共查询到20条相似文献,搜索用时 31 毫秒
1.
Serge Galam 《Physics letters. A》1984,100(2):105-107
A new mean field approach for antiferromagnets in a field is shown to be equivalent to a mean field treatment of ferromagnets in a random field. Phase diagrams of the two systems are analogous. 相似文献
2.
Amos Harpaz 《Foundations of Physics》2007,37(4-5):763-772
The potential of a static electric charge located in a Schwarzschild gravitational field is given by Linet. The expressions
for the field lines derived from this potential are calculated by numerical integration and drawn for different locations
of the static charge in the gravitational field. The field lines calculated for a charge located very close to the central
mass can be compared to those calculated by Hanni–Ruffini. Maxwell equations are used to analyze the dynamics of the falling
electric field in a gravitational field. 相似文献
3.
The balance equations are used to investigate the hot electron magneto-transport in narrowgap semiconductor InSb at 77 K in crossed weak magnetic field and electric field. In the case of vanishing transverse velocity, the drift mobility and the Hall mobility are calculated and it is shown that the Hall factor in InSb at 77K is less than 1 and decreases with electric field. In the case of vanishing transverse electric field, the longitudinal velocity and the transverse velocity are calculated as a function of the magnetic field and the electric field. The effect of the magnetic field on the longitudinal velocity is different from that on the transverse velocity. 相似文献
4.
X.L. Lei S.Y. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):271-277
We investigate the magnetotransport in semiconductors under the influence of a dc or slowly-varying electric field, an intense
polarized radiation field of terahertz frequency, and a uniform magnetic field, being in arbitrary directions and having arbitrary
strengths. Effective force- and energy-balance equations are derived by using a gauge that the magnetic field and the high-frequency
radiation field are described by a vector potential and the dc or slowly-varying field by a scalar potential, and by distinguishing
the slowly-varying velocity from the rapidly-oscillating velocity related to the high-frequency field. These equations, which
include the elastic photon process and all orders of multiphoton absorption and emission processes, are applied to the examination
of the effect of a terahertz radiation on the magnetophonon resonance of the longitudinal resistivity in the transverse configuration
in nonpolar and polar semiconductors. We find that the previous zero-photon resonance peaks are suppressed by the irradiation
of the terahertz field, while many new peaks, which may be related to multiphoton absorption and emission processes, emerge
and can become quite distinct, at moderately strong radiation field.
Received 17 May 1999 相似文献
5.
Magnetization reversal processes by a switching field in single-domain nano-sized magnetic particles in the presence of a small transverse non-static bias field are studied. Applying an oscillating bias field instead of a static field, the reversal time becomes much shorter when the switching field is slightly stronger than the effective anisotropy field. A pulsed bias field of a suitably chosen duration in the nanosecond scale is found to induce a rapid switching, even when the switching field is smaller than the anisotropy field. The dependence of the reversal time on the frequency of an oscillating bias field and the duration of a pulsed bias field are studied. The present work thus complement the earlier studies on switching in the presence of a static bias field. 相似文献
6.
O. B. Prepelitsa 《Journal of Experimental and Theoretical Physics》1997,85(5):838-845
Quantum-electrodynamic processes that take place in the presence of a squeezed electromagnetic field are discussed. Integral
formulas are derived that make it possible to express the probability of any process in a squeezed electromagnetic field in
terms of the probability of the same process in a classical electromagnetic field. The main laws that govern processes of
first order in the fine-structure constant as functions of the number of photons involved and the quantum fluctuations are
examined. Tunneling formulas for the probability of a photon producing an electron-positron pair in a strong squeezed field
are derived. Also, resonant electron-electron scattering is examined and the scattering cross section as a function of the
statistical properties of the field (the way the field has been squeezed) is investigated. It is found that the quantum fluctuations
of the squeezed electromagnetic field give rise to an increase in the scattering cross section, with the probability of the
process in a phase-squeezed electromagnetic field always being higher than the probability of the process in an amplitude-squeezed
electromagnetic field.
Zh. éksp. Teor. Fiz. 112, 1543–1556 (November 1997) 相似文献
7.
在假设声场不受电磁场影响的前提下,将Pride声电耦合方程组化为具有电流源的麦克斯韦方程组.与空间位置固定的电流源产生的电磁场不同,孔隙地层中声波诱导的电磁场是由空间波动的电流源产生的.通过引入赫兹矢量,将求解麦克斯韦方程组问题转化为求解关于赫兹矢量的非齐次矢量赫姆霍兹方程组.通过求解该方程组,得出电磁场表达式.利用此方法,针对声电效应测井,分别计算了由单极声源、偶极声源、四极声源激发的井内声场及其诱导电磁场的全波波形.
