Do gravitons interact with gravitons?

[PeterDonis]

The most recent paper that I cited above is precisely above the evolution of the early universe

I'll take a look, this looks more recent than the Deur papers I am familiar with.

 

[ohwilleke]

After rereading Deur's recent article I came across this text passage where I seem to have a misunderstanding:I "understand" that the " increased binding due to GR's SI" could account for dark matter. But how can the weakening of gravity's action (due to SI) account for the observed accelerated expansion of the universe?

If gravity is "just" weakened between the Galaxy clusters it's still attractive so how can this imitate (or replace?) the action of repelling gravity according to the Lambda-CDM model?

What am I missing?

To slightly oversimplify, DM phenomena are attributed to gravitons staying in the system more often than they would in a spherically symmetric system. Since those gravitons never level the system, there are fewer gravitons leaving the system than would leave a spherically symmetric system. So, the bond between the two systems is weaker than one would expect. Not being held together a tightly due to weaker than expected gravitational fields between systems looks the same as being pulled apart by additional diffuse dark energy.

 

[PeterDonis]

To slightly oversimplify, DM phenomena are attributed to gravitons staying in the system more often than they would in a spherically symmetric system. Since those gravitons never level the system, there are fewer gravitons leaving the system than would leave a spherically symmetric system. So, the bond between the two systems is weaker than one would expect. Not being held together a tightly due to weaker than expected gravitational fields between systems looks the same as being pulled apart by additional diffuse dark energy.

This explanation has at least two issues.

First, since Deur has also claimed that his proposed effect (at least, the one that emulates dark matter--see below) can be derived in classical GR, any talk about "gravitons" is both superfluous (we don't need any quantum gravity effects) and potentially misleading (since we have no actual evidence for any quantum gravity effects). In classical GR terms, Deur's proposed effect is due to nonlinearities in the Einstein Field Equation causing additional effects in a lens-shaped or disk-shaped system that they do not cause in a spherically symmetric system (because the additional symmetry basically cancels them out). I think that is a much better heuristic picture than any picture involving "gravitons".

Second, dark energy is not the same as dark matter. The "nonlinear effects" part, as I described it above, is a proposed alternate explanation for effects that are attributed in our current standard cosmology to dark matter. But the "fewer gravitons leaving the system" part is a proposed alternate explanation for effects that are attributed in our current standard cosmology to dark energy, not dark matter. The latter alternate explanation, AFAIK, is on much shakier ground since it does not appear in the classical version of Deur's proposal (i.e., it is not an effect that appears in classical GR; it is not just due to nonlinearities in the EFE, but something else). I think it would be much better not to conflate the two.

 

[ohwilleke]

This explanation has at least two issues.

First, since Deur has also claimed that his proposed effect (at least, the one that emulates dark matter--see below) can be derived in classical GR, any talk about "gravitons" is both superfluous (we don't need any quantum gravity effects) and potentially misleading (since we have no actual evidence for any quantum gravity effects). In classical GR terms, Deur's proposed effect is due to nonlinearities in the Einstein Field Equation causing additional effects in a lens-shaped or disk-shaped system that they do not cause in a spherically symmetric system (because the additional symmetry basically cancels them out). I think that is a much better heuristic picture than any picture involving "gravitons".

I don't disagree that the effect can be derived in classical GR which lacks gravitons. But, as a quick and dirty way to get across the concept, I think it is much more natural to understand in a graviton context, which is why I used this heuristic with the caveat that I am oversimplifying.

Ultimately, the physics of massless spin-2 gravitons are identical to GR except for quantum effects not implicated in this context, and the static equilibrium approximation used by Deur is, in this context, not sacrificing any important effects relevant to dark matter or dark energy phenomena.

Second, dark energy is not the same as dark matter. The "nonlinear effects" part, as I described it above, is a proposed alternate explanation for effects that are attributed in our current standard cosmology to dark matter. But the "fewer gravitons leaving the system" part is a proposed alternate explanation for effects that are attributed in our current standard cosmology to dark energy, not dark matter. The latter alternate explanation, AFAIK, is on much shakier ground since it does not appear in the classical version of Deur's proposal (i.e., it is not an effect that appears in classical GR; it is not just due to nonlinearities in the EFE, but something else). I think it would be much better not to conflate the two.

The non-linearities in classical GR have the same effect, although much less transparently, which is why I didn't use that heuristic example.

