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Comment by rwilson4 | Hacker News Reader

I believe the author's argument is: however simple or complicated dark matter and energy are, negative (inertial) mass just makes things even more complicated, without offering any new (testable) insights. The author herself points out that she (and the GR community) may be wrong about a lot of this stuff (e.g. that gravity is mediated by a spin-2 field), but absent a testable hypothesis, negative masses don't actually move the field forward at all.

Seemingly "crazy" ideas sometimes turn out to be correct! But in science, we demand radical ideas at least make testable hypotheses.

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That's the thing, I think it's exciting because that researcher does believe it to be testable. My comment from the last negative mass thread:

My favorite bit from the author on Twitter: https://threadreaderapp.com/thread/1070302359325151233.html > The next-generation radio telescope - the Square Kilometre Array @SKA_telescope will be able to test this theory, and directly confirm or invalidate its predictions. 13/17 It is rather surprising that the model predicts the properties of a LambdaCDM universe.

As a casual observer this is is what gets me excited! We'll get our answers one way or another

> "it’s highly problematic to introduce negative inertial masses because this means the vacuum becomes unstable. If you do this, you can produce particle pairs from a net energy of zero in infinitely large amounts. This fits badly with our observations."

Basically, if you mess the the equation, you have to be very sure you aren't simulating something silly. Which is easy to do, unfortunately I've done it often.

I still need to read the original paper in detail to confirm, but if the post is correct, the N-body simulation might have some issues.

Waaait a minute, isn't that describing something we've already observed - spontaneous creation of virtual particle pairs in a vacuum?

In infinitely large amounts?

We have definitely not observed spontaneous creation of virtual pairs in a vacuum. I do not blame you for thinking so as it is often described this way.

Almost no computation in Quantum Field Theory can be done exactly. What physicists do is using perturbation theory which is very similar to doing Taylor series in introductory calculus. Feynman, in a genius inspiration, found a way to represent the various mathematical terms that occur in these types of calculations as pictures which could be described in words. In this pictorial language, one would say things like "this term correspond to the creation of a virtual pair of particles", etc." The perturbation expansion is a mathematical "trick" done so that we can do obtain approximate results. Each individual term in that expansion has no physical meaning - in spite of the pictorial language used.

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