Cosmic Neutrino Background (CνB) Temperature Derived from the Stefan Boltzmann Law in R H t = c t Cosmolgy

We are proposing a temperature formula for the Cosmic Neutrino background (CνB) temperature that can be derived from the Stefan-Boltzman law under certain assumptions, such as $R_{H_t}=ct$ cosmology. Our derived formula gives a prediction of the CνB temperature of 1.9336 K ± 0.0072 K which is in line with the current literature on the topic.

• CνB Temperature
• CMB Temperature
• Reissner-Nordstrom Metric
• Haug Spavieri Metric

1. CMB Temperature

In contrast to the cosmic microwave background the cosmic neutrino background is very hard to detect directly as neutrinos are only known to have very weak interactions with other particles [1] , so before we get to how to predict it we will sumamrize some important development in relation to the CMB temperature. The CMB temperature is approximately 2.725 K [2] - [6] . Tatum, Seshavatharam, and SLakshminarayana [7] suggested based on heuristics that the CMB temperature for $R_H=ct$ cosmology could be given by:

$T_{cmb,t}=\frac{\hslash c^3}{k_{b}8\pi G\sqrt{M_{cr,t}{m}_p}}=\frac{\hslash c}{k_{b}4\pi \sqrt{R_{t}2l_p}}$(1)

where $R_t=\frac{c}{H_t}=ct$, $l_p=\sqrt{\frac{G\hslash }{c^3}}$ represents the Planck [8] [9] length, and $k_b$ denotes the Boltzmann constant. Furthermore $M_{cr,t}=\frac{c^2{R}_{H_t}}{2G}$ is the time dependent critical Friedmann [10] mass.

Haug and Wojnow [11] [12] are the first to demonstrate that the following formula can be derived from the Stefan-Boltzmann law:

$T_{cmb,t}=\frac{T_p}{8\pi }\sqrt{\frac{2l_p}{R_{H_t}}}$(2)

where $T_p=\sqrt{\frac{\hslash c^5}{G}}=\frac{m_p{c}^2}{k_b}$ is the Planck temperature. This Haug and Wojnow also demonstrated can be re-written into the Tatum et al formula.

Haug and Tatum [13] have indicated the CMB temperature also can be derived from geometric principles in a $R_h=ct$ type universe. See, for example, [14] . Haug [15] has demonstrated that the CMB temperature simply can be predicted as:

$T_{cmb,t}=\sqrt{T_{max}{T}_{min,t}}$(3)

where $T_{max}=\frac{\hslash c^3}{k_{b}8\pi G{m}_p}=\frac{\hslash c}{k_{b}8\pi l_p}$ is the Hawking [16] temperature of a Planck mass black hole and $T_{min,t}=\frac{\hslash c^3}{k_{b}8\pi G{M}_{bh}}=\frac{\hslash c}{k_{b}4\pi R_{H_t}}$ is the Hawking temperature of the Hubble sphere, when $M_{bh}=M_{cr}=\frac{c^2{R}_{H_t}}{2G}$ is the black hole mass equal to the critical Friedmann mass.

Equation (1), (2), and (3) are different ways to express the same concept. The most intuitive way is: $T_{cmb,t}=\sqrt{T_{max}{T}_{min,t}}$, as it shows that the CMB temperature is simply the geometric mean of the lowest and highest possible temperatures in the universe—something that is consistent with the universe being an ideal heat engine (Carnot engine); see [17] . The idea that the universe can operate as a heat engine is not new, nor is the idea that a black hole can possibly operate as a heat engine; see [18] - [24] . What is new is that Haug has recently demonstrated this leads to a CMB temperature that is the geometric mean of the maximum and minimum Hawking temperatures in a black hole universe.

2. Derivation of CνB Temperature from the Stefan-Boltzmann Law

The Cosmic Neutrino Background temperature is assumed to be approximately 1.95 K (see [25] ). The cosmic microwave background (CMB) radiation spectrum is known to be that of a nearly perfect black body. This has been pointed out by for example Muller et al. [26] :

“Observations with the COBE satellite have demonstrated that the CMB corresponds to a nearly perfect black body, characterized by a temperature $T_0$ at $z=0$, which is measured with very high accuracy, $T_0=2.72548\pm 0.00057\text{K}$.”

