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A Sigh is Just A Sigh

I was talking to a graduate student the other day, and he referred me to the “fundamental theorem of finance”.

Isn’t it strange? I thought later, that finance should have a fundamental theorem (and that I wasn’t quite sure what it was). Axiomatic systems have theorems. If you google “the fundamental theory of chemistry” you won’t find much because chemistry isn’t about axioms. Here is what you find if you google “fundamental theorem of arithmetic/algebra/calculus/finance”.

The fundamental theorem of arithmetic states that every natural number greater than 1 can be written as a unique product of prime numbers

The fundamental theorem of algebra states that every polynomial equation of degree n with complex number coefficients has n complex roots.

The first fundamental theorem of calculus states that, if f is continuous on the closed interval [a,b] and F is the antiderivative (indefinite integral) of f on [a,b], then the definite integral of f(x) from a to b is F(b) – F(a).

So far I get it.

Now (wait for it):

Fundamental Theorem of Finance. Security prices exclude arbitrage if and only if there exists a strictly positive value functional, under the technical restrictions that the space of portfolios and the space of contingent claims are locally convex topological vector spaces and the positive cone of the space of contingent claims is compactly generated, that is, there exists a compact set K of X (not containing the null element of X ) such that C = {x ? X : x ? 0} = U ?K for ?>= 0

You must remember this / A kiss is still a kiss / A sigh is just a sigh / The fundamental things apply / As time goes by.

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