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I suppose that enough light in a small enough volume could create a black hole.

What is the good quantity that can tell when light can or cannot make a black hole? Energy density? But there must be some importance of the time it stays in that volume (pulse duration?). So is it irradiance?

How much of it is required to form a black hole? I expect there must be some kind of threshold after which a black hole must be formed.

Imagine you try to concentrate light gradually in a smaller and smaller volume. Is there any known mechanism that will necessarily prevent black hole formation during this phase ? I suspect photon-photon interaction might cause losses that cannot be overcome in any way.

EDIT: This question is not the same as that one, which only asked whether radiation can curve space. Here, I ask how much light can create a black hole, which is not the same question, I believe.

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  • $\begingroup$ Why has it been closed? I did not ask IF light can form a black hole, but how much of our is needed. I did not see an answer to that. $\endgroup$
    – fffred
    Commented Feb 11, 2016 at 18:39
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    $\begingroup$ I'm interested in knowing what you think an answer would look like. I mean, black holes form because the requisite energy is packed into a small enough space (where there is a functional relationship between the volume and the necessary energy density) and that's true whatever you make them out of. But see the papers in Willie Wong's answer to the proposed duplicate and this link in twistor's answer. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Feb 18, 2016 at 15:26
  • $\begingroup$ I'm currently unable to view arxiv's papers right now. The website seems to be down. Anyways, I'm looking forward to three answers, corresponding to my three questions: whether the energy density or the irradiance is the right quantity; what is the formula that describes the threshold on that quantity (after the threshold, a black hole must be formed); which mechanisms are expected to prevent this effect. I'm not sure why my questions seem unclear, but for me they are straightforward to understand. Maybe the title was too basic? I'm not sure how to make it more complete. $\endgroup$
    – fffred
    Commented Feb 18, 2016 at 16:09
  • $\begingroup$ I had a look to the papers pointed out in the answer you refer to. They are very technical, and it would take years for me to understand then. I still cannot see how the questions are really answered in the so-called duplicate anyways: it only says that yes, black holes can be formed by radiation, which is not my question. In addition, the other link you provided does not seem to consider interactions to find an energy density limit: I specified interactions in my question. What more could I say to convince you that this is not a duplicate? $\endgroup$
    – fffred
    Commented Feb 22, 2016 at 22:36
  • $\begingroup$ I curious as to how light can form a black hole? Or how light can be condensed. $\endgroup$
    – Bill Alsept
    Commented Feb 23, 2016 at 9:50

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