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GammaRayBursts as standard candles to judge dark energy

  1. Jan 14, 2004 #1

    marcus

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    this was a new post today

    http://arxiv.org/astro-ph/0401244

    it is still just a germinal idea
    remember in 1998 type IA supernovae were used as a standard candle
    and the luminosity-distances of them at various redshifts pointed to the existence of dark energy or cosmological constant Lambda (add your own name for it here).

    well so far not all that many GRB have been observed (around 30 have had their redshifts measured)

    but they cluster around the same inferred energy on the order of several 1050 erg, these authors say

    that is 1043 joule
    or, in planck terms, on the order of 1034 natural units of energy, that seems like a lot of energy to be concentrated in a brief flash of gamma rays---I wonder if I understand them right.

    In any case, these people suggest that once there is a large dataset and 300 GRB or 1000 GRB have been observed then, since they all have about the same energy you could use them as standard candles and compare the numbers of them at various distances

    in a universe with dark energy there would be fewer close by and more further away, compared to a universe with only dark (and ordinary) matter.

    It is a catchy idea. The thing with Type IA supernovae was that because of what causes them they all have just about the same energy. So they work as standard candles for judging distances. So could the same thing be done, but over larger distances, using GRB as standard candles. I cant tell if it is a sensible proposal, but I like the sound of it.
     
    Last edited: Jan 14, 2004
  2. jcsd
  3. Jan 14, 2004 #2
    In Physic World, about a month ago, another article actually support on the other side of theory. based on simliar formula between luminosity, Mass and temperature and Xray data, it suggested dark energy and dark mass do not exist. FYI.
     
  4. Jan 14, 2004 #3

    marcus

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    Many thanks Sammywu!
    If you can give me the name of the author, or a link to the online
    Physics World table of contents, I may be able to follow up on it.

    I do not see how dark matter could fail to exist. Its gravity is required to keep the clusters of galaxies from flying apart.
    Individual galaxies are typically moving so fast in random directions that the clusters would
    not hold together if they did not have lots of extra mass in them.

    So this article you saw must propose strange and amazing things
    which would be curious to know about---to get rid of dark matter.


    It is easier to think of how there might be no dark energy, but then one would normally fill in with dark matter. If one has gotten rid of BOTH dark matter and dark energy then how can one explain the near flatness of the universe!
     
  5. Jan 14, 2004 #4
    Marcus, Try physicsweb.org/toc/world/. I know no much about this topic. It's just that the dark matter and dark energy always intrigue me. There is another document saying speculation of dark matter is certain antimaterials called neutralino populated in the intergalaxy space. Somehow, it probably won't react with light. You shall be able to find that in the same web site.
     
  6. Jan 15, 2004 #5

    marcus

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    Sammywu, I would appreciate some help finding the newsitem or article
    I went searching TOC of Physics World from September thru December 2003 but did not find a clear hit.

    I did find this, in November:

    http://physicsweb.org/article/world/16/11/3

    Is this the item you referred to? I was not sure.

    thanks in advance,

    Marcus
     
  7. Jan 16, 2004 #6
    Marcus, Did you find out the one disputing about drak matter/energy? Can you find the one summerizing the consonant model?
     
  8. Jan 16, 2004 #7

    marcus

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    Hi Sammywu, thanks for getting back to me. I have forgotten exactly
    what we were discussing
    You told me about some things in Physics World
    I tried to get them but I do not have a subscription, so
    sometimes I can only see a brief summary of the article.
    Dark energy (or as Sean Carroll calls it: the "smooth tension" throughout space) is pretty well established and I couldnt find
    a alternative explanation of the SNe data that satisfied me, in Physics World or anywhere else.

    I collected a bunch of cosmology resource links and posted them
    in "General Astronomy and Cosmology" Forum here at PF, in a
    thread started by Moni. We needed somewhere to put all the good
    cosmology resource links together in one place.
    Moni's thread is called "Universe Infinite!!!"
    the PF post-id is about 130338
    https://www.physicsforums.com/showthread.php?s=&postid=130338#post130338
    If I was recommending any articles to you it would be
    one of those links I just posted. But I wouldnt be recommending
    just now! You seem to already have plenty to read and think about
    so you dont need kibbitzing from me!

    BTW presentday accelerating expansion is similar in kind but different in degree from the "Inflation" scenario ascribed to very early universe.
    Inflation, in cosmology, is just another term for accelerated expansion. So if you can believe that Inflation happened, around time of big bang, then it should not be too difficult to believe in dark energy and accelerating expansion now-----especially as we have the Supernova evidence of it that we can actually observe.

