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OK. So I can type faster than I can think.
Here's my CORRECTION: The Instantaneous Creation of Infinite Space The 3-space in which we live is one of an infinite variety of possible geometries. http://arxiv.org/PS_cache/gr-qc/pdf/9804/9804006.pdf. No mortal can identify the right spatial form. The Big Bang creation story comes in two incomprehensible versions. No human knows which version is correct. This thread is a request that knowledgeable mathematicians answer questions as simply as possible on the very essence of mathematical cosmology and what is knowable and provable. The most delightful creation story is that, in an instant, out of nothing, infinite space suddenly came to be. The infinite and everywhere appeared instantly, inexplicably; and time was also born. The second creation story is a plain and simple alternative to the first. Space (the everywhere) was born finite, with zero volume and grew from that; and time also came to be. The birthing of geometry in time has associated with that space and time, a flow of idealized, mathematical trajectories. Each trajectory is easily pictured as the spatial trace of an abstract idealized clock moving effortlessly through that geometric space, parameterized by its own clock time. Each clock, therefore, is defined by a timelike geodesic. The most glaring fact that I see in the simultaneous emergence of space and time is the existence of the above mentioned global flow of abstract coordinate clocks, all initially synchronized by God Himself. Obviously, attempting mathematical physics by coordinatizing space and time, if space is infinite and flat, can not produce the Lorentz transformation. It isn't the Creator's choice. It doesn't harmonize with creation. Going the route of conventional special relativity would imply that imagining an event at some time in one frame of reference would necessarily translate to the same event happening in another frame before time even began. It's against nature. Imagine the second creation story and the birthing of a hypersphere (or projective 3-space if you prefer) from an initial inexplicable point. The symmetry of this space demands a corresponding symmetry in the global multidirectional flow of abstract coordinate clocks. To understand this symmetry physically, I wish to understand motion generally. My most stubborn and longstanding expectation is that all motions in spatially compact spacetimes have extremely absolute characteristics, whereas, all motion in spatially infinite spacetime is relative. Therefo I would like to define a geodesic coordinate system in space as a flow of our abstract idealized clocks such that all those clocks travel the same distances as a function of clock time. I also like the requirement that nearby clocks in the flow all move in approximately the same direction. What are all the global geodesic coordinate systems for an expanding circle, sphere and hypersphere? Eugene Shubert http://www.everythingimportant.org |
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Perfectly Innocent wrote:
The most delightful creation story is that, in an instant, out of nothing, infinite space suddenly came to be. The infinite and everywhere appeared instantly, inexplicably; and time was also born. The second creation story is a plain and simple alternative to the first. Space (the everywhere) was born finite, with zero volume and grew from that; and time also came to be. Within FRW cosmological models you have those two choices (with a sub-choice for the first: flat or hyperbolic 3-space). But who's to say those models are all there is? In particular, it is expected that a real theory of quantum gravity will have major things to say about this, and presumably the evolution of the cosmos at early times will be significantly different in such a theory.... The birthing of geometry in time has associated with that space and time, a flow of idealized, mathematical trajectories. Each trajectory is easily pictured as the spatial trace of an abstract idealized clock moving effortlessly through that geometric space, parameterized by its own clock time. Each clock, therefore, is defined by a timelike geodesic. Sure. You can imagine such clocks. The most glaring fact that I see in the simultaneous emergence of space and time is the existence of the above mentioned global flow of abstract coordinate clocks, all initially synchronized by God Himself. Huh??? Those clocks "exist" only in your imagination, and it is up to YOU to synchronize them. Go ahead -- it's easy to IMAGINE how to do that.... But the only "God" here is YOU. Obviously, attempting mathematical physics by coordinatizing space and time, if space is infinite and flat, can not produce the Lorentz transformation. I have no idea what you mean by that. The Lorentz transformation holds between any pair of locally-inertial coordinates. That, of course, is true in any Lorentzian manifold. It isn't the Creator's choice. Speak for yourself -- because YOU are the "creator" here. This whole discussion is about figments of your imagination. That is, of course, what all mathematical models of physics are.... It doesn't harmonize with creation. Why not? -- You don't like your own creation? Going the route of conventional special relativity would imply that imagining an event at some time in one frame of reference would necessarily translate to the same event happening in another frame before time even began. But you're imagining a manifold that is not consistent with the requirements of SR, so why should one be concerned that attempting to apply SR yields nonsense? It's against nature. "Nature" of course has nothing whatsoever to do with this, as you are not discussing the world we inhabit, you are discussing a figment of your own imagination. Imagine the second