2017-2018 ICFP seminar Program

Quick links

Quick links

Next student seminar :
Access to the program

Here you can find information about your internships:
Experimental Internship - Undergraduate program
Master ICFP first year Internship
Master ICFP second year Internship

News : ICFP Research seminars
November 6 - 10, 2017 :

All information about the program

2017-2018 Calendars :
Undergraduate program
Master ICFP 1st year
Master ICFP 2nd year

Contact us - Student support and Graduate School office :
Tél : 01 44 32 35 61
enseignement@phys.ens.fr

The seminar takes place on Tuesday, at 5:15pm.

 September 26: Erwan Allys

Seminar room: CONF4 (salle E244) - 24 rue Lhomond

Laboratoire de Radioastronomie, ENS Paris
Probing Grand Unified Theories with topological defects in Cosmology

Cosmic strings are linear topological defects which are expected to form during the spontaneous symmetry breaking of a Grand Unified Theory in the early universe. They could allow us to observationally probe particle physics up to energies of 10^16 GeV. The idea of this talk is to explain what are cosmic strings, and why we expect them to be formed in the standard cosmological scenario, before to discuss the current challenges linked with their observation. In a first part, we will present the concept of local symmetries in particles physics, the Standard Model, and explain why Grand Unified Theories are attractive models to describe physics at very high energies. In a second part, we will present in a broad manner the concepts of topological defect, considering both the cases of domain walls and cosmic strings/vortex lines. We fill finally discuss the formation and evolution of a cosmological lattice of cosmic strings, as well as the associated observational studies.

 October 10: Jean-Francois Rupprecht

Seminar room: Amphi Jaurès - 29 rue d’Ulm

Mechanobiology Institute, National University of Singapore
Grab-and-pull: from motors pinching to nuclear shaking and organ shaping

Cells sense the rigidity of their environment through local pinching exerted by bundles of myosin motors contracting over actin filaments. Recent experiments have shown that the motors within these bundles are surprisingly efficient, exerting forces that are way larger than the classically reported value of 5pN/motor. We interpret this high force generation based on a new molecular motor model, whereby a two-state potential describes the interaction of the myosin head over the two strands of the actin filament. Our mean-field description predicts that the collective dynamics of motors has features of a first order transition. The dynamics of motors has a strong stochastic component, which has been shown experimentally to lead to cell-scale stress fluctuations. We investigate the role of these fluctuations on the stochastic dynamics of an inclusion embedded in an active viscous gel. We show that, in non-equilibrium systems, stress fluctuations give rise to an effective attraction towards the boundaries of the confining domain. We apply our result to the dynamics of deformations of the cell nucleus and we demonstrate the appearance of a fluctuation maximum at a critical level of myosin motor activity, in agreement with experiments. Moving further to larger length scales, we consider the role of myosin motor contractility in organ formation. We model how, during embryogenesis, muscle segments of the zebrafish acquire their characteristic V-shape.

 November 7: Joshua McGraw

Seminar room: Amphi Dussane - 45 rue d’Ulm

Département de Physique, ENS Paris
Friction at the interface between solid selfassembled monolayers and liquid polymers or solid metal nanotips

The friction between a solid and a liquid was historically assumed to be so large that fluid molecules in contact with a solid boundary were stuck. Thus, the classical no-slip boundary condition was applied. With the advent of micro- and nano-fluidics in the last decades, however, this boundary condition has been observed to fail in many instances. Particularly, as will be discussed here, a slip boundary condition is observed when unentangled polystyrene (PS) dewets from a hydrophobic, alkylsilane self-assembled monolayer (SAM). This boundary condition can furthermore be tuned over an order of magnitude by subtly changing the SAM [1], indicating that the friction between solid and liquid is highly sensitive to atomic level details. We have also investigated the friction between these same SAMs and a solid metal tip of nanoscopic dimensions. Remarkably, this apparent solid/solid friction is velocity dependent and exhibits a crossover from a linear to logarithmic scaling in the velocity [2]. The results can be described in terms of a distribution of nanocontacts with very weak stiffness compared to the expected one for metal/solid contacts. The work presented here has been done in collaboration with the authors of refs. [1, 2].

1. J.D. McGraw, M. Klos, A. Bridet, H. Hä̈hl, M. Paulus, J.M. Castillo, M. Horsch, K.Jacobs, J. Chem. Phys. 146, 203326 (2017).
2. J.D. McGraw, A. Nigues, A. Siria, Nano Letters, 17, 6335 (2017).

 November 21: Bruno Laburthe-Tolra

Seminar room: Amphi Jaurès - 29 rue d’Ulm

Laboratoire de Physique des Lasers, Université Paris 13
Dipolar quantum gases and magnetism

I will describe an experiment performed with ultra-cold chromium atoms. These atoms interact rather strongly via dipole-dipole interactions. I will discuss the out-of-equilibrium spin dynamics driven by these interactions, and focuss on two cases in which our very complex many-body quantum system can be described by surprisingly simple equations.

 December 5: Kenneth Maussang

Seminar room: Amphi Jaurès - 29 rue d’Ulm

Institut d’Électronique et des Systèmes, Université de Montpellier

 December 19: Gabriel Hétet

Seminar room: Amphi Jaurès - 29 rue d’Ulm

Laboratoire Pierre Aigrain, ENS Paris

Quick links

Next student seminar :
Access to the program

Here you can find information about your internships:
Experimental Internship - Undergraduate program
Master ICFP first year Internship
Master ICFP second year Internship

News : ICFP Research seminars
November 6 - 10, 2017 :

All information about the program

2017-2018 Calendars :
Undergraduate program
Master ICFP 1st year
Master ICFP 2nd year

Contact us - Student support and Graduate School office :
Tél : 01 44 32 35 61
enseignement@phys.ens.fr