  This work is motivated by the long-standing question about the internal
stability of the electron. While one cannot investigate internal properties of
a point-like particle, it is fair to analyze the response of the Dirac sea to
an electron. For this purpose the concept of an exchange hole is generalized
from the Fermi sea of condensed matter physics to the Dirac sea of quantum
electrodynamics. In order to conserve charge and angular momentum, an exchange
electron is added to the exchange hole, forming a neutral exchange exciton.
Consequently, the pair correlation defining the exchange hole is generalized to
a three-fermion correlation. An approximation by sequential pair correlations
provides analytic results for charge densities, average distances, and force
densities of the exchange hole and electron. The analysis is supported by
analogies to the negative ion of positronium.
