https://doi.org/10.1140/epjc/s10052-017-4796-7
Regular Article - Theoretical Physics
A new recipe for 
CDM
1
Inter-University Centre for Astronomy and Astrophysics, Pune, India
2
Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi, 110025, India
* e-mail: varun@iucaa.in
Received:
12
May
2016
Accepted:
28
March
2017
Published online:
10
April
2017
It is well known that a canonical scalar field is able to describe either dark matter or dark energy but not both. We demonstrate that a non-canonical scalar field can describe both dark matter and dark energy within a unified setting. We consider the simplest extension of the canonical Lagrangian 
where 
and V is a sufficiently flat potential. In this case the kinetic term in the Lagrangian behaves just like a perfect fluid, whereas the potential term mimicks dark energy. For very large values, 
, the equation of state of the kinetic term drops to zero and the universe expands as if filled with a mixture of dark matter and dark energy. The velocity of sound in this model and the associated gravitational clustering are sensitive to the value of 
. For very large values of the clustering properties of our model resemble those of cold dark matter (CDM). But for smaller values of , gravitational clustering on small scales is suppressed, and our model has properties resembling those of warm dark matter (WDM). Therefore our non-canonical model has an interesting new property: its expansion history resembles CDM, while its clustering properties are akin to those of either cold or warm dark matter.
© The Author(s), 2017
