Dark Energy vs . Black Holes

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Reiku, Oct 19, 2007.

  1. Reiku Banned Banned

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    DARK-ENERGY STARS vs. BLACK HOLES


    For three days in April, 2005, I was a speaker and panelist at the NASA-sponsored “Physics for the 3rd Millennium II Conference” in Huntsville, Alabama, where twelve of us, including two Nobel Laureates, were invited to give 50-minute lectures about cutting-edge physics to an audience of NASA engineers, teachers, students, parents, and other interested attendees. In this column, I want to tell you about the work described in one of the talks, given by Dr. George Chapline of the Lawrence Livermore Laboratory.

    The issue that Chapline addressed had previously been brought into sharp focus in a science fiction story, Poul Anderson’s widely reprinted “Kyrie”, in which an intelligent energy-being falls into a black hole while in telepathic contact with a nun in a nearby spaceship. Near the event horizon of the black hole where time stops due to gravitational time dilation, the being is trapped in agony, presumably for all eternity.

    If a collapsing star has enough mass, the star cannot be stabilized by repulsion from the strong interaction, and so it collapses to a black hole. According to Einstein’s general relativity, as one approaches such a collapsed star, the increasing gravity field causes time to slow down until, on a surface called the “event horizon,” time stops altogether and an infalling object “freezes” there. Curiously, the general relativity description of a fall through the event-horizon depends on the situation of the observer. As viewed by an outside observer, time effectively comes to a halt for the infalling object, so that it appears to freeze at the event horizon. However, from the viewpoint of the unfortunate observer who is falling through the event horizon and into the black hole, nothing unusual happens as the event horizon is crossed except that contact with the external universe is cut off.

    Chapline argues that it is unreasonable that time comes to a halt in the external reference frame, while producing no observable consequences in the infalling observer’s frame. He suggests that quantum effects should become important near the event horizon.

    This suggestion goes against the conventional wisdom. Since the 1950s, there has been a general agreement among the physicist practitioners of general relativity that quantum effects should become significant only at very small distance scales, and that quantum mechanics can be comfortably ignored elsewhere. Chapline raises objections to this rule. He argues that the infinite time dilation at the event horizon of a black hole creates a situation in which quantum effects are needed, even though it is a macroscopic system. Further, he points out that quantum mechanics (which in its current formulation is not compatible with general relativity) requires some universal time standard, so that clocks can be synchronized and cross-referenced everywhere in a system. The behavior of time near the event horizon prevents such synchronization. If general relativity tries to stop the clocks, Chapline argues that quantum mechanics will “fix” this problem by producing a phase transition in the infalling matter as the event horizon is approached.



    To decide what should happen when quantum mechanics takes over, he considers an analogous situation, well described by quantum mechanics, which occurs in a vertical column of superfluid helium that has more pressure at the bottom than the top of the column due to the weight of the upper liquid. In such a situation, there is some particular vertical height at which the speed of sound in the liquid goes to zero. The sound waves encountering this zero-sound-velocity “barrier” should behave in a way that is analogous to the black hole situation in which the infalling particles attempt to cross the infinite time dilation barrier.

    In the superfluid case, when the sound waves come within a critical distance of the barrier, two things happen. First, the relation that the product of frequency times wavelength equals wave speed breaks down, and second, waves above a certain frequency become unstable, and their energy is dissipated in the liquid. Chapline suggests that a similar scenario should happen near the event horizon, and that in particular, the infalling particles, as they approach the event horizon, will become unstable. First the heavy particles like protons will decay into lighter particles like positrons and mesons, and then the quarks and leptons themselves will dissipate into the vacuum, raising the energy of the vacuum as they become “dark energy.” In other words, he hypothesizes that inside the event horizon, there are no particles, but only a dark-energy region where the cosmological constant is much larger than it is in the external world.

    As we have discussed in previous columns (for example, “Our Runaway Universe and Einstein’s Cosmological Constant”, Analog, May 1999), in general relativity, the dark energy of the vacuum creates a negative pressure that drives the accelerating expansion of the universe. Behind the event horizon, in Chapline’s scenario, the accumulating dark energy would create a large negative pressure that stabilizes the star, so that it never becomes a black hole, as that label is presently understood. Instead, the collapsed object becomes a dark-energy star.

    Therefore, according to Chapline, there are no black holes in our universe, only dark-energy stars that contract to some definite size at which they are stabilized by the negative pressure of the dark energy inside. This provides a new mechanism that prevents a collapsing star from progressing all the way to an information-destroying singularity. Instead, the phase change to dark energy would produce a stable system of finite size, with no singularities to worry about. Further, the supposed “evaporation” of black holes by the Hawking radiation process (which has never been observed) does not happen, because the quantum processes manifest themselves in a different way. It’s also interesting to note that the supposed thermodynamic connection between string theory and the surfaces of black holes, which has recently been publicized as a great triumph for string theory, may be based on questionable physics.



