1. Introduction.
In this course we will study mathematical finance. Mathematical finance is not
about predicting the price of a stock. What it is about is figuring out the price of options
and derivatives.
The most familiar type of option is the option to buy a stock at a given price at
a given time. For example, suppose Microsoft is currently selling today at $40 per share.
A European call option is something I can buy that gives me the right to buy a share of
Microsoft at some future date. To make up an example, suppose I have an option that
allows me to buy a share of Microsoft for $50 in three months time, but does not compel
me to do so. If Microsoft happens to be selling at $45 in three months time, the option is
worthless. I would be silly to buy a share for $50 when I could call my broker and buy it
for $45. So I would choose not to exercise the option. On the other hand, if Microsoft is
selling for $60 three months from now, the option would be quite valuable. I could exercise
the option and buy a share for $50. I could then turn around and sell the share on the
open market for $60 and make a profit of $10 per share. Therefore this stock option I
possess has some value. There is some chance it is worthless and some chance that it will
lead me to a profit. The basic question is: how much is the option worth today?
The huge impetus in financial derivatives was the seminal paper of Black and Scholes
in 1973. Although many researchers had studied this question, Black and Scholes gave a
definitive answer, and a great deal of research has been done since. These are not just
academic questions; today the market in financial derivatives is larger than the market
in stock securities. In other words, more money is invested in options on stocks than in
stocks themselves.
Options have been around for a long time. The earliest ones were used by manu