No need for dark matter, dark energy, MONDS, ect, nothing exotic?

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Discussion Overview

The discussion revolves around alternative theories to dark matter and dark energy, particularly focusing on a paper that proposes a model using lattice calculations and non-commutative approximations to describe gravitational interactions. Participants explore the implications of this model in comparison to established theories like MOND and dark matter, examining its qualitative and quantitative aspects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants highlight the interesting insights from a paper using lattice calculations to describe gravity, suggesting it may provide a simpler explanation than existing dark matter theories.
  • Others argue that the reliance on gravitons and the parameters associated with them is problematic, suggesting that the model may lack empirical verification compared to established theories.
  • A participant notes that the paper's approach attempts to remove additional assumptions made by dark matter and MOND, raising questions about the validity of these established theories.
  • Concerns are raised about the paper's claims regarding the energy density of the universe and how it accounts for dark matter, particularly in relation to observations like the bullet cluster.
  • Some participants express skepticism about the model's ability to explain a wide range of phenomena attributed to dark matter, suggesting that it may not rigorously address all relevant observations.
  • There are discussions about the implications of non-abelian effects in gravitational models and how they relate to observed structures in the universe.

Areas of Agreement / Disagreement

Participants exhibit a mix of agreement and disagreement. While some find the proposed model intriguing and potentially simpler, others express skepticism about its empirical support and ability to account for established observations. The discussion remains unresolved regarding the model's validity compared to traditional dark matter theories.

Contextual Notes

Limitations include the paper's reliance on specific approximations and the lack of detailed explanations for how it addresses key observations like the bullet cluster and WMAP results. Participants note that the model may not fully encompass the complexities of existing dark matter theories.

  • #31
From what I understand, it is not unlike the case of QCD where the non-abelian force (strong interaction) collapses into flux tubes, resulting into confinement. As a result this binding energy is indeed stored inside the system.

As far as the gas is concerned, if the mass distribution is the gas is homogeneous, then the symmetry of the system will be such that the flux lines will all compensate each other and result in no non-abelian net effect.
 
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  • #32
robva said:
From what I understand, it is not unlike the case of QCD where the non-abelian force (strong interaction) collapses into flux tubes, resulting into confinement. As a result this binding energy is indeed stored inside the system.

As far as the gas is concerned, if the mass distribution is the gas is homogeneous, then the symmetry of the system will be such that the flux lines will all compensate each other and result in no non-abelian net effect.

I should have been more careful in the second paagraph. What I meant is that there will be no non-abelian net effect seen from outside the system. Like QCD, everything will stay confined. In the case of the bullet cluster, you see that the two mass maximum are offset from the two gas density spikes. Gas dominates the visible mass of the cluster so it was seen as a proof of dark matter.

In this approach however, the graviton field self interaction effects (the contact term in G^2 in the paper) will dominate this gas. This is the strength of these effects that are able to deform the space-time and bend the light to make a gravitational lens.

To sum it up, the field self-interaction plays the role of dark matter in other models
 
  • #33
In the context of the weak approximation he made in this paper, the lensing effect can not be directly computed from the lagrangien. He kept only the scalar term which can only couple with the trace of the Fmunu tensor to produce an invariant. Since this trace is zero, this model does not allow photons to couple with gravitons. It is simply necessary for future work to extent this model to rank2 tensor in order to compute lensing directly from graviton interactions. It is very difficult to compute on a lattice but some people are starting to look at it. A simpler approach is simply to use the potential he got and via a semi-classical approach do a estimate of the lensing effects. That should work fine since it is essentially what current lensing models do using the Newtonian gravity potential with extra mass coming in from dark matter.
Alexandre is going to look at that, its on his long list of things to do.
 
  • #34
robva said:
It is very difficult to compute on a lattice but some people are starting to look at it.

So, it wasn't just me who got interested in his work?

BTW, I'd like to know how does the non abelian nature of his model relates to frame dragging.
 

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