Theory of Inflation

International Journal of Current Research and Academic Review, 2017

Article Info The Standard Big Bang Cosmology gives the most accepted concept about the beginning and evolution of the Universe. However, it has problems: the flatness problem, the horizon problem and the monopole problem. The predictions of the Standard Big Bang Cosmology do not match the observations of modern cosmologists. Nonetheless, the admirers of the Standard Big Bang Cosmology continued to find out ways for solving those problems and such attempts lead to our knowledge of Inflationary Cosmology. The theory of inflation, which was first proposed by Alan Guth in 1981, soon became a "need" of modern cosmology and various modified models of inflationary Universe were proposed. In this paper, the author gives a brief insight of the Standard Big Bang Cosmology, introduces inflationary cosmology with its brief background, reviews some concepts associated with cosmic inflation, explains how inflation can be classified into various types, describes few of the popular types in brief and explains how the cosmological problems are solved by cosmic inflation. Moreover, few insightful examples have been given to easily explain the fundamental concepts so that even a junior researcher can get thorough idea about the field by escaping the equations and simply going through the text selectively.

1999

An introductory account is given of the inflationary cosmology, which postulates a period of accelerated expansion during the Universe's earliest stages. The historical motivation is briefly outlined, and the modelling of the inflationary epoch explained. The most important aspect of inflation is that it provides a possible model for the origin of structure in the Universe, and key results are reviewed, along with a discussion of the current observational situation and outlook.

Studying the universe, understanding its origin and evolution has always been of great interest to humanity. In this context, cosmology proposes it, seeking to answer questions related to its structure, composition, and dynamics. Initially, there were various proposed models, but the one that has achieved considerable success when compared with different cosmological observations was the Hot Big Bang model. This implies a universe in expansion, homogeneous and isotropic on a large scale, that is, there are no preferred points or directions in the universe (WEINBERG, 2008). However, despite its great success, it has some problems, among them the horizon and flatness problems can be highlighted. A widely accepted proposal to solve them is that the universe, at its initial moment, underwent a phase of exponential growth. Such a proposal constitutes what is known as inflationary models, which, in addition to solving the problems present in the Hot Big Bang model, provides a good explanation for the formation of the anisotropies of the universe as a result of the expansion of quantum fluctuations in the scalar field generating the inflationary period called inflaton.

Classical and Quantum Gravity, 2002

This article gives a brief overview of some of the theory behind the inflationary cosmology, and discusses prospects for constraining inflation using observations. Particular care is given to the question of falsifiability of inflation or of subsets of inflationary models. ‡

a work done to simply understand the basic inflationary cosmology with minimal use of necessary general relativity

2023

This dissertation begins by exploring the distance ladder in cosmology, which is used to measure astronomical distances and is crucial to our understanding of the universe’s size and scale. The dissertation then provides an overview of the General Theory of Relativity and its application to the Friedmann-Robertson-Walker (FRW) Universe, which is a model of the universe that assumes it is homogeneous and isotropic on large scales. Then it explores the dynamics and properties of FRW Universe. Apart from having unmatched successes, Big Bang theory still has some problems, including the horizon problem, flatness problem, and monopole problem. To address these issues, a new theory was proposed in the 1980s known as Cosmic Inflation. The dissertation explains how the Slow Roll Model and Power Law Potential can be used to describe the inflaton field’s behavior during the inflationary period. Then it reviews some other inflation models and reheating. We also study the Cosmic Microwave Background Radiation(CMBR), which is the residual radiation left over from the Big Bang as a solution to these problems. The CMBR provides a window into the early universe, and its properties can be used to study the universe’s evolution. Finally, the paper concludes by discussing Precision Cosmology, which involves using data from Supernova Ia to estimate cosmological parameters. The paper also discusses the results from Wilkinson Microwave Anisotropy Probe(WMAP) and Planck data, which provide strong evidence for Cosmic Inflation. This data has also been successfully used to constrain the parameters of the inflaton field. Through this comprehensive analysis, the paper provides a detailed and informative overview of Cosmic Inflation and its significance in modern cosmology.

2000

Choosing the three phenomenological models of the dynamical cosmological term �, viz., � � (úa/a)2, � � ¨a/a and � � � where a is the cosmic scale factor, it has been shown by the method of numerical analysis for the considered non-linear differential equations that the three models are equivalent for the flat Universe k = 0 and for

Annals of the New York Academy of Sciences, 1984

For the reader who would like a more detailed review of this subject, let me point out that Reference 9 contains reviews by both A. D. Linde and myself. 'For a general background in cosmology, see Reference 25. At a less technical level, see References 26 and 27.

2013

The inflationary phase of the Universe is explored by proposing a toy model related to the scalar field, termed as {\it inflaton}. The potential part of the energy density in the said era is assumed to have a constant vacuum energy density part and a variable part containing the inflaton. The prime idea of the proposed model constructed in the framework of the closed Universe is based on a fact that the inflaton is the root cause of the orientation of the space. According to this model the expansion of the Universe in the inflationary epoch is not approximately rather exactly exponential in nature and thus it can solve some of the fundamental puzzles, viz. flatness as well as horizon problems. It is also predicted that the constant energy density part in the potential may be associated to the dark energy, which is eventually different from the vacuum energy, at least in the inflationary phase of the Universe. However, the model keeps room for the end of inflationary era.

Astrophysics and Space Science Proceedings, 2008

We present a brief review of Cosmological Inflation from the personal perspective of the author who almost 30 years ago proposed a way of resolving the problem of Cosmological Horizon by employing certain notions and developments from the field of High Energy Physics. Along with a brief introduction of the Horizon and Flatness problems of standard cosmology, this lecture concentrates on personal reminiscing of the notions and ideas that prevailed and influenced the author's thinking at the time. The lecture then touches upon some more recent developments related to the subject and concludes with some personal views concerning the direction that the cosmology field has taken in the past couple of decades and certain speculations some notions that may indicate future directions of research.