scholarly journals Many-Body Dynamics and Decoherence of the XXZ Central Spin Model in External Magnetic Field

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 23 ◽  
Author(s):  
Xu Zhou ◽  
Qing-Kun Wan ◽  
Xiao-Hui Wang
Keyword(s):  
Magnetic Field ◽  
Relaxation Process ◽  
Constant Magnetic Field ◽  
Stable State ◽  
Spin Model ◽  
Disorder Strength ◽  
Many Body ◽  
Anisotropic Parameter ◽  
Body Dynamics ◽  
The Magnetic Field

The many-body dynamics of an electron spin−1/2 qubit coupled to a bath of nuclear spins by hyperfine interactions, as described by the central spin model in two kinds of external field, are studied in this paper. In a completely polarized bath, we use the state recurrence method to obtain the exact solution of the X X Z central spin model in a constant magnetic field and numerically analyze the influence of the disorder strength of the magnetic field on fidelity and entanglement entropy. For a constant magnetic field, the fidelity presents non-attenuating oscillations. The anisotropic parameter λ and the magnetic field strength B significantly affect the dynamic behaviour of the central spin. Unlike the periodic oscillation in the constant magnetic field, the decoherence dynamics of the central spin act like a damping oscillation in a disordered field, where the central spin undergoes a relaxation process and eventually reaches a stable state. The relaxation time of this process is affected by the disorder strength and the anisotropic parameter, where a larger anisotropic parameter or disorder strength can speed up the relaxation process. Compared with the constant magnetic field, the disordered field can regulate the decoherence over a large range, independent of the anisotropic parameter.

scholarly journals Velocity-Magnetic Field Correlation of Pulsars

1996 ◽  
Vol 160 ◽  
pp. 49-50
Author(s):  
Naoki Itoh ◽  
Takemi Kotouda
Keyword(s):  
Magnetic Field ◽  
Constant Magnetic Field ◽  
Field Model ◽  
Transverse Velocity ◽  
Distribution Model ◽  
Recent Measurement ◽  
Apparent Correlation ◽  
Magnetic Field Model ◽  
Field Correlation ◽  
The Magnetic Field

Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.

scholarly journals Effect of Alternating Magnetic Field on Arc Plasma Characteristics and Droplet Transfer during Narrow Gap Laser-MIG Hybrid Welding

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1712
Author(s):  
Baihao Cai ◽  
Juan Fu ◽  
Yong Zhao ◽  
Fugang Chen ◽  
Yonghui Qin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Temperature ◽  
High Speed ◽  
Stable State ◽  
Alternating Magnetic Field ◽  
Hybrid Welding ◽  
Arc Plasma ◽  
Narrow Gap ◽  
Droplet Transfer ◽  
The Magnetic Field

In this paper, the morphological characteristics of arc plasma and droplet transfer during the alternating magnetic field-assisted narrow gap groove laser-MIG (metal inert gas) hybrid welding process were investigated. The characteristics of arc plasma and droplet transfer, electron temperature, and density were analyzed using a high-speed camera and spectrum diagnosis. Our results revealed that the arc maintained a relatively stable state and rotated at a high speed to enhance the arc stiffness, and further improved the stability of the arc under the alternating magnetic field. The optimum magnetic field parameters in this experiment were B = 16 mT and f = 20 Hz, the electron temperature was 9893.6 K and the electron density was 0.99 × 1017 cm−3 near the bottom of the groove, which improved the temperature distribution inside the narrow gap groove and eliminated the lack of sidewall fusion defect. Compared to those without a magnetic field, the magnetic field could promote droplet transfer, the droplet diameter decreased by 17.6%, and the transition frequency increased by 23.5% (owing to the centrifugal force during droplet spinning and electromagnetic contraction force). The width of the weld bead was increased by 12.4% and the pores were also significantly reduced due to the stirring of the magnetic field on the molten pool.

scholarly journals Modelling of spacecraft spin period during eclipse

2011 ◽  
Vol 29 (5) ◽  
pp. 875-882 ◽  
Author(s):  
E. Georgescu ◽  
F. Plaschke ◽  
U. Auster ◽  
K.-H. Fornaçon ◽  
H. U. Frey
Keyword(s):  
Magnetic Field ◽  
Heat Dissipation ◽  
Spin Model ◽  
Moment Of Inertia ◽  
Magnetic Field Direction ◽  
Spin Period ◽  
The Earth ◽  
Spacecraft Spin ◽  
The Moment ◽  
The Magnetic Field

