Vol. 24 No. 3 (2025): Mapana Journal of Sciences
Research Articles

An accelerating flat universe with an inverse square variation of the equation of state parameter with scale factor.

  • Sivakumar Chandrahasan
Sivakumar Chandrahasan
Maharaja's Collge affiliated to M G University, Kottayam

Published 2025-09-29

Keywords

  • Accelerating expansion, Hubble parameter, Pressure parameter, Dark energy.

Copyright (c) 2025

Creative Commons License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Abstract

The omega parameter in the equation of state of the cosmic fluid that varies inversely as the square of the scale factor is a possibility to explain the evolution of our flat universe, presently expanding with an increasing acceleration under the negative pressure of dark energy. The model is an attempt to demonstrate the shift of the universe from a phase of decelerating expansion rate to an acceleration using a simple equation of state consistent with the cosmological observations by introducing an effective omega parameter in the equation of state for the cosmic fluid which comprises of radiation, matter and dark energy.

References

  1. References
  2. . P. J. E. Peebles, Principles of Physical Cosmology, Princeton University Press, Princeton, 1993.
  3. . Dodelson, S., Modern Cosmology, Academic Press, 2003.
  4. . A. G. Riess et al, Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant, Astron. J. 116: 1009–1038, 1998.
  5. . S. Perlmutter et al, Measurements of Omega and Lambda from 42 High-Redshift Supernovae, Astrophys. J. 517: 565–586, 1999.
  6. . N. Aghanim et al (Planck Collaboration), Planck 2018 results. VI. Cosmological parameters, Astron. Astrophys. 641: A6, 2020.
  7. . S. Alam et al, Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory, Phys. Rev. D 103: 083533, 2021.
  8. . E. Tomasetti et al, Constraints on dynamical dark energy models using the latest data, Astron. Astrophys. 679: A96, 2023.
  9. . R. Jimenez et al, Updated observational constraints on H(z) measurements and the Hubble tension, JCAP 11: 047, 2023.
  10. . M. Li et al, Dark energy, Commun. Theor. Phys. 56: 525–604, 2011.
  11. . G. Gu et al, Observational signatures of dynamical DE models, Res. Astron. Astrophys. 24: 065001, 2024.
  12. . T. Padmanabhan, Cosmological constant—the weight of the vacuum, Phys. Rept. 380: 235–320, 2003.
  13. . W. Giare et al, A cosmographic analysis of DE evolution, JCAP 10: 035, 2024.
  14. . S. Weinberg, The cosmological constant problem, Rev. Mod. Phys. 61: 1–23, 1989.
  15. . J. Martin, Everything you always wanted to know about the cosmological constant problem (but were afraid to ask), Comptes Rendus Physique 13: 566–665, 2012.
  16. . I. Zlatev, L. Wang and P. J. Steinhardt, Quintessence, Cosmic Coincidence, and the Cosmological Constant, Phys. Rev. Lett. 82: 896–899, 1999.
  17. . E. J. Copeland, M. Sami and S. Tsujikawa, Dynamics of dark energy, Int. J. Mod. Phys. D 15: 1753–1936, 2006.
  18. . L. K. Duchaniya et al, Generalized holographic Ricci dark energy models, Phys. Dark Univ. 44: 101461, 2024.
  19. . S. Nojiri and S. D. Odintsov, Unified cosmic history in modified gravity, Phys. Rept. 505: 59–144, 2011.
  20. . E. Di Valentino et al, In the realm of the Hubble tension, Class. Quantum Grav. 38: 153001, 2021.
  21. . A. G. Riess et al, A comprehensive measurement of the local value of the Hubble constant, Astrophys. J. Lett. 934: L7, 2022.
  22. . E. Di Valentino et al, In the realm of the Hubble tension, Class. Quantum Grav. 38: 153001, 2021.
