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Jörg Jäckel

University of Heidelberg, Germany
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Spontaneous Symmetry Breaking by the
Condensation of Composites of Fermions

In this seminar I want to address some problems of partial bosonization
in systems with strongly
interacting fermions. Why is Mean Field Theory very deeply affected by
ambiguities in the choice
of the mean fields? After finding that these ambiguities are due to an
insufficient approximation I will show
how they can be removed in the context of the renormalization group.
This leads to the concept of scale dependent degrees of freedom.
Moreover, I would like to briefly discuss the 2PI bosonic effective
action as an alternative method. As an
application of this I investigate if a six fermion instanton interaction
can generate color octet condensates in the vacuum.

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