The unification of fundamental forces of nature into a single force occupied Einstein attention for much of his later life. Today thousand of physicist, on the cutting edge of physics is still trying to solve it. Albert Einstein spent his last two decades and during his last hr. he was trying to unify all the theories and laws of universe into a single theory so powerful that can describe all the laws and theories of the universe but Einstein ran out of time unfulfilling his dream, now almost a half century later his dream has become the holy grail of the modern physics we may achieve Einstein dream with a new and radical set of ideas called string theory but if this revolutionary theory is right we are in real quite a shock, String Theory says we may be living in a world where reality meets science fiction, a universe of eleven dimension with parallel universes right next to us i.e.an elegant universe composed entirely of the music of strings, but what would be if we combine Einstein general theory of relatively,Newtonian Mechanics Maxwellian Electromagnetism and quantum mechanics to produce a theory that can explain the cosmic background radiation then it would be really a blockbuster in the history of science. . I have seen that the weak force has ben successfully combined with electromagnetism so that they may be jointly viewed as aspects of a single electroweak force . theories that attempts to add the strong force to this combination-called grand unification theories (GUT) – are being persuade actively . This could be a theory that would seeks to complete the job by adding gravity – sometimes called theories of everything (TOE) .

1. Avinash Singh and Bhowar Gupta
Kalinga Institute Of Industrial Technology
Bhubaneshwar,Orissa
Einstein: A Century of Relativity
IISC Kolkata
March 5, 2011

2. What is String Theory?
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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?
 Outlook
Strings and Inflation 3

4. small Classical Physics (1687) heavy
fast
Quantum Mechanics (1905) Special Relativity (1905) General Relativity (1915)
Quantum Field Theory (1940’s) ?
String Theory ?
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5. In String Theory, Particles are Strings
Different Vibrations  String Combinations 
Different Particles Particle Interactions
up down
electron
quark quark
String theory realizes Einstein’s dream of a unified theory
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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?
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7. Extra Dimensions
 Suppose our world is only a slice of the whole universe
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8. Structure of Extra Dimensions
 The properties of the internal space
determine the low energy data, such as the
spectrum of particles and their interactions.

9. String dualities
 Strings are very useful objects to consider at weak coupling
 We like strings because they can deal with graviton exchange E. Witten
 Degrees of freedom can change; e.g. consider water and ice
 Something similar happens in string theory; at strong coupling dream
A
new (weakly coupled) degrees of freedom can be used in an come true!
approximate description
 This phenomenon is generally called a duality
 Particle/wave duality
 Strong/weak coupling duality (electric/magnetic)
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11. Standard Model of Particle Physics:
The Modern Theory of Matter
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12. Elementary Particles and Interactions
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13. Albert Einsten
1915: Spacetime is an active player:
curves, expands, shrinks, …
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14. The Big Bang
 The universe does not
expand into space –
space itself expands
 Extrapolating back, space
was small – the Big Bang
• Other dimensions could exist but still be small. String
theory requires 6 extra dimensions.
• How can we test this possibility?
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15. Small Dimensions
 Suppose all particles propagate in extra
dimensions, but these are curled up in circles.
 We will not notice them if the circles are very small.
Garden hose
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16.  A lot of dark matter is
required to hold
galaxies together
 It cannot all be made of
known particles
 It must be some new
form of matter – maybe
a sign of extra
dimensions!
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17. Dark Matter at Colliders
Large Hadron Collider at CERN, Geneva
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18. Strong Gravity and Black Holes
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19. Gravity
 Gravity is the least understood force.
 Many deep problems, but one obvious one:
Gravity is extraordinarily
weak. It is important in
everyday life only
because it is always
attractive.
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20. Strong Gravity
 In this case, gravity may be strong but appear
weak only because its strength is diluted by
extra dimensions.
 Fgravity ~ 1/r 2+n for small lengths, where n is
the number of extra dimensions. Can this be
true?
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21. What is M-
theory?
 Membrane, Mystery, M
other, Magic, …
Membranes
Eleven dimensions
String theory
P-branes
P.K. Townsend: “Pea brain democracy!”
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23. 7 + 7 TeV proton – proton collider

24. ….…..and a classic ending.
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