Superconformal Chern-Simons Theories and Their String Theory Duals

In this thesis, we consider two aspects of the conjectured gauge theory/string theory correspondence between three-dimensional maximal supersymmetric conformal field theories, which describe the world-volume theory of multiple M2-branes in flat space, and M-theory on AdS4 x S7.;First we study three classes of N = 6, 8 superconformal Chern-Simons theories that are related to the gauge theory side of the correspondence: the Bagger-Lambert (BL) theories based on 3-algebras, the Lorentzian signature 3-algebra theories, and the Aharony-Bergman-Jafferis-Maldacena (ABJM) theories. We verify the superconformal symmetry of the BL theory, prove that it is parity conserving and conjecture the (by now proven) uniqueness of its SO(4) realization. We then consider the Lorentzian signature 3-algebra theories and show that although the ghosts can be removed to ensure unitarity by gauging certain global symmetries, the resulting theories spontaneously break the conformal symmetry and reduce to maximally supersymmetric three-dimensional Yang-Mills theories. After this, we recast the ABJM theory in a form for which the SU(4) R-symmetry of the action is manifest; then we use this form to verify in complete detail the OSp(6|4) superconformal symmetry of the theory and to express the scalar potential as a sum of squares.;Next, we study the one-loop correction to the energy of a point-particle and circular string solutions to type IIA string theory on AdS 4 x CP3. We compute the spectrum of fluctuations for each of these solutions using two techniques, known as the algebraic curve approach and the world-sheet approach. We propose a new prescription for computing the one-loop corrections that gives well-defined results and agrees with the predictions of the all-loop Bethe ansatz for our point-particle and circular string solutions as well as for previous folded-spinning string solutions.