It is natural to assume also the Neutrino background fits well the assumption of almost a perfect black body and thereby one should be able to use the Stefan-Boltzmann law for deriving the CνB temperature. Relic neutrinos, while fermions, are often approximated as an almost perfect blackbody spectrum due to their thermal decoupling in the early universe while still relativistic. Their distribution follows a Fermi-Dirac function with zero chemical potential, contributing an energy density suppressed relative to photons by a factor of 7/8, characteristic of relativistic fermions. After electron-positron annihilation, entropy conservation yields the canonical temperature ratio $T_{\nu }={\left(\frac{4}{11}\right)}^{1/3}{T}_{\text{CMB}}$. While bosonic treatments neglect the 7/8 factor, they can still capture the qualitative thermodynamic behavior of neutrino backgrounds, with the induced error in energy density being about 12.5%, a known and easily correctable factor when needed for precision cosmology.

From the Stefan-Boltzmann law, the Neutrino “luminosity” of the Hubble sphere must should be given by:

$L_H=4\pi R_H^2\sigma T_{\nu }^4$(4)

where $T_{\nu }$ is the Neutrino background temperature of the Hubble sphere. This should likely at least be a good first approximation as Neutrinos moves with almost indistinguishable speed to the speed of light so they behave like heat radiation.

Further the Hawking temperature of a Planck mass black hole must be as shown by Haug and Wojnow [11] :

$T_{Hw,p}=\frac{\hslash g}{2\pi c{k}_b}=\frac{\hslash \frac{G{m}_p}{r_s^2}}{2\pi c{k}_b}=\frac{\hslash c}{8\pi l_p{k}_b}=\frac{T_p}{8\pi }.$(5)

We will assume Planck mass black holes are building blocks are linked to a hypothetical Planck mass particle that plays a central role in nature and cosmos, something discussed by Motz and Eppstein [27] as well as Haug [28] . The energy passing through a sphere with a radius equal to the Reissner-Nordström [29] [30] extremal solution or the Haug Spavieri [31] minimal solution of a Planck mass black hole must be:

$E=\frac{L_H}{4\pi r_h^2}.$(6)

where $r_h=\frac{GM}{c^2}=\frac{1}{2}{r}_s$ is the extremal black hole event horizon. The radiant flux absorbed by the Planck mass black hole cross-section $\pi r_h^2=\pi l_p^2$ is thus expressed as:

$4\pi l_p^2\sigma T_{Hw,p}^4=\pi {\left(2l_p\right)}^{2}E=4\pi l_p^2\frac{4\pi R_H^2\sigma T_{\nu }^4}{4\pi l_p^2}=4\pi R_H^2\sigma T_{\nu }^4$(7)

Solved for $T_{\nu }$ this gives:

$\begin{array}{l}{T}_{\nu }=T_{Hw,p}\sqrt{\frac{l_p}{R_H}}\\ T_{\nu }=\frac{T_p}{8\pi }\sqrt{\frac{l_p}{R_H}}=\frac{\hslash c}{8\pi k_b\sqrt{R_H{l}_p}}\approx 1.9336\text{K}\pm 0.0072\text{K}.\end{array}$(8)

which is very close to what is also estimated by the standard cosmological model, as seen in [25] [32] [33] , of about 1.95 K. We have used a $H_0=67.4\pm 0.5$ km/s/Mpc as given by the Particle Data Group (PDG) ¹ in their Astrophysical Constants and Parameters. We have naturally also taken into account the uncertanity in the Planck length and used the NIST CODATA value of $l_p=\left(1.616255\pm 0.000018\right)\times {10}^{-35}\text{m}$. However, unlike the CMB temperature [2] [3] [6] , the CνB temperature has not been measured, as neutrinos interact so weakly with other particles that it is hard to measure, however it could be that we in the future are able to measure the CνB background temperature also.

3. Further Discussion

Equation (8) above is likely related to metrics such the Haug Spavieri metric and the extremal solutions off Kerr [34] , and Kerr-Newman [35] [36] , as seen in [37] ). The Haug-Spavieri metric as well as the extremal Reissner-Nordstrom metric leads to a total mass-energy in the observable universe given by:

$M_u=\frac{c^2{R}_H}{2G}+\frac{c^3\text{Λ}{R}_H^2}{6G}=\frac{c^2{R}_H}{G}$(9)

The first part, $\frac{c^2{R}_H}{2G}$, is identical to the critical Friedmann mass. The second part is linked to relativistic gravitational energy and the cosmological constant (“Dark energy”), which has an exact value of $\text{Λ}=3{\left(\frac{H_t}{c}\right)}^2=\frac{3}{R_H^2}$. This latter part of the total mass represents relativistic gravitational energy, which can also be considered dark energy since only gravitational interactions from it are likely observable. We can also write the CνB temperature as:

