AMA | October 2024

12388.474 - 12410.305 Sean Carroll

And if you just start throwing fields around and you don't work very hard, you will end up with a quantum field theory that allows you to have particles with negative energies. And that means that your vacuum state is not stable. If you have one particle that has a negative energy, you can get an arbitrarily large negative energy just by creating a lot of those particles, right?