Probing the Heart of Matter
A/Prof. Anthony G. Williams
CSSM
Adelaide University
22 November 2001, Melbourne
Outline of Talk
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Introduction and Context
Special Research Centre for the Subatomic Structure of Matter
(CSSM)
The Standard Model of Particle Physics
Quantum Chromodynamics (QCD)
Quarks and Gluons and the Origin of 98% of the Mass of Tangible
Matter
Lattice Gauge Theory and Lattice QCD
Orion Supercomputer
Centre for High-Performance Computing and Applications
(CHPCA)
Conclusions and Outlook
Introduction and Context
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Strongly interacting matter makes up almost the entire mass of the
tangible universe, from the protons and neutrons in the nuclei of atoms
and molecules to neutron stars.
The strong interaction fuels the sun and stars and determines which
nuclei are stable and hence which elements can exist.
The underlying theory of the strong interaction is called quantum
chromodynamics (QCD) and has quarks (like electrons) and gluons (like
photons but self-interacting) as its fundamental constituents.
Quarks and gluons are bound so strongly together that they can never
appear as free particles. This is called confinement.
When probed at increasingly higher energies the interaction between
them becomes progressively weaker. This is called asymptotic freedom.
The quarks in your body represent only about 2% of your mass with the
rest of your mass being generated by the strong interaction itself.
The world's fastest supercomputers are being used to improve our
understanding of the strong interaction and the unusual properties of
quarks and gluons.
Concepts
•Strongly interacting matter is referred to as
hadronic matter and strongly interacting
particles are called hadrons, e.g., protons,
neutrons, and pions are all hadrons
•Hadrons with 1/2 integer spin (e.g., 1/2, 3/2,
5/2,…) are fermions and are called baryons.
Protons and neutrons are baryons.
•Hadrons with integer spin (e.g., 0, 1, 2, …) are
bosons and are called mesons. The pion is a
meson.
•Nuclei consist of protons and neutrons bound
together by the strong interaction.
•The elements and hence all of chemistry is
determined by which nuclei are stable.
Boson = Bose-Einstein statistics
Fermion = Fermi-Dirac statistics
Scales
• Typical atomic size is 10-10 m = 1
Angstrom
• Typical nuclear sizes are 10-14 m = 10
fermi
• 1 fermi = 1 fm = 10-15 m
• Proton radius is 0.8 fm,i.e.,
approximately 1 fm
• No substructure of electrons or quarks
has ever been observed at resolutions
down to approximately 1/100,000,000
Angstroms = 10-18 m.
• At the present time we assume that
electrons and quarks are elementary
particles.
Atomic
Structure
• Warning: Sketch not
to scale!
• If the protons and
neutrons in this
nucleus are 10cm
across then
• the nucleus is about
100cm across,
• the electrons and
quarks are less than
0.1mm across,
• and the atom is 10km
across!
Fundamental Forces
There are four fundamental forces which are believed to give rise to all
observed physical phenomena.
• Gravity: holds us to the earth, binds stars, solar systems, galaxies, etc.
• Electromagnetic: e.m. radiation, chemistry hence biology, touch,
electronics, etc.
• Weak: radioactivity, neutrino physics of supernovae, etc.
• Strong: all familiar matter, nuclear energy, powers sun and stars, etc.
Special Research Centre for the Subatomic Structure
of Matter (CSSM)
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The CSSM is a Special Research Centre of the Australian Research Council (ARC)
funded for nine years (since 1997) to carry out theoretical research in subatomic
physics.
