Non-perturbative solutions of the SD equation for an Abelian gauge field theory

In this article we present a mechanism in which we find new non-perturbative solutions of quantum electrodynamics in four dimensions. Two non-perturbative solutions are found for approximate Schwinger-Dyson equations. The mass ratio of the three solutions (one is ordinary solution) is approximately $1:(8\pi/\alpha)^{2/3}:8\pi/\alpha$.Comment: 6 pages, no figur

Transverse Ward-Takahashi Identity, Anomaly and Schwinger-Dyson Equation

Based on the path integral formalism, we rederive and extend the transverse Ward-Takahashi identities (which were first derived by Yasushi Takahashi) for the vector and the axial vector currents and simultaneously discuss the possible anomaly for them. Subsequently, we propose a new scheme for writing down and solving the Schwinger-Dyson equation in which the the transverse Ward-Takahashi identity together with the usual (longitudinal) Ward-Takahashi identity are applied to specify the fermion-boson vertex function. Especially, in two dimensional Abelian gauge theory, we show that this scheme leads to the exact and closed Schwinger-Dyson equation for the fermion propagator in the chiral limit (when the bare fermion mass is zero) and that the Schwinger-Dyson equation can be exactly solved.Comment: 22 pages, latex, no figure

Interacting with digital media at home via a second screen

In recent years Interactive Television (iTV) has become a household technology on a global scale. However, iTV is still a new technology in the early stages of its evolution. Our previous research looked at how everyday users of iTV feel about the interactive part of iTV. In a series of studies we investigated how people use iTV services; their likes, dislikes, preferences and opinions. We then developed a second screen-based prototype device in response to these findings and tested it with iTV users in their own homes. This is a work in progress paper that outlines the work carried previously in the area of controlling interactive Television via a second screen. The positive user responses led us to extend the scope of our previous research to look into other related areas such as barriers to digital interactive media and personalisation of digital interactive media at home

On ghost condensation, mass generation and Abelian dominance in the Maximal Abelian Gauge

Recent work claimed that the off-diagonal gluons (and ghosts) in pure Yang-Mills theories, with Maximal Abelian gauge fixing (MAG), attain a dynamical mass through an off-diagonal ghost condensate. This condensation takes place due to a quartic ghost interaction, unavoidably present in MAG for renormalizability purposes. The off-diagonal mass can be seen as evidence for Abelian dominance. We discuss why ghost condensation of the type discussed in those works cannot be the reason for the off-diagonal mass and Abelian dominance, since it results in a tachyonic mass. We also point out what the full mechanism behind the generation of a real mass might look like.Comment: 7 pages; uses revtex

Spontaneous Chiral-Symmetry Breaking in Three-Dimensional QED with a Chern--Simons Term

In three-dimensional QED with a Chern--Simons term we study the phase structure associated with chiral-symmetry breaking in the framework of the Schwinger--Dyson equation. We give detailed analyses on the analytical and numerical solutions for the Schwinger--Dyson equation of the fermion propagator, where the nonlocal gauge-fixing procedure is adopted to avoid wave-function renormalization for the fermion. In the absence of the Chern--Simons term, there exists a finite critical number of four-component fermion flavors, at which a continuous (infinite-order) chiral phase transition takes place and below which the chiral symmetry is spontaneously broken. In the presence of the Chern--Simons term, we find that the spontaneous chiral-symmetry-breaking transition continues to exist, but the type of phase transition turns into a discontinuous first-order transition. A simple stability argument is given based on the effective potential, whose stationary point gives the solution of the Schwinger-Dyson equation.Comment: 34 pages, revtex, with 9 postscriptfigures appended (uuencoded

Canted Ferromagnetism in Double Exchange Model with on-site Coulomb Repulsion

The double exchange model with on-site Coulomb repulsion is considered. Schwinger-bosons representation of the localized spins is used and two spin-singlet Fermion operators are introduced. In terms of the new Fermi fields the on-site Hund's interaction is in a diagonal form and the true magnons of the system are identified. The singlet fermions can be understood as electrons dressed by a cloud of repeatedly emitted and reabsorbed magnons. Rewritten in terms of Schwinger-bosons and spin-singlet fermions the theory is U(1) gauge invariant. We show that spontaneous breakdown of the gauge symmetry leads to \emph{\textbf{canted ferromagnetism with on-site spins of localized and delocalized electrons misaligned}}. On-site canted phase emerges in double exchange model when Coulomb repulsion is large enough. The quantum phase transition between ferromagnetism and canted phase is studied varying the Coulomb repulsion for different values of parameters in the theory such as Hund's coupling and chemical potential.Comment: 8 pages, 6 figure

