A. Morel
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
A. Morel has a total of 9 co-authors. Here are the top co-authors by number of shared publications:
- Bengt Petersson
Fakultät für Physik Universität Bielefeld P.O.Box 10 01 31 D-33501 Bielefeld Germany
5 shared publications - K. Petrov
Fakultät für Physik Universität Bielefeld P.O.Box 100131 D-33501 Bielefeld Germany
3 shared publications - T. Reisz
Service de Physique Théorique de Saclay CE-Saclay F-91191 Gif-sur-Yvette Cedex France
3 shared publications - P. Bialas
Institute of Comp. Science, Jagellonian University, 33-072 Krakow, Poland
2 shared publications - J. L. Meunier
Institut non Linéaire de Nice-Sophia Antipolis 1361 Route des Lucioles 06560 Valbonne France
1 shared publication J. Schroper
Fakultät für Physik Universität Bielefeld Postfach 10 01 31 D-33501 Bielefeld Germany
1 shared publication
Latest Publications
- Open Access
A Gauge Theory of Wilson Lines as a Dimensionally Reduced Model of QCD_3
We analyze a two dimensional SU(3) gauge model of Wilson lines as a dimensionally reduced model of high temperature QCD_3. In contrast to perturbative dimensional reduction it has an explicit global Z(3) symmetry in the action. The phase diagram of the model is studied in the space of two free parameters used to describe the self interaction of the Wilson lines. In addition to the confinement-deconfinement transition, the model also exhibits a new Z(3)-breaking phase. These findings are obtained by numerical simulations, and supported by a perturbative calculation to one loop. A screening mass from Polyakov loop correlations is calculated numerically. It matches the known QCD_3 mass in a domain of parameters belonging to the normal deconfined phase.
Open AccessA Gauge Theory of Wilson Lines as a Dimensionally Reduced Model of QCD_3
We analyze a two dimensional SU(3) gauge model of Wilson lines as a dimensionally reduced model of high temperature QCD_3. In contrast to perturbative dimensional reduction it has an explicit global Z(3) symmetry in the action. The phase diagram of the model is studied in the space of two free parameters used to describe the self interaction of the Wilson lines. In addition to the confinement-deconfinement transition, the model also exhibits a new Z(3)-breaking phase. These findings are obtained by numerical simulations, and supported by a perturbative calculation to one loop. A screening mass from Polyakov loop correlations is calculated numerically. It matches the known QCD_3 mass in a domain of parameters belonging to the normal deconfined phase.
- Open Access
- 31 May 2001
- Published by Elsevier in Nuclear Physics B
- Vol. 603 (1-2) , 369-388
QCD with adjoint scalars in 2D: properties in the colourless scalar sector
- 31 May 2001
- Published by Elsevier in Nuclear Physics B
- Vol. 603 (1-2) , 369-388
Open AccessQCD with adjoint scalars in 2D: properties in the colourless scalar sector
- Open Access
QCD with Adjoint Scalars in 2D: Properties in the Colourless Scalar Sector
We present a numerical study of an SU(3) gauged 2D model for adjoint scalar fields, defined by dimensional reduction of pure gauge QCD in (2+1)D at high temperature. In the symmetric phase of its global Z_2 symmetry, two colourless boundstates, even and odd under Z_2, are identified. Their respective contributions (poles) in correlation functions of local composite operators A_n of degree n=2p and 2p+1 in the scalar fields (p=1,2) fulfill factorization. The contributions of two particle states (cuts) are detected. Their size agrees with estimates based on a meanfield-like decomposition of the p=2 operators into polynomials in p=1 operators. No sizable signal in any A_n correlation can be attributed to 1/n times a Debye screening length associated with n elementary fields. These results are quantitatively consistent with the picture of scalar ``matter'' fields confined within colourless boundstates whose residual ``strong'' interactions are very weak.
Open AccessQCD with Adjoint Scalars in 2D: Properties in the Colourless Scalar Sector
We present a numerical study of an SU(3) gauged 2D model for adjoint scalar fields, defined by dimensional reduction of pure gauge QCD in (2+1)D at high temperature. In the symmetric phase of its global Z_2 symmetry, two colourless boundstates, even and odd under Z_2, are identified. Their respective contributions (poles) in correlation functions of local composite operators A_n of degree n=2p and 2p+1 in the scalar fields (p=1,2) fulfill factorization. The contributions of two particle states (cuts) are detected. Their size agrees with estimates based on a meanfield-like decomposition of the p=2 operators into polynomials in p=1 operators. No sizable signal in any A_n correlation can be attributed to 1/n times a Debye screening length associated with n elementary fields. These results are quantitatively consistent with the picture of scalar ``matter'' fields confined within colourless boundstates whose residual ``strong'' interactions are very weak.
