Related papers: QCD strings and the U(1) problem
The low-lying eigenmodes of the Dirac operator associated with typical gauge field configurations in QCD encode, among other low-energy properties, the physics behind the solution to the $U_A(1)$ problem (i.e. the origin of the $\eta'$…
Vacuum of Quantum Chromodynamics in very strong (hadron-scale) magnetic fields exhibits many interesting nonperturbative effects. Some of these effects can be studied with the help of lattice simulations in quenched QCD. We review our…
We consider the quantum chromodynamics (QCD) Kondo effect for a single heavy quark in quark matter composed of light quarks with chiral symmetry breaking. Introducing several spinor structures in QCD Kondo condensates, i.e.,…
QCD, the theory of the strong interactions, involves quarks interacting with non-Abelian gluon fields. This theory has many features that are difficult to impossible to see in conventional diagrammatic perturbation theory. This includes…
We show that several types of global strings occur in colour superconducting quark matter due to the spontaneous violation of relevant U(1) symmetries. These include the baryon U(1)_B, and approximate axial U(1)_A symmetries as well as an…
QCD perturbation theory using quark and gluon propagators that have an extra term at zero four-momentum is equivalent to standard PQCD in the presence of massless quark and gluon pairs in the perturbative vacuum. We verify at low orders in…
We show how the gauge invariant formulation of QCD in terms of loops is free from a hidden $\theta$ parameter and offers an alternative way to solve the $U(1)_A$ puzzle.
While it is clear that in some kinematic regime QCD can be described by an effective (as opposed to fundamental) string theory, it is not at all clear how this string theory should be. The `natural' candidate, the bosonic string, leads to…
By matching the world of hadrons to that of some effective chiral quark theory, we determine the induced condensates for QCD sum rules in the presence of an external pion field. The observed values of the strong and weak $\pi NN$ coupling…
A possibility is discussed that new nontrivial Chern-Simons like terms may be generated in (3+1)--dimensional QED Lagrangian, when induced by quark loops interacting with a non-abelian background field in an SU(2) model of QCD.
Both in electroweak theory and QCD, the vacuum in strong magnetic fields develops charged vector condensates once a critical value of the magnetic field is reached. Both ground states have a similar Abrikosov lattice structure and…
We discuss how the inclusion of singular gauge fields in the partition function for QCD can lead to a domain-like picture for the QCD vacuum by virtue of specific conditions on quantum fluctuations at the singularities. With a simplified…
We find a new type of topological vortex solution in the $U(1)_Z \times U(1)_A$ Chern Simons gauge theory in the presence of a $U(1)_A$ magnetic field background. In this theory $U(1)_Z$ is broken spontaneously by the $U(1)_A$ magnetic…
The role of the $U(1)_A$ anomaly in QCD phenomenology is reviewed, focusing on the relation between quark dynamics and gluon topology. Topics covered include a generalisation of the Witten-Veneziano formula for the mass of the $\eta'$, the…
It is shown that in the scheme with a rotating fermion mass matrix (i.e. one with a scale-dependent orientation in generation space) suggested earlier for explaining fermion mixing and mass hierarchy, the theta-angle term in the QCD action…
We compute the pressure, chiral condensate and strange quark number susceptibility from first principles within perturbative QCD at finite temperature and very high magnetic fields up to next-to-leading order and physical quark masses. The…
We model the effects of a large number of zero and near-zero modes in the QCD partition function by using sparse chiral matrix models with an emphasis on the quenched topological susceptibility in the choice of the measure. At finite…
The nature of chiral phase transition for QCD with two light quark flavors is not yet completely resolved. This is primarily because one has to understand whether or not the anomalous U(1) symmetry in the flavor sector is effectively…
The existence in the physical QCD vacuum of nonzero gluon condensates, such as $<g^2F^2>$, requires dominance of gluon fields with finite mean action density. This naturally allows any real number value for the unit ``topological charge''…
The distribution of the QCD topological charge can be described by cumulants, with the lowest one being the topological susceptibility. The vacuum energy density in a theta-vacuum is the generating function for these cumulants. In this…