Recent content by Tomas Vencl

  1. T

    I An invariant while crossing the horizon

    Yes, thank you all. The infalling observer’s proper time (\tau_1) is ultimately not important. What matters is that all observers agree that at the moment the infalling observer crosses the horizon, the black hole had mass m_1 from his point of view. We take this mass to be computed by the...
  2. T

    I An invariant while crossing the horizon

    Yes, that exactly is the point of the question.
  3. T

    I An invariant while crossing the horizon

    While reading the neighboring thread I came up with the following question: consider an evaporating black hole and an observer falling into it. The observer crosses the horizon at a finite proper time \tau_1; at the moment of horizon crossing the black hole has mass m_1 from the infalling...
  4. T

    B How can a black hole absorb matter?

    As JimWhoKnew has already noted: In other words, this scenario assumes that the photons emitted from the shell itself during the collapse are not affected by the mass of the shell, but only by the mass of the original black hole, which I think is quite an unphysical assumption.
  5. T

    I Black hole and coordinate time from the perspective of Alice outside

    I’m not sure whether this definition of reality is physically useful. It is fulfilled by every event in a block universe, and I can’t imagine a physical process that wouldn’t qualify as reality in this sense.
  6. T

    A Spacetime model of evaporating black hole

    Would it be possible to draw diagrams of the more realistic models considered by both of you? Thank you.
  7. T

    A Spacetime model of evaporating black hole

    Maybe I am mising something important. Imagine green observer with its proper time. You say that mass of bh decreases to zero between points (and greens times) 1 and 2 ? Then, how he can see some photons at point 3 eventually emmited from collapsing surface ? Or he cant ?
  8. T

    B Questions about space and matter

    I think that solving this guestion honestly is behind relativity framework, and needs deeper quantum gravity theory. For example: https://en.wikipedia.org/wiki/Causal_dynamical_triangulation
  9. T

    I Evaporating black hole: First principles consideration

    Here is first principles consideration: Since it is a black hole there is an event horizon where timelike worldlines can enter but not exit, this is what defines a black hole instead of a white hole. When evaporation is finished there is no more event horizon, this is what defines the...
  10. T

    B Falling into a black hole

    Yes,you are right. I am leaving the discussion for now. Thank you and Dale for your ttime.
  11. T

    B Falling into a black hole

    OK, perhaps it would be fair to also inform the inquirer that the assumptions may not be realistic (which I clumsily tried without any successs to do in my second comment).
  12. T

    B Falling into a black hole

    Sure, but you are not sure (since we do not have exact metric) that your assumptions (event horizon + evaporation) are even together physically possible . So this could be similar like counting of number of angels on tip of the needle. I can imagine that in case of evaporation instead of real...
  13. T

    B Falling into a black hole

    I do not think so, my claim: was reaction on this comment: I think that my claim can be rephrased for example that there is no horizon to cross (so there is no finite time to cross it, obviously), or, as another example, in some models with firewall also falling observer do not cross the...
  14. T

    B Falling into a black hole

    May be, but fact is that exact metric for evaporating “black hole” is unknown, so claiming that “in an evaporating spacetime it does not take an infinite amount of coordinate time to cross the horizon in Schwarzschild-like coordinates” is at least based on aproximations and rather speculative.
Back
Top