‘Observational’ Quantum Cosmology

Moniz, Paulo Vargas

doi:10.1007/978-3-642-11570-7_2

Cited by 2 publications

(4 citation statements)

References 30 publications

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“…We observe that for a matter-dominated case, our model yields two disconnected branches. 8 However, for both of the branches, by assuming a 3 0 ψ 0 > 0, the time behavior of the scalar field depends not only on the sign of the c 1 β but also on the signs of c 1 and β. We have shown that for different values of n, dependent on the signs of c 1 and β, the scalar field can whether contracts or expands with the cosmic time.…”

Section: (Effective) Dust Cosmologiesmentioning

confidence: 99%

“…In order to investigate the vacuum solution, from relations (4.8) and (4.9), we find that the only allowed solution is obtained by setting β = 0, such that by employing (3.12), we get γ = ± W/6. Consequently, the solutions (3.14), 8 The pre-big bag cosmology [70] has been inspired by superstring theory. Such a scenario has also been constructed by a class of solutions associated to the low-energy string theory, see, e.g., the Nariai solution associated to the dust fluid in the context of the BD theory [44,71,72], such that for one of them (branch I), the scale factor contracts when t < t i and for the other (branch II) it expands for t > t i .…”

Section: (Effective) Vacuum Cosmologiesmentioning

confidence: 99%

“…Higher-dimensional models of the universe have been widely studied: Kaluza-Klein (KK) theories [4][5][6], tendimensional and eleven-dimensional supergravity [7][8][9] as well as string theories [10,11]. In particular, Kaluza considered a five-dimensional space-time, under the following key assumptions [6], to bring together electromagnetism with general relativity (GR): (i) there is no ordinary matter in the higher dimensional space-time, (ii) geometrical quantities similar to those defined in GR were introduced and (iii) the cylinder condition for the extra coordinate was assumed, which implies that the derivatives with respect to the extra dimension must vanish.…”

Section: Introductionmentioning

confidence: 99%

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Modified Saez–Ballester scalar–tensor theory from 5D space-time

Rasouli

Moniz

2017

Class. Quantum Grav.

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In this paper, we bring together the five-dimensional Saez-Ballester (SB) scalar-tensor theory [1] and the induced-matter-theory (IMT) setting [2], to obtain a modified SB theory (MSBT) in four dimensions. Specifically, by using an intrinsic dimensional reduction procedure into the SB field equations in five-dimensions, a MSBT is obtained onto a hypersurface orthogonal to the extra dimension. This four-dimensional MSBT is shown to bear distinctive new features in contrast to the usual corresponding SB theory as well as to IMT and the Modified Brans-Dicke Theory (MBDT) [3]. In more detail, besides usual induced matter terms retrieved through the IMT, the MSBT scalar field is provided with additional physically distinct (namely, SB induced) terms as well as an intrinsic self-interacting potential (interpreted as consequence of the IMT process and the concrete geometry associated to the extra dimension). Moreover, our MSBT has four sets of field equations, with two sets having no analog in the standard SB scalar-tensor theory. It should be emphasized that the herein appealing solutions can emerge solely from the geometrical reductional process, from presence also of extra dimension(s) and not from any ad-hoc matter either in the bulk or on the hypersurface. Subsequently, we apply the herein MSBT to cosmology and consider an extended spatially flat FLRW geometry in a five-dimensional vacuum space-time. After obtaining the exact solutions in the bulk, we proceed to construct, by means of the MSBT setting, the corresponding dynamic, on the four-dimensional hypersurface. More precisely, we obtain the (SB) components of the induced matter, including the induced scalar potential terms. We retrieve two different classes of solutions. Concerning the first class, we show that the MSBT yields a barotropic equation of state for the induced perfect fluid. We then investigate vacuum, dust, radiation, stiff fluid and false vacuum cosmologies for this scenario and contrast the results with those obtained in the standard SB theory, IMT and BD theory. Regarding the second class solutions, we show that the scale factor behaves similar to a de Sitter (DeS) model. However, in our MSBT setting, this behavior is assisted by non-vanishing induced matter instead, without any a priori cosmological constat. Moreover, for all these solutions, we show that the extra dimension contracts with the cosmic time.

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Section: (Effective) Dust Cosmologiesmentioning

confidence: 99%

Section: (Effective) Vacuum Cosmologiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modified Saez–Ballester scalar–tensor theory from 5D space-time

Rasouli

Moniz

2017

Class. Quantum Grav.

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“…First, we shall make no attempt to be systematic in our presentation of chaos [10,16,32,81,248,256] and decoherence [121,253,275], we shall only pinpoint those aspects of these subjects which have been found to be relevant to quantum cosmology. Most importantly, we shall neither attempt a complete presentation of quantum cosmology itself [35,36,182,270,271] . For the purposes of this review, quantum cosmology means the theory of the Wheeler-DeWitt equation restricted to Friedmann -Robertson -Walker mini super spaces (to be defined below), later enlarged to midi super spaces by including also linearized primordial fluctuations (whereby the former mini super spaces come to be regarded as quantum open systems).…”

Section: Introductionmentioning

confidence: 99%

Chaos, decoherence and quantum cosmology

Calzetta

2012

Class. Quantum Grav.

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In this topical review we discuss the connections between chaos, decoherence and quantum cosmology. We understand chaos as classical chaos in systems with a finite number of degrees of freedom, decoherence as environment induced decoherence and quantum cosmology as the theory of the Wheeler -DeWitt equation or else the consistent history formulation thereof, first in mini super spaces and later through its extension to midi super spaces. The overall conclusion is that consideration of decoherence is necessary (and probably sufficient) to sustain an interpretation of quantum cosmology based on the Wave function of the Universe adopting a Wentzel -Kramers -Brillouin form for large Universes, but a definitive account of the semiclassical transition in classically chaotic cosmological models is not available in the literature yet.Chaos, decoherence and quantum cosmology

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‘Observational’ Quantum Cosmology

Cited by 2 publications

References 30 publications

Modified Saez–Ballester scalar–tensor theory from 5D space-time

Modified Saez–Ballester scalar–tensor theory from 5D space-time

Chaos, decoherence and quantum cosmology

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