scholarly journals Relativistic Cosmology with an Introduction to Inflation

2021 ◽  
Author(s):  
Muhammad Zahid Mughal ◽  
Iftikhar Ahmad ◽  
Juan Luis GARCÍA GUIRAO
Keyword(s):  
Standard Model ◽  
Early Universe ◽  
Large Scale ◽  
Initial Conditions ◽  
Big Bang ◽  
Relativistic Cosmology ◽  
The Standard Model ◽  
Big Bang Model ◽  
The Big Bang ◽  
The Universe

In this review article the study of the development of relativistic cosmology and introduction of inflation in it is carried out. We study the properties of standard cosmological model developed in the framework of relativistic cosmology and the geometric structure of spacetime connected coherently with it. We examine the geometric properties of space and spacetime ingrained into the standard model of cosmology. The big bang model of the beginning of the universe is based on the standard model which succumbed to failure in explaining the flatness and the large-scale homogeneity of the universe as demonstrated by observational evidence. These cosmological problems were resolved by introducing a brief acceleratedly expanding phase in the very early universe known as inflation. Cosmic inflation by setting the initial conditions of the standard big bang model resolves these problems of the theory. We discuss how the inflationary paradigm solves these problems by proposing the fast expansion period in the early universe.

scholarly journals Relativistic Cosmology with an Introduction to Inflation

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 276
Author(s):  
Muhammad Zahid Mughal ◽  
Iftikhar Ahmad ◽  
Juan Luis García Guirao
Keyword(s):  
Standard Model ◽  
Early Universe ◽  
Large Scale ◽  
Initial Conditions ◽  
Big Bang ◽  
Relativistic Cosmology ◽  
The Standard Model ◽  
Big Bang Model ◽  
The Big Bang ◽  
The Universe

In this review article, the study of the development of relativistic cosmology and the introduction of inflation in it as an exponentially expanding early phase of the universe is carried out. We study the properties of the standard cosmological model developed in the framework of relativistic cosmology and the geometric structure of spacetime connected coherently with it. The geometric properties of space and spacetime ingrained into the standard model of cosmology are investigated in addition. The big bang model of the beginning of the universe is based on the standard model which succumbed to failure in explaining the flatness and the large-scale homogeneity of the universe as demonstrated by observational evidence. These cosmological problems were resolved by introducing a brief acceleratedly expanding phase in the very early universe known as inflation. The cosmic inflation by setting the initial conditions of the standard big bang model resolves these problems of the theory. We discuss how the inflationary paradigm solves these problems by proposing the fast expansion period in the early universe. Further inflation and dark energy in fR modified gravity are also reviewed.

Alternative cosmological theories

2019 ◽  
pp. 119-161
Author(s):  
Helge Kragh
Keyword(s):  
Standard Model ◽  
Cosmic Time ◽  
Big Bang ◽  
Field Equations ◽  
Static Universe ◽  
The Standard Model ◽  
Scientific Nature ◽  
Big Bang Model ◽  
The Universe ◽  
Alternative Theories

Since about 1970 the broadly accepted theory of the universe has been the standard hot big-bang model. However, there is and has always been alternative theories which challenge one or more features of the standard model or, more radically, question the scientific nature of cosmology. Is the universe governed by Einstein’s field equations? Is it really in a state of expansion? Did it begin with a big bang? The chapter discusses various alternative or heterodox theories in the period from about 1930 to 1980, among them the idea of a static universe and the conception that our universe evolves cyclically in infinite cosmic time. While some of these theories have been abandoned long ago, others still live on and are cultivated by a minority of cosmologists and other scientists.

The early universe in a generalized theory of gravitation

1982 ◽  
Vol 60 (5) ◽  
pp. 659-663 ◽  
Author(s):  
J. W. Moffat ◽  
D. Vincent
Keyword(s):  
Early Universe ◽  
Initial Conditions ◽  
Big Bang ◽  
Field Equations ◽  
Anisotropic Solution ◽  
Plane Symmetric ◽  
Frw Model ◽  
Theory Of Gravitation ◽  
The Big Bang ◽  
The Universe

The standard Friedmann–Robertson–Walker (FRW) big-bang model of the universe requires special initial conditions: the early universe is highly homogeneous and isotropic even though there exist causally disconnected regions (horizon problem). A plane symmetric (anisotropic) solution of a system of field equations in a generalized theory of gravitation, predicts the beginning of the universe as a vacuum instability at a specific fundamental time (which can be associated with the Planck time (tp)), after which matter is created as the universe begins to expand. At a time t = tc there is a singular expansion, the anisotropy vanishes, and the physical horizon becomes infinite. Thereafter the solution of the field equations goes over into the FRW model. Thus the special initial conditions of the FRW model at the big-bang singularity t = tc are predicted by the theory.

scholarly journals Of Cosmic Background Anisotropies

1996 ◽  
Vol 168 ◽  
pp. 31-44
Author(s):  
G.F. Smoot
Keyword(s):  
Large Scale ◽  
Thermal Emission ◽  
Big Bang ◽  
Microwave Background ◽  
The Standard Model ◽  
The Big Bang ◽  
The Universe ◽  
Fundamental Physical ◽  
Large Scale Structure Formation

Observations of the Cosmic Microwave Background (CMB) Radiation have put the standard model of cosmology, the Big Bang, on firm footing and provide tests of various ideas of large scale structure formation. CMB observations now let us test the role of gravity and General Relativity in cosmology including the geometry, topology, and dynamics of the Universe. Foreground galactic emissions, dust thermal emission and emission from energetic electrons, provide a serious limit to observations. Nevertheless, observations may determine if the evolution of the Universe can be understood from fundamental physical principles.

scholarly journals The H0 Key Project: Cepheids in NGC925, M101 and M100

1995 ◽  
Vol 155 ◽  
pp. 258-259
Author(s):  
S. M. G. Hughes
Keyword(s):  
Standard Model ◽  
Hubble Space Telescope ◽  
Big Bang ◽  
Distance Scale ◽  
Space Telescope ◽  
The Standard Model ◽  
Age Of The Universe ◽  
Extragalactic Distance Scale ◽  
The Big Bang ◽  
The Universe

AbstractAs part of the Extragalactic Distance Scale Key Project, the Hubble Space Telescope has been used to identify Cepheids in M100, M101 and NGC925, and to measure distances derived from the Cepheid PL relation. For M100, the distance of 17.1 ± 1.8 Mpc has been used to infer a preliminary value for H0 of ~ 80 km/s/Mpc, which brings the age of the Universe derived from the standard model of the Big Bang into conflict with the ages of the oldest stars.

