*Harvard* *Condensed Matter Theory Seminars*

**Bosonization approach to mixed-valence quantum impurity models**

- I will review the Kondo and Anderson impurity models and their multi-channel
generalizations, giving a discussion of the different non-perturbative
approaches used to study their non-trivial infrared fixed points. I will
briefly outline the history of the models and point out their relevance for the
modern theory of certain heavy fermion compounds as well as certain types of
quantum dots. The emphasis will be on the case of multi-channel impurities. In
particular, I will give a summarized account of the most recent results for the
multi-channel Anderson model closing with a discussion of the bosonization
approach to this type of models.

Using Abelian bosonization, we have established the correspondence between an extended version of the two-channel Anderson model and a particular type of bi-resonant level model. For certain values of the parameters the new model becomes quadratic. We have calculated in closed form the entropy and impurity occupation as functions of temperature and identified the different physical energy scales of the problem. We have shown how, as the temperature goes to zero, the model approaches a universal line of non-Fermi-liquid fixed points.

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