Insights A Principle Explanation of the “Mysteries” of Modern Physics

[PeterDonis]

we know such adjoined solutions allow for larger orbital mass than proper mass

Isn't the difference the opposite? The "orbital mass" is what you are calling "dynamic mass" in the paper, and it is smaller than the "proper mass".

 

[PeterDonis]

I'm not taking about the effect of geometry on the light rays.

Ok, good. I didn't think so, but thanks for confirming.

 

[RUTA]

Isn't the difference the opposite? The "orbital mass" is what you are calling "dynamic mass" in the paper, and it is smaller than the "proper mass".

The orbital mass obtained from galactic rotation curve data is larger than the locally-determined proper mass (obtained from mass-luminosity ratios for example). That's the "missing mass" problem.

 

[PeterDonis]

The orbital mass obtained from galactic rotation curve data is larger than the locally-determined proper mass (obtained from mass-luminosity ratios for example).

I understand what the actual data says. But the statement of yours that I quoted in post #51 does not seem correct as a description of the effect that is present in the model. In the model, "dynamic mass" is smaller than "proper mass", not larger. So if the "dynamic mass" in the model is supposed to correspond to the orbital mass obtained from rotation curve data, and the "proper mass" in the model is supposed to correspond to the mass obtained from luminosity data, then the model is obviously wrong, since the model says "dynamic mass" should be smaller than "proper mass" but the actual data says "dynamic mass" is larger than "proper mass".

So either the model is wrong or I've misunderstood how the "dynamic mass" and "proper mass" in the model are supposed to correspond to the "orbital mass" (from rotation curves) and the "proper mass" (from luminosity) in the data.

 

[RUTA]

I understand what the actual data says. But the statement of yours that I quoted in post #51 does not seem correct as a description of the effect that is present in the model. In the model, "dynamic mass" is smaller than "proper mass", not larger. So if the "dynamic mass" in the model is supposed to correspond to the orbital mass obtained from rotation curve data, and the "proper mass" in the model is supposed to correspond to the mass obtained from luminosity data, then the model is obviously wrong, since the model says "dynamic mass" should be smaller than "proper mass" but the actual data says "dynamic mass" is larger than "proper mass".

So either the model is wrong or I've misunderstood how the "dynamic mass" and "proper mass" in the model are supposed to correspond to the "orbital mass" (from rotation curves) and the "proper mass" (from luminosity) in the data.

I went back and looked at the paper and you're right, we flipped the terms there from what I said above. I was using the term "dynamical mass" as in astronomy where it corresponds to "orbital mass" (the larger mass). In the paper, the term "dynamical mass" corresponds to what we were going to take as the mass obtained from the mass-luminosity relationship, i.e., the "local" value, since that's how one ultimately obtains the ML relationship. Thus, the terms are flipped. See on p. 5 starting with "Suppose that the Schwarzschild vacuum surrounding the FLRW dust ball in our example above is itself surrounded ... ."

 

[PeterDonis]

the terms are flipped. See on p. 5

Yes, I see that part, but I don't think it's correct. On p. 2, the relationship between proper mass and dynamic mass is given by:

$$
dM_p = \left( 1 - \frac{2 G M}{c^2 r} \right)^{- 1/2} dM
$$

where $M_p$ is proper mass and $M$ is dynamic mass. This formula clearly says that proper mass is locally measured and dynamic mass is externally measured, and the text accompanying the formula agrees with that.

However, on p. 5, in the text you refer to, "proper mass" $M_p$ is now claimed to be "globally determined" and to be the mass that would be measured by an observer in the surrounding FRW region. That is inconsistent with the formula and text on p.2, and also with the standard GR treatment of the spacetime geometry the paper is describing.

In the text on p. 5, you are describing a collapsing FRW region, which I'll call the "interior region" (which, to properly model something like a galaxy, should really be a stationary region containing matter, as I have commented before, but making that change would not affect what I am about to say), surrounded by a Schwarzschild vacuum region, surrounded by an expanding FRW region, which I'll call the "exterior universe". The interior region and Schwarzschild vacuum region together I will call the "bubble".

In the Schwarzschild vacuum region, the mass of the interior region, as measured by orbital dynamics of objects in the Schwarzschild vacuum region, is $M$. The text on p. 5 agrees with that.

However, the mass of the interior region as measured by an observer in the exterior universe, will not be $M_p$. An observer in the exterior universe cannot even measure the mass of the interior region directly, using orbital dynamics, because any such orbit will be affected by the stress-energy in the exterior universe that is closer to the bubble than the orbit itself. And if we imagine correcting such a measurement to subtract out the mass in the exterior universe that is affecting the orbit, the remainder will be $M$, not $M_p$.

The simplest way to see this is to observe that the function $m(r)$, which gives the "mass inside radius $r$" ("mass" meaning the mass measured by orbital dynamics) as a function of the areal radius $r$ centered on the bubble, must be continuous, and its value in the Schwarzschild vacuum region is $M$. Call the areal radius of the exterior boundary of the bubble $R_0$. Then we have $m(R_0) = M$. Now consider $m(R_0 + dr)$, the value of $m(r)$ just a little way into the exterior universe. This value, by continuity, must be $M + dM$ for $dM$ infinitesimal. But the paper's claim would require it to be $M_p + dM$, where $M_p - M$ is not infinitesimal. So the paper's claim is inconsistent with continuity of $m(r)$.

 

[RUTA]

Yes, I see that part, but I don't think it's correct. On p. 2, the relationship between proper mass and dynamic mass is given by:

$$
dM_p = \left( 1 - \frac{2 G M}{c^2 r} \right)^{- 1/2} dM
$$

where $M_p$ is proper mass and $M$ is dynamic mass. This formula clearly says that proper mass is locally measured and dynamic mass is externally measured, and the text accompanying the formula agrees with that.

However, on p. 5, in the text you refer to, "proper mass" $M_p$ is now claimed to be "globally determined" and to be the mass that would be measured by an observer in the surrounding FRW region. That is inconsistent with the formula and text on p.2, and also with the standard GR treatment of the spacetime geometry the paper is describing.

In the text on p. 5, you are describing a collapsing FRW region, which I'll call the "interior region" (which, to properly model something like a galaxy, should really be a stationary region containing matter, as I have commented before, but making that change would not affect what I am about to say), surrounded by a Schwarzschild vacuum region, surrounded by an expanding FRW region, which I'll call the "exterior universe". The interior region and Schwarzschild vacuum region together I will call the "bubble".

In the Schwarzschild vacuum region, the mass of the interior region, as measured by orbital dynamics of objects in the Schwarzschild vacuum region, is $M$. The text on p. 5 agrees with that.

However, the mass of the interior region as measured by an observer in the exterior universe, will not be $M_p$. An observer in the exterior universe cannot even measure the mass of the interior region directly, using orbital dynamics, because any such orbit will be affected by the stress-energy in the exterior universe that is closer to the bubble than the orbit itself. And if we imagine correcting such a measurement to subtract out the mass in the exterior universe that is affecting the orbit, the remainder will be $M$, not $M_p$.

The simplest way to see this is to observe that the function $m(r)$, which gives the "mass inside radius $r$" ("mass" meaning the mass measured by orbital dynamics) as a function of the areal radius $r$ centered on the bubble, must be continuous, and its value in the Schwarzschild vacuum region is $M$. Call the areal radius of the exterior boundary of the bubble $R_0$. Then we have $m(R_0) = M$. Now consider $m(R_0 + dr)$, the value of $m(r)$ just a little way into the exterior universe. This value, by continuity, must be $M + dM$ for $dM$ infinitesimal. But the paper's claim would require it to be $M_p + dM$, where $M_p - M$ is not infinitesimal. So the paper's claim is inconsistent with continuity of $m(r)$.

Sorry for the delay, I'm working on another paper now, let me get back to you with my thinking on this :-)

 

[Jimster41]

Correct.

