부산대학교 도서관

Summary: ``$SU(2)$ gauge fields and axions can have a stable, isotropicand homogeneous configuration during inflation. However, couplings toother matter species lead to particle production, which in turn inducesbackreaction on and destabilization of the non-Abelian and axionbackground. In this paper, we first study the particle production by a$SU(2)$ gauge field coupled to a massive Dirac doublet. To carry outthis calculation we have made two technical improvements compared towhat has been done in the literature. First, we apply theantisymmetrization of the operators to treat particles andantiparticles on equal footing; second, to deal with the UVdivergences, we apply instantaneous subtraction. We find that thebackreaction of produced fermions on the $SU(2)$ background isnegligible for model parameters of observational interest. Next, weconsider production of fermions due to coupling to the axion. Thetree-level backreaction on the gauge fields, as well as on the axion,is vanishingly small. We also provide an estimate for the loopeffects.''