TY - GEN

T1 - Unparticles: Interpretation and Cosmology.

AU - McDonald, John

PY - 2008

Y1 - 2008

N2 - We discuss the physical interpretation of unparticles and review the constraintsfrom cosmology. Unparticles may be understood in terms of confinedstates of a strongly-coupled scale-invariant theory, where scale-invariance implies that the confined states have continuous masses. This picture is consistentwith the observation that unparticle operators can be represented in terms ofcontinuous mass fields. Finite results in scattering processes are obtained bycompensating the infinite number of unparticle final states with an infinitesimalcoupling per unparticle. As a result, unparticles are stable with respect todecay or annihilation to Standard Model particles, implying a one-way flow ofenergy from the Standard Model sector to the unparticle sector. The qualitativeproperties of unparticles, which result from their continuous mass nature, areunchanged in the case where scale-invariance is broken by a mass gap. Unparticles with a mass gap can evade constraints from astrophysical and 5th force considerations, in which case cosmology provides the strongest constraints.

AB - We discuss the physical interpretation of unparticles and review the constraintsfrom cosmology. Unparticles may be understood in terms of confinedstates of a strongly-coupled scale-invariant theory, where scale-invariance implies that the confined states have continuous masses. This picture is consistentwith the observation that unparticle operators can be represented in terms ofcontinuous mass fields. Finite results in scattering processes are obtained bycompensating the infinite number of unparticle final states with an infinitesimalcoupling per unparticle. As a result, unparticles are stable with respect todecay or annihilation to Standard Model particles, implying a one-way flow ofenergy from the Standard Model sector to the unparticle sector. The qualitativeproperties of unparticles, which result from their continuous mass nature, areunchanged in the case where scale-invariance is broken by a mass gap. Unparticles with a mass gap can evade constraints from astrophysical and 5th force considerations, in which case cosmology provides the strongest constraints.

M3 - Other contribution

ER -