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FINITE TEMPERATURE EFFECTS ON SPIN POLARIZATION OF NEUTRON MATTER IN A STRONG MAGNETIC FIELD
Isayev, Alexander A.,Yang, Jong-Mann The Korean Astronomical Society 2010 Journal of The Korean Astronomical Society Vol.43 No.5
Magnetars are neutron stars possessing a magnetic field of about $10^{14}-10^{15}$ G at the surface. Thermodynamic properties of neutron star matter, approximated by pure neutron matter, are considered at finite temperature in strong magnetic fields up to $10^{18}$ G which could be relevant for the inner regions of magnetars. In the model with the Skyrme effective interaction, it is shown that a thermodynamically stable branch of solutions for the spin polarization parameter corresponds to the case when the majority of neutron spins are oriented opposite to the direction of the magnetic field (i.e. negative spin polarization). Moreover, starting from some threshold density, the self-consistent equations have also two other branches of solutions, corresponding to positive spin polarization. The influence of finite temperatures on spin polarization remains moderate in the Skyrme model up to temperatures relevant for protoneutron stars. In particular, the scenario with the metastable state characterized by positive spin polarization, considered at zero temperature in Phys. Rev. C 80, 065801 (2009), is preserved at finite temperatures as well. It is shown that, above certain density, the entropy for various branches of spin polarization in neutron matter with the Skyrme interaction in a strong magnetic field shows the unusual behavior, being larger than that of the nonpolarized state. By providing the corresponding low-temperature analysis, we prove that this unexpected behavior should be related to the dependence of the entropy of a spin polarized state on the effective masses of neutrons with spin up and spin down, and to a certain constraint on them which is violated in the respective density range.
Anisotropic pressure in dense neutron matter under the presence of a strong magnetic field
Isayev, A.A.,Yang, J. North-Holland Pub. Co 2012 Physics letters: B Vol.707 No.1
Dense neutron matter with recently developed BSk19 and BSk21 Skyrme effective forces is considered in magnetic fields up to 10<SUP>20</SUP> G at zero temperature. The breaking of the rotational symmetry by the magnetic field leads to the differentiation between the pressures along and perpendicular to the field direction which becomes significant in the fields H>H<SUB>th</SUB>~10<SUP>18</SUP> G. The longitudinal pressure vanishes in the critical field 10<SUP>18</SUP><H<SUB>c</SUB>@?10<SUP>19</SUP> G, resulting in the longitudinal instability of neutron matter. For the Skyrme force fitted to the stiffer underlying equation of state (BSk21 vs. BSk19) the threshold H<SUB>th</SUB> and critical H<SUB>c</SUB> magnetic fields become larger. The longitudinal and transverse pressures as well as the anisotropic equation of state of neutron matter are determined under the conditions relevant for the cores of magnetars.
Upper Bound On the Magnetic Field Strength in the Quark Core of a Strongly-magnetized Compact Star
Alexander Isayev,양종만 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.6
Two types of strongly-magnetized compact stars, represented by magnetized strange quark starsand magnetized hybrid stars, are considered. In each case, there exists an upper bound Hmax onthe magnetic field strength in the interior of a compact star. For a magnetized strange quark star,Hmax is determined by the magnetic field at which the upper bound on the bag pressure fromthe absolute stability window of magnetized strange quark matter (SQM) vanishes, assuming theMassachusetts Institute of Technology bag model description of SQM. For a hybrid star, Hmax isrepresented by the critical magnetic field for the occurrence of a longitudinal (along the magneticfield) instability in the quark core, at which the longitudinal pressure in magnetized SQM vanishes.
Ultrasonic-aided Extrusion Process for Recycling of Rubbers and Copolymerization of Polymer Blends
( A. I. Isayev ) 한국고무학회 2003 엘라스토머 및 콤포지트 Vol.38 No.1
N/A This paper describes recent advances in ultrasonic devulcanization technology and the in · Situ ultrasonic compatibilization of the blends of the immiscible polymers by making copolymers at the interfaus and their vicinities and our understanding of the mechanism of these processes.
Lee, Ho-Sang,Isayev, A.I. Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.1
A computer code was developed to simulate the filling stage of an injection/compression molding process using a finite element method. The constitutive equation was the compressible Leonov model and the PVT relationship was assumed to follow the Tait equation. The flow-induced birefringence was related to the calculated flow stresses through the linear stress-optical law. Simulations of a disk under different processing conditions, including variations of the compression stroke and compression speed, were performed to determine their effects on the flow-induced birefringence. Simulated pressure traces were also compared to those obtained in conventional injection molding and with experimental data from the literature.
두께가 급격히 변하는 영역에서 고분자 유동에 의한 복굴절
이호상(H. S. Lee),A. I. Isayev 한국소성·가공학회 2009 소성가공 : 한국소성가공학회지 Vol.18 No.1
A finite element analysis was carried out for a 4:1 planar contraction die for polymer melts using the viscoelastic constitutive equation of Leonov. Viscoelastic fluids showed significant differences in pressure drop and birefringence in contraction and expansion flows. The pressure drop was higher and the birefringence smaller in expansion than in contraction flow. The difference increased with increasing flow rate. The nonlinear Leonov model was shown to describe the viscoelastic effects observed in experiments.