All about the static fermion bags in the Gross-Neveu model

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We review in detail the construction of all stable static fermion bags in the (1 + 1)-dimensional Gross-Neveu model with N flavors of Dirac fermions, in the large-N limit. In addition to the well known kink and topologically trivial solitons (which correspond, respectively, to the spinor and antisymmetric tensor representations of O(2N)), there are also threshold bound states of a kink and a topologically trivial soliton: the heavier topological solitons (HTS). The mass of any of these newly discovered HTS's is the sum of masses of its solitonic constituents and it corresponds to the tensor product of their O(2N) representations. Thus, it is marginally stable (at least in the large-N limit). Furthermore, its mass is independent of the distance between the centers of its constituents, which serves as a flat collective coordinate, or a modulus. There are no additional stable static solitons in the Gross-Neveu model. We provide detailed derivation of the profiles, masses, and fermion number contents of these static solitons. For pedagogical clarity, and in order for this paper to be self-contained, we also included detailed appendices on supersymmetric quantum mechanics and on reflectionless potentials in one spatial dimension, which are intimately related with the theory of static fermion bags. In particular, we present a novel simple explicit formula for the diagonal resolvent of a reflectionless Schrödinger operator with an arbitrary number of bound states. In additional appendices we summarize the relevant group representation theoretic facts and also provide a simple calculation of the mass of the kinks.

Original languageEnglish
Pages (from-to)166-231
Number of pages66
JournalAnnals of Physics
Issue number1
StatePublished - Jan 2004

Bibliographical note

Funding Information:
I thank Yitzhak Frishman, Marek Karliner, Yael Shadmi, and Raphy Yuster for reading some parts of this review. I am indebted to Yael Shadmi for making useful comments concerning Appendix D and to Raphy Yuster for providing the alternative proof in Appendix F . This research has been supported in part by the Israeli Science Foundation.


  • Bag model
  • Gross-Neveu
  • Inverse scattering
  • Large N
  • Solitons

ASJC Scopus subject areas

  • General Physics and Astronomy


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