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Mission:
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- Make major advances in the understanding of the structure of hadronic matter
- Cross fertilization enhances opportunities for breakthroughs in understanding
- Pursue lattice, models, phenomenology, and strong links to experimental results
- Develop strong international links, exchanges
Personnel:
- High level postgraduate and postdoctoral training
- Interact with best researchers in a stimulating atmosphere
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Service:
- LANL Archive for Australia
- Workshop program (support external students and affiliate staff)
- Stimulate school students to science (brochures, school visits)
- Physics Guru, Public Lectures, Newspapers, radio, Television
CSSM: Current Academic Staff
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Professor Anthony Thomas (Director)
A/Prof. Anthony Williams (Deputy Director)
Dr. P. Coddington
Dr. Alex Kalloniatis (Australian Research Fellow)
Dr. Derek Leinweber
Dr. Andreas Schreiber (Australian Research Fellow)
Dr. Ingo Bojak
Dr. Xin-Heng Guo
Dr. Ayse Kizilersü
Dr. Vadim Guzey
Dr. Martin Oettel (joint appointment Alexander von Humbolt
Stiftung/Foundation & CSSM)
• Dr. Jianbo Zhang
Postgraduate Students
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Sundance Bilson-Thompson (Ph.D.).
Supervisors: D.B. Leinweber & A.G.
Williams
Francois Bissey (Ph.D.). Cotutelle
(U. Blaise Pascal) & A.W. Thomas.
Frederic Bonnet (Ph.D.).
Supervisors: D.B. Leinweber & A.G.
Williams.
Patrick Bowman (Ph.D.).
Supervisors: D.B. Leinweber & A.G.
Williams;
position at Florida State Univ.
Shane Braendler (Ph.D.).
Supervisor: A.W. Thomas
Will Detmold (Ph.D.). Supervisors:
A. Bender & A.W. Thomas
Emily Hackett-Jones (M.Sc.).
Supervisors: D.B. Leinweber &
A.W. Thomas
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Waseem Kamleh (Ph.D.). Supervisor:
A.G. Williams
Daniel Kusterer (M.Sc. BadenWuerttemberg/S.A. Exchange Program)
- Supervisor: D.B. Leinweber
Olivier Leitner (Ph.D.). Cotutelle (U.
Blaise Pascal) & A.W. Thomas
Tom Sizer (Ph.D.). Supervisor: A.G.
Williams
Stewart Wright (Ph.D.). Supervisors:
D.B. Leinweber & A.W. Thomas;
position at Liverpool, UK.
Ross Young (Ph.D.). Supervisors: D.B.
Leinweber & A.W. Thomas
James Zanotti (Ph.D.). Supervisors:
D.B. Leinweber & A.G. Williams
International Collaborative Agreements
 Abdus Salam International Centre for Theoretical Physics - Italy
 Argonne National Laboratory - USA
 Bonn University - Germany
 Chinese Academy of Sciences (Beijing) - China
 Commissariat à l'Energie Atomique - France
 European Centre for Theoretical Studies in Nuclear Physics and Related
Areas (Trento) - Europe
 Indiana University (Bloomington) - USA
 Institute for Nuclear Theory, University of Washington (Seattle) - USA
 Instituto De Fisica Teòrica (IFT-UNESP) - Brazil
 Joint Institute for Nuclear Research (JINR - Dubna) - Russia
 Jülich (FZ) - Germany
International Collaborative Agreements (cont.)
