The Quintom scenario was proposed in 2004 by Xin-Min Zhang et al., and is a hypothetical model of
dark energy
In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
. The name of 'quintom' was derived from 'quintessence' from
quintessence field and 'phantom' from
phantom dark energy
In cosmology, phantom dark energy is a hypothetical form of dark energy. It possesses negative kinetic energy, and predicts expansion of the universe in excess of that predicted by a cosmological constant, which leads to a Big Rip. The idea of pha ...
. The Quintom scenario was to fit the evolution of dark energy with the cosmological data.
Equation of state
In this scenario, the
equation of state
In physics and chemistry, an equation of state is a thermodynamic equation relating state variables, which describe the state of matter under a given set of physical conditions, such as pressure, volume, temperature, or internal energy. Most mo ...
(EoS)
of the dark energy, relating its
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...
and
energy density
In physics, energy density is the quotient between the amount of energy stored in a given system or contained in a given region of space and the volume of the system or region considered. Often only the ''useful'' or extractable energy is measure ...
, can cross the boundary
associated with the cosmological constant. The boundary separates the phantom-energy-like behavior with
from the quintessence-like behavior with
.
According to a no-go theorem, a single-field, single-fluid scalar model cannot cross
. Achieving such a crossing requires at least two degrees of freedom in dark energy models built from ideal fluids or scalar fields. To allow the effective equation of state to cross
, possible approaches include:
* Multiple fields & extra degrees of freedom, e.g. additional scalar fields or fermion fields;
* Higher-order derivative terms, e.g. Galileon theory;
* Modified gravities, e.g.
,
,
gravity,
metric-affine theory, or
Horndeski gravity;
* Matter-dark energy interactions, e.g. interacting
dark sector
''Dark Sector'', stylized as ''darkSector'', is a 2008 third-person shooter video game developed by Digital Extremes for the Xbox 360, PlayStation 3 and Microsoft Windows.
The game is set in the fictional Eastern Bloc country of Lasria, and ce ...
;
* Extra dimension effects, e.g.
DGP gravity.
The Quintom scenario was applied in 2008 to produce a model of
inflationary cosmology
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe. Following the inflationary period, the universe continued to expand, but at a slower r ...
with a
Big Bounce
The Big Bounce hypothesis is a cosmological model for the origin of the known universe. It was originally suggested as a phase of the ''cyclic model'' or ''oscillatory universe'' interpretation of the Big Bang, where the first cosmological event ...
instead of a
Big Bang
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...
singularity.
Observational evidence
Current cosmological observations have given a clue in favor of the Quintom scenario. Since 2024, DESI has released the first year data and provided a possible "Quintom-B" scenario, with the equation of state crossing the boundary from below to above. The DESI data release 2 shows a deviation from the ΛCDM model compared with dynamical dark energy, preferring a Quintom-B behavior crossing
from below to above.
References
External links
*
*
*
*
* Cai, Yi-Fu; Qiu, Taotao; Xia, Jun-Qing; Li, Hong; Zhang, Xinmin (2009). "Model of inflationary cosmology without singularity". ''Physical Review D''. 79 (2): 021303.
doi:
10.1103/PhysRevD.79.021303.
Dark energy
{{physical-cosmology-stub
fr:Énergie fantôme
it:Energia fantasma