The document discusses the history and development of theories attempting to unify the fundamental forces. It describes how electromagnetism was unified and the development of the electroweak theory. Efforts were made to include the strong nuclear force through grand unified theories, but requiring extremely high energies. String theory is now the leading approach to achieve a theory of everything by unifying gravity with other forces. Further experiments are still needed to fully test theories and achieve unification.

1. The String TheoryThe String Theory A Theory of EverythingA Theory of Everything

3. Warning
This journey may change your vision of the Universe.This journey may change your vision of the Universe.
What you will hear may alter your perception of reality.What you will hear may alter your perception of reality.
We are entering a Quantum World..
Stay awake and keep an open mind!

4.  Why do we need a single unified theoryWhy do we need a single unified theory
 What’s missing in the standard model?What’s missing in the standard model?
 Prescriptions of a unified theoryPrescriptions of a unified theory
 Gauge theoriesGauge theories
 Electroweak unificationElectroweak unification
 Grand unified theoryGrand unified theory
 Klein Kaluza theoryKlein Kaluza theory
 ConclusionConclusion
Why Do we need a single theory?

5. “Everyone’s goal is a theory of
everything, an economic,
simple theory that works at all
energies, at all scales, for all
time.”

6. Why Do we need a single theory?
 Because there is only One GodBecause there is only One God
 All the laws should be part of a single pattern.All the laws should be part of a single pattern.
 A single theory is more beautiful than many theoriesA single theory is more beautiful than many theories
 The early phases of the universe, only one UniversalThe early phases of the universe, only one Universal
force called Eventual Unity, is thought to have beenforce called Eventual Unity, is thought to have been
effective.effective.
 Like Behavior of Roulette Ball on a Roulette WheelLike Behavior of Roulette Ball on a Roulette Wheel
high energy rolls round & round but at low energyhigh energy rolls round & round but at low energy
drops in to any 37 slats. Low energy 37 states , highdrops in to any 37 slats. Low energy 37 states , high
energy only one state idea of unification at high energy.energy only one state idea of unification at high energy.

7. What is Grand Unified Theory?
Unified field theory is an attempt to
describe all fundamental forces and
the relationships between
elementary particles in terms of a
single theoretical framework.

8. Current Fundamental Forces
ElectromagneticElectromagnetic
Weak NuclearWeak Nuclear
Strong NuclearStrong Nuclear
GravityGravity

9. There are four fundamental forces,
or interactions in nature.
 Strong nuclearStrong nuclear
 ElectromagneticElectromagnetic
 Weak nuclearWeak nuclear
 GravitationalGravitational
Strongest
Weakest

10. Strong nuclear force
 Holds the nuclei of atoms togetherHolds the nuclei of atoms together
 Very strong, but only over very, very, veryVery strong, but only over very, very, very
short distances (within the nucleus of theshort distances (within the nucleus of the
atom) Responsible for Fission & Fusion.atom) Responsible for Fission & Fusion.

11. Electromagnetic force
 Causes electric and magnetic effectsCauses electric and magnetic effects
 Like charges repel each otherLike charges repel each other
 Opposite charges attract each otherOpposite charges attract each other
 Interactions between magnetsInteractions between magnets
 Weaker than the strong nuclear forceWeaker than the strong nuclear force
 Acts over a much longer distance rangeActs over a much longer distance range
than the strong nuclear force ,Also called asthan the strong nuclear force ,Also called as
(FORCE OF LIFE), Due to generating Bio(FORCE OF LIFE), Due to generating Bio
electrical currents in Human Body.electrical currents in Human Body.

