Stack Of D3-branes Research Articles

Low energy dynamics from deformed conformal symmetry in quantum 4D [formula omitted] SCFTs

We determine the one-loop deformation of the conformal symmetry of a general N=2 superconformally invariant Yang–Mills theory. The deformation is computed for several explicit examples which have a realization as world-volume theories on a stack of D3 branes. These include: (i) N=4 SYM with gauge groups SU( N), USp(2 N) and SO( N); (ii) USp(2 N) gauge theory with one hypermultiplet in the traceless antisymmetric representation and four hypermultiplets in the fundamental; (iii) quiver gauge theory with gauge group SU( N)× SU( N) and two hypermultiplets in the bifundamental representations ( N , N ) and ( N , N ) . The existence of quantum corrections to the conformal transformations imposes restrictions on the effective action which we study on a subset of the Coulomb branch corresponding to the separation of one brane from the stack. In the N=4 case, the one-loop corrected transformations provide a realization of the conformal algebra; this deformation is shown to be one-loop exact. For the other two models, higher-loop corrections are necessary to close the algebra. Requiring closure, we infer the two-loop conformal deformation.

A proposal for lowering the coupling unification scale

In the presence of an external electric field an ensemble of short open strings in equilibrium with the heat bath provided by the Euclidean worldvolume of a stack of D-branes undergoes a continuous transition to a long string phase. The transition temperature is at or below the string scale. We point out that this phenomenon provides a simple mechanism within string theory for the lowering of the strong-electro-weak coupling unification scale by up to two orders of magnitude relative to the string scale.

UV/IR mixing via closed strings and tachyonic instabilities

We discuss UV/IR mixing effects in non-supersymmetric non-commutative U( N) gauge theories. We show that the singular (non-planar) terms in the 2- and 3-point functions, namely the poles and the logarithms, can be obtained from a manifestly gauge invariant effective action. The action, which involves open Wilson line operators, can be derived from closed strings exchange between two stacks of D-branes. Our concrete example is type 0B string theory and the field theory that lives on a collection of N electric D3-branes. We show that one of the closed string modes that couple to the field theory operator which is responsible for the infrared poles, is the type 0 tachyon.

Finite N AdS/CFT correspondence for Abelian and non-Abelian orbifolds, and gauge coupling unification

Although the AdS/CFT correspondence is rigorous only for an infinite N→∞ stack of D3-branes, it can be fruitfully studied for finite N as a source of gauge structures and choices for chiral fermions and complex scalars which solve the hierarchy problem by a conformal fixed point. We emphasize orbifolds AdS5×S5/Γ where the resulting GFT has 𝒩=0 supersymmetry. The fact that the complex scalars are prescribed by the construction limits the possible spontaneous symmetry breaking. Both Abelian and non-Abelian Γ are illustrated by simple examples. An accurate sin2 θ in electroweak unification can be obtained, suggesting that this approach merits further study.

Magnetic susceptibility of mercuric iodide

We consider extensions of the standard model based on open strings ending on D-branes, in which gauge bosons and their associated gauginos exist as strings attached to stacks of D-branes, and chiral matter exists as strings stretching between intersecting D-branes. Under the assumptions that the fundamental string scale is in the TeV range and the theory is weakly coupled, we study models of supersymmetry for which signals of annihilating neutralino dark matter are observable. In particular, we construct a model with a supersymmetric R-symmetry violating (but R-parity conserving) effective Lagrangian that allows for the s-wave annihilation of neutralinos, once gauginos acquire mass through an unspecified mechanism. The model yields bino-like neutralinos (with the measured relic abundance) that annihilate to a γγ final state with a substantial branching fraction (∼10%) that is orders of magnitude larger than in the minimal supersymmetric standard model. A very bright gamma-ray spectral line could be observed by gamma-ray telescopes.