An electron that does not move in space would be represented by  a solid arrow pointing straight up. Photons are usually  represented by dotted arrows, while particles that move backwards  in time wou
An electron that does not move in space would be represented by  a solid arrow pointing straight up. Photons are usually  represented by dotted arrows, while particles that move backwards  in time would be represented by downward-pointing arrows. FTP, name  this mathematical tool useful for analyzing elementary reactions in  quantum electrodynamics, named for a Nobel Prize-winning American  physicist.
An electron that does not move in space would be represented by  a solid arrow pointing straight up.
{Feynman} diagram