scholarly journals Hydrodynamic attractor in a Hubble expansion

2021 ◽  
Vol 104 (5) ◽  
Author(s):  
Zhiwei Du ◽  
Xu-Guang Huang ◽  
Hidetoshi Taya
Keyword(s):  
Hubble Expansion

scholarly journals Experimental Evidence in Support of the Possibility That the Local Space of Earth Is Confined

2019 ◽  
Vol 11 (4) ◽  
pp. 7
Author(s):  
Shlomo Barak ◽  
Arie Zigler ◽  
Jenya Papeer
Keyword(s):  
Experimental Evidence ◽  
Laser Pulses ◽  
Correlation Technique ◽  
Space Flights ◽  
Hubble Expansion ◽  
Global Space ◽  
Auto Correlation ◽  
Local Space ◽  
The Times ◽  
Synchronization Scheme

We have measured variations in the times of flight of 25fsec laser pulses, along a given distance from A to B, in different directions in space. Flights from A to B are termed one-way versus two-way - from A to B and back to A. The isotropy obtained, despite the motion of Earth in global space, supports the possibility that the local space of Earth, and probably that of other stars, is confined - captured inside the sphere of the star. To maintain space continuity, despite this confinement, space must necessarily be an elastic fluid, as Einstein, for a different reason, concluded in 1939. In addition, we wonder if this confinement of a local space in a star or galaxy explains its non-participation in the Hubble expansion of space. Our experiment used an auto-correlation technique that dispels the need for clocks, which in one-way measurements require a problematic synchronization scheme.

scholarly journals Do supernovae indicate an accelerating universe?

2021 ◽  
Author(s):  
Roya Mohayaee ◽  
Mohamed Rameez ◽  
Subir Sarkar
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Bulk Flow ◽  
Expansion Rate ◽  
Accelerated Expansion ◽  
Accelerating Universe ◽  
Acoustic Oscillations ◽  
Independent Evidence ◽  
Peculiar Velocity ◽  
Hubble Expansion

AbstractIn the late 1990’s, observations of two directionally-skewed samples of, in total, 93 Type Ia supernovae were analysed in the framework of the Friedmann–Lemaître–Robertson–Walker (FLRW) cosmology. Assuming these to be ‘standard(isable) candles’ it was inferred that the Hubble expansion rate is accelerating as if driven by a positive Cosmological Constant $$\varLambda $$ Λ in Einstein’s theory of gravity. This is still the only direct evidence for the ‘dark energy’ that is the dominant component of today’s standard $$\varLambda $$ Λ CDM cosmological model. Other data such as baryon acoustic oscillations (BAO) in the large-scale distribution of galaxies, temperature fluctuations in the cosmic microwave background (CMB), measurement of stellar ages, the rate of growth of structure, etc are all ‘concordant’ with this model but do not provide independent evidence for accelerated expansion. The recent discussions about whether the inferred acceleration is real rests on analysis of a larger sample of 740 SNe Ia which shows that these are not quite standard candles, and more importantly highlights the ‘corrections’ that are applied to analyse the data in the FLRW framework. The latter holds in the reference frame in which the CMB is isotropic, whereas observations are carried out in our heliocentric frame in which the CMB has a large dipole anisotropy. This is assumed to be of kinematic origin i.e. due to our non-Hubble motion driven by local inhomogeneity in the matter distribution which has grown under gravity from primordial density perturbations traced by the CMB fluctuations. The $$\varLambda $$ Λ CDM model predicts how this peculiar velocity should fall off as the averaging scale is raised and the universe becomes sensibly homogeneous. However observations of the local ‘bulk flow’ are inconsistent with this expectation and convergence to the CMB frame is not seen. Moreover, the kinematic interpretation implies a corresponding dipole in the sky distribution of high redshift quasars, which is rejected by observations at $$4.9\sigma $$ 4.9 σ . Hence the peculiar velocity corrections employed in supernova cosmology are inconsistent and discontinuous within the data. The acceleration of the Hubble expansion rate is in fact anisotropic at $$3.9\sigma $$ 3.9 σ and aligned with the bulk flow. Thus dark energy could be an artefact of analysing data assuming that we are idealised observers in an FLRW universe, when in fact the real universe is inhomogeneous and anisotropic out to distances large enough to impact on cosmological analyses.