    Is there any evidence that the Chapline view of collapsed stars is correct? Perhaps so. There have been several space-based X-ray and gamma ray telescopes launched in recent years, and the resolution and sensitivity of these instruments has been improving, year by year. When these instruments look in the direction of our galactic center, they observe a remarkable and puzzling thing. There is a stream of antimatter electrons, the so-called “Positron Fountain,” coming from the galactic center region and producing a large quantity of 511-keV annihilation radiation there. This is probably related to another observation, of the population of charged particles in cosmic rays, which show that above a certain energy (~500 MeV) there is a definite excess of positrons over electrons in the population of charged particles reaching the solar system. These preferences for positrons are a mystery, since fundamental interactions, e.g. electron-positron pair creation, produce matter and antimatter electrons in an even-handed way, favoring neither one nor the other.

    Chapline suggests that these positron-favoring phenomena are the result of enhanced proton decay as the particles become unstable near the event horizons of dark-energy stars. In the 1980s, there were predictions from grand unified theories that the proton might be intrinsically unstable, and that in the fullness of time it might decay, for example, to a positron and one or more pi mesons. Subsequent experimental attempts to observe such decays have failed, thereby falsifying the simplest versions of grand unification theories and setting fairly low upper limits on the probability that a proton might decay in vacuum. However, in the vicinity of an event horizon, Chapline suggests that the decay rate of the proton is greatly enhanced, so that there is a much higher probability of proton decay. Some fraction of the positrons from such decays, particularly those with high energies, should escape the strong gravity field of the collapsed star, perhaps accounting for the observed positron cosmic ray abundance and the positron fountain at the galactic center. Chapline also makes the case that destabilization of infalling matter could account for the energy distributions observed in gamma ray bursts.

    Chapline further suggests that the dark matter in our universe might be an artifact of the same physics. Perhaps our normal vacuum is already close to the quantum transition point between normal vacuum and the dark energy continuum, with dark matter showing up in the vacuum because of the close proximity to the transition conditions. His papers are not specific enough to convince me that this would have the properties needed to account for the concentrations of dark matter near galactic clusters, but it’s an interesting idea.

    However, we might ask whether all of the recent publicity about the “observation” of black holes at the centers of our own and other galaxies contradicts these ideas. Doesn’t the observation of black holes preclude the existence of dark-energy stars?

    No, it doesn’t. The label “black hole” is now conventionally attached to any collapsed astronomical object heavier than a neutron star. The observations mentioned concern the accelerations of nearby stars and the existence of an accretion disk around the objects. Necessarily, there is no observational evidence of what lies inside the event horizons of the objects. Thus, the astronomical observations would be consistent with either a black hole or a dark energy star.



    Since this is a science fiction magazine, let’s suppose that Chapline is correct and consider the SF implications of his new twist on collapsed stars. First, all the SF that involves penetrating through the event horizon of a black hole is invalidated. For example, Fred Pohl’s Heechee in his Gateway series would not have been able to burrow behind the event horizon of an assembled low-tidal-force black hole, because when they approached the horizon, the Heechee populace would be converted into dark energy.

    But it does bring up some interesting questions. Suppose that by some mechanism (a wormhole?) one could reach the interior of a dark-energy star. How does the flow of time work inside the event horizon? Would the interior be a completely hostile environment? Could matter exist inside, if it didn’t have to come in through the event horizon? Would the high cosmological constant there induce a “Big Rip” in any matter present? Would the laws of physics there be those we understand? Could one “drain” the accumulated dark-energy through a wormhole and use it as an inexhaustible energy source?

    Perhaps, if Chapline’s ideas can withstand observational tests and theoretical scrutiny, we may learn the answers to some of these questions.



    AV Columns Online: Electronic reprints of over 120 “The Alternate View” columns by John G. Cramer, previously published in Analog, are available online at: http://www.npl.washington.edu/av. The preprints referenced below can be obtained at: http://www.arxiv.org.



    References:

    “Dark Energy Stars,” G. Chapline, Proceedings of the Texas Conference on Relativistic Astrophysics, Stanford, CA, December 12-17, (2004), preprint astro-ph/0503200

    “Have Nucleon Decays Already Been Seen?” J. Barbierii and G. Chapline, Phys Lett. B 590, 8, (2004);

    “Quantum Phase Transitions and the Breakdown of Classical General Relativity”, G. Chapline, E. Hohlfeld, R. B. Laughlin, D. I. Santiago, Int. J. Mod. Phys. A18 3587-90 (2003), preprint gr-qc/0012094.''

    By Dr. John G. Cramer
     
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  3. Cyperium I'm always me Valued Senior Member

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    Thank you, it was interesting. I wonder what dark matter would look like

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  5. Reiku Banned Banned

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    Hi Cyper

    Dark matter could be anything. The same goes for dark energy. Equally just important, and simultaneously worrying is that it could be neither.
     
