Remarks on the Liouville type problem in the stationary 3D Navier-Stokes equations

We study the Liouville type problem for the stationary 3D Navier-Stokes equations on $\Bbb R^3$. Specifically, we prove that if $v$ is a smooth solution to (NS) satisfying $\omega={\rm curl}\,v \in L^q (\Bbb R^3)$ for some $\frac32 \leq q< 3$, and $|v(x)|\to 0$ as $|x|\to +\infty$, then either $v=0$ on $\Bbb R^3$, or $\int_{\Bbb R^6} \Phi_+ dxdy=\int_{\Bbb R^6} \Phi_- dxdy=+\infty$, where $\Phi(x,y) :=\frac{1}{4\pi}\frac{\omega (x)\cdot(x-y)\times (v(y)\times \omega(y) )}{|x-y|^3}$, and $\Phi_\pm:=\max\{ 0, \pm \Phi\}$. The proof uses crucially the structure of nonlinear term of the equations.Comment: 12 page

Liouville type of theorems with weights for the Navier-Stokes equations and the Euler equations

We study Liouville type of theorems for the Navier-Stokes and the Euler equations on $\Bbb R^N$, $N\geq 2$. Specifically, we prove that if a weak solution $(v,p)$ satisfies $|v|^2 +|p| \in L^1 (0,T; L^1(\Bbb R^N, w_1(x)dx))$ and $\int_{\Bbb R^N} p(x,t)w_2 (x)dx \geq0$ for some weight functions $w_1(x)$ and $w_2 (x)$, then the solution is trivial, namely $v=0$ almost everywhere on $\Bbb R^N \times (0, T)$. Similar results hold for the MHD Equations on $\Bbb R^N$, $N\geq3$.Comment: 17 page

On the nonexistence of global weak solutions to the Navier-Stokes-Poisson equations in RN\Bbb R^N

In this paper we prove nonexistence of stationary weak solutions to the Euler-Poisson equations and the Navier-Stokes-Poisson equations in $\Bbb R^N$, $N\geq 2$, under suitable assumptions of integrability for the density, velocity and the potential of the force field. For the time dependent Euler-Poisson equations we prove nonexistence result assuming additionally temporal asymptotic behavior near infinity of the second moment of density. For a class of time dependent Navier-Stokes-Poisson equations this asymptotic behavior of the density can be proved if we assume the standard energy inequality, and therefore the nonexistence of global weak solution follows from more plausible assumption in this case.Comment: 27 page

Relative decay conditions on Liouville type theorem for the steady Navier-Stokes system

In this paper we prove Liouville type theorem for the stationary Navier-Stokes equations in $\Bbb R^3$ under the assumptions on the relative decays of velocity, pressure and the head pressure. More precisely, we show that any smooth solution $(u,p)$ of the stationary Navier-Stokes equations satisfying $u(x) \to 0$ as $|x|\to +\infty$ and the condition of finite Dirichlet integral $\int_{\Bbb R^3} | \nabla u|^2 dx <+\infty$ is trivial, if either $|u|/|Q|=O(1)$ or $|p|/|Q| =O(1)$ as $|x|\to \infty$, where $|Q|=\frac12 |u|^2 +p$ is the head pressure.Comment: 9 page

Remarks on regularity conditions of the Navier-Stokes equations

Let $v$ and \o be the velocity and the vorticity of the a suitable weak solution of the 3D Navier-Stokes equations in a space-time domain containing $z_0 =(x_0, t_0)$, and $Q_{z_0, r} =B_{x_0, r}\times (t_0-r^2, t_0)$ be a parabolic cylinder in the domain. We show that if v\times \frac{\o}{|\o|}\in L^{\gamma, \alpha}_{x,t} (Q_{z_0, r}) or {\o}\times \frac{v}{|v|}\in L^{\gamma, \alpha}_{x,t} (Q_{z_0, r}), where $L^{\gamma, \alpha}_{x,t}$ denotes the Serrin type of class, then $z_0$ is a regular point for $v$. This refines previous local regularity criteria for the suitable weak solutions.Comment: 13 page

Continuation of the zero set for discretely self-similar solutions to the Euler equations

We are concerned on the study of the unique continuation type property for the 3D incompressible Euler equations in the self-similar type form. Discretely self-similar solution is a generalized notion of the self-similar solution, which is equivalent to a time periodic solution of the time dependent self-similar Euler equations. We prove the unique continuation type theorem for the discretely self-similar solutions to the Euler equations in $\Bbb R^3$. More specifically, we suppose there exists an open set $G\subset \Bbb R^3$ containing the origin such that the velocity field $V\in C_s^1C^{2}_y (\Bbb R^{3+1})$ vanishes on $G\times (0, S_0)$, where $S_0 > 0$ is the temporal period for $V(y,s)$. Then, we show $V(y,s)=0$ for all $(y,s)\in \Bbb R^{3+1}$. Similar property also holds for the inviscid magnetohydrodynamic systemComment: 16 pages. arXiv admin note: text overlap with arXiv:1308.105

Euler's equations and the maximum principle

In this paper we use maximum principle in the far field region for the time dependent self-similar Euler equations to exclude discretely self-similar blow-up for the Euler equations of the incompressible fluid flows. Our decay conditions near spatial infinity of the blow-up profile are given explicitly in terms the coefficient in the equations. We also deduce triviality of the discretely self-similar solution to the magnetohydrodynamic system(MHD), under suitable decay conditions near spatial infinity than the previous one. Applying similar argument directly to the Euler equations, we obtain a priori estimate of the vorticity in the far field region.Comment: 15 page

Remarks on the asymptotically discretely self-similar solutions of the Navier-Stokes and the Euler equations

We study scenarios of self-similar type blow-up for the incompressible Navier-Stokes and the Euler equations. The previous notions of the discretely (backward) self-similar solution and the asymptotically self-similar solution are generalized to the locally asymptotically discretely self-similar solution. We prove that there exists no such locally asymptotically discretely self-similar blow-up for the 3D Navier-Stokes equations if the blow-up profile is a time periodic function belonging to $C^1(\Bbb R ; L^3(\Bbb R^3)\cap C^2 (\Bbb R^3))$. For the 3D Euler equations we show that the scenario of asymptotically discretely self-similar blow-up is excluded if the blow-up profile satisfies suitable integrability conditions.Comment: 11 pages(to appear in J. Nonlinear Analysis

On the blow-up problem for the axisymmetric 3D Euler equations

In this paper we study the finite time blow-up problem for the axisymmetric 3D incompressible Euler equations with swirl. The evolution equations for the deformation tensor and the vorticity are reduced considerably in this case. Under the assumption of local minima for the pressure on the axis of symmetry with respect to the radial variations we show that the solution blows-up in finite time. If we further assume that the second radial derivative vanishes on the axis, then system reduces to the form of Constantin-Lax-Majda equations, and can be integrated explicitly.Comment: 11 page

Notes on the Liouville type problem for the stationary Navier-Stokes equations in R3\Bbb R^3

In this paper we study the Liouville type problem for the stationary Navier-Stokes equations in $\Bbb R^3$. We deduce an asymptotic formula for an integral involving the head pressure, $Q=\frac12 |v|^2 +p$, and its derivative over domains enclosed by level surfaces of $Q$. This formula provides us with new sufficient condition for the triviality of solution to the Navier-Stokes equations.Comment: 7 page