scholarly journals ΛCDM periodic cosmology

2020 ◽  
Vol 494 (2) ◽  
pp. 2183-2190
Author(s):  
Stéphane Fay
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Hubble Expansion ◽  
Background Data ◽  
Periodic Models ◽  
Cosmic Microwave Background Data

ABSTRACT We examine the possibility that Universe expansion be made of some Λ-cold dark matter (ΛCDM) expansions repeating periodically, separated by some inflation- and radiation-dominated phases. This so-called ΛCDM periodic cosmology is motivated by the possibility that inflation and the present phase of accelerated expansion be due to the same dark energy. Then, in a phase space showing the variation of matter density parameter Ωm with respect to this of the radiation Ωr, the curve Ωm(Ωr) looks like a closed trajectory that Universe could run through forever. In this case, the end of the expansion acceleration of the ΛCDM phase is the beginning of a new inflation phase. We show that such a scenario implies the coupling of matter and/or radiation to dark energy. We consider the simplest of these ΛCDM periodic models i.e. a vacuum energy coupled to radiation. From matter domination phase to today, it behaves like a ΛCDM model, then followed by an inflation phase. But a sudden and fast decay of the dark energy into radiation periodically ends the expansion acceleration. This leads to a radiation-dominated Universe preceding a new ΛCDM type expansion. The model is constrained with Markov Chain Monte Carlo simulations using supernovae, Hubble expansion, Baryon Acoustic Oscillations (BAO), and cosmic microwave background data and fits the data as well as the ΛCDM one.

Effect upon universal order of Hubble expansion

2012 ◽  
Vol 391 (1-2) ◽  
pp. 410-413 ◽  
Author(s):  
B.R. Frieden ◽  
A. Plastino ◽  
A.R. Plastino
Keyword(s):  
Hubble Expansion ◽  
Universal Order

OBSERVATIONAL COSMOLOGY 2004: WHAT THE DATA SAY ABOUT DARK ENERGY AND THE CONTENTS OF THE UNIVERSE

2005 ◽  
Vol 20 (14) ◽  
pp. 2931-2942
Author(s):  
JOSEPH FOWLER
Keyword(s):  
Dark Energy ◽  
Background Radiation ◽  
Current Data ◽  
Observational Cosmology ◽  
Microwave Background ◽  
Hubble Expansion ◽  
Microwave Background Radiation ◽  
Expansion Of The Universe ◽  
Cosmological Data ◽  
The Universe

The latest cosmological data point to a model of the universe that is self-consistent but deeply weird. It seems that most matter in our universe is non-baryonic and hidden from direct view. Meanwhile, a repulsive "dark energy" causes the expansion of the universe to proceed at an accelerating rate. Sources of current data include studies of the distribution of matter in the universe, the anisotropies of the cosmic microwave background radiation, and the Hubble expansion law as probed by distant supernovae. In the near future, we can hope that measurements like these will begin to illuminate the nature of dark energy, starting with the question of whether it behaves like a cosmological constant or shows a more complicated evolution.

scholarly journals VISCOUS MODIFIED COSMIC CHAPLYGIN GAS COSMOLOGY

2013 ◽  
Vol 22 (09) ◽  
pp. 1350061 ◽  
Author(s):  
B. POURHASSAN
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Nonlinear Equation ◽  
Observational Data ◽  
Function Method ◽  
Chaplygin Gas ◽  
Time Dependent ◽  
Dark Energy Density ◽  
Hubble Expansion ◽  
Exponential Function Method

In this paper, we construct viscous modified cosmic Chaplygin gas as a model of dark energy. We use exponential function method to solve nonlinear equation and obtain time-dependent dark energy density. Then, we discuss Hubble expansion parameter and scale factor and fix them by using observational data. Effect of viscosity to the evolution of Universe is investigated. We also investigate stability of this theory.

scholarly journals Hubble expansion and structure formation in time varying vacuum models

2009 ◽  
Vol 80 (8) ◽  
Author(s):  
Spyros Basilakos ◽  
Manolis Plionis ◽  
Joan Solà
Keyword(s):  
Structure Formation ◽  
Time Varying ◽  
Hubble Expansion
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