  We study the interaction of electrons in graphene with the quantized
electromagnetic field in the presence of an applied uniform electric field
using the Dirac model of graphene. Electronic states are represented by exact
solutions of the Dirac equation in the electric background, and amplitudes of
first-order Feynman diagrams describing the interaction with the photon field
are calculated for massive Dirac particles in both valleys. Photon emission
probabilities from a single electron and from a many-electron system at the
charge neutrality point are derived, including the angular and frequency
dependence, and several limiting cases are analyzed. The pattern of photon
emission at the Dirac point in a strong field is determined by an interplay
between the nonperturbative creation of electron-hole pairs and spontaneous
emission, allowing for the possibility of observing the Schwinger effect in
measurements of the radiation emitted by pristine graphene under DC voltage.
