Cosmological phase space analysis of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>F</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>X</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:mo mathvariant="bold">−</mml:mo><mml:mi>V</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>ϕ</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>scalar field and bouncing solutions

De-Santiago, Josué; Cervantes-Cota, Jorge L.; Wands, David

doi:10.1103/physrevd.87.023502

Cited by 66 publications

(88 citation statements)

References 49 publications

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“…As a consequence, new variables should be considered instead, such as the BST curvature variable ζ BST [478]: although the "pure" curvature perturbation ζ is no longer conserved in the presence of spatial curvature, the new quantity, which reduces to the former in the limit K → 0, can be conserved on super Hubble scales under specific conditions which do not necessarily hold in a bouncing scenario [324,479]. One can note at this point that in the so-called K−bounce scenario in [479], for instance, the bounce is explicitly performed in a spatially curved universe, the K → 0 limit being assumed regular; it might not necessarily be a valid assumption depending on the specific form of the action [367].…”

Section: Spatial Curvature and Non-gaussianitiesmentioning

confidence: 99%

“…This model, however intrinsically problematic because relying on an unstable negative energy field, may be seen as a precursor of a ghost condensate: the temporary effective violation of the NEC merely permits the bounce to occur, but the negative energy component is otherwise subdominant for most of the universe history. No implementation was suggested in practice (see also [366] for a bounce introduced by K-essence, where the conditions for a regular bounce, as well as anisotropies, were discussed): A more general phase space analysis of models with generalized kinetic terms can be found in [367], where conditions under which a bounce is possible in the NEC violating regime are derived.…”

Section: • Ghost Fieldsmentioning

confidence: 99%

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A critical review of classical bouncing cosmologies

2015

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Given the proliferation of bouncing models in recent years, we gather and critically assess these proposals in a comprehensive review. The PLANCK data shows an unmistakably red, quasi scaleinvariant, purely adiabatic primordial power spectrum and no primary non-Gaussianities. While these observations are consistent with inflationary predictions, bouncing cosmologies aspire to provide an alternative framework to explain them. Such models face many problems, both of the purely theoretical kind, such as the necessity of violating the NEC and instabilities, and at the cosmological application level, as exemplified by the possible presence of shear. We provide a pedagogical introduction to these problems and also assess the fitness of different proposals with respect to the data. For example, many models predict a slightly blue spectrum and must be fine-tuned to generate a red spectral index; as a side effect, large non-Gaussianities often result.We highlight several promising attempts to violate the NEC without introducing dangerous instabilities at the classical and/or quantum level. If primordial gravitational waves are observed, certain bouncing cosmologies, such as the cyclic scenario, are in trouble, while others remain valid. We conclude that, while most bouncing cosmologies are far from providing an alternative to the inflationary paradigm, a handful of interesting proposals have surfaced, which warrant further research. The constraints and lessons learned as laid out in this review might guide future research.

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Section: Spatial Curvature and Non-gaussianitiesmentioning

confidence: 99%

Section: • Ghost Fieldsmentioning

confidence: 99%

A critical review of classical bouncing cosmologies

2015

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“…This includes the canonical choice if one considers f (B) = B − 1. In [37,38] it has been shown that, within general relativity, the most general Lagrangian leading to cosmological scaling solutions with an exponential potential can be written as 2 (29). In addition the dimensionless variables (12) turn out to be of great advantage if a scalar field Lagrangian is assumed as in (29).…”

Section: The Noncanonical Scalar Fieldmentioning

confidence: 99%

“…2 In [37,38] this Lagrangian was writtes as L φ = X f (B), however a simple redefinition of the function f can bring this in the form (29).…”

Section: The Noncanonical Scalar Fieldmentioning

confidence: 99%

“…(6)- (8) as an autonomous system of equations, but can also be generalized in different contexts such as nonminimally coupled scalar fields [20][21][22][23], tachyons [24], Galileons [25], phantom and quintom cosmology [26,27], k-essence [28,29], modified gravity [30], three-form cosmology [31,32] and dark energy models coupled to dark matter [33][34][35].…”

Section: The Canonical Scalar Fieldmentioning

confidence: 99%

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Dynamics of cosmological scalar fields

Tamanini

2014

Phys. Rev. D

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The background dynamical evolution of a universe filled with matter and a cosmological scalar field is analyzed employing dynamical system techniques. After the phenomenology of a canonical scalar field with exponential potential is revised, square and square root kinetic corrections to the scalar field canonical Lagrangian are considered and the resulting dynamics at cosmological distances is obtained and studied. These noncanonical cosmological models imply new interesting phenomenology including early time matter dominated solutions, cosmological scaling solutions and late time phantom dominated solutions with dynamical crossing of the phantom barrier. Stability and viability issues for these scalar fields are presented and discussed.

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Form Invariance of Raychaudhuri Equation in the Presence of Inflaton‐Type Fields

Panda,

Gangopadhyay,

Manna

2024

Fortschritte der Physik

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We show that the Raychaudhuri equation (RE) remains form invariant for certain solutions of scalar fields whose Lagrangian is non‐canonical and of the form , with and the potential. Solutions exist for both homogeneous and inhomogeneous fields that are like inflatons. Certain recent observations indicate that the cosmos is inhomogeneous and thus their results are in sync with latest observations. So the RE can accommodate primordial inhomogeneities as well as cosmologically relevant scenarios.

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Cosmological phase space analysis of theF(X)−V(ϕ)scalar field and bouncing solutions

Cited by 66 publications

References 49 publications

A critical review of classical bouncing cosmologies

A critical review of classical bouncing cosmologies

Dynamics of cosmological scalar fields

Form Invariance of Raychaudhuri Equation in the Presence of Inflaton‐Type Fields

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