In order that the DM fits are compelling, we would need to derive theoretical predictions for the fitting factors currently found empirically (for galactic rotation curves, galactic cluster mass profiles, CMB anisotropies) using contributions from those boundary terms. Again, that's just a simplification, but no one is ever going to solve Einstein's equations for a real galaxy. What we need to do is at least motivate the fitting factors via other measurements (luminosity, temperature, etc.). Then check the theoretical (approximated) predictions for the fitting factors against those obtained empirically. The work done to date was simply to find out whether or not the inverse square law functional form is reasonable (the answer there is clearly affirmative), so we know what we're looking for in the GR formalism. Have you done the fits for these data using MOND, various modified gravity theories, and the different DM models? If so, you'll see that our result is on par with all of those (I did all those and showed the comparisons in our papers). Anyway, finding theoretical predictions for the fitting factors should be possible, but I've been working on other questions in foundations that I find more interesting :-)

What I find more interesting than finishing the "no-DM-GR-is-correct model" is showing how the whole of physics is coherent, contrary to popular belief. And, I found a big piece of that by answering Bub's question, "Why the Tsirelson bound?" So, I've been busy these past two years working on the consequences of that answer.

So this T bound says there is some cutoff that makes the classical world have zero QM (neutral monistic) magic (no long-distance-large-object/ensemble-non-local ...ness), is that roughly right?

Is it related to “decoherence” which I sort of interpret as the Gaussian noise canceling effect of Lots of long distance large object/ensemble non-localness - which seems plausible but statistical and therefore unsatisfying (FYI that was a joke)... or is it somehow a clean unavoidable deduction?

And if it seemingly analytic and clean could that be due to the fact all Alice and Bob cases are toys (I.e they pretend there are these bounds on the lab to begin with)? Alternatively could it be that there are something more like Tsirelson “gaps” or troughs (waves) recurrence etc?

I know that’s a lot of question, so, just say I’m looking forward to learning about that one. Also, to me it bears on the discussion you and Peter were having about observes “inside the mass” vs “orbiting the mass”

 

[RUTA]

Here is the paper I was working on "Einstein's missed opportunity to rid us of 'spooky actions at a distance'". I'm posting the link here since it's relevant to this Insight. Hopefully I can get back to the pending questions above tomorrow.

 

[RUTA]

So this T bound says there is some cutoff that makes the classical world have zero QM (neutral monistic) magic (no long-distance-large-object/ensemble-non-local ...ness), is that roughly right?

Is it related to “decoherence” which I sort of interpret as the Gaussian noise canceling effect of Lots of long distance large object/ensemble non-localness - which seems plausible but statistical and therefore unsatisfying (FYI that was a joke)... or is it somehow a clean unavoidable deduction?

And if it seemingly analytic and clean could that be due to the fact all Alice and Bob cases are toys (I.e they pretend there are these bounds on the lab to begin with)? Alternatively could it be that there are something more like Tsirelson “gaps” or troughs (waves) recurrence etc?

I know that’s a lot of question, so, just say I’m looking forward to learning about that one. Also, to me it bears on the discussion you and Peter were having about observes “inside the mass” vs “orbiting the mass”

The Tsirelson bound is the most QM can violate the Bell inequality known as the CHSH inequality. Classical physics says the CHSH quantity must reside between $\pm 2$, but the Bell states give $\pm 2 \sqrt{2}$ (the Tsirelson bound). Superquantum correlations respect no-superluminal-signaling and give a CHSH quantity of 4. So, quantum information theorists want to know "Why the Tsirelson bound?" That is, why doesn't Nature produce superquantum correlations? Our answer is "conservation per NPRF." Of classical, QM, and superquantum, only QM satisfies this constraint.

 

[RUTA]

Yes, I see that part, but I don't think it's correct. On p. 2, the relationship between proper mass and dynamic mass is given by:

$$
dM_p = \left( 1 - \frac{2 G M}{c^2 r} \right)^{- 1/2} dM
$$

where $M_p$ is proper mass and $M$ is dynamic mass. This formula clearly says that proper mass is locally measured and dynamic mass is externally measured, and the text accompanying the formula agrees with that.

However, on p. 5, in the text you refer to, "proper mass" $M_p$ is now claimed to be "globally determined" and to be the mass that would be measured by an observer in the surrounding FRW region. That is inconsistent with the formula and text on p.2, and also with the standard GR treatment of the spacetime geometry the paper is describing.

In the text on p. 5, you are describing a collapsing FRW region, which I'll call the "interior region" (which, to properly model something like a galaxy, should really be a stationary region containing matter, as I have commented before, but making that change would not affect what I am about to say), surrounded by a Schwarzschild vacuum region, surrounded by an expanding FRW region, which I'll call the "exterior universe". The interior region and Schwarzschild vacuum region together I will call the "bubble".

In the Schwarzschild vacuum region, the mass of the interior region, as measured by orbital dynamics of objects in the Schwarzschild vacuum region, is $M$. The text on p. 5 agrees with that.

However, the mass of the interior region as measured by an observer in the exterior universe, will not be $M_p$. An observer in the exterior universe cannot even measure the mass of the interior region directly, using orbital dynamics, because any such orbit will be affected by the stress-energy in the exterior universe that is closer to the bubble than the orbit itself. And if we imagine correcting such a measurement to subtract out the mass in the exterior universe that is affecting the orbit, the remainder will be $M$, not $M_p$.

The simplest way to see this is to observe that the function $m(r)$, which gives the "mass inside radius $r$" ("mass" meaning the mass measured by orbital dynamics) as a function of the areal radius $r$ centered on the bubble, must be continuous, and its value in the Schwarzschild vacuum region is $M$. Call the areal radius of the exterior boundary of the bubble $R_0$. Then we have $m(R_0) = M$. Now consider $m(R_0 + dr)$, the value of $m(r)$ just a little way into the exterior universe. This value, by continuity, must be $M + dM$ for $dM$ infinitesimal. But the paper's claim would require it to be $M_p + dM$, where $M_p - M$ is not infinitesimal. So the paper's claim is inconsistent with continuity of $m(r)$.

Yes, there is a formal inconsistency exactly as you point out. The reason for that is we have discrete objects (stars) separated by light years modeled by a continuum for data collection and curve fitting. I'm thinking of the discrete objects for the use of varying boundaries for varying mass values while modeling the effect in continuum fashion for comparison with the data (which has to be collected that way obviously).

On another note, the mass we obtain from atomic/molecular spectra (ultimately responsible for the mass-luminosity relationship and mass of orbiting gas) is the "locally measured interior mass," since the spectra depend on the mass of the atoms/molecules as would be obtained in a lab on Earth.

One more note and I have to run. Note that the missing mass seems large (as large as a factor of 10 increase), but in terms of spatial curvature on galactic scales, it's tiny. It's in the paper, but I think the spatial curvature for galactic mass densities is on the order of $10^{-45}m^{-2}$. So, a change by a factor of 10 one way or another isn't very big in terms of GR.

 

[PeterDonis]

there is a formal inconsistency exactly as you point out

I don't think it's a formal inconsistency; I think it's a physical error.

The reason for that is we have discrete objects (stars) separated by light years modeled by a continuum

I don't see how that helps any, but perhaps I'm misunderstanding your argument. Let me try to frame a question that might help to elucidate what your argument is.

We on Earth observe some distant galaxy, and we see a discrepancy between two methods of estimating that galaxy's mass:

Method #1: Measure the rotation curves and use that to estimate the mass from the appropriate dynamical equations. This gives us a mass which I'll call $M_R$.

Method #2: Measure the aggregate luminosity and use that to estimate the mass using the appropriate relationships between mass and luminosity for stars. This gives us a mass which I'll call $M_L$.

The discrepancy is that we find $M_R > M_L$ by some significant factor.

Now the question, in two parts:

(1) Which of the two observations above, $M_R$ or $M_L$, do you think is affected by whatever source of error your paper is describing, and which your alternative method of analysis in the paper claims to fix?

