with known cancer genes from large, peerreviewed
databases, whereas the remaining ones were proposed as
new cancer gene candidates.
The seminar will take place at 13:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III
Seminar
Tuesday, April 4
Application of thermal boundary conditions at the
microscale: A means for flow generation and control
Faculty of Aerospace Engineering at the Technion
(Israel)
Abstract
In marked difference from incompressible fluid flows,
microscale gas flows commonly couple the dynamic and
thermodynamic fluid descriptions, through the
combination of bulkflow evolution and external
boundary conditions. Yet, while the thermal boundary
conditions have a significant effect on the generated
flows, traditional studies on rarefied gas systems have
been limited to gassurface interactions where the
surfaces temperatures are prescribed. Such an
assumption, however, seems of little practical value,
as the surface temperature at any experimental setup
can only be imposed indirectly through a direct
prescription of the boundary heatflux. To examine this
observation, the present work demonstrates the impact
of replacing an isothermal surface condition with a
heatflux condition in a variety of onedimensional and
unsteady microflow setups. These include gasflow
animation problems, acoustic wave propagation, and
active flow control applications. Possible extensions
to higherdimension configurations, including
sheardriven flows and hydrodynamic instability
problems, are also reviewed.
The seminar will take place at 11:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III
Seminar
Wednesday, March 15
Acoustic wave propagation in granular media: rotation
and nonlinearities
UC3M
Abstract
Granular materials are considered as a complex media
when elastic waves propagates in the bulk. This
complexity comes from their microinhomogeneous
character and from the highly nonlinear behavior of the
contact between the particles. Compared to the
classical elastic solids, one major difference is due
to the importance of the rotational degrees of freedom
of each particle for the description of the elastic
behavior of the media. In this work, the effects of the
rotational degrees of freedom are shown through
theoretical predictions, numerical simulations and
experimental results. Nonlinear wave propagation
phenomena also happen in granular materials. Two
examples are presented. The first one is the asymmetry
of the nonlinear wave generation in a granular crystal
submitted to gravity. The second one is the study of
one single contact sphereplane as a nonlinear
resonator.
The seminar will take place at 13:00 in classroom
2.1.C19 (Edificio Sabatini) Universidad Carlos III


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