Consider the following linear (Hamiltonian) operator on functions on the real line $\mathbb{R}$ $$H\psi(x)=-\frac{d^2}{dx^2}\psi(x)+V(x)\psi(x).$$
Assume that $V$ is a smooth function and $V(x)\to +\infty$ as $|x|\to +\infty$.
Is it true that the spectrum of $H$ is discrete? In my case $V$ is a polynomial of fourth degree. If the answer is negative in general, is it positive in my case?