 MESON (Medium Energy Science Open Network) involving IUCF
Indiana; Yonsei, Korea; RCNP Osaka; KVI Groningen; IMP Lanzhou;
TSL Uppsala; NAC Cape Town; SAHA Calcutta; FZ Jülich; CIAE Beijing
 Osaka University - Japan
 Computational Science and Information Technology (CSIT, Florida) USA
 Svedberg Laboratory - Sweden
 Thomas Jefferson National Accelerator Facility (Newport News) - USA
 Technical University of Munich - Germany
 TRIUMF (Vancouver) - Canada
 Université Blaise Pascal - France
 University of Tübingen - Germany
CSSM Workshops/Conferences
2000
• 3rd International Symposium on Symmetries in Subatomic Physics March
Total Number of Participants: 85
Overseas Participants: 45
Interstate Participants: 12
Local Participants: 28
• International Conference on Quark Nuclear Physics - February
Total Number of Participants: 109
Overseas Participants: 75
Interstate Participants: 1
Local Participants: 33
• HallD Workshop - February
Total Number of Participants: 45
Overseas Participants: 24
Interstate Participants: Nil
Local Participants: 21
CSSM Workshops/Conferences 2001
• Lattice Hadron Physics Workshop - July
Total Number of Participants: 42
Overseas Participants: 26
Interstate Participants: 1
Local Participants: 15
• Hamiltonian Lattice Gauge Theories Workshop - April
Total Number of Participants: 19
Overseas Participants: Nil
Interstate Participants: 4
Local Participants: 15
• Leptonic Scattering Workshop - March
Total Number of Participants: 64
Overseas Participants: 35
Local Participants: 29
Visitor Program 2001
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Dr. P. Bowman, Florida, USA
Dr. A. Chian, Sao Paolo, Brazil
Dr. M. Chaichian, Helsinki
Dr. G. Dunne, Connecticut
Dr. Y. Hoshino, Kushiro, Japan
Dr. C.-S. Huang, Beijing, China
Prof. A. Ioannides, RIKEN, Japan
Dr. S. Krewald, Jueilich, Germany
Dr. R. Landau, Oregon, USA
Dr. D. Lu, Zhejiang, China
Prof. W.-X. Ma, Beijing, China
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Dr. K. Maltman, York, Canada
Dr. S. Sharpe, Seattle, USA
Dr. A. Signal, Massey, NZ
Dr. D. Sinclair, Argonne, USA
Prof. J. Speth, Juelich, Germany
Dr. P. Tandy, Ohio, USA
Dr. G. Valencia, Iowa, USA
Prof. M. Veltman, Utrecht
Dr. J. Vergados, Ionnina, Greece
Dr. L. von Smekal, Erlangen
Dr. M. Weyrauch, Bundesanstalt,
Germany
Future Workshops
• Joint Workshop with JHF, March 2002
• The Structure of the Nucleon (Joint with ECT* in Trento),
September 2002
• NUPP Summer School, February 2003
• 2nd Lattice Workshop, Cairns, June/July(?) 2003
The Standard Model
Let us review some
aspects of the standard
model briefly before
beginning to focus on
QCD itself.
The Standard Model: Fermions
• In addition to
the 6 known
flavors of
quarks they
come in 3
“colours”: red,
blue, and green
• “Lepton” comes
from the Greek
for small mass
• Leptons do not
carry color
charge, i.e., they
do not feel the
strong force
The Standard Model: Bosons
• The very massive W-, W+, and Z0 bosons mediate the weak
interaction, which as a result is very short range
• The massless photon mediates the long-range e.m.
interactions
• Gluons carry color and mediate the strong interaction
The Standard Model: Forces
• Gravitons are thought to mediate the gravitational force but
have not yet been seen
• Gravitational waves are to gravitons what e.m. radiation is to
photons
• Above we see the relative strengths and relative ranges of the
four fundamental forces
Standard Model: Sample Processes
Standard model processes and interactions:
• neutron beta decay (neutrons are only stable in nuclei which is
just as well!) - imagine the universe if this was not so ...
• electron-positron annihilation to meson-antimeson pair
• proton-proton collision producing two Z0 bosons and other
hadrons
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Early
Univers
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Free quarks
and gluons
existed until
about 10-5
seconds
atoms formed
at about
300,000 years
stars formed at
about 1 billion
years
solar systems
and life at about
12 billion years
Neutron
Stars
• Different phases of
hadronic matter can
co-exist within a
neutron star.
• For this sample
neutron star, it is
expected that quark
matter becomes a
stable phase 1km
beneath the surface.
• In the central core
quark matter is
dominant.
Neutron Star: Phase vs Density
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Protons and
neutrons are
collectively
referred to as
nucleons
Ordinary nuclear
matter density is
approximately
0.17 nucleons/fm3
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Quantum Chromodynamics (QCD)
All hadrons are color-singlet (“white”):
• Baryons contain three quarks (red +
blue + green) - Different baryons arise
from the three quarks having
different flavor combinations.
