Cosmological Evolution in a Type-0 String Theory

Diamandis, G.A.; Georgalas, B.C.; Mavromatos, Nikolaos; Papantonopoulos, Eleftherios; Pappa, Ioanna

doi:10.1142/s0217751x02010534

Cited by 36 publications

(101 citation statements)

References 28 publications

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“…This important and by far not complete issue is highly model dependent, and it relies on specific properties of the underlying microscopic string theory, involving detailed scenaria of compactification, moduli field stabilization etc. In the literatute there are toy brane-inspired, non-critical-string cosmological models, where such approximately constant dilatons during early epochs of the Universe could be realised explicitly [13,14,25]. We also remark that similar assumptions are made in generic dilaton quintessence scenaria of critical strings [27].…”

Section: Modified Boltzmann Equation In Non-critical Stringsmentioning

confidence: 76%

“…through an appropriate minimisation of its potential, being thus stabilised at early times. In such on-shell situations, as opposed to our non-equilibrium (off-shell) model studied in this and in previous articles [1,25,26], matter particles may…”

Section: Modified Boltzmann Equation In Non-critical Stringsmentioning

confidence: 88%

“…In (2.24) we have taken into account that in the class of models of [1,25], we are concentrating in this work, = 0. Thus the Boltzmann equation finally becomes It is important to recall once more that, upon Liouville dressing, which restores the conformal invariance of the model, the graviton and dilaton Weyl anomaly coefficients satisfy (2.9), which upon the identification of the Liouville mode with (a function of the cosmic) time yield (2.11).…”

Section: The Final Form Of the Liouville Operation (220) Then Readsmentioning

confidence: 99%

“…For instance, in the absence of matter, in the specific (but generic enough) non-critical string model of [25], we have that the present-era dilaton and scale factor of the Universe are such that…”

Section: D X G Ementioning

confidence: 99%

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Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances

2007

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In this work we derive the modifications to the Boltzmann equation governing the cosmic evolution of relic abundances induced by dilaton dissipative-source and non-critical-string terms in dilaton-driven non-equilibrium string Cosmologies. We also discuss briefly the most important phenomenological consequences, including modifications of the constraints on the available parameter space of cosmologically appealing particle physics models, imposed by recent precision data of astrophysical measurements.

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Section: Modified Boltzmann Equation In Non-critical Stringsmentioning

confidence: 76%

Section: Modified Boltzmann Equation In Non-critical Stringsmentioning

confidence: 88%

Section: The Final Form Of the Liouville Operation (220) Then Readsmentioning

confidence: 99%

Section: D X G Ementioning

confidence: 99%

See 2 more Smart Citations

Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances

2007

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“…Reducing them to four-dimensions and assuming that all the fields are time dependent we get an effective four-dimensional theory. We found that this theory in a Robertson-Walker background has an inflationary phase but we cannot exit from this phase in a smooth way [17]. We believe that the central issue of inflationary cosmology is not how we can get an inflationary phase, but how we can exit from it.…”

Section: Discussionmentioning

confidence: 84%

Inflation in String Theory and How You Can Get Out of it

Papantonopoulos

2002

Modern Theoretical and Observational Cosmology

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Inflation is now a basic ingredient of the modern cosmology. After reviewing the basic characteristics of inflation, we briefly discuss inflation in string and brane theories, focusing on the problem of the exit from inflation in these theories. We present a model, based on type-0 string theory, in which our universe after the inflationary phase, passes smoothly to a flat Robertson-Walker universe.

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On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

Mavromatos

2004

Springer Proceedings in Physics

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Abstract. I discuss various ways in which CPT symmetry may be violated, and their phenomenology in current or immediate future experimental facilities, both terrestrial and astrophysical. Specifically, I discuss first violations of CPT symmetry due to the impossibility of defining a scattering matrix as a consequence of the existence of microscopic or macroscopic space-time boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological horizons due to the presence of a (positive) cosmological constant in the Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry, which may characterize certain approaches to quantum gravity, and third, I describe models of CPT non invariance due to violations of locality of interactions. In each of the above categories I discuss experimental sensitivities. I argue that the majority of Lorentz-violating cases of CPT breaking, with minimal (linear) suppression by the Planck-mass scale, are already excluded by current experimental tests. There are however some (stringy) models which can evade these constraints. CPT Breaking and the Scattering MatrixThe symmetry under the successive operations (in any order) of charge conjugation, C, parity (reflexion), P, and time reversal, T, known as CPT, is a fundamental symmetry of any local quantum field theory in flat space time, under the following assumptions [1]:• (i) Unitarity and the proper definition of a scattering matrix, • (ii) Lorentz Invariance and • (iii) Locality of InteractionsIn the presence of gravity, i.e. non-Minkowski,non-flat space time backgrounds, CPT symmetry may be violated, at least in in its strong form. This is indeed the case of singular space-time gravitational backgrounds, such as black holes, or in general space times with boundaries. The reason is that in such cases the presence of these boundaries jeopardizes requirements (i) and (ii) of the CPT theorem. In a quantum context, a Black hole evaporates due to Hawking radiation, and as such it may 'capture' for ever information on matter states passing nearby, as depicted schematically in figure 1. In such a case, one may not be able to define properly asymptotic state vectors |ψ > in a quantum context, given that Planck size black hole horizons appear as fluctuations of the geometry, and hence an asymptotic observer will necessarily trace out the information captured by the horizons. This means that the out states will be necessarily described by density matrices, ρ = Tr unobs |ψ >< ψ|. One has therefore an evolution from pure states to mixed, and unitarity is lost. The problem in defining asymptotic state vectors also implies the impossibility of defining a proper scattering S-matrix, since the latter connects by definition "in" and "out" state vectors: |OU T >= S|IN >. Instead, one can only define a Hawking $-matrix [2], which connects IN and OUT mixed states described by density matrices:where $ = SS † , with S = e iHt the S-matrix, and H the Hamiltonian of the matter subsystem. The $-matrix has no inverse, as a consequence...

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Cosmological Evolution in a Type-0 String Theory

Cited by 36 publications

References 28 publications

Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances

Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances

Inflation in String Theory and How You Can Get Out of it

On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

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