A working paper, Computational complexity and informational asymmetry in financial products, Sanjeev Arora, Boaz Barak, Markus Brunnermeier, Rong Ge. sheds some light on the complex mathematical models upon which credit default obligations and other derivatives are based.

What Arora et al. prove is not only are many derivative mathematical models impossible to compute, never mind in real time, **because** they require more computing power than the world possesses, the missing information to run a mathematical model is a very good place **to cheat** with.

To understand what CDOs, derivatives are, see this post, complete with video tutorials. For some background on the mathematics behind derivatives, read We Want the Formula and this one on some of the probability functions.

Onto the paper. Firstly this quote:

One of our main results suggests that it may be computationally intractable to price derivatives even when buyers know almost all of the relevant information, and furthermore this is true even in very simple models of asset yields.

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