• Mesons contain colour + anticolour
combinations of quark and antiquark
•A red quark emitting a
pairs (red + anti-red, green + antired-anti-blue gluon to
green, blue + anti-blue) - Different
leave a blue quark.
mesons arise from different flavor
•The quark flavor (i.e.,
combinations of the pair.
u,d,s,c,b,or t) does not
• Each flavor of quark cycles through
change during this
the three colors by exchanging
process, since gluons
gluons with the other quarks or anticarry no flavor.
quark.
QCD: Nuclear Forces
All hadrons are color-singlet (neutral or colorless or “white”) combinations
of quarks (3 quarks for baryons or quark-antiquark pair for mesons). But
just as electrically neutral atoms interact by van der Waals forces, so can
color neutral particles. This has very important consequences … the
strong nuclear force.
Two protons attract despite their e.m. repulsion …………
stable
nucleus
… leads to
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… and hence to atoms, molecules, chemistry, and all of biology.
QCD: Baryons and Antibaryons
• Baryons are
color-singlet
combinations
of three quarks.
• Anti-baryons
are colorsinglet
combinations
of three antiquarks.
QCD: Mesons
• Mesons are
made up of a
quark - antiquark pair with
equal and
opposite color
charges giving
a color-singlet.
Confinement
• The strong force between two quarks arises from the
exchange of gluons.
• There is also a strong force between two gluons - since they
carry color themselves they can interact with each other.
This is not the case for photons in QED since they carry no
electric charge.
• The force between two quarks is constant, i.e., independent
of their separation. This corresponds to a linearly rising
potential between them, which is referred to as a “string
tension”.
• This force between colored objects is equivalent to a wieight
of approximately 10 tons! - This is why no free quarks or
gluons are ever seen. QCD has the property of
CONFINEMENT.
String Breaking: Quark - Anti-quark
Pairs
“Gluons” are well-named since they lead to
the confinement of color particles - no free
colored objects have EVER been seen in
nature.
What happens when we try to pull apart two
colored objects by pumping more and more energy
into the system, e.g., through energetic collisions
at a particle accelerator?
•When the energy put in is large enough to make a
quark - anti-quark pair, then a meson can be
created and the string is “broken”.
•Confinement survives however as no free color
particles are produced.
Asymptotic Freedom
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ASYMPTOTIC
FREEDOM
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In quantum electrodynamics
(QED) the fine structure
constant is   1/137.
In QCD the coupling “runs”
by decreasing with
increasing energy scale, i.e.,
at short distances.
At the energy scale of the Z0
mass the strong coupling
constant has decreased to a
value s 0.12.
Quarks and gluons appear
almost free at high energies.
At low energies s  1, i.e.,
the coupling is very STRONG
and perturbation theory
fails..
Strong Coupling Constant at Z Mass
• At the energy scale of
the Z0 mass the strong
coupling constant has
decreased to s 0.12.
• This has been confirmed
in a variety of different
experiments with a
remarkable degree of
consistency.
QCD Produces 98% of Your Mass
•Proton mass is 938 MeV = 0.938
GeV.
Where does the rest of the hadron
mass come from?
•Up and down quark masses are
approximately 3 and 6 MeV
respectively.
•The interactions in the low-energy (long-distance) are so strong (i.e.,
non-perturbative) that they induce a mass in the quarks of
approximately 300 MeV. This is referred to as “dynamical mass
generation”. This is how three quarks in a bound state can have a
mass exceeding their naïve sum.
•The fact that the up and down quarks are so light and because of this
mass-generation, Goldstone’s theorem states that there will be nearly
massless Goldstone bosons associated with the spontaneous
breaking of this symmetry - these Goldstone bosons are the pions
which are anomalously light mesons. This is the basis of what is
called “chiral symmetry” and “dynamical chiral symmetry breaking”.
Lattice Gauge Theory
• Physicists at the CSSM and elsewhere use the techniques of
lattice gauge theory to put all of four-dimensional space-time on a
grid or lattice.
