Particle Creation and Excited-de Sitter Modes

Recently, in Ref.\cite{moh1}, we introduced exited-de Sitter modes to study the power spectrum which was finite in Krein space quantization and the trans-Plankian corrections due to the exited modes were non-linear. It was shown that the de Sitter limit of corrections reduces to what obtained via the several previous conventional methods, moreover, with such modes the space-time symmetry becomes manifest. In this paper, inspired by Krein method and using exited-de Sitter modes as the fundamental initial states during the inflation, we calculate particle creation in the spatially flat Robertson-Walker space-time. It is shown that in de Sitter and Minkowski space-time in the far past time limit, our results coincides to the standard results.Comment: 8 page

Evolution of Bulk Scale Factor in Warped Space-time

In this work the role of extra dimensions in the accelerated universe through the scenario of higher-dimensional Friedmann-Robertson-Walker (FRW) cosmology has been studied. For this purpose, we first consider warped space-time in the standard flat brane scenario as the modified form of Robertson-Walker (RW) metric in five-dimension (5D) space-time and then the variation of the bulk scale factor (warp factor), with respect to both space-like and time-like extra dimensions is obtained. Finally, it is shown that both of two types of extra dimensions are important in this scenario and also the bulk scale factor plays two different roles.Comment: This paper has been withdrawn by the author due to text overlap with arXiv:0710.3790 by other author

Spectrum of Gravitational Waves in Krein Space Quantization

The main goal of this paper is to derive the primordial power spectrum for the scalar perturbations generated as a result of quantum fluctuations during an inflationary pe- riod by an alternative approach of field quantization[1-3]. Formulas are derived for the gravitational waves, special cases of which include power law inflation and inflation in the slow roll approximation, in Krein space quantization.Comment: 6 pages, published in MPL

Scale-dependent power spectrum from initial excited-de Sitter modes

In this paper, we calculate corrections of scalar perturbations spectra resulting from excited-de Sitter modes as the nontrivial initial states. To obtain these modes, we consider the asymptotic expansion of the Hankel functions up to the higher order of 1/k{\tau} . Actually the Planck and WMAP data impose some constrains on the Hankel function index. These observational constraints and back-reaction effects stimulate us to use excited-de Sitter modes. Finally, we nominate these nontrivial general solutions as the fundamental mode functions during inflation and we calculate the corrected form of scale-dependent power spectrum with trans-Planckian corrections, and in de Sitter space-time limit the results reduce to the scale-invariant power spectrum.Comment: 16 pages, Title slightly modified, Back-reaction added,Some references added, Published open access in JHE

Power Spectrum with Auxiliary Fields in de Sitter Space

We use the auxiliary fields and (excited-) de Sitter solutions to study the standard power spectrum of primordial fluctuations of a scalar field in the early universe. The auxiliary fields are the negative norm solutions of the field equation and as it is shown, with a fixed boundary condition, utilizing these states results in a finite power spectrum without any infinity. The power spectrum is determined by the de Sitter solutions up to some corrections and the space-time symmetry is not broken in this point of view. The modulation to the power spectrum is of order $(\frac{H}{\Lambda})^{2}$, where $H$ is the Hubble parameter and $\Lambda$ is the energy scale, e.g., Planck scale.Comment: 7 pages, Krein discussion and section 3 improved, To appear in European Physical Journal