## Remarks on the four fundamental interactions

An interaction is a force or a potential energy between two different particles. So far, we know that there are four fundamental interactions in Nature– the electromagnetism, the gravity, the strong and the weak interactions. The discovery of the four interactions and the development of scientific theories of these interactions have always been an important endeavor of the mankind.

The most fundamental characteristic of a scientific theory for an interaction is that it can provide the interaction potential and force formulas, in agreement with experiments and observations.  Otherwise, the theory is at least incomplete or incorrect.  This fundamental characteristic suggests the following:

1. the Maxwell theory of electromagnetism, the Einstein theory of general relativity, and our field theory appear to be the only scientific theories of fundamental interactions, and

2. all other theories cannot provide strong and weak interaction potentials and force formulas, and are incomplete to be qualified as a scientific theory for the four fundamental interactions.

Two remarks are now in order.

1. The Maxwell theory of electromagnetism is a scientific theory, in which the interaction potential is electromagnetic potential ${A_\mu}$, dictated by the Maxwell equations. Interaction potential and force formulas for an electrically charged particle are the Coulomb formulas, which can be derived from the Maxwell equations.The Einstein theory of gravity, the theory of general relativity (GR), is certainly a scientific theory of the gravitational interaction. In GR, the Riemannian metric represents the basic interaction potentials, and the gravitational force formula including the Newtonian universal law of gravity can be derived from the Einstein gravitational field equations.
2. As mentioned in the previous posts, we have discovered three fundamental principles: 1) the principle of interaction dynamics (PID),  2) the principle of representation invariance (PRI), and 3) the coupling principle of symmetry-breaking (PSB) for unification.We have then derived a number of experimentally verifiable laws of Nature based only on the Einstein principle of general relativity, the gauge symmetry and the above three principles. In particular, among other implications, our theory offers basic interaction potential and force formulas for the weak and the strong interactions.

Tian Ma & Shouhong Wang