  We study the resonance interaction between two uniformly accelerated
identical atoms, one excited and the other in the ground state, prepared in a
correlated (symmetric or antisymmetric) state and interacting with the scalar
field or the electromagnetic field in the vacuum state. In this case (resonance
interaction), the interatomic interaction is a second-order effect in the
atom-field coupling. We separate the contributions of vacuum fluctuations and
radiation reaction to the resonance energy shift of the system, and show that
only radiation reaction contributes, while Unruh thermal fluctuations do not
affect the resonance interaction. We also find that beyond a characteristic
length scale related to the atomic acceleration, non-thermal effects in the
radiation reaction contribution change the distance-dependence of the resonance
interaction. Finally, we find that previously unidentified features appear,
compared with the scalar field case, when the interaction with the
electromagnetic field is considered, as a consequence of the peculiar nature of
the vacuum quantum noise of the electromagnetic field in a relativistically
accelerated background.
