These are excerpts and elaborations from my book "The Nature of Consciousness"
Of Symmetry and Asymmetry: Parity
Of Symmetry and Asymmetry: Gauge Theory
Unification: In Search of Symmetry Since the
electric charge also varies with flavor, it can be considered a flavor force as
well. Along these lines, Steven Weinberg and Abdus Salam (“A Model of
Leptons”, 1967) unified the weak and the
electromagnetic forces into one flavor force, and discovered a third flavor
force, mediated by the Z quanta. The unified flavor force therefore admits four
quanta: the photon, the W- boson, the W+ boson and the Z boson. These quanta
behave like the duals of gluons: they are sensitive to flavor, not to color.
All quanta are described by the so called "Yang-Mills field", which
is a generalization of the Maxwell field (Maxwell's theory becomes a particular case of Quantum
Flavor Dynamics: "Quantum Electrodynamics"). Note that the equations
of the Yang-Mills field were discovered by Chen Ning Yang and Robert Mills way before anyone even conceived of gluons ("Conservation of
Isotopic Spin and Isotopic Gauge Invariance”, 1954). They were just a
mathematical generalization: Maxwell’s equations assume that there is only one
kind of charge (the electric one), whereas the Yang-Mills equations allow for
many. The symmetry of
the electroweak force (whereby the photon and the bosons get transformed among
themselves) is not exact as in the case of Relativity (where time and space
coordinates transform each other): the photon is mass-less, whereas bosons have
mass. Only at extremely high temperatures the symmetry is exact. At lower
temperatures a spontaneous breakdown of symmetry occurs. This seems to be
a general caprice of nature. At different temperatures symmetry breaks down:
ferromagnetism, isotropic liquids, the electroweak force... A change in
temperature can create new properties for matter: it creates magnetism for metals,
it creates orientation for a crystal, it creates masses for bosons. The fundamental
forces exhibit striking similarities when their bosons are mass-less. The three families of particles, in
particular, acquire identical properties. This led scientists to believe that
the “natural” way of being for bosons in a remote past was mass-less. How did
they acquire the mass we observe today in our world? And why do they all have
different masses? The Higgs mechanism gives fermions and bosons a mass. Naturally it requires bosons of its own, the
Higgs bosons (particles of spin 0). Each interaction
exhibits a form of symmetry, but unfortunately they are all different, as
exemplified by the fact that quarks cannot turn into leptons. In the case of
the weak force, particles (e.g., the electron and its neutrino) can be
interchanged, while leaving the overall equations unchanged, according to a
transformation called SU(2), meaning that one particle can be exchanged for
another one. For the strong force (i.e., the quarks) the symmetrical
transformation is SU(3), meaning that three particles can be shuffled around.
For the electromagnetic force, it is U(1), meaning that only the electrical and
magnetic component of the field can be exchanged for each other. Any attempt to
find a symmetry of a higher order results into the creation of new particles.
SU(5), for example (proposed by Howard Georgi and Sheldon Glashow in 1974), entails the existence of 24 bosons... but it does allow
quarks and leptons to mutate into each other (five at the time), albeit at
terribly high temperatures. Back to the beginning of the chapter "The New Physics" | Back to the index of all chapters |
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