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String Theory, Quantum Mechanics and Relativity

String Theory, Quantum Mechanics and Relativity. Dr. David Berman Lecturer Department of Physics Queen Mary College University of London. Theoretical Physics the search for unity Relativity Einstein’s great theory of gravitation Quantum Mechanics the failure of the ‘classical’

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String Theory, Quantum Mechanics and Relativity

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  1. String Theory, Quantum Mechanics and Relativity Dr. David BermanLecturerDepartment of PhysicsQueen Mary CollegeUniversity of London

  2. Theoretical Physicsthe search for unity • RelativityEinstein’s great theory of gravitation • Quantum Mechanicsthe failure of the ‘classical’ • Unification needs String Theory • More about stringsthe exciting way strings changes our view of the universe

  3. History • Newton (1687): Unified Gravity The same force that pulls you is also pullingthe moon and all the planets Unity: A single explanation for many different things

  4. Picasso: “A painter should work with as few elements as possible.” So should physicists!

  5. Faraday & Maxwell (1873): Unified Electricity, Magnetism and motion Dynamo; Motor; Light Bulb… Weinberg & Salam (1979): Unified Electromagnetism and Nuclear Force

  6. All the forces in nature appeared as different aspects/faces of a single force

  7. This is the same for matter(the stuff we are made from) • The building blocks were found to be smaller and smaller

  8. When do we stop? 1mman 10-9m0.000000001mmolecule 10-10m0.0000000001matom 10-14mnucleus How many different ‘elementary’ particles are there? 10-18mquark

  9. 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

  10. John Schwarz Michael Green

  11. Unity: One Single Building Block STRING THEORY

  12. String: The different ways a string can vibrate look like different particles to us. Just like a violin string produces many different notes.

  13. How long is a piece of string? ~10-34m Far away, the string looks like a point…

  14. Einstein playing the violin

  15. General Relativity Space & Time continued = spacetime Spacetime can bend Gravity

  16. 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.

  17. Can we unify gravity & quantum mechanics? • Spacetime itself must now fluctuate at small scales • Big problem: The smaller you go, the more it fluctuates

  18. String Theory provides a shortest distance i.e. String theory is pointless 10-34m

  19. 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.

  20. Other Consequences • We live in 10 dimensions 1 dimension 2 dimensions 3 dimensions

  21. Kaluza & Klein

  22. Kaluza & Klein: The other dimensions are curled up and too small to see.

  23. Why 10 dimensions? • In 10 (and only 10) dimensions is the theory consistent. The remarkable price for unity!

  24. 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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