creation story and the birthing of a hypersphere (or projective 3-space if you prefer) from an initial inexplicable point. The symmetry of this space demands a corresponding symmetry in the global multidirectional flow of abstract coordinate clocks. Why? In particular: all you have specified is that space is a 3-sphere; that is a topological condition, and is not "symmetry" in any usual sense, which is normally expressed as a set of Killing vectors, which obviously require a connection on the manifold. To understand this symmetry physically, I wish to understand motion generally. My most stubborn and longstanding expectation is that all motions in spatially compact spacetimes have extremely absolute characteristics, whereas, all motion in spatially infinite spacetime is relative. Here your "most stubborn and longstanding expectation" is clearly wrong. Counterexample: consider the flat and hyperbolic FRW manifolds. Just as in the spherical FRW manifolds, the cosmic time coordinate is expressed in the proper time since the initial singularity of each and every dust particle. That cosmic time coordinate is "absolute" in the sense that it is unique and the same for all observers, and yields a similarly "absolute" spatial structure relative to which all motion can be referenced. It is true that certain manifolds of GR have an "absolute" spatial structure wrt which motion can be referenced. This is invariably due to those manifolds having appropriate symmetries (e.g. a timelike Killing vector), or appropriate other structure (e.g. a congruence of timelike geodesics as in the FRW manifolds). Note that topology alone is not sufficient for this, you need some additional structure to have any sort of "absolute" reference (and beware of that word -- it has meanings which don't apply here). Topology constrains the metric applied to a manifold, but does not determine it. In your SxR toy model you can apply a metric that determines a specific "absolute frame". But I could apply a different metric to the same manifold that determines a different "absolute frame". The topology requires there be such an "absolute frame", but does not in any way determine which frame is the "absolute" one. Therefo I would like to define a geodesic coordinate system in space as a flow of our abstract idealized clocks such that all those clocks travel the same distances as a function of clock time. That is the usual thing to do in FRW manifolds, and is called "cosmic time". Note it applies in all FRW manfiolds, including those with non-compact 3-spaces. I also like the requirement that nearby clocks in the flow all move in approximately the same direction. That is also true in the FRW manifolds for those "cosmic clocks". What are all the global geodesic coordinate systems for an expanding circle, sphere and hypersphere? There are none. It simply is not possible to cover S^n with a single coordinate system, for any n0. Note this is a topological theorem, unrelated to any metric. If you are truly interested in topics like this, you need to study geometry. For starters I suggest: Frankel, _The_Geometry_of_Physics_. Tom Roberts |
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Tom Roberts wrote in message ...
Perfectly Innocent wrote: The most delightful creation story is that, in an instant, out of nothing, infinite space suddenly came to be. The infinite and everywhere appeared instantly, inexplicably; and time was also born. The second creation story is a plain and simple alternative to the first. Space (the everywhere) was born finite, with zero volume and grew from that; and time also came to be. Within FRW cosmological models you have those two choices (with a sub-choice for the first: flat or hyperbolic 3-space). Physicists are stuck on the FRW cosmological models and they won't let go because 1) legends are sacrosanct and 2) they're insulted by the infinite variety of equally reasonable geometries that mathematicians are familiar with. http://arxiv.org/PS_cache/gr-qc/pdf/9804/9804006.pdf But who's to say those models are all there is? Albert Einstein wished to exclude every other realistic option without offering reasonable justification. http://arxiv.org/PS_cache/gr-qc/pdf/9804/9804006.pdf In particular, it is expected that a real theory of quantum gravity will have major things to say about this, and presumably the evolution of the cosmos at early times will be significantly different in such a theory.... Please understand that I'm referring to the basics of the creation story. Space being created either infinite or finite is the only essential point that I'm alluding to. The birthing of geometry in time has associated with that space and time, a flow of idealized, mathematical trajectories. Each trajectory is easily pictured as the spatial trace of an abstract idealized clock moving effortlessly through that geometric space, parameterized by its own clock time. Each clock, therefore, is defined by a timelike geodesic. Sure. You can imagine such clocks. The most glaring fact that I see in the simultaneous emergence of space and time is the existence of the above mentioned global flow of abstract coordinate clocks, all initially synchronized by God Himself. Huh??? Those clocks "exist" only in your imagination, and it is up to YOU to synchronize them. Go ahead -- it's easy to IMAGINE how to do that.... But the only "God" here is YOU. My use of the word _God_ was meant to be flexible enough to include the initial conditions decided by Creation itself. I was kindly accommodating both the actual and philosophical pantheism made popular and acceptable by such notable physicists as Albert Einstein and Stephen Hawking. http://members.aol.com/Heraklit1/einstein.htm http://www.harrison.dircon.co.uk/wpm/index.htm It isn't the Creator's choice. Speak for yourself -- because YOU are the "creator" here. This