$\begin{array}{c}{T}_{\nu }=\frac{\hslash c^3}{k_{b}8\pi G\sqrt{M_u{m}_p}}=\hslash \frac{c}{\sqrt{R_H{l}_p}}\frac{1}{k_{b}8\pi }=\frac{\hslash }{k_{b}8\pi \sqrt{t_h{t}_p}}\\ =\frac{\hslash \sqrt{H_0}}{k_{b}8\pi \sqrt{t_p}}\approx 1.9336\text{K}\pm 0.0072\text{K}.\end{array}$(10)

where $M_u$ represents the Haug-Spavieri universe mass as well as the Reissner-Nordström extremal universe mass [37] given by $M_u=2M_{cr}=\frac{c^2{R}_t}{G}$, where $R_t=ct$. This is equivalent to the critical Friedmann mass plus 50% dark energy, which essentially constitutes relativistic gravitational energy interacting with matter. The Haug-Spavieri universe adheres to $R_H=ct$ and also to the Haug extremal universe. This naturally implies that the formula is applicable to any cosmic epoch. However, further investigation is warranted, both mathematically and experimentally, as each metric and argument used must be carefully investigated before one hastily draws conclusions.

4. Neutrino Density and Neutrino Density Parameter

We further predict that the density of the CνB radiation must be based on Planck’s radiation law which should result in:

${\rho }_{\nu ,t}=\frac{1}{c^2}{\displaystyle {\int }_0^{\infty }hvn\left(v\right)\text{d}v}=\frac{a_b{T}_{\nu ,t}^4}{c^2}$(11)

where $a_b=\frac{4}{c}\sigma =\frac{{\pi }^2{k}_b^4}{15c^3{\hslash }^3}$ is the radiation constant.

Haug and Tatum [38] has demonstrated that the critical Friedmann density can be written as:

${\rho }_{cr,t}=\frac{3H_t^2}{8\pi G}=T_{cmb,t}^4\frac{23040\pi }{c^3}\sigma$(12)

where $\sigma =a_b\frac{c}{4}=\frac{{\pi }^2{k}_b^4}{60c^2{\hslash }^3}$ is the Stefan-Boltzmann constant and $a_b=\frac{4}{c}\sigma$ is the radiation constant and $T_{cmb,t}$ is the CMB temperature. The neutrino density parameter is defined as ${\Omega }_{\nu }=\frac{{\rho }_{\nu }}{{\rho }_{cr}}$ so we get:

$\begin{array}{l}{\Omega }_{\nu }=\frac{{\rho }_{\nu }}{{\rho }_{cr}}=\frac{\frac{\frac{4}{c}\sigma T_{\nu ,t}^4}{c^2}}{T_{cmb,t}^4\frac{23040\pi }{c^3}\sigma }\\ {\Omega }_{\nu }=\frac{T_{\nu ,t}^4}{T_{cmb,t}^{4}5760\pi }\\ {\Omega }_{\nu }=\frac{1}{23040\pi }\approx 1.38\times {10}^{-5}\end{array}$(13)

This means the Neutrino temperature after the neutrino decoupling can be written as (see also [39] )

$T_{\nu ,t}=\hslash \frac{c}{\sqrt{R_{H_t}{l}_p}}\frac{1}{k_{b}8\pi }=\sqrt[4]{\frac{3c^2{\Omega }_{\nu }}{8\pi G{a}_b}}\frac{1}{t^{1/2}}$(14)

If we input $t=\frac{1}{H_0}$ and are using a $H_0=66.9$ km/s/Mpc (see Haug and Tatum [40] for estimation of such a $H_0$) we get

$T_{\nu ,0}=\sqrt[4]{\frac{3c^2{\Omega }_{\nu }}{8\pi G{a}_b}}\frac{1}{{\left(\frac{1}{H_0}\right)}^{1/2}}\approx 1.93\text{K}$(15)

Which is very close to the assumed CνB temperature in standard theory also [25] , despite calculated from $R_{H_t}=ct$.

Equation (14) is not restricted only to a specific $R_{H_t}=ct$ model, but can be used to predict the CνB temperature also in other models that uses different assumptions and therefore have a different function or value for ${\Omega }_{\nu }$.

