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Homework Help: Redshift question

  1. Jan 15, 2009 #1
    1. The problem statement, all variables and given/known data
    The question:
    Explain why pair creation is expected to occur in the early universe, and estimate the redshift at which proton-antiproton pairs are created.

    2. Relevant equations

    3. The attempt at a solution
    My logic for the reason is that the process requires high energy gamma photons to create the proton-antiproton pair. As for the second part, I don't really have a clue, although this is my guess:

    For the process to occur, u need a photon to have around [itex]2m_p c^2[/itex] of energy, so:
    [tex] 2m_pc^2 = \frac{hc}{\lambda_e} [/itex]
    where the mass is the rest mass of the proton and the lambda is the wavelength of the original photon which made the pair.

    [tex] 1+Z = \frac{\delta \lambda}{\lambda_e} [/tex]
    [tex] Z = \frac{2 \delta \lambda m_p c}{h} - 1 [/tex]

    But I don't have any values, so where am I suppose to go from here?
  2. jcsd
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