Ensemble of Vortex Loops in the Abelian-Projected SU(3)-Gluodynamics

Grand canonical ensemble of small vortex loops emerging in the London limit of the effective Abelian-projected theory of the SU(3)-gluodynamics is investigated in the dilute gas approximation. An essential difference of this system from the SU(2)-case is the presence of two interacting gases of vortex loops. Two alternative representations for the partition function of such a grand canonical ensemble are derived, and one of them, which is a representation in terms of the integrals over vortex loops, is employed for the evaluation of the correlators of both kinds of loops in the low-energy limit.Comment: 10 pages, LaTeX2e, no figures, minor corrections, to appear in Mod. Phys. Lett.

Superconductivity Under Pressure in FeSe1-xTex Studied by DC Magnetic Measurements

AbstractSuperconductivity under pressure in FeSe1−xTex with x=0.7 (TC∽14K) has been investigated by the measurements of DC magnetization using high quality single crystal specimens. It has been found that TC increases and makes a maximum of ∽15K at 1GPa but rapidly decreases above 1GPa under hydrostatic pressure using liquid Ar as pressure transmitting media (PTM). In contrast, TC is found to increase up to 18K at 2.5GPa then decrease gradually under nearly uniaxial pressure along c-axis using NaCl as PTM. It is also found that TC reaches a maximum of 16K at 1GPa but is nearly pressure independent above 1GPa under nearly uniaxial pressure along a-axis. These behaviors suggest that the superconductivity is suppressed by the isotropic compression but is enhanced (not changed) by the uniaxial compression along c-axis (a-axis)

The design and thermo-structural analysis of target assembly for high intensity neutron source

The engineering design of an integrated target assembly of IFMIF lithium target was performed in IFMIF/EVEDA project for a high intensity neutron source. In the evaluation of the design, a thermos-structural analysis of was evaluated by ABAQUS code, and the modeling region was a part of the target assembly which was from the inlet nozzle to the outlet pipe. The material of the target assembly including the back plate was F82H steel. In the thermal-structural analysis, the normal operations and start/stop or abnormal operations were evaluated at 250 or 300 °C operation of Li flow in inlet pipe. The result showed that the temperature of the target assembly was evaluated to be still lower than the Li boiling point of 344 °C under a vacuum pressure of 10−3 Pa. In a temperature constant operation, the calculated stresses and displacements were small enough for thermal soundness of the target assembly in steady states. In a transient cooling process from 300 °C to 20 °C through 250 °C, the maximum Mises stress was found to be 372 MPa, which was lower than the yield stress at 300 °C. Keywords: High intensity neutron source, Target assembly, Thermo-structural analysis, Li target, IFMIF, F82

Theory of Orbital Kondo Effect with Assisted Hopping in Strongly Correlated Electron Systems: Parquet Equations, Superconductivity and Mass Enhancement

Orbital Kondo effect is treated in a model, where additional to the conduction band there are localized orbitals close to the Fermi energy. If the hopping between the conduction band and the localized heavy orbitals depends on the occupation of the atomic orbitals in the conduction band then orbital Kondo correlation occurs. The noncommutative nature of the coupling required for the Kondo effect is formally due to the form factors associated with the assisted hopping which in the momentum representation depends on the momenta of the conduction electrons involved. The leading logarithmic vertex corrections are due to the local Coulomb interaction between the electrons on the heavy orbital and in the conduction band. The renormalized vertex functions are obtained as a solution of a closed set of differential equations and they show power behavior. The amplitude of large renormalization is determined by an infrared cutoff due to finite energy and dispersion of the heavy particles. The enhanced assisted hopping rate results in mass enhancement and attractive interaction in the conduction band. The superconductivity transition temperature calculated is largest for intermediate mass enhancement, $m^*/m \approx 2-3$. For larger mass enhancement the small one particle weight ($Z$) in the Green's function reduces the transition temperature which may be characteristic for otherComment: 32 pages, RevTeX 3.0, figures on reques