1. Avinash Singh and Bhowar GuptaKalinga Institute Of Industrial TechnologyBhubaneshwar,OrissaEinstein: A Century of RelativityIISC KolkataMarch 5, 2011

2. What is String Theory?29 January 2005 Einstein: A Century of Relativity Feng 2 3. Outline String Theory A Theory looking for observations. The D-Brane revolution. What is the String Scale? Inflation Cosmic initial conditions and fluctuations. Phenomenology looking for a theory. Inflation in String Theory? Braneless attempts. Brane Inflation? OutlookStrings and Inflation 3 4. smallClassical Physics (1687) heavyfastQuantum Mechanics (1905)Special Relativity (1905)General Relativity (1915)Quantum Field Theory (1940s)? String Theory ?29 January 2005Einstein: A Century of RelativityFeng 4 5. In String Theory, Particles are StringsDifferent Vibrations String Combinations Different Particles Particle Interactions updown electronquarkquark String theory realizes Einsteins dream of a unified theory 29 January 2005 Einstein: A Century of RelativityFeng 5 6. Extra Dimensions (x, y, z, t) + w, v,? Science fiction? No a major topic in science today:What is our world made of?How does gravity work? How did this happen?29 January 2005Einstein: A Century of Relativity Feng 6 7. Extra Dimensions Suppose our world is only a slice of the whole universe29 January 2005Einstein: A Century of RelativityFeng 7 8. Structure of Extra Dimensions The properties of the internal spacedetermine the low energy data, such as thespectrum of particles and their interactions. 9. String dualitiesStrings are very useful objects to consider at weak couplingWe like strings because they can deal with graviton exchangeE. WittenDegrees of freedom can change; e.g. consider water and iceSomething similar happens in string theory; at strong coupling dreamA new (weakly coupled) degrees of freedom can be used in an come true! approximate descriptionThis phenomenon is generally called a duality Particle/wave duality Strong/weak coupling duality (electric/magnetic)12/15/01Saturday Morning Physics 9 10. Standard Model of Particle Physics:The Modern Theory of Matter 29 January 2005 Einstein: A Century of Relativity Feng 11 11. Elementary Particles and Interactions 29 January 2005 Einstein: A Century of Relativity Feng 12 12. Albert Einsten1915: Spacetime is an active player: curves, expands, shrinks, 29 January 2005Einstein: A Century of Relativity Feng 13 13. The Big BangThe universe does not expand into space space itself expandsExtrapolating back, space was small the Big Bang Other dimensions could exist but still be small. Stringtheory requires 6 extra dimensions. How can we test this possibility?29 January 2005Einstein: A Century of Relativity Feng 14 14. Small Dimensions Suppose all particles propagate in extradimensions, but these are curled up in circles. We will not notice them if the circles are very small.Garden hose29 January 2005 Einstein: A Century of Relativity Feng 15 15. A lot of dark matter isrequired to holdgalaxies together It cannot all be made ofknown particles It must be some newform of matter maybea sign of extradimensions!29 January 2005 Einstein: A Century of Relativity Feng 16 16. Dark Matter at CollidersLarge Hadron Collider at CERN, Geneva 29 January 2005Einstein: A Century of Relativity Feng 17 17. Strong Gravity and Black Holes29 January 2005 Einstein: A Century of Relativity Feng 18 18. Gravity Gravity is the least understood force. Many deep problems, but one obvious one:Gravity is extraordinarilyweak. It is important ineveryday life onlybecause it is alwaysattractive. 29 January 2005 Einstein: A Century of Relativity Feng 19 19. Strong Gravity In this case, gravity may be strong but appearweak only because its strength is diluted byextra dimensions. Fgravity ~ 1/r 2+n for small lengths, where n isthe number of extra dimensions. Can this betrue?29 January 2005Einstein: A Century of Relativity Feng 20 20. What is M- theory? Membrane, Mystery, M other, Magic, Membranes Eleven dimensionsString theoryP-branes P.K. Townsend: Pea brain democracy!12/15/01Saturday Morning Physics 21 21. 7 + 7 TeV proton proton collider 22. ...and a classic ending. Strings and Inflation 24