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The Little Big Bang:
Relativistic Nuclear Collisions
12
and the Physics at 10 K
Nathan Grau
Columbia University, Nevis Laboratories
Francis Marion University
01/22/2009
1
Outline


Top-down introduction to high energy physics
and the Quark-Gluon Plasma
The Quark-Gluon Plasma now


What we know now from the Relativistic Heavy
Ion Collider (RHIC)
The Quark-Gluon Plasma in the future

What we are learning and will learn from the
Large Hadron Collider, string theory, and trapping
supercold atoms
Francis Marion University
01/22/2009
2
Introduction and Background of High
Energy Physics
WARNING!
The units you are about to see and hear are “natural”
c = hbar = kB = 1
Energy in GeV, momentum GeV/c (p~mc),
mass in GeV/c2 (E=mc2)
Some important numbers to set a scale:
Proton mass = 1 GeV/c2
170 MeV = 1012 K (E=kBT)
Francis Marion University
01/22/2009
3
The Standard
Model Lagrangian

This is the culmination of
400+ years of physics
research




All current physics data is
explained
Disclaimer: Gravity Not
Included
Still not small enough to fit
on a T-shirt
Good party trick: Ask
where the sign error is
(there really is one!)
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01/22/2009
4
The Standard Model Condensed

The particles (fields)



12 particles
4 force carriers
Their interactions
are the fundamental
forces of nature…
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01/22/2009
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Fundamental Forces: Electroweak
Computer
Chip

1/2 Electroweak Force =
Electricity and Magnetism


Everything from transistors in
computers to wind is governed
by this force
Actually a single force:
Electromagnetic force
Interaction of two charged
entities
 Theory: Quantum
Electrodynamics (QED)

Hurricane Katrina
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01/22/2009
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Fundamental Forces: Electroweak
p p
p p

1/2 Electroweak Force =
Weak Force

interaction of two “weakly”
charged particles


light
It is why the sun shines.
In the first part of the chain the
proton turns into a neutron.
He
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01/22/2009
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Fundamental Forces: Strong Force

Quarks combine to form
other particles




Baryons (qqq): protons,
neutrons, etc.
Mesons(qq): pions, kaons,
etc.
Held together by gluons
proton
neutron
g
g
g
g
g
g
Quark charge is “color” of
3 types: red, green, blue


Contrast that with 2 electric
charges: +,Hadrons are color neutral =
white
Francis Marion University
01/22/2009
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Fundamental Forces: Strong Force

Quarks combine to form
other particles




neutron
g
g
g
g
g
g
Quark charge is “color” of
3 types: red, green, blue



Baryons (qqq): protons,
neutrons, etc.
Mesons(qq): pions, kaons,
etc.
Held together by gluons
proton
Contrast that with 2 electric
charges: +,Hadrons are color neutral =
white
Theory: Quantum
Chromodynamics (QCD)
Francis Marion University
01/22/2009
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Fundamental Forces: Strong Force

Quarks combine to form
other particles




Quark charge is “color” of
3 types: red, green, blue



Baryons (qqq): protons,
neutrons, etc.
Mesons(qq): pions, kaons,
etc.
Held together by gluons
Contrast that with 2 electric
charges: +,Hadrons are color neutral =
white
proton
neutron
g
g
g
g
g
g
Ca. 1970 view of the proton
and the neutron.
Only real improvement is that
the proton bubbles with lots of
gluons and qq pairs
Theory: Quantum
Chromodynamics (QCD)
Francis Marion University
01/22/2009

10
Proton Structure
d
g
d
qq
g
g

u
u
u
u

qq
g

Proton at two instances in time
The interior bubbles with qq pairs and gluons
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01/22/2009
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Proton Structure



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01/22/2009
Probability of
finding a gluon or
quark of a given
flavor with
momentum
fraction x = pq/pp
u, d = valence
near x~10-1
s,c,b,g = sea
12
Fundamental Forces: Strong Force



Strong force also binds nuclei
Clearly needed another nuclear force since an
electrically neutral neutron could not bind with a
positive proton via electromagnetic force
In fact, individual proton and
neutron definitions are
blurred by quantum
mechanics

Nucleus is a bag of quarks and
gluons
Francis Marion University
01/22/2009
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Confinement
Quarks and gluons are
confined - no evidence of
their existence outside of
(colorless) hadrons
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01/22/2009
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The Quark-Gluon Plasma: Unbinding
the Bound
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01/22/2009
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The History of the Universe
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01/22/2009
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Francis Marion University
01/22/2009
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The Quark-Gluon Plasma

The state of the universe before it cooled to allow
hadrons (protons, neutrons, etc.) to form

t < 1 s after the Big Bang


T > 1012 K




Hence part of my title
Hence the other part of my title
R < 1 fm = size of the proton
It is a different state of matter than what exists today
Can we reproduce it in a laboratory?