12. Weak nuclear force
 Responsible for nuclear decayResponsible for nuclear decay
 Weak and has a very short distance rangeWeak and has a very short distance range

13. Gravitational force
 Weakest of all fundamental forces, but actsWeakest of all fundamental forces, but acts
over very long distancesover very long distances
 Always attractiveAlways attractive
 Acts between any two pieces of matter inActs between any two pieces of matter in
the universethe universe
 Very important in explaining the structureVery important in explaining the structure
of the universe, Can affect space time, timeof the universe, Can affect space time, time
slows down , space is warped .(Einstein)slows down , space is warped .(Einstein)

14. The 4 forces of Nature
Weak
• Beta-decay
• pp fusion
Strong
Quark
binding
Electromagnetic
•TV, PCs
• Magnets
• e- e+ creation
Gravity
Responsible of
Keeping us
well-planted on earth
Electric
charge
mass
weak
charge
strong
charge

15. The Road to Unification
Magnetism
Light
ElectromagneticElectromagnetic
Weak
Astronomical
Motion
Terrestrial
Motion
Electroweak Strong Gravitation
Grand
Unification
Single Force
Space
Time
Weak
Electricity

16. Quark confinement
There are no free quarks, quarks and ant quarks are “confined”
in colourless doublet (mesons) or triplets (baryons) by the exchange
of gluons
The new quarks bound
to the old quarks
and form new mesons
until the gluon connection
snaps, and other quark-anti quark
pairs are created out of the
energy released
Gluon hold quarks
together as they move
further apart
Z
0
Decay
® S.Ward

17. Force Particles (summary)
Particles interact and/or decay thanks to forces
Forces are also responsible of binding particles together
Strong: gluons
Only quarks
(because of their
colour charge)
Weak: W+
, W-
, Z0
Leptons and quarks
(only force for
neutrinos)
Electromagnetic: γ
Quarks and charged
leptons (no neutrinos)
Gravity: graviton?
Still to be discovered
Negligible effects on
particles

18. Beyond the Standard
Model:Unification of forces
WEAK
STRONGGRAVITY
ELECTRO-
MAGNETIC
UNIFIED
FORCE?
Looking for a simple elegant unified theory

19. The History of Grand
Unified Theory

20. Electricity and Magnetism
 Michael Faraday:Michael Faraday:
 Born: September 22, 1791Born: September 22, 1791
Died: August 25, 1867Died: August 25, 1867
 English physicist andEnglish physicist and
chemist whose many experimentschemist whose many experiments
contributed greatly to the understanding ofcontributed greatly to the understanding of
electromagnetism.electromagnetism.
FARADAYS,S LAW OFFARADAYS,S LAW OF
ELECTROMAGNETIC INDUCTION.ELECTROMAGNETIC INDUCTION.

21. Electricity and Magnetism
 James MaxwellJames Maxwell
 Born June 13, 1831, Edinburgh, ScotlandBorn June 13, 1831, Edinburgh, Scotland
died November 5, 1879, Cambridge,died November 5, 1879, Cambridge,
Cambridgeshire, EnglandCambridgeshire, England
 Scottish physicist best known for his formulationScottish physicist best known for his formulation
of electromagnetic theory.of electromagnetic theory.
 Incorporated light and wave phenomena intoIncorporated light and wave phenomena into
electromagnetismelectromagnetism
 FAMOUS MAXWELL,S EQUATIONSFAMOUS MAXWELL,S EQUATIONS

22. Electricity and Magnetism
 In 1905 Einstein’s special theory ofIn 1905 Einstein’s special theory of
relativity showed that electricity andrelativity showed that electricity and
magnetism were link and that Maxwell wasmagnetism were link and that Maxwell was
correct.correct.
 The single force of Electromagnetism isThe single force of Electromagnetism is
born.born.

23. Electroweak Force
 Sheldon GlashowSheldon Glashow
 Abdus SalamAbdus Salam
 Steven WeinbergSteven Weinberg
 Each physicist independently found that theEach physicist independently found that the
weak nuclear force could be unified withweak nuclear force could be unified with
electromagnetic force.electromagnetic force.

24. Electroweak Force
 At extremely high energies, 10At extremely high energies, 101515
GeV theGeV the
electromagnetic and weak forces become theelectromagnetic and weak forces become the
same.same.
 The relationship is based on the exchange ofThe relationship is based on the exchange of
four particles: the photon of EM interactions,four particles: the photon of EM interactions,
two charged W particles and a neutral Ztwo charged W particles and a neutral Z
particle.particle.

