• Koyel Ganguly

      Articles written in Pramana – Journal of Physics

    • Chameleon field and the late time acceleration of the Universe

      Narayan Banerjee Sudipta Das Koyel Ganguly

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      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 $a^{−3}$.

    • Spherically symmetric scalar field collapse

      Koyel Ganguly Narayan Banerjee

      More Details Abstract Fulltext PDF

      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.

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