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xTras: a field-theory inspired xAct package for Mathematica (1308.3493v1)

Published 15 Aug 2013 in cs.SC, cs.MS, gr-qc, and hep-th

Abstract: We present the tensor computer algebra package xTras, which provides functions and methods frequently needed when doing (classical) field theory. Amongst others, it can compute contractions, make Ans\"atze, and solve tensorial equations. It is built upon the tensor computer algebra system xAct, a collection of packages for Mathematica.

Citations (223)

Summary

  • The paper demonstrates how xTras enhances tensor algebra by streamlining computations, performing contractions, and facilitating ansatz construction in field theory.
  • The package integrates with xAct and employs the Butler-Portugal algorithm for rapid canonicalization, enabling efficient resolution of complex tensorial equations.
  • xTras proves effective in recovering linearized Einstein equations and verifying the Gauss-Bonnet term’s topological properties, underscoring its research potential.

Overview of the xTras Package for Mathematica

The paper presents xTras, a sophisticated tensor computer algebra package designed to extend the capabilities of the xAct framework within Mathematica, focusing specifically on tasks pertinent to classical field theory. xTras aids researchers in executing tensor operations such as contractions, making Ansätze, and resolving tensorial equations. It integrates seamlessly with xAct, offering enhanced functionalities which were previously unavailable.

xAct, underlying the functionalities of xTras, is a robust collection of packages renowned for their efficiency in dealing with tensor algebra, notably due to the implementation of the Butler-Portugal algorithm. This algorithm enables rapid canonicalization of tensor indices based on permutation symmetries, facilitating a vast array of applications, ranging from tensor spherical harmonics to perturbations in homogeneous cosmological backgrounds.

Key Features of xTras

xTras introduces several key features which augment the capabilities of xAct:

  • Tensor Manipulation: Through xTras, users can engage in comprehensive tensor manipulations, which include but are not limited to computing contractions and varying tensor components, thereby addressing common computational requirements in field theoretical research.
  • Ansatz Construction: The package expedites the generation of parametrized expressions (Ansätze) by automating the detection and arrangement of symmetric and antisymmetric indices, which can be particularly valuable when dealing with complex field theories. This functionality alleviates the burden of manually determining viable tensor combinations that adhere to symmetry properties.
  • Handling Dimensional Dependencies: xTras excels in constructing dimension-dependent identities (DDIs) using basic identities from over-antisymmetrizations, crucial for computations in field theory where configurations and simplifications might vary with dimensions.

Numerical Results and Implications

The numerical efficacy of xTras is underpinned by its ability to manage extensive tensorial calculations effortlessly. The package proved instrumental in recovering linearized Einstein equations and confirming the topological nature of the Gauss-Bonnet term. Such results underscore the package's potential to simplify and streamline theoretical explorations across various dimensions and tensor configurations.

Speculative Future Developments

The development of xTras suggests a trajectory towards even more sophisticated computational tools within artificial intelligence and symbolic algebra systems. Potential future enhancements could include the further integration of multi-term symmetry simplifications and extending functionality to encompass greater classes of field theories, as well as refining user interfaces to democratize access to tensor computational resources.

Conclusion

xTras emerges as a significant extension of xAct, providing computational physicists and field theorists with a powerful suite of tools tailored to the exigencies of modern theoretical investigations. Its contributions lie not only in its present functionalities but also in its promise to inspire further advancements in symbolic computation and algebraic simplifications in physics research. As such, xTras is poised to become an invaluable asset in the computational toolkit of field theorists, facilitating explorations that are both profound and expansive.

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