The contribution of a field to the energy density and therefore the mass density and the pressure of the. The underlying theme is that cosmology gives us a unique window on the physics of nothing, or the quantummechanical properties of the vacuum. But first i would like to explain my understanding of the flatness problem. Its a very simple explanation, and its only possible with inflation and not within the conventional big bang theory. According to the new york timesof november 26, 1999, like the great navigators who. Home about research books inflation and quantum cosmology. In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe.
According to chaotic inflation, the universe starts off in a completely random state. I begin with a description of the initial conditions problems of the friedmannrobertsonwalker frw cosmology and then explain how inflation, an early period of. Is the theory at the heart of modern cosmology deeply flawed. Flatness, horizon and monopole problem, and additionally provides an explanation. The inflationary universe a new theory of cosmology suggests that the observable universe is embedded in a much larger region of space that had an extraordinary growth spurt a fraction of a second after the primordial big bang by alan h. Any region of space in this state will rapidly expand. It produced a response coauthored by another founder of inflation guth, the original authors produced their reply, but basically noone cares.
Inflationary cosmology is a highly successful framework for exploring these. One of the most important stages of the development of the in. 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 particular, i have a few questions regarding the flatness problem and how the inflation theory manages to resolve it. Assume, for a moment, the universe is not expanding. This is a course on cosmology, aimed at final year undergraduate students. The usual test for a theory is whether experiment agrees with model predictions. What everyone should know about where our matterandradiationfilled universe came from.
To solve these, the big bang theory is modified by the inflation theory, which states that the universe expanded rapidly shortly after it was created. One of the more enduring contributions of particle physics to cosmology is the prediction of inflation by the american physicist alan guth and others. Mcgill university physicist robert brandenberger and harvard physicist cumrun vafa spun their own take on cosmology and superstring theory with string gas cosmology pdf, another model that claims consistency with current observations but offers a different picture. T h e in flation ary u n iverse stanford university.
The origin of this book, first published in 1998, is a short lecture course at the uni versity of sussex, around 20 lectures, taught to students in the final year of a bachelors. Recently i have watched videos on how the inflation theory solves some problems that arise from the big bang theory. The test of inflation as the launch of the planck spacecraft approaches, eric hand investigates what the mission could mean for the predominant theory of the moments after the big bang. The physics world was rocked by a discovery that may shed light on the wild birth of our universe. General theory of relativity potential models of the theory. This paper is intended to offer a pedagogical treatment of inflationary cosmology, which is accessible to undergraduates. An introduction to modern cosmology university of belgrade. Guts 2 provides the framework for discussing the early universe. And thats exactly what the theory of cosmological inflation. Click download or read online button to get cosmological inflation and large scale structure book now. The development of physical theories of gravity was far from smooth, nor did it always conform. The prevailing theory about the origin and evolution of our universe is the socalled big bang theory. The second contender for a theory of initial conditions is quantum cosmology, the application of quantum theory to the entire universe.
The inflationary model solves many of the fundamental problems that challenge the standard big bang cosmology i. Flatness, horizon and monopole problem, and additionally provides an explanation for the initial conditions observed. Quantum field theory stipulates that the pressure of the vacuum energy is always negative and equal in magnitude to its energy density. This acceleration is believed to be driven by a quantum field in effect, some exotic kind of matter with a repulsive gravitational effect.
Inflationary universe theory the inflationary universe theory proposes a brief period of extremely rapid accelerating expansion in the very early universe, before the radiation dominated era called the hot big bang. In the original version of the inflationary theory guth 1981, the state that drove the. Despite this fact or maybe because of it it has become popular to propose various alternatives to inflation. I begin with a description of the initial conditions problems of the friedmannrobertsonwalker frw cosmology and then explain how inflation, an early period of accelerated expansion, solves these problems. First, i will act as fervent advo cate for, presenting the strongest advantages of the theory, and then, with equal fervor, as advocate against, presenting the most serious unresolved problems.