It is also interesting to note that we have:

$\frac{{\Omega }_{\nu }}{{\Omega }_{\gamma }}=\frac{{\rho }_{\nu }}{{\rho }_{\gamma }}=\frac{5760\pi }{23040\pi }=\frac{1}{4}$(16)

An interesting question is why the CνB density would be exactly one fourth of the CMB density. If this is correct also in the real universe, what would be the physical explanation for this? We do not yet have the answer, but we encourage others to research this as well.

5. Further Discussion

The derivations above are based on certain assumptions, such as the metric solutions of Reissner-Nordström or the Haug-Spavieri metric. While the CMB temperature has been measured with high precision and aligns well with recent developments in CMB predictions, the CνB temperature remains highly uncertain from an observational standpoint. Therefore, theoretical models regarding it should remain open to revision. The uncertainty primarily lies in ${\Omega }_{\nu }$; however, there is no such uncertainty in the model derived above, which yields an exact value of ${\Omega }_{\nu }=\frac{1}{23040\pi }$. Still, this result is based on assumptions that, with today’s technology, are difficult to test due to the challenges involved in measuring the CνB temperature.

An interesting question is why the predicted neutrino and CMB energy densities are so close in value. Specifically, why do we find that the CνB density is exactly a quarter of the CMB density: $\frac{{\rho }_{\nu }}{{\rho }_{\gamma }}=\frac{1}{4}$. Could the CνB be more closely related to the CMB than is commonly assumed? This and many other questions warrant further investigation. We have to be aware that we are working in a $R_{H_t}=ct$ model here. Also, the ratio between the CMB density and the critical density remains constant from CMB decoupling until today; it is ${\Omega }_{\gamma }=\frac{{\rho }_{\gamma }}{{\rho }_{cr}}=\frac{1}{5760\pi }$, see [41] . The physical explanation for this is likely either that the universe is a growing black hole, where the critical mass also increases linearly with $R_{H_t}$, or that the universe is an extremal black hole, where at least the apparent density changes as we observe matter farther away, see [42] .

In the standard model, the neutrino temperature is given by $T_{\nu }={\left(\frac{4}{11}\right)}^{1/3}{T}_{cmb}$, while in our model it is $T_{\nu }=\frac{1}{\sqrt{2}}{T}_{cmb}$. The difference in model predictions of the CνB temperature is about 1%. Unfortunately, to this day, the neutrino temperature has not been measured accurately enough to distinguish between the two models. However in the future one can hope this is possible.

6. Conclusion

We have suggested a formula that links the CνB temperature and the Hubble constant (Hubble radius and Hubble time), as well as actually also linking the CνB to the CMB temperature, as we, based on the derivations above, must have the following relation: $\frac{T_{\nu }}{T_{cmb}}=\frac{1}{\sqrt{2}}\approx 0.70711$ and further that $\frac{{\rho }_{\nu }}{{\rho }_{\gamma }}=\frac{1}{4}$, through the cosmic epochs of $R_{H_t}=ct$ cosmology. Furthermore, we have derived a CνB density parameter equal to ${\Omega }_{\nu }=\frac{1}{23040\pi }=\frac{1}{4}{\Omega }_{\gamma }$, valid for any time after neutrino decoupling inside $R_{H_t}=ct$ cosmology.

NOTES

¹ https://pdg.lbl.gov/2023/reviews/rpp2023-rev-astrophysical-constants.pdf

References

1. Zhou, Y. (2022) Methods of Discovering New Physics from the Cosmic Neutrino Background. Journal of Physics: Conference Series, 2381, Article 012079. >https://doi.org/10.1088/1742-6596/2381/1/012079

2. Fixsen, D.J., Kogut, A., Levin, S., Limon, M., Lubin, P., Mirel, P., et al. (2004) The Temperature of the Cosmic Microwave Background at 10 Ghz. The Astrophysical Journal, 612, 86-95. >https://doi.org/10.1086/421993

3. Fixsen, D.J. (2009) The Temperature of the Cosmic Microwave Background. The Astrophysical Journal, 707, 916-920. >https://doi.org/10.1088/0004-637x/707/2/916

4. Noterdaeme, P., Petitjean, P., Srianand, R., Ledoux, C. and López, S. (2011) The Evolution of the Cosmic Microwave Background Temperature. Astronomy&Astrophysics, 526, L7. >https://doi.org/10.1051/0004-6361/201016140

