Alan Harvey Guth (New Brunswick, 27 de fevereiro de ) é um físico e cosmologista estadunidense. É professor e pesquisador do Instituto de Tecnologia de Massachusetts. Guth é conhecido por ser o pai da teoria da inflação cósmica. Segundo esta teoria, o universo expandiu-se exponencialmente nos . Criar um livro · Descarregar como PDF · Versão para impressão. ALAN H. GUTH, Victor F. Weisskopf Professor of Physics and MacVicar Most of Professor Guth's research has centered on the application of. Universo inflacionário . Alan Guth propõe a ideia de Alan Guth, “Inflationary universe: A possible solution to the horizon and flatness.
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PDF | The various cosmological models along history are briefly reviewed. The evolution Em décadas recentes, esse modelo foi aperfeiçoado para um novo conceito, o do Big Bang inflacionário. Na virada observations until, in , the American physicist Alan Guth proposed a .. GUTH, A. The Inﬂationary Universe. era inflacionaria en los primeros segundos de la existencia del universo II. . a nuestro universo (de hecho Allan Guth declaró en que las posibilidades son tan en España. Sitio web: durchcomppumalchi.cf depende del mecanismo “inflacionario” propuesto por el físico ruso Alexei estadounidense Alan Guth, según el cual el universo sufrió una expansión .. durchcomppumalchi.cf~verada/pubs/files/durchcomppumalchi.cf
The theory of inflation proposes that when our universe was only about a trillionth of a trillionth of a trillionth of a second old, a peculiar type of energy caused the cosmos to expand very rapidly. A tiny fraction of a second later, the universe returned to the more leisurely rate of expansion of the standard Big Bang model.
Inflation solved a number of outstanding problems in cosmology, such as why the universe appears so homogeneous on large scales. More piles of paper and dozens of magazines littered the floor. The prize was the services of a professional organizer for one day. She took piles of envelopes from the floor and began sorting them according to size.
We have been talking about the multiverse. While challenging the Platonic dream of theoretical physicists, the multiverse idea does explain one aspect of our universe that has unsettled some scientists for years: according to various calculations, if the values of some of the fundamental parameters of our universe were a little larger or a little smaller, life could not have arisen.
For example, if the nuclear force were a few percentage points stronger than it actually is, then all the hydrogen atoms in the infant universe would have fused with other hydrogen atoms to make helium, and there would be no hydrogen left. No hydrogen means no water. Although we are far from certain about what conditions are necessary for life, most biologists believe that water is necessary. On the other hand, if the nuclear force were substantially weaker than what it actually is, then the complex atoms needed for biology could not hold together.
As another example, if the relationship between the strengths of the gravitational force and the electromagnetic force were not close to what it is, then the cosmos would not harbor any stars that explode and spew out life-supporting chemical elements into space or any other stars that form planets. Both kinds of stars are required for the emergence of life. No life of any kind would exist. Does the universe care about life?
Intelligent design is one answer. Indeed, a fair number of theologians, philosophers, and even some scientists have used fine-tuning and the anthropic principle as evidence of the existence of God. The multiverse offers another explanation.
1.1 TEORÍAS DEL ORIGEN DEL UNIVERSO.pdf
If there are countless different universes with different properties—for example, some with nuclear forces much stronger than in our universe and some with nuclear forces much weaker—then some of those universes will allow the emergence of life and some will not.
Some of those universes will be dead, lifeless hulks of matter and energy, and others will permit the emergence of cells, plants and animals, minds.
From the huge range of possible universes predicted by the theories, the fraction of universes with life is undoubtedly small. The explanation is similar to the explanation of why we happen to live on a planet that has so many nice things for our comfortable existence: oxygen, water, a temperature between the freezing and boiling points of water, and so on.
Is this happy coincidence just good luck, or an act of Providence, or what? No, it is simply that we could not live on planets without such properties. Many other planets exist that are not so hospitable to life, such as Uranus, where the temperature is — degrees Fahrenheit, and Venus, where it rains sulfuric acid.
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The multiverse offers an explanation to the fine-tuning conundrum that does not require the presence of a Designer. The multiverse idea offers an explanation of why we find ourselves in a universe favorable to life that does not rely on the benevolence of a creator, and so if correct will leave still less support for religion.
Others, such as Weinberg and Guth, have reluctantly accepted the anthropic principle and the multiverse idea as together providing the best possible explanation for the observed facts. Our universe is what it is because we are here. The situation could be likened to a school of intelligent fish who one day began wondering why their world is completely filled with water. Many of the fish, the theorists, hope to prove that the entire cosmos necessarily has to be filled with water.
Synonyms and antonyms of inflationary universe in the English dictionary of synonyms
For years, they put their minds to the task but can never quite seem to prove their assertion. Then, a wizened group of fish postulates that maybe they are fooling themselves.
Maybe there are, they suggest, many other worlds, some of them completely dry, and everything in between. The most striking example of fine-tuning, and one that practically demands the multiverse to explain it, is the unexpected detection of what scientists call dark energy.
Little more than a decade ago, using robotic telescopes in Arizona, Chile, Hawaii, and outer space that can comb through nearly a million galaxies a night, astronomers discovered that the expansion of the universe is accelerating. Orthodox cosmological thought held that the expansion is slowing down.
