  We describe a technique for using simulated tensor perturbations in order to
place upper limits on the intensity of magnetic fields in the early universe.
As an example, we apply this technique to the beginning of primordial
nucleosynthesis. We determined that any magnetic seed fields that existed
before that time were still in the process of being amplified. In the future,
we plan to apply this technique to a wider range of initial magnetic fields and
cosmological epochs.
