Divergence of the axial current and fermion density in Gross-Neveu models

The divergence of the axial current is used to relate the spatial derivative of the fermion density to the bare fermion mass and scalar/pseudoscalar condensates in 1+1 dimensional Gross-Neveu models. This serves as a novel test of known results, to explain simple features of the continuous chiral model and to resolve a conflict concerning the assignment of baryon number to certain multi-fermion bound states.Comment: 7 pages, no figure; v2: minor changes, reference adde

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

Integrating out the Dirac sea: Effective field theory approach to exactly solvable four-fermion models

We use 1+1 dimensional large N Gross-Neveu models as a laboratory to derive microscopically effective Lagrangians for positive energy fermions only. When applied to baryons, the Euler-Lagrange equation for these effective theories assumes the form of a non-linear Dirac equation. Its solution reproduces the full semi-classical results including the Dirac sea to any desired accuracy. Dynamical effects from the Dirac sea are encoded in higher order derivative terms and multi-fermion interactions with perturbatively calculable, finite coefficients. Characteristic differences between models with discrete and continuous chiral symmetry are observed and clarified.Comment: 13 pages, 11 figures; v2: typos corrected (Eqs. 4 and 44

Strong coupling of a qubit to shot noise

We perform a nonperturbative analysis of a charge qubit in a double quantum dot structure coupled to its detector. We show that strong detector-dot interaction tends to slow down and halt coherent oscillations. The transitions to a classical and a low-temperature quantum overdamping (Zeno) regime are studied. In the latter, the physics of the dissipative phase transition competes with the effective shot noise.Comment: 5 pages, 4 figure

Covariant boost and structure functions of baryons in Gross-Neveu models

Baryons in the large N limit of two-dimensional Gross-Neveu models are reconsidered. The time-dependent Dirac-Hartree-Fock approach is used to boost a baryon to any inertial frame and shown to yield the covariant energy-momentum relation. Momentum distributions are computed exactly in arbitrary frames and used to interpolate between the rest frame and the infinite momentum frame, where they are related to structure functions. Effects from the Dirac sea depend sensitively on the occupation fraction of the valence level and the bare fermion mass and do not vanish at infinite momentum. In the case of the kink baryon, they even lead to divergent quark and antiquark structure functions at x=0.Comment: 13 pages, 12 figures; v2: minor correction

Cotunneling at resonance for the single-electron transistor

We study electron transport through a small metallic island in the perturbative regime. Using a recently developed diagrammatic technique, we calculate the occupation of the island as well as the conductance through the transistor in forth order in the tunneling matrix elements, a process referred to as cotunneling. Our formulation does not require the introduction of a cut-off. At resonance we find significant modifications of previous theories and good agreement with recent experiments.Comment: 5 pages, Revtex, 5 eps-figure

Geometrical spin dephasing in quantum dots

We study spin-orbit mediated relaxation and dephasing of electron spins in quantum dots. We show that higher order contributions provide a relaxation mechanism that dominates for low magnetic fields and is of geometrical origin. In the low-field limit relaxation is dominated by coupling to electron-hole excitations and possibly $1/f$ noise rather than phonons.Comment: Replaced with final published versio

Utjecaj promijenjene mineralne ishrane na iglice Pančićeve omorike (Picea omorika Pančić) – istraživanje pojedinačnog slučaja

A widespread conifer forest decline in Europe and North America has been expressed through various combinations of symptoms. In our study, unspecific biochemical indicators and histological findings were compared with visually assessed damage symptoms in order to get a detailed diagnosis of a single declining Picea omorika Pančić tree. By measuring the content of photosynthetic pigments and proteins as well as total guaiacol peroxidase activity we confirmed an altered physiological state of the investigated tree. Histological analysis showed specific patterns of decline for Mg and K deficient trees.Sveprisutno propadanje šuma u Europi i sjevernoj Americi manifestira se kao kombinacija različitih simptoma. U provedenom istraživanju usporedili smo nespecifične biokemijske indikatore i histološke nalaze s vizualnom procjenom oštećenja, a s ciljem postavljanja detaljne dijagnoze propadanja jednog stabla Pančićeve omorike (Picea omorika Pančić). Odre|ivanjem sadržaja fotosintetskih pigmenata, proteina i aktivnosti ukupnih gvajacilnih peroksidaza potvr|ena je promjena fiziološkog statusa biljke. Histološke analize pokazale su specifičnosti karakteristične za stabla deficijentna magnezijem i kalijem

Utjecaj promijenjene mineralne ishrane na iglice Pančićeve omorike (Picea omorika Pančić) – istraživanje pojedinačnog slučaja

A widespread conifer forest decline in Europe and North America has been expressed through various combinations of symptoms. In our study, unspecific biochemical indicators and histological findings were compared with visually assessed damage symptoms in order to get a detailed diagnosis of a single declining Picea omorika Pančić tree. By measuring the content of photosynthetic pigments and proteins as well as total guaiacol peroxidase activity we confirmed an altered physiological state of the investigated tree. Histological analysis showed specific patterns of decline for Mg and K deficient trees.Sveprisutno propadanje šuma u Europi i sjevernoj Americi manifestira se kao kombinacija različitih simptoma. U provedenom istraživanju usporedili smo nespecifične biokemijske indikatore i histološke nalaze s vizualnom procjenom oštećenja, a s ciljem postavljanja detaljne dijagnoze propadanja jednog stabla Pančićeve omorike (Picea omorika Pančić). Odre|ivanjem sadržaja fotosintetskih pigmenata, proteina i aktivnosti ukupnih gvajacilnih peroksidaza potvr|ena je promjena fiziološkog statusa biljke. Histološke analize pokazale su specifičnosti karakteristične za stabla deficijentna magnezijem i kalijem