Eur. Phys. J. C (2012) 72: 1913
https://doi.org/10.1140/epjc/s10052-012-1913-5

Regular Article - Theoretical Physics

Particle scattering by a test fluid on a Schwarzschild spacetime: the equation of state matters

¹ CNR, Istituto per le Applicazioni del Calcolo “M. Picone”, 00185, Rome, Italy
² ICRA, University of Rome “La Sapienza”, 00185, Rome, Italy
³ Physics Department, University of Rome “La Sapienza”, 00185, Rome, Italy

^* e-mail: binid@icra.it

Received: 21 January 2012
Published online: 7 March 2012

Abstract

The motion of a massive test particle in a Schwarzschild spacetime surrounded by a perfect fluid with equation of state p ₀=wρ ₀ is investigated. Deviations from geodesic motion are analyzed as a function of the parameter w, ranging from w=1, which corresponds to the case of massive free scalar fields, down into the so-called “phantom” energy, with w<−1. It is found that the interaction with the fluid leads to capture (escape) of the particle trajectory in the case 1+w>0 (<0), respectively. Based on this result, it is argued that inspection of the trajectories of test particles in the vicinity of a Schwarzschild black hole with matter around may offer a new means of gaining insights into the nature of cosmic matter.