Inflation: Hyper Big-Bang

This hypothesis says, basically, that the Universe expanded much faster after the Big-Bang then we had previously thought. In fact, it says it expanded faster than the speed of light (10 to the 26^th power) one hundred- million- billion- billion- billionths of a second after the Big-Bang (we talked about how this is possible in our last article, Big-Bang: Cosmic Evolution), before slowing down to a lower speed, then continually accelerating.

Models

Some examples of the different mathematical variants of inflation include:

Eternal Chaotic Inflation

Most inflationary models predict that when the Universe inflated, it would slow down, to an extent, and then speed up again. However, what makes this particular version unique is that it predicts that inflation never slows down in some areas of the Universe, which continue to expand faster than light. As they expand faster than the speed at which information from the rest of the Universe can reach them, they are isolated and, for all practical purposes, independent Universes.



Most inflationary models predict the number of Universes to grow to infinity, giving rise to a "multiverse".

This is the most popular model as it doesn’t require specific conditions such as an initial high- temperature (which plagued earlier models of inflation), and it can provide a (relatively) realistic explanation for life. Different universes may have different low-energy laws of physics, and therefore only some have the right laws to allow life to exist (such as our own).

Higgs Inflation

This hypothesis states that the mysterious and unheard of “inflaton” particle or field was, in fact, the higgs field. It is technically possible, as the higgs particle has a quantum spin of 0, and the inflaton is theorized to have a quantum spin of 0 as well.

However, it only works if one considers there to be other unknown fields interacting with the Higgs field to be able to overcome the gravitational force (a process known as “minimal coupling”). Whilst minimal coupling is a possible phenomenon, it involves creating hypothetical fields beyond the Standard Model of Physics, which obviously involves making a lot of hypothetical assumptions. Furthermore, if the BICEP2 data truly is correct, it would mean that the Higgs-Inflation (at least in its current form) is too weak to be a real candidate for inflation.



Could the Higgs-Boson particle be the elusive inflaton?

Supergravity Inflation

This hypothesis (like many others) tries to reconcile quantum physics and general relativity by saying that gravity is mediated by a particle called the “graviton”, which has a super-partner particle called the “gravitino”. Super-gravity inflation (unlike super-symmetry inflation) says that super-symmetry is local (only occurs in specific areas), which make it more flexible. The introduction of a super-partner to the graviton also removes some mathematical quirks (such as infinite values). The fact that some versions are expected to produce a 4-dimensional Universe like this on and are possible explanations of M-Theory (the most widely-accepted model of String-Theory, which says all particles are 1 dimensional vibrating strings) is what makes super-gravity inflation, and super-gravity in general, a possible candidate for inflation.

However, it does have its problems. Most super-gravity models predict an expansion rate of the Universe far greater than is currently-observed. Furthermore, many other predictions made by super-gravity inflation are untestable as of yet.

Other Models

These models, whilst being plausible, are largely based in mathematics and are difficult and/or uninteresting to describe in simple words. They are:

·         Natural inflation

·         Hilltop Quartic model

·         Power law inflation

·         R-squared inflation

·         Axion-Monodromy inflation

·         Low-Scale Spontaneous-Symmetry-Breaking Super-Symmetric inflation

Interesting: Some models can actually overlap, with there being examples of chaotic natural inflation and natural inflation based on super-gravity.

So there are the basics of inflation and the different models of it. In the next article we’ll look at the evidence for inflation.