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At the edge of black hole, matter and antimatter is created, while the matter escape, antimatter annihilate inside the black hole thus decreasing it mass. But due to immense gravitation pull, why the newly generated matter also get pulled into the black hole, since it will have very less velocity to escape ?

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  • $\begingroup$ photons at least can! $\endgroup$
    – J. Chomel
    Jan 25, 2018 at 10:12
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    $\begingroup$ I think your first misunderstanding might be thinking that antimatter has negative mass. It doesn't. Antimatter falling into a black hole doesn't decrease the black hole's mass. $\endgroup$
    – James K
    Jan 27, 2018 at 6:10
  • $\begingroup$ @JamesK then why it is said that blackhole will evaporate with time ?? $\endgroup$
    – Gauti
    Jan 27, 2018 at 10:10
  • $\begingroup$ That would be a separate question: Research it then ask. $\endgroup$
    – James K
    Jan 27, 2018 at 12:38
  • $\begingroup$ blackhole evaporation is related to hawking radiation only . en.wikipedia.org/wiki/Hawking_radiation $\endgroup$
    – Gauti
    Jan 27, 2018 at 17:00

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For one thing, the mechanism behind Hawking Radiation is, as yet, unknown. Hawking, in his original formulation, never proposed a means by which this radiation was produced. The concept of particle-antiparticle pair production near the event horizon came as an after thought and there's no guarantee that is the way in which Hawking Radiation is actually produced. There are other potential explanations out there.

To address your more specific question though, I'd point out that your logic is a bit faulty. Under the assumption that Hawking Radiation can actually occur we necessarily know that energy is getting away from Black Holes which means that energy/matter must necessarily be able to achieve the escape velocity $-$ otherwise it wouldn't be escaping! So to propose the matter has less than the escape velocity is a non-starter since it's a fallacious premise.

That being said, the more direct answer to your question would be to explain how and why this Hawking Radiation can achieve escape velocity. Keep in mind first that the radiation which is escaping is doing so from outside the event horizon in which you can escape with a velocity less than or equal to $c$. Primarily what is escaping as Hawking Radiation are photons which of course travel at $c$ and, being outside the event horizon, are perfectly capable of escaping the black hole.

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  • $\begingroup$ I'd thought that the idea that the vacuum was filled with virtual pairs (en.wikipedia.org/wiki/Quantum_fluctuation) was established, and that Hawking radiation was inevitable near an event horizon. I didn't know the mechanism was still under such a cloud of uncertainty (pardon the pun). $\endgroup$
    – uhoh
    Jan 25, 2018 at 23:17
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    $\begingroup$ @uhoh The concept of pair production is certainly well established. What isn't established is that pair production near the event horizon is the cause of Hawking radiation. The wiki page on Hawking radiation discusses this point a bit. $\endgroup$
    – zephyr
    Jan 25, 2018 at 23:19
  • $\begingroup$ OK i'll give it a look after sufficient coffee. Thanks! $\endgroup$
    – uhoh
    Jan 25, 2018 at 23:23
  • $\begingroup$ @zephyr thanks..why it is said that black hole will shine in infrared, if we are not exactly sure what kind of particles are radiated out of it ? $\endgroup$
    – Gauti
    Jan 27, 2018 at 10:12
  • $\begingroup$ @Gauti I'm not sure what your source is which says black holes shine in the infrared, but whatever that source is, they must have assumed a particular mechanism for hawking radiation and calculated it based on that assumption. $\endgroup$
    – zephyr
    Jan 29, 2018 at 18:14

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