Dirac-Born-Infeld action from spontaneous breakdown of Lorentz symmetry in brane-world scenarios

In whatever Lorentz invariant theory, the presence of extended d-dimensional objects inside a higher dimensional bulk space-time, like for instance D-branes in string theories, induces a spontaneous breakdown of the Poincare' invariance of the bulk; however the effective action describing these extended objects should still respect this larger invariance through a non-linear realization of the full symmetry. Here the specific form of such a realization in presence of an electromagnetic field is uncovered. The Dirac-Born-Infeld type action for a D-brane turns out to be invariant under such transformations. Conversely it is explicitly demonstrated in some simple cases that the most general invariant action, as long as derivatives of the field strength (and second derivatives of the scalars) can be neglected, is a linear combination of terms of the Dirac-Born-Infeld type with different scale parameters. The string result is obtained if one further assumes that the theory depends upon a single length scale.Comment: 4 pages, no figures. v4: typos corrected; matches the published versio

Critical exponents for higher-representation sources in 3D SU(3) gauge theory from CFT

We establish an exact mapping between the multiplication table of the irreducible representations of SU(3) and the fusion algebra of the two-dimensional conformal field theory in the same universality class of 3D SU(3) gauge theory at the deconfining point. In this way the Svetitsky-Yaffe conjecture on the critical behaviour of Polyakov lines in the fundamental representation naturally extends to whatever representation one considers. As a consequence, the critical exponents of the correlators of these Polyakov lines are determined. Monte Carlo simulations with sources in the symmetric two-index representation, combined with finite-size scaling analysis, compare very favourably with these predictions.Comment: 15 pages, 2 figure

Self-avoiding effective strings in lattice gauge theories

It is shown that the effective string recently introduced to describe the long distance dynamics of 3D gauge systems in the confining phase has an intriguing description in terms of models of 2D self-avoiding walks in the dense phase. The deconfinement point, where the effective string becomes N=2 supersymmetric, may then be interpreted as the tricritical Theta point where the polymer chain undergoes a collapse transition. As a consequence, a universal value of the deconfinement temperature is predicted.Comment: 7 page

The Effective String of 3D Gauge Systems at the Deconfining Transition

It is argued that the effective string of whatever 3D gauge system at the deconfining transition is universally described by the minimal $N=2$ extended superconformal theory at $c=1$. A universal value of the critical temperature is predicted.Comment: 5 page