Type IIB flux compactifications on twistor bundles

We construct a U(1) bundle over N(1,1), usually considered as an SO(3) bundle over CP^2, and show that type IIB supergravity can be consistently compactified over it. With the five form flux turned on, there is a solution for which the metric becomes Einstein. We also turn on 3-form fluxes and show that there is a one parameter family of solutions. In particular, there is a limiting solution of large 3-form fluxes for which two U(1) fiber directions of the metric shrink to zero size. We also discuss compactifications over N(1,1) to AdS_3. All solutions turn out to be non-supersymmetric.Comment: 12 pages, typos fixed, minor correction

Supersymmetric D3-branes in Five-Form Flux

We consider multiple Euclidean D3-branes in a specific supergravity solution, which consists of a self-dual 5-form RR field in a flat background. We propose a deformation of ${\cal N}=4$ SYM action describing the dynamics of D3-branes in this background. We look at the supersymmetries of ${\cal N}=4$ SYM theory consistent with those preserved by the background. We derive the Chern-Simons action induced by the RR field, and show that the whole action can be supersymmetrized. This we do by deforming the supersymmetry transformations and using the BRST-like characteristic of the unbroken supercharges.Comment: 13 pages, latex file, minor changes, refs. adde

On the stability of non-supersymmetric supergravity solutions

We examine the stability of some non-supersymmetric supergravity solutions that have been found recently. The first solution is AdS_5 X M_6, for M_6 an stretched CP^3. We consider breathing and squashing mode deformations of the metric, and find that the solution is stable against small fluctuations of this kind. Next we consider type IIB solution of AdS_2 X M_8, where the compact space is a U(1) bundle over N(1,1). We study its stability under the deformation of M_8 and the 5-form flux. In this case we also find that the solution is stable under small fluctuation modes of the corresponding deformations.Comment: 11 page

Nonanticommutative Deformation of N=4 SYM Theory: The Myers Effect and Vacuum States

We propose a deformation of ${\cal N}=4$ SYM theoery induced by nonanticommutative star product. The deformation introduces new bosonic terms which we identify with the corresponding Myers terms of a stack of D3-branes in the presence of a five-form RR flux. We take this as an indication that the deformed lagrangian describes D3-branes in such a background. The vacuum states of the theory are also examined. In a specific case where the U(1) part of the gauge field is nonvanishing the (anti)holomorphic transverse coordinates of the brane sit on a fuzzy two sphere. For a supersymmetric vacuum the antiholomorphic coordinates must necessarily commute. However, we also encounter non-supersymmetric vacua for which the antiholomorphic coordinates do not commute.Comment: 14 pages, minor changes, refs. adde

N=1/2 Super Yang-Mills Theory on Euclidean AdS2xS2

We study D-branes in the background of Euclidean AdS2xS2 with a graviphoton field turned on. As the background is not Ricci flat, the graviphoton field must have both self-dual and antiself-dual parts. This, in general, will break all the supersymmetries on the brane. However, we show that there exists a limit for which one can restore half of the supersymmetries. Further, we show that in this limit, the N=1/2 SYM Lagrangian on flat space can be lifted on to the Euclidean AdS2xS2 preserving the same amount of supersymmetries as in the flat case. We observe that without the C-dependent terms present in the action this lift is not possible.Comment: 12 pages, latex file; v2: minor corrections, references adde

Comments on Gluino Condensates in N=1/2 SYM Theory

Using Ward identities of N=1/2 supersymmetric Yang-Mills theory, we show that while the partition function and antichiral gluino condensates remain invariant under the $C$ deformation, chiral gluino correlators can get contributions from all gauge fields with instanton numbers $k\leq 1$. In particular, a Ward identity of the $U(1)_R$ symmetry allows us to determine the explicit dependence of chiral gluino correlators on the deformation parameter.Comment: 11 pages, 4 figures, small changes, added a referenc

New Compactifications of Eleven Dimensional Supergravity

Using canonical forms on S^7, viewed as an SU(2) bundle over S^4, we introduce consistent ansatze for the 4-form field strength of eleven-dimensional supergravity and rederive the known squashed, stretched, and the Englert solutions. Further, by rewriting the metric of S^7 as a U(1) bundle over CP^3, we present yet more general ansatze. As a result, we find a new compactifying solution of the type AdS_5\times CP^3, where CP^3 is stretched along its S^2 fiber. We also find a new solution of AdS_2\times H^2\times S^7 type in Euclidean space.Comment: 15 pages, revised sec. 4, included new CP^3 and S^7 compactifications, published versio

On Instantons and Zero Modes of N=1/2 SYM Theory

We study zero modes of N=1/2 supersymmetric Yang-Mills action in the background of instantons. In this background, because of a quartic antichiral fermionic term in the action, the fermionic solutions of the equations of motion are not in general zero modes of the action. Hence, when there are fermionic solutions, the action is no longer minimized by instantons. By deforming the instanton equation in the presence of fermions, we write down the zero mode equations. The solutions satisfy the equations of motion, and saturate the BPS bound. The deformed instanton equations imply that the finite action solutions have U(1) connections which are not flat anymore.Comment: 9 pages, latex file, added references, minor change