# Alternative ideas in cosmology

18 Mar 2022-International Journal of Modern Physics D (International Journal of Modern Physics D)-Vol. 31, Iss: 08

TL;DR: Some remarkable examples of alternative cosmological theories are reviewed here, ranging from a compilation of variations on the standard model through the more distant quasi-steady-state cosmology, plasma cosmology or universe models as a hypersphere, to the most exotic cases including static models as discussed by the authors .

Abstract: Some remarkable examples of alternative cosmological theories are reviewed here, ranging from a compilation of variations on the Standard Model through the more distant quasi-steady-state cosmology, plasma cosmology, or universe models as a hypersphere, to the most exotic cases including static models. The present-day standard model of cosmology, Lambda-CDM, gives us a representation of a cosmos whose dynamics is dominated by gravity with a finite lifetime, large scale homogeneity, expansion and a hot initial state, together with other dark elements necessary to avoid certain inconsistencies with observations. There are however some models with characteristics that are close to those of the standard model but differing in some minor aspects: different considerations on CP violation, inflation, number of neutrino species, quark-hadron phase transition, baryonic or non-baryonic dark-matter, dark energy, nucleosynthesis scenarios, large-scale structure formation scenarios; or major variations like a inhomogeneous universe, Cold Big Bang, varying physical constants or gravity law, zero-active mass (also called `R_h=ct'), Milne, and cyclical models. At the most extreme distance from the standard model, the static models, a non-cosmological redshift includes `tired-light' hypotheses, which assume that the photon loses energy owing to an intrinsic property or an interaction with matter or light as it travels some distance, or other non-standard ideas. Our impression is that none of the alternative models has acquired the same level of development as Lambda-CDM in offering explanations of available cosmological observations. One should not, however, judge any theory in terms of the number of observations that it can successfully explain (ad hoc in many cases) given the much lower level of development of the alternative ones.

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TL;DR: In this article , the authors compare the results of the standard ΛCDM cosmological model and some static cosmology models, including Zwicky's "tired-light" model.

Abstract: The James Webb Space Telescope (JWST), which has recently become operational, is capable of detecting objects at record-breaking redshifts, z≳15. This is a crucial advance for observational cosmology, as at these redshifts the differences between alternative cosmological models manifest themselves in the most obvious way. In recent years, some observational hints have emerged indicating that the Standard Cosmological Model could require correcting. One of these hints is related to the discovery of remote galaxies whose redshifts correspond to the very young Universe (less than one billion years after the Big Bang) but which are similar to nearby galaxies. The issue is that such galaxies in the early Universe do not have enough time to evolve into something similar to the late-Universe galaxies. JWST observations of high-redshift objects are expected to shed light on the origin of this issue. Here we provide results on performing the “angular diameter—redshift” cosmological test for the first JWST observation data. We compare this result with predictions of the standard ΛCDM cosmological model and some static cosmological models, including Zwicky’s “tired-light” model. The latter is currently assumed to be ruled out by observations. We challenge this assumption and show that a static model can provide a natural and straightforward way of solving the puzzle of the well-evolved galaxies and better agreements with the results of the JWST “angular diameter—redshift” test at high redshifts than the correcting evolution model within the ΛCDM framework. We discuss several cosmological tests that will be important for further research on the possibility of revising the expanding Universe paradigm.

1 citations

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TL;DR: In this paper , the authors proposed a mechanism to increase the number of relativistic degrees of freedom in the CMB power spectrum using spin-0, spin-1/2, and spin 1 dark matter operators.