From the perspective of classical GR, the strengthening of the fields within the system due to its asymmetries and the non-linearities of GR that gives rise to dark matter phenomena simultaneously weakens the gravitational fields by a like amount outside that system.

The July 9, 2021 paper explains:

Besides their fundamentally different interpretation of the nature of gravitation, GR and Newton's gravity also crucially differ in that GR is non-linear. This can be traced to field SI once space-time curvature is interpreted in terms of fields. GR can be formalized by the Einstein-Hilbert Lagrangian density,(1)LGR=(det⁡gμν)12gμνRμν/(16πG),with gμν the metric, Rμν the Ricci tensor and G the gravitational constant. The https://www.sciencedirect.com/topics/physics-and-astronomy/gravitational-fields φμν originating from a unit mass source is the variation of gμν with respect to a constant metric ημν: φμν=(gμν−ημν)/M, where M is the system mass. Expanding LGR in term of φμν yields, in the pure field case [12]:(2)LGR=[∂φ∂φ]+16πMG[φ∂φ∂φ]+16πMG[φ2∂φ∂φ]+⋯,where [φn∂φ∂φ] represents a sum of Lorentz-invariant terms of the form φn∂φ∂φ. Newton's gravity is given by LGR truncated to n=0, with [∂φ∂φ]=∂μφ00∂μφ00, ημν the flat metric and ∂0φ00=0. The n>0 terms induce field SI.

Another fundamental force displaying SI is the Strong Interaction. It is formalized by quantum chromodynamics (QCD) whose pure field Lagrangian is:(3)LQCD=[∂ϕ∂ϕ]+παs[ϕ2∂ϕ]+παs[ϕ4].Here, ϕμ is the gluonic field and αs the QCD coupling [13]. Again, a bracket [] indicates a sum of Lorentz-invariant terms, and, in the QCD case, contractions of the color indices. The similarity between LGR and LQCD makes the latter useful as a guide for GR in its strong regime, since QCD in that regime is well-studied. Like GR, the terms beyond [∂ϕ∂ϕ] induce the field SI. They are interpreted in QCD (GR) as arising from the color charges (energy-momentum) carried by gluonic (gravitational) fields, which permit field self-coupling. For QCD the coupling –driven by αs– is large, making the consequences of field SI prominent. In GR, large GM/L values (L is a characteristic length of the system) enable SI. QCD's SI strongly increases the interaction between color charges and causes quark confinement. Likewise, GR's SI increases the gravitational system's binding compared to Newton's theory. If the latter is used to analyse galaxy or cluster dynamics, as is commonly done, ignoring the SI-induced intensification of the force then creates a missing (dark) mass problem. The results of Refs. [6], [7], [8] indicate that SI can sufficiently strengthen the gravitational binding such that no dark matter is required to explain galactic rotation curves or the internal dynamics of galaxy clusters. In QCD, the SI strengthens so much the binding of color sources that they remain confined, i.e. the Strong Interaction is essentially1 suppressed outside of the system, e.g. outside a nucleon. This can be globally understood from energy conservation: the confined field increases the system's binding energy, but the field concentration causes its depletion outside of the system. Likewise2 in gravitational systems, the increased binding due to GR's SI weakens gravity's action at large scale. If GR's SI is ignored, this weakening can then be misinterpreted as a large-scale repulsion, viz dark energy. The effect is time-dependent: as massive structures form, some gravitational fields become trapped in them, weakening their manifestation at larger scale. This implies a direct connection between dark energy and dark matter, particularly between dark energy and the onset of structure formation.

 

[PeterDonis]

From the perspective of classical GR, the strengthening of the fields within the system due to its asymmetries and the non-linearities of GR that gives rise to dark matter phenomena simultaneously weakens the gravitational fields by a like amount outside that system.

This is not correct, at least not if "weakens" is taken to mean "causes an effect that looks like accelerating expansion of the universe". In classical GR, what you are calling "strengthening of fields within the system" makes the system more tightly bound and thus decreases its externally measured mass. However, this decrease in externally measured mass, in classical GR, only has the effect of decreasing the deceleration of expansion due to that massive body. It does not cause any effect that looks like accelerating expansion. That requires a different form for the stress-energy tensor, a form which cannot be produced in classical GR simply by making a system more tightly bound.

