The Gluon Propagator on a Large Volume, at β=6.0\beta=6.0

We present the results of a high statistics lattice study of the gluon propagator, in the Landau gauge, at $\beta=6.0$. As suggested by previous studies, we find that, in momentum space, the propagator is well described by the expression $G(k^2)= \Big[ M^2 + Z\cdot k^2(k^2/\Lambda^2)^\eta\Big]^{-1}$. By comparing $G(k^2)$ on different volumes, we obtain a precise determination of the exponent $\eta=0.532(12)$, and verify that $M^2$ does not vanish in the infinite volume limit. The behaviour of $\eta$ and $M^2$ in the continuum limit is not known, and can only be studied by increasing the value of $\beta$.Comment: 21 pages, uuencoded LATEX plus 5 postscript figures. ROME prep. 94/1042, SHEP prep. 93/94-3

Four Loop Result in SU(3)SU(3) Lattice Gauge Theory by a Stochastic Method: Lattice Correction to the Condensate

We describe a stochastic technique which allows one to compute numerically the coefficients of the weak coupling perturbative expansion of any observable in Lattice Gauge Theory. The idea is to insert the exponential representation of the link variables $U_\mu(x) \to \exp\{A_\mu(x)/\sqrt\beta\}$ into the Langevin algorithm and the observables and to perform the expansion in \beta^{-1/2}. The Langevin algorithm is converted into an infinite hierarchy of maps which can be exactly truncated at any order. We give the result for the simple plaquette of SU(3) up to fourth loop order (\beta^{-4}) which extends by one loop the previously known series.Comment: 9 pages. + 5 figures (postscript) appended at the end, (University of Parma, Dept.of Physics, report uprf-397-1994

Asymptotic scaling of the gluon propagtor on the lattice

We pursue the study of the high energy behaviour of the gluon propagator on the lattice in the Landau gauge in the flavorless case (n_f=0). It was shown in a precedin g paper that the gluon propagator did not reach three-loop asymptotic scaling at an energy scale as high as 5 GeV. Our present high statistics analysis includes also a simulation at $\beta=6.8$ ($a\simeq 0.03$ fm), which allows to reach $\mu \simeq 10$ GeV. Special care has been devoted to the finite lattice-spacing artifacts as well as to the finite volume effects, the latter being acute at $\beta=6.8$ where the volume is bounded by technical limits. Our main conclusion is a strong evidence that the gluon propagator has reached three-loop asymptotic scaling, at $\mu$ ranging from 5.6 GeV to 9.5 GeV. We buttress up this conclusion on several demanding criteria of asymptoticity, including scheme independence. Our fit in the 5.6 GeV to 9.5 GeV window yields $\Lambda^{\bar{{\rm MS}}} = 319 \pm 14 ^{+10}_{-20}$ MeV, in good agreement with our previous result, $\Lambda^{\bar{{\rm MS}}} = 295 \pm 20$ MeV, obtained from the three gluon vertex, but it is significantly above the Schr\"odinger functional method estimate : $238 \pm 19$ MeV. The latter difference is not understood. Confirming our previous paper, we show that a fourth loop is necessary to fit the whole ($2.8 \div 9.5$) GeV energy window.Comment: latex-file, 19 pgs., 6 fig

Gluon Propagator in the Infrared Region

The gluon propagator is calculated in quenched QCD for two different lattice sizes (16^3x48 and 32^3x64) at beta=6.0. The volume dependence of the propagator in Landau gauge is studied. The smaller lattice is instrumental in revealing finite volume and anisotropic lattice artefacts. Methods for minimising these artefacts are developed and applied to the larger lattice data. New structure seen in the infrared region survives these conservative cuts to the lattice data. This structure serves to rule out a number of models that have appeared in the literature. A fit to a simple analytical form capturing the momentum dependence of the nonperturbative gluon propagator is also reported.Comment: 13 pages, 9 figures, using RevTeX. Submitted to Phys. Rev. D. This and related papers can also be obtained from http://www.physics.adelaide.edu.au/~jskuller/papers

