Masses have gravitational fields, which have energy, and energy has mass and makes gravitational fields. Masses interact with their gravitational fields to make energy {self-energy}| {matter field}. Because mass is only positive, gravity has interaction energy greater than zero.
renormalization
Mathematical renormalization adjusts values to prevent infinities.
electromagnetism
Perhaps, if charge moves (and external electric field is zero), charge gains velocity by interacting with its electric field, because energy in point-charge field is infinite (by Maxwell's equations or quantum electrodynamics). However, because positive and negative charges can induce each other, electromagnetism has no interaction energy.
Wheeler-Feynman theory
In Wheeler-Feynman theory, universe particles absorb moving-charge electric field, so field at large distances is zero, and system has no advanced solutions and no infinities. However, this theory is not correct.
perfect absorption
In perfect absorption, electric field is relativistically invariant, so all force-induced fields, including reaction forces, form other particles using photon exchanges and go to zero. Perfect absorption has only retarded solutions, because advanced solutions are improbable by thermodynamic laws. In expanding universes, absorption happens at low frequency for retarded solutions and at high frequency for advanced solutions. However, this theory is not correct.
Time-like space-time paths have points where space-time curvature and path curvature are not the same, and net gravity is zero {general energy condition}.
For classical matter, energy density is greater than or equal to zero in all reference frames {weak energy condition}. However, weak energy condition is false for quantum-mechanical scales.
For classical matter for long enough distances, energy density is greater than or equal to zero for all time-like paths {strong energy condition}. However, strong energy condition is false for quantum-mechanical scales.
5-Physics-Relativity-General Relativity
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Date Modified: 2022.0225