From gauge-fields to observables
-
A bottom-up construction in Landau-gauge QCD and beyond
Axel Maas
15th of February 2010
University of Sussex
UK
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Overview
●
Odds and ends: The necessity for non-perturbative physics
Supported by
Describing Gluons/Axel Maas
Slides left: 59 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Overview
●
Odds and ends: The necessity for non-perturbative physics
●
Fundamental issues: Gauge theories beyond perturbation theory
Supported by
Describing Gluons/Axel Maas
Slides left: 59 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Overview
●
Odds and ends: The necessity for non-perturbative physics
●
Fundamental issues: Gauge theories beyond perturbation theory
●
Properties of elementary particles
●
Gluons
●
Scalar matter
Supported by
Describing Gluons/Axel Maas
Slides left: 59 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Overview
●
Odds and ends: The necessity for non-perturbative physics
●
Fundamental issues: Gauge theories beyond perturbation theory
●
Properties of elementary particles
●
●
●
Gluons
●
Scalar matter
Extended outlook
●
Fermionic matter and hadrons
●
Gluons at finite temperature
Summary
Supported by
Describing Gluons/Axel Maas
Slides left: 59 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Describing Gluons/Axel Maas
Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Contains two kinds of particles
Describing Gluons/Axel Maas
Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Contains two kinds of particles
●
Matter: Quarks, leptons
Describing Gluons/Axel Maas
u
c
t
d
s
b
e 



e
Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Contains two kinds of particles
●
●
u
c
t
Matter: Quarks, leptons
d
s
b W
Force particles: Photon, gluon,
W- and Z-boson
e 
 Z
Describing Gluons/Axel Maas
e


g

Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Contains two kinds of particles
●
●
●
u
c
t
Matter: Quarks, leptons
d
s
b W
Force particles: Photon, gluon,
W- and Z-boson
e 
 Z
e


g
H

The Higgs is a bit of both, but more like matter
Describing Gluons/Axel Maas
Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Contains two kinds of particles
●
●
●
●
u
c
t
Matter: Quarks, leptons
d
s
b W
Force particles: Photon, gluon,
W- and Z-boson
e 
 Z
e


g
H

The Higgs is a bit of both, but more like matter
Description with perturbation theory very successful
Describing Gluons/Axel Maas
Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
The standard model
●
●
The standard model (until now) describes the physics
accessible in accelerator-based experiments
Contains two kinds of particles
●
●
●
u
c
t
Matter: Quarks, leptons
d
s
b W
Force particles: Photon, gluon,
W- and Z-boson
e 
 Z
e


g
H

The Higgs is a bit of both, but more like matter
●
Description with perturbation theory very successful
●
But...
Describing Gluons/Axel Maas
Slides left: 58 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
●
Bound states – hadrons, nucleons, and nuclei
●
Important in intermediate states – see muon g-2
Describing Gluons/Axel Maas
u
d
Slides left: 57 (in this section: 1)
u
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
●
Bound states – hadrons, nucleons, and nuclei
●
●
Important in intermediate states – see muon g-2
Confinement
Describing Gluons/Axel Maas
u
d
Slides left: 57 (in this section: 1)
u
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
●
u
Important in intermediate states – see muon g-2
●
Confinement
●
Dynamical generation of masses
Describing Gluons/Axel Maas
Mass
●
d
u
100%
80%
60%
Strong
Higgs
40%
20%
0%
u
d
s
c
b
t
W
Z Leptons
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
●
●
Confinement
●
Dynamical generation of masses
●
●
●
u
Important in intermediate states – see muon g-2
Mass
●
100%
80%
Formation of the Higgs condensate
60%
Heavy Higgs
20%
Strong new physics
Describing Gluons/Axel Maas
d
u
Strong
Higgs
40%
0%
u
d
s
c
b
t
W
Z Leptons
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
●
●
Confinement
●
Dynamical generation of masses
●
●
●
●
u
Important in intermediate states – see muon g-2
Mass
●
100%
80%
Formation of the Higgs condensate
60%
Heavy Higgs
20%
Strong new physics
d
Strong
Higgs
40%
0%
u
d
s
c
b
t
W
Z Leptons
Phase transitions
Describing Gluons/Axel Maas
u
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
●
●
Confinement
●
Dynamical generation of masses
●
●
●
●
u
Important in intermediate states – see muon g-2
Mass
●
100%
80%
Formation of the Higgs condensate
60%
Heavy Higgs
20%
Strong new physics
d
Strong
Higgs
40%
0%
u
d
s
c
b
t
W
Z Leptons
Phase transitions
Describing Gluons/Axel Maas
u
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
Important in intermediate states – see muon g-2
●
Confinement
●
Dynamical generation of masses
●
●
●
●
u
80%
60%
Heavy Higgs
20%
Phase transitions
Describing Gluons/Axel Maas
u
100%
Formation of the Higgs condensate
Strong new physics
d
Strong
Higgs
40%
0%
u
d
s
c
b
t
W
Z Leptons
Higgs phase
~Higgs mass
●
Mass
●
Weak confinement
~gauge coupling
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
Important in intermediate states – see muon g-2
●
Confinement
●
Dynamical generation of masses
●
●
●
u
80%
60%
Heavy Higgs
20%
●
Phase transitions
●
Factorization – problems?
Describing Gluons/Axel Maas
u
100%
Formation of the Higgs condensate
Strong new physics
d
Strong
Higgs
40%
0%
u
d
s
c
b
t
W
Z Leptons
Higgs phase
~Higgs mass
●
Mass
●
Weak confinement
~gauge coupling
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Beyond perturbation theory
Bound states – hadrons, nucleons, and nuclei
Important in intermediate states – see muon g-2
●
Confinement
●
Dynamical generation of masses
●
●
●
u
80%
60%
Heavy Higgs
20%
●
Phase transitions
●
Factorization – problems?
●
...
Describing Gluons/Axel Maas
u
100%
Formation of the Higgs condensate
Strong new physics
d
Strong
Higgs
40%
0%
u
d
s
c
b
t
W
Z Leptons
Higgs phase
~Higgs mass
●
Mass
●
Weak confinement
~gauge coupling
Slides left: 57 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
Must include perturbation theory for systematic control
Describing Gluons/Axel Maas

Slides left:
56 (in this section: 0)

Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
Describing Gluons/Axel Maas

Slides left:
56 (in this section: 0)

Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
• Basic entities: Force particles (gluons,...)
g
• Yang-Mills theory as a prototype
Describing Gluons/Axel Maas

Slides left:
56 (in this section: 0)

Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
• Basic entities: Force particles (gluons,...)
g
• Yang-Mills theory as a prototype
• Simple matter particles – fermions, scalar
u
g
• Bound states and the phase diagram
Describing Gluons/Axel Maas

Slides left:
56 (in this section: 0)

Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
• Basic entities: Force particles (gluons,...)
g
• Yang-Mills theory as a prototype
• Simple matter particles – fermions, scalar
u
g
• Bound states and the phase diagram
• Higgs and the Higgs effect
Describing Gluons/Axel Maas
H W Z

Slides left:
56 (in this section: 0)

Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
• Basic entities: Force particles (gluons,...)
g
• Yang-Mills theory as a prototype
• Simple matter particles – fermions, scalar
u
g
• Bound states and the phase diagram
• Higgs and the Higgs effect
H W Z
• The full standard model an beyond
c
Describing Gluons/Axel Maas

Slides left:
56 (in this section: 0)

Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype
• Simple matter particles – fermions, scalar
u
g
• Bound states and the phase diagram
• Higgs and the Higgs effect
H W Z
• The full standard model an beyond
c
Describing Gluons/Axel Maas
Slides left: 56 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype
➔Simple matter particles – fermions, scalar
u
g
➔Bound states and the phase diagram
➔Higgs and the Higgs effect
H W Z
• The full standard model an beyond
c
Describing Gluons/Axel Maas
Slides left: 56 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype
➔Simple matter particles – fermions, scalar
u
g
➔Bound states and the phase diagram
➔Higgs and the Higgs effect
H W Z
✗ The full standard model an beyond
c
Describing Gluons/Axel Maas
Slides left: 56 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype
Describing Gluons/Axel Maas
u
g
H W Z
c
Slides left: 56 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype – somewhat technical
Describing Gluons/Axel Maas
u
g
H W Z
c
Slides left: 56 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Force particles
Describing Gluons/Axel Maas
Slides left: 55 (in this section: 18)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge fields
●
Gauge theories describe force particles as gauge fields
●
Prototypes: QED, Yang-Mills theory, QCD, the standard model
Describing Gluons/Axel Maas
Slides left: 55 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge fields
●
Gauge theories describe force particles as gauge fields
●
●
Prototypes: QED, Yang-Mills theory, QCD, the standard model
Gauge fields are not uniquely defined
●
Gauge transformation can change them without changing
observables
Describing Gluons/Axel Maas
Slides left: 55 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
Describing Gluons/Axel Maas
(artist's view)
Slides left: 52 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
(artist's view)
Each point a complete space-time
history (or configuration) of the
gauge-fields
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
●
(artist's view)
Each point a complete space-time
history (or configuration) of the
gauge-fields
But gauge fields are not unique
●
Gauge transformation change
them
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
●
Each point a complete space-time
history (or configuration) of the
gauge-fields
But gauge fields are not unique
●
●
(artist's view)
Gauge transformation change
them
Each configuration related by a
gauge transformation provides
the same observables
●
Gauge orbit
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge fields
●
Gauge theories describe force particles as gauge fields
●
●
Prototypes: QED, Yang-Mills theory, QCD, the standard model
Gauge fields are not uniquely defined
●
●
Gauge transformation can change them without changing
observables
This also applies to matter charged under the gauge group
Describing Gluons/Axel Maas
Slides left: 54 (in this section: 17)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge fields
●
Gauge theories describe force particles as gauge fields
●
●
Prototypes: QED, Yang-Mills theory, QCD, the standard model
Gauge fields are not uniquely defined
●
Gauge transformation can change them without changing
observables
●
This also applies to matter charged under the gauge group
●
Even the charges are not gauge-invariant
●
Except for electric charges
●
No concept 0f a local gauge-invariant charge distribution
●
Similar to energy density in general relativity
Describing Gluons/Axel Maas
Slides left: 54 (in this section: 17)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge fields
●
Gauge theories describe force particles as gauge fields
●
●
Prototypes: QED, Yang-Mills theory, QCD, the standard model
Gauge fields are not uniquely defined
●
Gauge transformation can change them without changing
observables
●
This also applies to matter charged under the gauge group
●
Even the charges are not gauge-invariant
●
Except for electric charges
●
No concept 0f a local gauge-invariant charge distribution
●
●
Similar to energy density in general relativity
Only bound states can be gauge-invariant, and thus physical
Describing Gluons/Axel Maas
Slides left: 54 (in this section: 17)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Prototype: Yang-Mills Theory
●
●
Lagrangian:
1 a 
L=− F   F a
4
a
a
a
a
b c
F  =∂ A −∂ A gf bc A  A 
Degrees of freedom:
a
Gluons: A 
●
●
g is the coupling constant, giving the strength of coupling
f abc are numbers, depending on the gauge group, SU(3) for QCD:
gluons are organized in multiplets, just as with spin
Describing Gluons/Axel Maas
Slides left: 53 (in this section: 16)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge-fixing
●
Yang-Mills theory is a gauge theory
●
a

a

a
b
a
bc
c

b
Gauge transformations A  A  ∂− g f A   x 
a
with arbitrary   x  change the gauge fields, but leave physics
invariant
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 15)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge-fixing
●
Yang-Mills theory is a gauge theory
●
a

a

a
b
a
bc
c

b
Gauge transformations A  A  ∂− g f A   x 
a
with arbitrary   x  change the gauge fields, but leave physics
invariant
●
Choice to select an arbitrary element of the gauge orbit
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 15)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge-fixing
●
Yang-Mills theory is a gauge theory
●
a

a

a
b
a
bc
c

b
Gauge transformations A  A  ∂− g f A   x 
a
with arbitrary   x  change the gauge fields, but leave physics
invariant
●
Choice to select an arbitrary element of the gauge orbit
●
Gluons (and elementary particles) depend on the choice
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 15)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge-fixing
●
Yang-Mills theory is a gauge theory
●
a

a

a
b
a
bc
c

b
Gauge transformations A  A  ∂− g f A   x 
a
with arbitrary   x  change the gauge fields, but leave physics
invariant
●
Choice to select an arbitrary element of the gauge orbit
●
Gluons (and elementary particles) depend on the choice
●
Requires a prescription to make comparisons or obtain properties
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 15)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gauge-fixing
●
Yang-Mills theory is a gauge theory
●
a

a

a
b
a
bc
c

b
Gauge transformations A  A  ∂− g f A   x 
a
with arbitrary   x  change the gauge fields, but leave physics
invariant
●
●
Choice to select an arbitrary element of the gauge orbit
●
Gluons (and elementary particles) depend on the choice
●
Requires a prescription to make comparisons or obtain properties
Example: Landau gauge condition ∂ Aa=0
●
Here only Landau gauge results
●
Many other gauges have been studied
Describing Gluons/Axel Maas
Slides left: 52 (in this section: 15)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
Describing Gluons/Axel Maas
(artist's view)
Slides left: 51 (in this section: 14)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
(artist's view)
Impose Landau gauge condition
●
Reduces configuration space to a
hypersurface
Describing Gluons/Axel Maas
Slides left: 51 (in this section: 14)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Unambiguous gauge-fixing
●
Local gauge condition
●
●
[For an introduction: Sobreiro & Sorella, 2005]
Landau gauge: ∂ Aa=0
Can be implemented using auxiliary fields, the so-called
ghost fields
●
No physical objects: Pure mathematical convenience
Describing Gluons/Axel Maas
Slides left: 50 (in this section: 13)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Perturbative) Landau gauge
●
Lagrangian:
1 a  a
 b
L=− F  F a −c ∂ D ab c
4
ab
ab
ab
c
D  = ∂−ig f c A
●
Degrees of freedom:
Gluons: A
a