25. Weak force: W-
,W+
,Z0
β−decay
n pe→ νe
Electric charge
conserved at each
vertex
W-

26. Electroweak Force

27. Strong Nuclear Force
 Quantum Chromo dynamics was developed toQuantum Chromo dynamics was developed to
explain strong force during the 1970s.explain strong force during the 1970s.
 Quarks are believed interact by exchangingQuarks are believed interact by exchanging
gluons.gluons.
 The hope is to use that similarity to unify strongThe hope is to use that similarity to unify strong
with electroweak force.with electroweak force.
 The unification cannot be found because energyThe unification cannot be found because energy
levels 10levels 101212
higher than those needed to develop thehigher than those needed to develop the
electroweak force are required to test furtherelectroweak force are required to test further
unification.unification.

28. Strong Nuclear Force

29. Gravity
 Newton showed that bothNewton showed that both
astronomical and terrestrial motion could beastronomical and terrestrial motion could be
explained with gravitationexplained with gravitation
 In 1915 Einstein’s theory of general relativityIn 1915 Einstein’s theory of general relativity
was written in which concept on Anti Gravity &was written in which concept on Anti Gravity &
Black hole was given .Black hole was given .
 Einstein spent 30 years trying to unify EM withEinstein spent 30 years trying to unify EM with
gravity and failed.gravity and failed.

30. General Relativity
 The equivalence principle:The equivalence principle:
gravity and acceleration are equivalent –gravity and acceleration are equivalent –
i.e., one cannot discriminate betweeni.e., one cannot discriminate between
being at rest in a gravitational field andbeing at rest in a gravitational field and
being accelerated in the absence ofbeing accelerated in the absence of
gravitygravity

31. gravity = acceleration

32. General Relativity
 Mass causes space-time to curve:Mass causes space-time to curve:
Imagine space-time as a four-Imagine space-time as a four-
dimensional rubber sheet. Any objectdimensional rubber sheet. Any object
with mass causes this sheet to becomewith mass causes this sheet to become
deformed.deformed.

33. General Relativity
 The curvature of space-time tells matterThe curvature of space-time tells matter
how to move:how to move:
What we perceive as gravity arisesWhat we perceive as gravity arises
from the curvature of space-time.from the curvature of space-time.
Masses follow the ‘straightestMasses follow the ‘straightest
possible paths’ possible given thepossible paths’ possible given the
curvature.curvature.

34. Escape velocity from a black hole
 Remember (from Chapter 5) the escapeRemember (from Chapter 5) the escape
velocity is given byvelocity is given by
vvescesc = [2GM/R]= [2GM/R]1/21/2
 what if the escape velocity was equalwhat if the escape velocity was equal
to the speed of light?to the speed of light?
 this would set a maximum radius forthis would set a maximum radius for
which light could escape from anwhich light could escape from an
object with a given massobject with a given mass

36. The Schwarzschild radiusThe Schwarzschild radius
vv22
escesc = [2GM/R]= [2GM/R]= c= c22
 RRSS = 2GM/c= 2GM/c22
or Ror RSS = [3.0 x M/M= [3.0 x M/Msunsun] km] km

37. The Schwarzschild radius
 the larger the mass of a black hole, thethe larger the mass of a black hole, the
larger the Schwarzschild radiuslarger the Schwarzschild radius
 once light or any object has crossed theonce light or any object has crossed the
Schwarzschild radius (or event horizon), itSchwarzschild radius (or event horizon), it
can never escape the force of gravity of thecan never escape the force of gravity of the
black hole.black hole.

