Month: September 2022

REVIVING FORGOTTEN PHYSICS. “The reason for introducing the new formulation will be explained in the final section from the viewpoint to exhibit the contrast between free and interacting quantum fields in regard to their energy-momentum supports which are seldom touched upon (or forgotten) in the common physical discussions about quantum fields.” https://lnkd.in/dpsM58Ep View in LinkedIn

CONSEQUENCES OF FORGETTING. “While this language is very convenient in treating many-body problems in both contexts of relativistic particle physics and of non-relativistic solid state physics, its serious pitfall lies in its “forgetfulness” about the strict restriction on its applicability in physical nature!” https://lnkd.in/dpsM58Ep View in LinkedIn

CARTOON PICTURE. “Since the above simple-minded interpretation of quantum fields in terms of creation and annihilation operators is meaningful only for free fields without interactions, the validity of this vocabulary is at most for the asymptotic fields and states which describe quantum fields approximately only in the remote past or future regimes, respectively, before or after the actual scattering processes.” https://lnkd.in/dpsM58Ep View in LinkedIn

CONSEQUENCES OF CARTOONS. “In solid state physics described by quantum statistical mechanics, another typical non-applicability domain of particle pictures can also be found in the well-known phenomena of phase transitions caused by the instability between two stable thermodynamic phases with different particle pictures, through which the same physical system undergoes drastic changes in material configurations.” https://lnkd.in/dpsM58Ep View in LinkedIn

REAL CONSEQUENCES. “For instance, a phase transition from the normal phase with non-vanishing electric resistance to the superconducting one characterized by the vanishing resistance.” https://lnkd.in/dpsM58Ep View in LinkedIn

CONTEXTUAL IMPORTANCE. “These examples clarify that the on-shell states (abbreviation of “states on-the-mass shell”) described by the creation and annihilation operators are not eternal invariants of a system but variables highly dependent upon the environments in which the relevant physical system is placed.” https://lnkd.in/dpsM58Ep View in LinkedIn

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SYMMETRY BREAKING. “When certain continuous symmetry present in one phase is broken in the other, there arise some massless excitation modes in the broken phase, according to a general theorem called Nambu-Goldstone theorem, as is the case of the phase transition from the normal one with unbroken electromagnetic U(1) to the superconducting one with broken U(1) symmetry.” https://lnkd.in/dpsM58Ep View in LinkedIn

SOFT PHOTONS. “Furthermore, the commitment of electromagnetic field (quantum and/or classical) causes more complications as will be discussed, like the case of infrared divergences, where “infrared soft photons” carrying low energies cause serious divergences through the coupling with the “on-shell states” of charged particles.” https://lnkd.in/dpsM58Ep View in LinkedIn