Is Supersymmetry required by String theory?

In summary: But I would say that, even then, you would need to include some form of supersymmetry in order to make the theory consistent.
  • #1
TheHeraclitus
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TL;DR Summary
Supersymmetry is often mentioned together with String theory, but do all String theories require it?
From what I understood Supersymmetry means there are more particles than we currently know about and they are predicted by (some/all, I do not know) versions of String theory.
Is it so important to String theory or can it work without SUSY?

Thank you!
 
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  • #2
Susy is, as far as we know, required for the particle spectrum to be consistent. Without susy you get e.g. tachyonic particles which are hard to interpret as physical particles. So yes.
 
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  • #3
haushofer said:
Susy is, as far as we know, required for the particle spectrum to be consistent. Without susy you get e.g. tachyonic particles which are hard to interpret as physical particles. So yes.
Non-perturbative formulation of bosonic string-field theory reinterprets tachyonic state as an unstable state, very much like tachyonic Higgs field before symmetry breaking is reinterpreted as an unstable state. By a process of tachyon condenzation the unstable state (local maximum of the potential) settles down into a stable state (local minimum of the potential) and excitations around the stable state are no longer tachyonic. So I would say no.

But we still need susy in string theory because that's the only known way (as fas as I am aware) to incorporate fermions into string theory, and we need fermions because they are observed in nature.
 
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  • #4
I have seen multiple knowledgeable theoretical physicists state authoritatively that supersymmetry is necessary as a low energy approximation of string theory.

To some extent, however, it boils down to definitions.

If you use a fairly strict definition of string theory or M-theory, then this is probably correct.

If you use a loose definition of string theory that, for example, borrows heavily from its mathematical methods without embracing the entire discipline's canonical form for it, perhaps you could get a stringy theory that doesn't have supersymmetry as a low energy approximation.
 

FAQ: Is Supersymmetry required by String theory?

Is Supersymmetry required by String theory?

Supersymmetry is not strictly required by string theory, but it plays a crucial role in making the theory consistent and more manageable. In particular, supersymmetry helps to cancel out certain anomalies and infinities that arise in string theory calculations, making the theory more mathematically consistent.

What is the relationship between Supersymmetry and String theory?

Supersymmetry is a symmetry that relates bosons (force-carrying particles) and fermions (matter particles). In string theory, incorporating supersymmetry leads to "superstring theory," which is a more refined version of string theory. Superstring theory is considered to be more promising because it addresses several theoretical issues that arise in non-supersymmetric versions of string theory.

Can String theory work without Supersymmetry?

While it is theoretically possible to formulate string theory without supersymmetry, such versions are less appealing because they tend to suffer from mathematical inconsistencies and do not provide the same level of predictive power. Supersymmetry helps to eliminate many problematic infinities and anomalies, making superstring theory a more robust framework.

Has Supersymmetry been experimentally confirmed?

As of now, supersymmetry has not been experimentally confirmed. Particle accelerators like the Large Hadron Collider (LHC) have searched for supersymmetric particles, but no definitive evidence has been found yet. The lack of experimental confirmation is one of the key challenges facing both supersymmetry and string theory.

What happens to String theory if Supersymmetry is not found?

If supersymmetry is not found, it would pose a significant challenge to string theory, particularly to superstring theory, which relies heavily on supersymmetry for its internal consistency. However, it would not necessarily invalidate string theory altogether. Theoretical physicists might need to explore alternative versions of string theory or entirely new frameworks to address the inconsistencies that supersymmetry currently helps to resolve.

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