scholarly journals A New Measurement of the Geometry of Space

1987 ◽  
Vol 124 ◽  
pp. 217-221
Author(s):  
Edwin D. Loh
Keyword(s):  
Big Bang ◽  
Recent Measurement ◽  
Density Parameter ◽  
Confidence Limits ◽  
Dimensionless Form ◽  
Primordial Nucleosynthesis ◽  
Geometrical Effects ◽  
Age Of The Universe ◽  
The Universe ◽  
Inflationary Models

This paper discusses the recent measurement of the number of galaxies vs. redshift and flux and presents new results pertaining to the two dimensionless geometrical quantities that describe the geometry of the conventional big-bang cosmology, the density parameter Ω and the dimensionless form λ = Λ/(3H02) of the cosmological constant. In contrast to the classical redshift-magnitude test as applied to the brightest galaxies in clusters, this new method is able to separate the effects of evolution from geometrical effects and is therefore able to measure the geometry of space. The 95% confidence limits are Ω - λ = 0.9−0 5+0 7 and −1.5 < Ω + λ < 7.1. The principal conclusions are these: (1) For both λ = 0 and inflationary models of the universe, this measurement and primordial nucleosynthesis imply a large density of nonbaryonic matter. (2) Hubble's constant H0 and the age of the universe τ are constrained by 0.60 < H0τ < 0.88 (95% confidence).

scholarly journals COSMOLOGICAL CONSTRAINTS FOR THE COSMIC DEFECT THEORY

2011 ◽  
Vol 20 (06) ◽  
pp. 1039-1051 ◽  
Author(s):  
NINFA RADICELLA ◽  
MAURO SERENO ◽  
ANGELO TARTAGLIA
Keyword(s):  
Large Scale ◽  
Hubble Constant ◽  
Big Bang ◽  
Nuclear Species ◽  
Type Ia ◽  
Species Abundances ◽  
Age Of The Universe ◽  
Ia Supernovae ◽  
The Big Bang ◽  
The Universe

The cosmic defect theory has been confronted with four observational constraints: primordial nuclear species abundances emerging from the big bang nucleosynthesis; large scale structure formation in the Universe; cosmic microwave background acoustic scale; luminosity distances of type Ia supernovae. The test has been based on a statistical analysis of the a posteriori probabilities for three parameters of the theory. The result has been quite satisfactory and such that the performance of the theory is not distinguishable from that of the ΛCDM theory. The use of the optimal values of the parameters for the calculation of the Hubble constant and the age of the Universe confirms the compatibility of the cosmic defect approach with observations.

Construction of neutrino models with non-vanishing θ13 and leptogenesis

2015 ◽  
Vol 93 (12) ◽  
pp. 1561-1565
Author(s):  
Ng. K. Francis
Keyword(s):  
Neutrino Mass ◽  
Big Bang ◽  
Baryon Asymmetry ◽  
Daya Bay ◽  
Mass Model ◽  
Big Bang Nucleosynthesis ◽  
Great Discovery ◽  
Neutrino Mass Models ◽  
The Universe ◽  
Inflationary Models

We construct the neutrino mass models with non-vanishing θ13 and estimate the baryon asymmetry of the universe and subsequently derive the constraints on the inflaton mass and the reheating temperature after inflation. The great discovery of this decade, the detection of Higgs boson of mass 126 GeV and nonzero θ13, makes leptogenesis all the more exciting. Besides, the neutrino mass model is compatible with inflaton mass 1010–1013 GeV corresponding to reheating temperature TR ∼ 105–107 GeV to overcome the gravitino constraint in supersymmetry and big bang nucleosynthesis. When Daya Bay data θ13 ≈ 9° is included in the model, τ predominates over e and μ contributions, which are indeed a good sign. It is shown that neutrino mass models for a successful leptogenesis can be accommodated for a variety of inflationary models with a rather wide ranging inflationary scale.

scholarly journals Dynamic of the Accelerated Expansion of the Universe in the DGP Model

2011 ◽  
Vol 21 (3) ◽  
pp. 253 ◽  
Author(s):  
Vo Quoc Phong
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Cold Dark Matter ◽  
Growth Index ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Type Ia ◽  
Age Of The Universe ◽  
The Universe

