Strings and Conservation of Charge

The electric charge of an electron is in units known as elementary charge. The electric charge of a proton is in the same units. There are two basic properties of electric charge: All electric charges come in integer multiples of this unit and electric charge is conserved. What could be the explanation for both the discreteness of electric charge, as seen in nature, and the conservation law pertaining to charge?

In string theory, where particles are replaced by extended one-dimensional objects called strings, one often considers geometric situations such as the following: there is a loop (a string ) on an infinite cylinder (Fig. 19 ), where the circumference of the cylinder is viewed as an extra dimension (string theory enjoys more than 3-spatial dimensions–the extra ones are believed to be tiny, as we will discuss when we discuss dualities). Such a loop has a characteristic winding number that describes how many times it winds around the cylinder.