Extremizers for the Strichartz Inequality for a Fourth-Order Schr\"odinger Equation
In this paper, we consider the Strichartz inequality for a fourth-order Schr\"odinger equation on $\mathbb{R}^3$. We show that extremizers exist using a linear profile decomposition. Based on the existence of extremizers, we use the associated Euler-Lagrange equation to show that the extremizers have exponential decay and consequently must be analytic. Furthermore, we also prove that extremizers must have the even property $|\widehat{f}(\xi)|=|\widehat{f}(-\xi)|$ almost everywhere.