Abstract: Abstract The Hubble constant inferred from the 6-parameter fit to the CMB power spectrum conflicts with the value obtained from direct measurements via type Ia supernova and Cepheids observations. We write down effective operators involving spin-0, spin-1/2, and spin-1 dark matter that lead to the relativistic production of dark matter particles at early times, and consequently lead to an increase in the number of relativistic degrees of freedom. This mechanism which is amenable to CMB, BBN, and structure formation observables can sufficiently raise the value of the Hubble constant derived from CMB and reconcile local and CMB probes of the Hubble constant. This mechanism alone increases $$H_0$$ H 0 up to $$70\, \textrm{km}\, \textrm{s}^{-1} \, \textrm{Mpc}^{-1}$$ 70 km s - 1 Mpc - 1 , and with the help of a Phantom-like cosmology, reach $$H_0 \simeq $$ H 0 ≃ 71–73 $$\textrm{km} \,\textrm{s}^{-1} \textrm{Mpc}^{-1}$$ km s - 1 Mpc - 1 . Lastly, we outline the region of parameter space which reproduces $$H_0 \simeq $$ H 0 ≃ 71–73 $$\textrm{km} \,\textrm{s}^{-1} \, \textrm{Mpc}^{-1}$$ km s - 1 Mpc - 1 while obeying all relevant constraints.

1 citations

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TL;DR: An unexplained acceleration on the order of 10−8 cm s−2, which is close to cH, where c is the speed of light and H is the Hubble constant, is detected in gravitationally bound systems of different scales, from the solar system to clusters of galaxies as discussed by the authors .

Abstract: An unexplained acceleration on the order of 10–8 cm s–2, which is close to cH,
where c is the speed of light and H is the Hubble constant, is detected in
gravitationally bound systems of different scales, from the solar system to clusters of
galaxies. We found that any test body located inside a fractal structure with fractal
dimension D = 2 experiences acceleration of the same order and confirmed the previous
work that photons propagating through this structure decrease the frequency owing to
gravitational redshift. The acceleration can be directed against the movement of the
test body. The fractal distribution of the matter should be at scales of at least
hundreds of megaparsecs to a few gigaparsecs for the existence of this acceleration.

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23 Mar 2023TL;DR: In this paper , a bijective analysis is confirmed, the expansion of universal space has never been directly observed, and this assumption is unproven thus far, and even if the universal space is assumed to expand, the gravitational redshift cannot be assumed to be proof of the expansion.

Abstract: A bijective analysis is confirming, the expansion of universal space has never been directly observed, and this assumption is unproven thus far. The measurement of the gravitational redshift, which was confirmed using the Mossbauer experiment, proves only the gravitational redshift and nothing more because there is no causality between the gravitational redshift and hypothetical expansion. Thus, even if the universal space is assumed to expand, the gravitational redshift cannot be assumed to be proof of the expansion. In addition, the Doppler effect was never observed in an expanding space; thus, the claim that the cosmological redshift is partially caused by the Doppler effect, which is caused by the expansion of space, is an unproven assumption. Furthermore, the discovery of cosmic microwave background (CMB) radiation simply proves that the radiation is emitted by the entire universal space, but does not prove the existence of a recombination period. In stationary cosmology, every element in the model has a corresponding element in physical reality that is observed and measured. The stationary cosmology model is related to the real universe by a bijective function of set theory.

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TL;DR: In this paper , a comprehensive survival strategy based on ectogenesis, the raising of embryos in artificial uterus systems, was proposed to ensure human survival and procreativity on future Earths.

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Nabila Aghanim

^{1}, Yashar Akrami^{2}, Yashar Akrami^{3}, Yashar Akrami^{4}+229 more•Institutions (70)TL;DR: In this article, the authors present cosmological parameter results from the full-mission Planck measurements of the cosmic microwave background (CMB) anisotropies, combining information from the temperature and polarization maps and the lensing reconstruction.