Abstract. The majority of scientific satellites investigating the Earth magnetosphere are spin stabilized. The attitude information comes usually from a sun sensor and is missing in the umbra; hence, the accurate experimental determination of vector quantities is not possible during eclipses. The spin period of the spacecraft is generally not constant during these times because the moment of inertia changes due to heat dissipation. The temperature dependence of the moment of inertia for each spacecraft has a specific signature determined by its design and distribution of mass. We developed an "eclipse-spin" model for the spacecraft spin period behaviour using magnetic field vector measurements close to the Earth, where the magnetic field is dominated by the dipole field, and in the magnetospheric lobes, where the magnetic field direction is mostly constant. The modelled spin periods give us extraordinarily good results with accumulated phase deviations over one hour of less than 10 degrees. Using the eclipse spin model satellite experiments depending on correct spin phase information can deliver science data even during eclipses. Two applications for THEMIS B, one in the lobe and the other in the lunar wake, are presented.

DIFFUSION CHARACTERISTIC OF SEVERAL ELEMENTS IN COPPER DURING AN ELECTRIC SPARK PROCESSING UNDER A CONSTANT MAGNETIC FIELD

2009 ◽  
Vol 23 (19) ◽  
pp. 2369-2376 ◽  
Author(s):  
DINA GERTSRIKEN ◽  
VLADIMIR MAZANKO ◽  
SHENGRU QIAO ◽  
CHENGYU ZHANG
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Constant Magnetic Field ◽  
Energy Gap ◽  
Pyrolytic Graphite ◽  
X Ray ◽  
Lattice Constants ◽  
The Matrix ◽  
Mechanical Mixtures ◽  
The Magnetic Field

The surface of Cu cathode was alloyed by several elements, including pure Ni , Fe , Ag and pyrolytic graphite, during electric spark processing technology (ESP). The energy, gap between the electrode and matrix, and the total fabricating time of ESP are 0.9 J, 0.5 mm, and 30 s, respectively. The ESP was performed under a constant magnetic field (CMF) of 630 kA/m. The atom distribution profiles along the depth were measured by a serial sectioning and autoradiography. The lattice constants were studied by an X-ray diffractometer. The results show that there is one or several concentration peaks in the subsurface of Cu . When the depth is beyond the location corresponding to the concentration peaks, the concentration distribution in the matrix can be described by an exponential function. Fe and C atoms can homogeneously diffuse into the Cu lattice, accompanied by mechanical mixtures, and no traces of diffusion along the grain boundaries can be found. Comparing with the condition without a CMF, the diffusion coefficient decreases when the magnetic field is parallel to the surface, whereas the diffusion coefficient is the smallest when the magnetic field is perpendicular to the surface. The lattice constant of Cu becomes smaller after the ESP.

scholarly journals ENERGY SPECTRUM OF THE GROUND STATE OF A TWO-DIMENSIONAL RELATIVISTIC HYDROGEN ATOM IN THE PRESENCE OF A CONSTANT MAGNETIC FIELD

2003 ◽  
Vol 17 (25) ◽  
pp. 1331-1341 ◽  
Author(s):  
VÍCTOR M. VILLALBA ◽  
RAMIRO PINO
Keyword(s):  
Magnetic Field ◽  
Energy Spectrum ◽  
Ground State ◽  
Constant Magnetic Field ◽  
Two Dimensional ◽  
Relativistic Limit ◽  
Dirac Electron ◽  
Relativistic Hydrogen ◽  
Relativistic Hydrogen Atom ◽  
The Magnetic Field

We compute the energy spectrum of the ground state of a 2D Dirac electron in the presence of a Coulomb potential and a constant magnetic field perpendicular to the plane where the the electron is confined. With the help of a mixed-basis variational method we compute the wave function and the energy level and show how it depends on the magnetic field strength. We compare the results with those obtained numerically as well as in the non-relativistic limit.

scholarly journals EFFECT OF STRONG MAGNETIC FIELDS ON THE EQUILIBRIUM OF A DEGENERATE GAS OF NUCLEONS AND ELECTRONS

1996 ◽  
Vol 10 (23) ◽  
pp. 1141-1149 ◽  
Author(s):  
CHOON-LIN HO ◽  
V.R. KHALILOV ◽  
CHI YANG
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Strong Magnetic Field ◽  
Constant Magnetic Field ◽  
Fermi Momentum ◽  
Magnetic Field Induction ◽  
Strong Magnetic Fields ◽  
Field Induction ◽  
The Magnetic Field

We obtain the equations that define the equilibrium of a homogeneous relativistic gas of neutrons, protons and electrons in a constant magnetic field as applied to the conditions that probably occur near the center of neutron stars. We compute the relative densities of the particles at equilibrium and the Fermi momentum of electrons in the strong magnetic field as function of the density of neutrons and the magnetic field induction. Novel features are revealed as to the ratio of the number of protons to the number of neutrons at equilibrium in the presence of large magnetic fields.