39. Black holes have no hair
 all information about the material thatall information about the material that
is inside the event horizon of a blackis inside the event horizon of a black
hole is lost,hole is lost, exceptexcept
 massmass
 chargecharge
 angular momentumangular momentum

40. Black hole Entropy Theorem
 The total amount of information (entropy)The total amount of information (entropy)
in the Universe cannot decrease (secondin the Universe cannot decrease (second
law of thermodynamics)law of thermodynamics)
 this is what lead Bekenstein and Hawkingthis is what lead Bekenstein and Hawking
to the idea that Black holes must radiateto the idea that Black holes must radiate

41. Falling into a black hole
 stretched by tidal forcesstretched by tidal forces
 time slows downtime slows down
 radiation is redshiftedradiation is redshifted

42. Observational Evidence
 there is evidence that black holes formedthere is evidence that black holes formed
from collapsed stars exist in some X-rayfrom collapsed stars exist in some X-ray
binariesbinaries
 most promising candidate:most promising candidate:
 Cygnus X-1: 18 MCygnus X-1: 18 Msunsun star orbiting anstar orbiting an
unseen companion with a mass of 10 Munseen companion with a mass of 10 Msunsun
 too massive to be a neutron star and tootoo massive to be a neutron star and too
small to be an ordinary starsmall to be an ordinary star

43. Supermassive Black Holes
 there is very good evidence from thethere is very good evidence from the
motions of stars and gas near the centers ofmotions of stars and gas near the centers of
galaxies that most galaxies (including ourgalaxies that most galaxies (including our
own) contain ‘supermassive black holes’ –own) contain ‘supermassive black holes’ –
black holes weighing millions to billions ofblack holes weighing millions to billions of
solar massessolar masses
 how these objects formed is still somethinghow these objects formed is still something
of a mystery…of a mystery…

44. White holes, Wormholes, and
tunnels through hyperspace
 black holes are only one of the severalblack holes are only one of the several
kinds of singularities in the equations ofkinds of singularities in the equations of
general relativitygeneral relativity
 white holes are sort of like the opposite ofwhite holes are sort of like the opposite of
black holesblack holes
 a wormhole is a black hole connecting to aa wormhole is a black hole connecting to a
white holewhite hole

45. Einstein-Rosen bridge

46. Wormhole

47. The Future of the Grand Unified
Theories

48.  Gravity may be unified by superstring theory,Gravity may be unified by superstring theory,
which is the best theory right now for unification.which is the best theory right now for unification.
 Higher energy experiments are needed to study theHigher energy experiments are needed to study the
strong nuclear force and its unification withstrong nuclear force and its unification with
electroweak.electroweak.
 More study of electroweak is still needed. ByMore study of electroweak is still needed. By
using the simplest version of the theory ausing the simplest version of the theory a
calculation was performed that determined acalculation was performed that determined a
proton life several orders of magnitude too short,proton life several orders of magnitude too short,
from 10from 102929
to 10to 103131
years.years.
 show that the life of a proton is greater thanshow that the life of a proton is greater than
10103232
years. which means that one protonyears. which means that one proton
decay vs.decay vs. 10103232
show that the life of a proton isshow that the life of a proton is
greater than 10greater than 103232
years. which means that oneyears. which means that one
proton decay vs. 10 to the power 32/ yearproton decay vs. 10 to the power 32/ year

49. Why is the Universe made of matter
and not equally of anti-matter?
 We have seen that for every fundamental particle thereWe have seen that for every fundamental particle there
is a corresponding antiparticle.is a corresponding antiparticle.
 Where are these anti-particles?Where are these anti-particles?
 Large amount of matter but no evidence of largeLarge amount of matter but no evidence of large
amount of antimatter in the Universe .Good Luck!amount of antimatter in the Universe .Good Luck!
Otherwise Existence of Universe is not possible.Otherwise Existence of Universe is not possible.....

50. Why has all the anti-matter gone?
Anti-matter
The development of the Universe containing
matter and no antimatter requires that
matter and antimatter behave differently
This phenomenon is due to CP violation..
matter Puff
Good thing for us that there is no antimatter around!

51. CP Violation
 CCPP == CCharge Conjugation (reverse charge) xharge Conjugation (reverse charge) x PParity (reversearity (reverse
spatial coordinates as in a mirror)spatial coordinates as in a mirror)
CPCP
beauty anti-beauty
B0 B0
“Nobody
is perfect”
CP-Violation: B0
and B0
do not behave exactly in the same
way (their decay pattern as a function of time is different)
For GUTS CP(OK),CPT(not ok) THAT IS Direction reversal
symmetry breaks down.

