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M. N. Chernodub

Publications and source records attributed to M. N. Chernodub.

At least 109 records · Page 6Linked to original sources
arXiv2009

Chiral magnetization of non-Abelian vacuum: a lattice study

The chiral magnetization properties of cold and hot vacua are studied using quenched simulations in lattice Yang-Mills theory. In weak external magnetic fields the magnetization is proportional to the first power of the magnetic field. We evaluate numerically the coefficient of the proportionality (the chiral susceptibility) using near-zero eigenmodes of overlap fermions. We found that the product of the chiral susceptibility and the chiral condensate equals to 46(3) MeV. This value is very close to the phenomenological value of 50 MeV. In strong fields the magnetization is a nonlinear function of the applied magnetic field. We find that the nonlinear features of the magnetization are well described by an inverse tangent function. The magnetization is weakly sensitive to temperature in the confinement phase.

hep-lat↗
arXiv2009

Thermal monopoles and selfdual dyons in the Quark-Gluon Plasma

We perform a numerical study of the excess of non-abelian gauge invariant gluonic action around thermal abelian monopoles which populate the deconfined phase of Yang-Mills theories. Our results show that the excess of magnetic action is close to that of the electric one, so that thermal abelian monopoles may be associated with physical objects carrying both electric and magnetic charge, i.e. dyons. Thus, the quark gluon plasma is likely to be populated by selfdual dyons, which may manifest themselves in the heavy-ion collisions via the chiral magnetic effect. Thermodynamically, thermal monopoles provide a negative contribution to the pressure of the system.

hep-ph↗
arXiv2009

Lattice QCD in strong magnetic fields

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 recent results demonstrating that very strong external magnetic fields lead to (1) the enhancement of the chiral symmetry breaking [the quark condensate rises with the increase of the external magnetic field]; (2) the chiral magnetization of the QCD vacuum [spins of the quarks turn parallel to the external field]; (3) the chiral magnetic effect [a CP-odd generation of the electric current of quarks directed along the magnetic field]; (4) a CP-odd generation of the anomalous quark electric dipole moment along the axis of magnetic field. The first three effects were already predicted theoretically, and subsequently observed numerically in our simulations, while the fourth effect is a new result.

hep-ph↗
arXiv2009

Electric-magnetic asymmetry of the A^2 condensate and the phases of Yang-Mills theory

We study the finite-temperature behavior of the A^2 condensate in the Landau gauge of SU(2) Yang--Mills theory on the lattice in a wide range of temperatures. The asymmetry between the electric (temporal) and magnetic (spatial) components of this unconventional dimension-2 condensate is a convenient ultraviolet-finite quantity which possesses, as we demonstrate, unexpected properties. The low-temperature behavior of the condensate asymmetry suggests that the mass of the lowest thermal excitation in the condensate is unexpectedly low, about 200 MeV, which is much smaller than the glueball mass. The asymmetry is peaking at the phase transition, becoming a monotonically decreasing function in the deconfinement phase. A symmetric point is reached in the deconfinement phase at a temperature approximately equal twice the critical temperature. The behavior of the electric-magnetic asymmetry of the condensate separates the phase diagram of Yang-Mills theory into three regions. We suggest that these regions are associated with the condensed, liquid and gaseous states of the confining gluonic objects, the Abelian monopoles.

hep-lat↗
arXiv2009

Manifestations of magnetic vortices in equation of state of Yang-Mills plasma

The vacuum of Yang-Mills theory contains singular stringlike objects identified with center (magnetic) vortices. Percolation of magnetic vortices is known to be responsible for the color confinement in the low-temperature phase of the theory. In our work we study properties of the vortices at finite temperature using lattice simulations of SU(2) gauge theory. We show that magnetic vortices provide a numerically large contribution to thermodynamic quantities of the gluon plasma in Yang-Mills theory. In particular, we observe that in the deconfinement phase at temperatures T_c < T < 3 T_c the magnetic component of the gluon plasma produces a negative (ghostlike) contribution to the anomaly of the energy-momentum tensor. In the confinement phase the vortex contribution is positive. The thermodynamical significance of the magnetic objects allows us to suggest that the quark-gluon plasma may contain a developed network of magnetic flux tubes. The existence of the vortex network may lead to observable effects in the quark-gluon plasma because the chromomagnetic field of the vortices should scatter and drag quarks.

