Gravitation is established as a deformation of spacetime in the presence of mass, its effects being the product of the concentration of spacetime toward centers of mass, or "vertices." As such, gravitation cannot be a force, it cannot therefore be mediated by a particle, and it cannot radiate as mass-energy. The assimilation of gravitation by quantum theory and its derivatives as a field of force, and the positing of a gravitational quantum of action where none is apparent, theoretically necessary, or conceptually coherent are entirely without justification.3
These are admittedly unsettling propositions, but in consolation, their acceptance would make one of the principal objectives of quantum theory less complicated, as gravitation with all its peculiarities could be disregarded in the pursuit of a unified field theory. I hope that acceptance might also signal the need to rely more upon conceptualization, and not so heavily on mathematical formalisms in the development of physical hypotheses.
1 There may be an appearance of force if the gradient of a gravitational field is extreme enough relative to a body's extension in the direction of the field to produce tidal stresses on the body's molecular binding energies. (The earth's ocean tides are a dramatic instance.) But this too is entirely geometric in its origin, and only manifests local variations in the intensity of the distortion of spacetime.
2 The most prominent case of hypothetical gravitational energy and its radiation is the inspiraling binary star system, where there is evidently a loss of net relative (kinetic/potential) energy between the companions due to their deteriorating orbital dynamics. In terms of gravitation as a geometric principle, the idea of a transformation of relative accelerations to force-like radiation is incongrous; the extrinsic energy corresponding to the decrease within the binary system would be interpreted instead as a purely relative increase of (kinetic/potential) energy between a binary system and the rest of the universe.
3 Like energy-bearing gravitational waves, other hypotheticals -- gravitomagnetism, dark matter, and dark energy -- can be expected to continue eluding detection, as all are based on the presumed association of gravitation with force.
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