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## Full-Text Articles in Physics

On The Polarization Of Closed Strings By Ramond-Ramond Fluxes, Vatche Sahakian

#### On The Polarization Of Closed Strings By Ramond-Ramond Fluxes, Vatche Sahakian

*All HMC Faculty Publications and Research*

In the Green-Schwarz formalism, the closed string worldsheet of the IIB theory couples to Ramond-Ramond (RR) fluxes through spinor bilinears. We study the effect of such fluxes by analyzing the supersymmetry transformation of the worldsheet in general backgrounds. We show that, in the presence RR fields, the closed string can get `polarized', as the spinors acquire non-zero vevs in directions correlating with the orientation of close-by D-branes. Reversing the argument, this may allow for worldsheet configurationsâ€”with non-trivial spinor structureâ€”that source RR moments.

Closed Strings In Ramond-Ramond Backgrounds, Vatche Sahakian

#### Closed Strings In Ramond-Ramond Backgrounds, Vatche Sahakian

*All HMC Faculty Publications and Research*

We write the IIB Green-Schwarz action in certain general classes of curved backgrounds threaded with Ramond-Ramond fluxes. The fixing of the kappa symmetry in the light-cone gauge and the use of supergravity Bianchi identities simplify the task. We find an expression that truncates to quartic order in the spacetime spinors and relays interesting information about the vacuum structure of the worldsheet theory. The results are particularly useful in exploring integrable string dynamics in the context of the holographic duality.

Holography With Ramond-Ramond Fluxes, Vatche Sahakian

#### Holography With Ramond-Ramond Fluxes, Vatche Sahakian

*All HMC Faculty Publications and Research*

Starting from the non-linear sigma model of the IIB string in the light-cone gauge, we analyze the role of RR fluxes in Holography. We find that the worldsheet theory of states with only left or right moving modes does not see the presence of RR fields threading a geometry. We use this significant simplification to compute part of the strong coupling spectrum of the two dimensional NCOS theory. We also reproduce the action of a closed string in a PP-wave background using this general formalism; and we argue for various strategies to find new systems where the closed string theory ...

The Phases Of 2d Ncos, Vatche Sahakian

#### The Phases Of 2d Ncos, Vatche Sahakian

*All HMC Faculty Publications and Research*

We study the phases of the (1+1)-dimensional Non-Commutative Open String theory on a circle. We find that the length scale of non-commutativity increases at strong coupling, the coupling in turn being dressed by a power of D-string charge. The system is stringy at around this length scale, with dynamics involving an interplay between the open and wrapped closed strings sectors. Above this energy scale and at strong coupling, and below it at weak coupling, the system acquires a less stringy character. The near horizon geometry of the configuration exhibits several intriguing features, such as a flip in the ...

Comments On D Branes And The Renormalization Group, Vatche Sahakian

#### Comments On D Branes And The Renormalization Group, Vatche Sahakian

*All HMC Faculty Publications and Research*

We review the de Boer-Verlinde-Verlinde formalism for the renormalization group in the context of D*p*-brane vacua for *p* < 5. We comment on various aspects of the dictionary between bulk and boundary and relate the discussion to the Randall-Sundrum scenario. We find that the gravitational coupling for the Randall-Sundrum gravity on the D*p*-brane worldvolume is dressed by the c-function of the Yang-Mills theory. We compute the beta function and find the expected uneventful flow prescribed by the classical dimension of the Yang-Mills operator.