# Help understanding textbook on Landau Ginzburg theory

This question is about the Landau Ginzburg of phase transitions which seem to take this classical field theory form.
I don't understand the meaning of the 2nd to last equation
$$b(T) = b'(T -T_c)$$
does that mean b(T) has be redefined in the previous two equations relative to the original definition of ##b(T)##. Does the prime ##\prime## indicate a derivative? Here is the entire case, with ##A## being the free energy of some scalar field m(r), which may be interpreted as magnetization. T is temperature.

## Answers and Replies

It's a coordinate change; both ##b## and ##b'## are functions. Suppose ## f(x) = (x - a)^2 ##. What is ## f(x-a) ## ? Does ##f(x) = f(x-a)## ? If not, can you find ##g(x)## such that ##f(x-a) = g(x) ##?