N=8 Supergravity: Maximal Supergravity Explained

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Discussion Overview

The discussion centers on the concept of N=8 supergravity, particularly why it is referred to as 'maximal supergravity' in four dimensions. Participants explore the definitions, implications, and characteristics of supergravity theories, including their particle content and relationships to higher-dimensional theories.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that maximal supergravities are defined with 32 supersymmetries, questioning the terminology of N=8 supergravity as 'maximal'.
  • Another participant suggests that theories with N>8 contain particles with spin greater than 2, which are not well-defined.
  • A different participant expresses uncertainty about the relationship between the dimensionality of spinors and the number of supercharges, proposing that in four dimensions, the calculation of 4*8=32 may be relevant.
  • There is a request for a list of supergravity theories that includes details on particle content, chiral structure, and their ability to reproduce the standard model, among other characteristics.
  • A repeated request for the same information about supergravity theories indicates a desire for clarification and further discussion on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of N=8 supergravity, with no consensus reached on the validity of the claims regarding particle spins and the characteristics of supergravity theories.

Contextual Notes

Some claims about the properties of supergravity theories, such as finiteness and connections to string theory, remain unresolved and are subject to ongoing research.

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Provided that no particles have spins higher than 2, maximal supergravities are defined to be with supergravities with 32 supersymmetries.
Why is the N=8 supergravity in four dimensions called 'the maximal supergravity'? I am confused now...
Thanks.
 
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Not an expert, but from what I've been told the N>8 supergravity theories always contain particles with spin > 2. And these are not well-defined.
 
Thanks for your reply. However, I am not sure whether it's right.
Another answer, which may be wrong, is that in four dimensions the spinors are 4-dimensional, then one could obtain 4*8=32 for the N=8 case.
But what does it mean, and why Is it in accordance with the 32 real supercharges?
xepma said:
Not an expert, but from what I've been told the N>8 supergravity theories always contain particles with spin > 2. And these are not well-defined.
 
Is there a list of SUGRA theories (in terms of N and D) from which the following information follows
- particle content
- chiral structure
- able to reproduce the standard model (gauge fields, fermion generations, higgs)
- finiteness (I think there are no rigorous proofs but ongoing research programs)
- low-energy limit of some string theory
 
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I simply ask the same questions a second time - hope somebody will read and provide answers - thanks :-)

tom.stoer said:
Is there a list of SUGRA theories (in terms of N and D) from which the following information follows
- particle content
- chiral structure
- able to reproduce the standard model (gauge fields, fermion generations, higgs)
- finiteness (I think there are no rigorous proofs but ongoing research programs)
- low-energy limit of some string theory
 

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