What is apparent horizon?

Apparent Horizon

In general relativity, an apparent horizon is a surface that is the boundary between light rays that are directed outwards and moving outwards, and those directed outwards but moving inwards.

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Some articles on apparent horizon:

Apparent Horizon - Differences From The (Absolute) Event Horizon
... In the context of black holes, the term event horizon refers almost exclusively to the notion of the absolute horizon ... Much confusion seems to arise concerning the differences between an apparent horizon (AH) and an event horizon (EH) ... the EH and the AH generally do not coincide as long as either horizon fluctuates ...
Event Horizon - Apparent Horizon of An Accelerated Particle
... Under these conditions, an apparent horizon is present in the particle's (accelerating) reference frame, representing a boundary beyond which events are unobservable ... appears to be a boundary behind it from which no signals can escape (an apparent horizon) ... accelerators, for example), a true event horizon is never present, as the particle must be accelerated indefinitely (requiring arbitrarily large ...

Famous quotes containing the words horizon and/or apparent:

    The bird is lost,
    Dead, with all the music:
    While sunsets heard the brain’s music
    Faded to last horizon notes.
    Owen Dodson (b. 1914)

    I am from time to time congratulating myself on my general want of success as a lecturer; apparent want of success, but is it not a real triumph? I do my work clean as I go along, and they will not be likely to want me anywhere again. So there is no danger of my repeating myself, and getting to a barrel of sermons, which you must upset, and begin again with.
    Henry David Thoreau (1817–1862)