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  7. Cyperium I'm always me Valued Senior Member

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    After all, we name it dark matter since we don't know what it is, if it is ordinary matter that is "converted" into dark matter, would it do anything to the properties of that matter? Would iron dark matter be different from gold dark matter?

    But I think that it should change form due to the convertation (sp?) process.
     
  8. Reiku Banned Banned

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    Yes. There will be a dark matter periodic table.

    One type of element is the axion. This particle can actually move through solid objects without its velocity being tampered with!
     
  9. Cyperium I'm always me Valued Senior Member

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    If it is the curving space that hinders the velocity, wouldn't that mean that the axion moves to a certain degree above space and time? If it would follow the curvation of spacetime then wouldn't we notice the speed difference?
     
  10. Reiku Banned Banned

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    It was Peccei-Quinn in 1977 who stipulated the axion, and as I believe, it was created to resolve a problem in the strong-CP for QCD. The following will be the reasoning why it was predicted… and I’ll explain anything else too.
    Until the 1950's, the view was that the laws of quantum physics remained absolutely unchanged when one changes the sign of spatial coordinates, such as x, y, z into -x, -y and -z; this particular mirror structure is called the parity, symbolized with P. However, C.S. Wu realized that the left-handed neutrino had no mirror reflection, (the left-handed neutrino), thus the symmetry of 'weak interaction' was violated through the parity; the symmetry could only be revived, if one considered that P could not be alone, and one must introduce the invariant of CP into the equation - - - hence, the CP Violation. 'C' stands for 'charge conjugate', which is the transformation of a particle into its antipartner, such as an electron into a positron. In Wu's case, a left-handed neutrino can be transformed into a right-handed antineutrino.
    In 1964, physicists James Cronin and Val Vitch found a symmetry violation in the CP transformation, in observations on the K-meson, or ''Kaon'' particle. In short, they showed that the Antikaon is not the absolute mirror symmetry of the neutral Kaon. The Antikaon was shown to have a smaller life expectancy than its neutral partner. They received a Nobel Prize for their discovery.
    The increasing studies into CP Violation, and fundamental asymmetry is having scientists ask why matter should be dominant in this universe, and not just a soup of gamma ray energy; the result when a particle comes into contact with an antiparticle. Even though the universe is vastly wide, and that ordinary matter covers only a mere 1% of spacetime, an even smaller percentage of this should be made up of antimatter - perhaps a mere 0.011%... though Cp Violation is telling us possibly why there isn't that much antimatter in the universe.
    Other theorists have concluded that a very heavy boson, dubbed the X-boson, might decay in such a way it is able to violate CP... However, the X-boson comes at a price; it would state that the proton is not infinitely stable! If the proton does decay, it's lifetime is expected to be something like 10^30 years. Though, so much controversy clouds the lifespan of the proton, if it even has a calculable lifespan. One might ask why we have never observed the X-boson... The X-Boson cannot be verified objectively, though it could be proven indirectly through proton decay.
    Together with the effects of the weak violation, the strong violation given as , is found to be an intrinsic parameter of the theory, even though it isn’t predicted! This was what led to a paradox of physics, because the strong effective violation would cause the neutron to eventually have a dipole moment… and as we know, the neutron is a neutral particle with no charge, but it seems to work, because of certain predictions concerning the neutron. But it is also predicted to be very rare.
    The theory seems to ask… ‘’why is this variable [X] close to vanishing numbers?’’
    An interesting solution came about. If at least one of the quarks in this model, creating the neutron are massless, then the variable becomes unobservable. But this doesn’t seem right from a quantum physical view, because none of the quarks are predicted to be massless… (But I like the idea).

    Then a second solution was devised by R. Peccei and H Quinn creating the ‘’global symmetry solution of Peccei-Quinn’’. They invited a new particle into the mix for the solution of the strong CP problem, which involves also spontaneous symmetry violations creating this new particle. This will now make the following… X = 0, instead of some non-zero total close to zero. As I am sure you can guess, this was when the dark matter particle ‘’axion’’ was created.

    It turns out that the axion has no electric charge, and has a vanishingly small mass of 10^-6 and super low interactions with the weak and strong forces. They can interact with other corporeal particles, but only very rarely. This is, it appears, the reason why they have the properties they have.
    A recent proposal was made suggesting that axion particles might be able to be teased from a transverse magnetic field, using photons to tease the dark matter out. I am still awaiting to hear any results of this experiment.
     
  11. kaneda Actual Cynic Registered Senior Member

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    If something is put in a heavier than normal gravity field, it is said to experience "time dilation". Might it not instead just be experiencing gravity? We have electrons travelling around a nucleus. In a stronger than 1G gravity field, surely they would have to work harder and as the gravity increases, the orbits would become smaller and the object more compacted?
     
  12. Reiku Banned Banned

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    I suppose it is scientifically probable.
     

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