    If you have time to look at something completely different, how about
    glancing at "Expanding Confusion" by two Australian astronomers, Tamara Davis and Charles Lineweaver.
    http://arxiv.org./abs/astro-ph/0310808
    The expansion of space means that the separation between two points can often be increasing at a rate which is greater than the speed of light. See what you think. (Unless that is already old stuff for you.)
     
    Last edited: Jan 16, 2004
  9. Jan 17, 2004 #8
    Marcus, I found these documents:
    arXiv:astro-ph/0308418 0311344 and 0311381.
     
  10. Jan 17, 2004 #9

    marcus

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    Last edited: Jan 17, 2004
  11. Feb 12, 2004 #10
    Another one disputed dark matter and dark energy.

    arxiv.org/abs/astro-ph/0306180
     
  12. Feb 12, 2004 #11

    marcus

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    thanks Sammywu, it is good to know that you are skeptical about
    these proposed things----dark matter and dark energy
    http://arxiv.org/abs/astro-ph/0306180

    so often people (including myself) accept what experts say without too much critical scrutiny
    I do this in many cases because I TRUST that there are plenty of skeptical people out there who will blow the whistle
    and I dont have time or capacity to be skeptical of everything.

    I had a fantasy about this that you would write a short essay
    about why it is reasonable to suspect that dark matter and energy do not exist-----and (very important) how the observations can be explained by alternative means

    you could quote from these arxiv papers you have found

    it would be a service to those others of us who do not have the energy to challenge these things.

    Personally I accept dark energy and matter because I cannot imagine any other way to explain the observations and if I try to think how they could not exist I just end up wracking my brains and not getting anywhere-----so in the end I just have to accept them.

    Do us a favor and explain clearly how they could not exist :wink:
     
  13. Feb 13, 2004 #12

    wolram

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    a paper dated jan 2004
    gravitation, the dark matter effect
    and the fine structure constant.

    the good news and the bad news, or is it just how you
    interpret the raw data?

    http://arxiv.org/PS_cache/physics/pdf/0401/0401047.pdf

    Gravitational anomalies such as the mine/borehole g anomaly, the near-flatness of the spiral galaxy rotation-velocity curves, currently interpreted as a `dark matter' effect, the absence of that effect in ordinary elliptical galaxies, and the ongoing problems in accurately determining Newton's gravitational constant G_N are explained by a generalisation of the Newtonian theory of gravity to a fluid-flow formalism with one new dimensionless constant. By analysing the borehole and spiral galaxy data this constant is shown to be the fine structure constant alpha=1/137. This formalism then also explains the cause of the long-standing uncertainties in G_N and leads to the introduction of a fundamental gravitational constant G not = G_N with value G=(6.6526 +/- 0.013)x 10^-11 m^2s^{-2}kg^{-1}. The occurrence of alpha implies that space has a quantum structure, and we have the first evidence of quantum gravity effects.
     
    Last edited: Feb 13, 2004
  14. Feb 13, 2004 #13

    wolram

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    http://arxiv.org/abs/astro-ph/0401398

    Newtonian mechanics indicates that galaxies and galaxy clusters are much more massive than we would have guessed from their luminosities, with the discrepancy being generally attributed to dark matter halos. An alternative hypothesis is that accelerations in very weak gravitational fields are larger than predicted by Newton's laws, and there is no need for dark
    -------------------------------------------------------------------


    http://physicsweb.org/article/news/7/9/1

    Astrophysicists will be scratching their heads following the discovery that three elliptical galaxies seem to contain little or no dark matter. A team led by Aaron Romanowsky of the University of Nottingham in the UK found that the dynamics of the elliptical galaxies could be explained without the need for dark matter, in contrast to the motion of spiral galaxies. The unexpected result questions the widely held belief that elliptical galaxies form when galaxies rich in dark matter collide (A Romanowsky et al 2003 Sciencexpress 1087441 ).
     
  15. Feb 13, 2004 #14

    wolram

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    http://physicsweb.org/article/news/04/10/3

    However, McGaugh offers a different interpretation of the Boomerang results, proposing that the small second peak is evidence for a purely baryonic universe with no dark matter. He argues that many of the adjustments that have been made to cosmological models to account for the small second peak contravene other crucial constraints. McGaugh is a supporter of modified Newtonian dynamics (MOND) which, he claims, has had considerable success in predicting the dynamics of a wide variety of cosmological objects.
     
