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Insights Will all matter be converted to photons?

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  1. Aug 5, 2015 #1

    bcrowell

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    Last edited by a moderator: Aug 25, 2015
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  3. Aug 5, 2015 #2

    marcus

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    That's interesting. Could you say briefly how most (presumably mostly dead) stars eventually get ejected from whatever gravitationally bound structures like galaxies and galaxy clusters?

    I can see how assuming a cosmological constant--as in standard LCDM model-- once stuff is widely dispersed it has little or no chance of ever gathering back together again--much less forming black holes!

    What puzzles me is how galaxies and galaxy clusters get dispersed and gravitationally unbound. A simple cosmological constant like the one we appear to have wouldn't do that, would it? Our Local Group of galaxies would seem likely to end up as one single larger galaxy.

    Would one of these references explain the process of ejection?

    Adams and Laughlin, "A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects", Rev. Mod. Phys. 69 (1997) 337, http://arxiv.org/abs/astro-ph/9701131

    Baez, "The End of the Universe," 2004, http://math.ucr.edu/home/baez/end.html

    Penrose, Causality, quantum theory and cosmology. In On Space and Time, ed. Shahn Majid, Cambridge University Press, Cambridge, 2008, pp. 141-195. (ISBN 978-0-521-88926-1)

    Hu, "Hawking radiation from the cosmological horizon in a FRW universe," Phys.Lett. B701 (2011) 269-274, http://arxiv.org/abs/1007.4044
     
  4. Aug 5, 2015 #3

    marcus

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    Adams and Laughlin:
    ==quote abstract, and page 12==
    This process tails off as the galaxy gradually depletes its stars by ejecting the majority, and driving a minority toward eventual accretion onto massive black holes. ...
    ...
    Thus, stars escape from the galaxy with a characteristic time scale η ≈ 19 − 20 (see also Islam, 1977; Dyson, 1979).

    The stellar dynamical evolution of the Galaxy is more complicated than the simple picture outlined above. First, the galaxy is likely to have an extended halo of dark matter, much of which may be in non-baryonic form. Since this dark halo does not fully participate in the dynamical relaxation process, the halo tends to stabilize the system and makes the stellar evaporation time scale somewhat longer than the simple estimate given above.
    ==endquote==
    I can visualize the mechanism of a galaxy flinging away most of its stars. But I suppose most of the galaxy mass is in the DM halo, so I'm not convinced they actually get flung out with escape velocity by a mere concentration a *minority* of the baryonic matter into BH a la Adams and Laughlin.

    Still it's an interesting idea

    John Baez invokes COMPUTER SIMULATIONS! Somewhere after about 10 line or paragraph breaks in his essay he says:
    ==quote Baez, http://math.ucr.edu/home/baez/end.html ==
    The black holes will suck up some of the other stars they encounter. This is especially true for the big black holes at the galactic centers, which power radio galaxies if they swallow stars at a sufficiently rapid rate. But most of the stars, as well as interstellar gas and dust, will eventually be hurled into intergalactic space. This happens to a star whenever it accidentally reaches escape velocity through its random encounters with other stars. It's a slow process, but computer simulations show that about 90% of the mass of the galaxies will eventually "boil off" this way - while the rest becomes a big black hole.
    ==endquote==
    I still wonder if the sims included DM and if so how they included it. But Baez is .... like so many people I'm a fan...so maybe provisionally I have to accept this 90% "boiling off"
     
    Last edited: Aug 5, 2015
  5. Aug 5, 2015 #4

    marcus

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    In case anyone else is interested in this and wants to research it, here is the Inspire record for Adams Laughlin
    http://inspirehep.net/record/428242?ln=en
    and here are the 67 papers that have cited that one:
    http://inspirehep.net/search?ln=en&p=refersto:recid:428242
    Including this one by Harvard's Abraham Loeb
    http://arxiv.org/abs/1102.0007
    Cosmology with Hypervelocity Stars
    Abraham Loeb (Harvard)
    (Submitted on 31 Jan 2011)
    In the standard cosmological model, the merger remnant of the Milky Way and Andromeda (Milkomeda) will be the only galaxy remaining within our event horizon once the Universe has aged by another factor of ten, ~10^{11} years after the Big Bang. After that time, the only extragalactic sources of light in the observable cosmic volume will be hypervelocity stars being ejected continuously from Milkomeda. ...
    ...
    4 pages, 2 figures, accepted for publication in the Journal of Cosmology and Astroparticle Physics (JCAP, 2011)
     
  6. Aug 5, 2015 #5

    Chalnoth

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    I don't know. If the cosmological constant is true, then everything but photons will dilute away to nothing (so that there is at most one massive particle per Hubble volume, with most containing no massive particles).

