Information paradox Definition and 12 Discussions

The black hole information paradox is a puzzle resulting from the combination of quantum mechanics and general relativity. Calculations suggest that physical information could permanently disappear in a black hole, allowing many physical states to devolve into the same state. This is controversial because it violates a core precept of modern physics—that, in principle, the value of a wave function of a physical system at one point in time should determine its value at any other time. A fundamental postulate of the Copenhagen interpretation of quantum mechanics is that complete information about a system is encoded in its wave function up to when the wave function collapses. The evolution of the wave function is determined by a unitary operator, and unitarity implies that information is conserved in the quantum sense.
As of November 2019, the paradox may have been resolved, at least for simplified models of gravity. (also see § Recent developments)

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  1. S

    I Information lost at the Big Crunch?

    Let's imagine for a moment that the universe stopped expanding somehow (even though the evidence we have suggests this is not going to happen) and gravity made it contract until reaching a Big Crunch state. According to our actual understanding of physics and our current working models, Is it...
  2. nomadreid

    I Entangled particles in black hole decay?

    First, I was not sure whether this should go into the Relativity or the Quantum Physics rubric, but since the central question is about entanglement, I opted for the Quantum. I do not have the necessary sophistication to follow string theory arguments, and even most explanations in...
  3. J

    A What does the equation C = 12 J mean for black holes?

    Just saw a documentary about resolving Hawking's "information paradox". In my own lay terms the physicists appear to theorize resolving the paradox with with their proposed C = 12 J . C is the central charge (which I don't fully understand) and J is the total angular momentum of the black...
  4. avischiffman

    B How to shorten this speech about BH?

    Hi guys I am writing a speech for a school video and I have a maximum of 3 minutes, but I've written 4 minutes and 17 seconds worth of stuff. I need help cutting the fat away giving me around 2 minutes and 45 seconds worth of stuff so that I can have some quick experiments and speak slower so...
  5. K

    A A question about the information loss paradox

    In the information loss paradox, people say that in quantum mechanics , time evolution is unitary. They usually do not say anything about the measurement process of if they do, they briefly say that the measurement process does not violate unitarity either if one takes into account the...
  6. stevendaryl

    A Information Paradox for Unruh Radiation?

    I'm sure that there are limits to the analogy between the event horizon of black holes and the "Rindler horizon" for an accelerated observer, but there are a number of similarities: For Schwarzschild spacetime as described in Schwarzschild coordinates: Spacetime is static, and a rocket must...
  7. Will K

    B Black Holes and Information

    What happens to the information about the objects falling into the black hole? Are their states somehow contained in the Hawking Radiation, and if so, how? Or is the information scrambled as it passes the EH?
  8. O

    A Conservation of Information: Neutron Formation and Decay

    Has anyone analyzed the process of Neutron formation and decay from the perspective of "information conservation"? Does anyone have any thoughts on what the results of such an analysis would be? What is the status of the observed evidence of reality in respect of whether one should conclude...
  9. A

    What is the core problem of the information paradox?

    Can you please explain what the core problem of the information paradox is? Hi all! I've read many articles about it, watched videos, argued with some physicists, and yet I can't grasp at all where the paradox lies. For example, from the Wikipedia: "An important difference between the black...
  10. anorlunda

    Please Define Information

    Searches of PF archives for Information Conservation turn up many threads in which the question is more or less dismissed. It sounds like many PF regulars don't believe in it, as if it were fringe science or metaphysics. Contrast that with the prominence given to the recent thread Stephen...
  11. stevendaryl

    Connection between Einstein-Cartan and "Baby Universes"

    The Einstein-Cartan theory is, to my mind, a completely straightforward generalization of General Relativity, and indeed seems like a necessary generalization if we are to accommodate particles with intrinsic spin. (The mathematics for this claim is beyond me, but the layman's summary is this...
  12. Larry Pendarvis

    Is it possible to distinguish between pure and mixed states?

    Is it possible, in principle, for an experiment to distinguish between an ensemble of pure states and an ensemble of mixed states? If so, how? In particular, I am thinking of an ensemble of particles whose spin has been measured, one at a time, on the "Vertical" axis. The ensemble consists of...