Are there fundamental theories in low energy physics?
Lev Landau once said that “Science consists of more than measurements”. Landau’s intention can be summarised very well as follows. One ought to understand the physics behind the experimental measurements to a certain desired depth.
In this talk, and on this background, I propose to discuss some fundamental theories in the realm of low energy physics, which every student of physics would like to be aware of. Those theories are both phenomenological and microscopic in content. My list will include, among others, the theory of continuous phase transitions, Ginzburg-Landau theory, Landau's theory of Fermi liquids, and the theory of superfluidity in bosonic systems. For many practitioners of these theories who attempt to analyse experiments or compute some properties of materials, I shall highlight some crucial issues and challenges in our understanding of experimental phenomena at a pedagogical level. I shall present a general perspective of how the fundamental understanding of low energy physics has emerged during the past seven decades.