Topological flux sectors in extended U(1) gauge theory on T^4

We consider the 4d compact U(1) gauge theory with fundamental-adjoint action on a hypertorus. We give a full characterization of the phase diagram of this model in terms of topological flux sectors.Comment: 3 pages, 5 figures, Lattice2002(topology

Finite temperature Z(N) phase transition with Kaluza-Klein gauge fields

If SU(N) gauge fields live in a world with a circular extra dimension, coupling there only to adjointly charged matter, the system possesses a global Z(N) symmetry. If the radius is small enough such that dimensional reduction takes place, this symmetry is spontaneously broken. It turns out that its fate at high temperatures is not easily decided with straightforward perturbation theory. Utilising non-perturbative lattice simulations, we demonstrate here that the symmetry does get restored at a certain temperature T_c, both for a 3+1 and a 4+1 dimensional world (the latter with a finite cutoff). To avoid a cosmological domain wall problem, such models would thus be allowed only if the reheating temperature after inflation is below T_c. We also comment on the robustness of this phenomenon with respect to small modifications of the model.Comment: 18 pages. Revised version, to appear in Nucl.Phys.

Are there Local Minima in the Magnetic Monopole Potential in Compact QED?

We investigate the influence of the granularity of the lattice on the potential between monopoles. Using the flux definition of monopoles we introduce their centers of mass and are able to realize continuous shifts of the monopole positions. We find periodic deviations from the $1/r$-behavior of the monopole-antimonopole potential leading to local extrema. We suppose that these meta-stabilities may influence the order of the phase transition in compact QED.Comment: 11 pages, 5 figure

Spin-Charge Separation and the Pauli Electron

The separation between the spin and the charge converts the quantum mechanical Pauli Hamiltonian into the Hamiltonian of the non-Abelian Georgi-Glashow model, notorious for its magnetic monopoles and confinement. The independent spin and charge fluctuations both lead to the Faddeev model, suggesting the existence of a deep duality structure and indicating that the fundamental carriers of spin and charge are knotted solitons.Comment: 7 pages; v2: new results added, references update

Hygrotermic Treatment of Chesnut Logs Infected with Cryphonectria parasitica

Due to the reduced availability of large-sized chestnut logs in Europe, many European timber industries currently get their supplies from non-European countries, mainly from the Caucasian region, which are often not immune to chestnut blight. Given the high risk of introducing new virulent strains incompatible with local hypovirulent ones, the European Union regulation requires that chestnut logs, imported from so-called “third party” nations where Cryphonectria parasitica is present, reach the European boundaries bark free: this prevents the production of veneers, which are highly remunerative, but whose first workmanship phases require barked logs. Following a multilevel investigation, the authors propose a stem-flow protocol that can devitalise the parasite in barked logs while preserving the commodity characteristics of the wood, through a fast, simple and low-cost treatment, that can be performed at the European borders whenever C. parasitica is or might be present

The phase diagram of Yang-Mills theory with a compact extra dimension

We present a non-perturbative study of the phase diagram of SU(2) Yang-Mills theory in a five-dimensional spacetime with a compact extra dimension. The non-renormalizable theory is regularized on an anisotropic lattice and investigated through numerical simulations in a regime characterized by a hierarchy between the scale of low-energy physics, the inverse compactification radius, and the cutoff scale. We map out the structure of the phase diagram and the pattern of lines corresponding to fixed values of the ratio between the mass of the fifth component of the gauge field and the non-perturbative mass gap of the four-dimensional modes. We discuss different limits of the model, and comment on the implications of our findings.Comment: 17 pages, 9 figure

Electromagnetic fluxes, monopoles, and the order of the 4d compact U(1) phase transition

We consider the 4d compact U(1) gauge theory with extended action S=-beta sum_P cos theta_P -gamma sum_P cos 2 theta_P We give a full characterization of the phase diagram of this model using the notion of flux. The relation with the usual monopole picture is discussed. In analogy with the XY model we consider the helicity modulus \cite{Jose:1977gm} for this theory, and show that it is an order parameter. Analyzing the finite-size effects of the helicity modulus we conclude that the transition is first-order. The value of this order parameter is related to the renormalized coupling beta_R. We measure beta^c_R at the transition point and give a counterexample to its conjectured universal value \cite{Cardy:jg}