scholarly journals Shedding Light On An Undiscovered Aspect That Perfectly Mimics Cosmic Acceleration

2021 ◽  
Author(s):  
Karan R. Takkhi
Keyword(s):  
Scale Factor ◽  
Cosmic Acceleration ◽  
Expansion Rate ◽  
Distance Modulus ◽  
Speed Of Light ◽  
Local Structures ◽  
Time Relationship ◽  
Distance Relationship ◽  
Superluminal Expansion ◽  
The Universe

Abstract The comparison of redshift-distance relationship for high and low-redshift supernovae revealed the surprising transition of Universe’s expansion from deceleration to acceleration. As compared to local supernovae, remote supernovae are further away than expected. The expansion rate obtained for local supernovae is higher with low redshifts as compared to the expansion rate obtained for remote supernovae with high redshifts. Since observed redshifts provide an estimate of recession/expansion velocities in order to determine the expansion rate (km s-1 Mpc-1) of the Universe, therefore, it is very disturbing to find that low recession velocities (just 1% of speed of light) indicate a faster rate of expansion (acceleration), whereas high recession velocities (60% of speed of light) indicate a slower rate of expansion (deceleration). In this paper I unravel an undiscovered aspect that perfectly mimics cosmic acceleration. Rather than “cosmic deceleration that preceded the current epoch of cosmic acceleration”, I show that “consecutive expansion epochs of the Universe that preceded the current expansion epoch were responsible for placing remote supernovae further away than expected”. As a consequence of consecutive expansion, expansion began for remote structures in preceding expansion epochs before it did for local structures in the current expansion epoch; remote supernovae are therefore not only further away than expected, but they also happen to yield a slower rate of expansion even with “superluminal expansion velocities”. As a result of consecutive expansion, preceding expansion epochs appear to be decelerating as compared to the expansion epoch that succeeds them. The results obtained have been confirmed by plotting velocity-distance relationship, expansion rate vs. time relationship, expansion factor vs. time relationship, scale factor vs. time relationship, scale factor vs. distance relationship, distance-redshift relationship, and distance modulus vs. redshift relationship, moreover, deceleration parameter (q0) is also found to be negative (q0 < 0).

scholarly journals The Flatness Problem and the Variable Physical Constants

Galaxies ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 77
Author(s):  
Rajendra P. Gupta
Keyword(s):  
Hubble Constant ◽  
Physical Constant ◽  
Big Bang ◽  
Scale Factor ◽  
Radius Of Curvature ◽  
Distance Modulus ◽  
Speed Of Light ◽  
Curvature Term ◽  
The Universe ◽  
Flatness Problem

We have used the varying physical constant approach to resolve the flatness problem in cosmology. Friedmann equations are modified to include the variability of speed of light, gravitational constant, cosmological constant, and the curvature constant. The continuity equation obtained with such modifications includes the scale factor-dependent cosmological term as well as the curvature term, along with the standard energy-momentum term. The result is that as the scale factor tends to zero (i.e., as the Big Bang is approached), the universe becomes strongly curved rather than flatter and flatter in the standard cosmology. We have used the supernovae 1a redshift versus distance modulus data to determine the curvature variation parameter of the new model, which yields a better fit to the data than the standard ΛCDM model. The universe is found to be an open type with a radius of curvature R c = 1.64   ( 1 + z ) − 3.3 c 0 / H 0 , where z is the redshift, c 0 is the current speed of light, and H 0 is the Hubble constant.

scholarly journals The Flatness Problem and the Varying Physical Constants

2019 ◽  
Author(s):  
Rajendra P. Gupta
Keyword(s):  
Hubble Constant ◽  
Physical Constant ◽  
Big Bang ◽  
Scale Factor ◽  
Radius Of Curvature ◽  
Distance Modulus ◽  
Speed Of Light ◽  
Curvature Term ◽  
The Universe ◽  
Flatness Problem

We have used the varying physical constant approach to resolve the flatness problem in cosmology. Friedmann equations are modified to include variability of speed of light, gravitational constant, cosmological constant and the curvature constant. The continuity equation obtained with such modifications includes scale factor dependent cosmological term as well as the curvature term along with the standard energy-momentum term. The result is that as the scale factor tends to zero (i.e. as the big-bang is approached) the universe becomes strongly curved rather than flatter and flatter in the standard cosmology. We have used the supernovae 1a redshift versus distance modulus data to determine the curvature variation parameter of the new model, which yields a better fit to the data than the standard &Lambda;CDM model. The universe is found to be open type with radius of curvature Rc = 1.64 (1+z)-3.3 c0/H0, where z is the redshift, c0 is the current speed of light and H0 is the Hubble constant.