• We formulate the gauge field theory (e.g., QED, QCD, etc.) on this
discrete lattice with finite-difference techniques. This is done in
Euclidean space-time for numerical reasons. We use methods
adapted from statistical mechanics to study the physical
properties of the theory from the confining to the asymptotically
free regimes.
• We use this to study and model subatomic particles and their
interactions. It is VERY computationally expensive to do this Teraflop-years of computer time are needed.
• More accurate results need a finer lattice with larger space-time
volumes. This is what makes it computationally costly.
Lattice QCD
Depiction of electron scattering from quark through a virtual photon
exchange in a background gluon field. Lattice QCD does weighted
averages over gauge field configurations to obtain physical quantities of
interest.
Lattice QCD: Gluon Configurations
•Typical gluon field
configuration used
in lattice
calculations, (3-dim
slice of 4-dim lattice
showing action
density, where red
depicts highest).
•The estimate of the
integral over gluon
fields does a
weighted average
over hundreds of
these.
Fluctuations in the
QCD vacuum.
High-Performance Computing
• Traditionally supercomputers were very expensive, contained
purpose-built hardware, and were obsolete within 5 years.
• Most modern high-performance computing uses cost-effective
clusters of mass-produced commodity off-the-shelf (COTS)
hardware, rather than expensive proprietary hardware.
• These clusters of workstations or PC’s are connected either by
commodity Fast Ethernet or Gigabit switched networking or by
(more expensive) special ultrafast, low-latency networks for
clustering (e.g., Myrinet, ServerNet, GigaNet, SCI, etc).
• Clusters are flexible in their design and easy to build and upgrade
- e.g., add more nodes; upgrade some or all of the nodes; upgrade
some or all of the networking.
• Can get an order of magnitude better price/performance ratio!
Top 500 Supercomputers
• Clusters of PCs or Unix workstations have become incredibly
popular in the last few years -- ranging from a few networked PCs
to around 1000 Compaq Alpha workstations.
• The unit used to measure the performance of computers is the
“flop”, i.e., 1 flop = 1 floating-point operation per second.
• In other words: 1 flop = 1 calculation per second.
• The 12 fastest supercomputers in the world all exceed 1 Teraflop,
i.e., 1 Teraflop = 1,000 Gigaflops = 1,000 billion calculations per
second.
• The current fastest is 7.2 Teraflops, (cluster with 8,192 CPU’s
called “ASCI White” at Lawrence Livermore National Laboratory in
the USA- models nuclear explosions in place of nuclear tests).
• Three of the top 4 machines serve this same purpose.
Top 500 Supercomputers (cont.)
• The fastest supercomputer in Australia at present is the NEC SX5/32M2 at the CSIRO Bureau of Meteorology in Melbourne. It is
number 99 in the world and is 241.4 /(256 peak) Gigaflops.
• The current second fastest is the APAC facility at ANU in Canberra,
which is a Compaq alpha workstation cluster and is number 134 in
the world and 167.5/(245 peak) Gigaflops. It will very soon be
upgraded to 980 peak Gigaflops (almost a Teraflop peak) and at
that time will be Australia’s fastest.
• The third is a similar Compaq cluster run by VPAC in Melbourne
and is number 151 at 149.1/(213 peak) Gigaflops.
• Fourth is our own Sun cluster in Adelaide, called “Orion”, which is
number 246 at 110/(144 peak) Gigaflops.
Cluster Computing Architectures
• Many possible design choices in building a compute cluster -depends on type of application (or applications).
• Unix workstations or Beowulf PC cluster?
• What processor, clock speed, cache, bus speed, etc?
• Single processor or Shared-Memory Processor (SMP) nodes?
• Linux or commercial operating system (OS)?
• How much memory and disk per node?
• Buy from vendor or systems integrator, or build it yourself?
• What networking technology to use?
– Commodity Fast or Gigabit switched ethernet is relatively cheap,
but has high latency.
– Low-latency, ultra-fast networks are significantly more
expensive, but far superior.
Orion Supercomputer
Built in partnership with Sun
Microsystems.