- Open Access
High Temperature 3D QCD: Dimensional Reduction at Work
We investigate the three-dimensional SU(3) gauge theory at finite temperature in the framework of dimensional reduction. The large scale properties of this theory are expected to be conceptually more complicated than in four dimensions. The dimensionally reduced action is computed in closed analytical form. The resulting effective two-dimensional theory is studied numerically both in the electric and magnetic sector. We find that dimensional reduction works excellently down to temperatures of 1.5 times the deconfinement phase transition temperature and even on rather short length scales. We obtain strong evidence that for ${\rm QCD}_3$, even at high temperature the colour averaged potential is represented by the exchange of a single state, at variance with the usual Debye screening picture involving a pair of electric gluons.Open AccessHigh Temperature 3D QCD: Dimensional Reduction at Work
We investigate the three-dimensional SU(3) gauge theory at finite temperature in the framework of dimensional reduction. The large scale properties of this theory are expected to be conceptually more complicated than in four dimensions. The dimensionally reduced action is computed in closed analytical form. The resulting effective two-dimensional theory is studied numerically both in the electric and magnetic sector. We find that dimensional reduction works excellently down to temperatures of 1.5 times the deconfinement phase transition temperature and even on rather short length scales. We obtain strong evidence that for ${\rm QCD}_3$, even at high temperature the colour averaged potential is represented by the exchange of a single state, at variance with the usual Debye screening picture involving a pair of electric gluons. - Open Access
Condensation and Metastability in the 2D Potts Model
For the first order transition of the Ising model below $T_c$, Isakov has proven that the free energy possesses an essential singularity in the applied field. Such a singularity in the control parameter, anticipated by condensation theory, is believed to be a generic feature of first order transitions, but too weak to be observable. We study these issues for the temperature driven transition of the $q$ states 2D Potts model at $q>q_c=4$. Adapting the droplet model to this case, we relate its parameters to the critical properties at $q_c$ and confront the free energy to the many informations brought by previous works. The essential singularity predicted at the transition temperature leads to observable effects in numerical data. On a finite lattice, a metastability domain of temperatures is identified, which shrinks to zero in the thermodynamical limit. ~Open AccessCondensation and Metastability in the 2D Potts Model
For the first order transition of the Ising model below $T_c$, Isakov has proven that the free energy possesses an essential singularity in the applied field. Such a singularity in the control parameter, anticipated by condensation theory, is believed to be a generic feature of first order transitions, but too weak to be observable. We study these issues for the temperature driven transition of the $q$ states 2D Potts model at $q>q_c=4$. Adapting the droplet model to this case, we relate its parameters to the critical properties at $q_c$ and confront the free energy to the many informations brought by previous works. The essential singularity predicted at the transition temperature leads to observable effects in numerical data. On a finite lattice, a metastability domain of temperatures is identified, which shrinks to zero in the thermodynamical limit. ~ - Open Access
An investigation of the 2D attractive Hubbard model
We present an investigation of the 2D attractive Hubbard model, considered as an effective model relevant to superconductivity in strongly interacting electron systems. We use both hybrid Monte Carlo simulations and existing hopping parameter expansions to explore the low temperature domain. The increaseof the static S-wave pair correlation with decreasing temperature is analyzed in terms of an expected Kosterlitz-Thouless superconducting transition. The evidence for this transition is weak: If it exists, its temperature is very low and depends weakly on the band filling near half filling. The number of unpaired electrons remains nearly constant with temperature at fixed attractive potential strength. In contrast, the static magnetic susceptibility decreases fast with temperature, and cannot be related only to pair formation. We introduce a method by which the Pade approximants of the existing series for the susceptibility give sensible results down to rather low temperature region, as shown by comparison with our numerical data.
Open AccessAn investigation of the 2D attractive Hubbard model
We present an investigation of the 2D attractive Hubbard model, considered as an effective model relevant to superconductivity in strongly interacting electron systems. We use both hybrid Monte Carlo simulations and existing hopping parameter expansions to explore the low temperature domain. The increaseof the static S-wave pair correlation with decreasing temperature is analyzed in terms of an expected Kosterlitz-Thouless superconducting transition. The evidence for this transition is weak: If it exists, its temperature is very low and depends weakly on the band filling near half filling. The number of unpaired electrons remains nearly constant with temperature at fixed attractive potential strength. In contrast, the static magnetic susceptibility decreases fast with temperature, and cannot be related only to pair formation. We introduce a method by which the Pade approximants of the existing series for the susceptibility give sensible results down to rather low temperature region, as shown by comparison with our numerical data.