52. 53
The String Theory: The Wholly GrailThe String Theory: The Wholly Grail
 A theory to unify quantumA theory to unify quantum
mechanics and general relativitymechanics and general relativity
(all known forces).(all known forces).
 Every particle boils down toEvery particle boils down to
vibrating strings .vibrating strings .
 The difference in vibrationalThe difference in vibrational
strings makes up each atom andstrings makes up each atom and
gives them their properties.gives them their properties.
 All forces (and phenomena) inAll forces (and phenomena) in
existence described in oneexistence described in one
equation. (Space time unification)equation. (Space time unification)
Emission & Absorption ofEmission & Absorption of
particles take place through openparticles take place through open
and close strings like two legs in aand close strings like two legs in a
trouser, upper one , lower two ,trouser, upper one , lower two ,
some times open ,some timessome times open ,some times
close.close.

53. LIGHT and GRAVITY
in
STRING THEORY

54. STRING THEORY
 String theory offers us surprises ofString theory offers us surprises of
comparable magnitude.comparable magnitude.
 The elements in Einstein’s synthesis wereThe elements in Einstein’s synthesis were
space and time.space and time.
 The surprising synthesis emerging fromThe surprising synthesis emerging from
String theory in the last decade or soString theory in the last decade or so
involves two other familiar elements of ourinvolves two other familiar elements of our
experience : Light and Gravity.experience : Light and Gravity.

55.  Maxwell’s Electromagnetic theory of light ( pre-20’thMaxwell’s Electromagnetic theory of light ( pre-20’th
century ) when developed to incorporate the insights ofcentury ) when developed to incorporate the insights of
quantum mechanics and relativity ( early 20’th century )quantum mechanics and relativity ( early 20’th century )
gives rise to a new framework :gives rise to a new framework :
Quantum field theory ( QFT )Quantum field theory ( QFT )
–– mid-20’th centurymid-20’th century

56. Light and Photons
 In QFT, light can be viewed as anIn QFT, light can be viewed as an
elementary particle, called the photonelementary particle, called the photon
 QFT provides a new way to understand forceQFT provides a new way to understand force
: Force is due to the exchange of elementary: Force is due to the exchange of elementary
particlesparticles
 Electric Force between particles e.g.Electric Force between particles e.g.
electrons is due to the exchange of photons (electrons is due to the exchange of photons (
light )light )

57.  Hence QFT is the language of the Standard model ofHence QFT is the language of the Standard model of
Particle Physics (discovered by Weinberg andParticle Physics (discovered by Weinberg and
Salam ) which has been tested to extremely highSalam ) which has been tested to extremely high
accuracy in accelerators around the world.accuracy in accelerators around the world.

58. QFT and Strong Force
 Electrons spread to the outskirts of atoms. TheElectrons spread to the outskirts of atoms. The
core of atoms consists of nuclei, made of protonscore of atoms consists of nuclei, made of protons
and neutrons. Protons and neutrons are themselvesand neutrons. Protons and neutrons are themselves
made of quarks.made of quarks.
 QFT can also account for sub-nuclear forcesQFT can also account for sub-nuclear forces
between quarks.between quarks.
 The mediators of the ( strong ) force betweenThe mediators of the ( strong ) force between
quarks are gluons.quarks are gluons.

59. Photons, Gluons , Large N
 Photons – force between electric charge.Photons – force between electric charge.
One kind of charge ( one number, positive orOne kind of charge ( one number, positive or
negative ) . One kind of photon.negative ) . One kind of photon.
 Quarks come in 3 colours. Hence gluons come inQuarks come in 3 colours. Hence gluons come in
multiple types, depending on which quarks theymultiple types, depending on which quarks they
mediate between.mediate between.
 A simple mathematical generalization consists ofA simple mathematical generalization consists of
imagining theories with N quarks and N^2 gluons.imagining theories with N quarks and N^2 gluons.