(2) How does your alternative method of analysis fix the error? That is: if your answer to #1 is that $M_R$ as estimated by standard methods is larger than it should be, how does your method make $M_R$ smaller so it matches $M_L$? Or, if your answer to #1 is that $M_L$ as estimated by standard methods is smaller than it should be, how does your method make $M_L$ larger so it matches $M_R$?

 

[PeterDonis]

Now the question, in two parts:

(1) Which of the two observations above, $M_R$ or $M_L$, do you think is affected by whatever source of error your paper is describing, and which your alternative method of analysis in the paper claims to fix?

(2) How does your alternative method of analysis fix the error? That is: if your answer to #1 is that $M_R$ as estimated by standard methods is larger than it should be, how does your method make $M_R$ smaller so it matches ? Or, if your answer to #1 is that $M_L$ as estimated by standard methods is smaller than it should be, how does your method make $M_L$ larger so it matches ?

Perhaps it will also help if I give what I take to be the answers to these questions that would be given by a proponent of (A) dark matter, and (B) MOND.

(A1) $M_R$ is correct, but $M_L$ is too small because it only counts luminous matter.
(A2) There is other matter present, dark matter, which is not luminous and so can't be counted that way. When we add in the mass of dark matter, we get $M_L + M_D = M_R$, which fixes the discrepancy.

(B1) $M_L$ is correct, but $M_R$ is too large because it is estimated using the wrong dynamical equations.
(B2) MOND changes the dynamical equations so that $M_R$ is smaller and matches $M_L$, which fixes the discrepancy.

 

[ohwilleke]

FWIW, my read on the paper (and RUTA can correct me if I'm wrong) is that B1 and B2 are the answers here as well, although not so much "the wrong dynamical equations" as the wrong operationalization of the right dynamical equations, causing non-Newtonian, non-linear GR effects to be disregarded because they naively seem insignificant in any particular instance where they are considered. But the GR deviations from Newtonian approximations actually add up to something that is a big deal in a system like a galaxy, or a galaxy cluster, or the immediate post-Big Bang universe as a whole, because the insignificant effects don't cancel out.

 

[PeterDonis]

my read on the paper (and RUTA can correct me if I'm wrong) is that B1 and B2 are the answers here as well, although not so much "the wrong dynamical equations" as the wrong operationalization of the right dynamical equations

This was my initial read as well, based on the usage of the terms "proper mass" and "dynamical mass" -- basically, that the non-Newtonian effects mean that the "proper mass", which includes corrections for things like spatial curvature, is a better thing to plug into the dynamical equations than the "dynamical mass", which does not include those corrections. However, that can't be the right answer because, as I noted in an earlier post, the correction is in the wrong direction: the corrections due to things like including spatial curvature make the estimate for $M_R$ larger, not smaller.

 

[RUTA]

I don't think it's a formal inconsistency; I think it's a physical error.
I don't see how that helps any, but perhaps I'm misunderstanding your argument. Let me try to frame a question that might help to elucidate what your argument is.

We on Earth observe some distant galaxy, and we see a discrepancy between two methods of estimating that galaxy's mass:

Method #1: Measure the rotation curves and use that to estimate the mass from the appropriate dynamical equations. This gives us a mass which I'll call $M_R$.

Method #2: Measure the aggregate luminosity and use that to estimate the mass using the appropriate relationships between mass and luminosity for stars. This gives us a mass which I'll call $M_L$.

The discrepancy is that we find $M_R > M_L$ by some significant factor.

Now the question, in two parts:

(1) Which of the two observations above, $M_R$ or $M_L$, do you think is affected by whatever source of error your paper is describing, and which your alternative method of analysis in the paper claims to fix?

(2) How does your alternative method of analysis fix the error? That is: if your answer to #1 is that $M_R$ as estimated by standard methods is larger than it should be, how does your method make $M_R$ smaller so it matches $M_L$? Or, if your answer to #1 is that $M_L$ as estimated by standard methods is smaller than it should be, how does your method make $M_L$ larger so it matches $M_R$?

There is no error, they are two different measurements of mass for one and the same matter, as allowed per GR. You can map them one to the other as I showed in the paper.

 

[PeterDonis]

There is no error

What I am calling the "error" there is the discrepancy between $M_R$ and $M_L$ when using standard methods to estimate both. So there is an error. I am trying to understand how your proposed method resolves it. See below.

they are two different measurements of mass for one and the same matter, as allowed per GR. You can map them one to the other as I showed in the paper.

This doesn't answer my question, because I can't make what you're describing here give an answer that resolves the discrepancy. I don't understand how to relate what you are saying in the paper to what I am calling $M_R$ and $M_L$, or how what you are describing in the paper corrects the discrepancy between the two. The only sense I can make of "two different measurements of mass for one and the same matter" gives an answer that makes the discrepancy worse, not better, for the reason I gave in post #65 (it doesn't change $M_L$ and it makes $M_R$ larger, not smaller). So I'm confused. I am hoping that if you give explicit answers to the two questions I gave, it will help to resolve, or at least reduce, my confusion.

 

[PeterDonis]

The only sense I can make of "two different measurements of mass for one and the same matter" gives an answer that makes the discrepancy worse, not better, for the reason I gave in post #65 (it doesn't change $M_L$ and it makes $M_R$ larger, not smaller).

Actually, on thinking this over some more, I think I have misstated this a bit. Including non-Newtonian effects of the kind implied by "two different measurements of mass for one and the same matter" (which means correcting for things like spatial curvature) should not change either $M_L$ or $M_R$. What it should change is our calculation of how much proper spatial volume the mass occupies, i.e., it should change our estimate of the average density (more precisely, proper density, the density measured by an observer locally inside the galaxy) of the matter in a galaxy, as compared to a Newtonian calculation (our estimate of average proper density should be reduced--more spatial volume for the same mass). But it should not change the mass we infer from rotation curves or luminosity at all, because those estimates are independent of our estimate of the average density.

 

[PeterDonis]

Including non-Newtonian effects of the kind implied by "two different measurements of mass for one and the same matter" (which means correcting for things like spatial curvature) should not change either $M_L$ or $M_R$.

On further thought, this way of putting it, while it is correct, might not really get at the issue I'm trying to describe. So let me try it another way.

Suppose we know $M_R$ for some galaxy but we don't know $M_L$ (say we can't see the galaxy directly because it's obscured by a dust cloud, but we've been sent rotation curve data for the galaxy by some alien civilization that isn't behind the dust cloud). What value for $M_L$ would we predict from our knowledge of $M_R$? Or, to put it another way that makes the logic clearer, what value for total luminosity for the galaxy would we predict from our knowledge of $M_R$, if we assume that all the matter in the galaxy is luminous (stars) and has similar properties to stars in our own galaxy?

The Newtonian prediction is simple: we expect $M_L = M_R$, so we just apply some expected distribution of stellar luminosities, plug those into an integral for total luminosity, and use known mass-luminosity relationships to apply the appropriate weighting factors in the integral so that the total mass, given our assumed distribution of stellar luminosities (which we can translate into an assumed distribution of stellar masses) comes out to $M_L$. This kind of calculation, since it gives an answer for total luminosity that is significantly larger than the total luminosity we actually observe, is the basic argument used by proponents of dark matter: there must be non-luminous matter present to make up the total mass that is needed to account for the observed rotation curves.

Since in actual fact we observe $M_L < M_R$ by some significant factor, if we want to avoid dark matter (and if we also want to avoid modifying our theory of gravity, which is what the paper under discussion wants to do--it wants to find a solution within GR), we need to find some non-Newtonian effect that would modify the above prediction procedure. The first obvious non-Newtonian effect to consider is gravitational binding energy: in Newtonian gravity, binding energy doesn't affect mass, but in GR, it does. However, this effect is in the wrong direction: it leads us to expect $M_L > M_R$ in the above prediction procedure (i.e., it leads us to expect a larger total luminosity than what we would infer by assuming $M_L = M_R$ in the above procedure), because gravitational binding energy is negative; the mass measured "from the outside" by something like rotation curves is smaller than the mass measured "from the inside", by an observer locally that is next to some particular star, and that locally measured mass is what is correlated with the luminosity in our known mass-luminosity relationships. This kind of effect is what I was thinking of in post #65, but I incorrectly mixed it up with space curvature.

