Caravel: A C++ framework for the computation of multi-loop amplitudes with numerical unitarity

We present the first public version of Caravel, a C++17 framework for the computation of multi-loop scattering amplitudes in quantum field theory, based on the numerical unitarity method. Caravel is composed of modules for the D-dimensional decomposition of integrands of scattering amplitudes into master and surface terms, the computation of tree-level amplitudes in floating point or finite-field arithmetic, the numerical computation of one- and two-loop amplitudes in QCD and Einstein gravity, and functional reconstruction tools. We provide programs that showcase Caravel's main functionalities and allow to compute selected one- and two-loop amplitudes. Program Title:Caravel CPC Library link to program files:https://doi.org/10.17632/rfjrxrb3rk.1 Developer's repository link:https://gitlab.com/caravel-public/caravel.git Licensing provisions: GPLv3 Programming language: C++ External dependencies: • Required:Python3 [1], meson [2] • Optional:Doxygen [3], Eigen [4], GiNaC [5], GMP [6], Lapack [7], MPFR [8], MPI [9], PentagonLibrary [10,11], QD [12] Nature of problem: The computation of multi-loop multi-particle scattering amplitudes in quantum field theory Solution method: The multi-loop numerical unitarity method, functional reconstruction algorithms Additional comments including restrictions and unusual features: Current version includes tools employed in previous calculations, with the aim of showcasing details of the algorithms employed. Computations are organized by provided data files. [1]http://www.python.org/[2]https://mesonbuild.com/[3]http://www.doxygen.nl/[4]http://eigen.tuxfamily.org/[5]https://ginac.de/[6]https://gmplib.org/[7]http://www.netlib.org/lapack/[8]https://www.mpfr.org/[9]https://www.open-mpi.org/[10]T. Gehrmann, J. M. Henn and N. A. Lo Presti, JHEP 1810 (2018) 103, arXiv:1807.09812 [hep-ph][11]https://gitlab.com/caravel-public/pentagon-library[12]QD: A double-double and quad-double package for Fortran and C++, https://www.davidhbailey.com/dhbsoftware/