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How Did The Grand Unified Theory and Inflation Save Cosmology?

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

One of the most successful developments in all of science is the Standard Model for particle physics, but it has some issues. For one, over 19 parameters are needed in the equations governing them. Another sore point is how gravity is not explained at all, for it has no particle but as we currently understand it is just a result of mass interacting with space time. Gravity is unlike the other three forces in this regard, for they can be tied together while gravity has thus far remained elusive. But a step in the direction of figuring it out would be the Grand Unified Theory (GUT) (Kaku 83-4).

Though this, quarks and leptons would be the same type of object, and the force carriers (W/Z Bosons, gluons, and photons) as also some form of one another, all of this being the case in the distant past when temperatures were high enough to permit this symmetry. Note that this is only for 3 of the 4 forces, with gravity being the odd man out still. But with GUT it may be possible to see how gravity fits into this, for the early Universe went through a phase transition after the Big Bang that broke the 4 forces from being in one just 10-30 seconds post Big Bang and it had the high temperatures needed for GUT to be applicable. That phase transition caused a release of energy into what was at the time the lowest energy state possible: a true vacuum. Anyone willing to bet a false one exists too? It does, and it was the state of the Universe when the 3 particle-based forces (and therefore GUT) were as one. As the transition from false to true vacuum occurred and energy was released, Alan Guth realized that this would drive the Universe to expand exponentially. This became known as inflation, and through the exploration of this idea several universal problems would be resolved (Kaku 84-5, Krauss 64-5).

Monopole problem.

Monopole problem.

The Monopole Problem

One of the implications that GUT entails is that the Universe should be full of monopole magnets, where only a north or a south pole should exist. As you know from experience, none have been found but maybe that’s because they are elsewhere in the Universe. But no searches of the sky have turned them up. Inflation can fix this though, for as the Universe inflated and went from a false vacuum to a true vacuum, the monopoles were spread out to the point of making their detection nearly impossible (86).

Flatness Problem.

Flatness Problem.

The Flatness / Fine Tuning Problem

The shape of spacetime is a critical factor to the growth of the Universe. It can impact the rate of growth and the properties we see around us. The critical density of the Universe to make it flat (which is what observations show it to be) should be 1, but relativity says it should go to 0 and either be a saddle-point or a spherical shape. A lot of time has passed since the Big Bang, so the likelihood of this being a normal discrepancy is low. In fact, if the flatness we see today is real, then the critical density of the Universe had to be 1.00000000000000 just 1 second after the Big Bang. That is simply amazing and seems to imply some fine tuning of our Universe, but it is actually a natural consequence of inflation. The sudden expansion of the Universe would flatten out the shape of the Universe, eliminating the need for some crazy explanation (Kaku 87, Krauss 61).

The Horizon Problem

Related to the issue of flatness is the homogenous nature of the Universe. On large scales, different portions of the Universe are practically the same in structure and the cosmic microwave background (a relic of the early Universe) shows a consistent temperature with deviations less than a thousandth of a degree. But a sneaky problem exists here, for the Universe is limited in terms of information transference. Nothing in space time can travel faster than the speed of light, so how do these vast regions of the Universe look so similar if they are too far apart for such commonality to arise? Inflation offers a way, for it cause that spacetime to accelerate faster than the speed of light, and nothing is wrong with that. The physical space itself can move at any speed but things inside it cannot go beyond the speed of light. And so, the different regions were much closer in the past, were flattened out and made rather uniform as inflation occurred (Kaku 88, Krauss 61).

More problems were resolved by this merging of GUT and inflation, and who knows what else it may uncover…

Works Cited

Kaku, Michio. Parallel Worlds. Doubleday, New York 2005. 83-8. Print.

Krauss, Laurence M. “A Beacon from The Big Bang.” Scientific American Oct. 2014: 61, 64-5. Print.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2019 Leonard Kelley