Related papers: Superspace formulations of the (super)twistor stri…
We describe D=4 twistorial membrane in terms of two twistorial three-dimensional world volume fields. We start with the D-dimensional p-brane generalizations of two phase space string formulations: the one with $p+1$ vectorial fourmomenta,…
Closed super (p+2)-forms in target superspace are relevant for the construction of the usual super p-brane actions. Here we construct closed super (p+1)-forms on a {\it worldvolume superspace}. They are built out of the pull-backs of the…
We review the salient features of spacetime and worldvolume supersymmetric super p-brane actions. These are sigma models for maps from a worldvolume superspace to the target superspace. For p-branes, the symmetries of the model depend…
The twistor superstring, which describes N=4 super Yang-Mills trees, is taken off-shell (for loops) by generalizing Penrose twistors (which describe on-shell momenta) to Atiyah-Drinfel'd-Hitchin-Manin twistors (which include the usual…
We extend the non-perturbative time-dependent bosonic string action of [3] to a N=1 supersymmetric world sheet action with graviton background, and assume a superpotential, function of the time super coordinate.
In this thesis, two aspects of string theory are discussed, tensionless strings and supersymmetric sigma models. The equivalent to a massless particle in string theory is a tensionless string. Even almost 30 years after it was first…
Using the manifestly spacetime-supersymmetric version of open superstring field theory, we construct the free action for the first massive states of the open superstring compactified to four dimensions. This action is in N=1 D=4 superspace…
A family of new twistor string theories is constructed and shown to be free from world-sheet anomalies. The spectra in space-time are calculated and shown to give Einstein supergravities with second order field equations instead of the…
We consider the twistor description of conformal higher spin theories and give twistor space actions for the self-dual sector of theories with spin greater than two that produce the correct flat space-time spectrum. We identify a ghost-free…
This paper studies the two-component spinor form of massive spin-3/2 potentials in conformally flat Einstein four-manifolds. Following earlier work in the literature, a non-vanishing cosmological constant makes it necessary to introduce a…
We study scattering equations and formulas for tree amplitudes of various theories in four dimensions, in terms of spinor helicity variables and on-shell superspace for supersymmetric theories. As originally obtained in Witten's twistor…
The Heterotic twistor string theory of Mason and Skinner is investigated with particular attention given to the role of topological gravity on the world-sheet. The general structure of scattering amplitudes is discussed and expressed in…
This thesis considers two different aspects of string theory, the tensionless limit of the string and supersymmetric sigma models. The tensionless limit is used to find a IIB supergravity background generated by a tensionless string.…
We present a twistor description for null two-surfaces (null strings) in 4D Minkowski space-time. The Lagrangian density for a variational principle is taken as a surface-forming null bivector. The proposed formulation is reparametrization…
We consider F-strings with arbitrary configurations in the Minkowski directions of a higher-dimensional spacetime, which also wrap and spin around $S^1$ subcycles of constant radius in an arbitrary internal manifold, and determine the…
This paper presents a covariant twistor string model in four dimensions coupled to two-dimensional worldsheet gravity with an anomaly-free BRST charge. The model contains two twistors and two fermionic bi-spinors with incidence related…
We suggest supersymmetric extension of conformally invariant string theory which is exclusively based on extrinsic curvature action. At the classical level this is a tension-less string theory. The absence of conformal anomaly in quantum…
A class of non-supersymmetric string backgrounds can be constructed using twists that involve space-time fermion parity. We propose a non-perturbative definition of string theory in these backgrounds via gauge theories with supersymmetry…
A new type of supersymmetric twistors is proposed and they are called $\theta$-twistors versus the supertwistors. The $\theta$-twistor is a triple of spinors including the spinor superspace coordinate $\theta$ instead of the Grassmannian…
We exploit the properties of the three-dimensional hyperbolic space to discuss a simplicial setting for open/closed string duality based on (random) Regge triangulations decorated with null twistorial fields. We explicitly show that the…