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Non prolongement unique des solutions d'opérateurs «somme de carrés»

Hajer Bahouri (1986)

Annales de l'institut Fourier

Dans ce travail, nous avons montré que si P = i = 1 n - 1 x i 2 , où les x i sont des champs de vecteurs C linéairement independants dans un ouvert Ω de R n tels que l’algèbre de Lie qu’ils engendrent soit de rang maximum en tout point et la forme volume qu’on leur associe soit de classe 4 en un point x 0 de Ω , alors il existe un voisinage ouvert V de x 0 et une fonction a C ( V ) tels que P + a possède pas la propriété de prolongement unique.

Nonanalyticity of solutions to t u = ² x u + u ²

Grzegorz Łysik (2003)

Colloquium Mathematicae

It is proved that the solution to the initial value problem t u = ² x u + u ² , u(0,x) = 1/(1+x²), does not belong to the Gevrey class G s in time for 0 ≤ s < 1. The proof is based on an estimation of a double sum of products of binomial coefficients.

Non-autonomous 2D Navier–Stokes system with a simple global attractor and some averaging problems

V. V. Chepyzhov, M. I. Vishik (2002)

ESAIM: Control, Optimisation and Calculus of Variations

We study the global attractor of the non-autonomous 2D Navier–Stokes system with time-dependent external force g ( x , t ) . We assume that g ( x , t ) is a translation compact function and the corresponding Grashof number is small. Then the global attractor has a simple structure: it is the closure of all the values of the unique bounded complete trajectory of the Navier–Stokes system. In particular, if g ( x , t ) is a quasiperiodic function with respect to t , then the attractor is a continuous image of a torus. Moreover the...

Non-autonomous 2D Navier–Stokes system with a simple global attractor and some averaging problems

V. V. Chepyzhov, M. I. Vishik (2010)

ESAIM: Control, Optimisation and Calculus of Variations

We study the global attractor of the non-autonomous 2D Navier–Stokes system with time-dependent external force g(x,t). We assume that g(x,t) is a translation compact function and the corresponding Grashof number is small. Then the global attractor has a simple structure: it is the closure of all the values of the unique bounded complete trajectory of the Navier–Stokes system. In particular, if g(x,t) is a quasiperiodic function with respect to t, then the attractor is a continuous image...

Non-existence of global classical solutions to 1D compressible heat-conducting micropolar fluid

Jianwei Dong, Junhui Zhu, Litao Zhang (2024)

Czechoslovak Mathematical Journal

We study the non-existence of global classical solutions to 1D compressible heat-conducting micropolar fluid without viscosity. We first show that the life span of the classical solutions with decay at far fields must be finite for the 1D Cauchy problem if the initial momentum weight is positive. Then, we present several sufficient conditions for the non-existence of global classical solutions to the 1D initial-boundary value problem on [ 0 , 1 ] . To prove these results, some new average quantities are...

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