2nd quantisation is a mathematical technique used in quantum mechanics to describe the behavior of particles as waves rather than individual point-like objects. In the WDW (Wheeler-DeWitt) equation, it is used to describe the evolution of a quantum state in a closed system.
2nd quantisation is important because it allows us to describe the behavior of particles in a more accurate and comprehensive way. It takes into account the quantum nature of particles and their interactions, which is crucial in understanding the behavior of systems at the microscopic level.
In 1st quantisation, particles are described as point-like objects with definite positions and momenta. In 2nd quantisation, particles are described as wave-like objects with a probability distribution of positions and momenta. Additionally, in 2nd quantisation, particles can interact with each other, whereas in 1st quantisation, particles are treated as independent entities.
2nd quantisation has various applications in the WDW equation, such as in the study of quantum field theory, quantum gravity, and cosmology. It is also used in condensed matter physics to describe systems with a large number of particles, such as superconductors and superfluids.
No, 2nd quantisation is not applicable to all systems. It is most useful in systems with a large number of particles, such as atoms, molecules, and solids. It is also not applicable to systems with strong interactions or high energies, such as black holes.