Susskind on supersymmetry vs. cosmological constant?

However, in our universe supersymmetry is slightly broken, sothe cosmological constant is small but nonzero.In summary, Susskind claims that bosons have a positive contribution to the cosmological constant while fermions have a negative contribution. This leads to the conclusion that if supersymmetry is present, the cosmological constant is zero. However, in our slightly broken universe, the cosmological constant is small but nonzero. This theory is based on supergravity, which is a combination of supersymmetric quantum field theory and gravity.
  • #1
haael
539
35
In one book of Susskind I found the following claim and I wanted to ask for its basis.

Susskind says that each kind of boson gives positive contribution to the cosmological constant (the lighter, the better). Each kind of fermion gives negative contribution to the cosmological constant. Thus, if supersymmetry holds, then the cosmological constant is zero.

In our universe supersymmetry is slightly broken, so the cosmological constant is small but nonzero.

Could you point be to a theory this thesis is based on? I guess this will be the string theory as it involves QFT and gravity.
 
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  • #2
Supersymmetric QFT and gravity together make a theory called supergravity, which can be formulated independently of string theory.
 
  • #3
Interesting. I had never heard that exact claim made before in that way.
 
  • #4
It is based on a naive calculation of the quantum vacuum in supergravity with mattercouplings. For exact SUSY (where the masses of the superpartners are the same) the loopcontributions cancel.
 

1. What is supersymmetry and how does it relate to cosmological constant?

Supersymmetry is a theoretical concept in physics that proposes a symmetry between particles and forces in the universe. It suggests that every particle in the Standard Model (the current understanding of particle physics) has a "superpartner" with slightly different properties. The cosmological constant, on the other hand, is a term in Einstein's equations of general relativity that describes the energy density of the vacuum of space. Supersymmetry is often proposed as a solution to the fine-tuning problem of the cosmological constant, as it predicts that the vacuum energy should cancel out to a very small value.

2. What is the main argument in Susskind's theory on supersymmetry vs. cosmological constant?

Leonard Susskind, a theoretical physicist, argues that supersymmetry is not a viable solution to the cosmological constant problem. He believes that the fine-tuning of the cosmological constant can be explained by the anthropic principle, which states that the universe is the way it is because it allows for the existence of intelligent life. Thus, the seemingly small value of the cosmological constant is not a result of fine-tuning, but rather a consequence of the existence of life.

3. Is there any evidence for or against Susskind's theory?

Currently, there is no conclusive evidence for or against Susskind's theory. The existence of supersymmetry and its potential role in resolving the cosmological constant problem are still open questions in physics. Some theoretical and experimental studies have suggested that supersymmetry may not be observed at the energy scales currently accessible, but there is ongoing research in this area.

4. How does Susskind's theory impact our understanding of the universe?

If Susskind's theory is correct, it would challenge the current understanding of the universe and the role of supersymmetry in explaining the fine-tuning of the cosmological constant. It would also have implications for other areas of physics, such as the search for new particles and the nature of dark matter. However, more research and evidence are needed to fully understand the implications of Susskind's theory.

5. What are some potential alternative theories to supersymmetry and the cosmological constant?

Some alternative theories to supersymmetry and the cosmological constant include modified gravity theories, which suggest a modification to Einstein's equations of general relativity, and the holographic principle, which proposes that the information in a 3-dimensional space can be described by a 2-dimensional surface. There are also ongoing efforts to reconcile supersymmetry with experimental data and develop new theoretical frameworks that could potentially solve the cosmological constant problem without invoking supersymmetry.

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