The Quintom scenario (derived from the words quintessence and phantom, as in phantom energy) is a hypothetical model of dark energy.
In this scenario, the equation of state [math]\displaystyle{ p = w\rho }[/math] of the dark energy, relating its pressure and energy density, can cross the boundary [math]\displaystyle{ w = -1 }[/math] associated with the cosmological constant. The boundary separates the phantom-energy-like behavior with [math]\displaystyle{ w \lt -1 }[/math] from the quintessence-like behavior with [math]\displaystyle{ w \gt -1 }[/math]. A no-go theorem shows that this behavior requires at least two degrees of freedom for dark energy models involving ideal gases or scalar fields.[1]
The Quintom scenario was applied in 2008 to produce a model of inflationary cosmology with a Big Bounce instead of a Big Bang singularity.[2]
fr:Énergie fantôme it:Energia fantasma