We give general intersecting brane solutions without assuming any restriction on the metric in supergravity coupled to a dilaton and antisymmetric tensor fields in arbitrary dimensions D. The result is a general class of intersecting brane solutions which interpolate the non-extreme solutions of type 1 and 2. We also discuss the relation of our solutions to the known single brane solution.

By using the systematic approach of parent action method, we derive one Weyl-noninvariant and two Weyl-invariant actions of bosonic p-branes (p, 2) starting from the Nambu-Goto action, and establish the duality symmetries in this set of four actions. Moreover, we discover a new bosonic p-brane action (including the string theory) and deduce two corresponding Weyl-invariant formulations by proposing a new special parent action. We find that the same duality symmetries as those mentioned above exist in this new set of actions. The new p-brane actions are also briefly analyzed.

Underlying a general noncommutative algebra with both noncommutative co-ordinates and noncommutative momenta in a (1+1)-dimensional spacetime, a chiral boson lagrangian with manifest Lorentz covariance is proposed by linearly imposing a generalized self-duality condition on a noncommutative generalization of massless real scalar fields. A signifi cant property uncovered for noncommutative chiral bosons is that the leftfi and right-moving chiral scalars cannot be distinguished from each other, which originates from the noncommutativity of coordinates and momenta. An interesting result is that Dirac's method can be consistently applied to the constrained system whose lagrangian explicitly contains space and time. The self-duality of the noncommutative chiral boson action does not exist.

Siegel's action is generalized to the D=2(p+1)-dimensional space-time (p even). The investigation of self-duality of chiral p-forms is extended to the momentum frame, using Siegel's action of chiral bosons in two space-time dimensions and its generalization in higher dimensions as examples. The whole procedure of the investigation is realized in the momentum space that relates to configuration space through the Fourier transformation of fields. These actions correspond to non-local Lagrangians in the momentum frame. Their selfduality with respect to dualization of chiral fields is uncovered. The relationship between two self-dual tensors in momentum space, whose form appears similar in configuration space, plays an important role in the calculation, that is, its application realizes the algebraic solution of an integral equation.

The effect of temperature is investigated in the Randall-Sundrum brane-world scenario. It is shown that for a spacetime ansatz motivated by similarity with AdS/CFT correspondence several features of the model, such as its Z2 symmetry, are not maintained at nonzero temperatures.