string theory, quantum mechanics and relativity dr. david berman lecturer department of physics...
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String Theory, Quantum String Theory, Quantum Mechanics and RelativityMechanics and Relativity
Dr. David BermanLecturer
Department of PhysicsQueen Mary CollegeUniversity of London
1. Theoretical Physicsthe search for unity
2. RelativityEinstein’s great theory of gravitation
3. Quantum Mechanicsthe failure of the ‘classical’
4. Unification needs String TheoryString Theory
5. More about stringsthe exciting way strings changes our view of the universe
History• Newton (1687):
Unified GravityThe same force that pulls you is also pulling
the moon and all the planets
Unity: A single explanation for many different things
Picasso:
“A painter should work with as few elements as possible.”
So should physicists!
Faraday & Maxwell (1873):
Unified Electricity, Magnetism and motion
Dynamo; Motor; Light Bulb…
Weinberg & Salam (1979):
Unified Electromagnetism and Nuclear Force
• This is the same for matter(the stuff we are made from)
• The building blocks were found to be smaller and smaller
1mman
10-9m0.000000001mmolecule
10-10m0.0000000001matom
10-14mnucleus
10-18mquark
When do we stop?
How many different ‘elementary’ particles are there?
The basic building blocks known today:
• 18 Quarks – make up protons and neutrons
• 6 Leptons – things like electrons
• 3 Types of Force –
Quite good, but we can do better!
Gravity‘Electroweak nuclear’Strong Nuclear
• String: The different ways a string can vibrate look like different particles to us.
Just like a violin string produces manydifferent notes.
Quantum Mechanics
Things on ‘small’ scales fluctuate randomly
Size matters in physics!
The smaller scales you go the more random and non-intuitive things get.
Can we unify gravity & quantum mechanics?
• Spacetime itself must now fluctuate at small scales
• Big problem:The smaller you go, the more it fluctuates
For example:• Examine a landscape by rolling balls over
the surface.
The detail/resolution will depend on the size of the ball. To get perfect resolution, you need a perfectly small ball.
Why 10 dimensions?
• In 10 (and only 10) dimensions is the theory consistent.
The remarkable price for unity!
Questions• How does geometry change when there
are no points?• What are the effects on the physics in the
world we see from the hidden dimensions?• Why stop at strings? What about
membranes as fundamental building blocks?
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