The linearized 3+1 TEGR system has imaginary eigenvalues in its principal symbol but becomes strongly hyperbolic after gauge fixing isolated problematic sectors.
Introducing Cadabra: a symbolic computer algebra system for field theory problems
4 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Cadabra is a new computer algebra system designed specifically for the solution of problems encountered in field theory. It has extensive functionality for tensor polynomial simplification taking care of Bianchi and Schouten identities, for fermions and anti-commuting variables, Clifford algebras and Fierz transformations, implicit coordinate dependence, multiple index types and many other field theory related concepts. The input format is a subset of TeX and thus easy to learn. Both a command-line and a graphical interface are available. The present paper is an introduction to the program using several concrete problems from gravity, supergravity and quantum field theory.
fields
gr-qc 4representative citing papers
Pure R^2 gravity propagates three degrees of freedom nonlinearly but zero linearly around Minkowski and other traceless-Ricci R=0 spacetimes due to ten second-class constraints becoming first-class upon linearization.
Primary constraint analysis of Newer General Relativity recovers five tensor and three vector constraints and identifies a previously unreported scalar-sector degeneracy that produces one or two constraints depending on the c_i values.
Derives background-hierarchy bounds for scalar, transverse-vector and tensor modes in Type 3 NGR around flat FLRW, identifying viable parameter regions where linear perturbation theory remains consistent.
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Spectrum of pure $R^2$ gravity: full Hamiltonian analysis
Pure R^2 gravity propagates three degrees of freedom nonlinearly but zero linearly around Minkowski and other traceless-Ricci R=0 spacetimes due to ten second-class constraints becoming first-class upon linearization.