 

[ohwilleke]

This is not correct, at least not if "weakens" is taken to mean "causes an effect that looks like accelerating expansion of the universe". In classical GR, what you are calling "strengthening of fields within the system" makes the system more tightly bound and thus decreases its externally measured mass. However, this decrease in externally measured mass, in classical GR, only has the effect of decreasing the deceleration of expansion due to that massive body. It does not cause any effect that looks like accelerating expansion. That requires a different form for the stress-energy tensor, a form which cannot be produced in classical GR simply by making a system more tightly bound.

To be clear, you don't disagree with the notion of a "decrease in externally measured mass, in classical GR," which is the effect that he is referencing.

Keep in mind that this decrease is present and growing (on average) with respect to every single galaxy and galaxy cluster and other gravitationally bound system. Certainly, a weaker gravitational bond between galaxies and galaxy clusters across the board looks the same as Newtonian gravity plus a repulsive force.

It is not at all obvious why "the deceleration of expansion due to that massive body. It does not cause any effect that looks like accelerating expansion". If clumps of matter have an initial expansion rate at one level of gravitational bonding which is holding back the momentum driving the initial expansion, and the gravitational bond between those clumps of matter weakens over time, why shouldn't it appear to accelerate relative to the rate seen before, with the same momentum but less of a gravitational force between clumps of matter holding it back.

 

[PeterDonis]

this decrease is present

Only in the sense that the actual mass is less than the mass currently included in our models.

and growing

Not as I understand it. A galaxy with a given number of stars will have a given "decrease" (actual mass compared to mass in our current models) that does not change.

a weaker gravitational bond between galaxies and galaxy clusters

Is not the actual classical GR effect. The actual classical GR effect is a slightly smaller mass for each galaxy and galaxy cluster than the one that is currently in our models. That is not the same as a "weaker gravitational bond". The "strength of gravity" is not changed. See below.

looks the same as Newtonian gravity plus a repulsive force.

No, it doesn't. It looks like a slightly smaller "matter" contribution to the overall evolution of the FRW spacetime scale factor than the one that is in our current models. There is no "repulsive force". The effect of the matter contribution on the evolution of the scale factor (namely, deceleration) is not changed.

It is not at all obvious...

Maybe not to you, but that does not mean you should resort to hand-waving to try to justify your alternative claim. You should stop and think very carefully about what the "decrease" you refer to actually means. See my comments above.

 

[ohwilleke]

Not as I understand it. A galaxy with a given number of stars will have a given "decrease" (actual mass compared to mass in our current models) that does not change.

Galaxies merge and collect into galaxy clusters over time. The number of stars in the system grows. As the systems evolve to have stronger dark matter phenomena over time, the magnitude of the dark energy phenomena increases as well.

No, it doesn't. It looks like a slightly smaller "matter" contribution to the overall evolution of the FRW spacetime scale factor than the one that is in our current models. There is no "repulsive force".

I'm not saying that there is a repulsive force, I'm saying that if you have one force between two objects that weakens, that is indistinguishable observationally from a stronger force that is expected matched by a repulsive force.

Think of it this way. Our current observations are incorporated into a model to estimate the magnitude of lambda, the cosmological constant. If the apparent masses of galaxies at the same distance from each other is smaller than previously modeled, and if that apparent mass decreases over time due to galaxy mergers, galaxy cluster formation, etc., the estimated value of lambda should be smaller than it is currently estimated as being today. Also, this particular physical constant is one of the less precisely known in core theory. Maybe it goes to zero, much it is just materially smaller and we still need "dark energy" albeit, much less of it. Somebody has to quantify the exact magnitude of that effect which Deur tries to do in his latest paper. But, it is hard to see how it could not be a significant adjustment. The amount of energy required to make the expansion accelerate at an observed rate has to be smaller if the amount of apparent mass that needs to be moved is smaller.

 

[PeterDonis]

Galaxies merge and collect into galaxy clusters over time. The number of stars in the system grows. As the systems evolve to have stronger dark matter phenomena over time, the magnitude of the dark energy phenomena increases as well.

Ah, I see.

I'm not saying that there is a repulsive force, I'm saying that if you have one force between two objects that weakens, that is indistinguishable observationally from a stronger force that is expected matched by a repulsive force.

This is not correct, because here "repulsive force" would have to mean "something that causes the appearance of accelerated expansion", and that's not what a change to the matter term in the evolution equation for the scale factor does. All it does is reduce the deceleration. It does not change deceleration to acceleration. Those are qualitatively different appearances and one cannot reproduce the other.

