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Thread: Question about Hawking Radiation

  1. #1 Question about Hawking Radiation 
    Forum Bachelors Degree x(x-y)'s Avatar
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    Hawking radiation, as I understand it, theorises that virtual particles forming at the event horizon of a black hole will become seperated from each other preventing annihilation- which would usually occur. The process theorises that over large amounts of time, a black hole will radiate away it's entire mass- leaving "nothing" (however, this creates a problem in itself, as I've heard, in the form of the "black hole information paradox").

    So, anyway, my question is: how does this process show a black hole losing mass? I would've thought that, to an outside observer, the black hole is gaining mass as it takes in a virtual particle every time virtual antipairs form on the event horizon. One thing I can think of to answer my own question is that the energy required to form the virtual antipair of particles in the first place comes from the black hole, and so every time this occurs the black hole is losing 50% of the energy it used to form the virtual particles from one "flying away" from the black hole- and the other 50% entering the black hole in the form of the anti-particle. But, I'm not sure if that is right.

    Also, could it be true that the "black hole information paradox" could be solved, assumung Hawking Radiation occurs, by proving that the information contained within the black hole is carried away by the virtual particles?

    Thanks in advance.


    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
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  3. #2  
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    Honestly, maybe Hawking radiation is a nice concept, but ... it contradicts the existence of black holes
    As you say, it means that the matter inside is just destroyed and its energy is transformed into massless radiation - it violates baryon number conservation law.

    If baryon number doesn't have to be conserved in extreme conditions like of black holes (or while baryogenesis creating more matter than antimatter), while neutron star collapse any possible condition limit is exceeded in its core - so destroying baryons (proton/neutron decay) should start not after creating 'black hole matter state' of infinite density, but before - releasing huge amount of energy and so preventing such hypothetical singularity of matter.

    The hypothesis that extreme mass creates 'black hole state' silently assumes that 'matter is indestructible': baryon number is ultimately conserved.
    In other case nature would start 'burning' its baryons before this infinity.


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  4. #3  
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    Quote Originally Posted by Jarek Duda
    Honestly, maybe Hawking radiation is a nice concept, but ... it contradicts the existence of black holes
    As you say, it means that the matter inside is just destroyed and its energy is transformed into massless radiation - it violates baryon number conservation law.

    If baryon number doesn't have to be conserved in extreme conditions like of black holes (or while baryogenesis creating more matter than antimatter), while neutron star collapse any possible condition limit is exceeded in its core - so destroying baryons (proton/neutron decay) should start not after creating 'black hole matter state' of infinite density, but before - releasing huge amount of energy and so preventing such hypothetical singularity of matter.

    The hypothesis that extreme mass creates 'black hole state' silently assumes that 'matter is indestructible': baryon number is ultimately conserved.
    In other case nature would start 'burning' its baryons before this infinity.
    Baryon number is only approximately conserved in ordinary circumstances. Black holes are not "ordinary circumstances" anyway.
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    Baryon number is only approximately conserved in ordinary circumstances. Black holes are not "ordinary circumstances" anyway.
    The question is where is this boundary of "ordinary circumstances"?
    It is believed that baryogenesis is above it, allowing to create more baryons than antibaryons ...

    Anyway, as far this boundary is, collapsing neutron star is believed to exceed all possible limits for density/temperature ... so if 'baryon state' isn't global energy minimum of the field, but only local - guarded by some energy barrier, such barrier would be also exceeded (releasing this energy) before creating 'black hole state' ...
    ... which is already believed to allow to exceed this energy barrier due to Hawking radiation ...

    I know reasons that charges/spins are conserved (guarded by field around thanks of Stokes theorems: Coulomb/Ampere law), but are there any reasons for ultimate conservation of other numbers?
    Modern particle models like supersymmetric requires proton decay.
    Ok - they cannot find it, but where they are looking for it ... in water tanks, assuming that huge energy to exceed such hypothetical energy barrier would be spontaneously created in water chemistry ... but maybe Boltzmann distribution doesn't longer behave well so far far away?
    I would rather search for it in high energy physics like LHC (very difficult, required dedicated experiments) or in neutron stars/supernovas ... especially there are no reasonable energy sources for the gamma-ray bursts ...
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    The evaporation comes from conservation laws. When a virtual particle pair is created its from 'borrowed' energy. After a period of time specified by the uncertainty principle, this borrowed energy MUST be re-paid to the universe. If one of the created virtual particles is trapped by an event horizon, effectively removing it from our universe, it cannot re-combine with its mate and re-pay the borrowed energy. The law of conservation of energy demands the loan be paid back and so it takes the energy ( read mass ) from the black hole's mass. In effect the black hole swallows a patrticle's mass, but actually ends up losing mass and so it evaporates.

    I don't know what information paradox you mean. Black holes are theorised to destroy all information except for a few things that are conserved ( charge, angular momentum and mass/energy ) and some that an be calculated from the conserved quantities ( entropy and temperature ).
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  7. #6  
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    Quote Originally Posted by MigL
    I don't know what information paradox you mean. Black holes are theorised to destroy all information except for a few things that are conserved ( charge, angular momentum and mass/energy ) and some that an be calculated from the conserved quantities ( entropy and temperature ).
    That is not quite true.

    The destruction of information by black holes was proposed by Hawking who has since changed his mind and conceded a bet with John Preskill. Others are not convinced.

    The rationale for Hawking's concession lies in string theory and at least one unproved conjecture, the AdS/CFT correspomdence.

    Susskind wrote a particularly badly skewed account of this in The Black Hole War.
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    It may not be decided but I wouldn't say its untrue, yet.

    All I know about AdS/CFT correspondence is that it is based on supersymmetry, or spin symmetries which predict the existence of companion particles and force carriers with names like selectrons, photinos and gluinos. Some of these should have been found at the LHC since their energies are in the right range. But so far, nothing.
    Its a gut feeling but I don't have a good feeling about supersymmetry, or current string theory for that matter. I believe you've voiced the same opinion numerous times.
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