In an old paper, Dr. D.V. Ahluwalia suggests that the Great Attractor embeds us in gravitational potential at the order of -3x10^(-5).
Interestingly, one of my colleague (Michael Peck) also suggestes that there could be global gravitaional potential affecting the entire Universe. So what di you think?
http://arxiv.org/pdf/gr-qc/9805067v1.pdf
Dear Mark: thank you for your answer. So if you think that there is evidence for such a global gravitational potential affecting the entire Universe, would you mind to let me know if there are recent papers discussing this hypothesis? Thanks
the local group has a gravitational potential as evidenced by the fact that the andromeda [sp?] is blue shifted and so is falling towards us, I went to a talk on the dynamics of the local group I can chase up the name of the person who studies this if you really want....
Dear Mark: thanks, yes please kindly find the name of scientist who describes the dynamics of local group. So far i only find this paper as provided by Michael Peck: http://arxiv.org/pdf/1109.0941.pdf.
Moreover, if you have found new paper on evidence of global gravitational potential affecting the entire Universe, would you mind to let me know. Thanks
http://arxiv.org/pdf/1109.0941.pdf
The problem to define such a global gravitational potential is Newton's Gravity versus General Relativistic description, and how to settle the issue of the boundary. The type of potentials I talked about many years ago were those that arise from nearly spherical distributions of matter around an observer, and the boundary conditions were at `infinity'. When we talk about the global potential, where to set the boundary? I am still interested in the question, perhaps someone more knowledgeable than I can enlighten us further.
Dear Dr. Ahluwalia: thank you for your answer. Yes, this problem is also interesting to me, my hypothesis is that perhaps there are different embedding gravitational potential for different scales, for example: solar system scale, great attractor scale, and universe scale. I can only find a paper by Michael Peck, but cannot locate the exact paper. Best wishes
http://astroreview.com/issue/2012/article/evidence-of-a-global-gravitational-potential
depends on what sort of boundary you mean, the boundary between us seeing a 1/r potential and cosmological expansion is at about the edge of the local group, I know how to model this using newtonian physics, takes about 3 equations, but a relativistic tolman-bondi type solution remain elusive...
Dear Mark: thank you for your answer. Do you mean we should use LTB theory? As far as i know, LTB is for inhomogenous universe. Best wishes
Blue shift of M 31 (i.e. negative radial velocity) by itself is not evidence of a local group gravitational potential. There could be zero local potential and M 31 would be just passing through, currently with a component of its velocity toward us. If you threw a baseball straight up, and that happens to be toward a z=5 quasar, does that mean the upward velocity of the baseball (baseball's light blue shifted as seen from the quasar, relative to Earth's light) is evidence of (caused by) the quasar's gravity?
Dear Allan and others: thank you for your answers. I just have an email with Michael Peck, qnd he gave me a link to his paper which is perhaps worth reading. Please see the link below. Best wishes
http://s3.amazonaws.com/presspublisher-do/upload/3419/Evidence%20of%20a%20Global%20Gravitational%20Potential.pdf
Victor
The dynamics of the Local Group (LG) and its gravitational potential are dominated by the M31 and the Milky Way. All the other galaxies in the LG are too small to contribute significantly to the potential. The Universe at large does not resemble the LG, so there is no reason why the potentials should bear any similarity.
@Dr. Matts Roos: thank you for your answer. Based on paper by Dr. Ahluwalia, i guess that perhaps there are different gravitational potentials at different scales: a. At solar system scale, b. at Great Attractor scale, and c. At The universe scale. That is my impression, and i do think they resemble each other. What is your opinion? Thanks
The local group is infalling, I went to a seminar by a spanish man in edinburgh who studies this, cannot remember his name off hand... The critical distance where cosmological expansion takes over so that galaxies are red shifted not blue shifted is about the dimensions of the local group - 500mpc if I remember, I know how to model this in newtonian mechanics but not yet in tolman-bondi....
In Newtonian gravity the potential of an homogeneous mass distribution is diverging toward minus infinity as the boundary radius increases, which means that the summed contribution of remote matter contributes more to the potential than the local matter, provided the distribution is effectively homogeneous, i.e., constant density. Now for dynamics what counts is the gradient of the potential. Even if the total potential diverges, the gradient may vanish, or stays small, so the absolute value of the potential is not dynamically relevant, only its gradient.
As an example, if one takes a triaxial homogeneous ellipsoid with fixed axis ratios a:b:c while a -> infinity the potential at the center diverges, as said before, but the force is a linear function of position to the center proportional to Ax, By, Cz where the positive constants A,B,C depends only on the ratios a/b, a/c and the density (their expressions involve elliptic integrals) and not on a, b, c separately. This example illustrates that an homogeneous model of the universe is singular since the force at a point depends directly on the shape of the boundary at arbitrarily large distances.
Of course the real universe is inhomogeneous at least below some scale of order 10Mpc where the local inhomogeneities produce forces larger than the universe at large. Above this scale it tends to be homogeneous but also time-dependant, showing that the remote matter indeed dominates "local" (several Mpc averaged) dynamics.
This problem is sufficiently well described in the Newtonian frame, where gravity propagates at infinite speed. Relativistic corrections are only needed at much larger scales (in fact for distances corresponding to redhsifts of order 0.5 and more).
Victor, any honest calculation or comparison of potentials is looking for answers which go much beyond your "resembles".
Dear Victor,
According to the PFO-CFO Theory (the publications are available at my and Elena Kadyshevich ResearchGate pages), gravitation is not constant over the Universe (you could see also my answers to the cosmological questions which were put by Elena at this site).
The local group has been studied for whether the gravitational potential associated with it differs from the global gravitational potential. The most recent answer, today at a conference in Estonia, says that it is inconclusive.
Only Nature could answer to this question but not any conference. (This is my answer to Prof. Matts Ross)
There are no proofs that it is constant. This means that we can't consider it to be constant. This is common law of science.
But if we can't say that gravitation is constant over Universe, we can't say that the light speed is constant over Universe because we know from experiments that light deviates in gravitation fields, i.e., we should conclude that there are no grounds to apply the Einstein's GR to Universe. I had said you this without any local group and you had answered me that you wrote four editions of handbook and that 400 papers, in which GR is applied to the entire Universe, are published each month.
What will you say at present? The fact of the matter is that the 100-year-old theories grew decrepit and should be rejected. Today, only the PFO-CFO Theory can replace them.
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