Project

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Non-perturbative aspects of chiral symmetry and confinement in QCD and related theories

English title Non-perturbative aspects of chiral symmetry and confinement in QCD and related theories
Applicant Wenger Urs Rudolf
Number 139196
Funding scheme SNSF Professorships
Research institution Institut für Theoretische Physik Universität Bern
Institution of higher education University of Berne - BE
Main discipline Theoretical Physics
Start/End 01.03.2012 - 30.09.2014
Approved amount 751'557.00
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All Disciplines (2)

Discipline
Theoretical Physics
Particle Physics

Keywords (14)

Particle Physics; Theoretical Physics; Large-N Gauge Theories; Numerical Simulations; Lattice Gauge Theory; Confinement; Non-Perturbative Calculations; Algorithms; Supersymmetric Gauge Theories; Lattice QCD; Chiral Symmetry; String-Gauge Duality; Supersymmetric Matrix Models; Supersymmetry

Lay Summary (English)

Lead
Lay summary
At low energies, Quantum Chromodynamics (QCD) exhibits a variety of phenomena that can not be described in the framework of perturbation theory. Many of these non-perturbative aspects of the theory are still poorly understood, like for example colour confinement, the fact that only composite colour-neutral particles, so-called hadrons, can be observed in nature, but not the quarks and gluons themselves. Another non-perturbative aspect of QCD is the spontaneous breaking of chiral symmetry leading to the particular spectrum of the lightest hadrons observed in nature. Yet another striking non-perturbative phenomenon is the restoration of chiral symmetry, either at large density where new unexplored phases of baryonic matter emerge, as they might exist in compact stars, or at high temperature where ordinary hadronic matter transforms into a quark-gluon-plasma, as is beautifully demonstrated by lattice QCD calculations and also indicated by heavy-ion collision experiments. It is clear that a thorough qualitative and quantitative understanding of all these non-perturbative aspects of QCD is of utmost importance for the justification of QCD as the fundamental theory describing the strong interactions and for the justification of the Standard Model (SM) in general. One goal of this project is to provide exactly such an understanding of low-energy QCD via computer simulations where all the systematic errors are under control. Precise ab-initio calculations of the non-perturbative properties of QCD in the chiral regime will enable a further confirmation of the theoretical framework. One of the main challenges for non-perturbative QCD calculations lies e.g.~in the accurate and reliable determination of hadronic matrix elements and form factors which in many cases constitute the main source of theoretical uncertainties in the direct confrontation of the theory with experiment. Furthermore, such results will be used as valuable input into non-perturbative effects in SM phenomenology, and beyond, via the reduction of theoretical uncertainties in the hadronic sector. This will provide stringent tests of the SM and constitute an invaluable contribution towards the potential discovery of new Beyond the Standard Model (BSM) physics at the Large Hadron Collider (LHC). In the same spirit this project also aims to put the non-perturbative study of QCD and QCD-like theories to wider use beyond the SM. This is achieved by trying to derive analogous non-perturbative properties of large-N field theories, where the number of colour degrees of freedom is taken to infinity, or Supersymmetric (SUSY) gauge theories that are likely to turn out to be the more fundamental theories in Particle Physics. This approach is made possible on the one hand through our recent developments in understanding and simulating QCD and related theories in the chiral regime, but also through our novel, non-perturbative studies of (pure gauge) QCD in the limit of a large number of quark colours. In particular, the large-N limit allows to build a bridge between the conventional Quantum Field Theory approach to particle physics and alternative theories like string theories which try to explain our microscopic world as the result of resonating strings and branes. Another important step is our recent development of the fermion loop formulation for low-dimensional SUSY models on the lattice, e.g. SUSY matrix models. This allows very efficient simulations of these models and hence the non-perturbative investigation of spontaneous SUSY breaking from first principles.

