Violation of The Equivalence Principle in Scalar-Tensor Theories of Gravity

Andrias Fajarudin

Diploma on HEP, Abdus Salam ICTP


In this thesis I study the violation of the equivalence principle induced by two screening mechanisms in scalar-tensor theories of gravity : the chameleon mechanism and the Vainshtein effect. In the chameleon mechanism, the scalar field acquires a mass which depends on the environment density such that it will be screened in a high density environments. I discuss the violation of the equivalence principle both in Einstein and in Jordan frames. In Einstein frame, unscreened objects will move with bigger acceleration compared to screened objects. In Jordan frame, only unscreened objects feel the chameleon field whereas screened objects donít. Consequently, only unscreened objects move on geodesics. This leads to order unity violation of the equivalence principle. In the Vainshtein mechanism, the screening of the scalar field comes from derivative interaction that become large in the vicinity of massive objects. Perturbations of scalar in such regions acquire a large kinetic term and therefore decouple from matter. Thus, the scalar screens itself and become invisible to experiments. Vainshtein mechanism doesnít lead to order unity violation of the equivalence principle. In this screening mechanism, equivalence principle violation occurs at a much reduced level.

fisik@net (ISSN 2086-5325)

Publikasi : Tesis S2 (2010)
Tanggal masuk / revisi : 8 September 2010 / 8 September 2010
Naskah lengkap : format PDF (1.013.284 byte)
Kontak : Andrias Fajarudin
Keterangan : fisika teoritik
40 halaman
bahasa Inggris