60. WHY STRINGS ?
 QFT , while successful in describingQFT , while successful in describing
electromagnetic and sub-nuclear forces, is not soelectromagnetic and sub-nuclear forces, is not so
successful in describing the force of gravity.successful in describing the force of gravity.
 Rather we need String Theory, which is a newRather we need String Theory, which is a new
paradigm whereby fundamental constituents of theparadigm whereby fundamental constituents of the
world are lines – not points.world are lines – not points.
 A multiplicity of particles arises from differentA multiplicity of particles arises from different
vibration modes of the same string.vibration modes of the same string.

61. Weak Gravity
 In the limit of weak gravity, weIn the limit of weak gravity, we
recover Newton’s gravity, whichrecover Newton’s gravity, which
describes most planetary orbits todescribes most planetary orbits to
reasonable accuracy.reasonable accuracy.

62. Strong Gravity
 In the limit of strong gravity, the EinsteinIn the limit of strong gravity, the Einstein
equations describe black holes …equations describe black holes …
•ON very large cosmological scales, it describes the
expansion of the Universe.

63. A String duality between
Light and Gravity
 In string theory, light ( and its large NIn string theory, light ( and its large N
generalization ) arises from the same object asgeneralization ) arises from the same object as
gravitons. This leads to the unexpected relation :gravitons. This leads to the unexpected relation :
 Gravity for space-time in the shape of a solid ballGravity for space-time in the shape of a solid ball
in five dimensions is equivalent to a theory within five dimensions is equivalent to a theory with
no gravitons but with large N-light propagating onno gravitons but with large N-light propagating on
the four dimensional surfacethe four dimensional surface
of the ball.of the ball.

64. STRING : gluon and graviton
 Vibrations of an open string give rise to gluons.Vibrations of an open string give rise to gluons.
 Vibrations of closed string -- graviton ( since 70’s )Vibrations of closed string -- graviton ( since 70’s )

65. Gravitons and Gravity
 Graviton exchange .… force of gravity.Graviton exchange .… force of gravity.
Charges replaced by masses.Charges replaced by masses.
Photon replaced by graviton.Photon replaced by graviton.
 By using symmetries of the stringBy using symmetries of the string
world-sheet, one can recover the equationsworld-sheet, one can recover the equations
of general relativity.of general relativity.

66. 67
Problems With The String TheoryProblems With The String Theory
 Theory included a particle (a Tachyon) that was faster than theTheory included a particle (a Tachyon) that was faster than the
speed of light.speed of light.
 Theory required multiple dimensions like 10 or 26 space timeTheory required multiple dimensions like 10 or 26 space time
dimensionsdimensions. More be the dimensions lesser be the curve , sple. More be the dimensions lesser be the curve , sple
be the motion, easily understandable.be the motion, easily understandable.
 No observation or experiment could discount the theory.No observation or experiment could discount the theory.
 The mass-less particle. Later proposed as the graviton. AThe mass-less particle. Later proposed as the graviton. A
particle that governs gravity at atomic level and ultimatelyparticle that governs gravity at atomic level and ultimately
decided how small the strings are.decided how small the strings are.
 If an atom were the size of the solar system, a string would beIf an atom were the size of the solar system, a string would be
the size of a tree.the size of a tree.

67. 68
The String Theory ExpandsThe String Theory Expands
If we could master the rhythms of strings thenIf we could master the rhythms of strings then
we could explain all the matter, forces, andwe could explain all the matter, forces, and
phenomena in nature from the biggest thingsphenomena in nature from the biggest things
(planets, galaxies) to the smallest quantum(planets, galaxies) to the smallest quantum
particles.-Idea if Higgs that is H particle particleparticles.-Idea if Higgs that is H particle particle
in universe that is between earth & sun isin universe that is between earth & sun is
equivalent to Gluon exchange betweenequivalent to Gluon exchange between Quarks.Quarks.

