quantum field theory - Why is $\langle j^\mu j^\nu \rangle$ the vacuum polarization amplitude? - Physics Stack Exchange
Sam Walters ☕️ on Twitter: "In the #hydrogen atom, electronic states 2s and 2p have a difference in microwave energy 1058 MHz, called Lamb shift. This is mostly accounted for due to #
Difference between a point particle and an extended particle | Renaissance Universal