A second non-Newtonian effect to consider is space curvature; but as I noted in my previous post (quoted above), that doesn't affect either $M_R$ or $M_L$ in the above prediction procedure (i.e., it doesn't affect the total luminosity we would infer from rotation curve data). It just affects the proper volume we assign to the galaxy, which means it affects the average density we expect a local observer, inside the galaxy, to measure.

So neither of those non-Newtonian effects can account for our observation that $M_L < M_R$. And I am not aware of any other non-Newtonian effect that would be significant in this scenario, nor does the paper appear to me to suggest one; it only suggests one of the above two, neither of which work.

 

[RUTA]

Sorry for the confusion, Peter, let me try one more time to clarify what we did

When you adjoin the FRW and Schwarzschild solutions, the comparative mass can be equal, larger, or smaller, and the matter can be surrounded by vacuum or vice-versa, as I explain in the corresponding AJP paper. That fact alone is used heuristically as follows.

$M_R$ is inferred from orbital speeds (or other data in the cases of mass profiles of X-ray clusters and anisotropies in the angular power spectrum of the cosmic microwave background) by assuming Newtonian gravity supplies the centripetal acceleration for UCM of the orbiting stars and gas. When the orbital speeds are measured (via redshifts) we find $M_R$ is much larger than $M_L$. So, we are considering a correction to Newtonian gravity for a situation that otherwise doesn't seem to warrant it (very small spatial curvature). The correction we proposed is simply to replace $M_L$ in the Newtonian acceleration with a corrected value, since the mass of the matter responsible for the acceleration is being measured in two different ways and GR allows for simultaneously differing mass values for one and the same matter. We found a functional form for correcting $M_L$ that rivals or beats all competitors across three different astronomical matter distributions -- galactic, galactic cluster, and cosmological. That is interesting because no other approach works as well across all three distributions. The rivals we compared are:

1. Two different DM distribution models (Burkett and NFW). The functional forms for these DM distributions are not based on any knowledge of the physics for these hypothetical and unlikely (as shown by Carroll) particles.
2. Correction to Newtonian physics (MOND). The ad hoc change of Newtonian acceleration at large scales. There is a relativistic counterpart for this now, but it's ugly and does not satisfy local conservation (not divergence-free).
3. Two different corrections to GR (MSTG and STVG). These are also otherwise unmotivated and do not satisfy local conservation.

Again, none of the rivals match our fits using our simple functional form for the correction of $M_L$ across all three matter distributions. Keep in mind that we're not talking about a new phenomenon here. The missing mass phenomenon was introduced in the 1930's (e.g., Zwicky, F: On the masses of nebulae and clusters of nebulae. The Astrophysical Journal 86, 217-246 (1937)). So, after 80+ years these are still our best guesses.

Conclusion, maybe it's reasonable to consider the idea from GR that matter can simultaneously possesses different values of mass based on spatially different measurement contexts. We already know it's true for different temporal contexts, e.g., free neutron mass greater than bound neutron mass. So, is this such a stretch?

That's the best I can do, Peter. Hope it suffices.

 

[PeterDonis]

That fact alone is used heuristically

This is probably where I see the disconnect.

First, as I think I've said before, I don't think "heuristically" is enough. You can't just assume the effect you want to be there actually is there in a solution that is applicable to a galaxy and our observations of it. You have to show that the effect is there and of the right general order of magnitude. Just assuming it's there because it appears to be there in a different solution is not enough.

Second, the "fact" you are talking about, even in the solution you explicitly examine (collapsing FRW surrounded by Schwarzschild vacuum surrounded by expanding FRW), is not an effect that produces what you are looking for, as you are describing it later in your post. More on that below.

The correction we proposed is simply to replace $M_L$ in the Newtonian acceleration with a corrected value, since the mass of the matter responsible for the acceleration is being measured in two different ways and GR allows for simultaneously differing mass values for one and the same matter

This is simply invalid handwaving. "GR allows for simultaneously differing mass values for one and the same matter" is not a magic wand. It's a specific statement about a specific pair of measurements, and it has a specific effect, and that effect is not what you're looking for.

A correct application of "GR allows for simultaneously differing mass values for one and the same matter" would look like this:

The mass $M_L$, because it is obtained from observed luminosities, is a sum of "locally measured" masses--masses that would be measured by an observer in the same local region of the galaxy as the stars whose luminosities are being observed. Those are the masses that appear in the mass-luminosity relationships that are being used.

The mass $M_R$, because it is obtained from observed rotation curves, is a sum of "externally measured" masses--masses that would be measured by an observer in the vacuum region outside the system. (There are some technicalities to this, but I think it's reasonable for the case under consideration.)

GR allows "externally measured" masses to be different from "locally measured" masses for systems like galaxies, because the latter include the effects of gravitational binding energy while the former do not. But that effect, as I've already noted, is in the wrong direction: "locally measured" masses are larger than "externally measured" masses, not smaller. So if the only matter in a galaxy is luminous matter, we would expect a GR correction to make $M_L > M_R$, which is the opposite of what we need. (Also, the magnitude of this correction is small; it is of rough order of magnitude $G M / c^2 R$, where $R$ is some appropriate value for the radius of the galaxy. For all galaxies we know of, this correction is a tiny fraction of a percent at best.)

GR also includes spatial curvature, which is not included in the standard Newtonian models of galaxies, but as I've already said, this does not affect either $M_R$ or $M_L$; it only affects our estimate of average density.

There is no other GR effect I know of that is applicable here. The only other thing you discuss in the paper that seems at all relevant is the claim on p. 5, after equation (7), that observers in the exterior FRW region will somehow measure $M_p$ instead of $M$; I have already explained why I don't find that claim to be valid. The only thing I would add to that here is that, as far as I can tell, any such effect, if it were valid, would affect how we infer $M_R$ from observations, not how we infer $M_L$; but you are saying in what I've quoted above that your claimed effect changes how we infer $M_L$.

We found a functional form for correcting $M_L$ that rivals or beats all competitors across three different astronomical matter distributions -- galactic, galactic cluster, and cosmological

As an empirical finding, this is fine. But it does not support any claim that there is a valid GR correction that will produce such a functional form. I don't see how there can be one, for the reasons given above. And as I've already remarked, and you have agreed, you are not deriving your functional form from any underlying GR equations; you are just assuming it as an ansatz and seeing how it fits the data. So the fact that it fits the data well does not provide any support for the claim that there is in fact a valid GR correction that leads to your ansatz.

So if your functional form turns out to be valid (i.e., if it doesn't turn out to be just another way of representing the effects of dark matter), I think it will be because it is a reasonable approximation to some underlying effect that is not present in GR, but is present in some modified theory (possibly derived from quantum gravity) that includes effects that are not present in GR. (I personally think this is extremely unlikely, but that's just my opinion; once we actually have a working theory of gravity, possibly quantum gravity, that goes beyond GR, we'll see what it says.)

 

[ohwilleke]

So it sounds like this is basically a discovery of an empirical formula that works well with broad applicability that is only dimly motivated by very top level concepts in GR, which doesn't mean that it isn't potentially a big deal, or that it might be possible to reverse engineer the formula to determine what kind of gravitational effect is necessary to produce this formula.

How does this compare to the works of Deur who derives a similar effect from the self-interactions of gravitons a naive effort to build a quantum gravity LaGrangian, more or less from first principles and informed by an analogy to parallel QCD equations (although his approach is not inherently quantum in nature and can also be described classically in terms of the self-interactions of a classical gravitational field)?

The formula seems very different but the result seems to be very similar.

 

[RUTA]

This is probably where I see the disconnect.

