and

Stockholm, August 27, 2004

Gerard ’t Hooft

Utrecht University

The Nature of

Sir James Clark Maxwell

1831-1879- Statistical Mechanics- Thermodynamics

- Improved the mathematical formulation of Michael Faraday’s theories of electricity and magnetic lines of force ...

The electro-magnetic force

Albert Einstein

1879 – 19551905: - Photo-electric effect - Special Relativity - Brownian motion; statistical mechanics1915: General relativity (gravitation)

/ 0v c 7 /8Special Relativity

Quantum Mechanics

QuantumMechanics

SpecialRelativity +

=Elementary Particle Physics

( = High Energy Physics = Quantum Field Theory )

anti- leptons

photon Leptons

e

anti- baryons

mesons

o

SL KK

KK

baryons

anti-

o

o

NP

Hadrons

21 spin

spin 1

0spin

21 spin

23 spin

1969

This is only 4 % of the matter in theUniverse ! (See Licia verde’s talk)

e

the forcesthe ELECTRO MAGNETIC force

the STRONG force

the WEAK force

Forces:

Known from experiment

The Yang-Mills Field

C.N. Yang and R.L. Mills, 1954

proton neutron

Yang - Mills quanta

-o

-

+o

o+

+ o

Multiplets

According to the Yang-Mills-theory

P N

o

A oA A

Nucleons

pions

Yang-Millsbosons

21spin

0spin

1spin

Peter Higgs

Breaking Rotational Symmetry

THIS becomes an essential degree

of freedom ...And THIS is theHiggs degree of

Freedom

… turning the gauge

force carriers massive !

St. Weinberg

S.L. Glashow

A. Salam

Weinberg Model

e

1 2 RIGHTspin

W

oZ

W

1spin

Weinberg’s lepton model

Leptons Gauge bosons

0Hspin 0

Higgs

ee

1 2 LEFTspin

e

e

1 2 RIGHTspin

e

1 2 LEFTspin

Anti –Leptons

Proton Lambda Antiproton

Pi-plus Pi-zero

The hadronic particles …

The Yang-Mills Color Field

Quantum Chromo Dynamics

Quark speciesquarks

s

u

d

u u

d d

s s

Antiquarks

c c c

u

d

s

u u

d d

s s

up

down

c c c charm

strange

tb

t tb b

t

b

tt

b b

top

bottom

weak

strong

Graviton

Generation I Generation IIThe Standard Model

Gauge Bosons

0Z W

W

g

c cc

Higgs

Generation III

b b

tt t

b

Leptons ee

Quarksu

d ssd

uu

sd

Total cross sections

CESR

DORIS

PEPPETRA

TRISTAN

hadronse e

e e

e e

Gravitation

The fourth force:

1 22

M MF G

R

1510 m

1810 m

2110 m

2410 m

2710 m

3010 m

3310 m

The highway across

the desert

Today’sLimit …

GUTs

3510 mPlanck length :

e

Further unificationSU(4) x SU(2) x SU(2)

ru gu bu SO(10)

erd gd bd

rd gd bd e

ru gu bu e

3 generations

The SuperString Theory

A Black Hole