Topological charge changing transitions can induce chirality in the quark-gluon plasma by the axial anomaly. We study the equilibrium response of the quark-gluon plasma in such a situation to an external magnetic field. To mimic the effect of the topological charge changing transitions we will introduce a chiral chemical potential. We will show that an electromagnetic current is generated along the magnetic field. This is the Chiral Magnetic Effect. We compute the magnitude of this current as a function of magnetic field, chirality, temperature, and baryon chemical potential.

Quantum chromodynamics (QCD) contains field configurations which can be characterized by a topological invariant, the winding number Q w . Configurations with nonzero Q w break the charge-parity (CP) symmetry of QCD. We consider a novel mechanism by which these configurations can separate charge in the presence of a background magnetic field -the "Chiral Magnetic Effect". We argue that sufficiently large magnetic fields are created in heavy ion collisions so that the Chiral Magnetic Effect causes preferential emission of charged particles along the direction of angular momentum. Since separation of charge is CP-odd, any observation of the Chiral Magnetic Effect could provide a clear demonstration of the topological nature of the QCD vacuum. We give an estimate of the effect and conclude that it might be observed experimentally.

Gluon field configurations with nonzero topological charge generate chirality, inducing P-and CPodd effects. When a magnetic field is applied to a system with nonzero chirality, an electromagnetic current is generated along the direction of the magnetic field. The induced current is equal to the Chiral Magnetic conductivity times the magnetic field. In this article we will compute the Chiral Magnetic conductivity of a high-temperature plasma for nonzero frequencies. This allows us to discuss the effects of time-dependent magnetic fields, such as produced in heavy ion collisions, on chirally asymmetric systems.

The chiral magnetic effect is the generation of electric current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly 1,2 in relativistic field theory of chiral fermions (massless spin 1/2 particles with a definite projection of spin on momentum) -a dramatic phenomenon arising from a collective motion of particles and antiparticles in the Dirac sea. The recent discovery 3-5 of Dirac semimetals with chiral quasi-particles opens a fascinating possibility to study this phenomenon in condensed matter experiments. Here we report on the first observation of chiral magnetic effect through the measurement of magneto-transport in zirconium pentatelluride, ZrTe 5 . Our angle-resolved photoemission spectroscopy experiments show that this material's electronic structure is consistent with a 3D Dirac semimetal. We observe a large negative magnetoresistance when magnetic field is parallel with the current. The measured quadratic field dependence of the magnetoconductance is a clear indication of the chiral magnetic effect. The observed phenomenon stems from the effective transmutation of Dirac semimetal into a Weyl semimetal induced by the parallel electric and magnetic fields that represent a topologically nontrivial gauge field background. PACS numbers:1 arXiv:1412.6543v1 [cond-mat.str-el]

We analyze the first results on charged particle multiplicity at RHIC in the conventional eikonal approach and in the framework of high density QCD. We extract the fraction F of the hadron multiplicity originating from "hard" (i.e. proportional to the number of binary collisions) processes; we find a strong growth of this fraction with energy:This indicates a rapid increase in the density of the produced particles. We outline the predictions of high density QCD for the centrality, energy, and atomic number dependence of hadron production. Surprisingly, the predictions of the conventional eikonal approach and of high density QCD for centrality dependence of hadron multiplicity at √ s = 130 GeV appear very similar.

We consider propagation of heavy quarks in QCD matter. Because of large quark mass, the radiative quark energy loss appears to be qualitatively different from that of light quarks at all energies of practical importance. Finite quark mass effects lead to an in-medium enhancement of the heavy-to-light D/π ratio at moderately large (5-10 GeV) transverse momenta. For hot QCD matter a large enhancement is expected, whose magnitude and shape are exponentially sensitive to the density of colour charges in the medium.

We review the predictions of the theory of a color glass condensate for a gluon production cross section in p(d)A collisions. We demonstrate that, at moderate energies, when the gluon production cross section can be calculated in the framework of the McLerran-Venugopalan model, it has only a partonic level Cronin effect in it. At higher energies or rapidities corresponding to smaller values of the Bjorken x, quantum evolution becomes important. The effect of quantum evolution at higher energies or rapidities is to introduce the suppression of high-p T gluons slightly decreasing the Cronin enhancement. At still higher energies or rapidities quantum evolution leads to the suppression of produced gluons at all values of p T .

The arguments for the possibility of violation of P and CP symmetries of strong interactions at finite temperature are presented. A new way of observing these effects in heavy ion collisions is proposed -it is shown that parity violation should manifest itself in the asymmetry between positive and negative pions with respect to the reaction plane. Basing on topological considerations, we derive a lower bound on the magnitude of the expected asymmetry, which may appear within the reach of the current and/or future heavy ion experiments.The strong CP problem remains one of the most outstanding puzzles of the Standard Model. Even though several possible solutions have been put forward (for example, the axion scenario [1]), at present it is still not clear why P and CP invariances are respected by strong interactions.A few years ago, it was proposed that in the vicinity of the deconfinement phase transition QCD vacuum can possess metastable domains leading to P and CP violation [2]. It was also suggested that this phenomenon would manifest itself in specific correlations of pion momenta [2,3]. Such "P-odd bubbles" are a particular realization of an excited vacuum domain which may be produced in heavy ion collisions [4], and several other realizations have been proposed before [5,6]. (For related studies of metastable vacuum states, especially in supersymmetric theories, see [7,8,9]). However the peculiar pattern of P and CP breaking possessed by P-odd bubbles may make them amenable to observation, as we will discuss in this letter.The existence of metastable P-odd bubbles does not contradict the Vafa-Witten theorem [10] stating that P and CP cannot be broken in the true ground state of QCD for θ = 0. Moreover, this theorem does not apply to QCD matter at finite isospin density [11] and finite temperature [12], where Lorentz-non-invariant Podd operators are allowed to have non-zero expectation values. Degenerate vacuum states with opposite parity were found [13] in the superconducting phase of QCD. Parity broken phase also exists in lattice QCD with Wilson fermions [14], but this phenomenon has been recognized as a lattice artifact for the case of mass-degenerate quarks; spontaneous P and CP breaking similar to the Dashen's phenomenon [15] can however occur for nonphysical values of quark masses [16]. P-even, but Codd metastable states have also been argued to exist in hot gauge theories [17]. The conditions for the applicability of Vafa-Witten theorem have been repeatedly reexamined in recent years [18].Several dynamical scenarios for the decay of P-odd bubbles have been considered [19], and a numerical lattice calculation of the fluctuations of topological charge in classical Yang-Mills fields has been performed [20]. The studies of P-and CP-odd correlations of pion momenta [21,22], including those proposed in ref [23], have shown that such measurements are in principle feasible but would require large event samples. In addition, the magnitude of the expected effect despite the estimates done using the chiral Lagran...