First, as I think I've said before, I don't think "heuristically" is enough. You can't just assume the effect you want to be there actually is there in a solution that is applicable to a galaxy and our observations of it. You have to show that the effect is there and of the right general order of magnitude. Just assuming it's there because it appears to be there in a different solution is not enough.

The judges at the Gravity Research Foundation, journal referees, and journal editors disagree with you there, as it received Honorable Mention and was published.

Second, the "fact" you are talking about, even in the solution you explicitly examine (collapsing FRW surrounded by Schwarzschild vacuum surrounded by expanding FRW), is not an effect that produces what you are looking for, as you are describing it later in your post. More on that below.

This is simply invalid handwaving. "GR allows for simultaneously differing mass values for one and the same matter" is not a magic wand. It's a specific statement about a specific pair of measurements, and it has a specific effect, and that effect is not what you're looking for.

A correct application of "GR allows for simultaneously differing mass values for one and the same matter" would look like this:

The mass $M_L$, because it is obtained from observed luminosities, is a sum of "locally measured" masses--masses that would be measured by an observer in the same local region of the galaxy as the stars whose luminosities are being observed. Those are the masses that appear in the mass-luminosity relationships that are being used.

The mass $M_R$, because it is obtained from observed rotation curves, is a sum of "externally measured" masses--masses that would be measured by an observer in the vacuum region outside the system. (There are some technicalities to this, but I think it's reasonable for the case under consideration.)

GR allows "externally measured" masses to be different from "locally measured" masses for systems like galaxies, because the latter include the effects of gravitational binding energy while the former do not. But that effect, as I've already noted, is in the wrong direction: "locally measured" masses are larger than "externally measured" masses, not smaller. So if the only matter in a galaxy is luminous matter, we would expect a GR correction to make $M_L > M_R$, which is the opposite of what we need. (Also, the magnitude of this correction is small; it is of rough order of magnitude $G M / c^2 R$, where $R$ is some appropriate value for the radius of the galaxy. For all galaxies we know of, this correction is a tiny fraction of a percent at best.)

GR also includes spatial curvature, which is not included in the standard Newtonian models of galaxies, but as I've already said, this does not affect either $M_R$ or $M_L$; it only affects our estimate of average density.

You've totally misunderstood what was published. Your analysis is so far off the mark, I would have to reproduce most of the paper to correct it here. Think carefully about your assertion, Peter. You're claiming that the authors, judges, referees, and editors all missed the fact that the application of the effect was backwards. But, it's obvious to you. Doesn't that give you pause at all?

There is no other GR effect I know of that is applicable here.

Is that your basis for a no-go theorem?

As an empirical finding, this is fine. But it does not support any claim that there is a valid GR correction that will produce such a functional form. I don't see how there can be one, for the reasons given above.

Unfortunately, the reasons given above are totally misguided.

And as I've already remarked, and you have agreed, you are not deriving your functional form from any underlying GR equations; you are just assuming it as an ansatz and seeing how it fits the data. So the fact that it fits the data well does not provide any support for the claim that there is in fact a valid GR correction that leads to your ansatz.

That is true.

So if your functional form turns out to be valid (i.e., if it doesn't turn out to be just another way of representing the effects of dark matter), I think it will be because it is a reasonable approximation to some underlying effect that is not present in GR, but is present in some modified theory (possibly derived from quantum gravity) that includes effects that are not present in GR. (I personally think this is extremely unlikely, but that's just my opinion; once we actually have a working theory of gravity, possibly quantum gravity, that goes beyond GR, we'll see what it says.)

Do you have any calculations or references to support your beliefs here? Because the reasons given above are totally erroneous. You have totally misunderstood the paper and I don't have the time to help you there, my friend.

 

[RUTA]

So it sounds like this is basically a discovery of an empirical formula that works well with broad applicability that is only dimly motivated by very top level concepts in GR, which doesn't mean that it isn't potentially a big deal, or that it might be possible to reverse engineer the formula to determine what kind of gravitational effect is necessary to produce this formula.

How does this compare to the works of Deur who derives a similar effect from the self-interactions of gravitons a naive effort to build a quantum gravity LaGrangian, more or less from first principles and informed by an analogy to parallel QCD equations (although his approach is not inherently quantum in nature and can also be described classically in terms of the self-interactions of a classical gravitational field)?

The formula seems very different but the result seems to be very similar.

I'll check that out, thnx.

 

[PeterDonis]

The judges at the Gravity Research Foundation, journal referees, and journal editors disagree with you there, as it received Honorable Mention and was published.

I don't accept arguments from authority. In fact, when I see someone retreat into an argument from authority, my Bayesian prior is to raise my estimate of the probability that their claims are mistaken. Just to help you calibrate your estimate of me, I posted a thread in the relativity forum not too long ago proposing that an argument by Schild that is presented in MTW is erroneous. The thread is linked below if you care to read it; there is quite a bit of good discussion by a number of PF members, several of whom raised good points I had not thought of:

https://www.physicsforums.com/threa...me-dilation-imply-spacetime-curvature.919181/

You've totally misunderstood what was published.

If that's the only response you can give, I'm afraid we have reached an impasse. But I'll try and frame a simpler question that might elicit a more helpful response from you in a follow-up post.

You're claiming that the authors, judges, referees, and editors all missed the fact that the application of the effect was backwards. But, it's obvious to you. Doesn't that give you pause at all?

No. I have no idea who these people are or what expertise they have in GR.

I won't respond to the rest of your post since I don't see any basis there for a constructive discussion. But, as I said, I'll try to frame a simpler question in a follow-up post.

 

[PeterDonis]

Here is my attempt at framing a simpler question. The following quote is from p. 5 of the paper:

The spacetime geometry of the surrounding FLRW dust will be unaffected by the intervening Schwarzschild vacuum, so observers in the surrounding FLRW dust (global context) will obtain the “globally determined” proper mass $M_p$ for the collapsed dust ball while observers in the Schwarzschild vacuum (local context) will obtain the “locally determined” dynamic mass $M$ for the collapsed dust ball.

The question is this: how will each of these observers obtain the masses they are said to obtain in the above?

I'll give what I understand to be the answer for the observer in the Schwarzschild vacuum region: this observer puts a test object into orbit about the "galaxy" (which in this model is actually a collapsing FLRW dust region, but let's ignore that and assume it's a stationary compact region like a galaxy) and measures its orbital parameters, and uses the well-known equations for orbits in Schwarzschild spacetime to derive the mass $M$ of the central object.

So to rephrase the question: first, is my understanding above correct? And if it isn't, what is the correct description of how the observer in the Schwarzschild vacuum region will measure his $M$?

And second, how will the other observer, the one in the surrounding FLRW dust region, measure $M_p$? What I am looking for is an explicit description of a measurement procedure similar to what I described above for the Schwarzschild observer. I have speculated about this in previous posts, but since you are saying I have misunderstood the paper, I will refrain from speculating. I would like you (@RUTA) to tell me.

 

[PeterDonis]

You've totally misunderstood what was published.

Btw, I should clarify something: nothing I have said should be taken as claiming that this statement just quoted is wrong. In fact I don't understand the claims being made in the paper about things like "globally determined" vs. "locally determined" mass, or how an observer in the surrounding FLRW dust region in what I quoted in my previous post just now can measure $M_p$. What I am trying to figure out is whether I don't understand because I've missed something, or because the paper is actually wrong in its claims about the existence of an effect within standard GR that has the necessary properties.

So far, the responses I have gotten have moved me in the direction of "the paper is actually wrong", but that's still just opinion on my part because I still have not gotten a response which helps me to make sense of the parts of the paper that I can't understand. In my previous post I tried to frame a simple question that focuses on one particular part that I can't understand, in the hope that I will get a response that helps me to understand it. I may still not agree with it even after I understand it, but I would much prefer, if I am going to end up disagreeing, to be able to do so with confidence that I understand the claim I am disagreeing with. That is why I have persisted in asking questions.