关键词:
孔隙介质
诱导电磁场
测井
多极声源 相似文献
8.
This paper extends a previous one which was applicable only to short range interactions. We study the relativistic field theory of a charged spin-zero boson field in the presence of the Coulomb field of a prescribed (nuclear) charge distribution. It is shown that for a sufficiently intense field the ground state is unstable against the formation of a Bose-Einstein condensate of negatively charged bosons, positively charged bosons escaping the system. When the effects of weak interaction are included, the instability occurs in a weaker field and positrons are emitted. A consistent quantum theory is formulated after the Coulomb interaction of the bosons is included. Properties of the condensate are examined in the limit of large condensate density, in a mean field approximation, which is also studied numerically. Possible implications concerning the existence of abnormally bound nuclei are presented. 相似文献
9.
《Fortschritte der Physik》2017,65(12)
Covariance is a useful property for handling supergravity theories. In this paper, we prove a covariance property of supergravity field equations: under reasonable conditions, field equations of supergravity are covariant modulo other field equations. We prove that for any supergravity there exist such covariant equations of motion, other than the regular equations of motion, that are equivalent to the latter. The relations that we find between field equations and their covariant form can be used to obtain multiplets of field equations. In practice, the covariant field equations are easily found by simply covariantizing the ordinary field equations. 相似文献
10.
The intrinsic angular-dependent hysteresis loops in perpendicular recording media have been measured by iteratively correcting the demagnetization effect in order to maintain the internal total field at a fixed angle. Both the angle and the magnitude of the applied field are adjusted simultaneously to compensate for the demagnetization field change. Significant differences have been observed between the conventional angular-dependent hysteresis loop with a constant applied field angle and the intrinsic angular-dependent hysteresis loop with a fixed total field angle. Without demagnetization corrections, the field range in which irreversible magnetization occurs changes as a function of the field angle, whereas it remains constant if proper demagnetization field corrections are applied. 相似文献
11.
R. M. Feshchenko A. V. Vinogradov 《Journal of Experimental and Theoretical Physics》2018,127(2):274-278
Relations determining the number of photons in an electromagnetic field are considered from the point of view of a classical electromagnetic field. A relativistically invariant expression is obtained for the number of emitted photons in terms of charges and currents producing the electromagnetic field. Examples are considered for calculating the numbers of photons in the electromagnetic field for the case of the electric dipole radiation field, as well as the field of a finite and spatially restricted electromagnetic pulse. 相似文献
12.
T. S. Li S. C. Chang M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(4):497-505
The electronic and transport properties of nanotube-ribbon hybrids
subject to the influences of
a transverse electric field are investigated theoretically.
The energy dispersion relations are found to exhibit rich dependence on the
nanotube-ribbon interactions, the field strength, and the geometry of the hybrids.
The nanotube-ribbon coupling will
modify the subband curvature, create additional band-edge states, and
change the subband spacing or energy gap. The bandstructures are asymmetric and symmetric about the Fermi energy when the
interactions are turned on and off, respectively.
The inclusion of a transverse electric field will further alter
the bandstructures and lift the degeneracy of the partial
flat bands in hybrid (IV). The chemical-potential-dependent
electrical and thermal conductance exhibit a stepwise increase
behavior. Variations in the electronic structures with field
strength will be reflected in the electrical and thermal
conductance. Prominent peaks, as well as single-shoulder and
multi-shoulder structures in the electrical and thermal conductance
are predicted when varying the electric field strength and the
nanotube location. The features of the conductance are found to be
strongly dependent on the field strength, the geometry and the
temperature. 相似文献
13.
This paper discusses the induced radiation of electrons in the field of a plane electromagnetic wave propagating along the intensity vector of a uniform magnetic field. Expressions are obtained for the power and frequencies of the radiation. The role of the polarization of the plane wave in the radiation process and the effect of the magnetic field present on the induced radiation in the field of a plane wave are investigated. Several specific cases are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 49–55, April, 1979. 相似文献
14.
