
Date Time 
Location  Speaker 
Title – click for abstract 

01/23 3:00pm 
BLOC 302 
Yiran Hu University of Texas at Austin 
Global in time solutions to a family of 3D QuasiGeostrophic Systems
Geophysicists have studied 3D QuasiGeostrophic systems extensively. These systems describe stratified atmospheric flows on a large time scale and are widely used for forecasting atmospheric circulation. They couple an inviscid transport equation in $\mathbb{R}_{+}\times\Omega$ with an equation on the boundary satisfied by the trace, where $\Omega$ is either $2D$ torus or a bounded domain in $\rt$. In this talk, I will show the existence and some regularity results of global in time solutions to a family of singular 3D quasigeostrophic systems with Ekman pumping, where the background density profile degenerates at the boundary. The main difficulty is handling the degeneration of the background density profile at the boundary. 

02/27 3:00pm 
BLOC 302 
Claude Bardos Laboratoire J.L.Lions 
About large medium and shortime behavior of solutions of the collision of the Vlasov equation
TBA 

02/27 4:00pm 
BLOC 302 
Matthias Hieber Technische Universität Darmstadt 
Analysis of Nematic Liquid Crystal Flows: The EricksenLeslie and the QTensor Model
In this talk we consider two models describing the flow of nematic liquid crystals: the EricksenLeslie model and the Qtensor model. We discuss local as well as global wellposedness results for strong solutions in the incompressible and compressible setting and investigate as well equlibrium sets and the longtime behaviour of solutions. This is joint work with A. Hussein, J. Pruss and M. Wrona. 

03/19 3:00pm 
BLOC 302 
Marita Thomas Freie Universitaet  Berlin 
Analysis of a model for viscoelastoplastic twophase flows in geodynamics
A model for an incompressible fluid of both viscoelastic and viscoplastic behavior is revisited, which is used in geodynamics, e.g., to describe the evolution of fault systems in the lithosphere on geological time scales. The Cauchy stress of this fluid is composed of a viscoelastic Stokeslike contribution and of an additional internal stress. The model thus couples the momentum balance with the evolution law of this extra stress, which features the ZarembaJaumann timederivative and a nonsmooth viscoplastic dissipation mechanism. This model is augmented to the situation of a biphasic material that undergoes phase separation according to a CahnHilliardtype evolution law. Suitable concepts of weak solutions are discussed for the coupled
model. This is joint work with Fan Cheng (FU Berlin) and Robert Lasarzik (WIAS and FU Berlin) within project C09 'Dynamics of rock dehydration on multiple scales' of CRC 1114 'Scaling Cascades in Complex Systems' funded by the German Research Foundation.


03/22 1:50pm 
BLOC 302 
Daniel Boutros University of Cambridge 
On energy conservation for inviscid hydrodynamic equations: analogues of Onsager's conjecture
Onsager's conjecture states that 1/3 is the critical spatial (Hölder) regularity threshold for energy conservation by weak solutions of the incompressible Euler equations. We consider an analogue of Onsager's conjecture for the inviscid primitive equations of oceanic and atmospheric dynamics. The anisotropic nature of these equations allows us to introduce new types of weak solutions and prove a range of independent sufficient criteria for energy conservation. Therefore there probably is a 'family' of Onsager conjectures for these equations.
Furthermore, we employ the method of convex integration to show the nonuniqueness of weak solutions to the inviscid and viscous primitive equations (and also the Prandtl equations), and to construct examples of solutions that do not conserve energy in the inviscid case. Finally, we present a regularity result for the pressure in the Euler equations, which is of relevance to the Onsager conjecture in the presence of physical boundaries. As an essential part of the proof, we introduce a new weaker notion of pressure boundary condition which we show to be necessary by means of an explicit example. These results are joint works with Claude Bardos, Simon Markfelder and Edriss S. Titi. 

03/26 3:00pm 
BLOC 302 
Dehua Wang University of Pittsburgh 
Hyperbolic and mixedtype problems in gas dynamics and geometry
We shall consider the hyperbolic and mixedtype problems arising in gas dynamics and geometry. In particular, the transonic flows past obstacles and in nozzles as well as the isometric embedding in geometry will be discussed. 

04/09 3:00pm 
BLOC 302 
Yeyu Zhang Shanghai University of Finance and Economics 
Coupled Nonlinear Evolution and Inverse Energy Transfer in Moist Boussinesq Dynamics
The interaction between slow and fast components in geophysical fluid dynamics, especially under the influence of phase changes, poses significant analytical challenges. Our study develops a fastwave averaging framework for the moist Boussinesq system, expanding past dry dynamics to include phase changes between water vapor and liquid water. We examine whether these phase transitions induce coupling between slow and fast waves or if the slow component evolves independently. Numerical simulations with a range of Froude and Rossby numbers reveal that phase changes may disrupt the proportionality of wave influence on the slow component, evidenced by a nonzero timeaveraged wave component due to phase transitions. Furthermore, inverse energy transfer to larger scales is investigated in rotating and stratified flows, including water effects and rapid cloud microphysics. The findings could imply that potential vorticity, phase boundaries, and vertical velocity contribute to the formation of coherent structures in strongly rotated and stratified flows, appearing to indicate a revision to the traditional view of energy cascades in geophysical fluids. 

04/09 4:00pm 
BLOC 302 
Ricardo Alonso Texas A&M University  Qatar 
An energy method for the Boltzmann equation: Higher integrability and boundedness of solutions
We cover in detail an argument for proving higher integrability and uniform boundedness for solutions of the homogeneous Boltzmann equation. Techniques are reminiscent of the level set De Giorgi's method for classical elliptic/parabolic PDE. A rough idea of the method's implementation for the spatially inhomogenous problem is discussed at the end.


04/16 04:00am 
BLOC 302 
Angeliki Menegaki Imperial College London 
Nonequilibrium Steady States in a BGK Model for Dilute Gases
We study the BGK equation on the 1D torus coupled to a spatially inhomogeneous thermostat, which models heat transfer in gases and remains out of equilibrium due to the action of the thermostat. We study properties of stationary solutions, also known as nonequilibrium steady states. We will discuss the existence, uniqueness and linear dynamical stability of spatially inhomogeneous steady states. This is based on a joint work with Jo Evans (University of Warwick). 

04/16 3:00pm 
BLOC 302 
Aseel Farhat Florida State University 
Impact of Rotation on the Regularity and Behavior of NavierStokes Solutions
In this presentation, we will address into the regularity challenges posed by the threedimensional (3D) NavierStokes equations (NSE) and explore the influence of planetary rotation. Additionally, we will discuss an upper bound on the Hausdorff dimension of the global attractor associated with the 2D NavierStokes equations on the betaplane, which depends on the rotation rate (referred to as the Rossby number). Our findings align with outcomes observed in numerical experiments, suggesting that rotation tends to induce a more zonal solution. 

04/30 3:00pm 
BLOC 302 
Slim Ibrahim Univeristy of Victoria 
TBA
TBA 

04/30 4:00pm 
BLOC 302 
Quyuan Lin Clemson University 
TBA
TBA 