Allow a direct study of the strong interaction which is 1/2 of
the Standard Model.
Francis Marion University
01/22/2009
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QCD Phase Diagram

A beginning
definition: A hot,
dense state of
weakly-interacting
quarks and gluons
over a distance
greater than the
size of the proton.
Quark-Antiquark imbalance
Francis Marion University
01/22/2009
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QCD Phase Diagram


A beginning
definition: A hot,
dense state of
weakly-interacting
quarks and gluons
over a distance
greater than the
size of the proton.
Expected to occur
at 1012K~170 MeV
Quark-Antiquark imbalance
Francis Marion University
01/22/2009
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QCD Phase Diagram


A beginning
definition: A hot,
dense state of
weakly-interacting
quarks and gluons
over a distance
greater than the
size of the proton.
Expected to occur
at 1012K~170 MeV
Quark-Antiquark imbalance
Heavy Ion Collision Trajectory
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01/22/2009
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The Relativistic Heavy Ion Collider
(RHIC) From Space
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01/22/2009
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The Collider From The Air
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01/22/2009
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RHIC Vitals and Statistics
•
•
•
•
Two independent rings 3.83 km in
circumference
–
120 bunches/ring
–
106 ns crossing time
Maximum Energy
–
s½ = 500 GeV p+p
–
s½ = 200 GeV/N-N A+A
Design Luminosity
–
Au+Au 2x1026 cm-2s-1
–
p+p 2x1032 cm-2s-1 ( polarized)
Capable of colliding any nuclear
species on any other nuclear species
•
•
•
•
•
•
•
Collision energy = two mosquitoes
colliding
Collision temperature: over 1 trillion
degrees
Over 35,500 kg (78,100 pounds) of
helium
Ring cooled to 4.6 Kelvin (-450
degrees F)
Refrigerator uses 15 MW electricity
20 years, less than one gram of gold is
used
Quark-gluon plasma lasts less than
0.00000000000000000000001 seconds
Francis Marion University
01/22/2009
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A Relativistic Heavy Ion Collision

Two nuclei approach
one another




Moving at v=0.9995c so
relativistically contracted
Mostly pass through
one another
Overlap region
converts energy into
heat and particles to
form the QGP
Peripheral collision


Not fully overlapping
See “participants” and
“spectators”
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
Simulations by the Frankfurt
UrQMD Group
Francis Marion University
01/22/2009
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A Relativistic Heavy Ion Collision
Animation by Jeffery Mitchell (Brookhaven National Laboratory). Simulation by the UrQMD Collaboration
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.

QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
Central (head-on) Au+Au Collision
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01/22/2009
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Real Heavy Ion Collisions
STAR
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01/22/2009
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Measuring 



M. Kaneta, N. Xu, nucl-th/0405068 (2004)
If  is the quarkantiquark imbalance
then measure antiparticle/particle
ratios
Compare to a
statistical model of
hadronization
Note the species
measured: K, K*,
p, 
Francis Marion University
01/22/2009
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Measuring 



M. Kaneta, N. Xu, nucl-th/0405068 (2004)
If  is the quarkantiquark imbalance
then measure antiparticle/particle
ratios
Compare to a
statistical model of
hadronization
Note the species
measured: K, K*,
p, 
Francis Marion University
01/22/2009
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Measuring 



M. Kaneta, N. Xu, nucl-th/0405068 (2004)
If  is the quarkantiquark imbalance
then measure antiparticle/particle
ratios
Compare to a
statistical model of
hadronization
Note the species
measured: K, K*,
p, 
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01/22/2009
B~30 MeV
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Measuring T

Look at the
photons

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01/22/2009
Just like
COBE
measures
the CMB
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Measuring T: Photon Spectrum



Yield of photons at
each momentum bin
Dashed line is fit to
p+p data
Extra photons in
Au+Au collisions