Radiationless Internal Vibration sof Extended Charged Particles in a Constant Magnetic Field

1977 ◽  
Vol 32 (9) ◽  
pp. 903-913
Author(s):  
W. Heudorfer ◽  
M. Sorg
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Constant Magnetic Field ◽  
Constant Velocity ◽  
Charged Particles ◽  
Internal Vibration ◽  
Particle Theory ◽  
Free Case ◽  
The Magnetic Field

The extended particle theory recently proposed is further investigated. Especially, it is shown for the force-free case that no runaway solutions exist and that the particle must ultimately assume constant velocity. For a certain structure of the particle, internal radiationless vibrations are found and discussed extensively for the case, where the particle moves in a constant homogenious magnetic field. If the magnetic field strength assumes a certain discrete set of values, the motion terminates in that radiationless internal rotation; in all other cases the particle spirals inwards under emission of radiation until it comes to rest.

scholarly journals Effects of Constant Magnetic Field to the Proliferation Rate of Human Fibroblasts Grown onto Different Substrates: Tissue Culture Polystyrene, Polyacrylamide Hydrogel and Ferrogels γ-Fe2O3 Magnetic Nanoparticles

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1697 ◽  
Author(s):  
Felix A. Blyakhman ◽  
Grigory Yu. Melnikov ◽  
Emilia B. Makarova ◽  
Fedor A. Fadeyev ◽  
Daiana V. Sedneva-Lugovets ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cell Proliferation ◽  
Tissue Culture ◽  
Magnetic Nanoparticles ◽  
Regenerative Medicine ◽  
Constant Magnetic Field ◽  
Dermal Fibroblasts ◽  
Proliferation Rate ◽  
Tissue Culture Polystyrene ◽  
The Magnetic Field

The static magnetic field was shown to affect the proliferation, adhesion and differentiation of various types of cells, making it a helpful tool for regenerative medicine, though the mechanism of its impact on cells is not completely understood. In this work, we have designed and tested a magnetic system consisting of an equidistant set of the similar commercial permanent magnets (6 × 4 assay) in order to get insight on the potential of its experimental usage in the biological studies with cells culturing in a magnetic field. Human dermal fibroblasts, which are widely applied in regenerative medicine, were used for the comparative study of their proliferation rate on tissue culture polystyrene (TCPS) and on the polyacrylamide ferrogels with 0.00, 0.63 and 1.19 wt % concentrations of γ-Fe2O3 magnetic nanoparticles obtained by the well-established technique of laser target evaporation. We used either the same batch as in previously performed but different biological experiments or the same fabrication conditions for fabrication of the nanoparticles. This adds special value to the understanding of the mechanisms of nanoparticles contributions to the processes occurring in the living systems in their presence. The magnetic field increased human dermal fibroblast cell proliferation rate on TCPS, but, at the same time, it suppressed the growth of fibroblasts on blank gel and on polyacrylamide ferrogels. However, the proliferation rate of cells on ferrogels positively correlated with the concentration of nanoparticles. Such a dependence was observed both for cell proliferation without the application of the magnetic field and under the exposure to the constant magnetic field.

Effects of High Magnetic Field and Tensile Stress on Martensitic Transformation Behavior and Microstructure At 4 K in Fe-Ni-C Alloys

1995 ◽  
Vol 398 ◽  
Author(s):  
H. Ohtsuka ◽  
K. Nagai ◽  
S. Kajiwara ◽  
H. Kitaguchi ◽  
M. Uehara
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
Tensile Stress ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
High Magnetic Field ◽  
Constant Magnetic Field ◽  
Critical Magnetic Field ◽  
Transformation Behavior ◽  
The Magnetic Field

ABSTRACTEffects of high magnetic field and tensile stress on martensitic transformation behavior and microstructure at 4 K have been studied in Fe-31Ni-0.4C and Fe-27Ni-0.8C shape memory alloys. It was found that the critical magnetic field to induce martensitic transformation is between 7.5 T and 10 T. In the case of Fe-27Ni-0.8C, martensitic transformation is stress-induced at lower level of stress in magnetic field than in the case when no magnetic Field is applied. The amount of martensite formed by increasing the magnetic field under constant stress is larger than that formed by increasing the stress in the constant magnetic field.

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