The high energy limit of scattering amplitudes in string theory

In this thesis we disscuss the high energy limit of scattering amplitudes in string theory.
To be specific, we focus on the bosonic open string theory. Our result can be immediately
applied to bosonic closed strings, whose amplitudes factorize into open string
amplitudes. It should also be possible to extend our results to superstrings. We will
use the convention that 0 = 1/2.
First we discuss how to calculate scattering amplitudes, and give some examples.
Then we take high energy limit of those amplitudes, we found that there are very simple
relations between independent amplitudes.
In the last chapter, we discuss physical meaning of the relations mentioned above,
and give a comment of another explaination of the simple relation. All of the results
support our hypothesis, that there is a big symmetry hidden in string theory.