Читать книгу String Theory For Dummies - Andrew Zimmerman Jones - Страница 49

Supersymmetry is a principle that says that two types of fundamental particles, bosons and fermions, are connected to each other. The benefit of this type of symmetry is that the mathematical relationships in gauge theory reduce in such a way that unifying all the forces becomes more feasible. (We explain bosons and fermions in greater detail in Chapter 8, while we present a more detailed discussion of supersymmetry in Chapter 10.)

The top graph in Figure 2-2 shows the strengths of the three forces described by the Standard Model modeled at different energy levels. If the three forces met up in the same point, it would indicate that there might be an energy level where these three forces become fully unified into one single force.

Lisa Randall, 2005. Reproduced by permission of HarperCollins Publishers.

FIGURE 2-2: If supersymmetry is added, the strengths of the forces in the Standard Model scale differently with energy, and they may become equal at high enough energy.

However, as the lower graph of Figure 2-2 shows, when supersymmetry is introduced into the equation (literally, not just metaphorically), the three forces meet in a single point. If supersymmetry proves to be true, it’s strong evidence that the three forces of the Standard Model unify at high enough energy.

Many physicists believe that all four forces are a manifestation of the same fundamental laws, which in string theory would be the dynamics of quantum strings. This should be apparent at high energy levels, but as the universe reduced into a lower-energy state, the inherent symmetry between the forces began to break down. This broken symmetry caused the creation of four apparently very different forces of nature.

The goal of a theory of quantum gravity is, in a sense, an attempt to look back in time, to when these four forces were unified into a single structure. If successful, it would profoundly affect our understanding of the first few moments of the universe — the last time the forces joined together in this way.