23 research outputs found
Antisymmetric tensor Z_p gauge symmetries in field theory and string theory
We consider discrete gauge symmetries in D dimensions arising as remnants of
broken continuous gauge symmetries carried by general antisymmetric tensor
fields, rather than by standard 1-forms. The lagrangian for such a general
gauge theory can be described in terms of a -form gauge field
made massive by a -form, or other dual realizations, that we also
discuss. The theory contains charged topological defects of different
dimensionalities, generalizing the familiar charged particles and strings in
D=4. We describe realizations in string theory compactifications with torsion
cycles, or with background field strength fluxes. We also provide examples of
non-abelian discrete groups, for which the group elements are associated with
charged objects of different dimensionality.Comment: 16 pages; v2: references added and typos fixe
Non-Abelian discrete gauge symmetries in 4d string models
We study the realization of non-Abelian discrete gauge symmetries in 4d field
theory and string theory compactifications. The underlying structure
generalizes the Abelian case, and follows from the interplay between gaugings
of non-Abelian isometries of the scalar manifold and field identifications
making axion-like fields periodic. We present several classes of string
constructions realizing non-Abelian discrete gauge symmetries. In particular,
compactifications with torsion homology classes, where non-Abelianity arises
microscopically from the Hanany-Witten effect, or compactifications with
non-Abelian discrete isometry groups, like twisted tori. We finally focus on
the more interesting case of magnetized branes in toroidal compactifications
and quotients thereof (and their heterotic and intersecting duals), in which
the non-Abelian discrete gauge symmetries imply powerful selection rules for
Yukawa couplings of charged matter fields. In particular, in MSSM-like models
they correspond to discrete flavour symmetries constraining the quark and
lepton mass matrices, as we show in specific examples.Comment: 58 pages; minor typos corrected and references adde