General relativity with spin and torsion: Foundations and prospects

Hehl, Friedrich W.; Heyde, Paul von der; Kerlick, G. David; Nester, James M.

doi:10.1103/revmodphys.48.393

Cited by 2,471 publications

(2,717 citation statements)

References 93 publications

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“…1 1 The affine connection determines not only the curving but also the twirling of the spacetime. The latter is encoded in the torsion tensor [2,4], and it is discarded from the analysis here by considering a symmetric connection Γ λ αβ = Γ λ βα only. Open access under CC BY license.…”

Section: Metric Vs Palatini Formulations: Generalitiesmentioning

confidence: 99%

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Inflation with non-minimal coupling: Metric vs. Palatini formulations

2008

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We analyze non-minimally coupled scalar field theories in metric (second-order) and Palatini (first-order) formalisms in a comparative fashion. After contrasting them in a general setup, we specialize to inflation and find that the two formalisms differ in their predictions for various cosmological parameters. The main reason is that dependencies on the non-minimal coupling parameter are different in the two formalisms. For successful inflation, the Palatini approach prefers a much larger value for the non-minimal coupling parameter than the Metric approach. Unlike the Metric formalism, in Palatini, the inflaton stays well below the Planck scale whereby providing a natural inflationary epoch.

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Section: Metric Vs Palatini Formulations: Generalitiesmentioning

confidence: 99%

“…terms quadratic in the torsion [2,4]. In this work, following this observation, fermion contributions to the affinity Γ will be discarded.…”

Section: Metric Vs Palatini Formulations: Generalitiesmentioning

confidence: 99%

Inflation with non-minimal coupling: Metric vs. Palatini formulations

2008

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“…It can be shown [25,26] that the field strength H µνρ plays a rôle analogous to a totally antisymmetric torsion [27,28], entering through a generalised Christoffel connection Γ ρ µν Γ ρ νµ :…”

Section: Lorentz and Cpt Violating Geometries (With Torsion) In The Strmentioning

confidence: 99%

Proceedings of the 12th International Conference on Low Energy Antiproton Physics (LEAP2016)

Hiyama¹,

Kanai²,

Ulmer

et al. 2017

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I review briefly string-inspired models of the Early Universe in which the Robertson-Walker geometry is extended to involve appropriate torsion fields that are constant in the frame of a cosmological observer. Fermion fields in such geometries are described by Lagrangians that fall in the simplest Lorentz-and CPT-violating extensions of the Standard Model (SME), in which the fermions couple to a constant axial vector background b µ γ 5 , with the b µ "axion-like" field associated to torsion. In the talk I also review mechanisms to suppress the torsion in the current era, compatible with the existing stringent upper bounds, which are of relevance to searches for CPT violation of interest to this conference. KEYWORDS:Early Universe, Torsion, Strings, Standard Model Extension, CPT Violation Theoretical motivations for Lorentz and CPT ViolationBaryogenesis/Leptogenesis, that is processes in the early Universe that lead to the observed matter-antimatter asymmetry in the Cosmos, represent a long-standing unresolved issue in cosmology [1]. Many approaches to the problem proposed in the literature [2] but no consensus has emerged on the potential mechanisms. Many of them predict lepton number violation, and in particular some of them entail [3] a µ → e − γ interaction with predictions on the corresponding branching ratio which may be falsified at the next generation experiments, but others are more difficult to falsify.A standard measure of the abundance of baryons over that of antibaryons is defined by the ratiowhere n B is the number density of baryons, nB is the number density of antibaryons and n γ is the density of photons (proportional to the entropy density s). This number was determined with accurate measurements of the CMB radiation by the experiments WMAP [5] and Planck [6]. However, there is no experimental evidence for primordial antimatter in the visible universe. Similarly, the generation of an asymmetry between leptons and antileptons is known as leptogenesis. This is expected to be of the same order of magnitude as Y ∆B . If B, the net baryon number, is conserved in Nature, the matter asymmetry can only originate from an asymmetric initial condition B 0. However, such an asymmetry would rapidly diminish during inflation, and extreme fine tuning of the initial condition would become necessary. This is highly unsatisfactory from a theoretical point of view. Consequently a mechanism for the dynamical generation of a baryon asymmetry is required. In the seminal paper [7], Sakharov identified three sufficient conditions that must be satisfied in order to produce a net baryon number.(1) The theory must allow for interactions that violate B conservation. These interactions must become effective at high energy scales in order to guarantee the stability of the proton. (2) Both discrete symmetries C (charge conjugation) and CP (where P denotes parity) are violated.In fact C violation is not enough, as correlations between the spins of particles and antiparticles 1

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“…which implies that the augmented KR field strength 3-tensor acts as the source of torsion [12]. The resulting action, which has direct correspondence with heterotic string theory, is then given by…”

Section: General Formalismmentioning

confidence: 99%

Does curvature–dilaton coupling with a Kalb–Ramond field lead to an accelerating Universe?

SenGupta

Sur

2003

J. Cosmol. Astropart. Phys.

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In this work we show that the Universe evolving in a spacetime with torsion (originated from a second rank antisymmetric Kalb-Ramond field) and dilaton is free from any big bang singularity and can have acceleration during the evolution. Both the matter and radiation dominated era have been considered and the role of the dilaton to explain the decelerating phase in the earlier epoch has also been discussed.

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General relativity with spin and torsion: Foundations and prospects

Cited by 2,471 publications

References 93 publications

Inflation with non-minimal coupling: Metric vs. Palatini formulations

Inflation with non-minimal coupling: Metric vs. Palatini formulations

Proceedings of the 12th International Conference on Low Energy Antiproton Physics (LEAP2016)

Does curvature–dilaton coupling with a Kalb–Ramond field lead to an accelerating Universe?

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