An expanding universe without dark matter and dark energy!

Discussion in 'Astronomy, Exobiology, & Cosmology' started by gabana, Feb 8, 2013.

  1. gabana Registered Member

    Messages:
    13
    Abstract:

    Assuming that observers located inside the Universe measure a time flow which is different from the time appearing in the Friedmann-Lemaitre equation, and determining this time flow such that the Universe always appears flat to these observers, we derive a simple cosmological model which allows to explain the velocity dispersions of galaxies in galaxy clusters without introducing dark matter. It also solves the horizon problem without recourse to inflation. Moreover, it explains the present acceleration of the expansion without any resort to dark energy and provides a good fit to the observations of distant supernovae. Depending on the present value of the matter-energy density, we calculate an age of the Universe between 15.4 and 16.5 billion years, significantly larger than the 13.7 billion years of the standard ΛCDM model. Our model has a slower expansion rate in the early epochs, thus leaving more time for the formation of structures such as stars and galaxies.

    http://arxiv.org/pdf/1212.1110v2.pdf
     
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  3. Scott Myers Newbie Registered Senior Member

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    After a quick read, I don't really see that this (extra) mathematic variable is much better than Dark Matter, or Dark Energy. This is equal to “Tired Light” ideas that can be worked out by changing a parameter over time, or distance, just because it can be solved for, or thought of. This might be called ‘Tired Time’ or something like that.

    Time is variant, but the only reasons observed for the phenomenon are Velocity Time Dilation in SR, which we know to be frame dependent, and Gravity Time Dilation in GR, which is not frame dependent.

    From the Indroduction:
    “However, in order to provide an accurate description of large-scale and long-term phenomena,
    a number of artifacts had to be added to the theory. The motion of stars in the
    outskirts of spiral galaxies and the velocity dispersions of galaxies in clusters required the
    addition of dark matter. The acceleration of the expansion of the Universe called for the
    introduction of dark energy. The so-called flatness and horizon problems were solved by
    postulating an early phase of dramatic expansion named inflation.”


    The answer that is proposed is convenient, but can neither be confirmed or denied, because it claims that time simply changes over a “large-scale and long-term” context. I see no reason this does any better at answering, or resolving, the issues it has claimed to address, nor is there any proposed reason WHY time would do this other than because it was so long ago?

    Not picking on anyone, but I believe this should be in the Alternate Theories forum perhaps. Interesting, but I just don’t see it. Thanks for posting it though.
     
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  5. AlphaNumeric Fully ionized Registered Senior Member

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    This is a reply to this post in another thread where the same paper was put forth by the same poster. I'm replying here to keep it all in one thread and to reduce disturbance to the other thread.

    Are you just searching the internet for papers which say things along the lines of "... and therefore we do not need to include dark matter/energy into our model to explain the universe's structure."? Do you read the details of the papers you're linking to, to see what they are doing and how they do it? Or are you just looking at the title and abstract before wheeling it out in any discussion on dark matter or dark energy?

    The first paper you linked to fails to justify its assertions. In places it says "It can be shown that our model...." and then they don't show the workings. If it is their model it is up to them to demonstrate the validity of their claims. As I said, the approach used is extremely rudimentary, isn't shown to be consistent within relativity and reaches results which contradict experiments. I've already given an example, the \(\frac{\delta \tau_{2}}{\delta \tau_{1}}\) ratio in (10). They obtain it by assuming the applicability of a Lorentz transform between frames when comparing say us with the material at the edge of galaxies. For curved space-time you cannot apply Lorentz transforms like that because Lorentz transforms work on flat space, not general curved space. To demonstrate and apply Lorentz symmetries within special relativity you have to first go into normal coordinates and consider Lorentz transforms on these. I can be more explicit if needed but it is fairly heavy on the mathematics.

    Even assuming you can apply Lorentz transforms blindly the velocity discrepancies seen in galaxy rotation rates are much much bigger than anything such a scaling can account for. It is strange the authors do not address that but instead test their idea by looking at galaxy-galaxy relative velocity behaviours. But, as they state, now we're talking about distances of billions of light years over time scales of billions of years. Since they are using the FRW metric as their initial starting point and explicitly restructure their notion of time by using a curved metric then the blind application of Lorentz transforms in that manner, ie not taking into account also how expansion impacts relative velocities and times measured between galaxies, then it is even more dubious.

