Cosmic Microwave Background Anisotropy: A Critical Test for Early Universe Inflation Theories
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Cosmic Microwave Background Anisotropy: A Critical Test for Early Universe Inflation Theories

Chenghao Sun 1*
1 Suzhou Foreign Language School
*Corresponding author: sflssunchenghao@163.com
Published on 2 October 2025
Journal Cover
TNS Vol.143
ISSN (Print): 2753-8826
ISSN (Online): 2753-8818
ISBN (Print): 978-1-80590-407-6
ISBN (Online): 978-1-80590-408-3
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Abstract

An important tool for humans to comprehend the physics of the early cosmos is CMB anisotropies, which can also be used to evaluate inflationary hypotheses. These days, evidence of inflationary theories has been provided by data from COBE, WMAP, Plank, and BICEP/Keck, particularly an almost scale-invariant and adiabatic spectrum. The origin of initial conditions, the trans-Planckian dilemma, and the fine-tuning of the inflaton potential were among the unanswered concerns that the theories also had to deal with. Furthermore, challenges like as foreground pollution and cosmic variance remain. Future prospects are bright since next-generation systems like CMB-S4 and LiteBIRD can overcome these obstacles. Their sensitivity will allow for considerably more precise probing of primordial B-modes, μ-distortions, and non-Gaussianity.

Keywords:

CMB anisotropy, inflationary model, B-mode polarization, future CMB missions

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Sun,C. (2025). Cosmic Microwave Background Anisotropy: A Critical Test for Early Universe Inflation Theories. Theoretical and Natural Science,143,34-41.

References

[1]. Cosmic Microwave Background (CMB) radiation . https: //www.esa.int/Science_Exploration/Space_Science/Cosmic_Microwave_Background_CMB_radiation.

[2]. Cosmic Microwave Background Center for Astrophysics Harvard & Smithsonian (2024). https: //www.cfa.harvard.edu/research/topic/cosmic-microwave-background.

[3]. Gümrükçüo, A.E., Contaldi, C.R. and Peloso, M. (2007) Inflationary perturbations in anisotropic backgrounds and their imprint on the cosmic microwave background, Journal of Cosmology and Astroparticle Physics, 11, 005.

[4]. Linde, A.D. (1983) Chaotic inflation, Physics Letters B, 129(3–4), 177–181. https: //doi.org/10.1016/0370-2693(83)90837-7.

[5]. Linde, A. (1994) Hybrid inflation, Physical Review. D. Particles, Fields, Gravitation, and Cosmology/Physical Review. D. Particles and Fields, 49(2), 748–754.

[6]. Challinor, A. (2012) CMB anisotropy science: a review, Proceedings of the International Astronomical Union, 8(S288), 42–52.

[7]. Durrer, R. (2001) The theory of CMB anisotropies, J. Phys. Stud., 5, 177-215

[8]. Jones, W.C. et al. (2006) A Measurement of the Angular Power Spectrum of the CMB Temperature Anisotropy from the 2003 Flight of BOOMERANG, The Astrophysical Journal, 647(2), 823–832.

[9]. Ade, P. a. R. et al. (2014) Detection of B-Mode polarization at degree angular scales by BICEP2, Physical Review Letters, 112(24).

[10]. Hancock, S. et al. (1997) Constraints on cosmological parameters from recent measurements of CMB anisotropy, arXiv (Cornell University) [Preprint].

[11]. Ade, P. a. R. et al. (2021) Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/ Keck Observations through the 2018 Observing Season, Physical Review Letters, 127(15).

[12]. Cabella, P. and Marinucci, D. (2009) Statistical challenges in the analysis of Cosmic Microwave Background radiation, The Annals of Applied Statistics, 3(1).

[13]. Tucci, M. et al. (2005) Limits on the detectability of the CMB B-mode polarization imposed by foregrounds, Monthly Notices of the Royal Astronomical Society, 360(3), 935–949.

[14]. Zegeye, D. et al. (2023) CMB-S4: Forecasting Constraints on fNL Through μ-distortion Anisotropy, arXiv (Cornell University) [Preprint].

[15]. Allys, E. et al. (2022) Probing cosmic inflation with the LiteBIRD cosmic microwave background polarization survey, Progress of Theoretical and Experimental Physics, 2023(4).

[16]. Naruko, A., Komatsu, E. and Yamaguchi, M. (2015) Anisotropic inflation reexamined: upper bound on broken rotational invariance during inflation, Journal of Cosmology and Astroparticle Physics, 2015(4), 045.

[17]. Watanabe, M.A., Kanno, S. and Soda, J. (2011) Imprints of the anisotropic inflation on the cosmic microwave background, Monthly Notices of the Royal Astronomical Society Letters, 412(1), L83–L87.

