Tachyon inflation in teleparallel gravity

Akbarieh, Amin Rezaei; Izadi, Yousef

doi:10.1140/epjc/s10052-019-6819-z

Cited by 27 publications

(4 citation statements)

References 47 publications

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“…In [538], a powerlaw model of f (T) gravity was probed for its possible inflationary scenarios where the spectral index and power spectrum is again calculated but where the model was not totally related to possible late-time accelerated expansion, for consistency. Finally, [539] explores possible tachyonic inflationary scenarios which has some interesting explanations for recent observational measurements. [Jackson: In this section a number of prominent modified theories within TG have been explored through the works that appear in the literature in the cosmological setting at background level.…”

Section: Higgs Inflationmentioning

confidence: 99%

Teleparallel gravity: from theory to cosmology

et al. 2023

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Teleparallel gravity has significantly increased in popularity in recent decades, bringing attention to Einstein’s other theory of gravity. In this Review, we give a comprehensive introduction to how teleparallel geometry is developed as a gauge theory of translations together with all the other properties of gauge field theory. We also related this form of geometry to the broader metric-affine approach to forming gravitational theories where we describe a systematic way of constructing consistent teleparallel theories that respect certain physical conditions such as local Lorentz invariance. We first use teleparallel gravity to formulate a teleparallel equivalent of general relativity which is dynamically equivalent to general relativity but which may have different behaviors for other scenarios, such as quantum gravity. After setting this foundation, we describe the plethora of modified teleparallel theories of gravity that have been proposed in the literature. We attempt to connect them together into general classes of covariant gravitational theories. Of particular interest, we highlight the recent proposal of a teleparallel analogue of Horndeski gravity which offers the possibility of reviving all of the regular Horndeski contributions. In the second part of the Review, we first survey works in teleparallel astrophysics literature where we focus on the open questions in this regime of physics. We then discuss the cosmological consequences for the various formulations of teleparallel gravity. We do this at background level by exploring works using various approaches ranging from dynamical systems to Noether symmetries, and more. Naturally, we then discuss perturbation theory, firstly by giving a concise approach in which this can be applied in teleparallel gravity theories and then apply it to a number of important theories in the literature. Finally, we examine works in observational and precision cosmology across the plethora of proposal theories. This is done using some of the latest observations and is used to tackle cosmological tensions which may be alleviated in teleparallel cosmology. We also introduce a number of recent works in the application of machine learning to gravity, we do this through deep learning and Gaussian processes, together with discussions about other approaches in the literature.

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Section: Higgs Inflationmentioning

confidence: 99%

Teleparallel gravity: from theory to cosmology

et al. 2023

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“…Direct coupling of a scalar field to the torsion scalar [51, and inflation in teleparallel gravity [48,49,51,90,109,117, have been studied in a number of papers. It has always been assumed that non-metricity vanishes, which in the tetrad formalism is known as the tetrad postulate.…”

Section: Higgs Inflationmentioning

confidence: 99%

Higgs inflation and teleparallel gravity

Raatikainen

Räsänen

2019

J. Cosmol. Astropart. Phys.

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Teleparallel gravity is a formulation of general relativity that is physically equivalent to metric gravity if the gravitational action has the Einstein-Hilbert form and matter is minimally coupled. However, scalar fields generally couple directly to the connection, breaking the equivalence. In particular, this happens for the Standard Model Higgs. We show that a teleparallel theory with a non-minimally coupled scalar field has no linear scalar perturbations, and therefore cannot give successful inflation, unless the non-minimal coupling functions satisfy a particular relation. If the relation is satisfied, Higgs inflation can give an arbitrarily large tensor-to-scalar ratio r. Our results also apply to f (T ) theories, as they are scalar-tensor theories written in different field coordinates. We discuss generalisation to more complicated actions.

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“…As the impetus and implications from fundamental physics to the reasonable form of nonminimal coupling to torsion are still unclear, alternatives to the usual quadratic coupling may be well explored. Of course, there are also proposals for more general scalar-torsion theories including an additional coupling to vector torsion or the boundary term [22,51,84,85], modification of the kinetic term [86], analogue of Horndeski gravity [87], and even more general frameworks [58,63,88]. The current method of investigation should be suitable for those as well.…”

Section: Discussionmentioning

confidence: 99%

Global Portraits of Nonminimal Teleparallel Inflation

Järv

Lember

2021

Universe

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We construct global phase portraits of inflationary dynamics in teleparallel gravity models with a scalar field nonminimally coupled to torsion scalar. The adopted set of variables can clearly distinguish between different asymptotic states as fixed points, including the kinetic and inflationary regimes. The key role in the description of inflation is played by the heteroclinic orbits that run from the asymptotic saddle points to the late time attractor point and are approximated by nonminimal slow roll conditions. To seek the asymptotic fixed points, we outline a heuristic method in terms of the “effective potential” and “effective mass”, which can be applied for any nonminimally coupled theories. As particular examples, we study positive quadratic nonminimal couplings with quadratic and quartic potentials and note how the portraits differ qualitatively from the known scalar-curvature counterparts. For quadratic models, inflation can only occur at small nonminimal coupling to torsion, as for larger coupling, the asymptotic de Sitter saddle point disappears from the physical phase space. Teleparallel models with quartic potentials are not viable for inflation at all, since for small nonminimal coupling, the asymptotic saddle point exhibits weaker than exponential expansion, and for larger coupling, it also disappears.

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Tachyon inflation in teleparallel gravity

Cited by 27 publications

References 47 publications

Teleparallel gravity: from theory to cosmology

Teleparallel gravity: from theory to cosmology

Higgs inflation and teleparallel gravity

Global Portraits of Nonminimal Teleparallel Inflation

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