Ghosts: c a , c a
●
Ghosts interact with gluons: They have to be included
●
Here: Euclidean version
Describing Gluons/Axel Maas
Slides left: 49 (in this section: 12)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Unambiguous gauge-fixing
●
Local gauge condition
●
●
[For an introduction: Sobreiro & Sorella, 2005]
Landau gauge: ∂ Aa=0
Sufficient for perturbation theory
Describing Gluons/Axel Maas
Slides left: 48 (in this section: 11)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Proceeding
●
●
Once the gauge is fixed, all kind of (perturbative)
calculations can be done
Use correlation functions as basic entities
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Correlation functions
●
[Alkofer & von Smekal 2000]
Correlation functions, describe a theory completely
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Correlation functions
[Alkofer & von Smekal 2000]
●
Correlation functions, describe a theory completely
●
Expectation values of a product of field operators
●
Build from the fields, here gluons and ghost
●
E.g.:  c
 c
●
Full correlation functions contain all information
●
There are an infinite number of them
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Correlation functions
[Alkofer & von Smekal 2000]
●
Correlation functions, describe a theory completely
●
Expectation values of a product of field operators
●
Build from the fields, here gluons and ghost
●
E.g.:  c
 c
●
Full correlation functions contain all information
●
There are an infinite number of them
●
If having a non-vanishing color charge they change under gauge
transformation
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Correlation functions
[Alkofer & von Smekal 2000]
●
Correlation functions, describe a theory completely
●
Expectation values of a product of field operators
●
Build from the fields, here gluons and ghost
●
E.g.:  c
 c
●
Full correlation functions contain all information
●
There are an infinite number of them
●
●
If having a non-vanishing color charge they change under gauge
transformation
Simplest non-zero correlation functions: 2-point functions or propagators
●
Expectation values of products of two field operators
●
1-point functions vanish
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Propagators
●
In Landau gauge: Gluon and one auxiliary field: Ghost
●
Gluon:
ab

a

b

D  x− y=  A  x  A  y
p p Z  p
D   p=− 2  2
p
p
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Propagators
●
In Landau gauge: Gluon and one auxiliary field: Ghost
●
Gluon:
ab

a

b

D  x− y=  A  x  A  y
p p Z  p
D   p=− 2  2
p
p
●
Ghost:
ab
a
b
D G  x− y = c  x c  y
−G  p
D G  p=
2
p
Describing Gluons/Axel Maas
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Propagators
●
In Landau gauge: Gluon and one auxiliary field: Ghost
●
Gluon:
ab

a

b

D  x− y=  A  x  A  y
p p Z  p
D   p=− 2  2
p
p
●
Ghost:
ab
a
b
D G  x− y = c  x c  y
−G  p
D G  p=
2
p
●
Ghost propagator can be expressed as a gluon operator, the inverse
Faddeev-Popov operator
ab
ab −1
ab
D G  x− y  ~ ∂ D    = ∂  ∂− g f
Describing Gluons/Axel Maas
abc
c
−1
A  
Slides left: 47 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Proceeding
●
●
●
Once the gauge is fixed, all kind of (perturbative)
calculations can be done
Use correlation functions as basic entities
Combination of gauge-variant correlation functions
yield gauge-invariant results
●
E.g. scattering cross-sections
Describing Gluons/Axel Maas
Slides left: 46 (in this section: 9)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Proceeding
●
●
●
Once the gauge is fixed, all kind of (perturbative)
calculations can be done
Use correlation functions as basic entities
Combination of gauge-variant correlation functions
yield gauge-invariant results
●
●
E.g. scattering cross-sections
Almost all perturbative calculations proceed via
gauge-variant correlation functions
Describing Gluons/Axel Maas
Slides left: 46 (in this section: 9)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Also non-perturbatively?
Would be nice:
Same entities and concepts as in perturbation theory
Direct connection to perturbation theory
Describing Gluons/Axel Maas
Slides left: 45 (in this section: 8)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
(artist's view)
Perturbation theory is applicable close
to the origin
Describing Gluons/Axel Maas
Perturbation theory
Slides left: 44 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
●
(artist's view)
Perturbation theory is applicable close
to the origin
Non-perturbative physics probes the
complete hypersurface
Describing Gluons/Axel Maas
Perturbation theory
Slides left: 44 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Unambiguous gauge-fixing
●
[For an introduction: Sobreiro & Sorella, 2005]
Local gauge condition
●
Landau gauge: ∂ Aa=0
●
Sufficient for perturbation theory
●
Insufficient beyond perturbation theory
●
There are gauge-equivalent configurations which obey the same
local gauge-condition: Gribov copies [Gribov 1978]
Describing Gluons/Axel Maas
Slides left: 43 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Unambiguous gauge-fixing
●
[For an introduction: Sobreiro & Sorella, 2005]
Local gauge condition
●
Landau gauge: ∂ Aa=0
●
Sufficient for perturbation theory
●
Insufficient beyond perturbation theory
●
●
There are gauge-equivalent configurations which obey the same
local gauge-condition: Gribov copies [Gribov 1978]
There are no local gauge conditions known, which select a
unique gauge field configuration
[Singer 1978]
●
Non-local conditions possible
Describing Gluons/Axel Maas
Slides left: 43 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Example: Instanton
●
[Maas, 2005]
Instanton field configuration is
Describing Gluons/Axel Maas
a
a
2
2
A r , =2r   / g r  
Slides left: 42 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Example: Instanton
●
[Maas, 2005]
Instanton field configuration is
●
a
a
2
It is a Landau-gauge configuration, satisfying ∂ Aa=0
Describing Gluons/Axel Maas
2
A r , =2r   / g r  
Slides left: 42 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Example: Instanton
●
[Maas, 2005]
Gauge transformation to
Describing Gluons/Axel Maas
a
a
2
2
2
2
A r , =−2r     / gr r  
Slides left: 42 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Example: Instanton
●
[Maas, 2005]
Gauge transformation to
●
a
a
2
2
2
It is still a Landau gauge configuration!
Describing Gluons/Axel Maas
2
A r , =−2r     / gr r  
Slides left: 42 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Example: Instanton
●
[Maas, 2005]
Gauge transformation to
a
a
●
It is still a Landau gauge configuration!
●
Gribov copy
●
Non-perturbative: Depends on 1/ g
Describing Gluons/Axel Maas
2
2
2
2
A r , =−2r     / gr r  
Slides left: 42 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Residual freedom
●
Impose Landau gauge condition
●
Reduces configuration space to a hypersurface
Describing Gluons/Axel Maas
Slides left: 41 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Residual freedom
●
Impose Landau gauge condition
●
●
Reduces configuration space to a hypersurface
Leaves the non-perturbative gauge freedom to choose between gaugeequivalent Gribov copies
●
Residual gauge orbit
●
Set of Gribov copies, in general not continous
Describing Gluons/Axel Maas
Slides left: 41 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Residual freedom
●
Impose Landau gauge condition
●
●
●
Reduces configuration space to a hypersurface
Leaves the non-perturbative gauge freedom to choose between gaugeequivalent Gribov copies
●
Residual gauge orbit
●
Set of Gribov copies, in general not continous
A definite prescription is required for an unambiguous result
●
●
There is no unique prescription how to complete Landau gauge nonperturbatively
There is no possibility using a local condition
Describing Gluons/Axel Maas
Slides left: 41 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Residual freedom
●
Impose Landau gauge condition
●
●
●
Leaves the non-perturbative gauge freedom to choose between gaugeequivalent Gribov copies
●
Residual gauge orbit
●
Set of Gribov copies, in general not continous
A definite prescription is required for an unambiguous result
●
●
●
Reduces configuration space to a hypersurface
There is no unique prescription how to complete Landau gauge nonperturbatively
There is no possibility using a local condition
Construct a non-local condition instead to solve the problem
Describing Gluons/Axel Maas
Slides left: 41 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
Describing Gluons/Axel Maas
(artist's view)
[Gribov NPA 1978, Zwanziger 1993...2003]
Slides left: 40 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
(artist's view)
Gribov horizon encloses all field
configurations with positive
Faddeev-Popov operator −∂ D 
Describing Gluons/Axel Maas
[Gribov NPA 1978, Zwanziger 1993...2003]
Gribov horizon
Slides left: 40 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
(artist's view)
Gribov horizon encloses all field
configurations with positive
Faddeev-Popov operator −∂ D 
●
[Gribov NPA 1978, Zwanziger 1993...2003]
Gribov horizon
All gauge orbits pass through
this region
●
Bounded (and convex))
●
Many Gribov copies for each
Describing Gluons/Axel Maas
Slides left: 40 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
Gribov horizon encloses all field
configurations with positive
Faddeev-Popov operator −∂ D 
●
●
(artist's view)
[Gribov NPA 1978, Zwanziger 1993...2003]
Gribov horizon
All gauge orbits pass through
this region
●
Bounded (and convex))
●
Many Gribov copies for each
Includes the fundamental modular
region
●
●
One and only one Gribov copy
Also bounded (and convex)
Describing Gluons/Axel Maas
Fundamental modular region
Slides left: 40 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Configuration space
●
Gribov horizon encloses all field
configurations with positive
Faddeev-Popov operator −∂ D 
●
●
(artist's view)
[Gribov NPA 1978, Zwanziger 1993...2003]
Gribov horizon
All gauge orbits pass through
this region
●
Bounded (and convex))
●
Many Gribov copies for each
Includes the fundamental modular
region
●
One and only one Gribov copy
●
Also bounded (and convex)
●
Complicated definition
Describing Gluons/Axel Maas
Fundamental modular region
Slides left: 40 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
At the boundary of the first Gribov horizon the Faddeev-Popov
operator develops zero eigenmodes
Describing Gluons/Axel Maas
Slides left: 39 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
At the boundary of the first Gribov horizon the Faddeev-Popov
operator develops zero eigenmodes
Lowest eigenvalue of the Faddeev-Popov operator varies along the
gauge orbits
Describing Gluons/Axel Maas
Slides left: 39 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
●
At the boundary of the first Gribov horizon the Faddeev-Popov
operator develops zero eigenmodes
Lowest eigenvalue of the Faddeev-Popov operator varies along the
gauge orbits
Finite quantity, but very hard to determine in general
Describing Gluons/Axel Maas
Slides left: 39 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
At the boundary of the first Gribov horizon the Faddeev-Popov
operator develops zero eigenmodes
Lowest eigenvalue of the Faddeev-Popov operator varies along the
gauge orbits
●
Finite quantity, but very hard to determine in general
●
Is there also an expression in terms of a correlation function?
Describing Gluons/Axel Maas
Slides left: 39 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
At the boundary of the first Gribov horizon the Faddeev-Popov
operator develops zero eigenmodes
Lowest eigenvalue of the Faddeev-Popov operator varies along the
gauge orbits
●
Finite quantity, but very hard to determine in general
●
Is there also an expression in terms of a correlation function?
●
Not directly. But the ghost propagator is influenced by the
eigenspectrum:
−G  p
ab
ab −1
=D

