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Supercomputer simulations of field theories

Titel Englisch Supercomputer simulations of field theories
Gesuchsteller/in de Forcrand Philippe
Nummer 162515
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Institut für Theoretische Physik ETH Zürich
Hochschule ETH Zürich - ETHZ
Hauptdisziplin Theoretische Physik
Beginn/Ende 01.10.2015 - 30.09.2017
Bewilligter Betrag 223'421.00
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Keywords (5)

Phase diagram; Lattice gauge theory; QCD; Monte Carlo; Sign problem

Lay Summary (Französisch)

Lead
L'eau, quand on la chauffe ou qu'on la comprime, se presente sous differentsetats: la vapeur d'eau est gazeuse, l'eau est liquide, les diverses sortesde glace sont solides. En est-il de meme pour la matiere nucleaire, faitede quarks? Nous voulons etudier cette question et determiner les differentsetats de la matiere faite de quarks en fonction de la temperature et dela pression (ou de la densite). Notre etude theorique se presente commele pendant de programmes experimentaux, qui etudient la meme question aumoyen de collisions d'ions lourds a haute energie. La decouverte recented'etoiles a neutrons massives (plus de deux fois la masse du soleil)place des contraintes sur les comportements possibles de la matiere faitede quarks et en fait un sujet "brulant". Le but de notre projet est d'avancer l'etat de l'art des simulations numeriques de la matiere dequarks pour en elucider les proprietes thermodynamiques.
Lay summary
La methode de choix pour l'etude des proprietes non-perturbatives des
quarks et des gluons est la simulation numerique, par Monte Carlo, de
la chromodynamique quantique sur reseau ("lattice QCD"). Malheureusement,
cette methode ne peut pas s'appliquer au cas d'une densite non-nulle de
quarks, a cause du "probleme de signe": le poids statistique de chaque
configuration dans la fonction de partition n'est plus reel positif,
ce qui empeche de l'interpreter comme une probabilite d'echantillonage
dans un processus de Monte Carlo. Neanmoins, nous voulons progresser dans
ce domaine, dans deux directions:

A. La determination du diagramme de phase de la QCD sur reseau, au-dela
de la limite du couplage fort.

Recemment, nous avons determine le diagramme de phase complet, dans la
limite ou le couplage est infini, et nous avons mesure les corrections
dominantes a cette limite. Nous avons maintenant trouve une approche qui
s'applique a couplage moins fort, et nous voulons etudier ce regime, qui
s'approche de la limite du continu (i.e. couplage faible). A present, il
n'existe aucune autre methode qui donne des resultats fiables dans ce
regime.

B. Une precision accrue sur l'equation d'etat de la QCD a faible densite
de quarks.

Quand la densite de quarks est faible, plusieurs methodes numeriques
peuvent etre employees. Malheureusement, les groupes de recherche
correspondants ne sont pas encore d'accord sur les valeurs de quantites
fondamentales, comme la courbure de la ligne pseudo-critique ou l'existence
possible d'un point critique a un potentiel chimique faible. Nous voulons
incorporer trois ameliorations techniques, qui permettront une reduction
substantielle des erreurs sur l'equation d'etat de la QCD a faible densite,
et qui devraient permettre des reponses claires aux questions ci-dessus.
Les calculs a grande echelle requis seront executes en collaboration
avec le Prof. Massimo D'Elia et son groupe a l'Universite de Pise.

Direktlink auf Lay Summary Letzte Aktualisierung: 06.10.2015

Lay Summary (Englisch)

Lead
Water, when heated or compressed, is found in different states:gaseous steam, liquid water, and many different forms of solid ice.Is the behaviour of nuclear matter, made of quarks, similar?We want to investigate the different states of quark matter as a function of temperature and pressure (or density). This theoretical study complements experimental programs of heavy-ion collisions aimed at similar knowledge. It is even more timely now that heavy neutron stars(two solar masses) have been discovered, because they impose restrictionson possible phases of quark matter.Thus, we want to improve the state of the art in the numerical investigationof thermodynamic properties of quark matter.
Lay summary
The established tool for investigations of non-perturbative properties
of quarks and gluons is the numerical, Monte Carlo simulation of lattice QCD.
However, this standard approach is not applicable at non-zero quark density
because of the notorious ``sign problem'': the weight of each configuration
in the partition sum is not always positive, which prevents its interpretation
as a Monte Carlo sampling probability. We want to advance the state of the art
for simulations at non-zero quark density, in two directions:

A. Determining the phase diagram of lattice QCD away from the strong coupling limit.

In recent work, we have completely determined this phase diagram in the limit
of infinite coupling, and have measured leading corrections to this limit.
We have now devised a scheme to extend this study further away from the strong
coupling limit, and want to apply this scheme to extend our knowledge of the
lattice QCD phase diagram towards the continuum limit.
At present, no other approach can provide reliable information on this
crucial subject.

B. Improving the accuracy of the QCD equation of state at  small quark density.

In the regime of small densities, several numerical lattice approaches have
been employed. Still, different groups do not agree yet on basic quantities
like the curvature of the pseudo-critical line or the possible existence of
a QCD critical point at small chemical potential. We want to incorporate
three technical refinements, which will considerably improve the accuracy of
the QCD equation of state at small density, and should resolve the above
discrepancies.
The necessary large-scale simulations will be conducted in collaboration with
Prof. Massimo D'Elia and his group at the University of Pisa.

