85 research outputs found
Two-Dimensional Bosonization from Variable Shifts in the Path Integral
A method to perform bosonization of a fermionic theory in (1+1) dimensions in
a path integral framework is developed. The method relies exclusively on the
path integral property of allowing variable shifts, and does not depend on the
explicit form of Greens functions. Two examples, the Schwinger model and the
massless Thirring model, are worked out.Comment: 4 page
Fermion Condensates of massless at Finite Density in non-trivial Topological Sectors
Vacuum expectation values of products of local bilinears are
computed in massless at finite density. It is shown that chiral
condensates exhibit an oscillatory inhomogeneous behaviour depending on the
chemical potential. The use of a path-integral approach clarifies the
connection of this phenomenon with the topological structure of the theory.Comment: 16 pages, no figures, To be published in Phys.Rev.
Smooth Bosonization II: The Massive Case
The (1+1)-dimensional bosonization relations for fermionic mass terms are
derived by choosing a specific gauge in an enlarged gauge-invariant theory
containing both fermionic and bosonic fields. The fermionic part of the
generating functional subject to the gauge constraint can be cast into the form
of a strongly coupled Schwinger model, which can be solved exactly. The
resulting bosonic theory coupled to the scalar sources then exhibits directly
the bosonic counterparts of the fermionic scalar and pseudoscalar mass
densities.Comment: 8 pages, Latex, CERN-TH-6563/9
Numerical study of the critical behavior of the Ashkin-Teller model at a line defect
We consider the Ashkin-Teller model on the square lattice, which is
represented by two Ising models ( and ) having a four-spin
coupling of strength, , between them. We introduce an asymmetric
defect line in the system along which the couplings in the Ising model
are modified. In the Hamiltonian version of the model we study the scaling
behavior of the critical magnetization at the defect, both for and for
spins by density matrix renormalization. For we observe
identical scaling for and spins, whereas for one
model becomes locally ordered and the other locally disordered. This is
different of the critical behavior of the uncoupled model () and is
in contradiction with the results of recent field-theoretical calculations.Comment: 6 pages, 4 figure
A gauge invariant and string independent fermion correlator in the Schwinger model
We introduce a gauge invariant and string independent two-point fermion
correlator which is analyzed in the context of the Schwinger model (QED_2). We
also derive an effective infrared worldline action for this correlator, thus
enabling the computation of its infrared behavior. Finally, we briefly discuss
possible perspectives for the string independent correlator in the QED_3
effective models for the normal state of HTc superconductors.Comment: 14 pages, LaTe
Multiflavor Correlation Functions in non-Abelian Gauge Theories at Finite Density in two dimensions
We compute vacuum expectation values of products of fermion bilinears for
two-dimensional Quantum Chromodynamics at finite flavored fermion densities. We
introduce the chemical potential as an external charge distribution within the
path-integral approach and carefully analyse the contribution of different
topological sectors to fermion correlators. We show the existence of chiral
condensates exhibiting an oscillatory inhomogeneous behavior as a function of a
chemical potential matrix. This result is exact and goes in the same direction
as the behavior found in QCD_4 within the large N approximation.Comment: 28 pages Latex (3 pages added and other minor changes) to appear in
Phys.Rev.
potential in the Schwinger model on curved space - time
We study the confining and screening aspects of the Schwinger model on curved
static backgrounds.Comment: 14 pages, Latex. Typos corrected. Erratum submitte
Role of mitochondrial raft-like microdomains in the regulation of cell apoptosis
Lipid rafts are envisaged as lateral assemblies of specific lipids and proteins that dissociate and associate rapidly and form functional clusters in cell membranes. These structural platforms are not confined to the plasma membrane; indeed lipid microdomains are similarly formed at subcellular organelles, which include endoplasmic reticulum, Golgi and mitochondria, named raft-like microdomains. In addition, some components of raft-like microdomains are present within ER-mitochondria associated membranes. This review is focused on the role of mitochondrial raft-like microdomains in the regulation of cell apoptosis, since these microdomains may represent preferential sites where key reactions take place, regulating mitochondria hyperpolarization, fission-associated changes, megapore formation and release of apoptogenic factors. These structural platforms appear to modulate cytoplasmic pathways switching cell fate towards cell survival or death. Main insights on this issue derive from some pathological conditions in which alterations of microdomains structure or function can lead to severe alterations of cell activity and life span. In the light of the role played by raft-like microdomains to integrate apoptotic signals and in regulating mitochondrial dynamics, it is conceivable that these membrane structures may play a role in the mitochondrial alterations observed in some of the most common human neurodegenerative diseases, such as Amyotrophic lateral sclerosis, Huntington's chorea and prion-related diseases. These findings introduce an additional task for identifying new molecular target(s) of pharmacological agents in these pathologies
Production of mesons by high energy neutrinos from the Tevatron
Charged vector meson production is studied in a high energy neutrino bubble chamber experiment with mean neutrino energy of 141 GeV. The are produced in of the neutrino charged current interactions, indicating a steep increase of cross section with energy. The mean fractional hadronic energy of the meson is
A membrane-inserted structural model of the yeast mitofusin Fzo1
Mitofusins are large transmembrane GTPases of the dynamin-related protein family, and are required for the tethering and fusion of mitochondrial outer membranes. Their full-length structures remain unknown, which is a limiting factor in the study of outer membrane fusion. We investigated the structure and dynamics of the yeast mitofusin Fzo1 through a hybrid computational and experimental approach, combining molecular modelling and all-atom molecular dynamics simulations in a lipid bilayer with site-directed mutagenesis and in vivo functional assays. The predicted architecture of Fzo1 improves upon the current domain annotation, with a precise description of the helical spans linked by flexible hinges, which are likely of functional significance. In vivo site-directed mutagenesis validates salient aspects of this model, notably, the long-distance contacts and residues participating in hinges. GDP is predicted to interact with Fzo1 through the G1 and G4 motifs of the GTPase domain. The model reveals structural determinants critical for protein function, including regions that may be involved in GTPase domain-dependent rearrangements
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