Bouncing cosmology from warped extra dimensional scenario

The European Physical Journal C, Nov 2017

From the perspective of four dimensional effective theory on a two brane warped geometry model, we examine the possibility of “bouncing phenomena”on our visible brane. Our results reveal that the presence of a warped extra dimension lead to a non-singular bounce on the brane scale factor and hence can remove the “big-bang singularity”. We also examine the possible parametric regions for which this bouncing is possible.

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Bouncing cosmology from warped extra dimensional scenario

Eur. Phys. J. C Bouncing cosmology from warped extra dimensional scenario Ashmita Das 1 Debaprasad Maity 1 Tanmoy Paul 0 Soumitra SenGupta 0 0 Department of Theoretical Physics, Indian Association for the Cultivation of Science , 2A & 2B Raja S.C. Mullick Road, Kolkata 700 032 , India 1 Department of Physics, Indian Institute of Technology , North Guwahati, Guwahati, Assam 781039 , India From the perspective of four dimensional effective theory on a two brane warped geometry model, we examine the possibility of “bouncing phenomena”on our visible brane. Our results reveal that the presence of a warped extra dimension lead to a non-singular bounce on the brane scale factor and hence can remove the “big-bang singularity”. We also examine the possible parametric regions for which this bouncing is possible. 1 Introduction Over the last two decades models with extra spatial dimensions [1–13] have been increasingly playing a central role in physics beyond the standard model of particle [14] and cosmological [15] physics. Apart from the phenomenological approach, higher dimensional scenarios occur naturally in string theory. Depending on different possible compactification schemes for the extra dimensions, a large number of models have been constructed, and their predictions are yet to be observed in the current experiments. In all these models, our visible universe is identified as one of the three branes embedded within a higher dimensional spacetime. The low energy effective description [16–18] of the dynamical three brane turned out to be a very powerful tool in studying the dynamics ranging from particle to cosmology. In our present work we will take this ansatz to understand cosmological bouncing phenomena in the early universe cosmology considering the Randall–Sundrum two brane model. Among various extra dimensional models proposed over the last several years, the Randall–Sundrum (RS) warped extra dimensional model [6] earned special attention since it can resolve the gauge hierarchy problem without introducing any intermediate scale (between Planck and TeV) in the theory. The RS model is a five dimensional AdS space with S1/Z2 orbifolding along the extra dimension while two three branes are placed at the orbifold fixed points. The bulk negative cosmological constant along with appropriate boundary conditions generate exponentially warped geometry along the extra dimension. Due to this exponential warping, the Planck scale on one brane gets suppressed along the extra dimension and emerges as TeV scale [6] on the visible brane. In the RS model the interbrane separation (known as modulus or radion) is ∼ Planck length and generates the required hierarchy between the branes. Subsequently, Goldberger and Wise (GW) proposed a modulus stabilzation mechanism [19] by introducing a massive scalar field in the bulk with appropriate boundary conditions. Different variants of the RS model and its modulus stabilization are extensively studied in [21–28]. In this paper we will consider a specific variant of RS scenario and study the cosmological dynamics from the perspective of low energy effective field theory induced on the visible brane. It is well known that standard Big Bang scenario is quite successful in explaining many aspects of cosmological evolution of our universe. However, the big-bang model is plagued with a singularity (known as “cosmological singularity”) in the finite past. Resolving this time like cosmological singularity is an important issue which is a subject of great research in theoretical cosmology for the last several decades. It is widely believed that quantum theory of gravity, if any, should play very important role in resolving this singularity. One of the important aspects of all the known non-singular cosmological models is the existence of pre Big-Bang universe [29]. In terms of effective theory, different models of nonsingular cosmologies, such as ekpyrotic universe [30,31], loop quantum cosmology [32,33], Galileon genesis [34–36], or the classical bouncing model, can be described by gravity coupled to a scalar field which generically violates the null energy condition at the background level. Therefore, the scale factor of the universe undergoes a non-singular bounce geometry has S1/Z2 orbifolding along the extra dimension. Taking ϕ as the extra dimensional angular coordinate, the branes are situated at orbifolded fixed points i.e. at ϕ = 0 (Planck brane) and ϕ = π (TeV brane), respectively, while our visible universe is identified with the TeV scale brane. The proper distance between the branes is considered as a function of spacetime coordinates. The action of this model [16] is the following: 1 S = 2κ2 d4x dϕ√−G R( 5 ) + (12/ l2) − d4x √−ghid Vhid + √ −gvisVvis with x μ = (x 0, x 1, x 2, x 3) the brane coordinates. 2κ12 = M 3, M is the five dimensional Planck mass. R( 5 ) and l (∼ Planck length) are the Ricci scalar and curvature radius of the five dimensional spacetime, re (...truncated)


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Ashmita Das, Debaprasad Maity, Tanmoy Paul, Soumitra SenGupta. Bouncing cosmology from warped extra dimensional scenario, The European Physical Journal C, 2017, pp. 813, Volume 77, Issue 12, DOI: 10.1140/epjc/s10052-017-5396-2