scholarly journals Shedding Light On An Undiscovered Aspect That Perfectly Mimics Cosmic Acceleration

2022 ◽  
Author(s):  
Karan R. Takkhi
Keyword(s):  
Gamma Ray ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Cosmic Acceleration ◽  
Expansion Rate ◽  
Type Ia Supernovae ◽  
Time Relationship ◽  
Type Ia ◽  
Ia Supernovae ◽  
Distance Relationship

Abstract The comparison of redshift-distance relationship for high and low-redshift supernovae revealed the surprising transition of the Universe’s expansion from deceleration to acceleration. As compared to local supernovae, remote supernovae appear 10% to 25% dimmer as they are further away than expected. The expansion rate obtained for local supernovae is higher with low redshifts as compared to the expansion rate obtained for remote supernovae with high redshifts. Since observed redshifts in an expanding Universe provide an estimate of recession velocities, therefore, it is very disturbing to find that low recession velocities (just 1% of speed of light) indicate a faster rate of expansion (acceleration), whereas high recession velocities (60% of speed of light) indicate a slower rate of expansion (deceleration). In this paper, I unravel an undiscovered aspect that perfectly mimics cosmic acceleration. Rather than “cosmic deceleration that preceded the current epoch of cosmic acceleration”, I show in this paper, that “consecutive expansion epochs of the Universe that preceded the current epoch of cosmic expansion” were responsible for placing remote supernovae further away than expected. As a consequence of consecutive expansion, expansion began for remote structures in preceding expansion epochs before it did for local structures in the current (or more recent) expansion epoch; remote supernovae, quasars, and gamma-ray bursts are therefore not only further away than expected, but they also happen to yield a slower rate of expansion, thereby suggesting their deceleration even with “superluminal expansion”. As a result of consecutive expansion, preceding expansion epochs appear to be decelerating as compared to the expansion epoch that succeeds them. The analysis is based on the redshift-distance relationship plotted for 580 type Ia supernovae from the Supernova Cosmology Project, 7 additional high-redshift type Ia supernovae discovered through the Advanced Camera for Surveys on the Hubble Space Telescope from the Great Observatories Origins Deep Survey Treasury program, and 1 additional very high-redshift type Ia supernova discovered with Wide Field and Planetary Camera 2 on the Hubble Space Telescope. The results obtained by the High-Z Supernova Search Team through observations of type Ia supernovae have also been analysed. Studies incorporating quasars and gamma-ray bursts to determine how the expansion of the Universe has changed over time have been taken into consideration as well. The results obtained in this paper have been confirmed by plotting velocity-distance relationship, expansion rate vs. time relationship, expansion factor vs. time relationship, scale factor vs. time relationship, scale factor vs. distance relationship, distance-redshift relationship, and distance modulus vs. redshift relationship, moreover, the deceleration parameter (q0) is also found to be negative (q0 < 0).

scholarly journals Model-independent cosmic acceleration and redshift-dependent intrinsic luminosity in type-Ia supernovae

2019 ◽  
Vol 625 ◽  
pp. A15 ◽  
Author(s):  
I. Tutusaus ◽  
B. Lamine ◽  
A. Blanchard
Keyword(s):  
Spline Interpolation ◽  
High Redshift ◽  
Cosmic Acceleration ◽  
Expansion Rate ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe ◽  
Intrinsic Luminosity

