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Description:
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Observations from the 1930s until the present have established the existence of
dark matter with an abundance that is much larger than that of luminous matter .
Because none of the known particles of nature have the correct properties to be
identified as the dark matter , various exotic candidates have been proposed . The
neutralino of supersymmetric theories is the most promising example . Such cold dark
matter candidates , however , lead to a conflict between the standard simulations of
the evolution of cosmic structure and observations . Simulations predict excessive
structure formation on small scales , including density cusps at the centers of galaxies ,
that is not observed . This conflict still persists in early 2007 , and it has not
yet been convincingly resolved by attempted explanations that invoke astrophysical
phenomena , which would destroy or broaden all small scale structure . We have
investigated another candidate that is perhaps more exotic : Lorentz -violating dark
matter , which was originally motivated by an unconventional fundamental theory , but
which in this dissertation is defined as matter which has a nonzero minimum velocity .
Furthermore , the present investigation evolved into the broader goal of exploring
the properties of Lorentz -violating matter and the astrophysical consequences – a
subject which to our knowledge has not been previously studied . Our preliminary
investigations indicated that this form of matter might have less tendency to form
small -scale structure . These preliminary calculations certainly established that Lorentz -violating matter which always moves at an appreciable fraction of the speed
of light will bind less strongly . However , the much more thorough set of studies
reported here lead to the conclusion that , although the binding energy is reduced ,
the small -scale structure problem is not solved by Lorentz -violating dark matter . On
the other hand , when we compare the predictions of Lorentz -violating dynamics with
those of classical special relativity and general relativity , we find that differences might
be observable in the orbital motions of galaxies in a cluster . For example , galaxies –
which are composed almost entirely of dark matter – observed to have enlarged orbits
about the cluster center of mass may be an indication of Lorentz violation . |