Supersymmetry
A theoretical symmetry between bosons and fermions, unconfirmed by experiment.
Supersymmetry is a theoretical framework in physics that proposes a fundamental symmetry between bosons, particles with integer spin, and fermions, particles with half-integer spin. In a supersymmetric theory, the equations governing forces and those governing matter are identical. For every known fermion, a bosonic superpartner would exist, and vice versa, with the partner’s spin differing by a half-integer. The names of bosonic partners of fermions are prefixed with “s-”, as in “selectron” for the electron’s superpartner. In the simplest, unbroken supersymmetry, each pair of superpartners would share the same mass and internal quantum numbers; more complex theories with spontaneously broken symmetry allow superpartners to have different masses. The history of supersymmetry began in 1966, when Hironari Miyazawa proposed a broken internal supersymmetry relating mesons and baryons, though this work was largely ignored. It was independently rediscovered in the context of quantum field theory in 1971 by J. L. Gervais and B. Sakita, and by Yu. A. Golfand and E. P. Likhtman, and in 1972 by D. V. Volkov and V. P. Akulov. A consistent graded Lie-algebraic structure arose in 1971 from early string theory work by Pierre Ramond, John H. Schwarz, and André Neveu. In 1974, Julius Wess and Bruno Zumino identified key renormalization features of four-dimensional supersymmetric field theories, leading to early particle physics applications. The first realistic supersymmetric version of the Standard Model, the Minimal Supersymmetric Standard Model (MSSM), was proposed in 1977 by Pierre Fayet to address the hierarchy problem. The term “supersymmetry” was coined by Abdus Salam and John Strathdee in 1974, simplifying “super-gauge symmetry” used by Wess and Zumino. Supersymmetry has applications across quantum mechanics, statistical mechanics, quantum field theory, condensed matter physics, nuclear physics, optics, stochastic dynamics, astrophysics, quantum gravity, and cosmology. Despite extensive experimental searches, no supersymmetric extensions of the Standard Model have been verified, leading some physicists to consider the theory unsupported by evidence.
- field
- Theoretical physics, particle physics
- known_for
- Proposing a symmetry between bosons and fermions, superpartner particles, and extensions of the Standard Model
- key_developers
- Pierre Ramond, John H. Schwarz, André Neveu, Julius Wess, Bruno Zumino, Abdus Salam, Pierre Fayet
- status
- Not experimentally verified; some physicists argue the theory is dead
Lore & Background
Supersymmetry is a theoretical framework proposing a fundamental symmetry between two classes of particles: bosons, which have integer spin, and fermions, which have half-integer spin. In a supersymmetric theory, every known fermion would have a bosonic partner, and every known boson a fermionic partner, known as a superpartner. The spin of a superpartner differs by a half-integer from its counterpart. For example, the electron’s bosonic partner is called the selectron. In the simplest, unbroken supersymmetry, superpartners would share identical mass and internal quantum numbers; in more complex theories, spontaneous symmetry breaking allows them to differ in mass. The names of bosonic partners of fermions are prefixed with “s-”, indicating they are scalar particles. Supersymmetry is a type of spacetime symmetry, and a supersymmetric theory is defined by having identical equations for force and matter. Dozens of such theories exist. The concept first appeared in 1966 in hadronic physics, proposed by Hironari Miyazawa, but was largely ignored. It was independently rediscovered in quantum field theory in 1971 by J. L. Gervais and B. Sakita, Yu. A. Golfand and E. P. Likhtman, and D. V. Volkov and V. P. Akulov, and also arose in early string theory from Pierre Ramond, John H. Schwarz, and André Neveu. In 1974, Julius Wess and Bruno Zumino identified key renormalization features of four-dimensional supersymmetric field theories, leading to early particle physics applications. The term “supersymmetry” was coined by Abdus Salam and John Strathdee in 1974 as a simplification of “super-gauge symmetry.” The first realistic supersymmetric version of the Standard Model, the Minimal Supersymmetric Standard Model (MSSM), was proposed by Pierre Fayet in 1977. Despite extensive experimental searches, no evidence for supersymmetry has been found. If confirmed, it could explain phenomena such as dark matter and the hierarchy problem.
Reader's Guide
Supersymmetry remains a vital part of many proposed theories in physics, with applications ranging from quantum mechanics and statistical mechanics to quantum field theory, condensed matter physics, nuclear physics, optics, stochastic dynamics, astrophysics, quantum gravity, and cosmology. In high-energy physics, a supersymmetric extension of the Standard Model is a possible candidate for physics beyond the Standard Model, but no such extension has been experimentally verified. The mathematical structure of supersymmetry, based on graded Lie superalgebras, has been applied successfully to topics such as nuclear physics, critical phenomena, and statistical physics. However, the lack of experimental evidence has led some physicists to argue the theory is dead, and the Coleman–Mandula theorem's limitations were overcome by the Haag–Łopuszański–Sohnius theorem, which analyzed all possible superalgebras. Supersymmetry's significance lies in its potential to unify spacetime and internal symmetries and to solve problems like the hierarchy problem and dark matter, though it remains unconfirmed.
Did You Know?
- The term 'supersymmetry' was coined by Abdus Salam and John Strathdee in 1974 as a simplification of 'super-gauge symmetry'.
- Multiple experiments on supersymmetry have failed to provide evidence that it exists in nature.
Frequently Asked Questions
Who is Supersymmetry?
Supersymmetry is a theoretical symmetry principle in particle physics that pairs every boson with a fermionic superpartner and every fermion with a bosonic one. It was first proposed in the 1960s–70s by several independent groups, including Miyazawa, Gervais and Sakita, Gol'fand and Likhtman, and Volkov and Akulov.
What are Supersymmetry's powers and role?
Its core function is to extend the Standard Model by introducing a partner particle for each known particle whose spin differs by half a unit. This extension is designed to address open puzzles such as the hierarchy problem and to supply a natural dark-matter candidate in the form of the lightest superpartner.
How does Supersymmetry's story end?
As of now, no experiment—including those at the LHC—has detected any superpartner, so the theory remains unconfirmed. Some physicists have begun arguing that the simplest supersymmetric models are effectively ruled out, though the broader framework has not been formally discarded.
Why is Supersymmetry important?
It offers a mathematically elegant way to stabilize the Higgs mass against quantum corrections and to unify forces, making it one of the most studied extensions of the Standard Model. Even without experimental confirmation, it has driven decades of theoretical progress in string theory, cosmology, and quantum field theory.
Who are Supersymmetry's key developers?
Beyond the original proposers, the framework was shaped in the 1970s by Pierre Ramond, André Neveu, John Schwarz, Julius Wess, Bruno Zumino, Abdus Salam, and Pierre Fayet. Their collective work turned a loose symmetry idea into a full quantum field theory and later into the foundation of superstring theory.
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