"Greg Egan - Schild's Ladder" - читать интересную книгу автора (Egan Greg)

their own intentional signals. By choice, they all looked politely interested, but were giving nothing away.

"You have a lot of confidence in QGT?" Clearly, Livia did realize just how strange her questions
sounded; her tone was that of someone begging to be indulged until her purpose became apparent.

Cass said, "Yes, I do. It's simple, it's elegant, and it's consistent with all observations to date." That
handful of words sounded glib, but other people had quantified all of these criteria long ago. QGT as a
description of the dynamics of the universe with the minimum possible algorithmic complexity. QGT as a
topological redescription of some basic results in category theory--a mathematical setting in which the
Sarumpaet rules appeared as natural and inevitable as the rules of arithmetic. QGT as the most probable
underlying system of physical laws, given any substantial database of experimental results that spanned
both nuclear physics and cosmology.

Darsono leaned toward her and interjected, "But why, in your heart"--he thumped his chest with an
imaginary fist--"are you convinced that it's true?" Cass smiled. That was not a gesture in the staid
vocabulary her Mediator used by default; Darsono must have requested it explicitly.

"In part, it's the history," she admitted, relaxing slightly. "The lineage of the ideas. If some alien civilization
had handed us Quantum Graph Theory on a stone tablet--out of the blue, in the eighteenth or nineteenth
century--I might not feel the same way about it. But general relativity and quantum mechanics were
among the most beautiful things the ancients created, and they're still the best practical approximations we
have for most of the universe. QGT is their union. If general relativity is so close to the truth that only the
tiniest fragment can be missing, and quantum mechanics is the same...how much freedom can there be to
encompass all of the successes of both, and still be wrong?"

Kusnanto Sarumpaet had lived on Earth at the turn of the third millennium, when a group of physicists
and mathematicians scattered across the planet--now known universally as the Sultans of Spin--had
produced the first viable offspring of general relativity and quantum mechanics. To merge the two
descriptions of nature, you needed to replace the precise, unequivocal geometry of classical space-time
with a quantum state that assigned amplitudes to a whole range of possible geometries. One way to do
this was to imagine carrying a particle such as an electron around a loop, and computing the amplitude for
its direction of spin being the same at the end of the journey as when it first set out. In flat space, the spins
would always agree, but in curved space the result would depend on the detailed geometry of the region
through which the particle had traveled. Generalizing this idea, crisscrossing space with a whole network
of paths taken by particles of various spins, and comparing them all at the junctions where they met, led
to the notion of a spin network. Like the harmonics of a wave, these networks comprised a set of
building blocks from which all quantum states of geometry could be constructed.

Sarumpaet's quantum graphs were the children of spin networks, moving one step further away from
general relativity by taking their own parents' best qualities at face value. They abandoned the idea of any
preexisting space in which the network could be embedded, and defined everything--space, time,
geometry, and matter--entirely on their own terms. Particles were loops of altered valence woven into the
graph. The area of any surface was due to the number of edges of the graph that pierced it, the volume of
any region to the number of nodes it contained. And every measure of time, from planetary orbits to the
vibrations of nuclei, could ultimately be rephrased as a count of the changes between the graphs
describing space at two different moments.

Sarumpaet had struggled for decades to breathe life into this vision, by finding the correct laws that
governed the probability of any one graph evolving into another. In the end, he'd been blessed by a lack
of choices; there had only been one set of rules that could make everything work. The two grandparents