5. Dhal, S., Singh, S., Konar, K. and Paul, R.K. (2023) Calculation of Cosmic Microwave Background Radiation Parameters Using COBE/FIRAS Dataset. Experimental Astronomy, 56, 715-726. >https://doi.org/10.1007/s10686-023-09904-w

6. Dhal, S. and Paul, R.K. (2023) Investigation on CMB Monopole and Dipole Using Blackbody Radiation Inversion. Scientific Reports, 13, Article No. 3316. >https://doi.org/10.1038/s41598-023-30414-4

7. Tatum, E.T., Seshavatharam, U.V.S. and Lakshminarayana, S. (2015) The Basics of Flat Space Cosmology. International Journal of Astronomy and Astrophysics, 5, 116-124. >https://doi.org/10.4236/ijaa.2015.52015

8. Planck, M. (1899) Natuerliche Masseinheiten. Der Königlich Preussischen Akademie Der Wissenschaften. >https://www.biodiversitylibrary.org/item/93034#page/7/mode/1up

9. Planck, M. (1959) Vorlesungen über die Theorie der Wärmestrahlung. Dover Publication.

10. Friedmann, A. (1922) Über die krüng des raumes. Zeitschrift für Physik, 10, 377-386. >https://doi.org/10.1007/BF01332580

11. Haug, E.G. and Wojnow, S. (2024) How to Predict the Temperature of the CMB Directly Using the Hubble Parameter and the Planck Scale Using the Stefan-Boltzmann Law. Journal of Applied Mathematics and Physics, 12, 3552-3566. >https://doi.org/10.4236/jamp.2024.1210211

12. Haug, E.G. (2024) CMB, Hawking, Planck, and Hubble Scale Relations Consistent with Recent Quantization of General Relativity Theory. International Journal of Theoretical Physics, 63, Article No. 57. >https://doi.org/10.1007/s10773-024-05570-6

13. Haug, E.G. and Tatum, E.T. (2024) The Hawking Hubble Temperature as the Minimum Temperature, the Planck Temperature as the Maximum Temperature, and the CMB Temperature as Their Geometric Mean Temperature. Journal of Applied Mathematics and Physics, 12, 3328-3348. >https://doi.org/10.4236/jamp.2024.1210198

14. Haug, E.G. and Tatum, E.T. (2025) Friedmann Type Equations in Thermodynamic Form Lead to Much Tighter Constraints on the Critical Density of the Universe. Discover Space, 129, Article No. 6. >https://doi.org/10.1007/s11038-025-09566-y

15. Haug, E.G. (2025) The CMB Temperature Is Simply the Geometric Mean: of the Minimum and Maximum Temperature in the Hubble Sphere. Journal of Applied Mathematics and Physics, 13, 1085-1096. >https://doi.org/10.4236/jamp.2025.134056

16. Hawking, S.W. (1974) Black Hole Explosions? Nature, 248, 30-31. >https://doi.org/10.1038/248030a0

17. Haug, E.G. (2025) The Hubble Sphere as an Extremal Reissner-Nordström Black Hole Carnot Engine Operating at the CMB Temperature of: . Cambridge University Press. >https://doi.org/10.33774/coe-2025-w2dxp

18. Kaburaki, O. and Okamoto, I. (1991) Kerr Black Holes as a Carnot Engine. Physical Review D, 43, 340-345. >https://doi.org/10.1103/physrevd.43.340

19. Opatrný, T. and Richterek, L. (2011) Black Hole Heat Engine. American Journal of Physics, 80, 66-71. >https://doi.org/10.1119/1.3633692

20. Hendi, S.H., Eslam Panah, B., Panahiyan, S., Liu, H. and Meng, X.-H. (2018) Black Holes in Massive Gravity as Heat Engines. Physics Letters B, 781, 40-47. >https://doi.org/10.1016/j.physletb.2018.03.072

21. Wei, S. and Liu, Y. (2019) Charged AdS Black Hole Heat Engines. Nuclear Physics B, 946, Article 114700. >https://doi.org/10.1016/j.nuclphysb.2019.114700

22. Debnath, U. (2020) Thermodynamics of FRW Universe: Heat Engine. Physics Letters B, 810, Article 135807. >https://doi.org/10.1016/j.physletb.2020.135807

23. Debnath, U. (2022) General Thermodynamic Properties of FRW Universe and Heat Engine. Universe, 8, Article 400. >https://doi.org/10.3390/universe8080400

24. Kruglov, S.I. (2024) The Heat Engine of Magnetic Black Holes in AdS Space with Rational Nonlinear Electrodynamics. Canadian Journal of Physics, 946, Article 114700. >https://doi.org/10.1139/cjp-2024-0146

