The primary purpose of this paper is to see how well a recently proposed new
model fits (a) the position of the baryon acoustic oscillations (BAO) features
observed in the large-scale distribution of galaxies and (b) the angular size
measured for the sound horizon due to BAO imprinted in the cosmic microwave
background (CMB) anisotropy. The new model is a hybrid model that combines the
tired light (TL) theory with a variant of the ${Lambda}CDM$ model in which the
cosmological constant is replaced with a covarying coupling constants’ (CCC)
parameter ${alpha}$. This model, dubbed the CCC+TL model, can fit the
supernovae type 1a Pantheon+ data as accurately as the ${Lambda}CDM$ model,
and also fit the angular size of cosmic dawn galaxies observed by the James
Webb Space Telescope, which is in tension with the ${Lambda}CDM$ model. The
results we obtained are $151.0 (pm5.1)$ Mpc for the absolute BAO scale at the
current epoch, and the angular size of the sound horizon
${theta}_{sh}=0.60{deg}$ matching Planck’s observations at the surface of the
last scattering when the baryon density is set to 100% of the matter density
and |${alpha}$| is increased by 5.6%. It remains to be seen if the new model
is consistent with the CMB power spectrum, the big-bang nucleosynthesis of
light elements, and other critical observations.

The primary purpose of this paper is to examine how well a recently proposed hybrid model, called the CCC+TL model, fits the observed baryon acoustic oscillations (BAO) features in the large-scale distribution of galaxies and the angular size measured for the sound horizon in the cosmic microwave background (CMB) anisotropy. This model combines the tired light (TL) theory with a variant of the ${Lambda}CDM$ model, where the cosmological constant is replaced with a covarying coupling constants’ (CCC) parameter ${alpha}$.

The CCC+TL model has shown that it can accurately fit the supernovae type 1a Pantheon+ data as well as the angular size of cosmic dawn galaxies observed by the James Webb Space Telescope. These results are in tension with the ${Lambda}CDM$ model. Specifically, the absolute BAO scale at the current epoch is estimated to be 1.0 (pm5.1)$ Mpc, and the angular size of the sound horizon is ${theta}_{sh}=0.60{deg}$, matching Planck’s observations. These values are obtained when the baryon density is set to 100% of the matter density and |${alpha}$| is increased by 5.6%.

However, it remains to be seen if the CCC+TL model is consistent with other critical observations, such as the CMB power spectrum and big-bang nucleosynthesis of light elements. Future research should focus on testing the model against these observations to validate its overall consistency and accuracy.

Future Roadmap

Based on the results and conclusions presented in this paper, there are several potential challenges and opportunities on the horizon:

  • Further testing against the CMB power spectrum: The CCC+TL model needs to be examined in the context of the CMB power spectrum to determine if it can accurately explain the observed anisotropy in the cosmic microwave background radiation. This will require detailed analysis and comparison with existing data.
  • Verification through big-bang nucleosynthesis: The model’s consistency with the big-bang nucleosynthesis of light elements needs to be investigated. This process involves examining the production of light elements in the early universe and comparing it to observational data. If the CCC+TL model can accurately explain these observations, it would strengthen its validity.
  • Exploration of other critical observations: In addition to the two mentioned above, there may be other crucial observations that can provide further evidence for or against the CCC+TL model. Researchers should explore these observations and conduct detailed analyses to determine the model’s overall consistency and its ability to explain various cosmological phenomena.
  • Refinement and improvement of the CCC+TL model: As the CCC+TL model is still in its early stages, there is room for refinement and improvement. Future research should focus on tweaking and optimizing the model to enhance its accuracy and compatibility with various cosmological measurements.

Overall, while the CCC+TL model shows promise in fitting observed data related to baryon acoustic oscillations and cosmic dawn galaxies, further investigations are necessary to validate its compatibility with other critical observations. By addressing these challenges and exploring new opportunities, researchers can advance our understanding of the universe’s large-scale structure and potentially uncover new insights into cosmology.

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