Direct interaction along light cones at the quantum level

Understand

Here, we point out that interactions with time delay can be described at the quantum level using a multi-time wave function $\psi(x_1,...,x_N)$, i.e., a wave function depending on one spacetime variable $x_i = (t_i,\mathbf{x}_i)$ per particle.

• In particular, such a wave function makes it possible to implement direct interaction along light cones (not mediated by fields), as in the Wheeler-Feynman formulation of electrodynamics.
• Our results are as follows.
• (1) We derive a covariant two-particle integral equation and discuss it in detail.