hep-lat↗
arXiv2009

Numerical evidence of chiral magnetic effect in lattice gauge theory

The chiral magnetic effect is the generation of electric current of quarks along external magnetic field in the background of topologically nontrivial gluon fields. There is a recent evidence that this effect is observed by the STAR Collaboration in heavy ion collisions at RHIC. In our paper we study qualitative signatures of the chiral magnetic effect using quenched lattice simulations. We find indications that the electric current is indeed enhanced in the direction of the magnetic field both in equilibrium configurations of the quantum gluon fields and in a smooth gluon background with nonzero topological charge. In the confinement phase the magnetic field enhances the local fluctuations of both the electric charge and chiral charge densities. In the deconfinement phase the effects of the magnetic field become smaller, possibly due to thermal screening. Using a simple model of a fireball we obtain a good agreement between our data and experimental results of the STAR Collaboration.

hep-lat↗
arXiv2009

Magnetic component of gluon plasma and its viscosity

We discuss the role of the magnetic degrees of freedom of the gluon plasma in its viscosity. The main assumption is that motions of the magnetic component and of the rest of the plasma can be considered as independent. The magnetic component in the deconfined phase is described by a three-dimensional (Euclidean) field theory. The parameters of the theory can be estimated phenomenologically, from the lattice data. It is not ruled out that the magnetic component is superfluid.

hep-ph↗
arXiv2009

Baryon number violation and a new electroweak interaction

We introduce a new supercurrent in the electroweak sector of the standard model. Its interaction with the hypergauge field influences the mass of the Z boson but has no effect on the W^\pm-boson masses. In the leptonic sector it affects the numerical value of the vector and axial coupling constants between neutral currents and the Z boson, and a comparison with experimental values yields an upper bound to the strength of the coupling between the supercurrent and the hypergauge field. In the baryonic sector the supercurrent gives a new contribution to the anomaly equation for baryon number current. As a consequence it may have an effect on baryogenesis.

hep-ph↗
arXiv2009

Deconfinement phase transition in mirror of symmetries

We summarize and extend evidence that the deconfinement phase transition in Yang-Mills theories can be viewed as change of effective non-perturbative degrees of freedom and of symmetries of their interactions. In short, the strings in four dimensions (4d) at temperatures below the critical temperature Tc are replaced by particles, or field theories in 3d at T>Tc. The picture emerges within various approaches based, in particular, on dual models, lattice data and field theoretic models. We concentrate mostly on the lattice data, or on the language of quantum geometry.

hep-ph↗
arXiv2008

Abelian monopoles and center vortices in Yang-Mills plasma

Condensation of the Abelian monopoles and the center vortices leads to confinement of color in low temperature phase of Yang-Mills theory. We stress that these topological magnetic degrees of freedom are also very important in the deconfinement regime: at the point of the deconfinement phase transition both the monopoles and the vortices are released into the thermal vacuum contributing, in particular, to the equation of state and, definitely, to transport properties of the hot gluonic medium. Thus, we argue that a novel, magnetic component plays a crucial role. On the other hand, it was demonstrated that an effective three-dimensional description can be brought, beginning with high temperatures, down to the critical temperature by postulating existence of a system of 3d Higgs fields. We propose to identify the 3d color-singlet Higgs field with the 3d projection of the 4d magnetic vortices. Such identification fits well the 3d properties of the theory and contributes to interpretation of the magnetic component of the Yang-Mills plasma.

