7/28/2019 feynman diagram 1.pdf

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Feynman diagrams

Lee EunheeKAIST

Physical Mathematics I Conference 2010December 11, 2010

http://find/

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Contents

1 Introduction

2 Three types of particles

3 Interaction

4 Scattering

5 More application

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Why are Feynman diagrams

important?

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Why are Feynman diagrams

important?

It gives intuitive explanation for QED since diagrams areeasier to understand than mathematical formula.

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Why are Feynman diagrams

important?

It gives intuitive explanation for QED since diagrams areeasier to understand than mathematical formula.

It makes calculation simply

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Three types of particles

Each line on diagram represents a particle

e

e+

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through onepath. It goes through every possible path.

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through onepath. It goes through every possible path.

E(1 2) = P(1 2)

space

time

1

2

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Feynman

diagrams

Lee Eunhee

Introduction

Three types ofparticles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through onepath. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3)

space

time

1

2

3

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through one

path. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3) n2 P(3 2)

space

time

1

2

3

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through one

path. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3) n2 P(3 2)

+ P(1 4)

space

time

1

2

3

4

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through one

path. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3) n2 P(3 2)

+ P(1 4) n2

space

time

1

2

3

4

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through one

path. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3) n2 P(3 2)

+ P(1 4) n2 P(4 5)

space

time

1

2

3

4 5

F

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through one

path. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3) n2 P(3 2)

+ P(1 4) n2 P(4 5) n2

space

time

1

2

3

4 5

F

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Expressing E by PAn electron traveling from a certain time and place(point 1) toother certain time and place(point 2) doesnt go through one

path. It goes through every possible path.

E(1 2) = P(1 2) + P(1 3) n2 P(3 2)

+ P(1 4) n2 P(4 5) n2 P(5 2)

+ ...

multiply n2 each time sharp turn

space

time

1

2

3

4 5

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Feynman

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Feynman

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Interaction

At timeT

1 two electrons at 1 and 2

space

timeT1

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Feynman

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y

diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Simplest cases

E(1 3)

space

time

1

2

3

4

Feynman

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diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Simplest cases

E(1 3) E(2 4)

space

time

1

2

3

4

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Feynman

diagrams

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diagrams

Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

One photon interaction

multiply j for each time electron emitting and absorbingphotons

E(1 5)E(2 6)jP(5 6)j

space

time

1

2

3

4

5

6

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Feynman

diagrams

O h t i t ti th

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

One photon interaction other case

E(1 6)E(2 5)jP(5 6)j

space

time

1

2

3

4

5

6

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Feynman

diagrams

Two photons interaction

7/28/2019 feynman diagram 1.pdf

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Two photons interaction

space

time

1

2

3

4

5

6

7

8

Feynman

diagrams

Two photons interaction

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Two photons interaction

E(1 5) E(2 7)

space

time

1

2

3

4

5

6

7

8

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Feynman

diagrams

Two photons interaction

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Two photons interaction

E(1 5) E(2 7)j P(5 6)jj P(7 8)j

space

time

1

2

3

4

5

6

7

8

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Feynman

diagrams

Interaction

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

Interaction

No photon cases :

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Feynman

diagrams

Lee EunheeInteraction

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

No photon cases :

E(1

3)

E(2

4)E(1 4) E(2 3)

One photon cases :

E(1 5) E(2 6)j P(5 6)jE(5 3) E(6 4)

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Feynman

diagrams

Lee EunheeInteraction

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

No photon cases :

E(1

3)

E(2

4)E(1 4) E(2 3)

One photon cases :

E(1 5) E(2 6)j P(5 6)jE(5 3) E(6 4)

E(1 6) E(2 5)j P(5 6)j

E(6 4) E(5 3)

Two photons cases :

E(1 5) E(2 7)j P(5 6)jj P(7 8)

j E(5 8) E(7 6) E(8 3) E(6 4)

Feynman

diagrams

Lee EunheeInteraction

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Lee Eunhee

Introduction

Three types of

particles

Interaction

Scattering

More

application

It decreases fast since, j 110

.

We can stop at desired accuracy.

Feynman

diagrams

Lee EunheeScattering

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Introduction

Three types of

particles

Interaction

Scattering

More

application

1 dominant case

space

time

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Feynman

diagrams

Lee EunheeScattering

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Introduction

Three types of

particles

Interaction

Scattering

More

application

1 dominant case

2 emitting before absorbing

3 electron going to past

space

time

How could it be happened?

Feynman

diagrams

Lee EunheePositron

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Introduction

Three types of

particles

Interaction

Scattering

More

application1 Same as electron but has opposite charge

2 Anti-particle of electron3 Colliding electron and positron produces photon

Feynman

diagrams

Lee EunheeElectron goes to past

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Introduction

Three types of

particles

Interaction

Scattering

More

application

e

e+

space

time

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Feynman

diagrams

Lee EunheeElectron goes to past

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Introduction

Three types of

particles

Interaction

Scattering

More

application

e

e+

space

timeT1 T2

Feynman

diagrams

Lee EunheeElectron goes to past

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Introduction

Three types of

particles

Interaction

Scattering

More

application

e

e+

space

timeT1 T2

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