arXiv subjects

R. N. Zhokhov

Publications and source records attributed to R. N. Zhokhov.

31 records · Page 2Linked to original sources

arXiv2019

QCD phase diagram with chiral imbalance in NJL model: duality and lattice QCD results

In addition to temperature and baryon chemical potential there are other parameters that matter in the real quark matter. One of them is isospin asymmetry which does exist in nature, for example, in the compact stars and in heavy ion collisions. The chiral imbalance, the difference between left- and right-handed quarks, is another phenomenon that could occur in quark matter. We have shown that lattice QCD results support the existence of the approximate duality in real QCD. The rise of pseudo-critical temperature with increase of chiral chemical potential $μ_{5}$ (the much debated effect recently, a lot of studies on this contradict each other) has been established in terms of just duality notion, hence reinforce confidence in this result and put it on the considerably more solid ground.

hep-ph↗

arXiv2019

Charged pion condensation and duality in dense and hot chirally and isospin asymmetric quark matter in the framework of NJL$_2$ model

In this paper we investigate in the large-$N_c$ limit ($N_c$ is the number of colored quarks) the phase structure of a massless (1+1)-dimensional quark model with four-quark interaction and in the presence of baryon ($μ_B$), isospin ($μ_I$) and chiral isospin ($μ_{I5}$) chemical potentials as well as at nonzero temperature. It is established that chiral isospin chemical potential leads to the generation of charged pion condensation (PC) in dense (nonzero baryon density) and chiral asymmetric quark matter for a wide range of isospin densities. It is shown that there exists a duality correspondence between the chiral symmetry breaking and the charged PC phenomena at any values of temperature even for very hot quark gluon plasma. Moreover, it is shown that charged PC phase with nonzero baryon density can be induced in the model at comparatively high temperatures. This opens up new possible physical systems, where it can be of importance, such as heavy ion collisions, just born neutron stars (proto-neutron stars), supernovas as well as neutron star mergers.

hep-ph↗

arXiv2019

Dualities and inhomogeneous phases in dense quark matter with chiral and isospin imbalances in framework of effective model

It has been shown in [32,33] in the framework of Nambu--Jona-Lasinio model with the assumption of spatially homogeneous condensates that in the large-$N_{c}$ limit ($N_{c}$ is the number of quark colours) there exist three dual symmetries of the thermodynamic potential, which describes dense quark matter with chiral and isospin imbalances. The main duality is between the chiral symmetry breaking and the charged pion condensation phenomena. There have been a lot of studies and hints that the ground state could be characterized by spatially inhomogeneous condensates, so the question arises if duality is a rather deep property of the phase structure or just accidental property in the homogeneous case. In this paper we have shown that even if the phase diagram contains phases with spatially inhomogeneous condensates, it still possesses the property of this main duality. Two other dual symmetries are not realized in the theory if it is investigated within an inhomogeneous approach to a ground state. From various earlier studied aspects of QCD phase diagram of isospin asymmetric matter with possible inhomogeneous condensates, in the present paper the unified picture and full phase diagram of isospin imbalanced dense quark matter have been assembled. Acting on this diagram by a dual transformation, we obtained, in the framework of an approach with spatially inhomogeneous condensates and without any calculations, a full phase diagram of chirally asymmetric dense medium. This example shows that the duality is not just entertaining mathematical property but an instrument with very high predictivity power. The obtained phase diagram is quite rich and contains various spatially inhomogeneous phases.

hep-ph↗

arXiv2019

Chiral imbalanced hot and dense quark matter: NJL analysis at the physical point and comparison with lattice QCD

Hot and dense quark matter with isospin and chiral imbalances is investigated in the framework of the (3+1)-dimensional Nambu--Jona-Lasinio model (NJL) in the large-$N_c$ limit ($N_c$ is the number of quark colors). Its phase structure is considered in terms of baryon -- $μ_B$, isospin -- $μ_I$ and chiral isospin -- $μ_{I5}$ chemical potentials. It is shown in the paper that (i) in the chiral limit there is a duality between chiral symmetry breaking (CSB) and charged pion condensation (PC) phenomena. (ii) At the physical point, i.e. at nonzero bare quark mass $m_0$, and temperature this duality relation is only approximate, although rather accurate. (iii) We have shown that the chiral isospin chemical potential $μ_{I5}$ in dense quark matter generates charged pion condensation both at zero and nonzero $m_0$, and at $μ_{I5}\ne 0$ this phase might be observed up to temperatures as high as 100 MeV. (iv) Pseudo-critical temperature of the chiral crossover transition rises in the NJL model with increasing $μ_{I5}$. (v) It has been found an agreement between particular sections of the phase diagram in the framework of NJL model and corresponding ones in lattice QCD simulations. Two different plots from different lattice simulations that are completely independent and are not connected at the first sight are in reality dual to each other, it means that lattice QCD simulations support the hypothesis that in real quark matter there exists the (approximate) duality between CSB and charged PC. Moreover, we can reverse the logic and we can predict the increase of pseudo-critical temperature with chiral chemical potential, the much debated effect recently, just by the duality notion, hence bolster confidence in this result (lattice QCD showed this feature for unphysically large pion mass) and put it on the considerably more solid ground.

