Non-compact nonlinear sigma models

Abstract

The target space of a nonlinear sigma model is usually required to be positive definite to avoid ghosts. We introduce a unique class of nonlinear sigma models where the target space metric has a Lorentzian signature, thus the associated group being non-compact. We show that the would-be ghost associated with the negative direction is fully projected out by 2 second-class constraints, and there exist stable solutions in this class of models. This result also has important implications for Lorentz--invariant massive gravity: There exist stable nontrivial vacua in massive gravity that are free from any linear vDVZ--discontinuity and a ${\Lambda }_2$ decoupling limit can be defined on these vacua.

5 pages

References in corpus (4)

• Resummation of Massive Gravity
• Cosmic Acceleration and the Helicity-0 Graviton
• Generalized Galileon Duality
• Stability of Massive Gravity Solutions for Holographic Conductivity

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