Does a Kalb--Ramond field make spacetime optically active?
Department of Physics and Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721 302, India
2 The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600 113, India
3 Department of Physics, Jadavpur University, Calcutta 700 032, India
4 St. Edmunds College, University of Cambridge, Cambridge CB3 0BN, UK
Published online: 25 January 2002
A spacetime with torsion produced by a Kalb--Ramond field coupled gravitationally to the Maxwell field, in accordance with a recent proposal by two of us (PM and SS), is argued to lead to optical activity in synchrotron radiation from cosmologically distant radio sources. We show that this indicates a very small, but possibly observable rotation of the plane of polarization of the radiation, above and beyond the Faraday rotation due to magnetized galactic plasma. Implications for heterotic string theory are outlined.
© Società Italiana di Fisica, Springer-Verlag, 2002