Campoamor Stursberg, Otto-RudwigLow, S. G.2023-06-202023-06-2020091751-811310.1088/1751-8113/42/6/065205https://hdl.handle.net/20.500.14352/43785Given a semidirect product g = s ⊎ r of semisimple Lie algebras s and solvable algebras r, we construct polynomial operators in the enveloping algebra U(g) of g that commute with r and transform like the generators of s, up to a functional factor that turns out to be a Casimir operator of r. Such operators are said to generate a virtual copy of s in U(g), and allow to compute the Casimir operators of g in closed form, using the classical formulae for the invariants of s. The behavior of virtual copies with respect to contractions of Lie algebras is analyzed. Applications to the class of Hamilton algebras and their inhomogeneous extensions are given.engjournal articlehttps//doi.org/10.1088/1751-8113/42/6/065205http://iopscience.iop.org/1751-8121/42/6/065205/open access512.554.3Lie algebraUniversal enveloping algebraCasimir operatorSemidirect productÁlgebra1201 Álgebra