Inflation Theory Detailed

The inflation theory originated at the end of the 1970s from the study a particle physics expert, Alan Guth, was leading with Henry Tye about monopoles. Monopoles are hypothetical, numerous, heavy mass, particles due to appear with the second split of the Universe forces at 10^-35 seconds after the Big Bang. Computing the total mass such particles would reach, Guth and Tye realized that they would have forbidden the Universe to develop beyond 6,000 years. The Universe would have just falled back in a Big Crunch. The question was: why did the Universe continue to expand? And the answer was the inflation theory. Simply said, the inflation theory is a theory which gets rid of the monopoles

Scalar Field Vs. Monopoles

Monopoles appear in the process along which fundamental forces of the Universe are splitting. At the farthest of the early Universe all the four main forces of today's physics are assumed unified: gravity, the electromagnetic force, the strong and weak nuclear forces. As the Big Bang occurs, the Universe expands, the temperatures decrease, and the forces spontaneously split. At 5.38 x 10^-44 seconds (which is the Planck time, the farthest moment physics can reach), the first split occurs. Gravity separates from the other forces which remain unified. When this second period of the Universe -the Great Unification- ends (10^-35 seconds after the Big Bang) the second split occurs: the strong nuclear force separates from the weak and the electromagnetic forces which remain unified as the electroweak force. Guth and Tye are working then about the Grand Unified Theories (GUTs) trying to push the Standard Model of physics a step further to reach a comprehensive view of all the forces of the particles world. It is this theoretical frame which brings the creation of monopoles at the moment of the second split in the forces. As the monopoles either must not exist or exist in far less number than predicted to allow a furter expansion of the Big Bang, Guth and Tye just insert into this view of the early Universe a mechanism which prevents the formation of monopoles

Guth and Tye are building upon a concept of the quantum mechanics which is the concept of "false vacuum". In the 1970s particles physicists are understanding that the Standard Model of physics generates, at high energies, a lot of new forms of matter as a system, in physics is not described by the matter -the particles, it contains, but by the concept of field. A field is a mathematical quantity only. It may, or not, contains particles. Hence fields may exist, to which no particles are associated, yet having a value, and yet having a strong energy. This energy is a strong, vacuum-based, cohesive, anti-gravitational energy. Such field are temporary and cannot be lowered quickly. They turn into usual matter and usual radiation when they stop expanding. A Higgs field e.g. is a scalar field as should be states of matter predicted by the Grand Unified Theories. Hence a false vacuum is what Guth and Tye are looking for!

The Inflation Is a Scalar Field at Work

When the Universe is decreasing in temperature, it passes through phase transitions. A phase transition is the abrupt change of one or more physical properties of a system due to a change in temperature. The icon example is water freezing at 32° F or boiling at 214° F. Such a phase transiton may be temporarily halted under certain conditions. Water e.g. does not freeze if the decrease in temperature occurs swiftly. It's only when the persistent melting energy is released that it turns suddenly to ice. It is this particular aspect of a phase transition which the inflation theory is applying to the Universe along with concept of false vacuum

According to the inflation theory the Universe until T=0 is seen like a minute ensemble of a scalar field located on the plateau of an energy field. The plateau is surrounded by a trough of minimum. The ensemble is possibly governed by the laws of a Grand Unified Theories. The Universe is at an equilibrium point. At T=0 the equilibrium is broken by quantum fluctuations as the false vacuum dumps into the Universe a tremendous energy. It's the beginning of the Big Bang. The phase transition the Universe should endure is halted due to the scalar field' energy not being able to be lowered quickly. The strong force does not split immediately as it should. The scalar field acts like a suction. It creates a gravitational field. It contains a anti-gravitational force at the same time. Bubbles of real void appear inside the false void. As they have a positive gravity opposed to the scalar field's tremendous anti-gravitational forces, such bubbles enter an inflationary expansion. In the blink of an eye, the Universe passes from a size barely above the Planck size (the Universe is about 10^-24 m), to about the size of the current orbit of Pluto, increasing by a factor 10²⁴. As the temperature drops to 3° K (about -456°.F --270°.C), the false void energy evaporates (it turns into photons, into light) and the inflation stops. The Universe is now as wide at 1/5th of a light-year. The strong force eventually can split from the electroweak force. At 10^-32 second the usual laws of the Standard Model are back, instead of the more primitive forces at work until then

As far as monopoles are concerned, the delay brought by the false vacuum to the split of the forces' unity has as a consequence that they have not time enough to form in enough quantity. As the phase transition eventually happens, it happens at characteristics at which the generation of monopoles is not possible. The phase transition of the Universe results into the second split of its fundamental forces

Conclusion

As Alan Guth expressed it himself in 1997 the Big Bang theory was the theory of the aftermath of a bang, the theory of how the early Universe expanded and cooled as the Big Bang theory "[was not even giving] a clue about what banged, what caused it to bang, or what happened before it banged". The inflation adresses the fundamental question of what physics governed the explosion. The inflation theory brings solutions to some classical paradoxes of the original Big Bang: the inflation is an answer to the question of the curvature of the Universe. The present Universe is more or less flat. W is near the critical value of density. The inflation widened the Universe by such an amount that the Universe became flattened at the end of the process whatever its curvature might have been at the beginning. On the other hand whatever any possible discrepancy from the critical value of density might have existed, the characteristics of the scalar field had it stay like it was despite the enormous increase in size, as a normal expansion of the Universe would have increased it. The inflation is an answer too to the question of the homogeneity of the Universe. The cosmic microwave background (CMB) is homogeneous. This means that all regions of the Universe endured the same conditions and that a usual cooling led to a homogeneous temperature. The Universe tremendous, cohesive, and swift increase in size gave the same characteristics to regions distant from each other in a way than even light never had a chance to link them as an homogeneous temperature was reached through an usual cooling before the inflation. A last point -the imbalance matter-antimatter- is answered too by inflation. Universe is almost only made of matter (antimatter scores only at 0.01%). This is easily explained by the fact that the split between the strong force and the electroweak force at the end of the inflation produced massive bosons and their anti-particles. Such X-bosons are decaying into quarks more quickly than their anti-X-bosons do turn into anti-quarks (this phenomenon is called violation of the CP symmetry). Thus a greater number of quarks eventually remained hence as a greater amount of matter, as these remaining quarks formed protons and neutrons, these bases for the atoms' nuclei. Eventually the scalar field model is another good explanation for the filamentary net of the present Universe. The false vacuum pouring into the energy trough oscillated randomly bringing additional energy in some parts of it. These inhomogeneities were expanded in the inflation process providing the nodes where gas clouds aggregated later, forming the first clumps of stars and galaxies. More generally, most recent observations of the Universe all go in the direction that the inflation theory is true

Another major direction where the inflation theory is heading is the one of the bubble-universes -the multiverse. Building on this idea that there is a Universe before the Universe, this energy field where the vacuum field is standing, Guth himself, as other scientists like Andrei Linde, think that the inflationary process did not occur once only. It surely created other expanding bubbles of real void which turned into separated universes. The main questions are to know whether such bubbles are connected or disconnected, or whether such bubbles work according the same laws of physics. Such bubbles are seen too like having in turn generated new inflationary processes leading to a fractal universe where bubble-universes are continually being born from each other. Some goes up to think that the expansion of some real void bubbles was such that what is called Universe by dwellers of parts of them is just a minute part of such gigantic bubbles. The accelerating expansion of our Universe since 7 billion years due to the dark energy might well be an inflation as Vilenke and Linde are stressing that in such mushrooming Universes inflation is carving at minute scales conditions for future inflations