Perhaps now that there are other physicists (besides myself) making
these claims, people in the AGI community will start to take more
seriously the implications for their own field ....
http://www.newscientist.com/article/mg20026764.100
For those who do not have a New Scientist subscription, the full article
refers to a paper at http://www.arxiv.org/abs/0809.0151.
Mile Gu et al looked at the possibility of explaining emergent
properties of Ising glasses and managed to prove that those properties
are not reducible.
Myself, I do not need the full force of Gu's proof, since I only claim
that emergent properties can be *practically* impossible to work with.
It is worth noting that his chosen target systems (Ising glasses) are
very closely linked to some approaches to AGI, since these have been
proposed by some neural net people as the fundamental core of their
approach.
I am sure that I can quote a short extract from the full NS article
without treading on the New Scientist copyright. It is illuminating
because what Gu et al refer to is the problem of calculating the lowest
energy state of the system, which approximately corresponds to the state
of maximum "understanding" in the class of systems that I am most
interested in:
BEGIN QUOTE:
Using the model, the team focused on whether the pattern that the atoms
adopt under various scenarios, such as a state of lowest energy, could
be calculated from knowledge of those forces. They found that in some
scenarios, the pattern of atoms could not be calculated from knowledge
of the forces - even given unlimited computing power. In mathematical
terms, the system is considered "formally undecidable".
"We were able to find a number of properties that were simply decoupled
from the fundamental interactions," says Gu. Even some really simple
properties of the model, such as the fraction of atoms oriented in one
direction, cannot be computed.
This result, says Gu, shows that some of the models scientists use to
simulate physical systems may actually have properties that cannot be
linked to the behaviour of their parts (www.arxiv.org/abs/0809.0151).
This, in turn, may help explain why our description of nature operates
at many levels, rather than working from just one. "A 'theory of
everything' might not explain all natural phenomena," says Gu. "Real
understanding may require further experiments and intuition at every level."
Some physicists think the work offers a promising scientific boost for
the delicate issue of emergence, which tends to get swamped with
philosophical arguments. John Barrow at the University of Cambridge
calls the results "really interesting", but thinks one element of the
proof needs further study. He points out that Gu and colleagues derived
their result by studying an infinite system, rather than one of large
but finite size, like most natural systems. "So it's not entirely clear
what their results mean for actual finite systems," says Barrow.
Gu agrees, but points out that this was not the team's goal. He also
argues that the idealised mathematical laws that scientists routinely
use to describe the world often refer to infinite systems. "Our results
suggest that some of these laws probably cannot be derived from first
principles," he says.
END QUOTE.
I particularly liked his choice of words when he said: "We were able to
find a number of properties that were simply decoupled from the
fundamental interactions..."
Now where have I heard that before, I wonder?
Richard Loosemore
-------------------------------------------
agi
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