Chameleon scalar fields in relativistic gravitational backgrounds

Shinji Tsujikawa*, Takashi Tamaki, Reza Tavakol

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)


We study the field profile of a scalar field φ that couples to a matter fluid (dubbed a chameleon field) in the relativistic gravitational background of a spherically symmetric spacetime. Employing a linear expansion in terms of the gravitational potential Φ c at the surface of a compact object with a constant density, we derive the thin-shell field profile both inside and outside the object, as well as the resulting effective coupling with matter, analytically. We also carry out numerical simulations for the class of inverse power-law potentials V(φ) = M 4+nφ -n by employing the information provided by our analytical solutions to set the boundary conditions around the centre of the object and show that thin-shell solutions in fact exist if the gravitational potential Φ c is smaller than 0.3, which marginally covers the case of neutron stars. Thus the chameleon mechanism is present in the relativistic gravitational backgrounds, capable of reducing the effective coupling. Since thin-shell solutions are sensitive to the choice of boundary conditions, our analytic field profile is very helpful to provide appropriate boundary conditions for Φ cO(0.1).

Original languageEnglish
Article number020
JournalJournal of Cosmology and Astroparticle Physics
Issue number5
Publication statusPublished - 2009
Externally publishedYes


  • Dark energy theory
  • Gravity
  • String theory and cosmology

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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