# QFT newbie-creation of particle and anti-particle

Hi,
I read the following in an online source:
In relativistic settings, momentum and energy are equal so the uncertainty principle, for a particle of mass m which is trapped in a box of size L, becomes delta E>= $\hbar$c/L. If uncertainty exceeds delta E=2mc^2, we get pairs of particles and anti-particles from the vacuum.

What I do not understand is these pairs created out of nothing? Has this got to do with field folding up and making these new pairs around the particle in the box?

## Answers and Replies

Mentor
In relativistic settings, momentum and energy are equal
They are not. Do you mean E=pc for ultrarelativistic particles?

If uncertainty exceeds delta E=2mc^2, we get pairs of particles and anti-particles from the vacuum.
Why should we? The "old" particle cannot just release its energy (what is its state afterwards?), and the new particles could be confined to the potential well, too - so they need even more energy.

In relativistic settings, momentum and energy are equal so the uncertainty principle, for a particle of mass m which is trapped in a box of size L, becomes delta E>= $\hbar$c/L. If uncertainty exceeds delta E=2mc^2, we get pairs of particles and anti-particles from the vacuum.