In another tiny fraction of a second, inflation slowed to a. A prediction of inflationary theory is that the variations are nearly scaleinvariant. Cosmology and time claus beisbart seminar philosophy of space and time. In physical cosmology, cosmic inflation, cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 10 78 in volume, driven by a negativepressure vacuum energy density. The reader is brought to the frontiers of current cosmological research by the discussion of more speculative ideas. Inflation and the theory of cosmological perturbations 3000 mpc cosmology 2. Turok and steinhardt are not the only physicists marshaling string theory to build alternatives to inflation. The case for inflation can be summarized by three dictums. In physical cosmology, the idea of inflation is a proposed theory that would explain many features of the presentday universe, including the existence of largescale structures such as galaxies.
The inflationary universe theory, on the other hand, is a description of the bang itself, and provides plausible answers to these questions and more. Cosmologists introduced this idea in 1981 to solve several important problems in cosmology. Some of the key questions for cosmology research are. One area of interest to cosmologists is the ways in which inflation theory might lead to insights into dark energy, or vice versa. Following the inflationary period, the universe continued to expand, but at. Cosmology, inflation, and the physics of nothing w. The inflation theory it proposes a period of extremely rapid exponential expansion of the universe prior to the more gradual big bang expansion, during which time the energy density of the universe was dominated by a cosmological constant type of vacuum energy that later decayed to produce the matter and radiation that fill the universe today. And in our current theory of particle physics, the standard model of particle physics, theres even one particular field called the higgs field, which has a nonzero mean value in the vacuum besides fluctuations. Inflation and string theory juan maldacena strings 2015, bangalore. In trying to understand the universe, two major problems remained. The basic idea is that at high energies matter is better described by fields than by classical means. The inflation debate princeton physics princeton university. The research in inflationary cosmology represented below ranges from the original foundations of the theory the first working examples, the first gauge invariant derivation of scaleinvariant density fluctuations, the first complete computations of the scalar and tensor microwave background predictions to exposing. Depending on the outcome of the observations, the theories will need to be abandoned, revised or extended to accommodate the data.
This is an ideal textbook both for advanced students of physics and astrophysics and for those with a particular interest in theoretical cosmology. Throughout the symposium, special attention was given to the connections between the fields. Jm and pimentel inflation is the leading candidate for a theory that produces the primordial fluctuations. Inflation cosmology simple english wikipedia, the free. This site is like a library, use search box in the widget to get ebook that. Shortlyafterward new measurements of the cosmic background radiation overturned the prevailing beliefs about the geometryand total mass density of the universe. The symposium marked a new era in the understanding of the science of the very small and the very large. According to the theory of inflation, the early universe expanded exponentially fast for a fraction of a second after the big bang. Problems with the theory of inflation physics forums. Inflationary theory postulates that there is a vacuum state with very large vacuum energy, caused by a nonzero vacuum expectation value of the inflaton field.
The inflationary epoch comprises the first part of the electroweak epoch following the grand unification epoch. This initial singularity is, however, not physical since general relativity fails for t. During the last 20 years inflationary theory 1, 2, 3 has evolved from a problematic hypothesis to an almost universally accepted cosmological paradigm. The term inflation refers to the explosively rapid expansion of spacetime that occurred a tiny fraction of a second after the big bang. Inflation and the new era of highprecision cosmology mit. The scale of inflation can be very high are there possible signatures from string. Today, the principles at the heart of inflation theory have a profound impact. It solves many fundamental cosmological problems and makes several predictions that agree very well with the observational data. An exposition on inflationary cosmology gary scott watson dept. Inflation and the theory of cosmological perturbations. The cosmological implications of this theory will be thoroughly discussed in 00 7 and 8. While the concept of dark energy in modern cosmological theory also accelerates the expansion of the universe, the mechanisms involved appear to be very different from those involved in inflation theory. In some regions matter will be more energetic than in others and inflation could ensue, producing the observable universe.
1106 850 300 320 1339 261 1407 1280 545 1054 1258 1183 729 39 1152 305 879 742 1402 880 808 686 1169 574 518 1490 823 417 1214