hep-ph↗
arXiv2008

Non-Abelian Supercurrents and de Sitter Ground State in Electroweak Theory

We show that gauge symmetry breaking in the Weinberg-Salam model can be implemented by a mere change of variables and without any explicit gauge fixing. The change of variables entails the concept of supercurrent which has been widely employed in the study of superconductivity. It also introduces a separation between the isospin and the hypercharge, suggesting that our new variables describe a strongly coupled regime of the electroweak theory. We discuss the description of various embedded topological defects in terms of these variables. We also propose that in terms of our variables the Weinberg-Salam model can be interpreted in terms of a gravity theory with the modulus of Higgs field as dilaton and the de Sitter space as the ground state.

hep-th↗
arXiv2008

Embedding Brans-Dicke gravity into electroweak theory

We argue that a version of the four dimensional Brans-Dicke theory can be embedded in the standard flat spacetime electroweak theory. The embedding involves a change of variables that separates the isospin from the hypercharge in the electroweak theory.

hep-ph↗
arXiv2008

Monopoles and vortices in Yang-Mills plasma

We discuss the role of magnetic degrees of freedom in Yang-Mills plasma at temperatures above and of order of the critical temperature Tc. While at zero temperature the magnetic degrees of freedom are condensed and electric degrees of freedom are confined, at the point of the phase transition both magnetic and electric degrees of freedom are released into the thermal vacuum. This phenomenon might explain the observed unusual properties of the plasma.

hep-ph↗
arXiv2008

Combining infrared and low-temperature asymptotes in Yang-Mills theories

We demonstrate that power-like non-perturbative behavior of gluon and ghost propagators in infrared limit of Yang-Mills theories can provide at finite temperatures T a negative T^4-contribution to the pressure and energy density. Existence of mass gap implies then new relations between infrared critical exponents of gluon and ghost propagators.

hep-ph↗
arXiv2008

Monopoles from quark condensates in QCD

Chiral monopoles are hedgehoglike structures in local chiral condensates in QCD. These monopoles are (i) made of quark and gluon fields; (ii) explicitly gauge-invariant; and (iii) they carry quantized and conserved chromomagnetic charge. We argue that the chiral condensate vanishes in a core of the chiral monopole while the density of these monopoles increases with temperature wiping out the quark condensate in quark-gluon plasma. We suggest that the dynamics of the chiral monopoles is responsible for the chiral symmetry restoration in high temperature phase of QCD. We also argue that the chiral monopoles are unlikely to be associated with confining degrees of freedom. In our approach the chiral symmetry restoration and the color deconfinement in QCD are not necessarily related to each other and the corresponding transitions may occur at different temperatures.

hep-ph↗
arXiv2007

Topological defects and equation of state of gluon plasma

We show that the degrees of freedom associated with magnetic monopole- and vortexlike gluonic configurations make a strong contribution to the anomaly of the energy-momentum tensor of Yang-Mills theory in the deconfinement phase immediately above the critical temperature. As is well known in zero-temperature Yang-Mills theory, the monopoles and vortices are constituents of a generic gluonic object in which the two neighbor monopoles are connected together by a segment of vortex string. Our results provide evidence that the monopole-vortex chains in SU(2) gauge theory and their SU(3) counterparts, the monopole-vortex nets, are thermodynamically relevant degrees of freedom in the gluonic plasma.

hep-lat↗
arXiv2007

Confining string and its widening in HP1 embedding approach

Structure of confining string in terms of the topological charge density and the action density is studied in SU(2) Yang-Mills theory on the lattice using HP1 sigma-model embedding approach. We find that the confining flux tube noticeably suppresses both the topological charge and the action densities. Beyond the string formation length the string cross section in terms of these quantities is well described by a Gaussian profile. In both cases the squared string width is found to be a logarithmic function of the string length confirming the Luscher widening of the chromoelectric string. Characteristic string scales in terms of the topological and action densities are estimated as well.

hep-lat↗