On the perturbation theory in spatially closed background

Asgari, Ali A.; Abbassi, Amir H.; Khodagholizadeh, Jafar

doi:10.1140/epjc/s10052-014-2917-0

Cited by 13 publications

(25 citation statements)

References 44 publications

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“…It can be shown that in thecomoving gauge δρ = δp = − E 2a 2Φ′2 and δΦ = 0, where ρ and p are energy density and pressure of the perfect fluid associated with the inflation. Now from combination of the perturbative field equations as well as the energy conservation law[37] we may extract an explicit equation for the evolution of R in the inflation epoch…”

mentioning

confidence: 99%

Scalar and tensor power spectra in a universe with positive curvature index and maximally symmetric spatial section

Asgari

Abbassi

2015

Physics of the Dark Universe

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mentioning

confidence: 99%

Scalar and tensor power spectra in a universe with positive curvature index and maximally symmetric spatial section

Asgari

Abbassi

2015

Physics of the Dark Universe

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“…By replacing F n and G n from Eqs. (19), (20) and use the same procedures used for C S T E, derivation we find that…”

Section: Eementioning

confidence: 92%

An analytical approach to the CMB polarization in a spatially closed background

Niazy

Abbassi

2018

Physics of the Dark Universe

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The scalar mode polarization of the cosmic microwave background is derived in a spatially closed universe from the Boltzmann equation using the line of sight integral method. The EE and TE multipole coefficients have been extracted analytically by considering some tolerable approximations such as considering the evolution of perturbation hydrodynamically and sudden transition from opacity to transparency at the time of last scattering. As the major advantage of analytic expressions, C S EE, and C S T E, explicitly show the dependencies on baryon density Ω B , matter density Ω M , curvature Ω K , primordial spectral index n s , primordial power spectrum amplitude A s , Optical depth τ reion , recombination width σ t and recombination time t L . Using a realistic set of cosmological parameters taken from a fit to data from Planck, the closed universe EE and TE power spectrums in the scalar mode are compared with numerical results from the CAMB code and also latest observational data. The analytic results agree with the numerical ones on the big and moderate scales. The peak positions are in good agreement with the numerical result on these scales while the peak heights agree with that to within 20% due to the approximations have been considered for these derivations. Also, several interesting properties of CMB polarization are revealed by the analytic spectra.

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“…Such universe can be split as R × M where M is compact if K = +1 and non-compact if K = 0 or −1 (Indeed topology of the universe is R × M ). On the other hand, the energy-momentum of the cosmic fluid may be decomposed as [7] T 00 = a 2…”

Section: Generalized Mukhanov-sasaki Equationmentioning

confidence: 99%

“…By taking these two equations to the Fourier space i.e. using Fourier transformation on M (spatial slice of the universe) one can rewrite equations (12) and (13) as [7,16,17]…”

Section: Generalized Mukhanov-sasaki Equationmentioning

confidence: 99%

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Curvature and topology dependency of the cosmological spectra

2019

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In this article we investigate dependency of two important cosmological random fields defined on spatial slices of the FLRW universe and their spectra on the geometry and topology of the background universe. Our discussion includes the post-inflationary universe i.e. radiation-dust mixture era. For this purpose, we first extract an explicit equation describing evolution of the comoving curvature perturbation in the FLRW universe with arbitrary spatial sectional curvature. We may realize when K = 0, curvature scale may be as significant as the perturbations scales to recognize the behavior of the spectral indices. We also focus on the entropy perturbation in order to extract behavior of the isocurvature spectral index in terms of the curvature index and time. Our analysis shows that the adiabatic and entropy spectral indices of the cosmological perturbations (spectra of curvature and entropy perturbations) in sub-horizon scales could be function of topology. It may be significant because reveals imprints of geometry on the statistical information deduced by observations. Moreover, an accurate analysis makes clear that time-average of isocurvature index in case K = 0 is about zero,so that imprint of entropy perturbation in time duration may be negligible. We also consider evolution of the cosmological indices for super-curvature modes in case K = −1 . In the most results dependency to curvature, initial conditions and scale modes are thoroughly vivid.

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On the perturbation theory in spatially closed background

Cited by 13 publications

References 44 publications

Scalar and tensor power spectra in a universe with positive curvature index and maximally symmetric spatial section

Scalar and tensor power spectra in a universe with positive curvature index and maximally symmetric spatial section

An analytical approach to the CMB polarization in a spatially closed background

Curvature and topology dependency of the cosmological spectra

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