Context. The cosmological concordance model (ΛCDM) is the current standard model in cosmology thanks to its ability to reproduce the observations. The first observational evidence for this model appeared roughly 20 years ago from the type-Ia supernovae (SNIa) Hubble diagram from two different groups. However, there has been some debate in the literature concerning the statistical treatment of SNIa, and their stature as proof of cosmic acceleration. Aims. In this paper we relax the standard assumption that SNIa intrinsic luminosity is independent of redshift, and examine whether it may have an impact on our cosmological knowledge and more precisely on the accelerated nature of the expansion of the universe. Methods. To maximise the scope of this study, we do not specify a given cosmological model, but we reconstruct the expansion rate of the universe through a cubic spline interpolation fitting the observations of the different cosmological probes: SNIa, baryon acoustic oscillations (BAO), and the high-redshift information from the cosmic microwave background (CMB). Results. We show that when SNIa intrinsic luminosity is not allowed to vary as a function of redshift, cosmic acceleration is definitely proven in a model-independent approach. However, allowing for redshift dependence, a nonaccelerated reconstruction of the expansion rate is able to fit, at the same level of ΛCDM, the combination of SNIa and BAO data, both treating the BAO standard ruler rd as a free parameter (not entering on the physics governing the BAO), and adding the recently published prior from CMB observations. We further extend the analysis by including the CMB data. In this case we also consider a third way to combine the different probes by explicitly computing rd from the physics of the early universe, and we show that a nonaccelerated reconstruction is able to nicely fit this combination of low- and high-redshift data. We also check that this reconstruction is compatible with the latest measurements of the growth rate of matter perturbations. We finally show that the value of the Hubble constant (H0) predicted by this reconstruction is in tension with model-independent measurements. Conclusions. We present a model-independent reconstruction of a nonaccelerated expansion rate of the universe that is able to fit all the main background cosmological probes nicely. However, the predicted value of H0 is in tension with recent direct measurements. Our analysis points out that a final reliable and consensual value for H0 is critical to definitively prove cosmic acceleration in a model-independent way.

Bulk viscosity in Friedmann universe with a varying speed of light described by modified equation of state

2015 ◽  
Vol 12 (10) ◽  
pp. 1550126
Author(s):  
G. S. Khadekar ◽  
Arti Ghogre
Keyword(s):  
Equation Of State ◽  
Bulk Viscosity ◽  
Scale Factor ◽  
Special Choice ◽  
Speed Of Light ◽  
Dependent Parameter ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Modified Equation ◽  
Universe Evolution

We solve the Freidmann equations by considering a universe media as a bulk viscosity described by a modified equation of state (EOS) of the form p = (γ - 1)ρc2 + Λ(t). A completely integrable dynamical equation to the scale factor is obtained and gives out the exact solution by assuming that the time-dependent parameter Λ and the bulk viscosity are linear combination of two and three terms, respectively and is expressed as: [Formula: see text] and [Formula: see text], where R is a scale factor and Λ0, Λ1, ζ0, ζ1, ζ2, are constants. For a special choice of the parameters, we discuss the acceleration expansion of the universe evolution and future singularities in the framework of variable speed of light (VSL) theory.

scholarly journals Analytical Solution to FRW Metric with Variable Speed of Light

2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Gabriel W. Joseph ◽  
Terkaa Victor Targema ◽  
M. O. Kanu
Keyword(s):  
Hubble Parameter ◽  
Reference Frames ◽  
Einstein Field Equation ◽  
State Parameter ◽  
Scale Factor ◽  
General Covariance ◽  
Speed Of Light ◽  
Cosmological Time ◽  
Age Of The Universe ◽  
The Universe

<p>According to the principle of general covariance, the laws of physics are the same in all reference frames. The controversial theory of the Varying Speed of Light (VSL) contradicts the principle of general covariance. Fortunately the VLS theory explains some crucial issues in cosmology such as Lorentz variance, biometric theories, locally Lorentz variance, cosmological constant problem, horizon<em> </em>and flatness<em> </em>problems. Also, recent astronomical observations from quasar show that the fine structural constant depends on redshift and therefore, varies with cosmological time. In other to harness this fascinating and published knowledge, two models where used in this work.  1. Cosmology with variables c; here the Friedmann-Robertson-Walker (FRW) is used in the Einstein field equation with variable c and Λ terms to obtain the scale factor, which shows the continuous exponential expansion of the universe. 2. Variation of the speed of light as a function of the scale factor of the universe; here we obtained: a good approximation to estimate the current age of the universe. The scale factor of the universe depends its content given by the equation of state parameter ω. We obtained the deceleration parameter in terms of the Hubble parameter. We arrived at a conclusion that the universe was decelerating at ω = 1, accelerating at ω = 1/3 and the Hubble parameter diverges at the beginning and end of the universe.</p>

scholarly journals Expanding Confusion: Common Misconceptions of Cosmological Horizons and the Superluminal Expansion of the Universe

2004 ◽  
Vol 21 (1) ◽  
pp. 97-109 ◽  
Author(s):  
Tamara M. Davis ◽  
Charles H. Lineweaver
Keyword(s):  
General Relativity ◽  
Confidence Level ◽  
Speed Of Light ◽  
Observable Universe ◽  
Expansion Of The Universe ◽  
Superluminal Expansion ◽  
The Universe ◽  
Recession Velocity ◽  
Common Misconceptions ◽  
Rule Out