hep-ph↗

arXiv2019

Dense quark matter with chiral and isospin imbalance: NJL-model consideration

Isospin asymmetry is the well-known property of dense quark matter, which exists in the compact stars and is produced in heavy ion collisions. On the other hand, the chiral imbalance between left- and right-handed quarks is another highly anticipated phenomenon that could occur in the dense quark matter. To investigate quark matter under these conditions, we take into account baryon -- $μ_B$, isospin -- $μ_I$ and chiral isospin -- $μ_{I5}$ chemical potentials and study QCD phase portrait using NJL$_4$ model generalized to two massive quarks that could condense into the pion condensation. We have shown that the chiral isospin chemical potential $μ_{I5}$ generates pion condensation in isospin asymmetric quark matter. Also, we have investigated discrete symmetry (duality) between chiral and pion condensates in the case of massless quarks, which stay relatively instructive even if the quarks have bare mass. To describe hot dense quark matter, in addition to the above-mentioned chemical potentials, we introduce non-zero temperatures into consideration.

hep-ph↗

arXiv2018

Dualities in dense quark matter with isospin, chiral and chiral isospin imbalance in the framework of the large-N$_{c}$ limit of the NJL$_{4}$ model

In this paper the phase structure of the dense quark matter has been investigated in the presence of baryon $μ_B$, isospin $μ_I$, chiral $μ_{5}$ and chiral isospin $μ_{I5}$ chemical potentials in the framework of Nambu--Jona-Lasinio model. It has been shown that in the large-$N_{c}$ limit ($N_{c}$ is the number of quark colours) there exist three duality correspondences in the model. The first duality is between the chiral symmetry breaking and the charged pion condensation phenomena. And there are two new dualities that hold only for chiral symmetry breaking and charged pion condensation phenomena separately. It was shown that at nonzero chiral $μ_{5}$ chemical potential chiral isospin $μ_{I5}$ chemical potential can generate charged pion condensation in dense quark matter even with zero $μ_{I}$. But $μ_{5}$ alone (in absence of $μ_{I5}$ chemical potential) can generate this phase but not as powerfully as $μ_{I5}$ does and only at comparatively low baryon densities.

hep-ph↗

arXiv2018

Dulaity and charged pion condensation in chirally asymmetric dense quark matter in the framework of an NJL$_2$ model

In this talk we present investigation of the phase structure of a (1+1)-dimensional quark model with four-quark interaction and in the presence of baryon ($μ_B$), isospin ($μ_I$) and chiral isospin ($μ_{I5}$) chemical potentials. Spatially homogeneous and inhomogeneous (chiral density wave (for chiral condensate) and single wave (for charged pion condensate)) condensates are considered. It is established that in the large-$N_c$ limit ($N_c$ is the number of colored quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation one. The primary conclusion of this investigation is the fact that chiral isospin chemical potential generates charged pion condensation with non-zero baryon density in dense quark matter. Moreover, it is shown that inhomogeneous charged PC phase with nonzero baryon density is induced in the model by arbitrary small values of the chemical potential $μ_{I5}$ (for a rather large region of $μ_B$ and $μ_I$).

hep-ph↗

arXiv2018

Dense baryon matter with isospin and chiral imbalance in the framework of NJL$_4$ model at large $N_c$: duality between chiral symmetry breaking and charged pion condensation

In this paper the phase structure of dense quark matter has been investigated in the presence of baryon, isospin and chiral isospin chemical potentials in the framework of (3+1)-dimensional Nambu--Jona-Lasinio model with two quark flavors. It has been shown that in the large-$N_{c}$ limit ($N_{c}$ is the number of colors of quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation one. The key conclusion of our studies is the fact that chiral isospin chemical potential generates charged pion condensation in dense quark matter with isotopic asymmetry.

