Cosmological power spectrum in a noncommutative spacetime

Kothari, Rahul; Rath, Pranati K.; Jain, Pankaj

doi:10.1103/physrevd.94.063531

Cited by 5 publications

(5 citation statements)

References 59 publications

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“…Our results imply that the presence of non-diagonal correlations in the polarization field, suggested in the literature [17], cannot be attributed to a modulation in the scalar modes E and B. However our analysis doesn't rule out the possibility that such correlations can arise due to modified power spectra based models [16][17][18][19][20][21][22] that may further arise due to reasons like spacetime non-commutativity [18,43], direction Fig. 2 Plot of the modulating function f in different cases.…”

Section: Discussionmentioning

confidence: 64%

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A comprehensive study of modulation effects on CMB polarization

Kothari

2022

Gen Relativ Gravit

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The Cosmic Microwave Background is characterized by temperature and linear polarization fields. Dipole modulation in the temperature field has been extensively studied in the context of hemispherical power asymmetry. In this article, we show that a dipole modulation, and in general, any kind of modulation isn't allowed in the E and B modes. This is the main result of this paper. This result explains why no evidence of modulation in E mode has been found in the literature. On the contrary, the linear polarization fields Q and U have no such restrictions. We show that modulation under certain situations can be thought of as local U (1) gauge transformations on the surface of a sphere. As far as the modulation function is concerned, we show that physical considerations enforce it to be (i) a spin 0 field and (ii) a scalar under parity. As masking is a specific type of modulation, our study suggests that a direct masking of E mode isn't also possible. Masking in E map can only be applied through Q and U fields. This means that in principle, leaking of E and B mode powers into each other is unavoidable. KeywordsCosmic microwave background • Polarization • Modulation B Rahul Kothari

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Section: Discussionmentioning

confidence: 64%

“…For example, a dipole modulation leads to non diagonal correlations between and ± 1 multipoles. In the literature, the presence of these non-diagonal correlations has been explained on the basis of modification of the primordial power spectrum [16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

A comprehensive study of modulation effects on CMB polarization

Kothari

2022

Gen Relativ Gravit

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“…Similar ideas have been explored in order to explain the hemispherical anisotropy (Rath et al, 2015;Jain and Rath, 2015;Kothari et al, 2015a;Ghosh et al, 2016). However in this case an explicit model requires either an inhomogeneous Universe (Carroll et al, 2010;Rath et al, 2015) or space-time noncommutativity (Jain and Rath, 2015;Kothari et al, 2015b). A detailed analysis of such models is so far not available in the literature.…”

Section: Theoretical Expectationsmentioning

confidence: 99%

Probing Statistical Isotropy of Cosmological Radio Sources using Square Kilometre Array

et al. 2016

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There currently exist many observations which are not consistent with the cosmological principle. We review these observations with a particular emphasis on those relevant for Square Kilometre Array (SKA). In particular, several different data sets indicate a preferred direction pointing approximately towards the Virgo cluster. We also observe a hemispherical anisotropy in the Cosmic Microwave Background Radiation (CMBR) temperature fluctuations. Although these inconsistencies may be attributed to systematic effects, there remains the possibility that they indicate new physics and various theories have been proposed to explain them. One possibility, which we discuss in this review, is the generation of perturbation modes during the early pre-inflationary epoch, when the Universe may not obey the cosmological principle. Better measurements will provide better constraints on these theories. In particular, we propose measurement of the dipole in number counts, sky brightness, polarized flux and polarization orientations of radio sources. We also suggest test of alignment of linear polarizations of sources as a function of their relative separation. Finally we propose measurement of hemispherical anisotropy or equivalently dipole modulation in radio sources.

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“…The correction to Bekenstein-Hawking entropy in noncommutative space-time was studied in [41]. Different features of non-commutative field theoretical models in FLRW space-time were investigated in [42,43]. Using squashed fuzzy sphere, the super Chandrasekhar limit for a white dwarf mass was calculated in [44].…”

Section: Introductionmentioning

confidence: 99%

Newtonian Cosmology and Evolution of κ-Deformed Universe

Harikumar,

Sreekumar,

Panja

2023

Universe

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Considering space-time to be non-commutative, we study the evolution of the universe employing the approach of Newtonian cosmology. Generalizing the conservation of energy and the first law of thermodynamics to κ-deformed space-time, we derive the modified Friedmann equations, valid up to the first order, in the deformation parameter. Analyzing these deformed equations, we derive the time evolution of the scale factor in cases of radiation-dominated, matter-dominated, and vacuum (energy)-dominated universes. We show that the rate of change of the scale factor in all three situations is modified by the non-commutativity of space-time, and this rate depends on the sign of the deformation parameter, indicating a possible explanation for the observed Hubble tension. We undertake this investigation for two different realizations of non-commutative space-time coordinates. In both cases, we also argue for the existence of bounce in the evolution of the universe.

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Cosmological power spectrum in a noncommutative spacetime

Cited by 5 publications

References 59 publications

A comprehensive study of modulation effects on CMB polarization

A comprehensive study of modulation effects on CMB polarization

Probing Statistical Isotropy of Cosmological Radio Sources using Square Kilometre Array

Newtonian Cosmology and Evolution of κ-Deformed Universe

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