Non-singular Brans–Dicke collapse in deformed phase space

Rasouli, S. M. M.; Ziaie, Amir Hadi; Jalalzadeh, S.; Moniz, Paulo Vargas

doi:10.1016/j.aop.2016.09.007

Cited by 19 publications

(16 citation statements)

References 161 publications

(105 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For θ 0, solving the complicated differential equation (23) analytically is impossible. However, it is feasible to derive the general conditions under which the universe can accelerate.…”

Section: Kinetic Inflation and The Horizon Problemmentioning

confidence: 99%

“…From ( 28), we observe that the acceleration/deceleration condition of the scale factor completely depends on the evolution of the scalar field, which, in turn, is obtained from a nonlinear differential equation (23). Note that to obtain ä a for the commutative case, θ must be set equal to zero in both ( 23) and (28).…”

Section: Kinetic Inflation and The Horizon Problemmentioning

confidence: 99%

“…In this regard, Snyder's formulation [1,2] for a NC setting of spacetime coordinates is of significant interest. It introduces a short length cutoff (that is called the NC parameter) which can modify the renormalizability properties of relativistic quantum field theory (see [3,4] and references therein for a thorough review; cf., e.g., [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24] for several specific explorations.) At the scales where quantum gravity effects would be important, NC effects could therefore be relevant 1 .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Inflationary universe in deformed phase space scenario

et al. 2018

Self Cite

View full text Add to dashboard Cite

We consider a noncommutative (NC) inflationary model with a homogeneous scalar field minimally coupled to gravity. The particular NC inflationary setting herein proposed, produces entirely new consequences as summarized in what follows. We first analyze the free field case and subsequently examine the situation where the scalar field is subjected to a polynomial and exponential potentials. We propose to use a canonical deformation between momenta, in a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe, and while the Friedmann equation (Hamiltonian constraint) remains unaffected the Friedmann acceleration equation (and thus the Klein-Gordon equation) is modified by an extra term linear in the NC parameter. This concrete noncommutativity on the momenta allows interesting dynamics that other NC models seem not to allow. Let us be more precise. This extra term behaves as the sole explicit pressure that under the right circumstances implies a period of accelerated expansion of the universe. We find that in the absence of the scalar field potential, and in contrast with the commutative case, in which the scale factor always decelerates, we obtain an inflationary phase for small negative values of the NC parameter. Subsequently, the period of accelerated expansion is smoothly replaced by an appropriate deceleration phase providing an interesting model regarding the graceful exit problem in inflationary models. This last property is present either in the free field case or under the influence of the scalar field potentials considered here. Moreover, in the case of the free scalar field, we show that not only the horizon problem is solved but also there is some resemblance between the evolution equation of the scale factor associated to our model and that for the R 2 (Starobinsky) inflationary model. Therefore, our herein NC model not only can be taken as an appropriate scenario to get a successful kinetic inflation, but also is a convenient setting to obtain inflationary universe possessing the graceful exit when scalar field potentials are present.

show abstract

“…For θ 0, solving the complicated differential equation (23) analytically is impossible. However, it is feasible to derive the general conditions under which the universe can accelerate.…”

Section: Kinetic Inflation and The Horizon Problemmentioning

confidence: 99%

Section: Kinetic Inflation and The Horizon Problemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Inflationary universe in deformed phase space scenario

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…In this paper, we have introduced a NC BD setting. Such a scenario bears much resemblance to the settings assumed in NC quantum cosmology or a few classical noncommutative gravitational/cosmological investigations in theories alternative to general relativity [12][13][14][15]).…”

Section: Discussionmentioning

confidence: 86%

Gravity-Driven Acceleration and Kinetic Inflation in Noncommutative Brans-Dicke Setting

Rasouli

Moniz

2016

OAP

Self Cite

View full text Add to dashboard Cite

By assuming the spatially flat FLRW line-element and employing the Hamiltonian formalism, a noncommutative (NC) setting of the Brans-Dicke (BD) theory is introduced. We investigate gravitydriven acceleration and kinetic inflation in this NC BD cosmology. Despite to the commutative case, in which both the scale factor and BD scalar field are obtained in power-law forms (in terms of the cosmic time), in our herein NC model, we see that the power-law scalar factor is multiplied by a dynamical exponential warp factor. This warp factor depends on not only the noncommutative parameter but also the momentum conjugate associated to the BD scalar field. For very small values of this parameter, we obtain an appropriate inflationary solution, which can overcome problems within standard BD cosmology in a more efficient manner. Moreover, we see that a graceful exit from an early acceleration epoch towards a decelerating radiation epoch is provided. For late times, due to the presence of the NC parameter, we obtain a zero acceleration epoch, which can be interpreted as the coarse-grained explanation.

show abstract

“…It has been demonstrated that the singularity can be removed by including quantum effects [29, 28]. coarse grained effects at late times of the evolution of the universe. Recently, various NC cosmological/gravitational frameworks have been constructed to investigate different shortcomings associated to the corresponding standard models [35,40,36,39,38,37]. For instance, in [24], two of us have shown that such source can be borrowed from the NC portions accompanying the standard BD setting.…”

Section: Introductionmentioning

confidence: 99%

Kinetic inflation in deformed phase space Brans–Dicke cosmology

Rasouli

Marto

Moniz

2019

Physics of the Dark Universe

Self Cite

View full text Add to dashboard Cite

In this paper, by establishing a Brans-Dicke (BD) cosmology by means of a deformed phase space, in the absence of any scalar potential, cosmological constant and ordinary matter, we show that it is feasible to overcome obstacles reported in the corresponding commutative (nondeformed) frameworks. More concretely, by applying the Hamiltonian formalism and introducing a dynamical deformation, between the momenta associated to the FLRW scale factor and the BD scalar field, we obtain the modified equations of motion. In particular, these equations reduce to their standard counterparts when the noncommutative (NC) parameter is switched off. By focusing on a specific branch of solutions, in contrast to standard frameworks (even with a varying BD coupling parameter), we show that we can obtain an adequate appropriate inflationary epoch possessing a suitable graceful exit. In other words, in the Jordan frame (JF), such branch of solutions properly satisfy the sufficient condition required for satisfactory inflation, which is equivalent to get an inflationary phase in the conformal Einstein frame (EF) without branch change. Concerning the cosmological dynamics, we further show that our NC framework bears close resemblance to the R 2 (Starobinsky) inflationary model. 1 Recently, concerning such an ad hoc scalar potential in scalar tensor theories, it has been shown that the geometry of the higher dimensions can instead naturally yield it; see, for instance, [9,10,11,12]. Moreover, we should note that, in addition to including a scalar potential, there are also other approaches for describing the present day acceleration (which, in turn, suffer from major problems [13]): (i) When the BD coupling parameter is restricted to −2 ≤ ω ≤ −3/2; in this case, the energy condition associated to the BD scalar field is not satisfied. In this paper, to avoid encountering such a problem, we always assume −3/2 < ω. (ii) Assuming a varying BD coupling parameter [14]. (iii) Assuming that the scalar fields can interact with ordinary matter, which are called chameleon fields [15]. (iv) By starting from the BD theory in five or higher dimensional space-times, see for instance, [16]. We should emphasize that the motivation of

show abstract

Non-singular Brans–Dicke collapse in deformed phase space

Cited by 19 publications

References 161 publications

Inflationary universe in deformed phase space scenario

Inflationary universe in deformed phase space scenario

Gravity-Driven Acceleration and Kinetic Inflation in Noncommutative Brans-Dicke Setting

Kinetic inflation in deformed phase space Brans–Dicke cosmology

Contact Info

Product

Resources

About