 

[PeterDonis]

How does this compare to the works of Deur

A more pertinent paper by Deur for this discussion might be this one:

https://arxiv.org/pdf/0901.4005.pdf

This is ref. 3 in the paper linked to in the quote above, and appears to be the original paper presenting his proposed effect and estimating its impact on galaxy rotation curves.

 

[RUTA]

Let me review the scholarly process at work here. We have a *community* of scholars who work in a particular field and they have "authorities," e.g., journal editors and contest judges. When you believe you have something of interest to this community, you write it up and submit it too that community's "judicial institutions," e.g., journals and contests. Other members of the community (your colleagues) vet your work and the authorities then decide if it should be disseminated or otherwise recognized. If you read something that has passed this vetting process and been distributed by this community and you feel it should be clarified or corrected, you write up your idea and subject it to the same process within that community. If your colleagues and the authorities agree, they distribute it to the community so everyone may benefit from your clarifications and/or corrections. I've worked on both sides of this process, i.e., I've had papers published and/or recognized and I've published refutations of publications. It's a long process and it takes lots of work.

You may not respect the authorities and/or your colleagues in the community, but you nonetheless have to get them to sign off on your ideas if you want your ideas distributed and/or recognized by that community. I understand PF only allows Insights based on ideas that have successfully passed this process. My Insight is based 100% on that process. I have not seen you post any references refuting anything in my Insight that have passed that process. All I've seen from you are value judgments and unsupported beliefs regarding what is a highly tangential point of the Insight, i.e., principle explanation in modern physics. For example, what do you think about the ScienceX News article I linked earlier?

If you can cite a no-go theorem having passed the scholarly process, you will save me a lot of time in the future. Otherwise, you're wasting a lot of my time responding to your unsupported beliefs and value judgments. I'm sorry, I just can't spare the time in that direction, Peter.

 

[RUTA]

I read the Deur arXiv paper and found it interesting. I would like to see their fits of X-ray cluster mass profiles, since that's where MOND fails miserably and MOND also works well with galactic rotation curves. I would like to see their fits of the type Ia SN data and the Planck CMB anisotropy data, since they claim to account for dark energy effects. The work is highly speculative of course, since it's based on a direct quantization of GR which we know doesn't work. But, at least it provides an exact functional form and that form might be approximately produced from whatever QG theory we ultimately obtain.

 

[PeterDonis]

Let me review the scholarly process at work here.

I am not trying to criticize or disparage the scholarly process. I am certainly not trying to claim that the journal should not have published your paper. That is entirely up to them. I am also not at all saying that your Insights article should not have been written or that PF should not have published it.

I am just trying to understand the heuristic argument you are making in the paper regarding the presence of a GR effect with the claimed properties. Lecturing me on the scholarly process does not help me with that at all. What would help me with that would be if you would answer the questions I posed in post #76. If you're not going to do that, I'll just bow out of the discussion since I have nothing further either to gain from it or to contribute to it.

 

[PeterDonis]

All I've seen from you are value judgments and unsupported beliefs

No, that's not all you have seen from me. You have also seen specific, simple questions from me. You have not answered my latest one, in post #76. Can you answer it?

regarding what is a highly tangential point of the Insight, i.e., principle explanation in modern physics

Most of what I have posted in this discussion has not been about that at all. It has been about the GR effect claimed in your paper which I have not been able to understand.

 

[PeterDonis]

You're claiming that the authors, judges, referees, and editors all missed the fact that the application of the effect was backwards.

You're misunderstanding my point here. I am not saying that the application of your claimed GR effect in the paper was backwards. I am saying that the only GR effect I can come up with that could apply to $M_L$, which is where you say the change needs to happen, is in the opposite direction from what it would need to be to resolve the issue your claimed effect is supposed to resolve. That observation in itself doesn't tell me that anything specific in the paper is wrong; it just tells me that, whatever your claimed GR effect is, if it exists, it can't be any of the ones I can come up with. Which is why I keep asking questions to try to help me figure out what your claimed GR effect is, since if it exists it must be something different from any of the ones I have come up with.

 

[PeterDonis]

The work is highly speculative of course, since it's based on a direct quantization of GR which we know doesn't work.

Actually, from what I can see, the effects described in the 2009 Deur paper I linked to, and the 2020 paper @ohwilleke linked to, are classical effects and should be present in a classical GR model. His investigation was motivated by considering graviton-graviton interactions in a quantum field theory of a spin-2 field, but the actual Lagrangian he presents in the 2009 paper is classical; it's just a power series expansion of the standard Einstein-Hilbert Lagrangian around a zero order flat metric.

It seems to me that there are basically two classical effects he is describing:

(1) Nonlinearity in the Einstein Field Equation, which leads to terms in a post-Newtonian expansion that amount to adding a $\ln(r)$ term to the Newtonian potential, which in turn adds a $1 / r$ term to the Newtonian force, which is basically the same thing that MOND does, but now without requiring any modification to GR;

(2) Non-sphericity, the fact that a galaxy is a flattened disc and not a sphere, which, according to Deur, prevents different nonlinear effects under #1 above from canceling out. If this is correct, it is very interesting, because it would mean that the effects he is talking about would not be visible in a spherically symmetric model of the sort I have been considering in framing the questions I've asked. Which unfortunately makes checking the whole thing a lot harder, since there are no known closed form solutions for the flattened disc case (which is why Deur has to rely on numerical simulations).

 

[PeterDonis]

I would like to see their fits of X-ray cluster mass profiles, since that's where MOND fails miserably and MOND also works well with galactic rotation curves. I would like to see their fits of the type Ia SN data and the Planck CMB anisotropy data, since they claim to account for dark energy effects.

These are good points, I would like to see the same things for Deur's proposed model.

 

[PeterDonis]

what do you think about the ScienceX News article I linked earlier?

I'm not sure about all aspects of the analogy between SR and QM that is described in the paper.

I agree that all observers in relativity having to measure $c$ for the speed of light, regardless of their state of motion, is analogous to all observers in QM having to measure $\pm \hbar / 2$ for spin, regardless of their choice of measurement direction. And I agree that the latter fact requires that, when analyzing conservation of angular momentum in QM, the best we can possibly do is the "average conservation" that the paper describes.

I'm not sure how length contraction or time dilation correspond to the spin "corrections" that have to be made to verify "average conservation", since length and time aren't conserved quantities and the contracted lengths and dilated times that a given observer assigns to objects in motion relative to him are not "corrections" applied to any calculation of conservation.

I'm wondering, though, if the latter issue could be addressed by looking at energy and momentum instead of time and length, since they are "corrected" by the same factors and they are conserved quantities. That would still leave as a difference between SR and QM the fact that the SR conservation laws are not average only.

 

[ohwilleke]

I read the Deur arXiv paper and found it interesting. I would like to see their fits of X-ray cluster mass profiles, since that's where MOND fails miserably and MOND also works well with galactic rotation curves. I would like to see their fits of the type Ia SN data and the Planck CMB anisotropy data, since they claim to account for dark energy effects. The work is highly speculative of course, since it's based on a direct quantization of GR which we know doesn't work. But, at least it provides an exact functional form and that form might be approximately produced from whatever QG theory we ultimately obtain.

There is a complete annotated bibliography here.

 

[ohwilleke]

I would like to see their fits of the type Ia SN data and the Planck CMB anisotropy data, since they claim to account for dark energy effects.

One of the pieces of the @RUTA paper that I found particularly interesting was the CMB fit and I'm still trying to get a better handle on how that piece was done from a nuts and bolts perspective.

Deur has done some of what you are wondering about in his papers, although only at a back of napkin level.

But, Deur hasn't done the CMB piece. I corresponded with Deur about that and it turns out that the main reason is that he has a day job doing QCD physics at Jefferson Labs (some of his best work there is on bridging the boundary between non-perturbative and perturbative QCD methods), but has no funding for his gravity work (which is outside what is employer does and outside his subspecialty in physics) and he simply hasn't had the resources to do a big project like that in his spare time.

