A nonsupersymmetric matrix orbifold

We consider Heterotic string theories in the DLCQ. We derive that the matrix model of the Spin(32)/$Z_2$ Heterotic theory is the theory living on N D-strings in type I wound on a circle with no Spin(32)/$Z_2$ Wilson line on the circle. This is an O(N) gauge theory. We rederive the matrix model for the $\e8$ Heterotic string theory, explicitly taking care of the Wilson line around the lightlike circle. The result is the same theory as for Spin(32)/$Z_2$ except that now there i...

It has been proposed recently that, in the framework of M(atrix) theory, N=8 supersymmetric U(N) Yang-Mills theory in 1+1 dimensions gives rise to type IIA long string configurations. We point out that the quantum moduli space of $SYM_{1+1}$ gives rise to two quantum numbers, which fit very well into the M(atrix) theory. The two quantum numbers become familiar if one switches to a IIB picture, where they represent configurations of D-strings and fundamental strings. We argue ...

We introduce a $N_c\times N_c$ matrix model with $\mathcal{N}=2$ supersymmetries and show its relation to the topological rigid string and the topological YM$_2$. This allows to connect the latter two theories directly. Moreover the construction leads to a new insight in the \ninfty limit. Finally a quantum mechanical matrix theory is proposed which may describe light-cone (light-front) dynamics of gauge fields.

We examine several aspects of the formulation of M(atrix)-Theory on ALE spaces. We argue for the existence of massless vector multiplets in the resolved $A_{n-1}$ spaces, as required by enhanced gauge symmetry in M-Theory, and that these states might have the correct gravitational interactions. We propose a matrix model which describes M-Theory on an ALE space in the presence of wrapped membranes. We also consider orbifold descriptions of matrix string theories, as well as mo...

We study the origins of the five ten-dimensional ``matrix superstring'' theories, supplementing old results with new ones, and find that they all fit into a unified framework. In all cases the matrix definition of the string in the limit of vanishingly small coupling is a trivial 1+1 dimensional infra-red fixed point (an orbifold conformal field theory) characterized uniquely by matrix versions of the appropriate Green-Schwarz action. The Fock space of the matrix string is bu...

After a short introduction to Matrix theory, we explain how can one generalize matrix models to describe toroidal compactifications of M-theory and the heterotic vacua with 16 supercharges. This allows us, for the first time in history, to derive the conventional perturbative type IIA string theory known in the 80s within a complete and consistent nonperturbative framework, using the language of orbifold conformal field theory and conformal perturbation methods. A separate ch...

We show that all supersymmetric Type IIA D-branes can be constructed as bound states of a certain number of unstable non-supersymmetric Type IIA D9-branes. This string-theoretical construction demonstrates that D-brane charges in Type IIA theory on spacetime manifold $X$ are classified by the higher K-theory group $K^{-1}(X)$, as suggested recently by Witten. In particular, the system of $N$ D0-branes can be obtained, for any $N$, in terms of sixteen Type IIA D9-branes. This ...

We pursue the study of the type IIB matrix model as a constructive definition of superstring. In this paper, we justify the interpretation of space-time as distribution of eigenvalues of the matrices by showing that some low energy excitations indeed propagate in it. In particular, we show that if the distribution consists of small clusters of size $n$, low energy theory acquires local SU(n) gauge symmetry and a plaquette action for the associated gauge boson is induced, in a...

I summarize some recent developments in the issue of planar equivalence between supersymmetric Yang-Mills theory and its orbifold/orientifold daughters. This talk is based on works carried out in collaboration with Adi Armoni, Sasha Gorsky and Gabriele Veneziano.

Using free world-sheet fermions, we construct and classify all the N=2, Z2 X Z2 four-dimensional orbifolds of the type IIA/B strings for which the orbifold projections act symmetrically on the left and right movers. We study the deformations of these models out of the fermionic point, deriving the partition functions at a generic point in the moduli of the internal torus T6=T2 X T2 X T2. We investigate some of their perturbative and non-perturbative dualities and construct ne...