Quintessence with tachyonic resonance and late-time cosmic-microwave-background and gravitational-wave signals

TL;DR

This paper explores a quintessence dark energy model with tachyonic resonance, analyzing its late-time cosmological signals such as gravitational waves and CMB variations through numerical simulations and discussing their observational prospects.

Contribution

It introduces a novel quintessence model with abrupt oscillations and tachyonic instability, linking particle production to observable late-time cosmological signals.

Findings

Tachyonic resonance leads to significant gravitational-wave background.

Density perturbations are enhanced by particle production.

Model predictions are testable with current and future cosmological observations.

Abstract

Combinations of recent cosmological observations, including Dark Energy Spectroscopic Instrument (DESI), show hints of a dynamical nature for dark energy. While the data suggest the possibility of the phantom crossing, it is worth thoroughly exploring quintessence models. Given that phenomenological parametrisations of the equation-of-state parameter $w(a)$ with a sharp transitional feature fit the data well, we study the realisation of such models in quintessence. In the late Universe, the quintessence field begins to oscillate abruptly, changing the behaviour of $w$. Naturally, such a model entails tachyonic instability, and particle production modifies $w$. We perform numerical lattice simulations to study the time dependence of $w$. In addition, the violent particle production produces significant density perturbations and the stochastic gravitational-wave background, whose characteristic scale depends on the mass scale of the quintessence around the minimum of the potential. We discuss the observability of these late-time cosmological signals through cosmic microwave background, quasar astrometry, pulsar timing arrays, and other observational probes.