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A brief review review is presented of models tentatively leading to stable multiquarks. A new attempt is presented, based on a Steiner-tree model of confinement, which is inspired by by QCD. It leads to more attraction than the empirical colour-additive model used in earlier multiquark calculations, and predict several multiquark states in configurations with different flavours. [ABSTRACT FROM AUTHOR]

The long standing problem is solved why the number and the location of monopoles observed in Lattice configurations depend on the choice of the gauge used to detect them, in contrast to the obvious requirement that monopoles, as physical objects, must have a gauge-invariant status. It is proved, by use of non-abelian Bianchi identities, that monopoles are indeed gauge-invariant: the technique used to detect them has instead an efficiency which depends on the choice of the abelian projection, in a known and controllable way. [ABSTRACT FROM AUTHOR]

We describe an extension of the hadronic SU(3) non-linear sigma model to include quarks. As a result, we obtain an effective model which interpolates between hadronic and quark degrees of freedom. The new parameters and the potential for the Polyakov loop (used as the order parameter for deconfinement) are calibrated in order to fit lattice QCD data and reproduce the QCD phase diagram. Finally, the equation of state provided by the model, combined with gravity through the inclusion of general relativity, is used to make predictions for neutron stars. [Copyright &y& Elsevier]

The Duffin-Kemmer-Petiau (DKP) equation, in the scalar sector of the theory and with a linear nonminimal vector potential, is mapped into the nonrelativistic harmonic oscillator problem. The behavior of the solutions for this sort of vector DKP oscillator is discussed in detail. [Copyright &y& Elsevier]

Within a formulation of a Dynamical AdS/QCD model we calculate the spectrum of light flavored mesons. The background fields of the model correspond to an IR deformed Anti de Sitter metric coupled to a dilaton field. Confinement comes as a consequence of the dilaton dynamics coupled to gravity. Additionally to the Regge-like spectrum of light- scalar, vector and higher spin mesons, we obtain the decay width of scalar mesons into two pions. [Copyright &y& Elsevier]

The mechanism of spontaneous chiral symmetry χSB is defined as a statement on the fermion fock space consistent with the interaction. The consequences of χSB are briefly explained together with its extension to non zero temperature [Copyright &y& Elsevier]

Some of the difficulties arising when one tries to understand confinement as well as dynamical and anomalous chiral symmetry breaking are briefly reviewed. Criteria to be fulfilled by a successful and complete picture of these phenomena are presented, and a few of the suggested explanations are listed. [Copyright &y& Elsevier]

The trace anomaly of gluodynamics encodes the breakdown of classical scale invariance due to interactions around the deconfinement phase transition. While it is expected that at high temperatures perturbation theory becomes applicable we show that current lattice calculations are far from the perturbative regime and are dominated instead by inverse even power corrections in the temperature, while the total perturbative contribution is estimated to be extremely small and compatible with zero within error bars. We provide an interpretation in terms of dimension-two gluon condensate of the dimensionally reduced theory which value agrees with a similar analysis of power corrections from available lattice data for the renormalized Polyakov loop and the heavy quark-antiquark free energy in the deconfined phase of QCD [E. Megías, E. Ruiz Arriola and L. L. Salcedo, JHEP 0601 (2006) 073; E. Megías, E. Ruiz Arriola and L. L. Salcedo, Phys. Rev. D75 (2007) 105019]. [Copyright &y& Elsevier]

This is a combined and slightly expanded version of talks delivered at 14th International QCD Conference “QCD 08,” 7-12th July 2008, Montpellier, France, the International Conference “Quark Confinement and the Hadron Spectrum,” Mainz, Germany, September 1-6, 2008 (Confinement 08), and the International Conference “Approaches to Quantum Chromodynamics,” Oberwölz, Austria, September 7-13, 2008. [Copyright &y& Elsevier]

