Causal set theory involves partially ordered causal sets that represent the discrete structure of the universe with just matter, action, and quantum phase. Space and time then emerge by sprinkling the geneology of random photon geodesics from causal matter, action, and phase from which emerges the manifold of space and time. Space and time then emerge from that sprinkling of random quantum photon geodesics across the universe and the sprinkled random distribution preserves Lorentz invariance, which is the foundation of gravity relativity.

However, it is the quantum action of light that gives matter its action and it is the quantum action of light that links quantum gravity to quantum charge. So sprinkling these random photon geodesics is what makes our quantum reality real and without the action of light, there would be no changes to matter and so it is light that gives matter its action.

The matter-action quantum gravity causal Hasse diagram shows the resonant photon geodesics of both quantum gravity and quantum charge. Quantum gravity bonds results from the bonding of particles of matter like hydrogen to the universe as the diagram shows. Quantum charge bonds result when hydrogens are sufficiently close and overwhelm the quantum gravity bond.

While both quantum gravity and quantum charge are reversible resonant photon geodesics, there are also irreversible nonresonant photon geodesics as heat from blackbodies. Blackbodies absorb resonant photons and then randomize photon phases and frequencies, eventually reemitting heat photons as a quantum blackbody after some time delay. Quantum blackbodies then represent the irreversible arrow of time for gravity relativity with the chaos of a large number of resonant photon geodesics.In matter action there are 1.5e118 aether particles to begin with that make up the causal set matter-action universe with 1.5e118 as condensed into 7.6e76 electrons, protons, and Rydberg photons that make up the dim light of the CMB. Electrons, protons, and photons make up configurations or manifolds within matter action as various quantum particles that photon exchange bond with each other. While single photon exchange is the basic glue for quantum charge, it is quadrupole biphoton exchange that is the basic glue for quantum gravity.

Photon geodesics are what make reality real and we see images as manifolds of sprinkled random photon geodesics from matter to our retinal neurons. An emitter populates a quantum photon state that includes an absorber in resonance with the emitter as shown in the upper figure below for quantum particles. Each emitter, though, also populates a quantum photon state with the universe in resonance with the CMB and there are two photon states, a biphoton, that bond the two emitters as quantum gravity as the lower figure below. Thus, unlike quantum charge, the quantum gravity biphoton exchanges are actually resonances between the universe and each emitter and not resonances between the emitters.

*Causal Sets and the Deep Structure of Spacetime*, arxiv :gr-qc/0508109v1, 2005.

*Quantum Dynamics without the Wave Function*, J. Phys. A: Math. Theor. 40 : 3207-3221, 2007.

*Causal Set Approach to Quantum Gravity*, 2018 https://iopscience.iop.org/journal/0264-9381/page/Focus-Issue-on-the-Causal-Set-Approach-to-Quantum-Gravity

*The Causal Set Approach to Quantum Gravity*, arXiv:1903.11544v2 [gr-qc] 28 Aug 2019.