He did publish this week a detailed 117 page preprint spelling out his previous findings that apparently dark matter to ordinary matter ratios in elliptical galaxies are strongly correlated with the extent to which they are non-spherical using a decent sized sample, something that no other dark matter particle or modified gravity theory of which I am aware predicts, but which flows naturally from his approach as a prediction.

Deur's dark energy concept is very interesting because unlike almost all other dark energy theories it doesn't require any new substance and doesn't raise conservation of mass-energy issues the way that GR does which makes it particularly attractive in a potential quantum gravity theory.

Instead, he posits that the gravitational field of an object gets semi-confined within a system where dark matter phenomena are observed (much like gluons are largely confined within hadrons) and that this limits the amount of that object's gravitational field that escapes that system, thereby reducing the strength of the gravitational fields between systems. The weaker fields between systems look like dark energy. This explains why inferred total amount of dark energy estimates are of the same order of magnitude as inferred total amount of dark matter estimates (i.e. the coincidence problem).

Also, this means that unlike GR and most modified gravity theories, there is no need for a fundamental constant to quantify dark energy, so his approach actually has one less free parameter than GR with a cosmological constant (at least in principle).

 

[PeterDonis]

There is a complete annotated bibliography here.

I'm a little confused by this statement in the article:

"Deur's approach does not reproduce the conclusions of conventional classical General Relativity in the weak gravitational fields and spherically asymmetric systems where it dark matter and dark energy phenomena are observed"

At least as regards the effects I described in post #84 (particularly the first one), I don't see how this is correct. AFAIK it is perfectly true that conventional models of galaxies, the ones in which the discrepancy between mass inferred from luminosity and mass inferred from rotation curves is observed, are Newtonian and do not include any post-Newtonian terms, which means they do not include any effects of nonlinearity in the EFE. Those post-Newtonian terms and nonlinear effects are certainly present in principle, and in this respect Deur simply seems to be arguing that, contrary to the assumption underlying conventional models, those effects are not in fact negligible for galaxies. Since the magnitude of those effects is extremely hard to estimate from first principles (it's not feasible to numerically solve the Einstein-Infeld-Hoffman equations for a system of $10^{11}$ bodies), the arguments underlying the conventional assumption that they are negligible are heuristic, and so proposing a model that challenges those assumptions does not strike me as being inconsistent with GR.

Some of the other effects mentioned (such as the confinement invoked to account for dark energy effects) are not, as I understand it, present at all in classical GR, so the article's remark would apply to those; but the article doesn't seem to be drawing any distinction of this kind, it just seems to be making a blanket statement that none of Deur's claimed effects are present in classical GR, and that seems to me to be too strong.

 

[PeterDonis]

there is no need for a fundamental constant to quantify dark energy, so his approach actually has one less free parameter than GR with a cosmological constant

This struck me when I was reading the article you linked to; I think this is a very nice feature of the model.

 

[PeterDonis]

doesn't raise conservation of mass-energy issues the way that GR does

Can you elaborate on this?

 

[ohwilleke]

I'm a little confused by this statement in the article:

"Deur's approach does not reproduce the conclusions of conventional classical General Relativity in the weak gravitational fields and spherically asymmetric systems where it dark matter and dark energy phenomena are observed"

At least as regards the effects I described in post #84 (particularly the first one), I don't see how this is correct. AFAIK it is perfectly true that conventional models of galaxies, the ones in which the discrepancy between mass inferred from luminosity and mass inferred from rotation curves is observed, are Newtonian and do not include any post-Newtonian terms, which means they do not include any effects of nonlinearity in the EFE. Those post-Newtonian terms and nonlinear effects are certainly present in principle, and in this respect Deur simply seems to be arguing that, contrary to the assumption underlying conventional models, those effects are not in fact negligible for galaxies. Since the magnitude of those effects is extremely hard to estimate from first principles (it's not feasible to numerically solve the Einstein-Infeld-Hoffman equations for a system of $10^{11}$ bodies), the arguments underlying the conventional assumption that they are negligible are heuristic, and so proposing a model that challenges those assumptions does not strike me as being inconsistent with GR.

Some of the other effects mentioned (such as the confinement invoked to account for dark energy effects) are not, as I understand it, present at all in classical GR, so the article's remark would apply to those; but the article doesn't seem to be drawing any distinction of this kind, it just seems to be making a blanket statement that none of Deur's claimed effects are present in classical GR, and that seems to me to be too strong.

I've seen some statements in for example, Misner and Thorne's textbook "Gravitation", to the effect that self-interactions of a gravitational field cannot be an independent source of gravitational effects, that gravitational energy cannot be localized, and other details that don't seem to be consistent with Deur's approach. They look like no go theorems inconsistent with his approach but that may simply over read what they really mean.

A phrase that I like to use is that Deur's approach is different than GR as conventionally operationalized. All of his assumptions are plain vanilla in any attempt to quantize gravity from a GR foundation (which motivates his research method and makes his approach more obvious, even though, as you correctly note and one of his later papers explains, there is nothing in his conclusions that is inherently non-classical).

Deur also uses a scalar approximation of what are really tensor fields, so that it is possible to do the math, but makes a good case that this approximation for calculation purposes doesn't impact the result very much in systems that are close to equilibrium.

I've seen several papers arguing that GR should have very few post-Newtonian effects at the galaxy and larger scale, but agree with you that these conclusions aren't very rigorous.

 

[ohwilleke]

Can you elaborate on this?

While mass-energy is conserved locally in GR, there is debate over whether the cosmological constant amounts to violation of conservation of mass-energy as the amount of dark energy increases when the volume of the universe does, or whether that is really a trade off between gravitational potential energy of some sort and dark energy. You probably understand that debate better than I do.

Deur's approach, because it doesn't have a cosmological constant which is the only mass-energy conservation violating term in GR, has both local and global conservation of mass-energy. Dark energy phenomena arise from a lack of gravitational energy holding galaxies together in his approach since the energy that would do that is used to create dark matter phenomena instead, not from something extra pulling them apart, relative to the no cosmological constant conventionally applied GR status quo.

This is good for a quantum gravity theory because in a quantum gravity theory you'd like to have everything arise locally and no global effects like the cosmological constant. If you can fit all phenomena into the action of your graviton, you have a much easier problem.

 

[PeterDonis]

there is debate over whether the cosmological constant amounts to violation of conservation of mass-energy as the amount of dark energy increases when the volume of the universe does, or whether that is really a trade off between gravitational potential energy of some sort and dark energy

That debate isn't just over the dark energy case, although that's the case Sean Carroll chose to use to illustrate the issue in his blog post about "energy is not conserved". The debate applies to any spacetime that is not stationary, including the many non-stationary spacetimes with no cosmological constant (such as all of the FRW spacetimes with no cosmological constant).

So while I agree that not having to have a cosmological constant is a nice feature, I don't think Deur's model "solves" any general problem about "mass-energy not being conserved in GR". The same problem, if you think it's a problem, is there in FRW spacetime with no cosmological constant, which is basically where Deur's model would end up as a model of the universe as a whole (modulo some corrections due to the other effects in his model, that also don't affect the "conservation" issue as far as I can see).

This is good for a quantum gravity theory because in a quantum gravity theory you'd like to have everything arise locally and no global effects like the cosmological constant.

The cosmological constant in GR is not "global"; it's just non-dynamical--it's an extra effective energy density that is just there regardless of anything else that happens. In quantum field theory it just corresponds to a nonzero vacuum expectation value of energy, which is a perfectly good local quantity.

The last sentence leads to what I think is a better way to describe what problem is solved by not having to have a cosmological constant. All attempts to estimate from QFT what a nonzero vacuum expectation value of energy should be, if there is one, come up with answers 120 or so orders of magnitude larger than the observed value they are supposed to be explaining. Deur's model makes that problem go away, which is certainly nice, but again, I don't think "solving a problem with mass-energy not being conserved" is a good way to describe why it's nice; "eliminating the problem of the huge mismatch between theoretical and experimental values of the cosmological constant" would be better.

