Aspects of Two Measures Theory

Guendelman, Eduardo; Vasihoun, Mahary

doi:10.1142/9789814623995_0103

Cited by 2 publications

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“…The methods outlined there can be also applied in the modified measure case [92], thus providing another derivation of the effective action explained above.…”

Section: Fluctuationsmentioning

confidence: 99%

Connecting the Non-Singular Origin of the Universe, the Vacuum Structure and the Cosmological Constant Problem

Guendelman¹,

Labraña²

2015

The Thirteenth Marcel Grossmann Meeting

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We consider a non-singular origin for the Universe starting from an Einstein static Universe, the so called "emergent universe" scenario, in the framework of a theory which uses two volume elements √ −gd 4 x and Φd 4 x, where Φ is a metric independent density, used as an additional measure of integration. Also curvature, curvature square terms and for scale invariance a dilaton field φ are considered in the action. The first order formalism is applied. The integration of the equations of motion associated with the new measure gives rise to the spontaneous symmetry breaking (S.S.B) of scale invariance (S.I.). After S.S.B. of S.I., it is found that a non trivial potential for the dilaton is generated. In the Einstein frame we also add a cosmological term that parametrizes the zero point fluctuations. The resulting effective potential for the dilaton contains two flat regions, for φ → ∞ relevant for the non-singular origin of the Universe, followed by an inflationary phase and φ → −∞, describing our present Universe. The dynamics of the scalar field becomes non linear and these non linearities produce a non trivial vacuum structure for the theory and are responsible for the stability of some of the emergent universe solutions, which exists for a parameter range of values of the vacuum energy in φ → −∞, which must be positive but not very big, avoiding the extreme fine tuning required to keep the vacuum energy density of the present universe small. The non trivial vacuum structure is crucial to ensure the smooth transition from the emerging phase, to an inflationary phase and finally to the slowly accelerated universe now. Zero vacuum energy density for the present universe defines the threshold for the creation of the universe.

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“…The methods outlined there can be also applied in the modified measure case [92], thus providing another derivation of the effective action explained above.…”

Section: Fluctuationsmentioning

confidence: 99%

Connecting the Non-Singular Origin of the Universe, the Vacuum Structure and the Cosmological Constant Problem

Guendelman¹,

Labraña²

2015

The Thirteenth Marcel Grossmann Meeting

Self Cite

View full text Add to dashboard Cite

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“…Some applications have been, (i) D = 4-dimensional models of gravity and matter fields containing the new measure of integration appear to be promising candidates for resolution of the dark energy and dark matter problems, the fifth force problem, and a natural mechanism for spontaneous breakdown of global Weyl-scale symmetry [23]- [29], (ii) To study of reparametrization invariant theories of extended objects (strings and branes) based on employing of a modified non-Riemannian world-sheet/world-volume integration measure [30,31], leads to dynamically induced variable string/brane tension and to string models of 3 of 32 non-abelian confinement, interesting consequences from the modified measures spectrum [32], and construction of new braneworld scenarios [33], (iii) To study in Ref. [34] of modified supergravity models with an alternative non-Riemannian volume form on the space-time manifold .…”

Section: Introductionmentioning

confidence: 99%

Unification: inflation and dark epochs from multi-field theory.

Guendelman,

Herrera

2024

Preprint

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A two scalar field model that incorporates non Riemannian Measures of integration or usually called Two Measures Theory (TMT) is introduced, in order to unify the early and present universe. In the Einstein frame, a K-essence is generated and as a consequence for the early universe, we can have an Inflation for the very early universe and then, after inflation, an early dark energy period and a late dark energy period for the present universe dark, both dark energy epochs have a consistent generation of dark energy (DE), dark matter (DM) and stiff matter. This is obtained when the scale invariance is introduced and then is spontaneously broken from the integration of the degrees of freedom associated with the modified measures. The resulting effective potentials and K-essence in the Einstein frame produce the three flat regions corresponding to the different epochs mentioned before. For the first flat region, we can associate an inflationary universe. Also assuming this first plateau, we study the inflation in the framework of the slow-roll approximation. In this scenario under the slow roll approximation, we obtain a linear combination that is a constant. The corresponding cosmological perturbations in our model are determined and we also obtain the different constraints on the parameter-space from the Planck data. The slow roll approximation can be arranged so that the transition from inflation to the next flat region can be achieved without problems. In the following two flat regions, in addition to the inflation phase, representing the Early Dark Energy and Late Dark Energy Periods, with DE and also the DM, do not need to be introduced separately, they are instead a result of a K-essence induced by the multi measures, multi field theory. Therefore the scalars generate both the DE and the DM . Also a stiff matter component is automatically generated from the K-essence theory from two scalar fields. From the perturbative analysis associated to the perturbation solution of background, we find a correlation between the two scalars. Besides, we obtain that our model during the dark epoch has a behaviour of tracking freezing mode

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Aspects of Two Measures Theory

Cited by 2 publications

References 0 publications

Connecting the Non-Singular Origin of the Universe, the Vacuum Structure and the Cosmological Constant Problem

Connecting the Non-Singular Origin of the Universe, the Vacuum Structure and the Cosmological Constant Problem

Unification: inflation and dark epochs from multi-field theory.

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