Zhao, Xiaomei2010-06-292010-06-292010-06-292010http://hdl.handle.net/10012/5284The ring of polynomials over a finite field has many arithmetic properties similar to those of the ring of rational integers. In this thesis, we apply the Hardy-Littlewood circle method to investigate the density of rational points on certain algebraic varieties in function fields. The aim is to establish asymptotic relations that are relatively robust to changes in the characteristic of the base finite field. More notably, in the case when the characteristic is "small", the results are sharper than their integer analogues.enthe circle methodfunction fieldsexponential sumsmean value estimatesDoctoral ThesisPure Mathematics