The understanding of the non-perturbative properties related to confinement, chiral symmetry and SUSY breaking of large-N and SUSY field theories will lead to new insights into the mechanisms and theories behind it. To gain a non-perturbative understanding of these theories is one of the main objectives of this proposal and will be of highest relevance in view of the potential discovery of BSM physics at the LHC.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Comparison of different lattice definitions of the topological charge
Cichy K., Dromard A., Garcia-Ramos E., Ottnad K., Urbach C., Wagner M., Wenger U., Zimmermann F. (2014), Comparison of different lattice definitions of the topological charge, in Proceedings of Science, LATTICE2014, 075.
Conformal Dynamics and Thermal/Bulk Phase Transition in Lattice Gauge Theory with Many Fermion Species
Miura K., Lombardo M.-P., Pallante E., Nunes da Silva T., Deuzeman A. (2014), Conformal Dynamics and Thermal/Bulk Phase Transition in Lattice Gauge Theory with Many Fermion Species, in Proceedings, 1.
Loop formulation of supersymmetric Yang-Mills quantum mechanics
Steinhauer K., Wenger U. (2014), Loop formulation of supersymmetric Yang-Mills quantum mechanics, in Journal of High Energy Physics, 12, 044.
Progress in Simulations with Twisted Mass Fermions at the Physical Point
Abdel-Rehim A., Alexandrou C., Dimopoulos P., Frezzotti R., Jansen K., Kallidonis C., Kostrzewa B., Mangin-Brinet M., Rossi C. G., Urbach C., Wenger U. (2014), Progress in Simulations with Twisted Mass Fermions at the Physical Point, in Proceedings of Science, LATTICE2014, 119.
Review of lattice results concerning low energy particle physics
Aoki Sinya, Aoki Yasumichi, Bernard Claude, Blum Tom, Colangelo Gilberto, Wenger Urs (2014), Review of lattice results concerning low energy particle physics, in Eur.Phys.J., C74(9), 2890.
Spontaneous supersymmetry breaking in the two-dimensional N=1 Wess-Zumino model
Steinhauer K., Wenger U. (2014), Spontaneous supersymmetry breaking in the two-dimensional N=1 Wess-Zumino model, in Physical Review Letters, 113, 231601.
String Tension versus Critical Temperature in Walking Regime
Miura K., Deuzeman A., Lombardo M.-P., Nunes da Silva T., Pallante E. (2014), String Tension versus Critical Temperature in Walking Regime, in Proceedings of Science, LATTICE(2013), 74.
Up, down, strange and charm quark masses with Nf = 2+1+1 twisted mass lattice QCD
Carrasco N., Deuzeman A., Dimopoulos P., Frezzotti R., Gimenez V., others, Wenger U. (2014), Up, down, strange and charm quark masses with Nf = 2+1+1 twisted mass lattice QCD, in Nucl.Phys., B887, 19-68.
A first look at maximally twisted mass lattice QCD calculations at the physical point
Abdel-Rehim A., Boucaud Ph., Carrasco N., Deuzeman A., Dimopoulos P., others (2013), A first look at maximally twisted mass lattice QCD calculations at the physical point, in PoS, LATTICE2013, 264-264.
Corrections to the Banks-Casher relation with Wilson quarks
Necco S., Shindler A. (2013), Corrections to the Banks-Casher relation with Wilson quarks, in PoS, C12-08-06, 056-2012.
Experiences with OpenMP in tmLQCD
Deuzeman A., Jansen K., Kostrzewa B., Urbach C. (2013), Experiences with OpenMP in tmLQCD, in PoS, LATTICE2013, 416-416.
Loop formulation of the supersymmetric nonlinear O(N) sigma model
Steinhauer Kyle, Wenger Urs (2013), Loop formulation of the supersymmetric nonlinear O(N) sigma model, in PoS, LATTICE2013, 092-092.
Recent developments in the tmLQCD software suite
Deuzeman A., Abdel-Rehim A, Burger F., Jansen K., Kostrzewa B., Scorzato L., Urbach C. (2013), Recent developments in the tmLQCD software suite, in Proceedings of Science, LATTICE2013 (2014), 414.
The bulk transition of QCD with twelve flavors and the role of improvement
Deuzeman Albert, Lombardo Maria Paola, da Silva Tiago Nunes, Pallante Elisabetta (2013), The bulk transition of QCD with twelve flavors and the role of improvement, in Phys. Lett., B720, 358-365.
Gradient flow and scale setting for twisted mass fermions
Deuzeman Albert, Wenger Urs (2012), Gradient flow and scale setting for twisted mass fermions, in PoS, LATTICE2012, 162-162.
N(f) = 2 chiral dynamics in the mixed-regime
Vulvert Gregory, Hernandez Pilar, Necco Silvia, Pena Carlos (2012), N(f) = 2 chiral dynamics in the mixed-regime, in PoS, LATTICE2012, 204-204.
Phases of many flavors QCD : Lattice results
Deuzeman Albert, Lombardo Maria Paola, Miura Kohtaroh, Nunes da Silva Tiago, Pallante Elisabetta (2012), Phases of many flavors QCD : Lattice results, in PoS, ConfinementX, 274-274.
Spontaneous supersymmetry breaking in the 2d N=1 Wess-Zumino model
Wenger Urs, Steinhauer Kyle, Baumgartner David (2012), Spontaneous supersymmetry breaking in the 2d N=1 Wess-Zumino model, in PoS, LATTICE2012, 043-043.

