Tricritical behavior of the massive chiral Gross-Neveu model

The phase diagram of the massive chiral Gross-Neveu model (the 1+1-dimensional Nambu-Jona-Lasinio model at large N) is investigated in the vicinity of the tricritical point. Using the derivative expansion, the grand canonical potential is cast into the form of a Ginzburg-Landau effective action. Minimization of this action by variational and numerical methods reveals both 1st and 2nd order phase transitions to a chiral crystal phase, separated by a tricritical line. These findings are contrasted to the massive Gross-Neveu model with discrete chiral symmetry where only 2nd order transitions have been observed.Comment: 10 pages, 10 figures; v2: More details about perturbation theory given, cf Eqs. (46-48

From non-degenerate conducting polymers to dense matter in the massive Gross-Neveu model

Using results from the theory of non-degenerate conducting polymers like cis-polyacetylene, we generalize our previous work on dense baryonic matter and the soliton crystal in the massless Gross-Neveu model to finite bare fermion mass. In the large N limit, the exact crystal ground state can be constructed analytically, in close analogy to the bipolaron lattice in polymers. These findings are contrasted to the standard scenario with homogeneous phases only and a first order phase transition at a critical chemical potential.Comment: 12 pages, 7 figures, revtex; v2: improved readability, following advice of PRD referee; accepted for publicatio

Revised Phase Diagram of the Gross-Neveu Model

We confirm earlier hints that the conventional phase diagram of the discrete chiral Gross-Neveu model in the large N limit is deficient at non-zero chemical potential. We present the corrected phase diagram constructed in mean field theory. It has three different phases, including a kink-antikink crystal phase. All transitions are second order. The driving mechanism for the new structure of baryonic matter in the Gross-Neveu model is an Overhauser type instability with gap formation at the Fermi surface.Comment: Revtex, 12 pages, 15 figures; v2: Axis labelling in Fig. 9 correcte

The phase diagram of the massive Gross-Neveu model, revisited

The massive Gross-Neveu model is solved in the large N limit at finite temperature and chemical potential. The phase diagram features a kink-antikink crystal phase which was missed in previous works. Translated into the framework of condensed matter physics our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.Comment: revtex, 4 pages, 3 figures; v2: minor typos corrected; v3: minor corrections concerning figures 2 and

Fas and FasL expression in human adipose tissue is related to obesity, insulin resistance, and type 2 diabetes

Context: Deletion of the death receptor Fas (CD95) in adipocytes of mice is associated with improved insulin sensitivity and reduced adipose tissue (AT) inflammation. Objective: Here we investigate the relationship of AT Fas with human obesity. Design and Methods: In paired samples of omental and sc AT from 256 lean and obese (including insulin-sensitive and insulin-resistant subgroups; n = 60) participants, we investigated whether Fas and Fas-ligand (FasL) mRNA expression is fat depot-specific, altered in obesity, and related to measures of AT inflammation and insulin sensitivity. In addition, AT Fas mRNA expression was measured in 16 obese patients after significant weight loss of 45 ± 6.3 kg in the context of a two-step bariatric surgery strategy. Results: Fas and FasL are significantly higher expressed in omental (OM) compared to sc AT. Fas expression correlates with body mass index (OM, r(2) = 0.44; sc, r(2) = 0.14), AT macrophage infiltration (OM, r(2) = 0.36; sc, r(2) = 0.16), and glucose infusion rate in euglycemic-hyperinsulinemic clamps (OM, r(2) = 0.17; sc, r(2) = 0.13) (P < .05 for all). FasL expression most strongly correlates with adipocyte size (OM, r(2) = 0.32; sc, r(2) = 0.17) and AT macrophage infiltration (OM, r(2) = 0.46; sc, r(2) = 0.02). Insulin-sensitive obese individuals had significantly lower Fas and FasL expression than insulin-resistant obese individuals. Significant weight loss 12 months after gastric sleeve resection is associated with a significantly reduced Fas expression in OM and sc fat depots. Conclusions: Independently of body weight, increased Fas expression may contribute to impaired insulin sensitivity and AT dysfunction in obesity. Moreover, significant weight loss reduces Fas expression in OM and sc fat depots

First observation of in-medium modifications of the omega meson

The photoproduction of omega mesons on nuclei has been investigated using the Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The aim is to study possible in-medium modifications of the omega meson via the reaction A(gamma, omega)X. Results obtained for Nb are compared to a reference measurement on a liquid hydrogen target. While for recoiling, long-lived mesons (pi, eta and etaprime), which decay outside of the nucleus, a difference in the lineshape for the two data samples is not observed, we find a significant enhancement towards lower masses for omega mesons with low momenta produced on the Nb target.Comment: Latex, 4 pages, 4 figures, accepted by Phys. Rev. Lett; references re-arranged, now references in chronological order in first paragrap