PREPRINT

# Implications of Some Static Spherically Symmetric Graviton-Dilaton Solutions in Brans-Dicke and Low Energy String Theory

S. Kalyana Rama
arXiv:hep-th/9505151

Submitted on 24 May 1995

## Abstract

Analysing the static, spherically symmetric graviton-dilaton solutions in low energy string and Brans-Dicke theory, we find the following. For a charge neutral point star, these theories cannot predict non trivial PPN parameters, $\beta$ and $\gamma$, without introducing naked singularities. We then couple a cosmological constant $\mathrm{\Lambda }$ as in low energy string theory. We find that only in low energy string theory, a non zero $\mathrm{\Lambda }$ leads to a curvature singularity, which is much worse than a naked singularity. Requiring its absence upto a distance ${r}_{\ast }$ implies a bound $|\mathrm{\Lambda }|<{10}^{-102}\left(\frac{{r}_{\ast }}{\mathrm{p}\mathrm{c}}{\right)}^{-2}$ in natural units. If ${r}_{\ast }\simeq 1\mathrm{M}\mathrm{p}\mathrm{c}$ then $|\mathrm{\Lambda }|<{10}^{-114}$ and, if ${r}_{\ast }\simeq {10}^{28}\mathrm{c}\mathrm{m}$ then $|\mathrm{\Lambda }|<{10}^{-122}$ in natural units.

## Preprint

Comment: 11 pages. Latex File. Invited Talk presented at the XI DAE Symposium held during 21 - 28 December 1994 in Shantiniketan, India

Subjects: High Energy Physics - Theory; Astrophysics; General Relativity and Quantum Cosmology