Francis Marion University
01/22/2009
exp(-pT/T) with
T = 221+/-23(stat.)+/18(sys.) MeV
Other theoretical
models are yield T from
300-600 MeV
Recall transition at
T~170 MeV
32
Measuring T: Photon Spectrum

Central Au+Au
Non-central Au+Au


Yield of photons at
each momentum bin
Dashed line is fit to
p+p data
Extra photons in
Au+Au collisions



Francis Marion University
01/22/2009
exp(-pT/T) with
T = 221+/-23(stat.)+/18(sys.) MeV
Other theoretical
models are yield T from
300-600 MeV
Recall transition at
T~170 MeV
33
Measuring T: Photon Spectrum

Central Au+Au
Non-central Au+Au


Yield of photons at
each momentum bin
Dashed line is fit to
p+p data
Extra photons in
Au+Au collisions



Francis Marion University
01/22/2009
exp(-pT/T) with
T = 221+/-23(stat.)+/18(sys.) MeV
Other theoretical
models are yield T from
300-600 MeV
Recall transition at
T~170 MeV
34
Intermediate Conclusion


It seems like RHIC has indeed produced the
right conditions to produce a Quark-Gluon
plasma.
But…


Do we know it is thermalized? Is that temperature
from the photons really a temperature.
What about other thermodynamic quantities:
pressure, entropy, etc.? Is there an equation of
state?
Francis Marion University
01/22/2009
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Getting at the Pressure: Elliptic Flow

Non-overlapping
collisions of spherically
symmetric nuclei results
in a non-symetric
overlap region


QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
Differential pressure
gradients if you think in
terms of a fluid.
Use flow to measure
Equation of State and
speed of sound cs
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01/22/2009
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Azimuthal Distributions: v2


Particles have a
harmonic
distribution wrt
the reaction
plane.
v2 related to the
strength of the
modulation

dN N

1 2v 2 cos2   ...

d 2
Francis Marion University
01/22/2009
Dependent on
the particle’s
momentum and
mass
37
Compilation of Light Hadron v2 Data


Everything
flows
Hydrodynamics
fit data at low
momentum

Should not
work at high
momentum
Can add K*,
to this list as
Hydrodynamics = Fluid equations assuming well

An equation of state and thermalization.
Francis Marion University
01/22/2009
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v2 Scaling (I)
baryons
(qqq)
Mesons
(qq)
KE T  mT  m  pT2  m2  m
Francis Marion University
01/22/2009

With more
precise
data
scaling of
baryons
(p,n) and
mesons
(,K)
observed.
39
v2 Scaling (II)

Divide by the
constituent
quarks and a
universal v2
curve exists!



KE T  mT  m  pT2  m2  m
Francis Marion University
01/22/2009
nq=3 for
baryons
nq=2 for
mesons
Can be used
to derive a
speed of
sound: cs =
0.35+/-0.05
40
Heavy Quarks Flow Also!



Several models of
heavy flavor diffusion
through the medium
Francis Marion University
01/22/2009
Heavy
Flavor(HF):
c,b
e
c,b flow as
well!
Like
boulders
flowing in a
small
stream
41
Strongly Interacting Plasma

Hydrodynamic models work




Only works with QGP equation of state (not a hadron gas)
Implies local thermodynamic equilibrium
Have viscosity = 0!
The medium produced is a perfect fluid





Fluid! Not a gas!
Heavy flavors are also strongly coupled to the fluid
Data used to obtain (shear)viscosity/entropy density /s
Light hadron v2 indicates /s ~ 1/4
Heavy hadron v2 indicate /s ~ (1-2)/4
Francis Marion University
01/22/2009
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The Future: The Effects of RHIC and
New Experiments
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01/22/2009
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Should We Have Seen This Coming?


Lattic calculations
(numerically
solving QCD)
indicate a phase
transition
But new phase
doesn’t reach the
Stefan-Boltzmann
limit

QGP  SB
3
4
Francis Marion University
01/22/2009
The limit for noninteracting
paticles.
44
How Can We Make Headway?



