Centre de Physique Théorique


June 2019

Wednesday 19 June 14:00-15:00, CPT, Amphi 5

Singular limits solutions for a 2-dimensional elliptic system of Liouville type in some general case

Sami Baraket (Université de Tunis El-Manar)


We consider the existence of singular limit solutions for a nonlinear elliptic system of Liouville type with Dirichlet boundary conditions. We consider in particular the case, when the sets of singularities of solutions are intersecting. We use the nonlinear domain decomposition method and a Pohozaev type identity.

Tuesday 25 June 11:00-12:00, Amphi 5 du CPT

Theoretical and experimental studies on collective cell dynamics

Shao-Zhen Lin (Tsinghua University, Beijing, China).

Abstract: Collective cell dynamics exists extensively and plays key regulating roles in vast physiological or pathological processes including embryo development, wound healing, and tumor invasion. It involves the dynamic self-assembly of intracellular cytoskeleton, the regulation of biochemical signaling pathways, as well as the interactions among cells and those between cells and microenvironment, making it a challenging frontier topic in biophysics. Via combining experiments, theory, and simulations, I study collective cell dynamics in confluent cell monolayer systems. In this talk, I’ll present my primary research on collective cell dynamics during my PhD career. My work can be mainly divided into three parts as below.
Firstly, I investigate the velocity distribution statistics of collective cell migration in 2D cell monolayer systems. Through live-cell imaging experiments and PIV analysis, I find that cell velocities in 2D monolayers obey the q-Gaussian distribution. The velocity distribution statistics keeps almost invariant during the jamming transition of cell monolayers and has no apparent dependence on cell type and substrate stiffness, revealing its universality.
Secondly, collective cell migration on both planar and curved substrates are studied based on a proposed active vertex model. The regulating roles of intercellular social interactions and geometric constraints on collective migration modes, characteristic scales, and density fluctuations in cell monolayers are elucidated.
Thirdly, a chemomechanical model is established to investigate the collective morphodynamics in 2D cell monolayer systems. Taking the collective shape oscillations in Drosophilaamnioserosa as a typical example, I study the pattern, polarization, and synchronization of collective cell oscillations. Further, the regulating roles of mechanical forces and boundary constraints are deciphered.

Wednesday 26 June 11:00-12:00, CPT, Amphi 5

Wave turbulence and asymptotic for singular integrals

Serguei Kuksin (UPMC)


I will discuss the stochastic model for the wave turbulence due
to Zakharov-L’vov, explain that the corresponding problem of decomposing
the energy spectrum to formal series in the properly scaled small
amplitude leads to asymptotic questions for a class of singular
integrals and show how to calculate this asymptotic. Finally I will
explain how these results allow to obtain the kinetic approximation for
the energy spectrum.

Friday 28 June 14:00-15:00, Amphi 5

Quantum gravity from fakeons

Damiano Anselmi (University of Pisa)

A new quantization prescription is able to endow quantum field theory with a new type of "particle", the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive fakeon of spin 2 (together with a scalar field) allows us to build a theory of quantum gravity that is both renormalizable and unitary, and to some extent unique. After presenting the general properties of this theory, I discuss its classical limit, which carries important remnants of the fakeon quantization prescription. I also discuss the possibility that the Higgs boson might be a fakeon.