The thermal history of the universe we will now work our way backward in time to see what the universe was like in the really old days. The thermal history of the universe n this class l evolution of radiation and matter l timeline of the hot big bang l particle physics in the early universe i. On the expansion of the universe albert einstein 18791955 predicted a general expansion of the universe from his general theory of relativity. For much of this book, therefore, we will be considering the properties of an idealized, perfectly smooth, model universe. Too much helium our sun is about 28% helium by mass. Toward understanding of the complete thermal history of. Evolution of the scale factor and the hubble constant. The entropy of the neutrinos, and the entropies of the rest of the universe, then become separately conserved. It is useful to keep in mind some simple relations between time, distance and temperature in a radiationdominated universe. When the universe was times smaller and the cmb photons were at 3000k they were energetic enough disintingrate atoms into. Thermal history of the universe with dark energy component.
Rapid interactions drive distribution to thermal equilibrium but must compete with the expansion rate of universe. The consequent radiation production could have an important effect on the thermal history of the universe, even if the density of the holes is small. Cosmic microwave background anisotropy at degree angular scales and the thermal history of the universe. Part 2 describes the theory of gravitational instability in both the linear and nonlinear regimes. Thermal history of the universe n recall from last class the following two facts. We study the induced primordial gravitational waves gw coming from the effect of scalar perturbation on the tensor perturbation at the second order of cosmological perturbation theory. We will learn that they dont always cancel each other because the universe is cooling, and that means it cant be exactly in thermal equilibrium. Mar 27, 2011 pdf we discuss the deviations from the ideal relativistic thermal bath. The chronology of the universe describes the history and future of the universe according to big bang cosmology.
Mar 03, 2017 understanding the thermal history of the universe through direct and indirect detection of dark matter cl. Pregalactic black hole accretion and the thermal history. One reason why physicists are good at calculating nuclear reactions. Pdf qcd contributions to the thermal history of the. The main events of the thermal history and the transition between di erent entitydominated eras are analysed.
To reach our destination, we journey through background cosmology, statistical physics and particle physics. Overview our last problem in homogeneous cosmology is to consider the history of the matter content of the universe. But in the early period, the universe was in fact dominated by radiation, as we. Understanding the very earliest moments requires knowledge of the fundamental.
Abstract an extensive numerical analysis is made of distortions of the microwave background spectrum that can arise over a broad interval of cosmic times. Blackbody radiation and the early history of the universe, part i. Study materials massachusetts institute of technology. There is no evidence that this occurred ringwood, 1990. Part 1 deals with the friedmann model, the thermal history of the universe, and includes a description of observed structures in the universe. Writeup on chandrasekhar link to article nuclear binding energies. Photon trajectories near a black hole new views of neutron stars. Hadron epoch between 106 seconds and 1 second after the big bang hadrons are particles that feel the strong nuclear force and are combinations of quarks. Just as understanding the thermal history of the early universe has taught us an enormous amount about both cosmology and particle physics see, e. Thermal history hubbles discovery of the expansion of the universe in 1929 revealed our beginning from a much smaller and much denser initial state big bang theory. An especially important phase involved the formation of the light elements hydrogen, deuterium, helium, and small amounts of lithium and beryllium, aka \ big bang nucleosynthesis. Download this course mit opencourseware physics introduction to astronomy.
Above this temperature, thermal production of baryons and their strong interaction is significant and somewhat difficult to model. In this moment it was realized the universe is expanding. Toward understanding of the complete thermal history of the universe. Penzias and wilsons discovery of the cosmic microwave background radiation. The average energy per photon depends on the temperature of the universe and therefore, at early times, photons have a large amount of energy. National research council order in the universe cosmology is the study of the evolution of the universe from its first moments to the present. An especially important phase involved the formation of the light elements hydrogen, deuterium, helium, and small amounts of lithium and beryllium, aka \big bang nucleosynthesis.
A brief thermal history of the universe springerlink. We now turn to the role of the background radiation, in particular the cosmic microwave background radiation, in the study of the big bang model of the universe. Before we can do that, however, we need to work out in some detail the thermal history of the matter and radiation content of the universe according to the standard big bang picture. Let us next consider some key events in the evolutionary history of our universe. The topics are chosen to illustrate ideas and methods of thermal physics, but also because many. Some more details of the nuclear reactions in the early universe. From this point onwards the physics of the early universe is better understood, and less speculative. The key to understanding the thermal history of the universe is the comparison between the rate of interaction for a given process, and the expansion rate of the universe, h. Quantitative introduction to physics of the solar system, stars, interstellar medium, the galaxy, and universe, as determined from a variety of astronomical observations and models. In fact, expansion or collapse deflation seemed an almost inevitable result of his original field equations. Thermal equilibrium of particle species in the early universe is maintained by scattering of parti cles. Towards understanding thermal history of the universe. Pdf qcd contributions to the thermal history of the early. This picture is simple, elegant, and robust, but it can not be complete.
