eigenbases Definition and 1 Threads

Consider an infinite well between ##0## and ##a##, the energy eigen functions are: $$\phi(x)=\sqrt{\frac 2 a}\sin{\frac{n\pi x}a}$$ Since the Hamiltonian of this system is only a function of momentum operator ##(\hat H=\hat p^2/2m)##, we should be able to find a common energy and momentum...