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History 181B: Modern Physics
Class 29 (4/4/03)
Particles and nuclei
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| Navigation |
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| Outline |
QFTs and what they are good for (continued)
"Second" quantization and fields without classical
counterparts
Quantum electrodynamics: Dirac, Heisenberg-Pauli,
Fermi
Recovering Maxwellian electrodynamics
Reconstructing force as
exchange of particles
QED as a model for other QFTs
The cloud on the horizon: QED's infinities, and
its expected breakdown
Discovering new particles: The birth of particle physics
Experimental technologies: Making things "visible"
New particles of the 1930s
The physics of nuclei
The initial model: Protons plus electrons
And the problems it raised for quantum mechanics
The neutron, and Heisenberg's quantum mechanical
nucleus
Fermi's quantum field theoretic nucleus |
| Names
and terms |
| Primary |
Secondary |
quantum electrodynamics (QED)
Enrico Fermi (1901-1954), NP 1938
vacuum polarization
effective charge
fine structure constant alpha = e² / h-bar c
cloud chamber
electronic detectors
cosmic rays
Carl Anderson (1905-1991), NP 1936
Hideki Yukawa (1907-1981), NP 1949
James Chadwick (1901-1954), NP 1935
mass number A, atomic number Z
neutrino (nu)
Fermi interaction (beta decay)
Fermi-field theory of nuclear forces |
meson (pion) vs. muon |
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| Assignment |
Laurie M. Brown and Lillian Hoddeson, "The Birth
of Elementary-Particle Physics," Physics Today 35:4 (1982): 36-43.
This is dense reading. Ignore the details (unless
they interest you). Focus on understanding the headings (not necessarily
even the bullet points) in the boxes on p. 39 (experiment) and p. 42 (theory).
To do this, you will need to read the text, but let the boxes be your guide
to what's important.
What is quantum electrodynamics (QED)?
For what reasons did physicists in the 1930s expect
their theories would break down? Take either the "red" and "green" electrons
or the infinities of QED.
What did it take to get physicists to accept new
particles? |
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Copyright © Cathryn Carson 2003 |