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| Tags: look, newtonian, potential |
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#1
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Can an alternative measure of Newtonian potential
energy remove the Schwarzschild singularity (or at least move it to r=0)? A shell of matter gives rise to a potential which causes a redshift in the frequency of light. Redshifts do not add together - they multiply, for instance 1 + z = (1 + z_1) (1 + z_2), not 1 + z_1 + z_2. It is fundamental to general relativity that energy and frequency transform identically in a gravitational field - it would be inconsistent to assume differing transformations. Thus the calculation of gravitational potential energy should be obtained not from addition over the shells, but from a process reflecting the multiplicative nature of the redshift. It can be shown that a continuous multiplication of a function can be defined in the same way that integration is defined to represent a continuous summation. If u is the integral of a function, the continuous multiplication of the function gives U = U_0 exp(u / U_0) as the product where U_0 is an initial value. For u = -GMm/R as the Newtonian gravitational potential energy obtained from integration over the shells, continuous multiplication gives the product U = U_0 exp(u / U_0) where the initial value can be surmised to be the rest energy U_0 = mc^2 from Mach's principle, which postulates that rest energy is potential energy due to displacement of the mass, m, from distant matter. In the presence of a gravitational field the rest energy diminishes from U_0 = mc^2 to U = mc^2 exp(-GM/Rc^2). This can be compared to general relativity which has the gauge property that the dimensions of time, length and mass vary with the scale factor sigma = sqrt(1 - 2GM/Rc^2) as T = T_0 / sigma L = L_0 sigma M = M_0 / sigma^3 respectively, transforming the rest energy from E_0 = mc^2 far from the gravitational field to E = E_0 sigma in the presence of the field. U and E are almost indistinguishable for weak gravitational fields, so the question becomes how to get the exponential scale factor associated with U to replace the scale factor sigma which appears in the Schwarzschild solution. My guess would involve an exponential map of the metric to produce the multiplicative process. A file with more details (shells.pdf) is available at http://sites.google.com/site/revisingnewton/ |
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#2
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Colin Walker wrote on Sun, 28 Jun 2009 13:05:09 +0000:
Can an alternative measure of Newtonian potential energy remove the Schwarzschild singularity (or at least move it to r=0)? The Schwarzschild singularity in GR is already at r=0. -- http://www.canonicalscience.org/ |
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#3
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On Jun 28, 5:05*am, Colin Walker wrote:
Can an alternative measure of Newtonian potential energy remove the Schwarzschild singularity (or at least move it to r=0)? Given that Newtonian gravitation and GR are different theories, I'm going with "no". Furthermore, displacing the singularity by a coordinate change doesn't change the physics. A shell of matter gives rise to a potential which causes a redshift in the frequency of light. Redshifts do not add together - they multiply, for instance 1 + z = (1 + z_1) (1 + z_2), not 1 + z_1 + z_2. It is fundamental to general relativity that energy and frequency transform identically in a gravitational field *- it would be inconsistent to assume differing transformations. Since when? In GR, energy is simply the result of the metric being invariant under an infintesimal change in the t coordinate. Frequency isn't any more special. [snip rest] |
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#4
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On Jul 4, 8:56*pm, Eric Gisse wrote:
On Jun 28, 5:05*am, Colin Walker wrote: Can an alternative measure of Newtonian potential energy remove the Schwarzschild singularity (or at least move it to r=0)? Given that Newtonian gravitation and GR are different theories, I'm going with "no". Furthermore, displacing the singularity by a coordinate change doesn't change the physics. Sorry for using the wrong term - I should have said Schwarzschild radius or absolute event horizon instead of singularity. What I am proposing is not a coordinate transformation but a field transformation. Different field, different physics. It is fundamental to general relativity that energy and frequency transform identically in a gravitational field *- it would be inconsistent to assume differing transformations. Since when? In GR, energy is simply the result of the metric being invariant under an infintesimal change in the t coordinate. Frequency isn't any more special. A reference for the gauge property is Gravitation and Relativity by M.G. Bowler, published in 1976. Some elementary problems in GR can be solved using dimensional analysis. For example, a photon has energy E = h f where h is Planck's constant and f is photon frequency. By breaking down h into its dimensions of time, length and mass, it is clear that h = h_0 so Planck's constant does not change in a gravitational field. Doing the same with frequency (1/T) and energy shows that they both vary as sigma. My point is that if the redshift of frequency is computed using multiplication then so should the calculation of energy. This approach has limited application but is sufficient for a simple idealized free-fall example. By contrast, the gravitation constant varies as the 8th power of sigma, G = G_0 sigma^8 making dimensional analysis difficult for more complicated problems. |
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#5
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On Jul 1, 6:06*pm, CarlBrannen wrote:
On Jun 28, 6:05 am, Colin Walker wrote: Can an alternative measure of Newtonian potential energy remove the Schwarzschild singularity (or at least move it to r=0)? Hmmm. You might try using the Newtonian equivalent of the Schwarzschild equations of motion. A paper which gives them, along with the (somewhat simpler) equations of motion for the Gullstrand-Painleve coordinates of the Schwarzschild metric is at:http://www.brannenworks.com/Gravity/BranGravArXiv.pdf Thanks for the link to your paper. The modern role of force has been a source of confusion for me, and I was unaware of Gullstrand-Painleve coordinates. I think you have provided the means to answer my question because GP coordinates are entirely determined by the escape velocity. The river model of black holes by Hamilton and Lisle 2006 arXiv:gr-qc0411060v2 gives a metric ds^2 = -dt^2 + (dr + beta dt)^2 + r^2(dtheta^2 + sin^2theta dphi^2) where dt is in the frame of an object which is in free fall from infinity and where beta is the speed of that object, or the escape velocity. They say beta 'can also be considered to be a more general function of radius'. I take this to mean that it can be chosen freely. The escape velocity in GR can be found by increasing the energy E = E_0 sigma by the Lorentz factor 1/sqrt(1 - v^2/c^2) to get c sqrt(1 - sigma^2) with sigma = sqrt(1 - 2GM/Rc^2) which is also the Newtonian result. With an exponential scale factor, the escape velocity would be v = c sqrt[1 - exp(-2GM/Rc^2)] which determines Gullstrand-Painleve coordinates with beta = v. Thanks again Colin |
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