Confinement and the photon propagator in 3D compact QED: a lattice study in Landau gauge at zero and finite temperature

On the lattice we study the gauge boson propagator of three dimensional compact QED in Landau gauge at zero and non-zero temperature. The non-perturbative effects are taken into account by the generation of a mass, by an anomalous dimension and by the photon wave function renormalization. All these effects can be attributed to the monopoles: they are absent in the propagator of the singularity-free part of the gauge field. We assess carefully the Gribov copy problem for the propagator and the parameters emerging from the fits.Comment: 25 pages, 32 figures, RevTeX 4; version in print in Phys. Rev. D; typos and figures 5c and 7c correcte

Evidence for tuning adipocytes ICER levels for obesity care.

Abnormal adipokine production, along with defective uptake and metabolism of glucose within adipocytes, contributes to insulin resistance and altered glucose homeostasis. Recent research has highlighted one of the mechanisms that accounts for impaired production of adiponectin (ADIPOQ) and adipocyte glucose uptake in obesity. In adipocytes of human obese subjects and mice fed with a high fat diet, the level of the inducible cAMP early repressor (ICER) is diminished. Reduction of ICER elevates the cAMP response element binding protein (CREB) activity, which in turn increases the repressor activating transcription factor 3. In fine, the cascade triggers reduction in the ADIPOQ and GLUT4 levels, which ultimately hampers insulin-mediated glucose uptake. The c-Jun N-terminal kinase (JNK) interacting-protein 1, also called islet brain 1 (IB1), is a target of CREB/ICER that promotes JNK-mediated insulin resistance in adipocytes. A rise in IB1 and c-Jun levels accompanies the drop of ICER in white adipose tissues of obese mice when compared with mice fed with a chow diet. Other than the expression of ADIPOQ and glucose transport, decline in ICER expression might impact insulin signaling. Impairment of ICER is a critical issue that will need major consideration in future therapeutic purposes

Photon propagator, monopoles and the thermal phase transition in 3D compact QED

We investigate the gauge boson propagator in three dimensional compact Abelian gauge model in the Landau gauge at finite temperature. The presence of the monopole plasma in the confinement phase leads to appearance of an anomalous dimension in the momentum dependence of the propagator. The anomalous dimension as well as an appropriate ratio of photon wave function renormalization constants with and without monopoles are observed to be order parameters for the deconfinement phase transition. We discuss the relation between our results and the confining properties of the gluon propagator in non--Abelian gauge theories.Comment: 4 pages, 5 EPS figures, RevTeX 4, uses epsfig.sty; repaced to match version accepted for publication in Phys. Rev. Lett. (discussion on fits is extended

Soft Covariant Gauges on the Lattice

We present an exploratory study of a one-parameter family of covariant, non-perturbative lattice gauge-fixing conditions, that can be implemented through a simple Monte Carlo algorithm. We demonstrate that at the numerical level the procedure is feasible, and as a first application we examine the gauge dependence of the gluon propagator.Comment: 11 pages, Latex, epsf.sty included + 5 PostScript picture

Intra-articular administration of lidocaine plus adrenaline in dogs : pharmacokinetic profile and evaluation of toxicity in vivo and in vitro

The aim of this study was to evaluate the safety of intra-articular (IA) lidocaine plus adrenaline for improving peri-operative analgesia in anaesthetised dogs undergoing arthroscopy of the elbow. A solution of lidocaine (L) 1.98% plus adrenaline 1:100.000 was administered via the IA route and its safety evaluated in terms of cardio- neuro- and chondro-toxicity. No bradycardia or hypotension was recorded from induction to the last observational time point. Signs of toxicity of the nervous system could have been masked by the general anaesthesia but lidocaine concentrations detected in the blood were lower than those thought to be capable of producing toxicity. The assessment of in vitro chondrotoxicity showed a dose- and time-dependent effect of lidocaine on the viability of articular cells. Adrenaline appeared to reduce the chondrotoxicity of 1% lidocaine, following an exposure of up to 30 min