Signature of the Quantum Gravity
on the CMB
P. K. Suresh
Abstract The quantum gravity effect on chaotic inflation reduces its tensor-to-scalar
ratio than its predicted value and is found less than the estimated upper bound from
the various CMB observations. The lowering nature of the power level of the lensed
BB mode angular power spectrum, especially at lower multipoles, compared to the
absence of the quantum gravity effect, can be considered as the signature of the
quantum gravity on the CMB. The quantum gravity effect on the lensed BB mode
correlation angular power spectrum with BK15 and Planck 2018 joint data does not
rule out the chaotic inflationary models.
Keywords Quantum gravity · Inflation · CMB
1 Introduction
Despite several approaches developed in understanding quantum gravity over
decades, still there is no complete and satisfactory theory of quantum gravity. Therefore, a viable theory for quantum gravity remains a formidable challenging task even
today. However, it does not prevent us from exploring the observational consequence
of quantum gravity effect through some suitable experiments. Recently, it is remarked
that the effect of quantum gravity can be explored through cosmic microwave background radiation (CMB) through inflation and appears to be very promising. Hence,
hopefully, the CMB can be used as a testing arena for any theory of quantum gravity.
Inflation is a scenario proposed to resolve some of the shortcomings of the standard
cosmology [1–8]. According to the inflationary scenario, the universe expanded several folds for a brief interval of time during its very early stage of evolution. One
of the attractive features of inflation is that it seeded the formation of large-scale
structures in the universe and also possibly generated primordial gravitational waves
that are yet to be discovered. Therefore, the detection of the primordial gravitational
P. K. Suresh (B)
School of Physics, University of Hyderabad, Hyderabad, Telangana, India
e-mail: sureshpk@uohyd.ac.in
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
K. S. Sreelatha and V. Jacob (eds.), Modern Perspectives in Theoretical Physics,
https://doi.org/10.1007/978-981-15-9313-0_3
23
on the CMB
P. K. Suresh
Abstract The quantum gravity effect on chaotic inflation reduces its tensor-to-scalar
ratio than its predicted value and is found less than the estimated upper bound from
the various CMB observations. The lowering nature of the power level of the lensed
BB mode angular power spectrum, especially at lower multipoles, compared to the
absence of the quantum gravity effect, can be considered as the signature of the
quantum gravity on the CMB. The quantum gravity effect on the lensed BB mode
correlation angular power spectrum with BK15 and Planck 2018 joint data does not
rule out the chaotic inflationary models.
Keywords Quantum gravity · Inflation · CMB
1 Introduction
Despite several approaches developed in understanding quantum gravity over
decades, still there is no complete and satisfactory theory of quantum gravity. Therefore, a viable theory for quantum gravity remains a formidable challenging task even
today. However, it does not prevent us from exploring the observational consequence
of quantum gravity effect through some suitable experiments. Recently, it is remarked
that the effect of quantum gravity can be explored through cosmic microwave background radiation (CMB) through inflation and appears to be very promising. Hence,
hopefully, the CMB can be used as a testing arena for any theory of quantum gravity.
Inflation is a scenario proposed to resolve some of the shortcomings of the standard
cosmology [1–8]. According to the inflationary scenario, the universe expanded several folds for a brief interval of time during its very early stage of evolution. One
of the attractive features of inflation is that it seeded the formation of large-scale
structures in the universe and also possibly generated primordial gravitational waves
that are yet to be discovered. Therefore, the detection of the primordial gravitational
P. K. Suresh (B)
School of Physics, University of Hyderabad, Hyderabad, Telangana, India
e-mail: sureshpk@uohyd.ac.in
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
K. S. Sreelatha and V. Jacob (eds.), Modern Perspectives in Theoretical Physics,
https://doi.org/10.1007/978-981-15-9313-0_3
23