Horatiu Nastase

Strings in flat space and pp waves from N = 4 Super Yang Mills

We explain how the string spectrum in flat space and pp‐waves arises from the large N limit, at fixed gYM2, of U(N) N = 4 super Yang Mills. We reproduce the spectrum by summing a subset of the planar Feynman diagrams. We give a heuristic argument for why we can neglect other diagrams.

Strings in flat space and pp waves from Script N = 4 Super Yang Mills

We explain how the string spectrum in flat space and pp-waves arises from the large

Consistency of the AdS7×S4 reduction and the origin of self-duality in odd dimensions

N

The supergravity dual of a theory with dynamical supersymmetry breaking

limit, at fixed

Moduli flow and non-supersymmetric AdS attractors

g^2_{YM}

The fuzzy S 2 structure of M2-M5 systems in ABJM membrane theories

, of U(N)

Comments on gluon 6-point scattering amplitudes in = 4 SYM at strong coupling

{\cal N} =4

Heisenberg saturation of the Froissart bound from AdS-CFT

super Yang Mills. We reproduce the spectrum by summing a subset of the planar Feynman diagrams. We give a heuristic argument for why we can neglect other diagrams. We also discuss some other aspects of pp-waves and we present a matrix model associated to the DLCQ description of the maximally supersymmetric eleven dimensional pp-waves.

On the nonlinear KK reductions on spheres of supergravity theories

We discuss the full nonlinear Kaluza–Klein (KK) reduction of the original formulation of d=11 supergravity on AdS7×S4 to gauged maximal (N=4) supergravity in 7 dimensions. We derive the full nonlinear embedding of the d=7 fields in the d=11 fields (“the ansatz”) and check the consistency of the ansatz by deriving the d=7 supersymmetry laws from the d=11 transformation laws in the various sectors. The ansatz itself is nonpolynomial but the final d=7 results are polynomial. The correct d=7 scalar potential is obtained. For most of our results the explicit form of the matrix U connecting the d=7 gravitino to the Killing spinor is not needed, but we derive the equation which U has to satisfy and present the general solution. Requiring that the expressionδF=dδA in d=11 can be written as δd(fields in d=7), we find the ansatz for the 4-form F. It satisfies the Bianchi identities. The corresponding ansatz for the 3-form A modifies the geometrical proposal by Freed et al. by including d=7 scalar fields. A first order formulation for A in d=11 is needed to obtain the d=7 supersymmetry laws and the action for the nonabelian selfdual antisymmetric tensor field Sαβγ,A. Therefore selfduality in odd dimensions originates from a first order formalism in higher dimensions.

Analyticity for multi-Regge limits of the Bern–Dixon–Smirnov amplitudes

We study the large-N limit of a little string theory that reduces in the IR to U(N) = 1 supersymmetric Yang-Mills with Chern-Simons coupling k. Witten has shown that this field theory preserves supersymmetry if k ≥ N/2 and he conjectured that it breaks supersymmetry if k < N/2. We find a non-singular solution that describes the k = N/2 case, which is confining. We argue that increasing k corresponds to adding branes to this solution, in a way that preserves supersymmetry, while decreasing k corresponds to adding anti-branes, and therefore breaking supersymmetry.