p
~
∂
D
G

   ~
2
p
Describing Gluons/Axel Maas
∑i
1 2
∣i ∣
i
Slides left: 39 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
At the boundary of the first Gribov horizon the Faddeev-Popov
operator develops zero eigenmodes
Lowest eigenvalue of the Faddeev-Popov operator varies along the
gauge orbits
●
Finite quantity, but very hard to determine in general
●
Is there also an expression in terms of a correlation function?
●
Not directly. But the ghost propagator is influenced by the
eigenspectrum:
−G  p
ab
ab −1
=D

p
~
∂
D
G

   ~
2
p
●
∑i
1 2
∣i ∣
i
G(p) candidate for a characterization of a copy
Describing Gluons/Axel Maas
Slides left: 39 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
[Maas, unpublished, Maas, 2008/9, Fischer et al. 2008]
Effects will be strongest at the most non-perturbative
momenta: The infrared
Choose the renormalization-group invariant B=G(0)/G(P)
with P large fixed as a second gauge parameter
Describing Gluons/Axel Maas
Slides left: 38 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
[Maas, unpublished, Maas, 2008/9, Fischer et al. 2008]
Effects will be strongest at the most non-perturbative
momenta: The infrared
Choose the renormalization-group invariant B=G(0)/G(P)
with P large fixed as a second gauge parameter
●
Fourier-transform at low momentum: Highly non-local
●
Appears to be also working in the continuum and infinite volume
Describing Gluons/Axel Maas
Slides left: 38 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
[Maas, unpublished, Maas, 2008/9, Fischer et al. 2008]
Effects will be strongest at the most non-perturbative
momenta: The infrared
Choose the renormalization-group invariant B=G(0)/G(P)
with P large fixed as a second gauge parameter
●
Fourier-transform at low momentum: Highly non-local
●
Appears to be also working in the continuum and infinite volume
●
More studies required and underway for final confirmation
Describing Gluons/Axel Maas
Slides left: 38 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
[Maas, unpublished, Maas, 2008/9, Fischer et al. 2008]
Effects will be strongest at the most non-perturbative
momenta: The infrared
Choose the renormalization-group invariant B=G(0)/G(P)
with P large fixed as a second gauge parameter
●
Fourier-transform at low momentum: Highly non-local
●
Appears to be also working in the continuum and infinite volume
More studies required and underway for final confirmation

p
p
D
=0
Similar to define perturbatively the Landau gauge by  
●
●
Describing Gluons/Axel Maas
Slides left: 38 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Constructing a global gauge condition
●
●
[Maas, unpublished, Maas, 2008/9, Fischer et al. 2008]
Effects will be strongest at the most non-perturbative
momenta: The infrared
Choose the renormalization-group invariant B=G(0)/G(P)
with P large fixed as a second gauge parameter
●
Fourier-transform at low momentum: Highly non-local
●
Appears to be also working in the continuum and infinite volume
More studies required and underway for final confirmation