    Protons will decay (leaving no solid objects). Black holes will evaporate. That leaves electrons, neutrinos, dark matter, and photons. Bound objects will eventually dissipate through some combination of annihilation and gravitational interactions. Particles not bound to gravitational potentials should, given a cosmological constant, eventually become the only particle in their horizon.

    Photons should remain (at an exceedingly low temperature) due to Hawking radiation from the cosmological horizon.
     
  7. Aug 5, 2015 #6

    marcus

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    Numerical work!
    http://arxiv.org/abs/astro-ph/0310505
    Future Evolution of the Intergalactic Medium in a Universe Dominated by a Cosmological Constant
    Kentaro Nagamine, Abraham Loeb (Harvard-CfA)
    (Submitted on 17 Oct 2003 (v1), last revised 29 Mar 2004 (this version, v2))
    We simulate the evolution of the intergalactic medium (IGM) in a universe dominated by a cosmological constant. We find that within a few Hubble times from the present epoch, the baryons will have two primary phases: one phase composed of low-density, low-temperature, diffuse, ionized gas which cools exponentially with cosmic time due to adiabatic expansion, and a second phase of high-density, high-temperature gas in virialized dark matter halos which cools much more slowly by atomic processes. The mass fraction of gas in halos converges to ~40% at late times, about twice its calculated value at the present epoch. We find that in a few Hubble times, the large scale filaments in the present-day IGM will rarefy and fade away into the low-temperature IGM, and only islands of virialized gas will maintain their physical structure. We do not find evidence for fragmentation of the diffuse IGM at later times. More than 99% of the gas mass will maintain a steady ionization fraction above 80% within a few Hubble times. The diffuse IGM will get extremely cold and dilute but remain highly ionized, as its recombination time will dramatically exceed the age of the universe.
    Comments: 22 pages, 10 figures. Accepted to New Astronomy. Movies and a higher resolution version of the paper are available at http://cfa-www.harvard.edu/~knagamine/FutureIGM [Broken]

    http://arxiv.org/abs/astro-ph/0204249
    Future Evolution of Nearby Large-Scale Structure in a Universe Dominated by a Cosmological Constant
    Kentaro Nagamine, Abraham Loeb (Harvard-CfA)
    (Submitted on 15 Apr 2002 (v1), last revised 12 Nov 2002 (this version, v3))
    We simulate the future evolution of the observed inhomogeneities in the local universe assuming that the global expansion rate is dominated by a cosmological constant. We find that within two Hubble times (~ 30 billion years) from the present epoch, large-scale structures will freeze in comoving coordinates and the mass distribution of bound objects will stop evolving. The Local Group will get somewhat closer to the Virgo cluster in comoving coordinates, but will be pulled away from the Virgo in physical coordinates due to the accelerated expansion of the Universe. In the distant future there will only be one massive galaxy within our event horizon, namely the merger product of the Andromeda and the Milky Way galaxies. All galaxies that are not gravitationally bound to the Local Group will recede away from us and eventually exit from our event horizon. More generally, we identify the critical interior overdensity above which a shell of matter around an object will remain bound to it at late times.
    Comments: Accepted for publication in New Astronomy, 2002. Improved discussions. Higher resolution figures are available at http://cfa-www.harvard.edu/~knagamine/LocalGroup [Broken]
    ==quote page 3==

    The resulting mass of each dark matter particle in the high resolution region
    is 3.6 × 1011h−1M⊙⋆
    (comparable to the mass of an L*galaxy), and the number of high resolution particles is half a million.
    ==endquote==
     
    Last edited by a moderator: May 7, 2017
  8. Aug 5, 2015 #7

    bcrowell

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    Yes, the Baez article explains it briefly. See "(It may seem odd..."

