Microeconomics of GDP Macroeconomists tend to study GDP in terms of macro variables. 

Microeconomists study general equilibrium (among other thinga of course).

Is there theory about the relation between general equilibrium and GDP? Where should I look for this?
Macroeconomics nowadays tend to require microfoundations. As a result, general equilibrium are more of a topic for macro than micro analysis. The dynamic stochastic general equilibrium (DSGE) model and its variants underlie much of macroeconomic analysis nowadays.

Standard texts:


Stokey and Lucas (1989) Recursive Methods in Economic Dynamics
Ljungqvist and Sargent (2004) Recursive Macroeconomic Theory