According to experimental data of SNe Ia (Supernovae type Ia), we will discuss in detial dynamics of the DGP model and introduce a simple parametrization of matter $\omega$, in order to analyze scenarios of the expanding universe and the evolution of the scale factor. We find that the dimensionless matter density parameter at the present epoch $\Omega^0_m=0.3$, the age of the universe $t_0= 12.48$ Gyr, $\frac{a}{a_0}=-2.4e^{\frac{-t}{25.56}}+2.45$. The next we study the linear growth of matter perturbations, and we assume a definition of the growth rate, $f \equiv \frac{dln\delta}{dlna}$. As many authors for many years, we have been using a good approximation to the growth rate $f \approx \Omega^{\gamma(z)}_m$, we also find that the best fit of the growth index, $\gamma(z)\approx 0.687 - \frac{40.67}{1 + e^{1.7. (4.48 + z)}}$, or $\gamma(z)= 0.667 + 0.033z$ when $z\ll1$. We also compare the age of the universe and the growth index with other models and experimental data. We can see that the DGP model describes the cosmic acceleration as well as other models that usually refers to dark energy and Cold Dark Matter (CDM).

scholarly journals Photon Creation in the Universe and Primordial Nucleosynthesis

2000 ◽  
Vol 198 ◽  
pp. 113-115
Author(s):  
J.A. S. Lima ◽  
J. S. Alcaniz ◽  
J. Santos ◽  
R. Silva
Keyword(s):  
Irreversible Process ◽  
Big Bang ◽  
Radiation Temperature ◽  
Thermodynamic Approach ◽  
Phenomenological Parameter ◽  
Primordial Nucleosynthesis ◽  
Stringent Constraint ◽  
The Universe ◽  
Creation Rate

In hot big bang cosmologies, the irreversible process of continous photon creation may phenomenologically be described through a thermodynamic approach. In these models, the radiation temperature law depends on a phenomenological parameter β which is closely related to the photon creation rate. It is shown that a stringent constraint on the value of this parameter is imposed from primordial nucleosynthesis.

Age of the universe and the density parameter

1994 ◽  
Vol 33 (9) ◽  
pp. 1933-1934
Author(s):  
Marcelo Samuel Berman ◽  
Fernando de Mello Gomide
Keyword(s):  
Density Parameter ◽  
Age Of The Universe ◽  
The Universe

scholarly journals The flatness problem and the age of the Universe

2020 ◽  
Vol 495 (4) ◽  
pp. 3571-3575
Author(s):  
Phillip Helbig
Keyword(s):  
Early Universe ◽  
Time Scale ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Fine Tuning ◽  
Density Parameter ◽  
Age Of The Universe ◽  
Short Time ◽  
The Universe ◽  
Flatness Problem

ABSTRACT Several authors have made claims, none of which has been rebutted, that the flatness problem, as formulated by Dicke and Peebles, is not really a problem but rather a misunderstanding. Nevertheless, the flatness problem is still widely perceived to be real. Most of the arguments against the idea of a flatness problem are based on the change with time of the density parameter Ω and normalized cosmological constant λ and, since the Hubble constant H is not considered, are independent of time-scale. An independent claim is that fine-tuning is required in order to produce a Universe which neither collapsed after a short time nor expanded so quickly that no structure formation could take place. I show that this claim does not imply that fine-tuning of the basic cosmological parameters is necessary, in part for similar reasons as in the more restricted flatness problem and in part due to an incorrect application of the idea of perturbing the early Universe in a gedankenexperiment; I discuss some typical pitfalls of the latter.

The Alabama Insert

Think ◽  
2002 ◽  
Vol 1 (1) ◽  
pp. 7-20
Author(s):  
Richard Dawkins
Keyword(s):  
Public Schools ◽  
Life Forms ◽  
Big Bang ◽  
Human Beings ◽  
Text Book ◽  
Gallup Poll ◽  
The Bible ◽  
Age Of The Universe ◽  
The Big Bang ◽  
The Universe

Creationists believe that the Biblical account of the creation of the universe is literally true. God brought into existence the Earth and all its life forms in just six days. According to creationists, this event took place less than ten thousand years ago (they base their calculation of the age of the universe on the number of generations listed in the Bible).Creationists have succeeded in persuading large swathes of the general public that their theory is at least as scientifically respectable as the Big Bang/evolution alternative. A recent Gallup poll indicated that about 45% of US citizens currently believe that God created human beings ‘pretty much in [their] present form at one time or another within the last 10,000 years’.Two states, Arkansas and Louisiana, have even passed ‘balanced treatment’ laws requiring that creationism be taught alongside evolution in all state public schools. It was in Auburn, Alabama, shortly after that state required that a piece of paper be pasted into every biology school text book explaining why evolution is merely a ‘theory’ — and a highly questionable theory at that — that Richard Dawkins delivered the impromptu speech which forms the basis of the following.