Abstract: We present cosmological parameter results from the ﬁnal full-mission Planck measurements of the cosmic microwave background (CMB) anisotropies, combining information from the temperature and polarization maps and the lensing reconstruction Compared to the 2015 results, improved measurements of large-scale polarization allow the reionization optical depth to be measured with higher precision, leading to signiﬁcant gains in the precision of other correlated parameters Improved modelling of the small-scale polarization leads to more robust constraints on manyparameters,withresidualmodellinguncertaintiesestimatedtoaﬀectthemonlyatthe05σlevelWeﬁndgoodconsistencywiththestandard spatially-ﬂat6-parameter ΛCDMcosmologyhavingapower-lawspectrumofadiabaticscalarperturbations(denoted“base ΛCDM”inthispaper), from polarization, temperature, and lensing, separately and in combination A combined analysis gives dark matter density Ωch2 = 0120±0001, baryon density Ωbh2 = 00224±00001, scalar spectral index ns = 0965±0004, and optical depth τ = 0054±0007 (in this abstract we quote 68% conﬁdence regions on measured parameters and 95% on upper limits) The angular acoustic scale is measured to 003% precision, with 100θ∗ = 10411±00003Theseresultsareonlyweaklydependentonthecosmologicalmodelandremainstable,withsomewhatincreasederrors, in many commonly considered extensions Assuming the base-ΛCDM cosmology, the inferred (model-dependent) late-Universe parameters are: HubbleconstantH0 = (674±05)kms−1Mpc−1;matterdensityparameterΩm = 0315±0007;andmatterﬂuctuationamplitudeσ8 = 0811±0006 We ﬁnd no compelling evidence for extensions to the base-ΛCDM model Combining with baryon acoustic oscillation (BAO) measurements (and consideringsingle-parameterextensions)weconstraintheeﬀectiveextrarelativisticdegreesoffreedomtobe Neﬀ = 299±017,inagreementwith the Standard Model prediction Neﬀ = 3046, and ﬁnd that the neutrino mass is tightly constrained toPmν < 012 eV The CMB spectra continue to prefer higher lensing amplitudesthan predicted in base ΛCDM at over 2σ, which pulls some parameters that aﬀect thelensing amplitude away from the ΛCDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAOdataThejointconstraintwithBAOmeasurementsonspatialcurvatureisconsistentwithaﬂatuniverse, ΩK = 0001±0002Alsocombining with Type Ia supernovae (SNe), the dark-energy equation of state parameter is measured to be w0 = −103±003, consistent with a cosmological constant We ﬁnd no evidence for deviations from a purely power-law primordial spectrum, and combining with data from BAO, BICEP2, and Keck Array data, we place a limit on the tensor-to-scalar ratio r0002 < 006 Standard big-bang nucleosynthesis predictions for the helium and deuterium abundances for the base-ΛCDM cosmology are in excellent agreement with observations The Planck base-ΛCDM results are in good agreement with BAO, SNe, and some galaxy lensing observations, but in slight tension with the Dark Energy Survey’s combined-probe results including galaxy clustering (which prefers lower ﬂuctuation amplitudes or matter density parameters), and in signiﬁcant, 36σ, tension with local measurements of the Hubble constant (which prefer a higher value) Simple model extensions that can partially resolve these tensions are not favoured by the Planck data

4,688 citations

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TL;DR: In this article, the authors present a review of the most important aspects of the different classes of modified gravity theories, including higher-order curvature invariants and metric affine.

Abstract: Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology, and astrophysics. Among numerous alternatives to Einstein's theory of gravity, theories that include higher-order curvature invariants, and specifically the particular class of $f(R)$ theories, have a long history. In the last five years there has been a new stimulus for their study, leading to a number of interesting results. Here $f(R)$ theories of gravity are reviewed in an attempt to comprehensively present their most important aspects and cover the largest possible portion of the relevant literature. All known formalisms are presented---metric, Palatini, and metric affine---and the following topics are discussed: motivation; actions, field equations, and theoretical aspects; equivalence with other theories; cosmological aspects and constraints; viability criteria; and astrophysical applications.

4,027 citations

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TL;DR: A comprehensive survey of recent work on modified theories of gravity and their cosmological consequences can be found in this article, where the authors provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a selfcontained, comprehensive and up-to-date introduction to the subject as a whole.

3,674 citations

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TL;DR: In this article, the authors examine the possibility that a significant component of the energy density of the universe has an equation of state different from that of matter, radiation, or cosmological constant.

Abstract: We examine the possibility that a significant component of the energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ( $\ensuremath{\Lambda}$). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this component alters cosmic evolution in a way that fits current observations well. Unlike $\ensuremath{\Lambda}$, it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.

3,400 citations