@article{BaumgaertelLledo2004,
  author    = {Baumg{\"a}rtel, Hellmut and Lledo, Fernando},
  title     = {Duality of compact groups and Hilbert C*-systems for C*-algebras with a nontrivial center},
  issn      = {0129-167X},
  year      = {2004},
  abstract  = {In this paper we present duality theory for compact groups in the case when the C*-algebra A, the fixed point algebra of the corresponding Hilbert C*-system (F, 9), has a nontrivial center Z superset of C1 and the relative commutant satisfies the minimality condition A' boolean AND F = Z, as well as a technical condition called regularity. The abstract characterization of the mentioned Hilbert C*-system is expressed by means of an inclusion of C*- categories T-c < T, where T-c is a suitable DR-category and T a full subcategory of the category of endomorphisms of A. Both categories have the same objects and the arrows of T can be generated from the arrows of T-c and the center Z. A crucial new element that appears in the present analysis is an abelian group C(G), which we call the chain group of G, and that can be constructed from certain equivalence relation defined on (G) over cap, the dual object of G. The chain group, which is isomorphic to the character group of the center of g, determines the action of irreducible endomorphisms of A when restricted to Z. Moreover, C(g) encodes the possibility of defining a symmetry epsilon also for the larger category T of the previous inclusion},
  language  = {en}
}
@article{Lledo2002,
  author    = {Lled{\´o}, Fernando},
  title     = {Dual group actions on C*-algebras and their description by Hilbert extensions},
  year      = {2002},
  language  = {en}
}
@article{BaumgaertelJurkeLledo2002,
  author    = {Baumg{\"a}rtel, Hellmut and Jurke, Matthias and Lled{\´o}, Fernando},
  title     = {Twisted duality for the CAR-algebra},
  year      = {2002},
  language  = {en}
}
@article{Lledo1997,
  author    = {Lled{\´o}, Fernando},
  title     = {A family of examples with quantum constraints},
  year      = {1997},
  language  = {en}
}
@book{BaumgaertelJurkeLledo1995,
  author    = {Baumg{\"a}rtel, Hellmut and Jurke, Matthias and Lled{\´o}, Fernando},
  title     = {Symmetrie und Quantentheorie},
  series = {Preprint / Universit{\"a}t Potsdam, Institut f{\"u}r Mathematik},
  volume    = {1995, 6},
  journal   = {Preprint / Universit{\"a}t Potsdam, Institut f{\"u}r Mathematik},
  publisher = {Univ.},
  address   = {Potsdam},
  year      = {1995},
  language  = {de}
}
@article{BaumgaertelJurkeLledo1995,
  author    = {Baumg{\"a}rtel, Hellmut and Jurke, Matthias and Lled{\´o}, Fernando},
  title     = {On free nets over Minkowski space},
  year      = {1995},
  language  = {en}
}
@phdthesis{Lledo1998,
  author    = {Lled{\´o}, Fernando},
  title     = {Algebraic properties of massless free nets},
  address   = {Potsdam},
  pages     = {101 S.},
  year      = {1998},
  language  = {en}
}
@book{BaumgaertelJurkeLledo1994,
  author    = {Baumg{\"a}rtel, Hellmut and Jurke, Matthias and Lled{\´o}, Fernando},
  title     = {A remark on covariant and causal nets of CAR-resp.CCR-type local algebras assigned to the irreducible unitary representation of the poincare group labeled by (m>0, s, +)},
  series = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  volume    = {120},
  journal   = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  address   = {Berlin},
  year      = {1994},
  language  = {en}
}
@book{BaumgaertelJurkeLledo1994,
  author    = {Baumg{\"a}rtel, Hellmut and Jurke, Matthias and Lled{\´o}, Fernando},
  title     = {Mathematische Strukturen passen auf die Natur : Reflexionen {\"u}ber das Wechselverh{\"a}ltnis von Mathematik und Physik},
  series = {Preprint / Universit{\"a}t Potsdam, Institut f{\"u}r Mathematik},
  volume    = {1994, 18},
  journal   = {Preprint / Universit{\"a}t Potsdam, Institut f{\"u}r Mathematik},
  publisher = {Univ.},
  address   = {Potsdam},
  year      = {1994},
  language  = {de}
}
@article{BaumgaertelLledo1997,
  author    = {Baumg{\"a}rtel, Hellmut and Lled{\´o}, Fernando},
  title     = {Some results on superselection structures for C*-algebras with nontrivial center},
  isbn      = {981-02-3984-X},
  year      = {1997},
  language  = {en}
}
@article{BaumgaertelLledo1997,
  author    = {Baumg{\"a}rtel, Hellmut and Lled{\´o}, Fernando},
  title     = {Superselection structures for C*-algebras with nontrivial center},
  year      = {1997},
  language  = {en}
}
@book{Lledo1996,
  author    = {Lled{\´o}, Fernando},
  title     = {A family of examples with quantum constraints},
  series = {Preprint / Universit{\"a}t Potsdam, Institut f{\"u}r Mathematik},
  volume    = {1996, 01},
  journal   = {Preprint / Universit{\"a}t Potsdam, Institut f{\"u}r Mathematik},
  publisher = {Univ.},
  address   = {Potsdam},
  pages     = {10 S.},
  year      = {1996},
  language  = {en}
}
@book{BaumgaertelLledo2000,
  author    = {Baumg{\"a}rtel, Hellmut and Lled{\´o}, Fernando},
  title     = {Dual group actions on C*-algebras and their description by Hilbert extensions},
  series = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  volume    = {445},
  journal   = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  publisher = {Techn. Univ.},
  address   = {Berlin},
  pages     = {14 S.},
  year      = {2000},
  language  = {en}
}
@book{BaumgaertelJurkeLledo1999,
  author    = {Baumg{\"a}rtel, Hellmut and Jurke, Matthias and Lled{\´o}, Fernando},
  title     = {Twisted duality for the CAR-algebra},
  series = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  volume    = {401},
  journal   = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  publisher = {Techn. Univ.},
  address   = {Berlin},
  year      = {1999},
  language  = {en}
}
@book{GrundlingLledo1999,
  author    = {Grundling, H. and Lled{\´o}, Fernando},
  title     = {Local quantum constraints},
  series = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  volume    = {402},
  journal   = {Preprint / SFB 288, Differentialgeometrie und Quantenphysik},
  address   = {Berlin},
  year      = {1999},
  language  = {en}
}
@misc{Lledo1999,
  author    = {Lled{\´o}, Fernando},
  title     = {Contributions to operator theory in spaces with an indefinite metric, the Heinz Langer anniversary volume, A. S. Dijksma ... eds.; Basel [u.a.], Birkh{\"a}user, 1998, ISBN 3-7643-6003-8},
  year      = {1999},
  language  = {en}
}