AbstractWe use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard ΛCDM cosmology we point out confusions regarding the particle horizon, the event horizon, the ‘observable universe’ and the Hubble sphere (distance at which recession velocity = c). We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests. Attempts to restrict recession velocities to less than the speed of light require a special relativistic interpretation of cosmological redshifts. We analyze apparent magnitudes of supernovae and observationally rule out the special relativistic Doppler interpretation of cosmological redshifts at a confidence level of 23σ.

ANALYTICAL CONSIDERATIONS ABOUT THE COSMOLOGICAL CONSTANT AND DARK ENERGY

2009 ◽  
Vol 24 (28n29) ◽  
pp. 5427-5444 ◽  
Author(s):  
EVERTON M. C. ABREU ◽  
LEONARDO P. G. DE ASSIS ◽  
CARLOS M. L. DOS REIS
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Large Scale ◽  
Weak Interactions ◽  
High Redshift ◽  
Fundamental Constant ◽  
Scale Factor ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
The Universe

The accelerated expansion of the universe has now been confirmed by several independent observations including those of high redshift type Ia supernovae, and the cosmic microwave background combined with the large scale structure of the universe. Another way of presenting this kinematic property of the universe is to postulate the existence of a new and exotic entity, with negative pressure, the dark energy (DE). In spite of observationally well established, no single theoretical model provides an entirely compelling framework within which cosmic acceleration or DE can be understood. At present all existing observational data are in agreement with the simplest possibility that the cosmological constant be a candidate for DE. This case is internally self-consistent and noncontradictory. The extreme smallness of the cosmological constant expressed in either Planck, or even atomic units means only that its origin is not related to strong, electromagnetic, and weak interactions. Although in this case DE reduces to only a single fundamental constant we still have no derivation from any underlying quantum field theory for its small value. From the principles of quantum cosmologies, for example, it is possible to obtain the reason for an inverse-square law for the cosmological constant with no conflict with observations. Despite the fact that this general expression is well known, in this work we introduce families of analytical solutions for the scale factor different from the current literature. The knowledge of the scale factor behavior might shed some light on these questions mentioned above since the entire evolution of a homogeneous isotropic universe is contained in the scale factor. We use different parameters for these solutions and with these parameters we establish a connection with the equation of state for different DE scenarios.

scholarly journals SNe data analysis in variable speed of light cosmologies without cosmological constant

2014 ◽  
Vol 29 (24) ◽  
pp. 1450103 ◽  
Author(s):  
Pengfei Zhang ◽  
Xinhe Meng
Keyword(s):  
Dark Energy ◽  
Scale Factor ◽  
Model Parameters ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Data Sets ◽  
Variable Speed ◽  
Speed Of Light ◽  
Type Ia ◽  
Ia Supernovae

In this work, we aim to show the possibilities of the variable speed of light (VSL) theory in explaining the type Ia supernovae (SNe) observations without introducing dark energy. The speed of light is assumed to be scale factor-dependent, which is the most popular assumption in VSL theory. We show the modified calculation of the distance modulus and the validity of the redshift-scale factor relation in VSL theory. Three different models of VSL are tested SNe data-sets with proper constraints on the model parameters. The comparison of the three models and flat ΛCDM in distance modulus is showed. Some basic problems and the difficulties of the confirmation of the VSL theory are also discussed.

scholarly journals IMPLICATIONS OF A QUANTUM MECHANICAL TREATMENT OF THE UNIVERSE

1998 ◽  
Vol 13 (05) ◽  
pp. 347-351 ◽  
Author(s):  
MURAT ÖZER
Keyword(s):  
Quantum Mechanics ◽  
Wave Packet ◽  
Early Universe ◽  
Mechanical Treatment ◽  
Correspondence Principle ◽  
Scale Factor ◽  
Quantum Mechanical ◽  
Quantum Mechanical Treatment ◽  
The Standard Model ◽  
The Universe

We attempt to treat the very early Universe according to quantum mechanics. Identifying the scale factor of the Universe with the width of the wave packet associated with it, we show that there cannot be an initial singularity and that the Universe expands. Invoking the correspondence principle, we obtain the scale factor of the Universe and demonstrate that the causality problem of the standard model is solved.

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