Related papers: Fractional-Superstring Amplitudes, Multi-Cut Matri…

We study supervertices in six dimensional (2,0) supergravity theories, and derive supersymmetry non-renormalization conditions on the 4- and 6-derivative four-point couplings of tensor multiplets. As an application, we obtain exact…

Scattering amplitudes of the spin-4/3 fractional superstring are shown to satisfy spurious state decoupling and cyclic symmetry (duality) at tree-level in the string perturbation expansion. This fractional superstring is characterized by…

The focus of this thesis is on (1) the role of Ka\v c-Moody (KM) algebras in string theory and the development of techniques for systematically building string theory models based on higher level ($K\geq 2$) KM algebras and (2) fractional…

Motivated by quantum field theory (QFT) considerations, we present new representations of the Euler-Beta function and tree-level string theory amplitudes using a new two-channel, local, crossing symmetric dispersion relation. Unlike…

It has recently been realised that there are supersymmetry-preserving non-relativistic decoupling limits associated with each half-BPS object in String Theory and M-Theory. We argue that, given a $p$-brane and a $q$-brane for which there is…

We consider the low-energy limit of the two-dimensional theory on k M2-branes suspended between a straight M5-brane and a curved M5-brane. We argue that it is described by an N=(2,2) supersymmetric gauge theory with no matter fields but…

We embed the supersymmetry breaking mechanism in N=1 SQCD of hep-th/0602239 in a smooth superstring theory using D-branes in the background R^4 \times SL(2)_{k=1}/U(1) which smoothly captures the throat region of an intersecting NS5-brane…

We study the Type IIA limit of the M theory fivebrane configuration corresponding to N=1 supersymmetric QCD with massless quarks. We identify the effective gauge coupling constant that fits with Novikov-Shifman-Veinshtein-Zakharov exact…

In some models of N=1 supersymmetric SU(M) gauge dynamics (hep-th/9503163 and hep-th/9707244), the tension of a string ending on q external quarks is proportional to sin(pi q/M), q=1,..., M-1. In this paper we calculate the ratios of the…

This talk begins with some history and basic facts about string theory and its connections with strong interactions. Comparisons of stacks of Dirichlet branes with curved backgrounds produced by them are used to motivate the AdS/CFT…

This thesis consists of two parts. In the first part we study some topics in $\mathcal{N}=1$ supersymmeric gauge theory and the relation to matrix models. We review the relevant non-perturbative techniques for computing effective…

We study mass-deformed N=2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)-brane webs in type II string theory using Nekrasov's instanton calculus, secondly,…

The dissertation consists of two parts. The first presents an account of the effective worldvolume description of $N$ coincident M2-branes ending on an M5-brane in M-theory. It reviews Basu and Harvey's recent description of the worldvolume…

We show that string models with low energy supersymmetry which accommodate the fermion mass hierarchy generally give non-universal soft trilinear couplings (A-terms). In conjunction with the apparently large Cabibbo-Kobayashi-Maskawa (CKM)…

Basics of some topics on perturbative and non-perturbative string theory are reviewed. After a mathematical survey of the Standard Model of particle physics and GUTs, the bosonic string kinematics for the free case and with interaction is…

We investigate in detail solutions of supergravity that involve warped products of flat geometries of the type M(p+1) x R x T(D-p-2) depending on a single coordinate. In the absence of fluxes, the solutions include flat space and…

We explore the space of consistent three-particle couplings in $\mathbb Z_2$-symmetric two-dimensional QFTs using two first-principles approaches. Our first approach relies solely on unitarity, analyticity and crossing symmetry of the…

We study the off-diagonal blocks in the M(atrix) model that are supposed to correspond to open strings stretched between a Dp-brane and a Dp'-brane. It is shown that the spectrum, including the quantum numbers, of the zero modes in the…

We identify the 4D field theories living on the world volume of D4 branes in non-supersymmetric type IIA string theory constructions. They are softly broken N=2 SQCD with the breakings introduced through vevs of the auxilliary fields in the…

Recently, Kim, Shiu and Vafa proposed general consistency conditions for six dimensional supergravity theories with minimal supersymmetry coming from couplings to strings. We test them in explicit perturbative orientifold models in order to…