COSMOLOGICAL CONSEQUENCES OF A MODEL WITH A GENERALIZED COSMOLOGICAL CONSTANT

1999 ◽  
Vol 14 (18) ◽  
pp. 1157-1161 ◽  
Author(s):  
A. S. AL-RAWAF
Keyword(s):  
Cosmological Constant ◽  
Density Parameter ◽  
Suggested Model ◽  
Age Of The Universe ◽  
The Universe

Here, we discuss the cosmological consequences of a previous suggested model for the case K = ±1. It is shown that the model covers the whole observed ranges for the Hubble's constant, the age of the universe and the density parameter.

scholarly journals Cosmology from quantum potential in a system of oscillating branes

2016 ◽  
Vol 31 (01) ◽  
pp. 1650004 ◽  
Author(s):  
Alireza Sepehri
Keyword(s):  
Generalized Uncertainty Principle ◽  
Scalar Fields ◽  
Big Bang ◽  
Fundamental String ◽  
Extra Energy ◽  
Age Of The Universe ◽  
The Big Bang ◽  
M Theory ◽  
Derivatives Of ◽  
The Universe

Recently, some authors proposed a new mechanism which gets rid of the Big Bang singularity and shows that the age of the universe is infinite. In this paper, we will confirm their results and predict that the universe may expand and contract many N fundamental strings decay to N M0–anti-M0-branes. Then, M0-branes join each other and build a M8-anti-M8 system. This system is unstable, broken and two anti-M4-branes, a compactified M4-brane, a M3-brane in addition to one M0-brane are produced. The M3-brane wraps around the compactified M4-brane and both of them oscillate between two anti-M4-branes. Our universe is located on the M3-brane and interacts with other branes by exchanging the M0-brane and some scalars in transverse directions. By wrapping of M3-brane, the contraction epoch of universe starts and some higher order of derivatives of scalar fields in the relevant action of branes are produced which are responsible for generating the generalized uncertainty principle (GUP). By oscillating the compactified M4-M3-brane and approaching one of anti-M4-branes, one end of M3-brane glues to the anti-M4-brane and other end remains sticking and wrapping around M4-brane. Then, by getting away of the M4-M3 system, M4 rolls, wrapped M3 opens and expansion epoch of universe begins. By closing the M4 to anti-M4, the mass of some scalars become negative and they make a transition to tachyonic phase. To remove these states, M4 rebounds, rolls and M3 wraps around it again. At this stage, expansion branch ends and universe enters a contraction epoch again. This process is repeated many times and universe expands and contracts due to oscillation of branes. We obtain the scale factor of universe in this system and find that its values only at t [Formula: see text] shrinks to zero. Thus, in our method, the Big Bang is replaced by the fundamental string and the age of universe is predicted to be infinite. Also, when tachyonic states disappear at the beginning of expansion branch, some extra energy is produced and leads to an increase in the velocity of opening of M3. In these conditions, our universe, which is located on this brane, expands very fast and experiences an inflation epoch. Finally, by reducing the fields in 11-dimensional M-theory to the fields in four-dimensional universe, we show that our theory matches with quantum field theory prescriptions.

scholarly journals The Hubble Constant

2000 ◽  
Vol 17 (1) ◽  
pp. 45-47 ◽  
Author(s):  
Jeremy Mould
Keyword(s):  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
Big Bang ◽  
Accelerating Universe ◽  
De Sitter ◽  
Age Of The Universe ◽  
Extragalactic Distance Scale ◽  
The Big Bang ◽  
The Universe

AbstractWith the completion of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale, it is interesting to form the dimensionless quantity H0t0 by multiplying the Hubble Constant by the age of the Universe. In a matter dominated decelerating Universe with a density exceeding 0·26 of the critical value, H0t0 < 1; in an accelerating Universe with the same Ωm = 0·26, but dominated by vacuum energy with ΩV ≥ 1 – Ωm, H0t0 ≥ 1. If the first globular clusters formed 109 years after the Big Bang, then with 95% confidence H0t0 =1·0 ± 0·3. The classical Einstein–de Sitter cosmological model has H0t0 = ⅔.

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