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Dr Sanjaye Ramgoolam

From Force & Matter to Strings. Dr Sanjaye Ramgoolam. In collaboration with. J. Bedford and C. Papageorgakis. STRING THEORY arises from attempts to answer:. 1) What is the world made of? 2) How & Why does the world change in time?. Answers:. 1) MATTER!

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Dr Sanjaye Ramgoolam

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  1. From Force & Matter to Strings Dr Sanjaye Ramgoolam In collaboration with J. Bedford and C. Papageorgakis

  2. STRING THEORY arises from attempts to answer: 1) What is the world made of? 2) How & Why does the world change in time? Answers: 1) MATTER! E.g. Cars, Houses, Buildings, Planets… All matter has Mass

  3. 2) Forms of matter exert Forces on each other and they move under the influence of these forces For example: the attraction which causes an apple to fall off a tree.

  4. So far: 2 Questions 2 Answers MATTER ; FORCE

  5. Matter comes in millions of different forms: Apples, Oranges… Cars - Hondas BMWs... Garden Hoses, Grass, Trees... Earth, Sun, Moon… Galaxies, Planets, Stars... All this diversity in fact comes from only a few hundred atoms: Hydrogen, Oxygen, Nitrogen... • Each atom has a definite mass. • Each atom has an approximate size of about:

  6. By going from the large to the tiny, we reduce • the diversity of millions to around a hundred! • Things simplify further if we look • deeper into the atom: + Protons: Neutrons: Electrons: - Electrons orbit the nucleus which is composed of Protons and Neutrons

  7. The few hundred atoms reduce to only a • handful of fundamental objects • Our Millions of Matter objects have • been reduced to just 3 - Great! Unfortunately, the story starts to get more complicated: Proton & Neutron Quarks Colours red up down strange charm bottom top green + blue

  8. There are 3 ‘generations’ of these quarks • & each quark can have one of 3 different • ‘colours’ • Likewise there are 3 ‘generations’ of • electron-like objects called leptons: Leptons electron electron-neutrino muon muon-neutrino tau tau-neutrino

  9. The idea of String Theory is that this diversity of quarks and leptons comes from 1 String H O e p n e   u d s c t b 1 String

  10. What about Forces? “Hammer Force” “Fuel Force” “Astronomical Force” All this diversity of forces comes from: Gravity & Electromagnetism (& its 2 cousins)

  11. The Electric Force: • Rub a pen against your sleeve • & pick up pieces of paper. • Rubbing - Separation of charge. Matter contains positive & negative charges: Repulsion + + Repulsion - - Attraction + -

  12. On a grander scale: Lightning is caused by the Electric Force

  13. The connection between Light & Charge runs deep: Particle physics teaches us that “electrons repel because of the exchange of particles of light called photons” Exchange Repulsive force

  14. Particle physics reduces both Matter & Force to one kind of Entity i.e. particles. electrons Matter protons photons Forces gravitons Force of Gravity

  15. The Physics of particles is governed by “Quantum Mechanics” • Which brings about a Radical • Change in our concepts of • space. E.g. Cannot say electron is here and going nowhere. Every position is assigned a number telling us how likely the electron is to be at that point. x

  16. Quantum mechanical analogue of particle is here: The particle has maximum chances of being here and electrons in definite orbits is replaced by High chance of finding electron Small chance

  17. Deep inside proton: In addition to Electricity/Magnetism we need to know about Strong & Weak force. The mediators of strong forces are gluons. Quantum theory & particle physics do a great job of reducing diversity of matter & Electromagnetism, S & W forces to a few particles!

  18. Forces E.M. Strong Weak photons & gluons γ,g But gravity does not fit nicely into the Quantum Mechanical world. Applying Q.M. to gravitation gives infinities.

  19. String Theory combines all forces Strong,Weak, Gravitation, Electromagnetism & all matter electrons,protons,neutrons… into one object… …a String! Matter Force e-, p+, n γ, gluon, graviton

  20. How does a string accomplish this? • All particles have energy. In classical physics: I. also Rest energy ; II. Photons have frequency (related to colour of light) Planck’s constant

  21. Strings can vibrate in different ways For example: Guitar string Different vibration Different sound! • Fundamental string Different vibration Different particles! electron photon graviton

  22. In ordinary circumstances, we can understand • the world by applying different forces • according to the problem at hand. • A unified Theory of matter & forces is not just pretty - it is necessary for us to understand: • Physics of the Early Universe • Black Holes E.g. • Universe is expanding • Every galaxy is facing away from every other

  23. Going back in time, • All matter was crunched up in a very energetic state within a short distance. • Under these conditions all forces were equally important. • Hence String Theory becomes necessary for us to understand what happened at after the Big Bang.

  24. And it makes a startling prediction: The world contains… …Extra Dimensions!

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