The excitation of nucleon resonances in electromagnetic interaction has long been studied. The study of resonances helps us to understand the long- and short- range structures of the nucleon and its excited states in terms of quark confinement. While the existing data of the low-lying resonances are consistent with the well-studied SU(6) ⊗O(3) constituent quark model classification, many open questions still remain. Exclusive electro-production is one of the best ways to investigate nucleon resonances. The exclusive electro-production process was measured in the photon virtuality range Q 2 = 1.7 – 4.5 GeV2 and the invariant mass range for the nπ + system of W = 1.15 – 1.7 GeV using the CEBAF Large Acceptance Spectrometer. For the first time, these kinematics are probed in exclusive π + production from protons with nearly full coverage in the azimuthal and polar angles of the nπ + center-of-mass system. The nπ + channel has particular sensitivity to the isospin excited nucleon states, and together with the pπ 0 final state will serve to determine the transition form factors of a large number of resonances. The largest discrepancy between these results and present modes was seen in the structure function. Thanks to a large volume of data (31,295 cross section and 4,184 asymmetry data points), a reduced set of structure functions and Legendre polynomial moments are presented which are obtained in model-independent fits to the differential cross sections. In this paper, I will discuss the transition form factors of the nucleon resonances in terms of helicity amplitudes. [Copyright &y& Elsevier]

A brief review of vector mesons made of light quarks is presented. [Copyright &y& Elsevier]

In this review we discuss the general features of maximally twisted lattice QCD. In particular, we illustrate how automatic O(a) improvement can be achieved and how it is possible to set up a lattice regularization scheme where the problem of wrong chirality mixing (be it finite or infinite) affecting the computation of the matrix elements of the -conserving effective weak Hamiltonian is neatly avoided, while having at the same time a positive determinant even for non-degenerate quark pairs. The question of reducing the large cutoff effects that appear when the quark mass tends to zero as a consequence of parity and iso-spin breaking in the action is also addressed. It is shown that such dangerous lattice artifacts are strongly suppressed if the clover term is added to the action or, alternatively, the critical mass is chosen so as to enforce the restoration of parity. [Copyright &y& Elsevier]

The Yang-Mills Schrödinger equation is variationally solved in Coulomb gauge for the vacuum sector using a trial wave functional, which uses a Gaussian for the radial wave functional. The resulting Schwinger-Dyson equations are, for the first time, solved in a fully self-consistent way. We find the absence of gluons in the infrared and also a confining quark potential. Confinement is shown to be a consequence of the curvature of the space of gauge orbits. [Copyright &y& Elsevier]

We discuss the localization of eigenmodes of the covariant lattice Laplacian and overlap Dirac operator in lattice SU(2) gluodynamics. It occurs that the localization properties of the eigenmodes for fundamental scalars and fermions are different in confining configurations and in those from which confining disorder was eliminated by center-vortex removal. Localization of eigenmodes on subspaces of dimension less than four indicates the existence of the low dimensional structures in the confining vacuum. [Copyright &y& Elsevier]

The role of the center of the gauge group in the phenomenon of confinement in Yang-Mills theory is investigated. Starting from the most general perspective of considering all possible choices for the gauge symmetry group, we then focus on Yang-Mills theory: the simplest pure gauge theory with a trivial center and without ''t Hooft flux vortices. Numerical simulations show the presence of a first order finite temperature deconfinement phase transition in Yang-Mills theory in (3+1) dimensions. Interestingly, the gauge symmetry can be broken to an subgroup by the Higgs mechanism. We investigate the relation between the deconfinement phase transition in and Yang-Mills theories by numerical simulations in the gauge-Higgs system. [Copyright &y& Elsevier]

Baryons are described as bound states of quarks and scalar as well as axialvector diquarks. In order to effectively parametrize confinement several ansaetze for the dressing functions of the constituent propagators are used. The corresponding results for electromagnetic and strong form factors differ only slightly. On the other hand observables from production processes show the permissibility of different dressing functions. [Copyright &y& Elsevier]