Inflationary models of the primordial universe

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Large Scale Structure ◽  
Big Bang ◽  
Scale Structure ◽  
Fine Tuning ◽  
Accelerated Expansion ◽  
History Of ◽  
Big Bang Model ◽  
The Universe

This chapter addresses the problem of fine-tuning the initial conditions of the previous chapter’s hot Big Bang model, so that the universe has the observed properties, as well as the problem of the origin of large-scale structure. It shows that these problems are related to each other, and can be solved by assuming a period of accelerated expansion in the earliest history of the universe. Since the 1980s, the general acceptance of this idea of a primordial inflationary phase can be considered as the third phase in the history of the development of relativistic cosmology. The chapter first outlines the issues with the hot Big Bang model: the flatness problem; the Big Bang horizon, and monopole problems; and the problem of the origin of the large-scale structure. It then provides a solution in the form of inflation, and goes on to discuss ‘chaotic’ inflation.

scholarly journals Thermodynamics of the $$R_{\mathrm{h}}=ct$$ Universe: a simplification of cosmic entropy

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Fulvio Melia
Keyword(s):  
Standard Model ◽  
Second Law Of Thermodynamics ◽  
Big Bang ◽  
Second Law ◽  
Arrow Of Time ◽  
Physical Conditions ◽  
The Standard Model ◽  
The Big Bang ◽  
Low Entropy ◽  
The Universe

AbstractIn the standard model of cosmology, the Universe began its expansion with an anomalously low entropy, which then grew dramatically to much larger values consistent with the physical conditions at decoupling, roughly 380,000 years after the Big Bang. There does not appear to be a viable explanation for this ‘unnatural’ history, other than via the generalized second law of thermodynamics (GSL), in which the entropy of the bulk, $$S_\mathrm{bulk}$$ S bulk , is combined with the entropy of the apparent (or gravitational) horizon, $$S_{\mathrm{h}}$$ S h . This is not completely satisfactory either, however, since this approach seems to require an inexplicable equilibrium between the bulk and horizon temperatures. In this paper, we explore the thermodynamics of an alternative cosmology known as the $$R_{\mathrm{h}}=ct$$ R h = c t universe, which has thus far been highly successful in resolving many other problems or inconsistencies in $$\varLambda $$ Λ CDM. We find that $$S_{\mathrm{bulk}}$$ S bulk is constant in this model, eliminating the so-called initial entropy problem simply and elegantly. The GSL may still be relevant, however, principally in selecting the arrow of time, given that $$S_{\mathrm{h}}\propto t^2$$ S h ∝ t 2 in this model.

The Cosmic Microwave Background

2020 ◽  
pp. 272-289
Author(s):  
Hui Chieh Teoh
Keyword(s):  
Cosmic Microwave Background ◽  
Early Universe ◽  
Large Scale ◽  
Big Bang ◽  
Space Missions ◽  
Expanding Universe ◽  
Microwave Background ◽  
The Big Bang ◽  
The Universe

The cosmic microwave background (CMB) holds many secrets of the origin and the evolution of our universe. This ancient radiation was created shortly after the Big Bang, when the expanding universe cooled and became transparent, sending an afterglow of light in all directions. It is a pattern frozen in place that dates back to 375,000 years after the birth of the universe. Numerous experiments and space missions have made increasingly higher resolution maps of the CMB radiation, with the aims to learn more about the conditions of our early universe and the origin of stars, galaxies, and the large-scale cosmic structures that populate our universe today.

Naming the Big Bang

2012 ◽  
Vol 44 (1) ◽  
pp. 3-36 ◽  
Author(s):  
Helge Kragh
Keyword(s):  
Scientific Community ◽  
Big Bang ◽  
Consensus Model ◽  
Initial State ◽  
The Standard Model ◽  
Modern Cosmology ◽  
Fred Hoyle ◽  
The Big Bang ◽  
The Universe ◽  
Origin Of The Universe

The standard model of modern cosmology is known as the hot big bang, a name that refers to the initial state of the universe some fourteen billion years ago. The name Big Bang introduced by Fred Hoyle in 1949 is one of the most successful scientific neologisms ever. How did the name originate and how was it received by physicists and astronomers in the period leading up to the hot big bang consensus model in the late 1960s? How did it reflect the meanings of the origin of the universe, a concept that predates the name by nearly two decades? Contrary to what is often assumed, the name was not an instant success—it took more than twenty years before Big Bang became a household word in the scientific community. When it happened, it was used with different connotations, as is still the case. Moreover, it was used earlier and more frequently in popular than in scientific contexts, and not always relating to cosmology. It turns out that Hoyle’s celebrated name has a richer and more surprising history than commonly assumed and also that the literature on modern cosmology and its history includes many common mistakes and errors. An etymological approach centering on the name Big Bang provides supplementary insight to the historical understanding of the emergence of modern cosmology.

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.

Sign in / Sign up

Export Citation Format

Share Document