Remarks on shear flows of the Euler equations

The gradient estimates for renormalization solutions to the Euler equations are derived. The proof is based on the boundedness of the solutions to the linear transport equation, component-wisely. A shear flow is a unique globally-in-time strong solution in certain class due to the argument of renormalization solutions. Shear flows give lower bounds for gradient estimates as well as the analyticity rate. The threshold between locally well-posedness and ill-posedness of the Euler equations is clarified in terms of functions spaces of initial data.