String corrections to the Sagnac effect

In an effort to investigate string effects in physical observations, we have analyzed the rotating Kerr-Sen metric in a Sagnac type experiment and have deduced exact expressions for the delay. For an Earth bound configuration, it turns out that a correction to the basic Sagnac delay by an order of similar to10(-14) s leads to a terrestrial dilatonic charge of amount similar to10(24) esu, a value nearly 200 times larger than the electronic charge of the Earth's magnetosphere. (C) 2002 Elsevier Science B.V. All rights reserved.