Charges in light cones and quenched infrared radiation
Detlev Buchholz, Fabio Ciolli, Giuseppe Ruzzi, Ezio Vasselli
March 04, 2025
The creation of electrically charged states and the resulting electromagnetic
fields are considered in space-time regions in which such experiments can
actually be carried out, namely in future-directed light cones. Under the
simplifying assumption of external charges, charged states are formed from
neutral pairs of opposite charges, with one charge being shifted to light-like
infinity. It thereby escapes observation. Despite the fact that this charge
moves asymptotically at the speed of light, the resulting electromagnetic field
has a well-defined energy operator that is bounded from below. Moreover, due to
the spatiotemporal restrictions, the transverse electromagnetic field (the
radiation) has no infrared singularities in the light cone. They are quenched
and the observed radiation can be described by states in the Fock space of
photons. The longitudinal field between the charges (giving rise to Gauss's
law) disappears for inertial observers in an instant. This is consistent with
the fact that there is no evidence for the existence of longitudinal photons.
The results show that the restrictions of operations and observations to light
cones, which are dictated by the arrow of time, amount to a Lorentz-invariant
infrared cutoff.
Keywords:
none