Collaboration

Group / person Country
Types of collaboration
Flavianet Lattice Averaging Group (FLAG) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
ETH Zuerich and CERN, Geneva Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
George Washington University, Washington United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
European Twisted Mass Collaboration (ETMC) Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
32nd International Symposium on Lattice Field Theory (Lattice 2014) Talk given at a conference Loop formulation of supersymmetric Yang-Mills quantum mechanics 23.06.2014 New York, United States of America Wenger Urs Rudolf;
Oxford University, Particle and Fields Seminar Individual talk Spontaneous supersymmetry breaking on the lattice 28.11.2013 Oxford, Great Britain and Northern Ireland Wenger Urs Rudolf;
ETM Collaboration Meeting Talk given at a conference Scale setting for TM using gradient flow observables 10.09.2013 Berlin, Germany Wenger Urs Rudolf;
31st International Symposium on Lattice Field Theory (LATTICE 2013) Talk given at a conference Experiences with OpenMP in tmLQCD 29.07.2013 Mainz, Germany Deuzeman Albert;
31st International Symposium on Lattice Field Theory (LATTICE 2013) Talk given at a conference Loop formulation for the non-linear suppersymmetric O(N) sigma model 29.07.2013 Mainz, Germany Steinhauer Kyle;
31st International Symposium on Lattice Field Theory (LATTICE 2013) Talk given at a conference Common coding strategies for lattice QCD 29.07.2013 Mainz, Germany Deuzeman Albert;
Johann Wolfgang Goethe-Universität, ITP lattice seminar Individual talk Spontaneous supersymmetry breaking on the lattice 12.06.2013 Frankfurt am Main, Germany Wenger Urs Rudolf;
Frühjahrstagung der Deutschen Physikalischen Gesellschaft Talk given at a conference Spontaneous supersymmetry breaking on the lattice 25.02.2013 Jena, Germany Wenger Urs Rudolf;
Workshop on Strongly-Interacting Field Theories (SIFT 2012) Talk given at a conference Spontaneous supersymmetry breaking on the lattice 29.11.2012 Jena, Germany Wenger Urs Rudolf;
1st General Workshop of the Albert Einstein Center for Fundamental Physics Talk given at a conference Non-perturbative properties of the Standard Model and beyond 12.11.2012 Bern, Switzerland Wenger Urs Rudolf;
International Workshop on the Sign-Problem in QCD (SIGN 2012) Talk given at a conference Spontaneous supersymmetry breaking and the sign problem 19.09.2012 Regensburg, Germany Wenger Urs Rudolf;
7th International Workshop on Lattice QCD and Numerical Analysis (QCDNA VII) Talk given at a conference Simulating Wilson fermions without critical slowing down 04.07.2012 Adelaide, Australia Wenger Urs Rudolf;
30th International Symposium on Lattice Field Theory (LATTICE 2012) Talk given at a conference Spontaneous supersymmetry breaking in the 2d N=1 Wess-Zumino model 24.06.2012 Cairns, Australia Wenger Urs Rudolf;
30th International Symposium on Lattice Field Theory (LATTICE 2012) Talk given at a conference Gradient flow and scale setting for twisted mass fermions 24.06.2012 Cairns, Australia Deuzeman Albert;
ETM Collaboration Meeting Talk given at a conference Scale setting and topology from the gradient flow 02.05.2012 Orsay, Paris, France Wenger Urs Rudolf;
SFB Transregio 55 Meeting Talk given at a conference Supersymmetry on the lattice with Wilson fermions 29.03.2012 Regensburg, Germany Wenger Urs Rudolf;


Self-organised

Title Date Place
FLAG meeting 2014 19.05.2014 Madrid, Spain
QCD under extreme conditions (XQCD 2013) 05.08.2013 Bern, Switzerland
7th International Workshop on Chiral Dynamics 06.08.2012 Newport News, United States of America
FLAG-2 kick-off Meeting 07.05.2012 Les Houches, France

Associated projects

Number Title Start Funding scheme
149331 Non-perturbative aspects of strongly interacting quantum field theories 01.10.2014 Project funding
119015 Non-perturbative aspects of chiral symmetry and confinement in QCD and related theories 01.03.2008 SNSF Professorships

Abstract

The primary goal of this project is to provide a thorough qualitative and quantitative understanding of non-perturbative phenomena in the chiral regime of Quantum Chromodynamics (QCD) and related models via computer simulations. Many of these non-perturbative aspects are still poorly understood, like for example colour confinement, or the spontaneous breaking of chiral symmetry and its restoration either at high temperature or at large chemical potential where new and partly unexplored phases of strongly interacting matter emerge.One of the main challenges for non-perturbative QCD calculations lies in the accurate and reliable determination of the hadronic properties which in many cases constitute the main source of theoretical uncertainties in the direct confrontation of the theory with experiment. The precise ab-initio calculations that we are proposing in this project will enable a further confirmation of the theoretical framework and provide stringent tests of the Standard Model (SM). Moreover they will constitute invaluable contributions towards the potential discovery of new physics beyond the SM at the Large Hadron Collider (LHC).In the same spirit we also aim to put the non-perturbative study of QCD and QCD-like theories to wider use beyond the SM. This is achieved by our proposal to derive analogous non-perturbative properties of supersymmetric gauge theories that are likely to turn out to be the more fundamental theories in Particle Physics. This approach is made possible on the one hand through our recent developments in understanding and simulating QCD and related theories in the chiral regime, but also through our novel, non-perturbative studies of (pure gauge) QCD in the limit of a large number of quark colours. In particular, our proposed calculations allow to build a bridge between the conventional Quantum Field Theory approach and alternatives like string theories which try to explain our microscopic world as the result of resonating strings and branes. The understanding of the non-perturbative properties related to confinement and chiral symmetry breaking of large-N and SUSY field theories will lead to new insights into the fundamental mechanisms and theories behind it. To gain a non-perturbative understanding of these theories is one of the main objectives of this proposal and will be of highest relevance in view of the potential discovery of BSM physics at the LHC.
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