Saturday, 20 July 2013

String Theory

This chapter is an extension to Particle physics. If you have in depth knowledge of String theory, then you may skip this chapter.

This chapter is somewhat complicated to understand. Please go through it twice to understand properly.

For decades, Physicists have tried to figure out the Theory of Everything that would unify all the fundamental forces of nature. One of the most important theories in present time is the String Theory. String theory claims that all the fundamental particles consists of tiny vibrating one dimensional filaments called strings. Many scientist believe that String theory might be the solution to thousands of mystery in the universe one being the relation between Gravity and Quantum Physics.

Strings (one dimensional)
Significance of String Theory

String Theory is still being processed. It is so very difficult to pen down String Theory completely. However here is a glance of it.

1. All objects in our universe are composed of vibrating filaments (strings) and membranes (branes) of energy. Earlier it was believed that only bosons were Strings but it is not believed that Fundamental particles are also Strings.

2. String theory attempts to reconcile general relativity (gravity) with quantum physics.

3. A new connection (called supersymmetry) exists between two fundamentally different types of particles and bosons.

4. Several extra (usually unobservable) dimensions to the universe must exist. If the galaxies are believed to be strings several dimensions are possible (as strings are one dimensional).

5. There are also other possible string theory features, depending on what theories prove to have merit in the future. Possibilities include:

A landscape of string theory solutions, allowing for possible parallel universes (A Universe existing parallel to our own i.e possibility that there would be another person like you reading the same article on Internet at the same time).

The holographic principle, which states how information in a space can relate to information on the surface of that space.

The anthropic principle, which states that scientists can use the fact that humanity exists as an explanation for certain physical properties of our universe.

Our universe could be “stuck” on a brane, allowing for new interpretations of string theory.

Super Partners

Every Fundamental particle has a partner called super partner.

Standard Particle     Superpartner

Higgs boson                Higgsino
Neutrino                     Sneutrino
Lepton                       Slepton
Z boson                     Zino
W boson                   Wino
Gluon                        Gluino
Muon                        Smuon
Top quark                 Stop squark

Various theories in String Theory

String Theory has been given various names during its study such as Bosonic String theory (Basic string theory), Superstring Theory (Advanced extension), M-Theory (not completely same as String Theory) and F-Theory.

From Strings to Superstrings

Earlier only the Force carriers like the photons and fermons were believed to be made of Strings but soon this old ideas were replaced by Superstring Theory. It states that even the fundamental particles are also made up of strings.

By introducing Supersymmetry to Bosonic String Theory, we can obtain a new theory that describes both the forces and the matter which make up the Universe. This is the theory of superstrings. There are three different superstring theories which make sense, i.e. display no mathematical inconsistencies. In two of them the fundamental object is a closed string, while in the third, open strings are the building blocks. Furthermore, mixing the best features of the Bosonic string and the Superstring, we can create two other consistent theories of strings, Heterotic String Theories. Several more theories were introduced and these all were being equally accepted.

However, this abundance of theories of strings was a puzzle: The M-Theory gave the solution.

Extra dimensions

One of the most remarkable predictions of String Theory is that space-time has ten dimensions! At first sight, this may be seen as a reason to dismiss the theory altogether, as we obviously have only three dimensions of space and one of time (You would read later that Time is also a Dimension). However, if we assume that six of these dimensions are curled up very tightly, then we may never be aware of their existence. Furthermore, having these so-called compact dimensions is very beneficial if String Theory is to describe a Theory of Everything.


M-Theory is a major extension to String theory which states that Space Time is actually 11 dimensional which includes 7 Higher Dimensions and 4 common dimensions (i.e Space Time. You will read more about this in the later chapters). M theory, standing for Mother of all String theories, has been developed to take into consideration of all other String Theories. M theory however has not been proved.

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