Direktlink auf Lay Summary Letzte Aktualisierung: 06.10.2015

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Publikationen

Publikation
A Worm Algorithm for the Lattice CP(N-1) Model
Rindlisbacher Tobias, de Forcrand Philippe (2017), A Worm Algorithm for the Lattice CP(N-1) Model, in Proceedings of Science, PoS LATTICE2016 (2017), ?.
Continuum limit and universality of the Columbia plot
de Forcrand Philippe, D'Elia Massimo (2017), Continuum limit and universality of the Columbia plot, in Proceedings of Science, PoS LATTICE2016 (2017), 081.
Topology in the 2d Heisenberg Model under Gradient Flow
Sandoval Ilya, Bietenholz Wolfgang, de Forcrand Philippe, Gerber Urs, Mejia-Diaz Hector (2017), Topology in the 2d Heisenberg Model under Gradient Flow, in Journal of Physics Conference Series, 912, 012024.
Aspects of topological actions on the lattice
Akerlund Oscar, de Forcrand Philippe (2016), Aspects of topological actions on the lattice, in Proceedings of Science, PoS LATTICE2015 (2016), 169.
Effects of higher dimension operators on the Standard Model Higgs sector
Akerlund Oscar, de Forcrand Philippe, Steinbauer Jakob (2016), Effects of higher dimension operators on the Standard Model Higgs sector, in Proceedings of Science, PoS LATTICE2015 (2016) , 229.
Lattice simulation of the SU(2) chiral model at zero and non-zero pion density
Rindlisbacher Tobias, de Forcrand Philippe (2016), Lattice simulation of the SU(2) chiral model at zero and non-zero pion density, in Proceedings of Science, PoS LATTICE2015 (2016), 171.
Mean distribution approach to spin and gauge theories
Akerlund Oscar, de Forcrand Philippe (2016), Mean distribution approach to spin and gauge theories, in Nuclear Physics B, Nucl.Phys. B905 (2016) , 1.
Oscillating propagators in heavy-dense QCD
Akerlund Oscar, de Forcrand Philippe, Rindlisbacher Tobias (2016), Oscillating propagators in heavy-dense QCD, in Journal of High-Energy Physics, 2016(10), 055.
Sampling of General Correlators in Worm Algorithm-based Simulations
Rindlisbacher Tobias, Akerlund Oscar, de Forcrand Philippe (2016), Sampling of General Correlators in Worm Algorithm-based Simulations, in Nuclear Physics B, 909, 542.
The Slab Method to Measure the Topological Susceptibility
Bietenholz Wolfgang, Cichy Krzysztof, de Forcrand Philippe, Dromard Arthur, Gerber Urs (2016), The Slab Method to Measure the Topological Susceptibility, in Proceedings of Science, PoS LATTICE2016 (2016), 321.
Thermodynamics of strongly-coupled lattice QCD in the chiral limit
de Forcrand Philippe, Romatschke Paul, Unger Wolfgang, Vairinhos Helvio (2016), Thermodynamics of strongly-coupled lattice QCD in the chiral limit, in Proceedings of Science, PoS LATTICE2016 (2016), 086.
Two-Flavor Lattice QCD with a Finite Density of Heavy Quarks: Heavy-Dense Limit and "Particle-Hole" Symmetry
Rindlisbacher Tobias, de Forcrand Philippe (2016), Two-Flavor Lattice QCD with a Finite Density of Heavy Quarks: Heavy-Dense Limit and "Particle-Hole" Symmetry, in Journal of High-Energy Physics, 2016(2), 1.
Worm Algorithm for CP(N-1) Model
Rindlisbacher Tobias, de Forcrand Philippe (2016), Worm Algorithm for CP(N-1) Model, in Nuclear Physics B, Nucl.Phys. B918 (2016), 178.
Topological Susceptibility from Slabs
Bietenholz Wolfgang, de Forcrand Philippe, Gerber Urs (2015), Topological Susceptibility from Slabs, in Journal of High-Energy Physics, 2015(12), 070.
Alternatives to the stochastic "noise vector" approach
de Forcrand Philippe, Jaeger Benjamin, Alternatives to the stochastic "noise vector" approach, in European Physics Journal .
Strong-Coupling Lattice QCD on Anisotropic Lattices
de Forcrand Philippe, Unger Wolfgang, Vairinhos Helvio, Strong-Coupling Lattice QCD on Anisotropic Lattices, in Physical Review D.

Zusammenarbeit

Gruppe / Person Land
Formen der Zusammenarbeit
Prof. Massimo D'Elia, Univ. of Pisa Italien (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
- Publikation

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
175701 Supercomputer simulations of field theories 01.10.2017 Projektförderung (Abt. I-III)
149723 Supercomputer simulations of field theories 01.10.2013 Projektförderung (Abt. I-III)

Abstract

Water, when heated or compressed, is found in different states:gaseous steam, liquid water, and many different forms of solid ice.Is the behaviour of nuclear matter, made of quarks, similar?We want to investigate the different states of quark matter as a functionof temperature and pressure (or density). This theoretical studycomplements experimental programs of heavy-ion collisions aimed atsimilar knowledge. It is even more timely now that heavy neutron stars(two solar masses) have been discovered, because they impose restrictionson possible phases of quark matter.Thus, we want to improve the state of the art in the numerical investigationof thermodynamic properties of quark matter.
-