A picture of the Yang-Mills deconfinement transition and its lattice verification

In the framework of the center vortex picture of confinement, the nature of the deconfining phase transition is studied. Using recently developed techniques which allow to associate a center vortex configuration with any given lattice gauge configuration, it is demonstrated that the confining phase is a phase in which vortices percolate, whereas the deconfined phase is a phase in which vortices cease to percolate if one considers an appropriate slice of space-time.Comment: 9 pages, 3 ps figures included via epsfig; invited talk presented by M. Engelhardt at the Eleventh International Light-Cone Workshop on "New directions in Quantum Chromodynamics", Kyungju, Korea, 21.-25.6.99, to appear in the proceeding

Energy Density of Vortices in the Schroedinger Picture

The one-loop energy density of an infinitely thin static magnetic vortex in SU(2) Yang-Mills theory is evaluated using the Schroedinger picture. Both the gluonic fluctuations as well as the quarks in the vortex background are included. The energy density of the magnetic vortex is discussed as a function of the magnetic flux. The center vortices correspond to local minima in the effective potential. These minima are degenerated with the perturbative vacuum if the fermions are ignored. Inclusion of fermions lifts this degeneracy, raising the vortex energy above the energy of the perturbative vacuum.Comment: 25 pages, 2 figure

Beyond the Principles of Bioethics: Facing the Consequences of Fundamental Moral Disagreement

Given intractable secular moral pluralism, the force and significance of the four principles (autonomy, beneficence, non-maleficence, and justice) of Tom Beauchamp and James Childress must be critically re-considered. This essay examines the history of the articulation of these four principles of bioethics, showing why initially there was an illusion of a common morality that led many to hold that the principles could give guidance across cultures. But there is no one sense of the content or the theoretical justification of these principles. In addition, a wide range of secular moral and bioethical choices has been demoralized into lifestyle choices; the force of the secular moral point of view has also been deflated, thus compounding moral pluralism. It is the political generation of the principles that provides a common morality in the sense of an established morality. The principles are best understood as embedded not in a common morality, sensu stricto, but in that morality that is established at law and public policy in a particular polity. Although moral pluralism is substantive and intractable at the level of moral content, in a particular polity a particular morality and a particular bioethics can be established, regarding which health care ethics consultants can be experts. Public morality and bioethics are at their roots a political reality

Magnetic Monopoles, Center Vortices, Confinement and Topology of Gauge Fields

The vortex picture of confinement is studied. The deconfinement phase transition is explained as a transition from a phase in which vortices percolate to a phase of small vortices. Lattice results are presented in support of this scenario. Furthermore the topological properties of magnetic monopoles and center vortices arising, respectively, in Abelian and center gauges are studied in continuum Yang-Mills-theory. For this purpose the continuum analog of the maximum center gauge is constructed.Comment: talk given by H. Reinhardt on the Int. Workshop ``Hadrons 1999'', Coimbra, 10.-15. Sept. 199

Writhe of center vortices and topological charge -- an explicit example

The manner in which continuum center vortices generate topological charge density is elucidated using an explicit example. The example vortex world-surface contains one lone self-intersection point, which contributes a quantum 1/2 to the topological charge. On the other hand, the surface in question is orientable and thus must carry global topological charge zero due to general arguments. Therefore, there must be another contribution, coming from vortex writhe. The latter is known for the lattice analogue of the example vortex considered, where it is quite intuitive. For the vortex in the continuum, including the limit of an infinitely thin vortex, a careful analysis is performed and it is shown how the contribution to the topological charge induced by writhe is distributed over the vortex surface.Comment: 33 latex pages, 10 figures incorporating 14 ps files. Furthermore, the time evolution of the vortex line discussed in this work can be viewed as a gif movie, available for download by following the PostScript link below -- watch for the cute feature at the self-intersection poin

Center Vortex Model for the Infrared Sector of SU(3) Yang-Mills Theory - Vortex Free Energy

The vortex free energy is studied in the random vortex world-surface model of the infrared sector of SU(3) Yang-Mills theory. The free energy of a center vortex extending into two spatial directions, which is introduced into Yang-Mills configurations when acting with the 't Hooft loop operator, is verified to furnish an order parameter for the deconfinement phase transition. It is shown to exhibit a weak discontinuity at the critical temperature, corresponding to the weak first order character of the transition.Comment: 13 pages, 2 figures containing 3 eps file