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January 26, 2009

All around is just vacuum fluctuations

2 comments

Recent lattice QCD (Quantum ChronoDynamics) simulations madden at the John von Neumann Institute for Computing in Jülich, Germany, confirms that most of our mass comes from virtual quarks and gluons fizzing away in the quantum vacuum. This last statement is reinforced by the fact that with this lattice QCD method, calculations on the proton mass are wrong by 2% only wrt the value measured by experiments.

According to particle physics, the atoms are made up of protons and neutrons (more than 99% of the mass of the visible universe is made up of protons and neutrons), which are themselves composed of smaller particles known as quarks, which in turn are bound by gluons. Problem is that the mass of gluons is zero and the mass of quarks accounts for only 5%. So, where is the missing 95%?

Quark and gluon structure of a nucleon
© Jean-Francois COLONNA – hhtp://www.lactamme.polytechnique.fr



Once again, theory indicates that the energy coming from interactions between quarks and gluons accounts for the excess mass (thanks to Einstein's E=mc2 equation). Gluons give the strong nuclear force necessary to maintain three quarks together to form one proton or neutron. These gluons are constantly popping into existence and disappearing again and the energy of these vacuum fluctuations has to be included in the total mass of the proton and neutron.

This strong nuclear interaction is very well known, it's described by the equations of QCD (Quantum ChronoDynamics), but there are very difficult to solve in order to obtain actual numbers. Even with the method called lattice QCD, the calculations on virtual quarks (pairs of virtual quarks and antiquarks completes the model of the quantum vacuum) involves a matrix of more than 10 000 trillions numbers and there's no computer on Earth that could store such a big matrix in its memory as told Stephan Dürr, team member of the John von Neumann Institute for Computing in Jülich, Germany. Instead of simulates a three quark proton, Dürr's team has used a two-quark proton. In order to obtains some results, a parallel computer network that can handle 200 teraflops, has been used for almost 1 year. Without the quarks, earlier simulations got the proton mass wrong by about 10%. With them, Dürr gets a figure within 2% of the value measured by experiments.

Thus, Jürr's team present a full ad initio calculation for predicting accurately the masses of protons, neutrons, and other quark based particles using lattice QCD. They suggest that QCD is the theory of the strong interaction, at low energies as well, and furthermore that lattice studies have reached the stage where all uncertainties can be fully controlled. Furthermore, this study confirms the Standard Model (thanks God!) and the fact that most of our mass comes from virtual quarks and gluons fizzing away in the quantum vacuum.

What's next? To confirm another piece of the Standard Model puzzle, that is, to confirm that the Higgs field add also a small amount of mass to individual quarks, electrons and some other particles in the form of virtual Higgs bosons. The Large Hadron Collider will search for these Higgs bosons when it starts up at the middle of 2009. If the "God particle" is not observed next months in the LHC, that will not radically change the Standard Model (it’s just a model and we can adjust it if necessary) or our vision of the Universe; but if it exists, then we could concentrate our efforts in a new vision of the matter: the supersymmetry.



References:

Ab Initio Determination of Light Hadron Masses
S. Dürr (1), Z. Fodor (1,2,3), J. Frison (4), C. Hoelbling (2,3,4), R. Hoffmann (2), S. D. Katz (2,3), S. Krieg (2), T. Kurth (2), L. Lellouch (4), T. Lippert (2,5), K. K. Szabo (2), G. Vulvert (4).

(1) John von Neumann–Institut für Computing, Deutsches Elektronen-Synchrotron Zeuthen, D-15738 Zeuthen and Forschungszentrum Jülich, D-52425 Jülich, Germany.
(2) Bergische Universität Wuppertal, Gaussstrasse 20, D-42119 Wuppertal, Germany.
(3) Institute for Theoretical Physics, Eötvös University, H-1117 Budapest, Hungary.
(4) Centre de Physique Théorique (UMR 6207 du CNRS et des Universités d'Aix-Marseille I, d'Aix-Marseille II et du Sud Toulon-Var, affiliée à la FRUMAM), Case 907, Campus de Luminy, F-13288, Marseille Cedex 9, France.
(5) Jülich Supercomputing Centre, FZ Jülich, D-52425 Jülich, Germany.

http://blogs.discovermagazine.com/80beats/2008/11/21/confirmed-scientists-understand-where-mass-comes-from/


2 comments:

Zopenco January 28, 2009 at 10:54 PM  

Ciencia de punta. Que lo pario Mendieta no somos nada!

Sotreta Trompeta January 29, 2009 at 9:19 AM  

Y eso no es nada comparado a la teleportacion de qubits !!

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