相关论文: Local topological and chiral properties of QCD

We construct a model to study the impact of instantons on the low lying eigenvalue spectrum of the Dirac operator. The model is by necessity, approximate, though it does incorporate the important symmetries of the underlying field theory.…

We investigate the contribution that instantons make to the QCD chiral condensate for Nf= 0, 1 and 2 quark flavours. We use a simplified model: the instantons are a (weighted) gas, the fermionic integrations are restricted to the subspace…

This is a review of the QCD instanton vacuum. After introducing instantons and their physical meaning, I show that the number of instantons in the vacuum fluctuates in accordance with the QCD trace anomaly. The main properties of the…

In QCD the spontaneous breaking of chiral symmetry and the U(1) axial anomaly can be understood considering instantons as the gauge configurations mediating quark-quark interaction. The existence of an exact zero mode solution of the Dirac…

We review the theory and phenomenology of instantons in QCD. After a general overview, we provide a pedagogical introduction to semi-classical methods in quantum mechanics and field theory. The main part of the review summarizes our…

We investigate the contribution of instantons to the eigenvalue spectrum of the Dirac operator in quenched QCD. The instanton configurations that we use have been derived, elsewhere, from cooled SU(3) lattice gauge fields and, for…

A chiral fermion action allows one to do very clean studies of chiral symmetry breaking in QCD. I will briefly describe how to compute with the overlap action (relatively) cheaply, and then turn to physics: Low modes of the Dirac operator…

We calculate the spectral density of the Dirac operator over an ensemble of configurations composed of overlapping instantons and anti-instantons. We find evidence that the spectral density diverges in the limit of small eigenvalues. This…

We address the question of whether the low modes of the Dirac operator are caused by topological objects such as instantons in SU(N) gauge theories. We study the pseudo-scalar density of these modes, finding the size distributions of the…

The chiral phase transition of QCD is analyzed in a model combining random matrix elements of the Dirac operator with specially chosen non-random ones. The special form of the latter is motivated by the assumption that the fermionic…

This talk is a review of our studies of instantons and their properties as seen in our lattice simulations of SU(2) gauge theory. We have measured the topological susceptibility and the size distribution of instantons in the QCD vacuum. We…

We use low lying eigenvectors of the overlap-Dirac operator as a probe of the QCD vacuum. If instantons play a significant role one would expect the low lying eigenmodes of the overlap-Dirac operator to consist mainly of the mixed ``would…

The aim of this review is to demonstrate that there exists a coherent picture of strong interactions, based on instantons. Starting from the first principles of QCD - via the microscopic mechanism of spontaneous chiral symmetry breaking -…

This study is part of a research program aimed to investigate the relations between instantons, monopoles, and chiral symmetry breaking. Monopoles are important 3-dimensional topological configurations existing in QCD, which are believed to…

We discuss the spontaneous breakdown of chiral symmetry in Quantum Chromodynamics by considering gluonic instanton configurations in the partition function. It is shown that in order to obtain nontrivial fermionic correlators in a two…

We show, without using semiclassical approximations, that, in high-temperature QCD with chiral symmetry restoration and U(1) axial symmetry breaking, the partition function for sufficiently light quarks can be expressed as an ensemble of…

We explore the idea that the chiral phase transition in QCD can be described as a transition from a disordered instanton liquid to a strongly correlated phase of polarized instanton anti-instanton molecules. We find a number of non…

The local structure of low-lying eigenmodes of the overlap Dirac operator is studied. It is found that these modes cannot be described as linear combinations of 't Hooft "would-be" zeromodes associated with instanton excitations that…

We discuss the construction and properties of an approximate solution of the Ginsparg-Wilson equation, the so-called chirally improved lattice Dirac operator. In particular we study the behavior of its eigenmodes in smooth instanton…

We investigate the realization of chiral symmetry in the vicinity of the deconfinement transition in quenched QCD using overlap fermions. Via the index theorem obeyed by the overlap fermions, we gain insight into the behavior of topology at…