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arXiv · 2606.05204

xCPS: an xAct package for covariant phase space, Noether charges, and entropy

Juan Margalef-Bentabol
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Abstract

xCPS is an xAct tensor algebra package for symbolic computations within the covariant phase space formalism of field theories. From a generic Lagrangian, xCPS automates the derivation of equations of motion and symplectic currents. It systematically determines whether an infinitesimal transformation in the space of fields is a Noether symmetry and computes the associated Noether charge. Additionally, xCPS can in many cases determine whether a tensorial expression is a divergence and, if so, find its divergence potential. By implementing vertical exterior calculus through a graded, supercommutative wedge product and vertical operators, the package enables efficient computations in gauge theories and higher-derivative models of gravity, including the derivation of thermodynamic quantities like Wald's entropy. xCPS is open-source under the GPL license and available at https://github.com/juanmargalef.

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Juan Margalef-Bentabol. 2026-05-22. xCPS: an xAct package for covariant phase space, Noether charges, and entropy. https://arxiv.org/abs/2606.05204

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