    An additional problem is that they are claiming there is some time dilation effect going on which previously wasn't observed/realised and this explains all the things related to dark matter. If the edge of our galaxy seems to move as it does due to time dilation effects and other galaxies move relative to one another due to a time dilation effect why do we not observe the impact of this on phenomena internal to galaxies? For example, phenomena like supernova have very specific behaviour relating their brightness, power spectrum, illumination time profile and mass. Likewise for Cepheid stars, whose oscillation in size, power spectrum and brightness is well understood. Both of those phenomena are used as 'standard candles' to allow us to work out distances to various places in the universe. In fact it was supernovae which led us to realise the universe's expansion is accelerating.

    Why do we not see the tell tale signs of time dilation on these phenomena in other galaxies and here in the Milky Way? Once astrophysicists account for the various FRW metric modifications to observations (ie put observations into the standard model of cosmology, none of this 'universal time' stuff) they get consistent data. They also include notions of dark energy. The authors need to address such things. They also need to address other dark matter related phenomena, namely the Bullet Cluster and the micro-variations in the CMB caused by matter clumping before recombination occurred. Until they have addressed all of those points and also given more details of their workings it is unjustified of you to go around saying it's been explained away.

    The second paper you linked to (ie the one in this thread) doesn't do away with dark matter, instead it folds the notion of dark energy into dark matter by postulating a different model for dark matter. Initially there are massless particles and then later on they are placed by massive ones. This is done by writing down a simple scalar field model and then claiming the scalar field decomposes into a particle scalar field and the length scale parameter from the FRW metric. Using additional scalar fields to model the dynamics of space-time or to modify its dynamics is not new, nor is modifying the apparent rest masses of particle types through coupling to space-time. Getting space-time to then do what you want is something seen a lot in things such as string theory. The space-time length scale is coupled to an 'inflaton field' obtained by compactification whose rolling down a potential leads to inflation (hence the name). Additional scalar fields then arise from other moduli in the space and their vacuum expectation values give particles mass in a Higgs-esque manner.

    The paper is putting forth another way of modelling space-time expansion using particle fields coupling to the metric, as many papers before it have done. The ideas are interesting and (unlike the previous paper) explained in formal detail but it is only attempting to address one question in regards to dark matter/energy, can you do away with one of them and still explain a specific observed phenomenon. No attempt is made to consider galaxy rotation curves, the Bullet Cluster or variations in the CMB. This is because the authors are exploring matter driven space-time dynamics, they are not attempting to reinvent cosmology without dark matter or dark energy (not yet anyway). So the same applies to this paper as the previous, you cannot seriously say "This has shown dark matter and energy can be thrown in the bin" until it is shown that this method also explains the other dark matter/energy related phenomena correctly.

    This is why I asked you if you even read or understood the papers. You can't just find a paper which says "Here is some new cosmological model which does away with dark matter" and then another which says "This cosmological model does away with dark energy" and declare "Both dark energy and dark matter can be thrown away!". You can only say that if each paper justifies its claims and they are compatible with one another. The first paper modifies how time behaves over cosmological distances, which is something the second paper doesn't include. How do you know that when you use the first paper's idea in the second paper's model that they are compatible? You don't.

    Neither paper individually is enough to declare dark (stuff) can be thrown in the bin and it is not clear they are even compatible.
     
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  7. gabana Registered Member

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    Wow! Thanks, for the detailed reply!

    Sorry, but I have must to answer with the next paper again, for the detailed calculations.

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    The motion of stars in galaxies and the gravitational time dilatation

    http://arxiv.org/pdf/1005.2826.pdf

    This description will explain the galaxy rotation curves without dark matter too.
     
    Last edited: Feb 10, 2013
  8. brucep Valued Senior Member

    Messages:
    4,098
    I mostly read the final remarks and the Introduction. Maybe that's interesting, but for me, it's a novelty that doesn't have much chance to model our universe. Eliminating the need for dark energy doesn't make much sense since we already know what It is, cosmological constant, and how much exists per WMAP. The novelty is 'we can create a universe where the extra particles are gradually created from the gravitational field'. A different kind of 'inflation' without the need for 'dark energy'. How about sticking with 'all the matter in the universe was created during the last throws of inflation' and some of it is 'dark matter'.
     
  9. Scott Myers Newbie Registered Senior Member

    Messages:
    290
    Wow, thanks for posting this one Gabana. This idea, I like, and am (was already) in the process of filling in some of the blanks left in this paper, though I agree with their answer, that it is possible. I threw this up in Alternative Theories about a week ago. http://www.sciforums.com/showthread...e-Galaxy-Rotation-Problem-without-Dark-Matter

    I will repost the link there, since the exact idea was opened up there, I was looking for this being applied to the question, but could find no evidence thus far.
     
  10. Scott Myers Newbie Registered Senior Member

    Messages:
    290
    Because, quite simply, if it can be found that all of the mass can be accounted for in usual observeable scientific way, we'll all be the better for it. One problem at a time.
     

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