Supersymmetry Part 3

The history of supersymmetry is exceptional. In the past, virtually all major conceptual breakthroughs have occurred because physicists were trying to understand some established aspect of nature. In contrast, the discovery of supersymmetry in the early 1970s was a purely intellectual achievement, driven by the logic of theoretical development rather than by the pressure of existing data.  The history of supersymmetry is unique because it was discovered practically simultaneously and independently by two groups of researchers in different parts of the world. 

Supersymmetry was first proposed by Hironari Miyazawa in 1966, but his work was ignored at the time. In the early 1970s two groups of researchers rediscovered supersymmetry independent of each other. The discovery was made by these groups without any collaboration between them because of political tension between their respective countries at the time. One group in the USSR was exploring the mathematics of space-time symmetry and the other group in the west was trying to add fermions to bosonic string theory.

In the USSR, mathematicians Yuri Gol'fand and E. P. Likhtman wanted to do something exotic with the group theory of space-time symmetries. What Gol'fand and Likhtman ended up with was the group theory of supersymmetric transformations in four space-time dimensions. Using this new type of symmetry they constructed the first supersymmetric quantum field theory. Their work was ignored, both in the Soviet Union and in the West, until years later when supersymmetry was recognized as a major topic of investigation in particle physics. 

In the west, a completely different approach was taken. In 1973 Julius Wess and Bruno Zumino developed a theory of supersymmetry while studying two dimensional dual models. Dual models later came to be known as string theory.

Supersymmetry Part 2

Supersymmetry proposes that there are more elementary particles that are yet to be discovered. According to Supersymmetry every particle in the Standard Model has what is known as a superpartner also referred to as a supersymmetric particle or a super particle. A supersymmetric particle has a lot more mass than its partner particle. Physicists believe that the reason that these supersymmetric particles have not been discovered is that they are too massive to be detected in the particle accelerators of the past. Particle accelerators are machines that smash particles together at high speeds to break them into their constituent particles. Older particle accelerators cannot generate enough energy to approach the speeds needed to produce supersymmetric particles. Physicists are hoping to discover some of the supersymmetric particles with the use of the newer large scale particle colliders such as the Large Hadron Collider in Europe.

Supersymmetry relates the particles that transmit forces to the particles that make up matter. For every boson (particle that transmits a force) there is a corresponding supersymmetric fermion and for every fermion (particle that makes up matter) there is a corresponding supersymmetric boson. The existence of superpartners would double the amount of elementary particles in the Standard Model. Supersymmetry also introduces a new kind of mathematics. In the math that we use in everyday life numbers that are multiplied are commutative. That is to say that the numbers can be swapped with each other on both sides of the multiplication operator and they will still produce the same result; for example A x B = B x A. The math of supersymmetry can have A x B = -A x B or A x A = 0 even if A is not equal to 0. The combination of superpartners and the math of supersymmetry allow the particles in the Standard Model to be shuffled around an interchanged without creating inconsistencies in the equations that are applied to them. 

Supersymmetry is an important element for string theory. Evidence for supersymmetry at high energy would be compelling evidence that string theory is a good mathematical model for nature at the smallest distance scales.