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Osvaldo Chandia

Publications and source records attributed to Osvaldo Chandia.

At least 19 recordsLinked to original sources
arXiv2026

A note on gauge-covariant vertex operators of the ambitwistor string

We construct gauge-covariant unintegrated vertex operators in an antighost-independent subcomplex of the bosonic ambitwistor string. For a linearized gauge field, a world-sheet ghost-derivative term completes the standard vertex so that BRST closure imposes $\p^nF_{nmI}=0$ without the Lorenz condition. In the rank-two sector we use an antighost-free ansatz that is sufficient to isolate a diffeomorphism-invariant spin-two subsector. After eliminating auxiliary fields and consistently setting the antisymmetric and scalar combinations to zero, BRST closure gives $R_{mn}=0$ without imposing transversality. We distinguish this construction from the full relative BRST cohomology of the bosonic ambitwistor string, whose additional antighost-dependent states lead to the known higher-derivative spectrum.

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arXiv2026

A note on conserved worldsheet supercharges in heterotic pure spinor superstring

We study conserved worldsheet charges associated with spacetime supersymmetry in heterotic pure-spinor superstrings on curved ten-dimensional superspace backgrounds. Requiring BRST invariance and worldsheet conservation gives a covariant set of superspace constraints. In flat superspace these conditions reproduce the standard ten-dimensional supersymmetry generator. In curved superspace, they organize the requirements for global supersymmetry in terms of a normalizable spinor superfield.

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arXiv2024

Compactifications of Type II Supergravities in Superspace

We propose a way to describe compactifications of Type II supergravities with fluxes directly from superspace. The superspace used is the one that arises naturally from the pure spinor superstring. We show how previous results of flux compactifications can be obtained from our method.

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arXiv2023

B-RNS-GSS Type II superstring in Ramond-Ramond backgrounds

The B-RNS-GSS formalism containing both RNS and GS worldsheet variables is extended for the description of the Type II superstring in curved backgrounds. The BRST charge of the theory is expressed in terms of $N=(1,1)$ superconformal generators $(T,G; {\widehat{T}}, {\widehat{G}})$, and the classical anticommutation relations $\{G,G\}=-2T$ and $\{\widehat{G},{\widehat{G}}\}=-2{\widehat{T}}$ are shown to imply the Type II supergravity equations of motion. The particular case of the Type IIB superstring in an $AdS_5\times S^5$ background is discussed and shown to be classically integrable.

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arXiv2022

B-RNS-GSS heterotic string in curved backgrounds

The recently established B-RNS-GSS formalism is extended for the description of the heterotic superstring in curved backgrounds. We propose a generalized action and BRST charge defined in the small Hilbert space with the standard form of an $\mathcal{N}=(1,0)$ worldsheet superconformal theory with superconformal generator $G$ and stress tensor $T$. We show that $\big\{G,G\big\}=-2T$ implies the D=10 N=1 supergravity and super-Yang-Mills equations of motion, as well as holomorphicity of the BRST charge.

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arXiv2021

Relating the $b$ ghost and the vertex operators of the pure spinor superstring

The OPE between the composite $b$ ghost and the unintegrated vertex operator for massless states of the pure spinor superstring is computed and shown to reproduce the structure of the bosonic string result. The vanishing of the double pole singularity is Lorentz gauge and the single pole is shown to be equal to the corresponding integrated vertex operator.

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arXiv2019

The non-minimal type II pure spinor string in a curved background

The pure spinor superstring in a type II curved background is considered. In order to define reparametrization ghosts, non-minimal pure spinor variables have to be present in the formalism. The BRST transformations of the non-minimal variables are obtained. It is found that the BRST transformations of a set of world-sheet variables have the form of the corresponding transformations in flat spacetime, up to a field-dependent Lorentz rotation. This simplify the construction of the reparametrization $b$ ghosts.

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arXiv2019

General fluctuations of the type II pure spinor string on curved backgrounds

The general fluctuations, in the form of vertex operators, for the type II superstring in the pure spinor formalism are considered. We review the construction of these vertex operators in flat space-time. We then review the type II superstrings in curved background in the pure spinor formalism to finally construct the vertex operators on a generic type II supergravity background.

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arXiv2019

General fluctuations of the heterotic pure spinor string on curved backgrounds

The general fluctuations, in the form of vertex operators, for the heterotic superstring in the pure spinor formalism are considered. The case of a flat background is reviewed and the case of a curved case is studied. The left-moving ghosts are pure spinors and the right-moving ghosts come from fixing the reparametrization invariance. The role of the reparametrization ghosts in the construction of the vertex operators is emphasized.

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arXiv2018

Vertex operators for the plane wave pure spinor string

In this work we give an explicit construction for the vertex operators of massless states in the pure spinor superstring in a plane wave background. The construction is based on the observation that the full action can be divided in two parts, where the simpler one is based on a smaller coset and closely resembles the gauge fixed Green-Schwarz action.

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arXiv2016

Ambitwistor superstring in the Green-Schwarz formulation

In this paper we construct the ambitwistor superstring in the Green-Schwarz formulation. The model is obtained from the related pure spinor version. We show that the spectrum contains only ten dimensional supergravity and that kappa symmetry in a curved background implies some of the standard constraints.

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arXiv2015

Ambitwistor pure spinor string in a type II supergravity background

We construct the ambitwistor pure spinor string in a general type II supergravity background in the semi-classical regime. Almost all supergravity constraints are obtained from nilpotency of the BRST charge and further consistency conditions from additional world-sheet symmetries. We also discuss the case of $AdS_5\times S^5$ background.

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