p
p
D
=0
Similar to define perturbatively the Landau gauge by  
●
●
●
Would provide an unambiguous definition of the gauge
●
Resolves the Gribov ambiguity
Describing Gluons/Axel Maas
Slides left: 38 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of technicalities
●
Unambiguous description of elementary particles
requires gauge-fixing
Describing Gluons/Axel Maas
Slides left: 37 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of technicalities
●
●
Unambiguous description of elementary particles
requires gauge-fixing
Non-perturbatively this requires additional non-local
conditions
Describing Gluons/Axel Maas
Slides left: 37 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of technicalities
●
●
●
Unambiguous description of elementary particles
requires gauge-fixing
Non-perturbatively this requires additional non-local
conditions
It appears that additional conditions on one
correlation function is sufficient
Describing Gluons/Axel Maas
Slides left: 37 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of technicalities
●
●
●
●
Unambiguous description of elementary particles
requires gauge-fixing
Non-perturbatively this requires additional non-local
conditions
It appears that additional conditions on one
correlation function is sufficient
Provides the basis to calculate non-perturbatively
correlation functions
Describing Gluons/Axel Maas
Slides left: 37 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Describing Gluons/Axel Maas
Methods
Slides left: 36 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Methods
●
Lattice
Describing Gluons/Axel Maas
Slides left: 35 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Lattice calculations
●
Take a finite volume – usually a hypercube
Describing Gluons/Axel Maas
Slides left: 34 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Lattice calculations
●
Take a finite volume – usually a hypercube
●
Discretize it, and get a finite, hypercubic lattice
Describing Gluons/Axel Maas
Slides left: 34 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Lattice calculations
●
Take a finite volume – usually a hypercube
●
Discretize it, and get a finite, hypercubic lattice
●
Calculate observables using path integration
●
d
c c =∫ dAd c dc c c exp−∫ d x L
●
Can be done numerically
●
Uses Monte-Carlo methods
Describing Gluons/Axel Maas
Slides left: 34 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Lattice calculations
●
Take a finite volume – usually a hypercube
●
Discretize it, and get a finite, hypercubic lattice
●
Calculate observables using path integration
●
●
d
 c c =∫ dAd c dc c c exp −∫ d x L
●
Can be done numerically
●
Uses Monte-Carlo methods
Artifacts
●
Finite volume/discretization
Describing Gluons/Axel Maas
Slides left: 34 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Lattice calculations
●
Take a finite volume – usually a hypercube
●
Discretize it, and get a finite, hypercubic lattice
●
Calculate observables using path integration
●
●
d
 c c =∫ dAd c dc c c exp −∫ d x L
●
Can be done numerically
●
Uses Monte-Carlo methods
Artifacts
●
Finite volume/discretization
●
Masses vs. wave-lengths
Describing Gluons/Axel Maas
Slides left: 34 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Methods
●
Lattice
●
Discretize space-time in a box and calculate the path-integral and
expectation values explicitly
●
Full non-perturbative dynamics correctly implemented
●
Finite volume artifacts, disparate scales most severe obstacles
Describing Gluons/Axel Maas
Slides left: 33 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Methods
●
Lattice
●
●
Discretize space-time in a box and calculate the path-integral and
expectation values explicitly
●
Full non-perturbative dynamics correctly implemented
●
Finite volume artifacts, disparate scales most severe obstacles
Functional methods (DSE, RGE...)
Describing Gluons/Axel Maas
Slides left: 33 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Truncated) Dyson-Schwinger Equations (DSEs)
1
2
= p ∫ dq p  c cq A  A  p−q A  c c p , q
c c p
Describing Gluons/Axel Maas
Slides left: 32 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Truncated) Dyson-Schwinger Equations (DSEs)
1
2
= p ∫ dq p  c cq A  A  p−q A  c c p , q
c c p
●
Infinite set of coupled non-linear integral equations
Describing Gluons/Axel Maas
Slides left: 32 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Truncated) Dyson-Schwinger Equations (DSEs)
1
2
= p ∫ dq p  c cq A  A  p−q A  c c p , q
c c p
●
Infinite set of coupled non-linear integral equations
Describing Gluons/Axel Maas
Slides left: 32 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Truncated) Dyson-Schwinger Equations (DSEs)
1
2
= p ∫ dq p c cq A  A  p−q A  c c p , q
c c p
Infinite set of coupled non-linear integral equations
● Generate also perturbation theory
●
Describing Gluons/Axel Maas
Slides left: 32 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Truncated) Dyson-Schwinger Equations (DSEs)
Infinite set of coupled non-linear integral equations
● Generate also perturbation theory
●
Describing Gluons/Axel Maas
Slides left: 32 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
(Truncated) Dyson-Schwinger Equations (DSEs)
Infinite set of coupled non-linear integral equations
● Generate also perturbation theory
● Similar: Renormalization group equations (RGEs)
●
Describing Gluons/Axel Maas
Slides left: 32 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Truncations
●
[Fischer et al., 2008]
Solving the equations at all momenta requires input from the higher vertex
equations
Describing Gluons/Axel Maas
Slides left: 31 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Truncations
●
●
[Fischer et al., 2008]
Solving the equations at all momenta requires input from the higher vertex
equations
Requires truncations, in particular dropping of equations for many-legged
correlation functions [Fischer et al., 2008]
Describing Gluons/Axel Maas
Slides left: 31 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Truncations
●
●
●
[Fischer et al., 2008]
Solving the equations at all momenta requires input from the higher vertex
equations
Requires truncations, in particular dropping of equations for many-legged
correlation functions [Fischer et al., 2008]
Consistent and self-consistent truncation schemes can be developed
Describing Gluons/Axel Maas
Slides left: 31 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Truncations
●
●
●
[Fischer et al., 2008]
Solving the equations at all momenta requires input from the higher vertex
equations
Requires truncations, in particular dropping of equations for many-legged
correlation functions [Fischer et al., 2008]
Consistent and self-consistent truncation schemes can be developed
●
Preserve renormalization and perturbation theory
Describing Gluons/Axel Maas
Slides left: 31 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Truncations
●
●
●
[Fischer et al., 2008]
Solving the equations at all momenta requires input from the higher vertex
equations
Requires truncations, in particular dropping of equations for many-legged
correlation functions [Fischer et al., 2008]
Consistent and self-consistent truncation schemes can be developed
●
Preserve renormalization and perturbation theory
●
Introduces artifacts due to the violation of Slavnov-Taylor identities
●
●
Cannot be avoided, at best these can be closed self-consistenly
●
Not worse than in perturbation theory
Landau gauge is very advantageous, as such violations do not couple back
●
Only transverse contributions are coupled
Describing Gluons/Axel Maas
Slides left: 31 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Truncations
●
●
●
[Fischer et al., 2008]
Solving the equations at all momenta requires input from the higher vertex
equations
Requires truncations, in particular dropping of equations for many-legged
correlation functions [Fischer et al., 2008]
Consistent and self-consistent truncation schemes can be developed
●
Preserve renormalization and perturbation theory
●
Introduces artifacts due to the violation of Slavnov-Taylor identities
●
●
Cannot be avoided, at best these can be closed self-consistenly
●
Not worse than in perturbation theory
Landau gauge is very advantageous, as such violations do not couple back
●
●
Only transverse contributions are coupled
Still other artifacts remain
Describing Gluons/Axel Maas
Slides left: 31 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of methods
●
Lattice
●
●
Discretize space-time in a box and calculate the path-integral and
expectation values explicitly
●
Full non-perturbative dynamics correctly implemented
●
Finite volume artifacts, disparate scales most severe obstacles
Functional methods (DSE, RGE...)
●
Coupled non-linear integral equations must be solved
●
Requires (often completely uncontrolled) approximations
●
Continuum, partly analytical in the far infrared
Describing Gluons/Axel Maas
Slides left: 30 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of methods
●
Lattice
●
●
●
Discretize space-time in a box and calculate the path-integral and
expectation values explicitly
●
Full non-perturbative dynamics correctly implemented
●
Finite volume artifacts, disparate scales most severe obstacles
Functional methods (DSE, RGE...)
●
Coupled non-linear integral equations must be solved
●
Requires (often completely uncontrolled) approximations
●
Continuum, partly analytical in the far infrared
Perturbation theory included as limiting case at high energies
Describing Gluons/Axel Maas
Slides left: 30 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of methods
●
Lattice
●
●
Discretize space-time in a box and calculate the path-integral and
expectation values explicitly
●
Full non-perturbative dynamics correctly implemented
●
Finite volume artifacts, disparate scales most severe obstacles
Functional methods (DSE, RGE...)
●
Coupled non-linear integral equations must be solved
●
Requires (often completely uncontrolled) approximations
●
Continuum, partly analytical in the far infrared
●
Perturbation theory included as limiting case at high energies
●
Combination of all methods most successful!
Describing Gluons/Axel Maas
Slides left: 30 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Properties of gluons
Nb: The results depend little on the number of dimensions
but the lattice can reach larger volumes in lower dimensions
Results shown are therefore mixed from
3 and 4 dimensions, but are qualitatively very similar in both
Describing Gluons/Axel Maas
Slides left: 29 (in this section: 12)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Ghost propagator from the lattice
[Maas, 2009]
●
Results from lattice calculations
●
Different gauge choices yield different propagators
●
Lattice artifacts still to be studied
Describing Gluons/Axel Maas
Slides left: 28 (in this section: 11)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Ghost dressing function in the continuum
●
[Fischer, et al.i, 2008]
Corresponding results from functional methods (Dyson-Schwinger
equations (DSEs))
●
One-to-one-correspondence of lattice and continuum methods
●
Scaling: Divergent, Decoupling: Finite dressing function
Describing Gluons/Axel Maas
Slides left: 27 (in this section: 10)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Gluon dressing function in the continuum
●
●
[Fischer et al., 2008]
Decoupling gauges yield a decoupling (infrared massive)
gluon propagator
The scaling gauge yields an infrared vanishing gluon
propagator
Describing Gluons/Axel Maas
Slides left: 26 (in this section: 9)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Method comparison
[Maas et al. 2004, Maas 2008]
●
Perturbation theory recovered
●
Combination confirm assumption for functional equations
●
Extrapolation of lattice results by functional methods
●
Disadvantage cancellation
Describing Gluons/Axel Maas
Slides left: 25 (in this section: 8)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
Describing Gluons/Axel Maas
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
●
Propagator determines spectral function
2
spectral function q 
Propagator=One particle part∫ dq
2
2
p q
Describing Gluons/Axel Maas
2
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
●
Propagator determines spectral function
spectral function q 
Propagator=One particle part∫ dq
2
2
p q
Gluon propagator vanishes at zero momentum in scaling gauge
2
●
2
Describing Gluons/Axel Maas
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
●
Propagator determines spectral function
spectral function q 
Propagator=One particle part∫ dq
2
2
p q
Gluon propagator vanishes at zero momentum in scaling gauge
2
●
●
2
Gluon not part of the physical sub-space!
Describing Gluons/Axel Maas
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
●
Propagator determines spectral function
spectral function q 
Propagator=One particle part∫ dq
2
2
p q
Gluon propagator vanishes at zero momentum in scaling gauge
2
●
2
●
Gluon not part of the physical sub-space!
●
Also shown in decoupling gauges
Describing Gluons/Axel Maas
[Fischer et al., 2008, Cucchieri et al. 2004]
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
●
Propagator determines spectral function
2
spectral function q 
Propagator=One particle part∫ dq
2
2
p q
Gluon propagator vanishes at zero momentum in scaling gauge
2
●
●
Gluon not part of the physical sub-space!
●
Also shown in decoupling gauges
●
Can be extended to Wilson criteria for quark
Describing Gluons/Axel Maas
[Fischer et al., 2008, Cucchieri et al. 2004]
[Braun et al., 2007]
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Absence of the gluon from the physical spectrum
●
[Zwanziger, 1994-2009]
Gluon propagator violates positivity
●
Propagator determines spectral function
2
spectral function q 
Propagator=One particle part∫ dq
2
2
p q
Gluon propagator vanishes at zero momentum in scaling gauge
2
●
●
Gluon not part of the physical sub-space!
●
Also shown in decoupling gauges
●
Can be extended to Wilson criteria for quark
●
(Possibly) to all colored states using Kugo-Ojima construction
●
[Fischer et al., 2008, Cucchieri et al. 2004]
[Braun et al., 2007]
Uses the Neuberger-von Smekal BRST construction
[Neuberger 1986, von Smekal 2006-2009, Pawlowski et al., 2008]
Describing Gluons/Axel Maas
Slides left: 24 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Analytic structure
●
Vanishing D(0): Gluons do not propagate on the light-cone
Describing Gluons/Axel Maas
Slides left: 23 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Analytic structure
[Alkofer et al. 2003, Fischer et al. 2008]
●
Vanishing D(0): Gluons do not propagate on the light-cone
●
Schwinger function shows no pole mass for the gluon
●
Even when a screening mass exists
Describing Gluons/Axel Maas
Slides left: 23 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Analytic structure
[Alkofer et al. 2003, Fischer et al. 2008]
●
Vanishing D(0): Gluons do not propagate on the light-cone
●
Schwinger function shows no pole mass for the gluon
●
●
Even when a screening mass exists
Analytic structure: Cut along the time-like axis from 0
Describing Gluons/Axel Maas
Slides left: 23 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Interactions of gluons
Describing Gluons/Axel Maas
Slides left: 22 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Interactions of gluons
●
Example: Three-gluon vertex
●
Other: Ghost-gluon vertex,
4-gluon vertex, scattering kernels...
Describing Gluons/Axel Maas
Slides left: 22 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Interactions of gluons
●
Example: Three-gluon vertex
●
●
Other: Ghost-gluon vertex,
4-gluon vertex, scattering kernels...
Correlation function
Describing Gluons/Axel Maas
a