25. Faessler, A., Hodak, R., Kovalenko, S. and Simkovic, F. (2015) Search for the Cosmic Neutrino Background. Journal of Physics: Conference Series, 580, Article 012040. >https://doi.org/10.1088/1742-6596/580/1/012040

26. Muller, S., Beelen, A., Black, J.H., Curran, S.J., Horellou, C., Aalto, S., et al. (2013) A Precise and Accurate Determination of the Cosmic Microwave Background Temperature at . Astronomy&Astrophysics, 551, A109. >https://doi.org/10.1051/0004-6361/201220613

27. Motz, L. and Epstein, J. (1979) The Gravitational Charge as a Unifying Principle in Physics. Il Nuovo Cimento, 51, 88-113. >https://doi.org/10.1007/BF02822327

28. Haug, E.G. (2020) Collision-Space-Time: Unified Quantum Gravity. Physics Essays, 33, 46-78. >https://doi.org/10.4006/0836-1398-33.1.46

29. Reissner, H. (1916) Über die Eigengravitation des elektrischen Feldes nach der Einsteinschen Theorie. Annalen der Physik, 355, 106-120. >https://doi.org/10.1002/andp.19163550905

30. Nordström, G. (1918) On the Energy of the Gravitation Field in Einstein’s Theory. Koninklijke Nederlandsche Akademie van Wetenschappen Proceedings, 20, 1238-1245.

31. Haug, E.G. and Spavieri, G. (2023) Mass-Charge Metric in Curved Spacetime. International Journal of Theoretical Physics, 62, Article No. 248. >https://doi.org/10.1007/s10773-023-05503-9

32. Li, Y.F. (2017) Prospectives on Direct Detection of the Cosmic Neutrino Background. Journal of Physics: Conference Series, 888, Article 012146. >https://doi.org/10.1088/1742-6596/888/1/012146

33. Akita, K. and Yamaguchi, M. (2022) A Review of Neutrino Decoupling from the Early Universe to the Current Universe. Universe, 8, Article 552. >https://doi.org/10.3390/universe8110552

34. Kerr, R.P. (1963) Gravitational Field of a Spinning Mass as an Example of Algebraically Special Metrics. Physical Review Letters, 11, 237-238. >https://doi.org/10.1103/physrevlett.11.237

35. Newman, E.T. and Janis, A.I. (1965) Note on the Kerr Spinning-Particle Metric. Journal of Mathematical Physics, 6, 915-917. >https://doi.org/10.1063/1.1704350

36. Newman, E.T., Couch, E., Chinnapared, K., Exton, A., Prakash, A. and Torrence, R. (1965) Metric of a Rotating, Charged Mass. Journal of Mathematical Physics, 6, 918-919. >https://doi.org/10.1063/1.1704351

37. Haug, E.G. (2024) The Extremal Universe Exact Solution from Einstein’s Field Equation Gives the Cosmological Constant Directly. Journal of High Energy Physics, Gravitation and Cosmology, 10, 386-397. >https://doi.org/10.4236/jhepgc.2024.101027

38. Haug, E.G. and Tatum, E.T. (2024) Friedmann Type Equations in Thermodynamic Form Lead to Much Tighter Constraints on the Critical Density of the Universe. >https://www.preprints.org/manuscript/202403.1241/v2

39. Haug, E.G. (1948) The Gamow Temperature Formula, Adjusted for the Photon Density Parameter, Predicts the CMB Temperature Now and in the Past. Cambridge University Press. >https://doi.org/10.33774/coe-2025-jlff7

40. Haug, E.G. and Tatum, E.T. (2025) Solving the Hubble Tension Using the Pantheon-PlusSH0Es Supernova Database. Journal of Applied Mathematics and Physics, 13, 593-622. >https://doi.org/10.4236/jamp.2025.132033

41. Haug, E.G. (2025) An Exact CMB Photon Radiation Density of the Universe Derived from Cosmology. Cambridge University Press. U>https://doi.org/10.33774/coe-2025-jfg4t

42. Haug, E.G. (2025) The 14.6 Billion Age of the Universe in Black Hole Cosmology versus 13.8 Billon Years in Λ-CDM Cosmology, Dose It Explain the Early Galaxy Formation Problem? Journal of Applied Mathematics and Physics, 13, 1651-1664. >https://doi.org/10.4236/jamp.2025.135091