PHYSICS : String Theory the GUT ( Grand Unified Theory? )

A little story and description about String Theory

This theory began with the observation that elementary particle resonances (the different energies at which new elementary particles are produced in the colliding beams from particle accelerators in LHC) form regular patterns.

This theory proposes that the fundamental constituent of matter is tiny string vibration,

Yes we learn that every object made from atoms, if we zoom deep into the atom there is nucleus consists of proton and neutron that account of about 99% of particle mass.

So what are protons and neutrons made of?

Yes that’s right, Quark where conventional understanding stop, Quarks is all there is...

Image Source : https://byjus.com/physics/quark/

But String theory says that if we zoom deeper, quarks are made of tiny vibrating strand of string, and basically different vibration frequencies of string yields different particles just like guitar strings vibration on different musical key will produce different sound. a quark is imagined as a string undergoing a different vibrational pattern

the mass and charge of the particle is also determined by how a string vibrates.

Image of vibrational string theory

Back to the story...

By the mid 1970s, measurements of the strong force had deviated from string theory predictions, since then most researchers conclude that string theory had no relevance to the physical universe.

Many physicist felt it was unlikely that it would now prevail as the solution to an even more difficult problem

But in 1984 these two string theorists achieved a major breakthrough. They proved that the equations of string theory were consistent after all.

By the time this equation result spread throughout the physics community, hundreds of researchers had dropped what they were working on and turned their full attention to string theory.

During the decade from 1984 to 1994, many theoretical physicists strove to fulfill string theory’s promise by developing this abstract

There are initially 5 sub-theories of string theories, each of the 5 theories describe the string

Image Source : space.com

The five different string theories all involved strings and how the strings form and vibrates. They also all required our universe to have 10 total spatial dimension including our own 4 dimensions and in all the theories, the ways strings vibrate give rise to the richness of our physical world, from the forces of nature to the building blocks of matter to physical constants themselves.

The five theories are : Type 1, Type IIA, Type IIB, SO(32) heterotic, and E8xE8 heterotic. but eventually these five theories merged into one theory called M-Theory which further requires 11 spatial dimension and some interpretation even perceive there are up to 26 dimensions.

String theory is attractive by its own, for the elegancy of its mathematics and the concept of how strings are elegantly describe the universe we're living in.

The theory make some predictions though :

• The essential assumption as well as a prediction of string theory is that quarks too are not elementary, but rather there are vibrating strings,

• There are extra spatial dimensions. String theory predicts 11 space dimensions included our 4 space-time dimensions.

• These extra dimensions are hidden. They are microscopic, spherical-ish in shape and embedded in space-time itself. they are called Calabi-Yau manifolds.

• The theory also predicts supersymmetry. The idea is that every particle has a corresponding supersymmetric partner. Therefore, every fermion must have a supersymmetric boson partner, and every boson must have a supersymmetric fermion partner.

• Some interpretations of string theory predict the existence of a multiverse, i.e. an arena of an infinite universes. This prediction rises from the fact that the vast number of predicted shapes of Calabi-Yau manifolds(10^500), may each correspond to a different universe.

Image Source : https://blogs.lawrence.edu/

• Gravitons One of the massless particles in string theory has the right properties (zero mass and spin two) to be the graviton, the particle responsible for gravity made up from closed string states.
  

However the theory has some problem being considered as Grand Unification Theory (GUT)

Yes the theory supposed to be the unification theory for General Relativity and Quantum Mechanics but the theory find difficulties on testing its predictions in real-world like the existence of extra-dimension, multiverse and some experiments even found to be disagree with the prediction of string theory.

String theory also has difficulties explaining Dark Energy as the GUT at least things like dark energy shall be given a clue and some mathematical expression derived from the theory also shows inconsistencies

Overall the theoretical proposal seem to be a good candidate for GUT but especially the un-testable prediction is crucial because in order for a theory to be scientifically accepted the validity has to be tested. As for now string theory only remains as candidate but who knows if it gonna make a breakthrough in physics.