Yang-Mill's Theory is one of the Millennium Problems that the Clay Institute has endowed with one million dollars. Yang-Mill's theory deals with quantum theory and has been confirmed in many experiments, although it assumes that quantum particles moving at the speed of light have a mass. According to Einstein, photons or quanta have rest mass zero, he left open whether and to what extent they have a mass.
According to the Conservation of mass, both in nuclear fission and nuclear fusion, in which gamma rays are created that move at the speed of light, as well as in the annihilation of the electron and its antiparticle positron, photons and thus quanta have mass. The mass of a quantum particle is calculated from the relationship between rest mass and mass according to Einstein. The mass is therefore the rest mass divided by the relativistic root. The relativistic root, in turn, is the root of 1 minus the quotient of the square of the speed and the square of the speed of light. For particles moving at the speed of light, the relativistic root becomes 0. The rest mass is also zero, so the mass of a quantum particle is 0 / 0. According to previous mathematics, this is not defined. In particular, the obvious assumption that 0/0 = 1, just like every other real number is by itself 1, does not work with the previous definition of zero. A simple counter-proof would be 2 * 0 = 0 = 1 * 0. If you divide this equation by 0 and assume that 0/0 = 1, the result is that 2 = 1, which of course is a contradiction. However, if you redefine 0 by using the factor as an index, you can divide by zero. This idea is analogous to those of imaginary numbers, the roots of negative numbers. 2 * 0 is then no longer equal to 0 but equal to 0 (2). Accordingly, the conventional counter-evidence against the presumption that 0/0 = 1 fails. You can read more at the Division by Zero. With this redefinition of the number 0, you can see that the mass of a quantum particle is 0/0 = 1. So the particle that moves with the highest speed a particle can reach has the elemental mass. Accordingly, Yang-Mill's theory is confirmed and the problem is not really a problem.