 

[PeterDonis]

The amount of energy required to make the expansion accelerate at an observed rate has to be smaller if the amount of apparent mass that needs to be moved is smaller.

This is not correct. Accelerated expansion is not a "force" that has to be bigger to move more mass. It is a geometric property of spacetime that affects geodesic deviation, independently of the masses of objects that might or might not be following such geodesics.

 

[timmdeeg]

All it does is reduce the deceleration. It does not change deceleration to acceleration. Those are qualitatively different appearances and one cannot reproduce the other.

Thanks, much better expressed than what I tried to say in #35.

I really wonder if/why Deur has overlooked this issue.

 

[PeterDonis]

I really wonder if/why Deur has overlooked this issue.

I don't know that Deur has. I only know that @ohwilleke is. I don't know that Deur makes all of the same claims in his papers that @ohwilleke is making in this thread.

 

[timmdeeg]

I don't know that Deur has. I only know that @ohwilleke is. I don't know that Deur makes all of the same claims in his papers that @ohwilleke is making in this thread.

It seems that Deur makes this claim.

https://www.sciencedirect.com/science/article/pii/S0370269321004500?via=ihub

Ref. [10] points out that the SI-enhanced binding inside massive systems is balanced by reduced gravitational field outside these systems, and shows how this reduction can explain without dark energy the large-z supernova observations [18].

As I understand it these observations are uncontroversially associated with the accelerated expansion of the universe. Deur doesn't mention this term though.

 

[PeterDonis]

It seems that Deur makes this claim.

Yes, I see. Ref. 10 is this paper:

https://arxiv.org/abs/1709.02481

I'll take a look at it.

 

[PeterDonis]

Deur doesn't mention this term though.

He does in the first sentence of the paper I linked to in post #49.

 

[timmdeeg]

So he says implicitly that the "reduced gravitational field outside these systems" can explain the accelerated expansion of the universe.

 

[PeterDonis]

So he says implicitly that the "reduced gravitational field outside these systems" can explain the accelerated expansion of the universe.

That's how it looks to me, yes; but I'm not entirely sure whether, in his model, the term "accelerated expansion" is actually a correct description. He might be implicitly saying that what we currently think of as "accelerated expansion" is actually not accelerated, but it appears to us to be because we are modeling the evolution of the scale factor incorrectly; in Deur's model, the evolution of the scale factor might be changed so the expansion actually never is accelerated, we are just interpreting our observations incorrectly.

 

[ohwilleke]

Ah, I see.This is not correct, because here "repulsive force" would have to mean "something that causes the appearance of accelerated expansion", and that's not what a change to the matter term in the evolution equation for the scale factor does. All it does is reduce the deceleration. It does not change deceleration to acceleration. Those are qualitatively different appearances and one cannot reproduce the other.

"Repulsive force" would mean "something that causes an increase in the magnitude to the relative velocity of two masses that tends to move them farther apart from each other. Whether this means "accelerated expansion" or not would depend on exactly how one defined "expansion". Geometric terminology and force terminology are not inherently inconsistent.

 

[PeterDonis]

"Repulsive force" would mean "something that causes an increase in the magnitude to the relative velocity of two masses that tends to move them farther apart from each other.

That's the same thing as "accelerating expansion"; "accelerating" means "increasing magnitude of velocity".

As I noted in post #52, however, it's not clear to me whether Deur is actually claiming that. It seems to me that he might be saying that our universe's expansion actually is not accelerated--that the relative velocity between comoving observers is not actually increasing. He might be saying that it only appears to be increasing because our current standard model, the Lambda CDM model, is using an incorrect method of deriving the scale factor as a function of time, and when Deur's method is used instead, we find a different function of time for the scale factor, one which is always decelerating.

 

[timmdeeg]

It seems to me that he might be saying that our universe's expansion actually is not accelerated--that the relative velocity between comoving observers is not actually increasing.

I think this view fits to Deur's recent paper:

https://arxiv.org/pdf/1709.02481.pdf

This increased binding must, by energy conservation, weaken the action of gravity at larger scale. This can then be mistaken for a repulsion, i.e. dark energy. Specifically, the Friedmann equation for an isotropic and homogeneous Universe is (for a matter-dominated flat Universe) H2 = 8πGρ/3, with H the Hubble parameter and ρ the density. As massive structures coalesce, gravity is effectively suppressed at scales larger that these structures. This weakening with time results in a larger than expected value of H at early times, as seen by the observations suggesting the existence of dark energy.

