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Homework Help: Complex scalar field - Feynman integral

  1. Dec 6, 2011 #1
    1. The problem statement, all variables and given/known data

    For a real scalar field [itex]\phi[/itex], the propagator is [itex]\frac{i}{(k^2-m_\phi^2)}[/itex].

    If we instead assume a complex scalar field, [itex]\phi = \frac{1}{\sqrt{2}} (\phi_1 + i \phi_2)[/itex], where [itex]\phi_1,\phi_2[/itex] are real fields with masses [itex]m_{\phi 1},m_{\phi 2}[/itex], what is the propagator?

    2. Relevant equations


    3. The attempt at a solution

    Is this true?: There's a 1/2 probability that the propagator has mass [itex]\phi_1[/itex], [itex]\phi_2[/itex] so the propagator should just be [itex]\frac{1}{2} [ \frac{i}{(k^2-m_{\phi_1}^2)} + \frac{i}{(k^2-m_{\phi_2}^2)} ][/itex]. But how does the 'i' change things?

    Any help would be appreciated,

  2. jcsd
  3. Dec 6, 2011 #2


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    Science Advisor
    Homework Helper

    The Euler-Lagrange eqns (which typically determine the Feynman propagator) are completeley separated and identical with the original KG equation. So indeed the propagator will be written as a sum b/w a term with i and the other with i2.
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