b

c

A A A 
Slides left: 22 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Interactions of gluons
●
Example: Three-gluon vertex
●
Other: Ghost-gluon vertex,
4-gluon vertex, scattering kernels...
a

b

a
b
c

●
Correlation function
A A A 
●
Related to the vertex
 A A  A  = D   D  D      
Describing Gluons/Axel Maas
c
ad
be
cf
de f
Slides left: 22 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Interactions of gluons
●
Example: Three-gluon vertex
●
●
Other: Ghost-gluon vertex,
4-gluon vertex, scattering kernels...
a

b

a
b
c

●
Correlation function
A A A 
●
Related to the vertex
 A A  A  = D   D  D      
c
ad
be
cf
de f
Relevant for
●
Bound states
Describing Gluons/Axel Maas
Slides left: 22 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Interactions of gluons
●
Example: Three-gluon vertex
●
●
Other: Ghost-gluon vertex,
4-gluon vertex, scattering kernels...
a

b

a
b
c

●
Correlation function
A A A 
●
Related to the vertex
 A A  A  = D   D  D      
c
ad
be
cf
de f
Relevant for
●
Bound states
●
Splitting functions
Describing Gluons/Axel Maas
Slides left: 22 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Contractions
●
There are d3 x (Nc2-1)3 tensor components
Describing Gluons/Axel Maas
Slides left: 21 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Contractions
●
There are d3 x (Nc2-1)3 tensor components
●
Landau gauge: All longitudinal ones irrelevant
Describing Gluons/Axel Maas
Slides left: 21 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Contractions
●
There are d3 x (Nc2-1)3 tensor components
●
Landau gauge: All longitudinal ones irrelevant
●
Contractions useful
●
Three-gluon vertex
a

b

c

A A A  = D
A3
tl
ad

be

cf

D D 
de f

tl
tl
G =  AAA / DDD  
Describing Gluons/Axel Maas
Slides left: 21 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Contractions
●
There are d3 x (Nc2-1)3 tensor components
●
Landau gauge: All longitudinal ones irrelevant
●
Contractions useful
●
Three-gluon vertex
a

