Heavy Baryon Chiral Perturbation Theory
Encyclopedia
Heavy Baryon Chiral Perturbation Theory (HBChPT) is an effective quantum field theory used to describe the interactions of pions and nucleons/baryons. It is somewhat an extension of Chiral perturbation theory
(ChPT) which just describes the low-energy interactions of pions. In a richer theory one would also like to describe the interactions of baryons with pions. A fully relativistic
Lagrangian
of nucleons is non-predictive as the quantum corrections, or loop diagrams can count as
quantities and therefore do not describe higher-order corrections.
Because the baryons are much heavier than the pions, HBChPT rests on the use of a nonrelativistic description of baryons compared to that of the pions. Therefore, higher order terms in the HBChPT Lagrangian come in at higher orders of
where 
is the baryon mass.
Chiral perturbation theory
Chiral perturbation theory is an effective field theory constructed with a Lagrangian consistent with the chiral symmetry of quantum chromodynamics , as well as the other symmetries of parity and charge conjugation. ChPT is a theory which allows one to study the low-energy dynamics of QCD...
(ChPT) which just describes the low-energy interactions of pions. In a richer theory one would also like to describe the interactions of baryons with pions. A fully relativistic
Theory of relativity
The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....
Lagrangian
Lagrangian
The Lagrangian, L, of a dynamical system is a function that summarizes the dynamics of the system. It is named after Joseph Louis Lagrange. The concept of a Lagrangian was originally introduced in a reformulation of classical mechanics by Irish mathematician William Rowan Hamilton known as...
of nucleons is non-predictive as the quantum corrections, or loop diagrams can count as
quantities and therefore do not describe higher-order corrections.Because the baryons are much heavier than the pions, HBChPT rests on the use of a nonrelativistic description of baryons compared to that of the pions. Therefore, higher order terms in the HBChPT Lagrangian come in at higher orders of
where is the baryon mass.