On the global behaviors for defocusing semilinear wave equations in $mathbb{R}^{1+2}$

In this paper, we study the asymptotic decay properties for defocusing semilinear wave equations in $mathbb{R}^{1+2}$ with pure power nonlinearity. By applying new vector fields to null hyperplane, we derive improved time decay of the potential energy, with a consequence that the solution scatters both in the critical Sobolev space and energy space for all $p>1+sqrt{8}$. Moreover combined with Br{e}zis-Gallouet-Wainger type of logarithmic Sobolev embedding, we show that the solution decays pointwise with sharp rate $t^{-frac{1}{2}}$ when $p>frac{11}{3}$ and with rate $t^{ -frac{p-1}{8}+epsilon }$ for all $1<pleq frac{11}{3}$. This in particular implies that the solution scatters in energy space when $p>2sqrt{5}-1$.