68. 69
The Possibilities are InfiniteThe Possibilities are Infinite
 11 dimensions were needed for the 511 dimensions were needed for the 5
string theories to combine into one.string theories to combine into one.
Multi-dimensions are at the heart of theMulti-dimensions are at the heart of the
string theory.string theory.
 The degrees of freedom we (and what weThe degrees of freedom we (and what we
can observe) have locked us in to threecan observe) have locked us in to three
dimensions of space and one of time.dimensions of space and one of time.
While strings do not have the sameWhile strings do not have the same
limitations they can traverse all 11limitations they can traverse all 11
dimensions.dimensions.
 The 11The 11thth
dimension allows strings todimension allows strings to
stretch into membranes that can grow tostretch into membranes that can grow to
enormous sizes (like the size of aenormous sizes (like the size of a
universe).universe).
Eleven dimensions, parallel
universes, and a world made out
of strings. It's not science fiction,
it's string theory.

69. 70
Science or PhilosophyScience or Philosophy
 We live in a three dimensional plateWe live in a three dimensional plate
that traverses a 11 dimensional spatialthat traverses a 11 dimensional spatial
universe.universe.
 It is conceivable that our universe isIt is conceivable that our universe is
just one membrane that is a part ofjust one membrane that is a part of
an infinite number of membranes.an infinite number of membranes.
However, those membranes couldHowever, those membranes could
reside in 5, 6, or 7 dimensions.reside in 5, 6, or 7 dimensions.
Therefore, they could be right next toTherefore, they could be right next to
us but our three dimensionalus but our three dimensional
existence could never interact withexistence could never interact with
them, but strings could.them, but strings could.
 Multi dimensions could explain whyMulti dimensions could explain why
gravity is so weak in our universe.gravity is so weak in our universe.
Gravity could be just as strong as theGravity could be just as strong as the
other forces, but gravity could be aother forces, but gravity could be a
force that works in 5 or 6 dimensionsforce that works in 5 or 6 dimensions
and is weak in our three dimensionaland is weak in our three dimensional
space.space.

70. 71
Implications for E.T.Implications for E.T.
 The theory has pre-bigThe theory has pre-big
bang explanations.bang explanations.
 Two membranes in a fourTwo membranes in a four
dimensional space collideddimensional space collided
and all the laws, constants,and all the laws, constants,
and make up from the twoand make up from the two
four dimensionalfour dimensional
membranes combined intomembranes combined into
our existence.our existence.
 There is no reason why lifeThere is no reason why life
(intelligent) has to be(intelligent) has to be
limited to four dimensions.limited to four dimensions.

71. 72
More Implications for E.T.More Implications for E.T.
 Would a proven theory make it harder or easier to search forWould a proven theory make it harder or easier to search for
Everything.Everything.
 Would this expand our possibilities?Would this expand our possibilities?
 The theory accounts for hyperspace, traveling faster thanThe theory accounts for hyperspace, traveling faster than
light, multiple dimensions, strings traversing differentlight, multiple dimensions, strings traversing different
universes.universes.
 Will the theory help inWill the theory help in finding bacterial lifefinding bacterial life forms since it canforms since it can
determine the behavior of basically everything at its core (i.e.determine the behavior of basically everything at its core (i.e.
where certain particles, bacteria, is limited to, how naturewhere certain particles, bacteria, is limited to, how nature
“picks” certain molecules)?“picks” certain molecules)?
 Will knowing the behavior of everything about our fourWill knowing the behavior of everything about our four
dimensional universe help us flesh out where we should lookdimensional universe help us flesh out where we should look
in our Multi dimensional universe?in our Multi dimensional universe?
 Can the theory go far enough to determine how humansCan the theory go far enough to determine how humans
came to be and the possibilities of it happening elsewhere?came to be and the possibilities of it happening elsewhere?

72. Kaluza-Klein theory
 Kaluza-Klein added one extra spatialKaluza-Klein added one extra spatial
dimension to our conventional space-dimension to our conventional space-
time.time.
 Introduced 5-D metric tensor , which
can be decomposed into two parts

74. What have we learnt?
 A number of surprising things:A number of surprising things:
 A limited number ofA limited number of forces and matter particlesforces and matter particles
describe all the Universe we know about;describe all the Universe we know about;
 A theory of the interactions of matter with forces calledA theory of the interactions of matter with forces called
thethe Standard ModelStandard Model describes successfully thedescribes successfully the
phenomena of the subatomic world;phenomena of the subatomic world;
 There are evidences that there is lot more that we doThere are evidences that there is lot more that we do
not know about and our research should find: such asnot know about and our research should find: such as
thethe missing anti-mattermissing anti-matter,, dark matterdark matter,, puzzling neutrinopuzzling neutrino
properties, but also the Standard Model key-vault ..theproperties, but also the Standard Model key-vault ..the
HiggsHiggs!!

