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In the first part of this dissertation, we study two different aspects ofstring phenomenology. First we discuss the complementary signals of low masssuperstrings at the proposed electron-positron facilities (ILC and CLIC), ine+e- and {\gamma} {\gamma} collisions. We examine all relevant four-particleamplitudes evaluated at the center of mass energies near the mass of lightestRegge excitations and extract the corresponding pole terms. Secondly, weconsider string realizations of the Randall-Sundrum effective theory andexplore the search for the lowest massive Regge excitation of the gluon and ofthe extra (color singlet) gauge boson inherent of D-brane constructions. Wealso study the ratio of dijet mass spectra at small and large scatteringangles. We show that with the first fb-1 such a ratio can probe lowest-lyingRegge states for masses ~3.0 TeV. Finally, we propose that the 3.2$\sigma$excess at about $140 {\rm GeV}$ in the dijet mass spectrum of $W$ + jetsreproted by the CDF Collaboration originates in the decay of a leptophobic $Z'$that can be related to the U(1) symmetries inherent of D-brane models. In theremaining parts of this dissertation, we discuss several points that may helpto clarify some questions that remain about the anomaly puzzle in N=1supersymmetric Yang-Mills theory and we investigate the issue that the DiracHamiltonian of a spin-1/2 particle in a curved background appears to benon-hermitian.

Anomaly Puzzle, Curved-Spacetime Spinor Hamiltonian, and String Phenomenology