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In QED, the field strength dependence is expressed by a field of virtual photons of varying spatial density. I know that we describe gravity as a warp in space-time, but how can one warp space (and time) if there isn't anything there to warp (how does one warp a vacuum)? We have established the lack of an ether, but the Einstein tensors describe a topological warping that could be expressed as a change in density of a field. Is there any current theory involving a field of virtual gravitons to quantify the field strength?

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The real question is "is gravity quantized" ?

In a quantum field theory of gravity there will be a similar construct as the photon field, virtual photons exchanged in interactions, virtual gravitons exchanged in interactions.

String theory quantises gravity and thus has a graviton and virtual gravitons on par with photons and virtual photons. It is still though a theory in progress, no definite model yet.

As for the warping this quote from the link might help if you are mathematically inclined:

classical general relativity looks in many ways like the theory of a massless ‘spin-two’ field propagating on the flat Minkowski spacetime of special relativity.

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  • $\begingroup$ Does string theory say anything about what processes could emit real gravitons? It seems like gravity only operates through virtual gravitons. $\endgroup$ – Michael Sep 13 '19 at 17:05
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    $\begingroup$ @Michael The classical gravitational field in the quantum form is modeled with virtual gravitons the way the classical electric and magnetic fields with virtual photons. Classical gravitation has gravitational waves created by accelerating masses ( in specific ways) similar to accelerated charges generating elecromagnetic waves; and quantized (effective) gravity has gravitons the way quantized electromagnetic fields have photons. These in the context of string theory are expected to be accommodated in string excitations,, gravitons and photons similarly, afaik. $\endgroup$ – anna v Sep 13 '19 at 18:17

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