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A modification to general relativity by use of the notion of local expansion of space-time

Hodgkinson, TF A modification to general relativity by use of the notion of local expansion of space-time , PhD thesis, University of Salford.

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General Relativity (GR) is Einsteins' theory of gravity whereby the motions of bodies are explained due to their following geodesic paths (the shortest distance between two points) in a curved four dimensional space-time. The curvature being attributed to the presence of mass As such there is no explicit force present in this theory, contrary to Newtons' law of gravity. However in the limit of GR (where the field is both weak and static and bodies are travelling with velocities slow compared to that of light), then Newtons' law is recovered in the approximation. GR has explained all gravitational phenomena extremely well (eg solar system), that is until one considers the measured motions of galaxies. The galaxies are rotating too quickly to be consistent with GR/ Newton. An explanation for this discrepancy has originally been suggested, concerning the presence of extra mass, of as yet an unknown nature. However, to date not a hint of this `Dark Matter' has been detected. A second explanation is that of Modified Newtonian Dynamics (MOND), whereby at a certain very small acceleration, the actual gravitational physics deviates from that described by Newton. The MOND proposal seems to fit extremely well with observations without the need to invoke the presence of DM. The main problem with the MOND concept is that it does not fit in with the standard GR. ii The following work details an exploration into the novel assumption that the presence of mass is not only responsible for the curvature of space-time but also for a local expansion of space-time. By introducing an expansion factor at the very beginning of standard GR analysis, one �nds an extra term appears which is consistent throughout. With the inclusion of this extra term, one can, in the weak, static and slow velocity limit, �nd a direct link to the MOND phenomenology. It is found that the extra term is negligible for small systems (eg Solar) yet it is the dominant term for large systems (eg galaxies). The work is published in Physical Review D. `Gravitational Theoretical Development Supporting MOND'.

Item Type: Thesis (PhD)
Schools: Schools > School of Computing, Science and Engineering
Depositing User: S Rafiq
Date Deposited: 10 Sep 2015 11:12
Last Modified: 05 Apr 2016 18:20

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