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Eleven Dimensions
of the
Unifying Theory
Michael Duff
January 14 2009
Friends of Imperial College
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Two Pillars of XX Century Physics
• Quantum Mechanics: applies to the very small;
atoms, subatomic particles and the forces
between them.
• General Relativity: applies to the very large;
stars, galaxies and gravity, the driving force of
the cosmos as a whole.
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Central Quandary of XXI Century Physics
• Quantum mechanics and general relativity are
mutually incompatible!
• Microscopic scale: Einstein’s theory
fails to comply with the quantum rules
that govern the subatomic particles.
• Macroscopic scale: black holes are
threatening the very foundations of
quantum mechanics.
New scientific revolution? M- theory?
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When is a particle ``elementary’’?
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plus their antiparticles:
The building blocks : quarks and leptons
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Four fundamental forces
Plus the Higgs Boson to give mass
to the W, Z, quarks and leptons=
``The Standard Model’’
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The particle view of nature is a
description that works exceedingly
well to describe three of the four
observed forces of nature
The geometric view of nature
works very well for describing
gravity at astronomical distance scales
What exactly is a force?
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All-embracing theory?
If current ideas are correct, will require three
radical ingredients:
1) Extra dimensions
2) Supersymmetry
3) Extended objects (strings, branes..)
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Fifth dimension
• Kaluza and Klein imagined a small circle at each point of 4D
spacetime
D=4 perspective:
Einstein’s gravity PLUS Maxwell’s electromagnetism!
*
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Supersymmetry
1) Unifies bosons (force-carrying particles) with fermions
(building block particles)
2) I