# Divergence of integral over vacuum energies (Free field)

1. Aug 24, 2015

### soviet1100

Hi,

The Hamiltonian for the free scalar field, expressed in terms of the creation/annihilation operators, is

$H = \int d^{3}p [\omega_p a^{\dagger}_p a_p + \frac{1}{2}\omega_p \delta^{3}(0)] \hspace{3mm}$

I thought: $\omega_p$ is a function of p as $\omega^{2}_p = |p|^{2} + m^2$ and so the dirac delta will sift out the value of $\omega_p$ at $p = 0$. Could someone tell me why this statement is incorrect? I think I've made some significant conceptual error. Is the first term divergent for infinite p as well?

P.S. wherever p appears above, it is to be taken as the 3-momentum

Last edited: Aug 24, 2015
2. Aug 24, 2015

### ShayanJ

What you expect would happen if the Dirac delta was $\delta^3(p)$. But $\delta^3(0)$ is simply equal to infinity, or more precisely, the volume of whole space, which is a constant.

3. Aug 24, 2015

### soviet1100

Ah, of course. Thanks, that was silly of me.