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Title
Abstract
Introduction
The Background Setup
Some Limiting Cases of Einstein-GB-Dilaton Model
Conclusion
References
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Physics
Particle Physics

Modulus stabilization in higher curvature dilaton gravity

Profile image of Sayantan ChoudhurySayantan Choudhury

2014, Journal of High Energy Physics

https://doi.org/10.1007/JHEP08(2014)004
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20 pages

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Abstract

We propose a framework of modulus stabilization in two brane warped geometry scenario in presence of higher curvature gravity and dilaton in bulk space-time. In the prescribed setup we study various features of the stabilized potential for the modulus field, generated by a bulk scalar degrees of freedom with quartic interactions localized on the two 3-branes placed at the orbifold fixed points. We determine the parameter space for the gravidilaton and Gauss-Bonnet couplings required to stabilize the modulus in such higher curvature dilaton gravity setup.

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    COSMOS-e’-GTachyon from string theory
    Sayantan Choudhury

    The European Physical Journal C, 2016

    In this article, our prime objective is to study the inflationary paradigm from generalized tachyon (GTachyon) living on the world volume of a non-BPS string theory. The tachyon action is considered here is getting modified compared to the original action. One can quantify the amount of the modification via a power q instead of 1/2 in the effective action. Using this set up we study inflation from various types of tachyonic potentials, using which we constrain the index q within, 1/2 < q < 2, and a specific combination (∝ α M 4 s /g s) of Regge slope α , string coupling constant g s and mass scale of tachyon M s , from the recent Planck 2015 and Planck+BICEP2/Keck Array joint data. We explicitly study the inflationary consequences from single field, assisted field and multi-field tachyon set up. Specifically for single field and assisted field case we derive the results in the quasi-de-Sitter background in which we will utilize the details of cosmological perturbations and quantum fluctuations. Also we derive the expressions for all inflationary observables using any arbitrary vacuum and Bunch-Davies vacuum. For single field and assisted field case we derive-the inflationary flow equations, new sets of consistency relations. Also we derive the field excursion formula for tachyon, which shows that assisted inflation is in more safer side compared to the single field case to validate effective field theory framework. Further we study the features of CMB Angular power spectrum from TT, TE and EE correlations from scalar fluctuations within the allowed range of q for each potentials from single field setup. We also put constraints from the temperature anisotropy and polarization spectra, which shows that our analysis is consistent with the Planck 2015 data. Finally, using δN formalism we derive the expressions for inflationary observables in the context of multi-field tachyons.

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    COSMOS- $$e'$$ e ′ -soft Higgsotic attractors
    Sayantan Choudhury

    The European Physical Journal C, 2017

    In this work, we have developed an elegant algorithm to study the cosmological consequences from a huge class of quantum field theories (i.e. superstring theory, supergravity, extra dimensional theory, modified gravity, etc.), which are equivalently described by soft attractors in the effective field theory framework. In this description we have restricted our analysis for two scalar fields-dilaton and Higgsotic fields minimally coupled with Einstein gravity, which can be generalized for any arbitrary number of scalar field contents with generalized non-canonical and non-minimal interactions. We have explicitly used R 2 gravity, from which we have studied the attractor and non-attractor phases by exactly computing two point, three point and four point correlation functions from scalar fluctuations using the In-In (Schwinger-Keldysh) and the δN formalisms. We have also presented theoretical bounds on the amplitude, tilt and running of the primordial power spectrum, various shapes (equilateral, squeezed, folded kite or counter-collinear) of the amplitude as obtained from three and four point scalar functions, which are consistent with observed data. Also the results from two point tensor fluctuations and the field excursion formula are explicitly presented for the attractor and non-attractor phase. Further, reheating constraints, scale dependent behavior of the couplings and the dynamical solution for the dilaton and Higgsotic fields are also presented. New sets of consistency relations between two, three and four point observables are also presented, which shows significant deviation from canonical slow-roll models. Additionally, three possible theoretical proposals have presented to overcome the tachyonic instability at the time of late time acceleration. Finally, we have also provided the bulk interpretation from the three and four point scalar correlation functions for completeness.

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