A discussion on the most general torsion-gravity with electrodynamics for Dirac spinor matter fields

Fabbri, Luca

doi:10.1142/s0219887815500991

Cited by 34 publications

(50 citation statements)

References 19 publications

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“…In Ref. [35], Fabbri analyses the stability of the most general quadratic gravitational action with torsion and Dirac fields by demanding, in addition, a consistent decoupling between curvature and torsion that preserves continuity in the torsionless limit, concluding that the only non-vanishing component of the torsion is given by the pseudo-vector mode and that parity-violating terms are not allowed in the Lagrangian density. Nevertheless, due to some lack of clarity in the existing literature, a deeper analysis of the origins of these differences is not available yet.…”

Section: Stability In Minkowski Spacetimementioning

confidence: 99%

Stability in quadratic torsion theories

et al. 2017

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We revisit the definition and some of the characteristics of quadratic theories of gravity with torsion. We start from a Lagrangian density quadratic in the curvature and torsion tensors. By assuming that General Relativity should be recovered when the torsion vanishes and investigating the behaviour of the vector and pseudo-vector torsion fields in the weak-gravity regime, we present a set of necessary conditions for the stability of these theories. Moreover, we explicitly obtain the gravitational field equations using the Palatini variational principle with the metricity condition implemented via a Lagrange multiplier.

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Section: Stability In Minkowski Spacetimementioning

confidence: 99%

Stability in quadratic torsion theories

et al. 2017

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“…For the dynamics, we assume the action given by (22) in which (∂W ) µν is the curl of W µ being the torsion axial vector with R Ricci scalar and F µν Faraday tensor, and where X is the strength of the interaction between torsion and the spin of spinor fields while M and m are the mass of torsion and the spinor field itself. Having defined the connection in the torsionless case it would seem we went in a case of restricted generality, but in reality we are still in the most general situation even if the connection has no torsion so long as torsion is eventually included in the form of a supplementary massive axial vector field [16].…”

Section: Geometry Of the Spinor Fieldsmentioning

confidence: 99%

Torsion axial vector and Yvon-Takabayashi angle: zitterbewegung, chirality and all that

Fabbri

Rocha

2018

Eur. Phys. J. C

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We consider propagating torsion as a completion of gravitation in order to describe the dynamics of curvedtwisted space-times filled with Dirac spinorial fields; we discuss interesting relationships of the torsion axial vector and the curvature tensor with the Yvon-Takabayashi angle and the module of the spinor field, that is the two degrees of freedom of the spinor field itself: in particular, we shall discuss in what way the torsion axial vector could be seen as the potential of a specific interaction of the Yvon-Takabayashi angle, and therefore as a force between the two chiral projections of the spinor field itself. Chiral interactions of the components of a spinor may render effects of zitterbewegung, as well as effective mass terms and other related features: we shall briefly sketch some of the analogies and differences with the similar but not identical situation given by the Yukawa interaction occurring in the Higgs sector of the standard model. We will provide some overall considerations about general consequences for contemporary physics, consequences that have never been discussed before, so far as we are aware, in the present physics literature.

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“…g µν = −κ 2 g αβ ∂ α φ∂ β φ g µν , where κ denotes the Planck length scale, and the scalar 'mimetic field' φ is assumed dimensionless [21]. Such a parametrization not only ensures the invariance of g µν under a conformal demonstrates Cartan gauge invariance [157], the square-torsion theory [158][159][160][161], the degenerate tetrad formalism [162][163][164][165][166], the non-minimal metric-scalar-torsion coupling formalism [167][168][169], and so on. Moreover, a lot of attention has been drawn in recent years by modified versions of the (curvature-free) teleparallel gravity theories [170][171][172][173][174][175][176][177][178][179][180][181][182][183][184][185], apart from the modern refinements of Poincaré gauge theory of gravity [186][187][188][189][190][191][192][193][194][195][196].…”

Section: Introductionmentioning

confidence: 99%

Cosmological dark sector from a mimetic–metric–torsion perspective

Chothe

Dutta

Sur

2019

Int. J. Mod. Phys. D

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We generalize the basic theory of mimetic gravity by extending its purview to the general metriccompatible geometries that admit torsion, in addition to curvature. This essentially implies reinstating the mimetic principle of isolating the conformal degree of freedom of gravity in presence of torsion, by parametrizing both the physical metric and torsion in terms of the scalar 'mimetic' field and the metric and torsion of a fiducial space. We assert the requisite torsion parametrization from an inspection of the fiducial space Cartan transformation which, together with the conformal transformation of the fiducial metric, preserve the physical metric and torsion. In formulating the scalar-tensor equivalent Lagrangian, we consider an explicit contact coupling of the mimetic field with torsion, so that the former can manifest itself geometrically as the source of a torsion mode, and most importantly, give rise to a viable 'dark universe' picture from a mimicry of an evolving dust-like cosmological fluid with a non-zero pressure. A further consideration of higher derivatives of the mimetic field in the Lagrangian leads to physical bounds on the mimetic-torsion coupling strength, which we determine explicitly. * transformation of g µν , but also implicates that φ is left non-dynamical by the condition for the invertibility of g µν , viz. −κ 2 g µν ∂ µ φ∂ ν φ = 1 . This condition could be implemented in the theory as a constraint, using a Lagrange multiplier λ in an equivalent mimetic action. A further equivalence of the latter with the singular Brans-Dicke (BD) action (in which the BD parameter w = − 3 2 ) eventually shows that mimetic gravity is indeed a ratification of GR being raised to the status of a scalar-tensor equivalent MG theory [21][22][23][24]29].Detailed studies have revealed many attractive features of the basic mimetic model of Chemseddine and Mukhanov (henceforth, the CM model [21]) and its various extensions, from the perspectives of both cosmology and astrophysics . In particular, the CM Lagrangian extended by a potential V (φ) leads to the scenarios of a cosmologically evolving fluid -the so-called 'mimetic fluid' -which characterizes dust, albeit with a nonvanishing pressure 1 [22]. As such, no propagating scalar perturbation mode is there to suppress the growth of structures at smaller (sub-galactic) scales [26,27]. Nor it is possible to define the quantum fluctuations to the (non-dynamical) field φ, so that the latter can provide the seeds of the observed large scale structure of the universe [22,23]. A reasonable supposition has therefore been to extend the CM theory further by incorporating higher derivative (HD) term(s) for φ, e.g. (✷φ) 2 , which lead(s) to a non-vanishing sound speed c s of the mimetic matter perturbations, keeping the background solution unaffected qualitatively 2 [22,23,29]. However, the HD terms in general make the theory susceptible to Ostrogradsky ghost or(and) gradient instabilities [26,27,[64][65][66][67], possible wayouts of which point to more complicated extensions...

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A discussion on the most general torsion-gravity with electrodynamics for Dirac spinor matter fields

Cited by 34 publications

References 19 publications

Stability in quadratic torsion theories

Stability in quadratic torsion theories

Torsion axial vector and Yvon-Takabayashi angle: zitterbewegung, chirality and all that

Cosmological dark sector from a mimetic–metric–torsion perspective

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