Mondragon, Antonio Richard (2007-05). Lorentz-violating dark matter. Doctoral Dissertation. Thesis uri icon

abstract

  • 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.
  • 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.

publication date

  • May 2007