According to the Standard Model (SM) the quantum vacuum is not empty. However, General Relativity (GR) and the SM do not describe the vacuum structure. We propose a valence quark-based theory of the quantum vacuum structure based on a pion tetrahedron fabric that fills space with varying density. We assume that the valence quarks and antiquarks, u ,d ,u ̃ ,d ̃ that form the vacuum pion tetrahedron fabric. Motion of particles made of quarks on the vacuum pion tetrahedron fabric is performed by quark exchange reactions by tunneling through a double well potential and motion of massless particles are performed by internal degrees of freedom motion of the pion tetrahedron fabric. Active Galactic Nuclei (AGN) systems may be Carnot engines working between cold black hole (BH) and hot accretion disc reservoirs. The AGN Carnot cycle may create and emit to space pion tetrahedrons, protons, electrons and photons in pulses by the AGN jets. An alternative explanation for the observed expansion of the Universe may be the creation and emission of pion tetrahedrons to space by the AGN jets that expands the Universe quantum vacuum pion tetrahedron fabric from inside like a balloon. Shakura and Sunyaev thin accretion disc analytic expressions are used for calculating the pion tetrahedron mass and the number of pion tetrahedrons emitted by an AGN Carnot engine in a cycle.