Abstract. A gravitational extension of Dirac's 'extensible model of the electron' is presented. The Dirac bubble, treated as a three-dimensional electrically charged brane, is dynamically embedded within a four-dimensional Z₂-symmetric Reissner–Nordstrom bulk. Crucial to our analysis is the gravitational extension of Dirac's brane variation prescription; its major effect is to induce a novel geometrically originated contribution to the energy–momentum tensor on the brane. In turn, the effective potential which governs the evolution of the bubble exhibits a global minimum, such that the size of the bubble stays finite (Planck scale) even at the limit where the mass approaches zero. This way, without fine-tuning, one avoids the problem so-called 'classical radius of the electron'.

PACS numbers: 11.27.+d, 04.20.Fy, 04.40.Nr

Print publication: Issue 23 (7 December 2009)
Received 6 July 2009, in final form 29 September 2009
Published 6 November 2009