 

[PeterDonis]

I think this view fits to Deur's recent paper

Yes, that's one of the statements that makes me think that. I'm still working through the actual math.

 

[timmdeeg]

I'm still working through the actual math.

Great.

Perhaps it's possible to see if in principle Deur's model predicts observations which could verify/falsify his claim.

 

[ohwilleke]

Great.

Perhaps it's possible to see if in principle Deur's model predicts observations which could verify/falsify his claim.

There are many such observations at the galaxy scale (e.g. the relationship between the extent that an elliptical galaxy is spherical and its apparent dark matter fraction, and a relationship in spiral galaxies related to disk thickness), but the dark energy/cosmology scale work is less worked out. The main prediction seems to be structure formation at an earlier time than LambdaCDM which does indeed have some support observationally.

 

[timmdeeg]

The main prediction seems to be structure formation at an earlier time than LambdaCDM which does indeed have some support observationally.

Yes, but besides that I had the Ia Supernovae data and the CMB Power Spectrum in my mind. I wonder if the depletion function which is based on anisotropy factors shouldn't in principle produce the SN data. As Deur claims that these data are "mistaken for repulsion" then I would expect that e.g. the depletion function should yield an alternative (quantitative) explanation.

 

[ohwilleke]

Yes, but besides that I had the Ia Supernovae data and the CMB Power Spectrum in my mind. I wonder if the depletion function which is based on anisotropy factors shouldn't in principle produce the SN data. As Deur claims that these data are "mistaken for repulsion" then I would expect that e.g. the depletion function should yield an alternative (quantitative) explanation.

I'm pretty much 100% certain that the answer is that Deur hasn't had the time and resources to explore a lot of those questions yet. I've corresponded with him in the past and he's basically said as much. The gravity work, while Nobel Prize material and Stephen Hawking class fame generating if it works out, doesn't have grant funding and is basically side hustle made possible by the time that his day job allows for discretionary research. So, he has to spend most of his time working on far less consequential, but better funded, activities. If I won the lottery, the first thing I'd do would be to set up grants or an endowment to support this line of research.

 

[rcarbajal68]

I am working on something similar to that of Dr. Alexandre Deur. I am also using the self-interaction of gravity. But I'm doing the self-interaction in reverse of how he's using it. And I am getting very good results in fitting to the rotation curves of the galaxies.
Sincerely.
Dr. Rigoberto Carbajal Valdez

 

[ohwilleke]

I am working on something similar to that of Dr. Alexandre Deur. I am also using the self-interaction of gravity. But I'm doing the self-interaction in reverse of how he's using it. And I am getting very good results in fitting to the rotation curves of the galaxies.
Sincerely.
Dr. Rigoberto Carbajal Valdez
This is my email.
rcarbajal68@gmail.com

Have you published anything (even a pre-print) that someone could see?

 

[PeterDonis]

I am working on something similar to that of Dr. Alexandre Deur. I am also using the self-interaction of gravity. But I'm doing the self-interaction in reverse of how he's using it. And I am getting very good results in fitting to the rotation curves of the galaxies.

As @ohwilleke has pointed out, we need a reference (a published peer-reviewed paper) in order to have a basis for discussion.

 

[DanielJoseph]

I wonder if https://www-livescience-com.cdn.ampproject.org/v/s/www.livescience.com/amp/gravitational-wave-detector-strange-bumps.html?amp_js_v=a6&amp_gsa=1&usqp=mq331AQIKAGwASCAAgM%3D#aoh=16324719503472&csi=0&referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.livescience.com%2Fgravitational-wave-detector-strange-bumps.html is relevant at all

 

[Maarten Havinga]

If GR with self-interaction reproduces all verified MOND predictions (including the EFE) while retaining the beautiful symmetries and general framework of gauge fields and the standard model of particles:
THAT'S AWESOME!

 

[rcarbajal68]

Have you published anything (even a pre-print) that someone could see?

Good morning. I am working on that, in collaboration with another Doctor, as soon as I have something I will share it through this forum. Thank you.