•Orion is a Sun Technical
Compute Farm with 40 Sun
E420R 4-way SMP nodes (160
processors). Fast switched
ethernet AND high-speed Myrinet
network.
•110/(144 peak) Gflops, 160
Gigabytes RAM, 640 Megabytes
cache memory.
• Fastest computer in Australia
when installed in June 2000 and
now number 4.
•The CSSM together with lattice
theorists from UNSW and the
University of Melbourne obtained
RIEF funds to seed the National
Computing Facility for Lattice
Gauge Theory (NCFLGT) which
houses the Orion supercomputer.
Orion: Software
• Nodes run Solaris and standard Sun software and compilers.
• Sun HPC ClusterTools includes
– Sun Cluster Runtime Environment (CRE)
– Sun MPI, optimized for SMP cluster (and recently for Myrinet)
– Sun Scientific Software Library (S3L)
– Prism debugger and performance analysis tool
• S3L and Prism are developed from CM software.
• Sun Fortran 90/95 compiler, supports automated parallelisation and
OpenMP directives for shared memory parallelism.
• Portland Group HPF compiler, converts code to Sun F77/90 plus MPI.
• Sun Grid Engine (formerly CODINE) cluster management system is more
advanced than CRE, supports batch queueing, detailed logging of
system usage, access levels, etc.
Centre for High-Performance
Computing and Applications (CHPCA)
• The CHPCA is a newly created cross-disciplinary Research Centre
at Adelaide University. Its goal is to bring together all researchers
with an interest and commitment to High-Performance Computing
(HPC) in order to share expertise and to develop a very large
shared computing platform. [Director: AGW; Deputy Directors:
Paul Coddington (DHPC), Derek Lienweber (CSSM), and Francis
Vaughan (SAPAC)].
• Partner researchers include: Physics, Chemistry, Engineering,
Biology and Bioinformatics, Plant Science, Geology and
Geophysics, Water Resource Management, etc.
• Next year (2002) the CHPCA already has enough funds from its
members and partners to construct a 250+ Gigaflop cluster
consisting of 40 dual processor 2 GHz Pentium 4 nodes with
Myrinet 2000 cluster networking.
• The goal is to raise funds to turn this into a Teraflop
supercomputer.
CHPCA: Engineering Applications
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Computational fluid dynamics.
Drag and noise reduction in planes, ships, submarines, etc.
Petroleum geology, oil and gas reservoir modeling.
Flow through porous media.
Water quality management and salinity.
Optimization of distribution systems for water piplines, power lines, and
telecommunication networks.
• Optimization of engineering design over a large parameter space
– search over multiple parameters using task farm approach, many
sequential jobs each with different parameters
CHPCA: Biological Applications
• Bluegene - IBM plans to build a 1 Petaflop computer to study
fundamental problems in computational biology and protein science - (1
Petaflop = 1,000 Teraflops!) - 1 million processors and each processor
with multiple CPU’s and memory and communication logic built in.
• Bluegene will focus on protein folding in particular.
• Modelling heart and brain function, organ and arterial simulation chaos, heart fibrillation, epileptic seizures, etc.
• The “virtual human” project - Oak Ridge National Laboratory.
• DNA and protein sequence analysis and classification.
• Genome data and bioinformatics - “data farming” for efficient storage,
recovery, searching and matching of vast biological data, e.g., for
efficient drug design, etc.
Conclusions and Outlook
• This is an exciting time for theoretical subatomic physics in Australia.
• The CSSM is continuing to build on its successes and is highly productive.
• The Australian lattice QCD program is now well-established and runs a
world-class supercomputing facility.
• With the establishment of a cross-disciplinary CHPCA the path to a Teraflop
computer and a world-class resource for the coming years is becoming a
reality.
• We look forward to new discoveries and new opportunities in subatomic
physics over the next few years.
• Cross-disciplinary activity in High-Performance Computing research is
becoming increasingly important for the HPC field in order that research
areas that depend on it continue to thrive. - We are working on that.
• Thank you for your attention.
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