Koyel Ganguly
Articles written in Pramana – Journal of Physics
Volume 74 Issue 3 March 2010 pp L481-L489 Rapid Communication
Chameleon field and the late time acceleration of the Universe
Narayan Banerjee Sudipta Das Koyel Ganguly
In the present work, it is shown that a chameleon scalar field having a non-minimal coupling with dark matter can give rise to a smooth transition from a decelerated to an accelerated phase of expansion for the Universe. It is surprising to note that the coupling with the chameleon scalar field hardly affects the evolution of the dark matter sector, which still redshifts as $a^{−3}$.
Volume 80 Issue 3 March 2013 pp 439-448 Research Articles
Spherically symmetric scalar field collapse
Koyel Ganguly Narayan Banerjee
It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for $(𝜌 + 3p) < 0$. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons formed before the formation of singularity. The singularities formed are shell focussing in nature. The density of the scalar field distribution is seen to diverge at singularity. The Ricci scalar also diverges at the singularity. The interior spherically symmetric metric is matched with exterior Vaidya metric at the hypersurface and the appropriate junction conditions are obtained.
Volume 96, 2022
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