After all, gravity is an attractive force; it pulls masses closer together. So it was quite a surprise in when two teams of astronomers announced that some unknown force appears to be jamming its foot down on the cosmic accelerator pedal.
The expansion is speeding up. Galaxies are flying away from each other as if repelled by antigravity. Physicists have named the energy associated with this cosmological force dark energy. No one knows what it is. Not only invisible, dark energy apparently hides out in empty space. Yet, based on our observations of the accelerating rate of expansion, dark energy constitutes a whopping three quarters of the total energy of the universe.
It is the invisible elephant in the room of science. The amount of dark energy, or more precisely the amount of dark energy in every cubic centimeter of space, has been calculated to be about one hundred-millionth 10—8 of an erg per cubic centimeter.
This may not seem like much, but it adds up in the vast volumes of outer space. Astronomers were able to determine this number by measuring the rate of expansion of the universe at different epochs—if the universe is accelerating, then its rate of expansion was slower in the past. From the amount of acceleration, astronomers can calculate the amount of dark energy in the universe.
Theoretical physicists have several hypotheses about the identity of dark energy. According to quantum physics, empty space is a pandemonium of subatomic particles rushing about and then vanishing before they can be seen. Dark energy may also be associated with an as-yet-unobserved force field called the Higgs field, which is sometimes invoked to explain why certain kinds of matter have mass.
Theoretical physicists ponder things that other people do not. And in the models proposed by string theory, dark energy may be associated with the way in which extra dimensions of space—beyond the usual length, width, and breadth—get compressed down to sizes much smaller than atoms, so that we do not notice them.
Thus, in absolute magnitude, the amount of dark energy actually present in our universe is either very, very small or very, very large compared with what it could be. This fact alone is surprising. On one thing most physicists agree: If the amount of dark energy in our universe were only a little bit different than what it actually is, then life could never have emerged. A little more and the universe would accelerate so rapidly that the matter in the young cosmos could never pull itself together to form stars and thence form the complex atoms made in stars.
And, going into negative values of dark energy, a little less and the universe would decelerate so rapidly that it would recollapse before there was time to form even the simplest atoms. Here we have a clear example of fine-tuning: out of all the possible amounts of dark energy that our universe might have, the actual amount lies in the tiny sliver of the range that allows life.
There is little argument on this point. It does not depend on assumptions about whether we need liquid water for life or oxygen or particular biochemistries. As before, one is compelled to ask the question: Why does such fine-tuning occur?
And the answer many physicists now believe: The multiverse. A vast number of universes may exist, with many different values of the amount of dark energy. Our particular universe is one of the universes with a small value, permitting the emergence of life.
We are here, so our universe must be such a universe. We are an accident.
From the cosmic lottery hat containing zillions of universes, we happened to draw a universe that allowed life. But then again, if we had not drawn such a ticket, we would not be here to ponder the odds.
The concept of the multiverse is compelling not only because it explains the problem of fine-tuning. As I mentioned earlier, the possibility of the multiverse is actually predicted by modern theories of physics. In regular inflation theory, the very rapid expansion of the infant universe is caused by an energy field, like dark energy, that is temporarily trapped in a condition that does not represent the lowest possible energy for the universe as a whole—like a marble sitting in a small dent on a table.
The properties of the radiation are found to be in excellent agreement with the predictions of the simplest models of inflation [ image ]. Working with Prof.
Edward Farhi and others, Guth has explored the question of whether it is in principle possible to ignite inflation in a hypothetical laboratory, thereby creating a new universe. The answer is a definite maybe.
They showed that it cannot be done classically, but with quantum tunneling it might be theoretically possible.
The new universe, if it can be created, would not endanger our own universe. Instead it would slip through a wormhole and rapidly disconnect completely.
teoria de la inflacion del universo pdf
Another intriguing feature of inflation is that almost all versions of inflation are eternal—once inflation starts, it never stops completely. Inflation has ended in our part of the universe, but very far away one expects that inflation is continuing, and will continue forever.
Is it possible, then, that inflation is also eternal into the past? Recently Guth has worked with Alex Vilenkin Tufts and Arvind Borde Southampton College to show that the inflating region of spacetime must have a past boundary, and that some new physics, perhaps a quantum theory of creation, would be needed to understand it. Much of Guth's current work also concerns the study of density fluctuations arising from inflation: What are the implications of novel forms of inflation?
Can the underlying theory be made more rigorous? Guth's earlier work has included the study of lattice gauge theory, magnetic monopoles and instantons, Gott time machines, and a number of other topics in theoretical physics. He grew up and attended the public schools in Highland Park, NJ, but skipped his senior year of high school to begin studies at the Massachusetts Institute of Technology.
He remained at MIT from to , acquiring S.All we can do is hope that the same theories that predict the multiverse also produce many other predictions that we can test here in our own universe.
The amount of dark energy, or more precisely the amount of dark energy in every cubic centimeter of space, has been calculated to be about one hundred-millionth 10—8 of an erg per cubic centimeter. If the multiverse idea is correct, the style of fundamental physics will be radically changed.
It is now time to demonstrate how all parts of the theory that we have described thus far The predicted spectrum of these fluctuations was calculated by Guth and others in With the trade-off awareness gained, some brief summaries available online have a place to fit in. Some may not.
As far as physicists are concerned, the fewer the fundamental principles and parameters, the better. Is this happy coincidence just good luck, or an act of Providence, or what?
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