Comments | koganbot: Conservation Of Information?

koganbot

Conservation Of Information?

Dec 28, 2012 09:48

Posting again on a subject I don't understand and never will: what physicists mean by "information." My brain balks at mathematical symbols, but I'm good at concepts; so my guess is that if some articulate physicist were to wander by, he or she could explain "conservation of information" in a way that doesn't totally leave me at sea. Wikipedia hasn ( Read more... )

language studies, ludwig wittgenstein, information, popular science and technology

Comments 19

Getting rid of Laplace's Demon koganbot December 28 2012, 16:53:27 UTC

A way to get rid of the need for a Laplace Demon or for the vacuous idea of "objective information":

Is there something equivalent to a holographic principle that literally gets me and my pen and my understandings into a post-black-hole future? Something that's an alternative but equivalent way of describing the universe? This would make the Laplace Demon unnecessary, since no one would need an interpreter to reconstruct me, my pen, and my understandings: we're already there, albeit as pixels.

The world of ordinary experience is a hologram koganbot December 28 2012, 16:58:15 UTC

A month ago I made it back to the library and copied these down from Susskind and from Carroll. Unfortunately there are gaps in my notes.

From Leonard Susskind's The Black Hole War, p. 298:

The three-dimensional world of ordinary experience - the universe filled with galaxies, stars, planets, houses, boulders, and people - is a hologram, an image of reality coded on a two-dimensional surface. This new law of physics, known as the Holographic Principle, asserts that everything inside a region of space can be described by bits of information restricted to the boundary.
On page 411, Susskind says that this boundary is "only an imaginary mathematical surface with no real substance." So anything can enter or leave. But we can think of something called "anti de Sitter space" in which the angles in triangles add up to less than 180 degrees. He describes it as like the reverse of a Mercator projection: anything close to the boundary gets smaller, infinitely small, without crossing the boundary. So in effect the boundary is impenetrable. " ( ... )

If Life Is A Can Of Soup, What Am I Doing On The Label? koganbot December 28 2012, 17:02:51 UTC

Susskind (pp 418-419) continues, describing an idea of Edward Witten's:

Anti de Sitter space... is like a can of soup. Horizontal slices through the can represent space; the vertical axis of the can is time. The label on the outside of the can is the boundary, and the interior is the space-time continuum itself.

...Witten explained that by injecting enough mass and energy into the can, a black hole could be created. That raised a question. According to Maldacena, there must be a second description - a dual description - that makes no reference to the inside of the can. The alternate description would be in terms of a two-dimensional Quantum Field Theory of particles similar to gluons that move on the label. The existence of a black hole in the soup must be equivalent to something in the boundary hologram, but what was that something? In the Boundary Theory, Witten argued that the black hole in the soup was equivalent to an ordinary hot fluid of elementary particles - basically just gluons.
If I'm understanding this, we're taking a ( ... )

The explicit mechanism remains unclear koganbot December 28 2012, 17:06:52 UTC

This is from Sean Carroll, From Eternity To Here, p. 283; what he's calling "four-dimensional" is what I was calling "3 + 1 dimensions" (three of space, one of time, no gravity) in the previous two comments:

So we make a black hole in anti-de Sitter space and then let it evaporate. Is information lost? Well, we can translate the question into an analogous situation in the four-dimensional theory. But that theory doesn't have gravity, and therefore obeys the rules of ordinary quantum mechanics. There is no way for information to be lost in the four-dimensional nongravitational theory, which is supposed to be completely equivalent to the five-dimensional theory with gravity. So, if we haven't missed some crucial subtlety, the information must somehow be preserved in the process of black hole evaporation ( ... )

Do pointers have a point? koganbot December 30 2012, 01:39:21 UTC

By the way, what I wrote in my post may incidentally give the false impression that I think that language is fundamentally about pointing, which isn't right. Some words can point, but not all words must point. You can have the words "Frank's apartment," and some equivalent in some other language (except I don't know any other language, but maybe "l'appartement de François" or "François appartement" might work in French); and we can point to my apartment as what the words are referring to, no matter which of the two expressions we use ( ... )