 

[ohwilleke]

I wonder if https://www-livescience-com.cdn.ampproject.org/v/s/www.livescience.com/amp/gravitational-wave-detector-strange-bumps.html?amp_js_v=a6&_gsa=1&usqp=mq331AQIKAGwASCAAgM%3D#aoh=16324719503472&csi=0&referrer=https%3A%2F%2Fwww.google.com&_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.livescience.com%2Fgravitational-wave-detector-strange-bumps.html is relevant at all

Not really.

 

[ohwilleke]

If GR with self-interaction reproduces all verified MOND predictions (including the EFE) while retaining the beautiful symmetries and general framework of gauge fields and the standard model of particles:
THAT'S AWESOME!

FWIW, this particular effort does not resolve deep inconsistencies between classical GR and the quantum mechanical foundation of the Standard Model, and indeed, can be formulated in a purely classical sense, although the motivation for the work was rooted in quantum gravity concepts. But assuming it is correct (which is hard to verify as few other in the field have examined it closely) it is indeed awesome.

 

[ohwilleke]

The latest paper in the series of papers cited earlier is the following:

Figure 2 from the paper

Field self-interactions are at the origin of the non-linearities inherent to General Relativity. We study their effects on the Cosmic Microwave Background anisotropies. We find that they can reduce or alleviate the need for dark matter and dark energy in the description of the Cosmic Microwave Background power spectrum.

A. Deur, "Effect of the field self-interaction of General Relativity on the Cosmic Microwave Background Anisotropies"
arXiv:2203.02350 (March 4, 2022).

The introduction in the body text explains:

The power spectrum of the Cosmic Microwave Background (CMB) anisotropies is a leading evidence for the existence of the dark components of the universe. This owes to the severely constraining precision of the observational data and to the concordance within the dark energy-cold dark matter model (Λ-CDM, the standard model of cosmology) of the energy and matter densities obtained from the CMB with those derived from other observations, e.g. supernovae at large redshift z. Despite the success of Λ-CDM, the absence of direct or indirect detection of dark matter particles is worrisome since searches have nearly exhausted the parameter space where candidates could reside. In addition, the straightforward extensions of particle physics’ Standard Model, e.g. minimal SUSY, that provided promising dark matter candidates are essentially ruled out.

Λ-CDM also displays tensions with cosmological observations, e.g. it overestimates the number of dwarf galaxies and globular clusters or has no easy explanation for the tight correlations found between galactic dynamical quantities and the supposedly sub-dominant baryonic matter, e.g. the Tully-Fisher or McGaugh et al. relations.

These worries are remotivating the exploration of alternatives to dark matter and possibly dark energy. To be as compelling as Λ-CDM, such alternatives must explain the observations suggestive of dark matter/energy consistently and economically (viz without introducing many parameters and fields). Among such observations, the CMB power spectrum is arguably the most prominent.

Here we study whether the self-interaction (SI) of gravitational fields, a defining property of General Relativity (GR), may allow us to describe the CMB power spectrum without introducing dark components, or modifying the known laws of nature. GR’s SI already explains other key observations involving dark matter/energy: flat galactic rotation curves, large-z supernova luminosities, large structure formation, and internal dynamics of galaxy clusters, including the Bullet Cluster. It also explains the Tully-Fisher and McGaugh et al. relations. First, we recall the origin of GR’s SI and discuss when it becomes important as well as its overall effects.

 

[Maarten Havinga]

The latest paper in the series of papers cited earlier is the following:

View attachment 298460
Figure 2 from the paper

Although I am now a great fan of Deur's theory, this last paper is not so much to my liking. It would have been great if Deur had brought it like "okay, so the CMB is explained this way by lambda CDM and if you really want to reproduce the CMB that way, in principle it can also be done without dark matter".

My issues are:

1. This CMB graph from the Big Bang is a postdiction, not a prediction. And with 6 free variables.
2. The CMB in this interpretation ought to be dampened by cosmic dust, which is not reckoned with in Lambda-CDM or Deur's paper. See Vavrycuk's paper and video.
3. The Big Bang explanation assumes inflation, which is an unfalsifiable idea for our current experimentation range.
4. I'm a believer in the bible, and there's good reason to reject the Big Bang as description of how God created the universe. An alternative explanation is given by for instance Russell Humphreys' book Starlight and Time.

In general, my great liking of Deur's theory is slightly dampened by the fact he attaches such importance to accomodating a Big Bang scenario alike to how the lambda-CDM community preaches it. For my taste this paper handles a detail not worth a paper so early in Deur's on the whole extremely prudent approach.

Nevertheless I'm a big fan of his work! :-)