Acausality and Nonunique Evolution in Generalized Teleparallel Gravity

Abstract

We show the existence of physical superluminal modes and acausality in the Brans-Dicke type of extension of teleparallel gravity that includes F(T) gravity and teleparallel dark energy as special cases. We derive the characteristic hypersurface for the extra degrees of freedom in the theory, thereby showing that the time evolution is not unique and closed causal curves can appear. Furthermore, we present a concrete disastrous solution in Bianchi type I spacetime, in which the anisotropy in expansion can be any function of time, and thus anisotropy can emerge suddenly, a simple demonstration that the theory is physically problematic.

Version accepted by PRD (v2): 10 pages

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• f(T) teleparallel gravity and cosmology
• Teleparallel Theories of Gravity: Illuminating a Fully Invariant Approach
• Nonmetricity formulation of general relativity and its scalar-tensor extension
• Covariant formulation of scalar-torsion gravity
• Cosmological applications of $F(T,T_G)$ gravity
• Bounce inflation in $f(T)$ Cosmology: A unified inflaton-quintessence field
• Remnant group of local Lorentz transformations in f(T) theories
• Dynamical systems approach and generic properties of $f(T)$ cosmology
• Dynamical Stability Analysis of Accelerating f(T) Gravity Models
• Causal Structures in Gauss-Bonnet gravity
• Scalar-torsion theories of gravity III: analogue of scalar-tensor gravity and conformal invariants
• Foundational issues in f(T) gravity theory
• Scalar-torsion theories of gravity I: general formalism and conformal transformations
• Model-independent limits and constraints on extended theories of gravity from cosmic reconstruction techniques
• Scalar-torsion theories of gravity II: $L(T,X,Y,\varphi )$ theory
• General relativity as an attractor for scalar-torsion cosmology
• Problems of Massive Gravities
• Remnant Symmetry, Propagation and Evolution in f(T) Gravity
• Higgs inflation and teleparallel gravity
• Thermodynamic properties of modified gravity theories
• Post-Newtonian Approximation of Teleparallel Gravity Coupled with a Scalar Field
• Counting Components in the Lagrange Multiplier Formulation of Teleparallel Theories
• Post-Newtonian limit of generalized scalar-torsion theories of gravity
• Post-Newtonian limit of scalar-torsion theories of gravity as analogue to scalar-curvature theories
• Violation of causality in $f(T)$ gravity
• Inflation with teleparallelism: Can torsion generate primordial fluctuations without local Lorentz symmetry?
• Phase Space description of Nonlocal Teleparallel Gravity
• A geometric view on local Lorentz transformations in teleparallel gravity
• Mimetic f(T) Teleparallel gravity and cosmology
• Degrees of Freedom in modified Teleparallel Gravity
• Cosmological Issues in $F(T)$ Gravity Theory
• Global portraits of nonminimal teleparallel inflation
• More on Bianchi I spacetimes and f(T) gravity