Genady

You meant to say rather Bose-Einstein statistics, I believe.

(https://en.wikipedia.org/wiki/Degenerate_matter)

I'd like to find a new home for this book. Just pay a shipping cost. Amazon.com: Student Friendly Quantum Field Theory: Volume 1: Basic Principles and Quantum Electrodynamics: 9780984513956: Klauber, Robert D.: Books

The source gives the following "warning" before one reads the details: Pay attention to the last sentence.

This is encouraging. I will post a textbook for giveaway in the Scientific Education forum and see what happens. Unfortunately, shipping costs from here are not cheap.

I think so as well but would like to hear from the G&MO to be sure. No worries. None of these hurricanes is/was anywhere close to us. No effect on us at all.

I have some heavy weight textbooks that I don't need any more and would be glad to give them away for a cost of shipping. Is it OK to post such information on SFn? If so, where?

... and then, to test this restriction, one would have to compare events between IFRs. But the hypothesis

IIUC, this hypothesis is untestable.

Yes, they are different. Degeneracy and non-degeneracy refer to how many codons, one or more, code for 1 amino acid. OTOH, ambiguity and unambiguity refer to how many amino acids, one or more, 1 codon codes for.

To be precise, this metric is continuous, differentiable, and its first derivative is continuous. It is not twice differentiable though. Of course, it was introduced by hand, as defined in the question: "could one write down a metric for which ..."

lol +1

Today is October 20, 2020?

Developing on my previous post, I think that the metric \[diag(-1,1,1,1+H(z)z^2+H(-z)z^4)\] is not a valid solution to the EFE. *H() is Heaviside step function.

ok

If the metric is twice differentiable everywhere, then its Einstein tensor is everywhere defined, and you can just take this Einstein tensor as the energy-momentum tensor of your equation. Then, this metric is a solution of this equation. P.S. Of course, the metric has to be locally Lorentz to start with.

Both are unwelcomed.

In this example, a smooth curve appears not smooth as one zooms out. The opposite is also possible, i.e., a rugged curve appears smooth as one zooms out.

Space-time geometry is fine with singularities, too. Take a triangle. It is a perfect geometric shape in spite of having three singularities.

Right. But when this happens what fails is GR together with its framework, differential geometry. Not geometry. Geometry is fine with such singularities. Differential geometry has a problem.

This is incorrect. GR requires geometry with certain smoothness. It fails if the geometry is not sufficiently smooth.

I guess I was not clear enough. My claim is that geometry can exist without GR, but GR cannot exist without geometry. Thus, there cannot be an example of GR without geometry. As I said earlier, GR can fail for a reason other than absence of geometry.

@grayson, right?

"Failure of GR does not necessitate failure of geometry" implies geometry without GR. Why would I try to show an example of GR without geometry?

Evidently your perception is mistaken. I assume that it is based on pop-science rather than actual science sources. In my direct experience, science is fun and exciting.