Noncompact nonlinear sigma models
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 noncompact. We show that the wouldbe ghost associated with the negative direction is fully projected out by 2 secondclass 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 vDVZdiscontinuity and a decoupling limit can be defined on these vacua.
 Authors:

^{[1]};
^{[1]};
^{[1]}
 Case Western Reserve Univ., Cleveland, OH (United States). CERCA, Department of Physics
 Publication Date:
 Grant/Contract Number:
 SC0009946; SC0010600
 Type:
 Published Article
 Journal Name:
 Physics Letters. Section B
 Additional Journal Information:
 Journal Volume: 760; Journal ID: ISSN 03702693
 Publisher:
 Elsevier
 Research Org:
 Case Western Reserve Univ., Cleveland, OH (United States)
 Sponsoring Org:
 USDOE
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
 OSTI Identifier:
 1353492
 Alternate Identifier(s):
 OSTI ID: 1434606
de Rham, Claudia, Tolley, Andrew J., and Zhou, ShuangYong. Noncompact nonlinear sigma models. United States: N. p.,
Web. doi:10.1016/j.physletb.2016.07.035.
de Rham, Claudia, Tolley, Andrew J., & Zhou, ShuangYong. Noncompact nonlinear sigma models. United States. doi:10.1016/j.physletb.2016.07.035.
de Rham, Claudia, Tolley, Andrew J., and Zhou, ShuangYong. 2016.
"Noncompact nonlinear sigma models". United States.
doi:10.1016/j.physletb.2016.07.035.
@article{osti_1353492,
title = {Noncompact nonlinear sigma models},
author = {de Rham, Claudia and Tolley, Andrew J. and Zhou, ShuangYong},
abstractNote = {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 noncompact. We show that the wouldbe ghost associated with the negative direction is fully projected out by 2 secondclass 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 vDVZdiscontinuity and a decoupling limit can be defined on these vacua.},
doi = {10.1016/j.physletb.2016.07.035},
journal = {Physics Letters. Section B},
number = ,
volume = 760,
place = {United States},
year = {2016},
month = {7}
}