The fractional electric charge of quarks is a fundamental property of these elementary particles in the framework of the Standard Model of particle physics. The Standard Model describes the fundamental particles and their interactions.
Quarks are the basic building blocks of matter, and they come in six different types or flavors: up, down, charm, strange, top, and bottom. Each quark flavor has an associated electric charge. The up quark has a charge of +2/3, while the down quark has a charge of -1/3. The other quarks also have charges in multiples of 1/3.
The fractional electric charges of quarks might seem puzzling from a classical perspective, where we are used to dealing with whole numbers for electric charge. However, in the realm of quantum mechanics, the concept of fractional charge is perfectly consistent.
The explanation lies in a concept called color charge. Quarks possess an additional property called color charge, which is related to the strong nuclear force that binds them together. Color charge comes in three types: red, green, and blue. However, these "colors" are not the same as what we perceive as colors in our everyday life; they are just names given to the different types of charge.
In a similar way to how electric charge is conserved, color charge must also be conserved in interactions involving quarks. This conservation of color charge is achieved through the exchange of particles called gluons, which are the carriers of the strong force. Gluons themselves carry color charge, allowing them to interact with quarks.
The fractional electric charges of quarks arise due to a combination of their color charges and the way they interact through the exchange of gluons. The observed charges of quarks are the result of a complex interplay between their color charges and the dynamics of the strong force.