Kinetically Driven Quintessence
Takeshi Chiba, Takahiro Okabe, Masahide Yamaguchi
TL;DR
This work demonstrates that a scalar field with non-canonical, purely kinetic terms can drive cosmic acceleration as quintessence ($-1<w_Q<0$) or even phantom energy ($w<-1$) without a potential term. By constructing a kinetic Lagrangian $p(\phi,X)=f(\phi)(-X+X^2)$ and analyzing its scaling solutions, the authors show a constant EOS arises with a constant $X$, and that the corresponding attractor solutions are robust to a wide range of initial conditions. They extend the framework to phantom behavior using a generalized $p(\phi,X)=f(\phi)g(X)$ with an eighth-degree $g$, obtaining stable phantom scaling solutions and detailing their phase-space structure. The paper also discusses mass-scale implications, and outlines a reconstruction scheme to infer the underlying $p(\phi,X)$ from observational data via the distance–redshift relation. Overall, kinetic-only dark energy models offer a viable alternative to potential-driven quintessence, with attractor dynamics and potential observational tests through cosmological reconstructions.
Abstract
Recently, a novel class of models for inflation has been found in which the inflationary dynamics is driven solely by (non-canonical) kinetic terms rather than by potential terms. As an obvious extension, we show that a scalar field with non-canonical kinetic terms alone behaves like an energy component which is time-varying and has negative pressure presently, i.e. quintessence. We present a model which has a constant equation of state, that is, a ``kinetic'' counterpart of the Ratra-Peebles model of a quintessence field with a potential term. We make clear the structure of the phase plane and show that the quintessential solution is a late-time attractor. We also give a model for the ``phantom'' component which has an equation of state with $w=p/ρ<-1$.