  23. . L. Verde, T. Treu and A. G. Riess, Tensions between the early and late Universe, Nat. Astron. 3: 891–895, 2019.
  24. . S. Pan and S. Chakraborty, A cosmographic analysis of various parametrizations of dark energy, Int. J. Mod. Phys. D 28: 1950151, 2019.
  25. . W. Yang et al, Interacting dark energy models after Planck 2018, JCAP 01: 047, 2024.
  26. . B. J. Barros et al, Observational constraints on interacting models, Eur. Phys. J. C 84: 276, 2024.
  27. . S. Capozziello et al, Modified gravity approaches and cosmological observations, Symmetry 15: 65, 2023.
  28. . S. Weinberg, Gravitation and Cosmology: Principles and applications of GTR, Wiley, New York, 1972.
  29. . V. Mukhanov, Physical Foundations of Cosmology, Cambridge University Press, Cambridge, 2005.
  30. . B. Wang et al, Reconstructing quintessence and tachyon potentials from recent data, Phys. Rev. D 108: 043523, 2023.
  31. . S. D. Odintsov and V. K. Oikonomou, Singular cosmology from generalized entropy formalism, Phys. Rev. D 107: 083519, 2023.
  32. . Ö. Akarsu et al, Probing dynamical DE with cosmographic methods, Phys. Rev. D 107: 123503, 2023.
  33. . Y. Tada and T. Terada, Primordial black holes from the inflating curvaton, Phys. Rev. D 109: L121305, 2024.
  34. M. Cortes and A. R. Liddle, Bayesian model comparison of cosmologies with dynamical DE, JCAP 12: 007, 2024.
  35. . L. A. Escamilla et al, Holographic dark energy in f(R,T) gravity, JCAP 2024: 091, 2024.
  36. . A. C. Alfano et al, Late-time cosmological dynamics of generalized holographic models, Phys. Dark Univ. 42: 101298, 2023.
  37. . H. Wang and Y. S. Piao, Cosmological constant problem in inflationary models, Phys. Rev. D 105: 083504, 2022.
  38. . F. B. M. dos Santos, Observational constraints on interacting quintessence models, JCAP 07: 064, 2023.
  39. . K. Bamba, S. Capozziello, S. Nojiri and S. D. Odintsov, Dark energy cosmology: the equivalent description via different theoretical models and cosmography tests, Astrophys. Space Sci. 342: 155–228, 2012.
  40. . J. Niu et al, Cosmic growth index in modified gravity, Astrophys. J. 972: 14, 2024.
  41. . K. V. Berghaus et al, Planck constraints on extra relativistic species and DE models, Phys. Rev. D 110: 103524, 2024.
  42. . M. Lucca et al, Dark sector interactions and early dark energy, Phys. Rev. D 108: 063501, 2023.
  43. . T. Clifton et al, Modified gravity and cosmology, Phys. Rept. 513: 1–189, 2012.
  44. . Y. F. Cai et al, f(T) teleparallel gravity and cosmology, Rept. Prog. Phys. 79: 106901, 2016.
  45. . M. Krssak et al, Teleparallel theories of gravity: illuminating a fully invariant approach, Class. Quantum Grav. 36: 183001, 2019.
  46. . S. Bahamonde et al, Teleparallel gravity: From theory to cosmology, Phys. Rept. 775–777: 1–122, 2018.
  47. . S. D. Odintsov et al, A novel exponential f(R) gravity model for dark energy, Eur. Phys. J. C 85: 298, 2025.
  48. . M. C. B. Abdalla et al, Dark energy and dark matter interactions: theoretical models and observational constraints, Phys. Dark Univ. 38: 101256, 2022.
  49. . N. Aghanim et al, Planck 2018 results. VI. Cosmological parameters, Astron. Astrophys. 641: A6, 2020.
  50. . P. M. Garnavich et al, Supernova Limits on the Cosmic Equation of State, Astrophys. J. 509: 74–79, 1998.
  51. . C. Sivakumar, M. V. John and K. Babu Joseph, Stochastic evolution of cosmological parameters in the early universe, Pramana 56: 477–466, 2001.