[18]. Bartolo, N. et al. (2014) The expected anisotropy in solid inflation, Journal of Cosmology and Astroparticle Physics, 2014(11), 009.

[19]. Brandenberger, R.H. (2002) Principles, progress and Problems in inflationary Cosmology, arXiv (Cornell University) [Preprint].

[20]. Efstathiou, G. (2001) CMB anisotropies and the determination of cosmological parameters, in Springer eBooks, 179–189.

References

[1]. Cosmic Microwave Background (CMB) radiation . https: //www.esa.int/Science_Exploration/Space_Science/Cosmic_Microwave_Background_CMB_radiation.

[2]. Cosmic Microwave Background Center for Astrophysics Harvard & Smithsonian (2024). https: //www.cfa.harvard.edu/research/topic/cosmic-microwave-background.

[3]. Gümrükçüo, A.E., Contaldi, C.R. and Peloso, M. (2007) Inflationary perturbations in anisotropic backgrounds and their imprint on the cosmic microwave background, Journal of Cosmology and Astroparticle Physics, 11, 005.

[4]. Linde, A.D. (1983) Chaotic inflation, Physics Letters B, 129(3–4), 177–181. https: //doi.org/10.1016/0370-2693(83)90837-7.

[5]. Linde, A. (1994) Hybrid inflation, Physical Review. D. Particles, Fields, Gravitation, and Cosmology/Physical Review. D. Particles and Fields, 49(2), 748–754.

[6]. Challinor, A. (2012) CMB anisotropy science: a review, Proceedings of the International Astronomical Union, 8(S288), 42–52.

[7]. Durrer, R. (2001) The theory of CMB anisotropies, J. Phys. Stud., 5, 177-215

[8]. Jones, W.C. et al. (2006) A Measurement of the Angular Power Spectrum of the CMB Temperature Anisotropy from the 2003 Flight of BOOMERANG, The Astrophysical Journal, 647(2), 823–832.

[9]. Ade, P. a. R. et al. (2014) Detection of B-Mode polarization at degree angular scales by BICEP2, Physical Review Letters, 112(24).

[10]. Hancock, S. et al. (1997) Constraints on cosmological parameters from recent measurements of CMB anisotropy, arXiv (Cornell University) [Preprint].

[11]. Ade, P. a. R. et al. (2021) Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/ Keck Observations through the 2018 Observing Season, Physical Review Letters, 127(15).

[12]. Cabella, P. and Marinucci, D. (2009) Statistical challenges in the analysis of Cosmic Microwave Background radiation, The Annals of Applied Statistics, 3(1).

[13]. Tucci, M. et al. (2005) Limits on the detectability of the CMB B-mode polarization imposed by foregrounds, Monthly Notices of the Royal Astronomical Society, 360(3), 935–949.

[14]. Zegeye, D. et al. (2023) CMB-S4: Forecasting Constraints on fNL Through μ-distortion Anisotropy, arXiv (Cornell University) [Preprint].

[15]. Allys, E. et al. (2022) Probing cosmic inflation with the LiteBIRD cosmic microwave background polarization survey, Progress of Theoretical and Experimental Physics, 2023(4).

[16]. Naruko, A., Komatsu, E. and Yamaguchi, M. (2015) Anisotropic inflation reexamined: upper bound on broken rotational invariance during inflation, Journal of Cosmology and Astroparticle Physics, 2015(4), 045.

[17]. Watanabe, M.A., Kanno, S. and Soda, J. (2011) Imprints of the anisotropic inflation on the cosmic microwave background, Monthly Notices of the Royal Astronomical Society Letters, 412(1), L83–L87.

[18]. Bartolo, N. et al. (2014) The expected anisotropy in solid inflation, Journal of Cosmology and Astroparticle Physics, 2014(11), 009.

[19]. Brandenberger, R.H. (2002) Principles, progress and Problems in inflationary Cosmology, arXiv (Cornell University) [Preprint].

[20]. Efstathiou, G. (2001) CMB anisotropies and the determination of cosmological parameters, in Springer eBooks, 179–189.

Cite this article

Sun,C. (2025). Cosmic Microwave Background Anisotropy: A Critical Test for Early Universe Inflation Theories. Theoretical and Natural Science,143,34-41.

Data availability

The datasets used and/or analyzed during the current study will be available from the authors upon reasonable request.

About volume

Volume title: Proceedings of CONF-CIAP 2026 Symposium: International Conference on Atomic Magnetometer and Applications

ISBN: 978-1-80590-407-6(Print) / 978-1-80590-408-3(Online)
Editor: Marwan Omar , Jixi Lu , Mao Ye
Conference website: https://2026.confciap.org/hangzhou.html
Conference date: 30 January 2026
Series: Theoretical and Natural Science
Volume number: Vol.143
ISSN: 2753-8818(Print) / 2753-8826(Online)

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