The primary advantage of RQM is that it is possible to develop a consistent mathematical description of a relativistic system that is free of the infinities that are inherent in the Copenhagen interpretation of QM. RQM also makes it possible to calculate radiation and other asymptotic effects that are difficult or impossible to calculate in non-relativistic QM.
The principle of relativity, also known as the relativity principle or second principle, is a cornerstone of modern physics. It postulates that observations and experiments performed in a system of reference frame moving with a uniform velocity through space and time must have the same results as the corresponding observations and experiments in the system in rest. That is, the physics of the two systems must be equivalent if the velocities of the two systems are equal. This principle, first stated explicitly in 1899 by Hendrik Lorentz, implies the equality of the mass of a moving body and its rest-frame mass. The use of the principle of relativity in the study of special relativity is a key distinction between the two areas; the use of the principle of relativity in the study of general relativity is another. Finally, there are also systems in which the velocity is not constant, such as a massless body falling in a gravitational field. As Einstein discovered, the principle of relativity does not apply to these cases.
The Hamiltonian tells us whether the system is in a ground state, or an excited state, and what are the various energy levels of the system. In quantum mechanics, the ground state is the lowest energy state (the vacuum), and the excited states are higher energy states (the excited states are just the excited states that are above the ground state and there is no lower energy state). In a quantum system, there can be only one or no ground state. For the universe, the ground state is the vacuum, and there are excited states if a particle is created from the vacuum, or an excited state if a particle is annihilated from the vacuum. In QFT, the vacuum is the ground state and it is the only state. Therefore, there are no excited states in QFT. A particle in QFT is a composite particle. A particle is a coherent superposition of a field quanta. A field quantum is described by a field operator, and the state of the field quantum is described by a field quantum state, which is a mathematical tool that is used to define a field quantum. A field quantum state is a well defined state of a set of field quanta. In a particle state, the particle is composed of the set of field quanta, and in a field quantum state, the field is composed of the set of field quanta. In other words, a field quantum is a set of field quanta. 827ec27edc