Unparticle dark energy

TL;DR

This paper explores a dark energy model where unparticles act as quintessence, analyzing its evolution, constraints from observational data, and theoretical advantages over traditional scalar field models.

Contribution

It introduces a novel unparticle-based dark energy model with detailed parameter analysis and observational constraints, highlighting its theoretical robustness.

Findings

Model not ruled out by current data

Unparticles are protected from radiative corrections

Coupling to standard model can be arbitrarily suppressed

Abstract

We examine a dark energy model where a scalar unparticle degree of freedom plays the role of quintessence. In particular, we study a model where the unparticle degree of freedom has a standard kinetic term and a simple mass potential, the evolution is slowly rolling and the field value is of the order of the unparticle energy scale ($\lambda_u$). We study how the evolution of $w$ depends on the parameters $B$ (a function of the unparticle scaling dimension $d_u$), the initial value of the field $\phi_i$ (or equivalently, $\lambda_u$) and the present matter density $\Omega_{m0}$. We use observational data from Type Ia supernovae, BAO and CMB to constrain the model parameters and find that these models are not ruled out by the observational data. From a theoretical point of view, an unparticle dark energy model is very attractive, since unparticles (being bound states of fundamental fermions) are protected from radiative corrections. Further, coupling of unparticles to the standard model fields can be arbitrarily suppressed by raising the fundamental energy scale $M_F$, making the unparticle dark energy model free of most of the problems that plague conventional scalar field quintessence models.