Pure Spinor Sigma Model Research Articles

Beta deformed sigma model and strong deformation coupling limit

We study the beta deformation of the superstring in AdS5 × S5 at all orders in the deformation parameter, employing the pure spinor formalism. This is necessary in order to study the regime of strong deformation parameter, which in the field side is related to fishnet theories. We compare the pure spinor sigma model approach to the previously known supergravity description. We find a complete agreement. Moreover, the BRST structure of the worldsheet model provides a natural explanation of the peculiar features of the worldsheet model in the fishnet limit. In particular, we study the degeneracy of the sigma model Lagrangian. We show that the BRST structure is responsible for a particularly “tame” degeneration of the fishnet sigma-model.

A minimalistic pure spinor sigma-model in AdS

The b-ghost of the pure spinor formalism in a general curved background is not holomorphic. For such theories, the construction of the string measure requires the knowledge of the action of diffeomorphisms on the BV phase space. We construct such an action for the pure spinor sigma-model in AdS5 × S5. From the point of view of the BV formalism, this sigma-model belongs to the class of theories where the expansion of the Master Action in antifields terminates at the quadratic order. We show that it can be reduced to a simpler degenerate sigma-model, preserving the AdS symmetries. We construct the action of the algebra of worldsheet vector fields on the BV phase space of this minimalistic sigma-model, and explain how to lift it to the original model.

A construction of integrated vertex operator in the pure spinor sigma-model in AdS 5 × S 5

Vertex operators in string theory come in two varieties: integrated and unintegrated. Understanding both types is important for the calculation of the string theory amplitudes. The relation between them is a descent procedure typically involving the b-ghost. In the pure spinor formalism vertex operators can be identified as cohomology classes of an infinite-dimensional Lie superalgebra formed by covariant derivatives. We show that in this language the construction of the integrated vertex from an unintegrated vertex is very straightforward, and amounts to the evaluation of the cocycle on the generalized Lax currents.

PURE SPINOR FORMALISM FOR ${\rm Osp}({\mathcal N}\vert 4)$ BACKGROUNDS

We start from the Maurer–Cartan (MC) equations of the [Formula: see text] superalgebras satisfied by the left-invariant superforms realized on supercoset manifolds of the corresponding supergroups and we derive some new pure spinor constraints. They are obtained by "ghostifying" the MC forms and extending the differential d to a BRST differential. From the superalgebras [Formula: see text] we single out different subalgebras [Formula: see text] associated with the different cosets [Formula: see text]: each choice of ℍ leads to a different weakening of the pure spinor constraints. In each case, the number of parameter is counted and we show that in the cases of Osp (6|4)/ U (3)× SO (1, 3), Osp (4|4)/ SO (3) × SO (1, 3) and finally Osp (4|4)/ U (2) × SO (1, 3) the bosonic and fermionic degrees of freedom match in order to provide a c = 0 superconformal field theory. We construct both the Green–Schwarz and the pure spinor sigma model for the case Osp (6|4)/ U(3) × SO (1, 3) corresponding to AdS 4 ×ℙ3. The pure spinor sigma model can be consistently quantized.

Nonlocal charges for bonus yangian symmetries of Super-Yang-Mills

The existence of a "bonus" U(1) level-one Yangian symmetry of N=4 super-Yang-Mills has recently been proposed. We provide evidence for this proposal by constructing the BRST-invariant nonlocal charge in the pure spinor sigma model corresponding to this bonus level-one symmetry. We also construct analogous charges for bonus U(1) symmetries at all odd levels of the Yangian.

Quantum current algebra for the AdS 5 × S 5 superstring

The sigma model describing the dynamics of the superstring in the $AdS_5 \times S^5$ background can be constructed using the coset $PSU(2,2|4)/SO(4,1)\times SO(5)$. A basic set of operators in this two dimensional conformal field theory is composed by the left invariant currents. Since these currents are not (anti) holomorphic, their OPE's is not determined by symmetry principles and its computation should be performed perturbatively. Using the pure spinor sigma model for this background, we compute the one-loop correction to these OPE's. We also compute the OPE's of the left invariant currents with the energy momentum tensor at tree level and one loop.

Pure spinor superstrings on generic type IIA supergravity backgrounds

We derive the Free Differential Algebra for type IIA supergravity in 10 dimensions in the string frame. We provide all fermionic terms for all curvatures. We derive the Green-Schwarz sigma model for type IIA superstring based on the FDA construction and we check its invariance under κ-symmetry. Finally, we derive the pure spinor sigma model and we check the BRST invariance. The present derivation has the advantage that the resulting sigma model is constructed in terms of the superfields appearing in the FDA and therefore one can directly relate a supergravity background with the corresponding sigma model. The complete explicit form of the BRST transformations is given and some new pure spinor constraints are obtained. Finally, the explicit form of the action is given.