Modern Cosmology, an Amuse-Gueule

Schmitz, Kai

doi:10.1007/978-3-031-05625-3_3

Cited by 3 publications

(1 citation statement)

References 115 publications

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“…There appears to be a significant discrepancy, ≥ 5σ (Riess et al 2022;de Jaeger et al 2022) between the value of the Hubble constant as determined by early universe measurements (Planck Collaboration et al 2020;Fields et al 2020;Abbott et al 2018) and late universe measurements (Riess et al 2021;Freedman et al 2019;Birrer & Treu 2021;Wong et al 2020;Schombert et al 2020;Kourkchi et al 2020;Soltis et al 2021;Blakeslee et al 2021;Kim et al 2020;Pesce et al 2020;Abbott et al 2021;De Felice et al 2021;Hu & Wang 2022;Perivolaropoulos & Skara 2022a;Khetan et al 2021;Huang et al 2020;Mörtsell et al 2022;Wang et al 2023). For reviews see Perivolaropoulos & Skara (2022b); Di Valentino et al (2021); Verde et al (2019); Shah et al (2021) and Schmitz (2022) for a non-technical comprehensive review. There has been many attempts to explain this discrepancy by modifying ΛCDM such as Rezazadeh et al (2022); Addison (2021); Knox & Millea (2020); Kovács et al (2020); Schöneberg et al (2019); Buen-Abad et al (2023); Murgia et al (2021); Vagnozzi (2020); Abdalla et al (2022), just to mention a few.…”

Section: Introductionmentioning

confidence: 99%

Cosmological Gravitational Redshift and Hubble Tension

III

2023

Preprint

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For almost a century since its first measurement by Hubble in 1929 the value of the Hubble constant, H, has been the subject of intense debate. In the last few years a new dimension has been added to this debate because there appears to be a significant discrepancy between the values of H derived from present-day universe (cepheids, supernova, lensed quasars, tip of the red giant branch), which are minimally dependent on cosmological theory and those derived from early universe observations (cosmic microwave background and baryon acoustic oscillations), which are based on the standard cosmological theory, $\Lambda CDM$, whereby $\Lambda CDM$ in turn is based on the assumption that the universe is expanding. This discrepancy is known as Hubble tension. We resolve the Hubble tension by introducing a universe which is govern by the Taub-NUT solution to the field equations of general relativity. The Taub-NUT universe is not expanding. In this universe the observed cosmological redshift is due to the gravitational redshift associated with the Taub-Nut solution, which we refer to as cosmological gravitational redshift. Time dilation in this stationary universe has the same dependency on redshift, that generally has been seen as proof that space is expanding.

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Section: Introductionmentioning

confidence: 99%

Cosmological Gravitational Redshift and Hubble Tension

III

2023

Preprint

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Temporal evolution of cosmological density perturbations of the Bose–Einstein condensate dark matter

Mondal,

Choudhuri

2024

Eur. Phys. J. C

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Dark matter is assumed to be composed of scalar boson particles that form Bose–Einstein condensate during the cosmic evolution of the Universe when the temperature of the dark matter is below the critical temperature $$T_{cr}$$ T cr . At around a redshift $$z\sim 1200$$ z ∼ 1200 , the normal dark matter converted to Bose–Einstein condensate dark matter through a first-order phase transition and continued to complete the condensation process for nearly $$10^6$$ 10 6 years, until then, both phases coexist. In this manuscript, considering Bose–Einstein condensate dark matter as a Gross–Pitaevskii–Poisson system, we study the time evolution of density contrast of Bose–Einstein condensate dark matter using cosmological linear perturbation theory following previous works on the subject. The evolution equation contains quantum pressure due to Heisenberg’s uncertainty principle and self-interaction pressure terms. We solve the temporal density contrast equation of Bose–Einstein condensate dark matter analytically for both the Thomas-Fermi limit and the non-interacting case where the expansion rule follows similarly to that of the Einstein–de Sitter Universe. In addition, we also numerically analyze the temporal nature of the evolution of density contrast of Bose–Einstein condensate dark matter for the complete equation without applying any approximation. We find that the Bose–Einstein condensate model of dark matter could modify the temporal nature of density contrast evolution due to the presence of self-interaction and quantum pressure terms, which shows significant differences with respect to the conventional standard cold dark matter, and successfully solves the small-scale problems in the context of cosmological structure formation.

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Hubble Tension: The Evidence of New Physics

Wang

2023

Universe

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The ΛCDM model provides a good fit to most astronomical observations but harbors large areas of phenomenology and ignorance. With the improvements in the precision and number of observations, discrepancies between key cosmological parameters of this model have emerged. Among them, the most notable tension is the 4σ to 6σ deviation between the Hubble constant (H0) estimations measured by the local distance ladder and the cosmic microwave background (CMB) measurement. In this review, we revisit the H0 tension based on the latest research and sort out evidence from solutions to this tension that might imply new physics beyond the ΛCDM model. The evidence leans more towards modifying the late-time universe.

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Modern Cosmology, an Amuse-Gueule

Cited by 3 publications

References 115 publications

Cosmological Gravitational Redshift and Hubble Tension

Cosmological Gravitational Redshift and Hubble Tension

Temporal evolution of cosmological density perturbations of the Bose–Einstein condensate dark matter

Hubble Tension: The Evidence of New Physics

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