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In discussions regarding quantun gravity we generally state that we need to develop a nonperturbative theory since "in quantizing gravity there are, in perturbation theory, infinitely many independent parameters (counterterm coefficients) needed to define the theory."

We know that our observable universe is not infinite in extent. In chaotic systems it is possible through trial and error to develop a general coefficent that can smooth out the chaotic fluctuations but to do this to infinite decimal places it would take an infinite amoount of time.

So the question is whether we actually need to utilize an infinite number of parameters or just a very large number of parameters? Can we develop an effective theory of quantum theory of gravity by just focusing on setting a large number of parameters (say $10^{100}$ assuming similar level of computational power) through extensive trial and error?

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    $\begingroup$ In fact, an inspection of two-loop quantum Einsteinnian gravity shows that General Relativity can never be renormalized without adding quadratic terms in the curvature in the action. It is not a matter of the number of coefficients for the bare Lagrangian. Keep in mind that what N. Alves said is for the effective field theory viewpoint of quantum field theory. $\endgroup$ Commented Nov 24 at 6:52

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Short answer: not quite.

The practical point of view on quantum field theory today is that you won't need the higher energy corrections as long as you keep yourself at low energies. In this sense, in practice, we should never need more than $N$ terms as long as the energies are low enough. The reason is that the corrections enter the equations in the form $$\text{stuff we know} + c_n\left(\frac{E}{\Lambda_{\text{UV}}}\right)^n \cdot \text{something new} + \cdots,$$ where $E$ is the energy we are looking at and $\Lambda_{\text{UV}}$ (called the ultraviolet cutoff) is a very large energy at which the theory breaks down. $c_n$ is the new parameter we need to measure (some fundamental constant, like the electron charge for example).

If $E$ is very small compared to $\Lambda_{\text{UV}}$, we don't need some corrections because $E/\Lambda_{\text{UV}} \ll 1$ and they are very small compared to what we see. However, as $E$ gets larger, $E/\Lambda_{\text{UV}}$ gets closer to one and all the corrections start getting more important.

This is the trouble. General relativity has infinitely many of these corrections. Hence, if we get to sufficiently high energies (near the Planck scale), all of them are important. At this point, the quantum field theory is not quite consistent anymore and we do need a new theory of quantum gravity.

Think of it as describing water as a fluid. It works well for the ocean, it works well for a pool, it works well for droplets, although each case has a few more important aspects than others (surface tension is very important for droplets, maybe not as important for the ocean). However, if you zoom in close enough, you find out water is actually a molecule. At this point, the fluid description simply does not make sense, no matter how much information you have about the "fluid". You need a new description that can actually deal with molecules.

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