Keywords Abstract 20 years ago a new quantum state of matter was discovered and identified 1,2,3,4,5,6,7. The observed dynamic quantum state of spin precession in super-fluid 3 He-B bears the properties of spin current superfluidity, Bose condensation of spin waves – magnons, off-diagonal long-range order and related phenomena of quantum coherence.

Superconductivity, superfluidity, condensation, cluster formation, etc. are phenomena that might occur in many-particle systems. These are due to residual interactions between the particles. To explain these phenomena consistently in a microscopic approach, at some point, one needs to solve few-body equations that are modified because of the Pauli principle and the interactions of the many part...

20 years ago a new quantum state of matter was discovered and identified 1,2,3,4,5,6,7. The observed dynamic quantum state of spin precession in super-fluid 3 He-B bears the properties of spin current superfluidity, Bose condensation of spin waves – magnons, off-diagonal long-range order and related phenomena of quantum coherence.

Classically identical particles become quantum mechanically indistinguishable. Satyendra Nath Bose taught us, in 1924, how to correctly count the distinct microstates for the indistinguishables, and for a gas of light quanta (later photons), whose number is not conserved, e.g., can vary with temperature, he gave a proper derivation of Planck’s law of black body radiation. Einstein, in 1925, gen...