Waxa uu muujiyay in Lorentz ee isla'egyada electrodynamics ma ahaayeen si buuxda Lorentz-covariant. Sidaas waxa uu tilmaamay sifooyinka group of beddelidda, oo uu saxo Lorentz ee qaaciidooyinka for beddelidda of cufnaanta lacag iyo cufnaanta hadda (taas oo si qarsoodi ah ku jira qaabka relativistic xawaaraha-daray, taas oo uu ku faahfaahsan May ee warqad u Lorentz). Poincaré markii ugu horeysay loo isticmaalo ereyga "Lorentz-beddelidda", oo uu siiyey qaab ay symmetrical toddoba bilood ka dib si ay u daabacday maanta. Waxa uu soo bandhigay mabda'a a non-koronto oo la daabacay ka dib, waxa uu soo bandhigay in ay si macquul ah loo xaqiijiyo in habka of beddelidda ee korontada. Waxa uu sidoo kale soo bandhigay warqad la daabacay on December 23, 1906 (oo lagu magacaabay "Poincaré" oo lagu daabacay warqad uu ku tilmaamay in ay si macqu
23ka Luulyo