Supergravity is the idea that launched a thousand theories. This hypothesis suggests that the particle that causes gravity ought to have a partner, and from聽this idea聽came a possible way to solve some of the biggest mysteries in physics聽鈥� from unifying gravity with quantum mechanics to explaining the effects of dark matter.
The three scientists that formulated supergravity聽鈥� Sergio Ferrara, Daniel Z. Freedman and Peter van Nieuwenhuizen聽鈥� have been awarded the $3 million Special Breakthrough Prize in Fundamental Physics in recognition of their work. This is the fifth such prize that has been awarded. 快猫短视频 spoke with Peter van Nieuwenhuizen.
What is supergravity?
Supergravity is a combination of general relativity with the idea of supersymmetry, which is a symmetry between the two kinds of particles we see in nature, bosons and fermions. In supersymmetry, every boson should have a partner particle that is a fermion, and every fermion should have a partner boson. General relativity predicts a particle called the graviton, which is a boson, and supergravity adds another particle called the gravitino, a fermion, to be its superpartner. The gravitino has quantum properties that general relativity alone does not have.
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Where does the idea of supergravity come from?
Supergravity is an extension, but not a replacement, of Einstein鈥檚 theory of general relativity. A聽significant outstanding problem in physics has always been to unify quantum mechanics and relativity. That happens in supergravity.
What does it have to do with string theory?
String theory is an extension of supergravity in which the elementary particles are not points but little pieces of wire. Supergravity is聽the low-energy limit of string theory, so if you ever want to do experiments you have to go back to the real world and low energy, and that鈥檚 supergravity. Nowadays, supergravity and string theory are the same thing.
Are there any other problems that supergravity could solve?
Some people speculate that dark matter may consist of the supersymmetric partners of the graviton, the gravitino. If gravitinos can solve this riddle of dark matter it would be a great achievement.
Nobody has found any supersymmetric partner particles yet, including the gravitino. Does that bother you?
My hope is that there will be another larger collider in China, and also that the mass of the supersymmetric particles will be in the range that the next collider is making discoveries. If we do not find these particles, supergravity will survive as a tool to help with other calculations in physics and mathematics, but what is more important to me is physical reality. If it is not a theory of physical reality I will be very disappointed.
Were you excited to find out that you won the Breakthrough prize? Do you have any plans聽for the prize money?
When Edward Witten聽[chair of the selection committee] called, I was nervous that he was going to ask me a hard question about supergravity that I couldn鈥檛 answer. But instead he said, 鈥淚 am happy to inform you that you have won the Breakthrough Prize 2019.鈥� I was speechless. I haven鈥檛 thought much about what I鈥檓 going to do with it yet. I haven鈥檛 had much time. I am 80 years old, I still work, I still teach graduate courses that I love, and that is my life.
