Cosmology with unparticles

We discuss cosmological consequences of the existence of physics beyond the standard model that exhibits Banks-Zaks and unparticle behavior in the UV and IR, respectively. We first derive the equation of state for unparticles and use it to obtain the temperature dependence of the corresponding energy and entropy densities. We then formulate the Boltzmann and Kubo equations for both the unparticles and the Banks-Zaks particles, and use these results to determine the equilibrium conditions between the standard model and the new physics. We conclude by obtaining the constraints on the effective number of degrees of freedom of unparticles imposed by big-bang nucleosynthesis.

Figure 1

Regions in the ${\Lambda }_{\mathcal{U}}-M_{\mathcal{U}}$ plane corresponding to various freeze-out and thaw-in scenarios for $d_{\mathcal{U}}=3/2$, 2, 3, and $7/2$. Dark grey: SM-NP decoupling in the unparticle phase only; light grey: no SM-NP decoupling; in the white regions $T_{\mathcal{U}\mathrm{\text{−}}f}<v$ (${\Lambda }_{\mathcal{U}}$, $M_{\mathcal{U}}$ are in TeV units). We assumed $g_{\mathrm{SM}}=g_{\mathcal{B}\mathcal{Z}}=g_{\mathcal{U}}=100$, $g_{\mathrm{SM}}^{\prime }=4$, $g_{\mathcal{B}\mathcal{Z}}^{\prime }=50$, and $g_{\mathcal{U}}^{\prime }=d_{\mathcal{U}}$. For the $\mathcal{B}\mathcal{Z}$ phase: $n_{\mathrm{SM}}=n_{\mathrm{NP}}=2$, $d_{\mathrm{SM}}=2$, and $d_{\mathrm{NP}}=3$, while for the $\mathcal{U}$ phase: $n_{\mathrm{SM}}=2$, $n_{\mathrm{NP}}=2(d_{\mathcal{U}}-1)$, $d_{\mathrm{SM}}=2$, and $d_{\mathrm{NP}}=d_{\mathcal{U}}$.