# Index

Q

see Robinson arithmetic

q-hypergeometric functions

in hard hexagon problem, 1133

q-numbers

as generalizing numbers, 1168

QCD (quantum chromodynamics), 1057, 1061

and computational irreducibility, 1133

and experience of models in, 991

as simple physical model, 1025

QED

see Quantum electrodynamics

QSPR (quantitative structure-property relations), 1195

Quadratic congruential generators, 975

Quadratic Diophantine equations, 944

NP completeness of, 1146

Quadratic equations

as exactly soluble, 1133

Quadratic forms

and Diophantine equations, 1164

Quadratic functions

in Turing machines, 1144

Quadratic irrationals

and constructible reals, 1129

and continued fraction map, 955

and Penrose tilings, 932

and spectra, 1081

see also Sqrt (square root)

Quadratic maps, 921

and history of chaos, 971

Quadratic primes conjecture

as unsolved problem, 1166

Quadratic programming

and circle packings, 986

Quadratic residue sequences, 1090

in acoustic diffusers, 1183

and flat spectra, 1081

NP completeness in, 1145

Quadratures

as exact solutions, 1133

Quadrics

fit to curved surfaces, 1049

Quality factor

in image compression, 573

Quantifier elimination

and commutative groups, 1160

and real algebra, 1154

Quantifiers

higher-order, 1167

in predicate logic, 1151

in well-formed formulas, 1150

Quantitative traits, 1003

Quantization

and discreteness of networks, 528

of volume in spin networks, 1055

Quantized vortices

in neutron stars, 1188

Quantum chaos, 1056

and decoherence, 1064

Quantum chromodynamics

see QCD

Quantum computers, 1147

and NP completeness of factoring, 1090

and quantum history, 1058

vs. Turing machines, 771

Quantum cryptography, 1058

Quantum-dot cellular automata, 1193

Quantum electrodynamics (QED)

as analogy for quantum gravity, 1054

effective coupling in, 1062

Feynman diagrams in, 1060

history of, 1056

Monte Carlo methods in, 1192

and point electrons, 1044

Quantum field theory, 1061

and computational irreducibility, 1133

difficulty of computations in, 1146

and discrete space, 1027

and energy conditions, 1053

and gravity, 1054

and knot theory, 1046

measurement in, 1065

and origins of mass, 1046

particles in, 540

planar diagrams in, 1040

and quantum computers, 1148

and quantum measurement, 1064

and random networks, 1038

simple effective theories in, 1026

and space as background, 1028

and ultimate theory of physics, 1025

and uniform spectra, 988

vacuum fluctuations in, 1062

Quantum fluctuations

and noise, 969

Quantum gravity, 1054

and discrete space, 1027

and Hawking radiation, 1062

history of, 1025

path integrals in, 1057

as source of decoherence, 1063

and space vs. contents, 1028

and spin networks, 1055

undecidability in models of, 1138

Quantum groups

and spin networks, 1055

Quantum information theory, 1058

Quantum measurement, 542, 1062

vs. computational irreducibility, 1135

and multiway systems, 1036

Quantum mechanics, 537-545

and atomism, 876

Brillouin zones in, 988

and character of programs, 538

and Church's Thesis, 1126

discretization of, 1059

and existence of formulas, 1132

and free will, 752, 1135

and gauge invariance, 1045

history of, 1056

and history of randomness, 967

and history of statistics, 1082

and mechanistic explanations, 860

and new types of perception, 1106

and NP completeness, 771

and origins of Second Law, 1020

and PDEs, 923

on Pioneer 10 plaque, 1190

and randomness, 303, 539, 970

search for defining features of, 1059

in ultimate theory of physics, 469

and use of abstract models, 1026

and wave-particle duality, 1044

Quantum numbers

and network tangles, 527

Quantum potential, 1065

Quarantine of astronauts, 1180

Quark confinement

and computational irreducibility, 1133

Quarks

confinement of, 1061

as example of model, 992

masses of, 1046

and particle history, 1025

and QCD, 1057

as types of particle, 1043

Quartic equations

and computational reducibility, 1132

as exactly soluble, 1133

size of solutions to, 945

Quartz

hopper crystals in, 993

Quasars

and SETI, 1189

Quasi-Monte Carlo methods

and digit reversal, 905

as randomness application, 1192

and statistical tests, 1085

Quasicrystals, 994

diffraction patterns in, 1082

spectra in, 1080

Quasiperfect numbers, 911

Quasiperiodicity

in combinations of sines, 146

and turbulence, 998

Quaternions

and abstraction in math, 792

cellular automata based on, 886

as generalizing numbers, 1168

as non-commutative rings, 1153

Qubits (in quantum systems), 1147

Queen Anne's Lace, 1006

Quicksort algorithm, 1142, 1142'

Quincunx board

randomness in, 312

Quine-McCluskey procedure, 1095

Quintic equations, 945

as exactly soluble, 1133

numbers defined by, 916

solving as impossibility, 1137

unsolvability of, 1132

Quotient

basic example of, 854

and computational reducibility, 747

encoded as integer equation, 1160

Qur'an

calligraphy from, 874