Astronomy

Inflationary theory

Inflationary theory

According to the theory of the Big Bang or the Big Bang, generally accepted, the Universe arose from an initial explosion that caused the expansion of matter from a state of extreme condensation.

However, in the original formulation of the Big Bang theory there were several unresolved problems. The state of matter at the time of the explosion was such that normal physical laws could not be applied.

The degree of uniformity observed in the Universe was also difficult to explain because, according to this theory, the Universe would have expanded too quickly to develop this uniformity.

According to the Big Bang theory, the expansion of the universe loses speed, while inflationary theory accelerates it and induces the distancing, faster and faster, of some objects from others. This speed of separation becomes greater than the speed of light, without violating the theory of relativity, which prohibits any body of finite mass from moving faster than light. What happens is that the space around objects expands faster than light, while bodies remain at rest in relation to it.

This extraordinary speed of initial expansion is attributed to the uniformity of the visible universe, the parts that constituted it were so close to each other, that they had a common density and temperature.

Physicist and cosmologist Alan H Guth of the Massachusetts Institute of Technology (M.I.T.) suggested in 1981 that the hot universe, at an intermediate stage, could expand exponentially.

Guth's idea postulated that this process of inflation was developing while the primordial universe was in the state of unstable supercooling. This supercooled state is common in phase transitions; for example, under suitable conditions the water remains liquid below zero degrees. Of course, supercooled water ends up freezing; This event occurs at the end of the inflationary period.

In 1982 the Russian cosmologist Andrei Linde introduced what was called "new hypothesis of the inflationary universe". Linde realized that inflation is something that arises naturally in many elementary particle theories, including the simplest models of scalar fields.

If most physicists have assumed that the universe was born at once; that in the beginning this was very hot, and that the scalar field at the beginning had minimal potential energy, then inflation appears as natural and necessary, far from an exotic phenomenon appealed by theorists to get out of their problems. It is a variant that does not require quantum gravitational effects, phase transitions, supercooling or also an initial superheat.

Considering all the possible types and values ​​of scalar fields in the primordial universe and trying to check if any of them leads to inflation, it is found that in places where it does not occur, they remain small, and in the domains where it occurs they end being exponentially large and dominate the total volume of the universe. Considering that scalar fields can take arbitrary values ​​in the primordial universe, Andrei Linde called this hypothesis "chaotic inflation."

Inflationary theory predicts that the universe must be essentially flat, which can be tested experimentally, since the density of matter of a flat universe is directly related to its speed of expansion.

The other testable prediction of this theory has to do with the density disturbances produced during inflation. These are perturbations of the distribution of matter in the universe, which could even be accompanied by gravitational waves. The disturbances leave their mark on the cosmic microwave background, which fills the cosmos for almost 13.8 billion years.

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