To our great regret, we do not have the opportunity to rewind time back and see how the Universe developed in the first minutes of its life. Using mathematics and observational data, the best minds on the planet build the most daring models. One of them is cosmic inflation.
The inflationary theory, or inflationary model of the universe, combines ideas from quantum physics and particle physics to explore the early moments of the universe just after the Big Bang. According to her, the Universe was formed in a very unstable state, which provoked its rapid expansion in the very first moments. One of the consequences of this expansion is that the universe is much larger than originally anticipated, and it stretches much further than our telescopes can see. In addition, this theory predicts some properties that are not explained in the framework of the Big Bang theory, such as uniform energy distribution and flat space-time geometry.
The theory of an inflationary universe was developed by physicist Alan Guth in 1980. Today it is considered a generally accepted part of the Big Bang theory, even though the central ideas of the latter were established much earlier than the inflationary theory was formulated.
How it all started
The Big Bang theory has shown itself to be very successful over the years - in particular, given that it was confirmed through the discovery of the background radiation (microwave background). However, despite the great success of this theory in explaining most of the aspects observed in the universe, three problems remained:
The Big Bang model seemed to predict a curved universe in which energy was distributed unevenly and in which there were many magnetic monopoles. However, none of this matched the data.
Alan Guth / Annette Boutellier.
Physicist Alan Guth first learned about the problem of flatness at a lecture by Robert Dick at Cornell University in 1978. In the years that followed, Guth applied concepts from particle physics to this situation and developed an inflationary model of the early universe.
On January 23, 1980, Guth presented his findings in a lecture at the SLAC National Accelerator Laboratory. His revolutionary idea was that the principles of quantum physics from the very heart of particle physics could be applied to the early days of the Big Bang. According to him, the universe should have had a high energy density. According to thermodynamics, the density of the universe should have caused it to expand at an incredible rate.
In fact, according to the new model at that time, the Universe should have arisen in a "false vacuum" and in the absence of the Higgs mechanism (in other words, the Higgs boson did not exist). She had to go through a process of hypothermia in search of a stable low-energy state (the "true vacuum" in which the Higgs mechanism operates) - and that is what triggered a period of rapid expansion.
How fast is it? According to the model, the universe was doubling every 10-35 seconds. Thus, in the first 10-30 seconds after the Big Bang, it would have doubled in size 100 thousand times, and this is more than enough to explain the problem of flatness. Even if the universe had some curvature at the very beginning, this degree of expansion would lead to the fact that today everything would look flat. (Note that the Earth is large enough to make it look flat to us, although we know that the surface we are standing on is curved to form a spherical object.)
The quantum fluctuations that occur during inflation are indeed stretching across the universe. In its large-scale manifestation, inflation leads to the fact that the universe becomes flat and loses its early curvature / E. Siegel / Beyond the Galaxy.
In addition, the energy is distributed so evenly due to the fact that at the very beginning we were a very small part of the Universe, which expanded so quickly that even if there were significant irregularities in the distribution of energy, they would be too far from us for us could have noticed or felt them. This, in turn, serves as a solution to the homogeneity problem.
Development of theory
According to Alan Guth himself, the problem with the theory was that once inflation started, it would have to go on indefinitely. Scientists have not seen any hints of any distinct mechanism for "turning off" this process.
Also, if space was constantly expanding at this rate, then the idea previously expressed by Sidney Coleman would not have worked. Coleman predicted that small bubbles formed during phase transitions in the early universe, which merged with each other. In the presence of inflation, the bubbles would move away from each other too quickly, without having time to unite.
The Soviet physicist Andrei Linde drew attention to this problem. He studied it and found that there is another interpretation that provides a solution to this problem. At the same time - it was still the 1980s - on the other side of the Iron Curtain, Andreas Albrecht and Paul Steinhardt came to a similar decision on their own.
Andrey Linde / LA Cicero.
The point is that in the original Guth model, more than one inflationary area was allowed to arise, which, in turn, could collide. In this case, the result was a disorderly space, in which radiation and matter have an inhomogeneous density. This was not at all consistent with what was observed in reality. Linde, Albrecht, and Steinhardt changed the scalar field equation - and it all made sense. According to this solution, our observable universe originated from a single vacuum bubble, which separated from other inflationary regions of space. It is about unimaginable - by all standards - enormous distances.
Such a different theory of inflation
The inflationary theory has several names. For example, cosmological inflation, cosmic inflation, inflation, old inflation (as the original version of Alan Guth's theory is called), new inflationary theory (the model developed by Linde, Albrecht and Steinhardt).
There are also two close versions of the theory: the chaotic theory of inflation and eternal inflation. In these theories, the inflation mechanism did not just happen once - right after the Big Bang - but it happens again and again in different regions of space. These models assume a rapidly growing number of "bubble universes" that are part of the Multiverse, or Multiverse. Some physicists note that these predictions are present in all versions of the inflationary model of the universe, and therefore do not consider them to be different theories.
Vladimir Guillen