Understanding the thermal history of the universe through. It is useful to keep in mind some simple relations between time, distance and temperature in. H is satis ed, then the timescale of particle interactions is much smaller than the char. Background frw universe and thermal history this rst part of these lectures on the early universe is concerned with its overall content and evolution. But as the universe expanded and cooled down, the distance between particles increased and the expansion rate of the universe h overtook the neutrino interaction rate. But as the universe expanded and cooled down, the distance between particles increased and the expansion rate of the universe h. We now have to set the scene for our attack on the major problems of astrophysical cosmology how do we account for the origin and evolution of the galaxies. Qcd contributions to the thermal history of the early univer. The observed ratio of photons 400 per cubic centimeter to hydrogen in the universe is about 1 billion to 1. Thus, equilibrium is maintained and the expansion of the.
In physical cosmology, cosmic inflation, cosmological inflation, is the extremely rapid exponential expansion of the early universe by a factor of at least 1078 in. Newtonian cosmology, dynamical expansion and thermal history of the universe. Evidence for the hot big bang 1 cosmic expansion covered in previous lectures 2 big bang theory can predict the 24% primordial helium abundance that is observed everywhere. Satellites, balloonborne, and groundbased experiments scrutinize the cmb sky at multiple scales, and therefore enable to investigate not only the evolution of the early universe, but also its. To this end, we will consider the simplest possible model where the universe is highly symmetric. Gravitational waves are truly transparent to matter in the universe and carry the information of the very early epoch. Thermal history of the universe with dark energy component induced. This project is an attempt to fathom the thermal history of the universe. We show that the energy density spectrum of the primordial gravitational waves. This thermal history for the early universe can then be used to try to understand the primordial origin of dark matter dm particles, baryons, and the matter antimatter asymmetry. Not usable as a restricted elective by physics majors.
Thermal history of the universe january 17, 2017 1 thermodynamics in the expanding universe as discovered by penzias and wilson in 1965, and determined much more precisely in the early 1990s by the far infrared absolute spectrometer firas on nasas cosmic background ex. The heat death of the universe, also known as the big chill or big freeze, is a conjecture on the ultimate fate of the universe, which suggests the universe would evolve to a state of no thermodynamic free energy and would therefore be unable to sustain processes that increase entropy. However, with additional theoretical input the hypothesis about the thermal freezeout can potentially be verified, as illustrated with two examples. Equilibrium distributions shortrange interactions maintaining thermodynamic equilibrium. There may have been a global magma ocean beneath a massive protoatmosphere of. Journal of high energy physics, may 20 kohei kamada, tatsuo kobayashi, keisuke ohashi, yutaka ookouchi. After cosmic inflation ends, the universe is filled with a quark gluon plasma. Pdf cosmic microwave background anisotropy at degree. Thus, equilibrium is maintained and the expansion of the universe can be considered to be adiabatic as long as the interaction rate. The earliest stages of the universe s existence are estimated as taking place. We introduce the idea of thermal decoupling and discuss its signi.
Constraints on the thermal history of the universe from. The subject matter in this course divides intofundamental ideas and methods of thermal physics, which actually are not limited to this area and have very general relevance for the rest of physics. The most well understood phase of the universe occurs when the temperature is less than about 10 12 k. Thermal history of the universe california institute of.
Remember the ratio of photons to baryons in the universe now is one billion to one. We can ignore such complications at lower temperatures and as we shall see. So far weve dealt with a universe which contains only nonrelativistic matter and that, as we said from the beginning, describes our universe for the bulk of its history. The matter temperature would be boosted well above its friedmann value and, the matter would be completely reionized.
Toward understanding of the complete thermal history of the. Hence the universe used to be a real hot and dense place. H is satis ed, then the timescale of particle interactions is much smaller than the characteristic expansion timescale. We use the evolution of the standard model degrees of freedom with respect to temperature in the early universe to compute the induced gravitational waves bakcground.
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