whole discussion is about figments of your imagination. That is, of course, what all mathematical models of physics are.... Thanks for that acknowledgement about mathematical models of physics. It doesn't harmonize with creation. Why not? Going the route of conventional special relativity would imply that imagining an event at some time in one frame of reference would necessarily translate to the same event happening in another frame before time even began. But you're imagining a manifold that is not consistent with the requirements of SR, so why should one be concerned that attempting to apply SR yields nonsense? I believe that if you think about this carefully, you will see that Einstein's postulates of Special Relativity work perfectly fine on an instantaneously created, flat, infinite space but that the Lorentz transformation is not a natural law for that space. In this universe, as a consequence of instantaneous creation, there must have existed a natural initial synchronization for all idealized coordinate clocks in all frames of reference. t=0 everywhere. I believe that this is a straightforward counterexample to a false philosophy in relativity that I was combating recently on another thread. Eugene Shubert http://www.everythingimportant.org |
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#6
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In sci.astro Perfectly Innocent wrote:
[...] Physicists are stuck on the FRW cosmological models and they won't let go because 1) legends are sacrosanct and 2) they're insulted by the infinite variety of equally reasonable geometries that mathematicians are familiar with. http://arxiv.org/PS_cache/gr-qc/pdf/9804/9804006.pdf The paper you cite is by a physicist, not a mathematician. Furthermore, the "exotic" topologies Luminet talks about are all FRW cosmological models -- specifically, quotient spaces of standard simply connected FRW models by finite groups. In particular, they have the same general "history," starting with an initial big bang singularity. Your claim that physicists ignore these topological possibilities is simply wrong. See, for example, the September 1998 issue of _Classical and Quantum Gravity_, which is entirely devoted to this subject, or the review article by Lachieze-Rey and Luminet, Phys. Rept. 254 (1995) 135, which contains 165 references and has itself been cited over 100 times. In fact, there is an extensive observational effort to look for topologies of the type discussed by Luminet. The results so far have been negative: see Cornish et al., Phys. Rev. Lett. 92 (2004) 201302; Phillips and Kogut, preprint astro-ph/0404400; Uzan et al., Phys. Rev. D 69 (2004) 043003. Steve Carlip |
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Perfectly Innocent wrote:
wrote in message ... See, for example, the September 1998 issue of _Classical and Quantum Gravity_, How many physicists are reading your journal[...] Well, considering that C&QG (along with Phys Rev D) is the primary journal in the field, I'd say a lot. |
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Perfectly Innocent wrote:
wrote in message ... See, for example, the September 1998 issue of _Classical and Quantum Gravity_, How many physicists are reading your journal[...] Well, considering that C&QG (along with Phys Rev D) is the primary journal in the field, I'd say a lot. |
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In sci.astro Perfectly Innocent wrote:
wrote in message ... [...] Furthermore, the "exotic" topologies Luminet talks about are all FRW cosmological models -- specifically, quotient spaces of standard simply connected FRW models by finite groups. There is nothing "exotic" about the FRW cosmological models according to Luminet. He writes: "Such fruitful ideas of cosmic topology remained widely ignored by the main stream of big bang cosmology. Perhaps the Einstein-de Sitter model (1932), which assumed Euclidean space and eluded the topological question, had a negative influence on the development of the field. Almost all subsequent textbooks and monographies on relativistic cosmology assumed that the global structure of the universe was either the finite hypersphere, or the infinite Euclidean space, or the infinite hyperbolic space, without mentioning at all the topological indeterminacy." This says nothing either way about whether these topologies are "exotic." What I meant by the term was that: 1. They have complicated, nonabelian fundamental groups 2. While many examples are known, there is no systematic classification. 3. As far as I know, it is an open question whether these topologies are *classifiable* -- that is, whether, there is an algorithm that can determine whether any two given manifolds have the same topology or not. [...] See, for example, the September 1998 issue of _Classical and Quantum Gravity_, How many physicists are reading your journal and how many physicists still trust their outdated GR textbooks? The papers in that issue have a total of more than 250 citations. The issues are certainly known to most people working in the field. The paper by Cornish, Spergel, and Starkman on the possibility of actually detecting nontrivial topology by looking at the CMBR generated a great deal of excitement; it's been cited more than 70 times, and made Science News, Scientific American, and a bunch of newspapers. So did the recent observational results that rule out large numbers of topologies. This is close to the field I work in, and I know many of the people involved. It's true that 20 years ago, most people in general relativity and cosmology didn't pay much attention to three-manifold topologies. But things have changed *drastically* in the past couple of decades, and now it's a standard part of research. Steve Carlip |
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