Recent content by oldman

I'm bandwidth disadvantaged and can't watch this video, which indeed sounds interesting, if not provocative. Can someone who has watched it (or even someone who hasn't) clarify for me what could be meant by: . It's interesting to see a tool of physical chemistry (Born-Oppennheimer...

I'm surprised that Barrow's paper hasn't generated more discussion --- just a bit of quibbling about inflation. I can't say I understand quite what the authors doing by "making" the Cosmological Constant into a field or, since they're not Zeus et al., rather supposing that it behaves like...

Here you're asking questions that are beyond my limited capacity to answer, Phrak. Perhaps someone else can step in. To me torsion means something less esoteric than connection coefficients, perhaps something similar to but distinct from curvature; involving circuits that display closure...

Uniform scale-change always makes my simple mind boggle; where's the reference ruler? Made of electromagnetism, I guess. Thanks for the reference to Poisson's notes, George. They are simply and lucidly written --- just right for me, with a bit of effort. Leafs to the rescue. The only thing...

Your welcome comments, Phrak, show thinking somewhat parallel to mine. I'll try and reply to comments by George Jones and Daverz a bit later --- I'm about 80 Km or so from a library that I know has a copy of Misner et al. Not so sure about Plebanski and Krasinski. In the meantime, thanks to...

Thanks very much for pointing me to this article, Mentz, but it's "quite above my fireplace" as folk put it here, where winter rather than summer looms. Thanks also for your helpful reply, bcrowell. The antipodean EotWash group look to me like gallant experimental crusaders. But I've still not...

I guess that my original post above is too obscure to have warranted a reply. I'll conclude by trying to explain my motivation a bit more fully. In the early 20th century, when Einstein was Generalising his (special) theory of Relativity (GR) to describe gravity, physics was what we might...

I’m provoked into posting in this thread by your remarks in post 145, Marcus. You quote Bohr's Truth as: And then add: I agree. A quibble: did Bohr talk of measurement in this quote? Or did he just say: Which is not quite the same thing. Talk is cheap. Measurement is probably...

As I understand it, Riemannian geometry doesn't allow Torsion (a property of geometry involving certain permutations among the indices of Christoffel Symbols). Does this restrict the geometry of General Relativity (GR) to describing only a curved spacetime with the Riemann curvature tensor? Is...

Folk here are looking for a reason consistent with the maelstrom of mathematical models that is current theoretical physics --- I can't help in that context Perhaps if the answer to the old philosophical chestnut "why is there something rather than nothing" is sought in topology a clue might...

Please let me check that I finally do follow your clarifications, Slider. Knots in ordinary string loops are called by topologists "knots in closed curves that are 1-dimensional topological spheres (a.k.a. "circles") embedded in 3-dimensional space" . Similarly, in higher dimensions...

Thanks again, Slider, for this extended reply. Colour is a nice imagineable extra dimension. The reason for needing two extra dimensions, but no more, to create a knot is simple, as I guessed in my O.P., for a knot in ordinary string , itself something essentially one dimensional albeit flexible...

Thanks for clarifying what is meant by homotopy. I understand what you say, but it's always needing two extra dimensions for making knots possible that puzzles me, no matter how many (10, 11, 23?) space dimensions there are. And the fact that we seem to live in the apparently minimalist...

Thanks for the reply. I liked your colour example, but sadly I don't even know what homotopic means. Also, it's nice to know that "In dimension n, one studies (n-2)-dimensional knots" --- but, still, why the 2? You're talking to a mathematical simpleton here -- one who doesn't even appreciate...

While re-reading James Jean's The Mysterious Universe I came across his statement that "the capacity for tying knots is limited to space of three dimensions", in the context of sailor's knots. I'm no mathematician, but understand that mathematical folk regard a knot more generally as a...