75. Looking into the future
The Higgs should be found at the LHC…The Higgs should be found at the LHC…
please be patient for a few moreplease be patient for a few more
hours….and you will learn about the Higgs,hours….and you will learn about the Higgs,
the LHC, and much more!the LHC, and much more!
NOT

76. Conclusion
Physicists are trying to find a single theory thatPhysicists are trying to find a single theory that
explains the whole universe. I think that there willexplains the whole universe. I think that there will
always be some gaps.always be some gaps. The part of the universe thatThe part of the universe that
we can perceive is very small compared to the partwe can perceive is very small compared to the part
we can notwe can not. Cosmological observations (e.g., dark. Cosmological observations (e.g., dark
matter, dark energy,…) indicate that we are stillmatter, dark energy,…) indicate that we are still
crawling under the mountain of a single unifiedcrawling under the mountain of a single unified
theorytheory

77. Conclusion (Continued)
 Physics at TeV scale likely to be richPhysics at TeV scale likely to be rich
 To fully understand it, we will likely needTo fully understand it, we will likely need aa
lotlot of detailed informationof detailed information
 LC will study new particles one by oneLC will study new particles one by one
⇒⇒ reconstruct the fundamental Lagrangianreconstruct the fundamental Lagrangian
 Then we would like to move on further withThen we would like to move on further with
absolute confidenceabsolute confidence

78.  Dark Matter likely to be TeV-scaleDark Matter likely to be TeV-scale
electrically neutral weakly interactingelectrically neutral weakly interacting
particle (particle (e.g.e.g., LSP, Lightest KK), LSP, Lightest KK)
 With LC, measure its mass, couplingsWith LC, measure its mass, couplings
 Can calculate its cosmic abundanceCan calculate its cosmic abundance
 If it agrees with cosmological observation,If it agrees with cosmological observation,
we understand Universe back to 10we understand Universe back to 10–12–12
secsec
after the Big Bangafter the Big Bang
Produce Dark Matter

79. 80
References and InformationReferences and Information
 http://superstringtheory.com/experm/exper3.html - Basics of String Theoryhttp://superstringtheory.com/experm/exper3.html - Basics of String Theory
 http://superstringtheory.com/basics/basic5.html - Basics of String Theoryhttp://superstringtheory.com/basics/basic5.html - Basics of String Theory
 http://www.sukidog.com/jpierre/strings/ - Basics of String Theoryhttp://www.sukidog.com/jpierre/strings/ - Basics of String Theory
 Superstrings: A Theory of Everything?Superstrings: A Theory of Everything?, ed. P.C.W. Davies and J. Brown, Cambridge, ed. P.C.W. Davies and J. Brown, Cambridge
University Press, 1988;University Press, 1988;
 E. Witten, Reflections on the Fate of Spacetime, Physics Today, April 1996.E. Witten, Reflections on the Fate of Spacetime, Physics Today, April 1996.
 http://public.web.cern.ch/Public/Welcome.html - CERN Websitehttp://public.web.cern.ch/Public/Welcome.html - CERN Website
 Hyperspace: A Scientific Odyssey Through Parallel Universe, Time Warps, And The TenthHyperspace: A Scientific Odyssey Through Parallel Universe, Time Warps, And The Tenth
DimensionDimension by Michio Kakuby Michio Kaku
 The Elegant Universe; Superstrings, Hidden Dimensions, And The Quest For The UltimateThe Elegant Universe; Superstrings, Hidden Dimensions, And The Quest For The Ultimate
TheoryTheory by Brian Greeneby Brian Greene

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81. THANK YOU !!!