  16. Feb 13, 2004 #15

    wolram

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    it seems that we havent accounted for all the baryonic
    matter yet.
    ---------------------------------------------------------------------

    http://arxiv.org/PS_cache/astro-ph/pdf/0401/0401202.pdf

    detection of warm-hot intergalatic medium.

    the baryonic census by Fukugita et al 1998 tells us that in the local
    universe we are still missing a significant fraction of baryons that
    are observed at high red shifts
    ----------------------------------------------------------------------------
    http://www.csiro.au/index.asp?type=mediaRelease&id=BigBangTheoryChallenged

    An Australian-led team of astronomers has challenged conventional Big Bang theory by finding that large numbers of stars may be living unseen in the space between the galaxies.

    Team leader Professor Ken Freeman of the Australian National University will describe the finding tomorrow [24 March] at a meeting in Sydney hosted by CSIRO's Australia Telescope National Facility and the Anglo-Australian Observatory.

    "All these extra stars mean that there is too much normal ('baryonic') matter in the Universe to fit well with the current version of the Big Bang theory," Professor Freeman says.
     
  17. Feb 13, 2004 #16

    wolram

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    http://www.csiro.au/index.asp?type=mediaRelease&id=UndeadStarTorpedoes

    Using CSIRO data a West Australian PhD student has found a star that is not supposed to exist. His discovery is published in today's issue of the journal Nature.
    -----------------------------------------------------------------------------We found this pulsar only because it's relatively nearby - about 600 light-years away," says Mr Young. "It has a small beam and a fairly weak signal. This means there could be a lot more slow, old pulsars lurking out there undetected. Our best guess is about 100 000 in the Galaxy - as many as all the other pulsars put together."
     
  18. Feb 13, 2004 #17

    marcus

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    Hello wolram,
    it looks like I am responding to an earlier post of yours and in the meantime you have posted a bunch more. Cant tell what to think about Cahill's measurement of G
    --------earlier wolram post------
    a paper dated jan 2004
    gravitation, the dark matter effect
    and the fine structure constant.

    the good news and the bad news, or is it just how you
    interpret the raw data?

    http://arxiv.org/PS_cache/physics/pdf/0401/0401047.pdf

    Gravitational anomalies such as the mine/borehole g anomaly, the near-flatness of the spiral galaxy rotation-velocity curves, currently interpreted as a `dark matter' effect, the absence of that effect in ordinary elliptical galaxies, and the ongoing problems in accurately determining Newton's gravitational constant G_N are explained by a generalisation of the Newtonian theory of gravity to a fluid-flow formalism with one new dimensionless constant. By analysing the borehole and spiral galaxy data this constant is shown to be the fine structure constant alpha=1/137. This formalism then also explains the cause of the long-standing uncertainties in G_N and leads to the introduction of a fundamental gravitational constant G not = G_N with value G=(6.6526 +/- 0.013)x 10^-11 m^2s^{-2}kg^{-1}. The occurrence of alpha implies that space has a quantum structure, and we have the first evidence of quantum gravity effects.
    ---------end quote------------

    Reginald Cahill believes that the NIST figure for GNewt
    is too high by a factor involving alpha the fine structure constant.
    the real G is
    [tex]G_{Oz} = (1 - \frac{\alpha}{2})G_{Newt}[/tex]

    and this he has measured down a borehole where the dark energy cannot get at things and contaminate the Cavendish apparatus.
    I believe I will save this until about 16 hours this afternoon
    and think about it then
     
    Last edited: Feb 13, 2004
  19. Feb 13, 2004 #18

    wolram

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    MARCUS.
    i suppose you could call my postings a bit of mischief
    making, i posted his theory of gravity and the history
    of big G with another little snippet.
    the other posts are just to demonstrate that there is
    still baryonic matter to be accounted for in the
    equations, small amounts agreed but slowly adding up
    and not quite fitting in to present theories.

    will dark matter be found, not in my lifetime
    will gravitational radiation be found ditto
    will hawking's radiation be found ditto
    i accept no responsibility if any of the above predictions
    are incorrect.
     
  20. Feb 13, 2004 #19

    Phobos

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    Just skimmed the thread...sorry if this has been covered or is moot...

    Astronomy magazine (Jan 04) had a big article on GRBs and noted their consistent energy output (called them "standard bombs"). But it went on to note that there are still many uncertainties in GRB theories that need to be researched. I suspect more info is needed before we start relying on GRBs as a standard. One concern was that the apparent consistency of energy output may actually just be our inability to detect the weaker ones (and, I assume, there aren't many that get much stronger). So, we're only detecting the upper end of the phenomenon.

    Fortunately, NASA to launch the SWIFT satellite in May 2004. (or at least they did before Bush's announcement...now I'm not sure what the expect). It is hoped that the satellite will spot 300 GRBs/year and relay the info faster to astronomers on the ground so they can examine it before its gone.
     
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