If particles are strongly coupled cannot use
perturbative methods to calculate
Need a new tool that can calculate strongly
coupled field theories
Why not use string theory????
Francis Marion University
01/22/2009
45
AdS/CFT Correspondence
5-D Anti-de Sitter
Black Hole


4-D
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
5th dim
Maldecena’s
Conjecture

1) Calculate some
quantities in a 5-D
gravity
Anti-de Sitter (AdS)
defines the General
Relativity metric
Francis Marion University
01/22/2009
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AdS/CFT Correspondence

5-D Anti-de Sitter
Maldecena’s
Conjecture

Black Hole
4-D
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.

5th dim

CFT: scale
invariant field
theory
QCD is not quite
scale invariant

Francis Marion University
01/22/2009
2) Apply a
dictionary to get
analogous
quantity in the
dual conformal
field theory
(CFT)
Shh don’t tell…
47
AdS/CFT Correspondence
4-D
QCD-like,
strongly-coupled
fluid at TQGP
5-D Anti-de Sitter
Black Hole
4-D
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
5th dim
Conformal
boundary
r0~1/TQGP
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01/22/2009
48
What Do Strings Tell Us?

Limit of /s (looks like an uncertainty
relationship)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.

Checked by many different geometries seems universal!
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01/22/2009
49
/s For Physical Substances


QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Nothing comes close to
the physical bound
except the QGP at TC
Recall



Light hadron v2 indicates
/s~1/4
Heavy hadron v2 indicate
/s~(1-2)/4
Most perfect fluid ever
measured in a
laboratory
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01/22/2009
50
New Overlap With Other Fields
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01/22/2009
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New Experiments: Large Hadron
Collider (LHC) 27 km


New, large,
higher-energy
collider just
turning on in
CERN, Geneva
Switzerland.
200 GeV
Au+Au at RHIC
to 5.5 TeV
Pb+Pb at LHC
~100 m
below
ground
5.5 TeV A+A
14 TeV p+p
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01/22/2009
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The ATLAS Detector
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The ATLAS Detector
It floats!
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01/22/2009
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ATLAS vs. RHIC Acceptance
RHIC

Unprecedented coverage to measure HI
Collisions and their properties.
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01/22/2009
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The Last 10 Years
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The Last 10 Years
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01/22/2009
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The Last 10 Years
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01/22/2009
58
The Last 10 Years
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Francis Marion University
01/22/2009
59
The Last 10 Years
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Francis Marion University
01/22/2009
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
60
The Last 10 Years
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
TIFF (Uncompressed) decompressor
are needed to see this picture.
Francis Marion University
01/22/2009
61
The Last 10 Years

Physics Publications in Refereed Journals






BRAHMS - 19
PHENIX - 76
PHOBOS - ??? website down :(
STAR - 86
10s of technical papers
1 “White Paper” after 2003 run summarizing
physics

Before the strongly-interacting QGP
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01/22/2009
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The Last 10 Years



A phase transition in our understanding of the
Quark Gluon Plasma has occurred: it is a
strongly-interacting, perfect fluid!
Insights to calculating non-perturbative QCD
has come from String Theory!
New experiments and overlaps with other
fields will help us learn more about the matter
that dominates the visible universe.
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01/22/2009
63
Backup Slides
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01/22/2009
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The Standard Model Condensed
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01/22/2009
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Fundamental Forces: Strong Force

Quarks combine to form
other particles




Quarks have “color”
charge is of 3 types: red,
green, blue


Baryons: protons,
neutrons, etc.
Mesons: pions, kaons, etc.
Held together by gluons
Contrast that with 2 electric
charges: +,-
Quarks are confined no evidence of their
existence outside of
hadrons
proton
neutron
g
g
g
g
g
g
Ca. 1970 view of the proton
and the neutron.
Only real improvement is that
the proton bubbles with lots of
gluons and qq pairs
Francis Marion University
01/22/2009

66
The Collider From Inside a Detector
Beam View
STAR
dN/d ~ 600
Head-on (central) Au+Au
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01/22/2009
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AdS/CFT : QCD Correspondence



Maldecena’s conjecture
String theory is equivalent to a conformal (scaleinvariant) field theory in a lower dimension without
gravity
Further it has been argued that strongly coupled
field theories can be described by weak string
theories.
Implication: strongly coupled QCD can be calculated
by a gravity dual


Gravity = General Relativity in many dimensions
Lots of work in 5-dimensional Anti-de Sitter (AdS) space this just defines the metric connected with QCD in 4dimensions.
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01/22/2009
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