 

[PeterDonis]

I've seen some statements in for example, Misner and Thorne's textbook "Gravitation", to the effect that self-interactions of a gravitational field cannot be an independent source of gravitational effects, that gravitational energy cannot be localized, and other details that don't seem to be consistent with Deur's approach. They look like no go theorems inconsistent with his approach but that may simply over read what they really mean.

The bolded phrase is correct. I wrote up a series of Insights articles on this very topic:

https://www.physicsforums.com/insights/does-gravity-gravitate/

The short version is, the answer to the title question (does gravity gravitate?) can be either yes or no, depending on how you interpret it. The things MTW is talking about are part of the interpretation of the question that leads to a no answer. But the way Deur is using nonlinear effects is part of the interpretation of the question that leads to a yes answer. Both interpretations are valid; they just show that the question itself as originally stated is ambiguous, and the ambiguity can be resolved into two different questions that have different answers.

 

[Jimster41]

The Tsirelson bound is the most QM can violate the Bell inequality known as the CHSH inequality. Classical physics says the CHSH quantity must reside between $\pm 2$, but the Bell states give $\pm 2 \sqrt{2}$ (the Tsirelson bound). Superquantum correlations respect no-superluminal-signaling and give a CHSH quantity of 4. So, quantum information theorists want to know "Why the Tsirelson bound?" That is, why doesn't Nature produce superquantum correlations? Our answer is "conservation per NPRF." Of classical, QM, and superquantum, only QM satisfies this constraint.

I had heard of CHSH but there was a lot in that answer I didn't understand at all. In fact I hadn't even heard of "superquantum correlations". This paper was a pretty good intro to the idea... in case it's valuable to anyone else.

Maybe those variables are hidden by the 5D aliens so we won't realize there is no such thing as time and will keep trying to make lots of important decisions (that's a joke, in case it's not clear).

https://arxiv.org/abs/1205.1162
Classical, quantum and superquantum correlations
GianCarlo Ghirardi, Raffaele Romano

A deeper understanding of the origin of quantum correlations is expected to shred light on the physical principles underlying quantum mechanics. In this work, we reconsider the possibility of devising "crypto-nonlocal theories", using a terminology firstly introduced by Leggett. We generalize and simplify the investigations on this subject which can be found in the literature. At their deeper level, such theories allow nonlocal correlations which can overcome the quantum limit.

 

[RUTA]

I had heard of CHSH but there was a lot in that answer I didn't understand at all. In fact I hadn't even heard of "superquantum correlations". This paper was a pretty good intro to the idea... in case it's valuable to anyone else.

Maybe those variables are hidden by the 5D aliens so we won't realize there is no such thing as time and will keep trying to make lots of important decisions (that's a joke, in case it's not clear).

https://arxiv.org/abs/1205.1162
Classical, quantum and superquantum correlations
GianCarlo Ghirardi, Raffaele Romano

You might also like to read this Insight which explains an "unreasonable consequence" of superquantum correlations as presented in Bub and Bub's book.

I'm not surprised you haven't heard of superquantum correlations. I started working in foundations in 1994 and didn't hear about superquantum correlations until 2018. We published a book on foundations of physics in 2018 and Jeff Bub asked us to give a talk on it for his seminar. After a few hours of discussion we were walking from the restaurant to our car when Bub said, "What I really want to know is, Why don't we observe superquantum correlations? They don't violate no-superluminal-signaling, so why are they not found in Nature?" Silberstein and I didn't know what he was talking about. Answering his question (they violate "conservation per NPRF") is what ultimately led to this Insight.

 

[RUTA]

I'm not sure about all aspects of the analogy between SR and QM that is described in the paper.

I agree that all observers in relativity having to measure $c$ for the speed of light, regardless of their state of motion, is analogous to all observers in QM having to measure $\pm \hbar / 2$ for spin, regardless of their choice of measurement direction. And I agree that the latter fact requires that, when analyzing conservation of angular momentum in QM, the best we can possibly do is the "average conservation" that the paper describes.

I'm not sure how length contraction or time dilation correspond to the spin "corrections" that have to be made to verify "average conservation", since length and time aren't conserved quantities and the contracted lengths and dilated times that a given observer assigns to objects in motion relative to him are not "corrections" applied to any calculation of conservation.

I'm wondering, though, if the latter issue could be addressed by looking at energy and momentum instead of time and length, since they are "corrected" by the same factors and they are conserved quantities. That would still leave as a difference between SR and QM the fact that the SR conservation laws are not average only.

The "conservation part" of the mystery of entanglement is not found in the mysteries of time dilation and length contraction. The fact we are pointing out in our Scientific Reports paper (as outlined in the ScienceX News article) is that all of these mysteries stem from the application of the relativity principle ("no preferred reference frame" NPRF) to a fundamental constant. And while this principle explanation of the mysteries is true (principle explanation = mathematical consequences of empirical facts), there are still no (consensus) constructive accounts. And these mysteries are very very old. So, what do we make of these facts?

As I suggest in the ScienceX News article, perhaps we don't always need an explanation based on a causal mechanism. That's where the ScienceX News article ends, but we go further in our Scientific Reports paper. There we suggest that principle explanation is just as valid as constructive explanation when physics is viewed per Mermin's QBism (cited therein):

Laws of science are the regularities we have discerned in our individual experiences, and agreed on as a result of our communications with each other. Science, in general, and quantum mechanics, in particular, impose further constraints on my probabilistic expectations. They help each of us place better bets on our subsequent experience, based on our earlier experience.

In other words, physics provides constraints on experience. If that's the way you view physics, then a constraint such as NPRF is very reasonable. That's where the Scientific Reports paper ends, but we go further in our Entropy paper. In that paper, we provide a mathematical model of consciousness whereby all of physics follows from two axioms (empirical principles), one of which is NPRF. And that shows how the mysteries of physics are related to the hard and combination problems of consciousness, and how neutral monism resolves them all. The bottom line: the physics we have is beautifully coherent and comprehensive (although not finished, since we still need quantum gravity of course).

 

[Jimster41]

The whole “average conservation of angular moments only, due to Quantuum fintude (h)” just keeps reminding me of this book “Evolutionary Dynamics” by Nowak.

I just opened it to the chapter (6) that sort of blew my mind because it showed how a stochastic Moran process (conservation and “abundance of individuals given by integers”) will lead through neutral drift to the extinction of all but one type. This just sounded so much like spontaneity symmetry breaking to me - I stopped reading the book.

I am hung up on how evolution, a dynamical view if ever there was, and the ultimate bully idea of dynamical time fits into the adynamical Lagragian description of things in your view?

IOW given your focus on physical constants as “discrete limits” can the resolution of simultaneity in 4D be imagined as an evolutionary process... or more importantly, can that be flipped and can evolution as a dynamical perception be imagined as the partitioning of NPRF spacetime you allude to? It seems to me a handy bridge.

Sorry, I’m still reading your book. It will take awhile. And I don’t want to lose this question. BTW the above is not my idea I got it from Eric Chaisson’s (“The Life Era: Cosmic Selection and Conscious Evolution” Harvard University Press). Fair warning, it’s a wild book, the Chaisson one. The Nowak book is this elegant and slightly horrifyingly clear textbook.

 

[RUTA]

I am hung up on how evolution, a dynamical view if ever there was, and the ultimate bully idea of dynamical time fits into the adynamical Lagragian description of things in your view?

Dynamical explanation in physics is still absolutely legit in our view, it's just not fundamental. In my opinion, anything that can be explained dynamically should be, since our experience is dynamical. I only resort to the more fundamental principle/adynamical/Lagrangian explanation as a last resort, e.g., in dealing with closed timelike curves, origin of the universe, delayed choice, etc. All this is covered in our book, as you'll see. Chapters 7 & 8 cover the reconciliation of our dynamical experience of time with adynamical or block universe physics. You can also read our Entropy paper. At 35 pages it's long, but still shorter than Chapters 7 & 8