b

c

A A A  = D
A3
●
●
tl
ad

be

cf

D D 
de f

tl
tl
G =  AAA / DDD  
Measures the deviation from the tree-level vertex
Appears in the gluon one-loop self-energy
Describing Gluons/Axel Maas
Slides left: 21 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Three-gluon vertex
●
●
[Cucchieri et al. 2008]
No emission around hadronic energy scales!
Infrared enhanced: Strong emission of (non-propagating)
gluons on the light-cone
Describing Gluons/Axel Maas
Slides left: 20 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Running coupling
●
Possible to extract a running coupling
Describing Gluons/Axel Maas
Slides left: 19 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Running coupling
●
[Alkofer et al. 1997, Fischer et al. 2008]
Possible to extract a running coupling
●
IR fixed point for scaling gauge
●
IR vanishing for decoupling gauge
Describing Gluons/Axel Maas
Slides left: 19 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Running coupling
●
●
[Alkofer et al. 1997, Fischer et al. 2008]
Possible to extract a running coupling
●
IR fixed point for scaling gauge
●
IR vanishing for decoupling gauge
Known in the perturbative domain up to four loops
[Sternbeck et al. 2008]
Describing Gluons/Axel Maas
Slides left: 19 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Infrared properties in the scaling gauge
●
DSEs and RGEs deliver a qualitative asymptotic infrared solution for all
correlation functions and all dimensions [Alkofer et al., 2005, Fischer et al. 2007/9]
Describing Gluons/Axel Maas
Slides left: 18 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Infrared properties in the scaling gauge
●
DSEs and RGEs deliver a qualitative asymptotic infrared solution for all
correlation functions and all dimensions [Alkofer et al., 2005, Fischer et al. 2007/9]
●
Power-laws. Simplest case: All momenta equal and m gluon and n
ghost legs in d dimensions:
●
●
●

n ghost
n
d
−m gluon 1− ghost  −2
2
2
2
[Alkofer et al. 2006, Huber at al. 2008]
p
Analytic solution without truncation
It is the only power-law-like solution
Describing Gluons/Axel Maas
[Fischer et al. 2007/9]
Slides left: 18 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Infrared properties in the scaling gauge
●
DSEs and RGEs deliver a qualitative asymptotic infrared solution for all
correlation functions and all dimensions [Alkofer et al., 2005, Fischer et al. 2007/9]
●
Power-laws. Simplest case: All momenta equal and m gluon and n
ghost legs in d dimensions:
●
●
●
●

n ghost
n
d
−m gluon 1− ghost  −2
2
2
2
[Alkofer et al. 2006, Huber at al. 2008]
p
Analytic solution without truncation
It is the only power-law-like solution
[Fischer et al. 2007/9]
Truncated DSEs give quantitative predictions for the exponent 
[Zwanziger, 2002, Lerche et al. 2002]
Describing Gluons/Axel Maas
Slides left: 18 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Infrared properties in the scaling gauge
●
DSEs and RGEs deliver a qualitative asymptotic infrared solution for all
correlation functions and all dimensions [Alkofer et al., 2005, Fischer et al. 2007/9]
●
Power-laws. Simplest case: All momenta equal and m gluon and n
ghost legs in d dimensions:
●
●
●
●

n ghost
n
d
−m gluon 1− ghost  −2
2
2
2
[Alkofer et al. 2006, Huber at al. 2008]
p
Analytic solution without truncation
It is the only power-law-like solution
[Fischer et al. 2007/9]
Truncated DSEs give quantitative predictions for the exponent 
[Zwanziger, 2002, Lerche et al. 2002]
●
In particular: IR-vanishing gluon propagator, IR-enhanced ghost
propagator
Describing Gluons/Axel Maas
Slides left: 18 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Infrared properties in the scaling gauge
●
DSEs and RGEs deliver a qualitative asymptotic infrared solution for all
correlation functions and all dimensions [Alkofer et al., 2005, Fischer et al. 2007/9]
●
Power-laws. Simplest case: All momenta equal and m gluon and n
ghost legs in d dimensions:
●
●
●
●

n ghost
n
d
−m gluon 1− ghost  −2
2
2
2
[Alkofer et al. 2006, Huber at al. 2008]
p
Analytic solution without truncation
It is the only power-law-like solution
[Fischer et al. 2007/9]
Truncated DSEs give quantitative predictions for the exponent 
[Zwanziger, 2002, Lerche et al. 2002]
●
●
In particular: IR-vanishing gluon propagator, IR-enhanced ghost
propagator
Can be expanded to the case with matter fields [Alkofer et al., 2007/8]
Describing Gluons/Axel Maas
Slides left: 18 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of gluon properties
●
●
Gluonic correlation functions can be determined with
the combination of methods
Gluon correlation functions depend on the gauge
choice
Describing Gluons/Axel Maas
Slides left: 17 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of gluon properties
●
●
●
Gluonic correlation functions can be determined with
the combination of methods
Gluon correlation functions depend on the gauge
choice
There is no pole mass for the gluon
●
Non-trivial analytic structure
Describing Gluons/Axel Maas
Slides left: 17 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of gluon properties
●
●
●
Gluonic correlation functions can be determined with
the combination of methods
Gluon correlation functions depend on the gauge
choice
There is no pole mass for the gluon
●
●
●
Non-trivial analytic structure
Gluon splitting and propagation together suppress
gluon emission at low energies
Confinement of gluons is manifest
Describing Gluons/Axel Maas
Slides left: 17 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Describing Gluons/Axel Maas
Matter
Slides left: 16 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype – very technical
➔Simple matter particles – scalar
Describing Gluons/Axel Maas
u
g
Slides left: 15 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Matter fields
●
Scalar matter
1

 1

2

L=− F  F −  D  D m −c ∂ D  c
4
2
a a
 R
D =∂−ieA 
●
R denotes the representation
●
Fundamental: Like quarks - Adjoint: Like gluons
Describing Gluons/Axel Maas
Slides left: 14 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Scalar matter
●
Simpelst case: Scalar matter
Describing Gluons/Axel Maas
Slides left: 13 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Scalar matter
●
Simpelst case: Scalar matter
●
Consider scalar in the confinement phase (quenched)
●
Here: Fundamental (like Higgs) charged
Describing Gluons/Axel Maas
Slides left: 13 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Scalar matter
●
Simpelst case: Scalar matter
●
Consider scalar in the confinement phase (quenched)
●
●
Here: Fundamental (like Higgs) charged
Propagator H ij  x − y = i  x  j  y
Describing Gluons/Axel Maas
Slides left: 13 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Scalar matter
●
Simpelst case: Scalar matter
●
Consider scalar in the confinement phase (quenched)
●
Here: Fundamental (like Higgs) charged
●
Propagator H ij  x − y = i  x  j  y
●
(Simplest) Vertex
Describing Gluons/Axel Maas
a


i
 A   j
G

A 
tl

tl
tl
=  A   / DHH  
Slides left: 13 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Scalar proagator
●
1 GeV tree-level mass – effective mass is 1.6 GeV
●
●
[Maas, unpublished]
Dynamical mass generation, independent of tree-level mass
Analytic structure requires more data
Describing Gluons/Axel Maas
Slides left: 12 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Scalar-gluon vertex
[Maas, unpublished]
●
Almost no difference to tree-level
●
Low-momentum behavior mass-dependent
●
Suppression for small masses
Describing Gluons/Axel Maas
Slides left: 11 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of matter
●
Matter fields can also be accessed
●
More complicated than the gauge fields
Describing Gluons/Axel Maas
Slides left: 10 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of matter
●
Matter fields can also be accessed
●
More complicated than the gauge fields
●
More affected by than affecting the dynamics
Describing Gluons/Axel Maas
Slides left: 10 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary of matter
●
Matter fields can also be accessed
●
More complicated than the gauge fields
●
More affected by than affecting the dynamics
●
Dynamical generation of mass observed
Describing Gluons/Axel Maas
Slides left: 10 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Describing Gluons/Axel Maas
Outlook
Slides left: 9 (in this section: 8)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype – very technical
➔Simple matter particles – fermions, scalar
Describing Gluons/Axel Maas
u
g
Slides left: 8 (in this section: 7)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Matter fields
●
Scalar matter
1

