Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAspects of Type 0 String Theory
57
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A construction of compact tachyon-free orientifolds of the non-supersymmetric Type 0B string theory is presented. Moreover, we study effective non-supersymmetric gauge theories arising on self-dual D3-branes in Type 0B orbifolds and orientifolds.
rate research
Read More
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 Harveys recent description of the worldvolume theory of the M2-branes in terms of a Bogomolnyi equation, and its solution via a fuzzy (three-) funnel. Tests of the consistency of this picture are then performed and many of the issues with it are addressed. This is followed by a discussion of how a refinement of the fuzzy three-sphere algebra used can lead to the correct $N^{3/2}$ scaling of degrees of freedom for this system. A reduction of this Basu-Harvey picture to the D1-string picture of the D1-D3 intersection is then performed via constructing a reduction of the fuzzy-three sphere to the fuzzy two-sphere. The second part of the dissertation describes how a holomorphic factorisation argument can be used to demonstrate quantum equivalence of the doubled formalism of string theory with the standard formalism by deriving the partition function, including instanton and oscillator sectors.
The $Z_2times Z_2$ heterotic string orbifold gives rise to a large space of phenomenological three generation models that serves as a testing ground to explore how the Standard Model of particle physics may be incorporated in a theory of quantum gravity. Recently, we demonstrated the existence of type 0 $Z_2times Z_2$ heterotic string orbifolds in which there are no massless fermionic states. In this paper we demonstrate the existence of non--supersymmetric tachyon--free $Z_2times Z_2$ heterotic string orbifolds that do not contain any massless bosonic states from the twisted sectors. We dub these configurations type ${bar 0}$ models. They necessarily contain untwisted bosonic states, producing the gravitational, gauge and scalar moduli degrees of freedom, but possess an excess of massless fermionic states over bosonic ones, hence producing a positive cosmological constant. Such configurations may be instrumental when trying to understand the string dynamics in the early universe.
In a recent paper we considered the type 0 string theories, obtained from the ten-dimensional closed NSR string by a GSO projection which excludes space-time fermions, and studied the low-energy dynamics of N coincident D-branes. This led us to conjecture that the four-dimensional SU(N) gauge theory coupled to 6 adjoint massless scalars is dual to a background of type 0 theory carrying N units of R-R 5-form flux and involving a tachyon condensate. The tachyon background leads to a ``soft breaking of conformal invariance, and we derived the corresponding renormalization group equation. Minahan has subsequently found its asymptotic solution for weak coupling and showed that the coupling exhibits logarithmic flow, as expected from the asymptotic freedom of the dual gauge theory. We study this solution in more detail and identify the effect of the 2-loop beta function. We also demonstrate the existence of a fixed point at infinite coupling. Just like the fixed point at zero coupling, it is characterized by the AdS_5times S^5 Einstein frame metric. We argue that there is a RG trajectory extending all the way from the zero coupling fixed point in the UV to the infinite coupling fixed point in the IR.
We review the boundary state description of D-branes in type I string theory and show that the only stable non-BPS configurations are the D-particle and the D-instanton. We also compute the gauge and gravitational interactions of the non-BPS D-particles and compare them with the interactions of the dual non-BPS states of the heterotic string, finding complete agreement.
The sum over planar multi-loop diagrams in the NS+ sector of type 0 open strings in flat spacetime has been proposed by Thorn as a candidate to resolve non-perturbative issues of gauge theories in the large $N$ limit. With $SU (N)$ Chan-Paton factors, the sum over planar open string multi-loop diagrams describes the t Hooft limit $Nto infty$ with $Ng_s^2$ held fixed. By including only planar diagrams in the sum the usual mechanism for the cancellation of loop divergences (which occurs, for example, among the planar and Mobius strip diagrams by choosing a specific gauge group) is not available and a renormalization procedure is needed. In this article the renormalization is achieved by suspending total momentum conservation by an amount $pequiv sum_i^n k_i eq 0$ at the level of the integrands in the integrals over the moduli and analytically continuing them to $p=0$ at the very end. This procedure has been successfully tested for the 2 and 3 gluon planar loop amplitudes by Thorn. Gauge invariance is respected and the correct running of the coupling in the limiting gauge field theory was also correctly obtained. In this article we extend those results in two directions. First, we generalize the renormalization method to an arbitrary $n$-gluon planar loop amplitude giving full details for the 4-point case. One of our main results is to provide a fully renormalized amplitude which is free of both UV and the usual spurious divergences leaving only the physical singularities in it. Second, using the complete renormalized amplitude, we extract the high-energy scattering regime at fixed angle (tensionless limit). Apart from obtaining the usual exponential falloff at high energies, we compute the full dependence on the scattering angle which shows the existence of a smooth connection between the Regge and hard scattering regimes.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
