Is Our Universe Accelerating Dynamics Fractional Order?

2015 ◽  
Author(s):  
Caibin Zeng ◽  
YangQuan Chen ◽  
Igor Podlubny
Keyword(s):  
Fundamental Solution ◽  
Fractional Order ◽  
Exponential Function ◽  
Dynamical Equation ◽  
Hubble Constant ◽  
Expansion Rate ◽  
Fractional Dynamics ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

In this paper, a fractional dynamics approach is used to characterize the observed accelerating expansion of the universe. We claim that the evolution of accelerating expansion obeys an α-exponential function, which is the fundamental solution of linear fractional order dynamical equation. We find that the Hubble constant is 67.8807, 68.2546, and 67.9119 for all redshift z < 1.5, z < 1, and z < 0.1 based on the dataset collected by the Supernova Cosmology Project. Furthermore, we verify that the expansion rate of our universe is speeding up and actually obeys a Mittag-Leffler law.

scholarly journals Universe opacity and Type Ia supernova dimming

2019 ◽  
Vol 489 (1) ◽  
pp. L63-L68 ◽  
Author(s):  
Václav Vavryčuk
Keyword(s):  
Cold Dark Matter ◽  
Hubble Constant ◽  
Light Extinction ◽  
Universe Model ◽  
Type Ia Supernova ◽  
Accelerating Expansion ◽  
Λcdm Model ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
The Universe

ABSTRACT In this paper, I revoke a debate about an origin of Type Ia supernova (SN Ia) dimming. I argue that except for a commonly accepted accelerating expansion of the Universe, a conceivable alternative for explaining this observation is universe opacity caused by light extinction by intergalactic dust, even though it is commonly assumed that this effect is negligible. Using data of the Union2.1 SN Ia compilation, I find that the standard Λ cold dark matter (ΛCDM) model and the opaque universe model fit the SN Ia measurements at redshifts z < 1.4 comparably well. The optimum solution for the opaque universe model is characterized by the B-band intergalactic opacity $\lambda _{B} = 0.10 \pm 0.03 \, \mathrm{Gpc}^{-1}$ and the Hubble constant $H_0 = 68.0 \pm 2.5 \, \mathrm{km\, s^{-1}\, Mpc^{-1}}$. The intergalactic opacity is higher than that obtained from independent observations but still within acceptable limits. This result emphasizes that the issue of the accelerating expansion of the Universe as the origin of the SN Ia dimming is not yet definitely resolved. Obviously, the opaque universe model as an alternative to the ΛCDM model is attractive, because it avoids puzzles and controversies associated with dark energy and the accelerating expansion.

scholarly journals Kinetic studies relating to the accelerated expansion of the Universe

2021 ◽  
Author(s):  
Wei Zhang ◽  
Cheng Deng
Keyword(s):  
General Relativity ◽  
Hubble Constant ◽  
Kinetic Studies ◽  
Physical Significance ◽  
Accelerated Expansion ◽  
Newtonian Mechanics ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Masses ◽  
The Universe

Abstract After taking into account the mass loss of galaxies and stars at the cosmic scale, the speed and acceleration of the accelerating expansion of the Universe are derived from general relativity and Newtonian mechanics, as respectively. The physical significance of the Hubble constant is proved to be the average of the masses ejected per second per unit mass in the observed range, and it is shown that the accelerated expansion of the universe doesn’t require dark energy

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

Spectral redshift does not imply an accelerating expansion of the universe

2013 ◽  
Vol 26 (3) ◽  
pp. 452-456
Author(s):  
Dimitrios Laskaroudis
Keyword(s):  
Red Shift ◽  
Gravity Center ◽  
Erroneous Conclusion ◽  
Minimum Value ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Creation ◽  
The Universe ◽  
Spectral Redshift

Spectra received from faraway heavenly objects display a redshift. In this paper, it is shown that there is a moment in time tx at which time the red shift has its minimum value. This moment is different for every object and depends on the distance of the emission from the gravity center of the object. So from the time of the creation of the object and up until the time tx, the red shift is decreasing and from that moment on it is increasing while the object, due to the expansion of the universe, continues to move away with decreasing speed. Due to the change of the red shift from decreasing to increasing, it is possible to observe faraway supernovas with a brightness that is less than what is expected. This observation leads to the erroneous conclusion that the universe is expanding with acceleration. Finally, an explanation is given to the fact that the number of quasars is decreasing in time.

scholarly journals ACCELERATING EXPANSION OF THE UNIVERSE MAY BE CAUSED BY INHOMOGENEITIES

2006 ◽  
Vol 21 (14) ◽  
pp. 1117-1125 ◽  
Author(s):  
GYULA BENE ◽  
VIKTOR CZINNER ◽  
MÁTYÁS VASÚTH
Keyword(s):  
Friedmann Equation ◽  
Additional Term ◽  
Density Fluctuations ◽  
Einstein Equations ◽  
The Other ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Homogeneous Approximation ◽  
Spatial Inhomogeneities

We point out that, due to the nonlinearity of the Einstein equations, a homogeneous approximation in cosmology leads to the appearance of an additional term in the Friedmann equation. This new term is associated with the spatial inhomogeneities of the metric and can be expressed in terms of density fluctuations. Although it is not constant, it decays much slower (as t-2/3) than the other terms (like density) which decrease as t-2. The presence of the new term leads to a correction in the scale factor that is proportional to t2and may give account of the recently observed accelerating expansion of the universe without introducing a cosmological constant.

scholarly journals Resolving the Hubble Constant Discrepancy: Revisiting the Effect of Local Environments

2020 ◽  
Vol 2 (1) ◽  
pp. 94-96
Author(s):  
Dennis M Doren ◽  
James Harasymiw
Keyword(s):  
Mass Density ◽  
Hubble Constant ◽  
Local Environment ◽  
Expansion Rate ◽  
Local Environments ◽  
The Universe

Studies have found two differing sets of figures for the Hubble constant without clear direction for resolution of that difference. This article offers a direction for reconciling the measurement discrepancy. Research is reviewed and theory is described that indicate the resolution may be found in revisiting how the degree of mass in local environments affects computations. The idea that the expansion rate of the universe is invariably uniform is discounted, to be replaced by a range of figures depending on the mass density of the local environment underlying the measurement.

Swampland criteria and cosmological behavior of Tsallis holographic dark energy in Bianchi -III Universe

2020 ◽  
Vol 17 (07) ◽  
pp. 2050098 ◽  
Author(s):  
Umesh Kumar Sharma ◽  
Shikha Srivastava ◽  
A. Beesham
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Accelerating Universe ◽  
Accelerating Expansion ◽  
Bianchi Iii ◽  
Expansion Of The Universe ◽  
Hubble Horizon ◽  
The Universe ◽  
Universe Evolution

In this paper, a new form of dark energy, known as Tsallis holographic dark energy (THDE), with IR cutoff as Hubble horizon proposed by Tavayef et al. Tsallis holographic dark energy, Phys. Lett. B 781 (2018) 195 has been explored in Bianchi-III model with the matter. By taking the time subordinate deceleration parameter, the solution of Einstein’s field equation is found. The Universe evolution from earlier decelerated to the current accelerated phase is exhibited by the deceleration parameter acquired in the THDE model. It can be seen that the derived THDE model is related to an accelerating Universe with quintessence ([Formula: see text]). The squared sound speed [Formula: see text] also suggests that the THDE model is classically stable at present. In addition, the quintessence phase of the THDE model is analyzed with swampland conjecture to reformulate the accelerating expansion of the Universe.

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