 1

2

L=− F  F −  D  D m −c ∂ D  c
4
2
a a
 R
D =∂−ieA 
●
R denotes the representation
●
●
Fundamental: Like quarks - Adjoint: Like gluons
Fermionic matter
1 a  , a

a 
ab b
L=− F  F
iD   −m− c ∂ D  c
4
Describing Gluons/Axel Maas
Slides left: 8 (in this section: 7)
¿
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Fermionic matter
●
Quark propagator
Describing Gluons/Axel Maas
Slides left: 7 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Fermionic matter
●
Quark propagator
−1
S  p= A  p
●
M mass function
●
A-1 wave function renormalization
Describing Gluons/Axel Maas
 p  M  p
2
p M
2
Slides left: 7 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Fermionic matter
●
Quark propagator
−1
S  p= A  p
 p  M  p
2
p M
●
M mass function
●
A-1 wave function renormalization
●
Zero mass: mass function zero perturbatively
Describing Gluons/Axel Maas
2
Slides left: 7 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Fermionic matter
Quark propagator
−1
S  p= A  p
 p  M  p
2
p M
●
M mass function
●
A-1 wave function renormalization
●
Zero mass: mass function zero perturbatively
●
2
Non-zero for generated mass (by QCD and the Higgs)
Mass
●
100%
80%
60%
Strong
Higgs
40%
20%
0%
Describing Gluons/Axel Maas
u
d
s
c
b
t
Leptons
Slides left: 7 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Fermionic matter
Quark propagator
−1
S  p= A  p
 p  M  p
2
p M
●
M mass function
●
A-1 wave function renormalization
●
Zero mass: mass function zero perturbatively
●
2
Non-zero for generated mass (by QCD and the Higgs)
Mass
●
100%
80%
60%
Strong
Higgs
40%
20%
0%
●
u
d
s
c
b
t
Leptons
Measure: trS
Describing Gluons/Axel Maas
Slides left: 7 (in this section: 6)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Quarks
[DSE: Fischer et al., 2003
Lattice: Overlap: Bonnet et al 2003, Asqtad: Bowman et al., 2005]
Quark mass function
Dynamical mass generation observed
●
Describing Gluons/Axel Maas
Slides left: 6 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Quarks
Quark mass function
[DSE: Fischer et al., 2003
Lattice: Overlap: Bonnet et al 2003, Asqtad: Bowman et al., 2005]
Quark wave function renormalization
Dynamical mass generation observed
●Yang-Mills Sector (almost) unaffected (for not too many light quarks)
●
Describing Gluons/Axel Maas
Slides left: 6 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Quarks
Quark mass function
[DSE: Fischer et al., 2003
Lattice: Overlap: Bonnet et al 2003, Asqtad: Bowman et al., 2005]
Quark wave function renormalization
Dynamical mass generation observed
●Yang-Mills Sector (almost) unaffected (for not too many light quarks)
●Analytical structure and vertices very complicated
●
Describing Gluons/Axel Maas
Slides left: 6 (in this section: 5)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype – very technical
➔Simple matter particles – fermions, scalar
u
g
➔Bound states
Describing Gluons/Axel Maas
Slides left: 5 (in this section: 4)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Bound states
●
Can be extended to bound-state calculations
Describing Gluons/Axel Maas
Slides left: 4 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Bound states
●
Can be extended to bound-state calculations
●
Lattice calculations – hard to reach physical mass
●
Functional equations – requires assumptions
Describing Gluons/Axel Maas
Slides left: 4 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Bound states
[Eichmann et al., 2009, PDG
2009, Aoki et al . 2009]
Mass
2000
1800
1600
1400
1200
1000
800
600
400
Nucleon
Rho
200
Delta
0
E xp
L a tti c e
Fu n c
●
Fu n c
E xp
E xp
L a tti c e
L a tti c e
Fu n c
Can be extended to bound-state calculations
●
Lattice calculations – hard to reach physical mass
●
Functional equations – requires assumptions
Describing Gluons/Axel Maas
Slides left: 4 (in this section: 3)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
What is required?
●
A unified framework covering all aspects
●
●
Must include perturbation theory for systematic control
Construct it step-by-step
✔ Basic entities: Force particles (gluons,...)
g
✔ Yang-Mills theory as a prototype – very technical
➔Simple matter particles – fermions, scalar
u
g
➔Bound states and the phase diagram
Describing Gluons/Axel Maas
Slides left: 3 (in this section: 2)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Finite temperature
Describing Gluons/Axel Maas
Slides left: 2 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Finite temperature
●
QCD Phase transition
Describing Gluons/Axel Maas
Slides left: 2 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Finite temperature
●
QCD Phase transition
Describing Gluons/Axel Maas
Slides left: 2 (in this section: 1)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Finite temperature
●
[Maas, 2009]
QCD Phase transition can be observed in some of the
gluon propagator tensor components
Describing Gluons/Axel Maas
Slides left: 1 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Finite temperature
●
●
[Left: Maas, 2009
Right: Fischer et al., 2009]
QCD Phase transition can be observed in some of the
gluon propagator tensor components
Reflected in trS of the quark propagator
Describing Gluons/Axel Maas
Slides left: 1 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary
●
Correlation functions contain all information
●
Masses, widths, couplings, interactions, bound states,...
Describing Gluons/Axel Maas
Slides left: 0 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary
●
Correlation functions contain all information
●
●
Masses, widths, couplings, interactions, bound states,...
Determination in the non-perturbative domain hard
●
Requires a combination of methods for systematic control
Describing Gluons/Axel Maas
Slides left: 0 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary
●
Correlation functions contain all information
●
●
Determination in the non-perturbative domain hard
●
●
Masses, widths, couplings, interactions, bound states,...
Requires a combination of methods for systematic control
Successful applications in QCD
●
Confinement, QCD phase diagram, hadrons
Describing Gluons/Axel Maas
Slides left: 0 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary
●
Correlation functions contain all information
●
●
Determination in the non-perturbative domain hard
●
●
Requires a combination of methods for systematic control
Successful applications in QCD
●
●
Masses, widths, couplings, interactions, bound states,...
Confinement, QCD phase diagram, hadrons
Going to the standard model...
Describing Gluons/Axel Maas
Slides left: 0 (in this section: 0)
Introduction – Gauge fixing – Methods – Gluons – Matter – Outlook
Summary
●
Correlation functions contain all information
●
●
Determination in the non-perturbative domain hard
●
●
Requires a combination of methods for systematic control
Successful applications in QCD
●
●
Masses, widths, couplings, interactions, bound states,...
Confinement, QCD phase diagram, hadrons
Going to the standard model...and beyond
●
Applicable to any field theory
●
Applications eg to supersymmetry
Describing Gluons/Axel Maas
lWipf et al., 2009]
Slides left: 0 (in this section: 0)