Photon self-energy in a color superconductor - art. no. 094013

In a color superconductor the diquark condensates break spontaneously both the color and ordinary electromagnetism, leaving a remaining rotated U(1) s ymmetry unbroken. The gauge interactions associated with this rotated symme try may be considered as the in-medium electromagnetism. We compute the in- medium photon self-energy in the presence of diquark condensates at high ba ryonic density and weak coupling. This is done to one-loop order for the ca ses of two and three quark flavors. For vanishing temperature, a detailed d iscussion is given of the low momentum behavior of the photon polarization tensor. A simple physical picture for the propagation of light in color sup erconducting media is obtained. The main new effect is due to the diquark c ondensates, which lead to a strong dielectric constant of the medium. The m agnetic permeability remains unchanged, because the primary condensates hav e vanishing spin and angular momentum. In the two flavor case, an additiona l contribution arises due to gapless quarks and electrons, which is respons ible for Debye screening effects. We also discuss the low energy effective theory for the three flavor case in the presence of electromagnetic interac tions.