What are the five string theories?

In summary, the five string theories are theoretical frameworks that aim to unify the four fundamental forces of nature: gravity, electromagnetism, strong nuclear force, and weak nuclear force. These theories propose that the fundamental building blocks of the universe are not particles, but rather tiny, vibrating strings. The five string theories are Type 1, Type 1A, Type 2A, Type 2B, and heterotic. Each theory has its own unique characteristics and mathematical equations, but they all share the common goal of explaining the fundamental nature of the universe. Despite their differences, these theories all have the potential to revolutionize our understanding of the universe and provide a unified theory of everything.
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and?
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i can not seem to find any good or relevant information on the five different string theories and how they differ from one another. i know of, and to the best of my ability try to understand 'basic' M-theory but am very strapped for info on the other theories and their specifics. if some one could endulge me i'd be very greatful.[?]
 
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  • #2
Originally posted by and?
i can not seem to find any good or relevant information on the five different string theories and how they differ from one another. i know of, and to the best of my ability try to understand 'basic' M-theory but am very strapped for info on the other theories and their specifics. if some one could endulge me i'd be very greatful.[?]

Well, actually, M-Theory is the combination/unification of the five string theories (along with the introduction of a sixth string theory), through the use of Duality. A good resource on this is Brian Greene's The Elegant Universe.
 
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OK, what ARE the six theories and their properties? I'd like to receive as much info as possible so i can better my understanding of M-theory and the unification model.
 
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To speak properly, they are not string theories, but superstring theories. Type I is the only that admits both closed and open strings, while the other 4 (Type IIA, type IIB, heterotic SO(32) and heterotic E8XE8) admit only closed strings. Each of the 5 superstring theories lives in a different background space.Theories related through the T-duality are the two heterotic between them, and the two type II between them. Theories related through the S-duality are Type I with heterotic SO(32), and Type IIB with itself. If you compactify M-theory in a circle (with some additional conditions) you get superstring theory type IIA, and if you compactify M-theory in a line (with some additional conditions)you get heterotic E8XE8
Heterotic E8XE8 is special in the sense that is the only that postulates the existence of a twin universe of ours called shadow universe or hidden sector. The only interaction permitted between the two universes is the gravitational interaction
If this is not enough ask for more :wink:
 
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good enough:wink:
 
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"and?", as I mentioned before, The Elegant Universe is a very good resource for learning about superstring theories. I highly recommend it.
 

1. What is string theory?

String theory is a theoretical framework in physics that seeks to explain the fundamental nature of particles and their interactions. It proposes that particles are not point-like objects, but rather tiny vibrating strings.

2. How many string theories are there?

There are five string theories currently being studied: type I, type IIA, type IIB, heterotic SO(32), and heterotic E8 x E8. These theories are all different formulations of string theory, each with their own unique properties and predictions.

3. What are the differences between the five string theories?

The five string theories differ in the number of dimensions they propose, the types of particles they predict, and the symmetries they exhibit. For example, type I theory is the only one that includes open strings, while the heterotic theories incorporate additional dimensions.

4. How are the five string theories related?

The five string theories are believed to be different limits of a single underlying theory called M-theory. In certain scenarios, the five theories can be connected through a process called duality, where two theories are equivalent in certain limits.

5. What are the implications of string theory?

If string theory is proven to be correct, it would provide a unified framework for understanding all of the fundamental forces of nature, including gravity. It could also potentially reconcile quantum mechanics and general relativity, two theories that currently do not work together.

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