hep-ph↗

arXiv2017

Inhomogeneous charged pion condensation in chiral asymmetric dense quark matter in the framework of NJL$_2$ model

In this paper we investigate the phase structure of a (1+1)-dimensional quark model with four-quark interaction and in the presence of baryon ($μ_B$), isospin ($μ_I$) and chiral isospin ($μ_{I5}$) chemical potentials. Spatially inhomogeneous chiral density wave (for chiral condensate) and single wave (for charged pion condensate) approaches are used. It is established that in the large-$N_c$ limit ($N_c$ is the number of colored quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation (PC) one. Moreover, it is shown that inhomogeneous charged PC phase with nonzero baryon density is induced in the model by arbitrary small values of the chemical potential $μ_{I5}$ (for a rather large region of $μ_B$ and $μ_I$).

hep-ph↗

arXiv2014

Zeeman interaction and chiral symmetry breaking by tilted magnetic field in the (2+1)-dimensional Gross--Neveu model

hep-ph↗

arXiv2013

Magnetic catalysis effect in (2+1)-dimensional Gross--Neveu model with Zeeman interaction

Magnetic catalysis of the chiral symmetry breaking and other magnetic properties of the (2+1)-dimensional Gross--Neveu model are studied taking into account the Zeeman interaction of spin-1/2 quasi-particles (electrons) with tilted (with respect to a system plane) external magnetic field $\vec B=\vec B_\perp+\vec B_\parallel$. The Zeeman interaction is proportional to magnetic moment $μ_B$ of electrons. For simplicity, temperature and chemical potential are equal to zero throughout the paper. We compare in the framework of the model the above mentioned phenomena both at $μ_B=0$ and $μ_B\ne 0$. It is shown that at $μ_B\ne 0$ the magnetic catalysis effect is drastically changed in comparison with the $μ_B= 0$ case. Namely, at $μ_B\ne 0$ the chiral symmetry, being spontaneously broken by $\vec B$ at subcritical coupling constants, is always restored at $|\vec B|\to\infty$ (even at $\vec B_\parallel=0$). Moreover, it is proved in this case that chiral symmetry can be restored simply by tilting $\vec B$ to a system plane, and in the region $ B_\perp\to 0$ the de Haas -- van Alphen oscillations of the magnetization are observed. At supercritical values of coupling constant we have found two chirally non-invariant phases which respond differently on the action of $\vec B$. The first (at rather small values of $|\vec B|$) is a diamagnetic phase, in which there is an enhancement of chiral condensate, whereas the second is a paramagnetic chirally broken phase. Numerical estimates show that phase transitions described in the paper can be achieved at low enough laboratory magnetic fields.

hep-ph↗

arXiv2013

Superconductivity phenomenon induced by external in-plane magnetic field in (2+1)-dimensional Gross--Neveu type model

Phase structure of the (2+1)-dimensional model with four-fermion interaction of spin-1/2 quasiparticles (electrons) both in the fermion-antifermion (or chiral) and fermion-fermion (or superconducting) channels is considered at nonzero chemical potential $μ$ and under the influence of an in-plane, i.e. parallel to a system sheet, external magnetic field $\vec B_\parallel$. It is shown that at sufficiently large values of $μ$ and/or $\vec B_\parallel$ the Cooper pairing (or superconducting) phase appears in the system at arbitrary relation between coupling constants, provided that there is an (arbitrary small) attractive interaction in the superconducting channel. In particular, at sufficiently weak attractive interaction in the chiral channel, the Cooper pairing occurs even at infinitesimal values of $μ$ and/or $\vec B_\parallel$. The superconducting phase of the model is always a paramagnetic one.

hep-th↗

arXiv2012

Superconducting phase transitions induced by chemical potential in (2+1)-dimensional four-fermion quantum field theory

In the paper a generalization of the (1+1)-dimensional model by Chodos et al [Phys. Rev. D61, 045011 (2000)] has been performed to the case of (2+1)-dimensional spacetime. The model includes four-fermion interaction both in the fermion-antifermion (or chiral) and fermion-fermion (or superconducting) channels. We study temperature $T$ and chemical potential $μ$ induced phase transitions in the leading order of large-$N$ expansion technique, where $N$ is a number of fermion fields. It is shown that at sufficiently large values of $μ$ and arbitrary relations between coupling constants, superconducting phase appears in the system both at T=0 and $T>0$. In particular, at T=0 and sufficiently weak attractive interaction in the chiral channel, the Cooper pairing occurs for arbitrary couplings in the superconducting channel even at infinitesimal values of $μ$.

hep-th↗