Medium modifications of baryon properties in nuclear matter and hypernuclei

We study the medium modifications of baryon properties in nuclear many-body systems, especially in $\Lambda$ hypernuclei. The nucleon and the $\Lambda$ hyperon are described in the Friedberg-Lee model as nontopological solitons which interact through the self-consistent exchange of scalar and vector mesons. The quark degrees of freedom are explicitly considered in the model, so that the medium effects on baryons could be investigated. It is found that the model can provide reasonable descriptions for nuclear matter, finite nuclei, and $\Lambda$ hypernuclei. The present model predicts a significant increase of the baryon radius in nuclear medium.