    I think it's closely analogous to a counterintuitive fact about thermodynamics, which is discussed in Peierls, Surprises in theoretical physics, p. 55. Consider an isolated galaxy in infinite space. If there were an equilibrium state, the galaxy would be recapturing stars and losing them at equal rates. Note that fluctuations can always kick out a star, because there is no impediment due to conservation of energy. You can always reduce the PE to any extent you like by bringing some of your stars sufficiently close together. So the rate of loss is never zero. But the rate of recapture decreases with the volume of the surrounding space, and approaches zero as the volume approaches infinity. Therefore there can never be an equilibrium state.
     
  9. Aug 5, 2015 #8

    bcrowell

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    Thanks for your comments. I think you're right. I need to modify my statements. It is not true, as I stated, that massive particles dominate the mass-energy density of the final state of the universe. However, it is true that stable, massive particles continue to exist.

    Re this, "Particles not bound to gravitational potentials should, given a cosmological constant, eventually become the only particle in their horizon," you can actually omit the qualifying phrase at the beginning. Gravitationally bound systems will still (counterintuitively) evaporate. This is discussed in the Baez article and also in #7.
     
  10. Aug 6, 2015 #9
    Can i know the power of gravitational force at the black hole will never get reduced while it consumes many subbatomic particles?
     
  11. Aug 6, 2015 #10
    While there is still infalling matter a black hole will continue to grow in mass and it's associated gravity increases.
    It's quite possible though that a black hole after a very long time will eventually clear out most other material in it's region, it has nothing left to consume.
    According to Stephen Hawkins it should at that point very gradually start losing overall mass due to a form of radiation.
     
  12. Aug 6, 2015 #11
  13. Aug 7, 2015 #12
  14. Aug 7, 2015 #13

    mfb

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    Conservation of angular momentum gives a good argument why most stars have to get ejected: a single massive black hole has a tiny angular momentum, so most angular momentum has to leave the galaxy. This happens via ejecting radiation (negligible), mass (!) and gravitational waves. Gravitational waves are important in the direct vicinity of the black hole, but negligible for objects somewhere else in the galaxy.
     
  15. Aug 7, 2015 #14
    I'm somewhat flattered by this featured thread. It's less than three days before this that I post: https://www.physicsforums.com/threads/heat-death-of-the-universe.825752/#post-5186170
    And this thread addresses exactly my point: Will all matters sucked to form a single black hole and then evaporated through Hawking radiation into photon.
    So the orbit of the celestial bodies are not deterioting?
    So this calculation also include 'dark matter'? That is supposedly bound celestial bodies to revolve around the Galaxy centre.
    Or 'dark matter' only hold galaxies to orbit the centre of the supercluster, not stars to orbit SMBH?
     
  16. Aug 7, 2015 #15
    Ahh, I can't edit or delete my post:
    MFB has answered it:
     
  17. Aug 7, 2015 #16

    bcrowell

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    I don't follow you here. This might explain why we can't have a central black hole eat up its entire host galaxy, but that would have never occurred to me in the first place as a plausible possibility. I think what most people would expect would be that the galaxy would continue to be bound and stay in pretty much the same state -- which isn't what happens, for the reasons explained in #7 and in the Baez article.
     
  18. Aug 7, 2015 #17

    bcrowell

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    The scattering of matter out of a gravitationally bound system follows from very basic considerations relating to statistical mechanics, as described in #7 and the Baez article. It doesn't matter whether the matter is in the form of stars or dark matter.
     
  19. Aug 7, 2015 #18

    mfb

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    Well, it cannot stay in the same state, if nothing else would happen the emission of gravitational waves would eventually let everything fall into the central black hole.
     
  20. Aug 8, 2015 #19
    How does a gravitational waves would eventually let everything fall into the central black hole? They are just waves. you assuming that these waves are likes sea waves?which comes forth and move backwards?
     
  21. Aug 8, 2015 #20

    mfb

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    Orbiting bodies emit gravitational waves and lose energy in the process, which makes their orbits get closer over time.

    This is an incredibly slow process for stars orbiting a galaxy, but it is notable in close binary systems. PSR B1913+16 is the most famous system, PSR J0737-3039 is even better to study.
     
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