S. Habib Mazharimousavi 《Annalen der Physik》2023,535(1):2200249
In the framework of an electromagnetic field coupled nonminimally with a scalar field in flat spacetime, the existence of a non-singular electric field is proved for a point electric charge or electric monopole. In analogy with the Maxwell-dilaton system introduced by Gibbons and Wells, first, a Maxwell-anti-dilaton system is constructed where the radial electric field of a static electric monopole is coupled to an anti-dilaton. The field equations are solved analytically for the electric and dilaton fields and observe the nonsingular electric field. Also, the self-energy of the electric monopole is found to be finite. Furthermore, the formalism to a Maxwell-scalar field is generalized where a mechanism is introduced upon which the coupled regular-electric field and scalar field is obtained. The formalism shows that for a given regular electric field there are two supersymmetric coupling functions corresponding to a scalar and a phantom field. 相似文献
15.
ZHANG Hongying XIA Yuanqin CHEN Deying XIAO Pan FAN Rongwei & MA Zuguang State Key Laboratory of Tunable Laser Technology Institute of Opto-Electronics Harbin Institute of Technology Harbin China 《中国科学G辑(英文版)》2005,48(1):78-88
Theoretically based on the four-level model, one LICET process in Eu-Sr system in both weak and strong fields was calculated by immediate numerical integrations. Numerical results in weak field are in fair to good agreement with analytical ones. Numerical results in strong field show that: (a) the peak of the LICET profiles moves to the violet side and the tuning range of the profiles obviously becomes narrower when the laser field intensity increases; and (b) numerical results in strong field differ a lot from analytical ones, which indicates that in strong field, the analytical expressions are not applicable any longer. 相似文献
16.
The Mössbauer spectra of a permalloy film placed in an rf magnetic field are measured. The film is so thin that transverse magnetostriction oscillations are not excited in it. This permits the observation of satellites that are due solely to periodic variations of the magnetic field at the nucleus. The data are in good agreement with calculations performed in the model of step-wise field reversals. On application of an additional static magnetic field the splitting of the satellites is observed, as predicted by the model of asymmetric step-wise field reversals. 相似文献
17.
Yu. P. Mel’nikov 《Journal of Experimental and Theoretical Physics》2000,90(3):460-469
The nonlinear collision integral for the Green’s function averaged over a random magnetic field is transformed using an iteration procedure taking account of the strong random scattering of particles on the correlation length of the random magnetic field. Under this transformation the regular magnetic field is assumed to be uniform at distances of the order of the correlation length. The single-particle Green’s functions of the scattered particles in the presence of a regular magnetic field are investigated. The transport coefficients are calculated taking account of the broadening of the cyclotron and Cherenkov resonances as a result of strong random scattering. The mean-free path lengths parallel and perpendicular to the regular magnetic field are found for a power-law spectrum of the random field. The analytical results obtained are compared with the experimental data on the transport ranges of solar and galactic cosmic rays in the interplanetary magnetic field. As a result, the conditions for the propagation of cosmic rays in the interplanetary space and a more accurate idea of the structure of the interplanetary magnetic field are determined. 相似文献
18.
Manuk G. Barseghyan Albert A. Kirakosyan 《Physica E: Low-dimensional Systems and Nanostructures》2005,28(4):471-481
The quantum states and energy spectrum of an electron in a rectangular step quantum well in a magnetic field parallel to the plane of two-dimensional electronic gas are investigated. It is shown that the joint effect of a magnetic field and confining potential of quantum well results in radical change of the electron energy spectrum. The energy dependencies on the parameters of the quantum well and magnetic field induction are investigated. Numerical calculations are carried out for an AlAs/ GaAlAs/ GaAs/ AlAs step quantum well. 相似文献
19.
Mechanisms underlying the formation and dynamics of a virtual cathode (VC) in a tubular electron beam subjected to a magnetic
field are studied using a numerical 2D model. Two qualitatively different competing types of space charge dynamics near the
VC are discovered. Which of them predominates depends on the magnetic field strength. The beam current critical density at
which a nonstationary VC forms in the system is also strongly dependent on the magnetic field. It is shown that the optimal
strength of the magnetic field that minimizes the beam current critical density depends on the Brillouin magnetic field. 相似文献
20.
The quantum mechanical two — particle problem is considered in hot dense nuclear matter under the influence of a strong electric field such as the field of the residual nucleus in heavy — ion reactions. A generalized Galitskii-Bethe-Salpeter equation is derived and solved which includes retardation and field effects. Compared with the in-medium properties in the zero-field case, bound states are turned into resonances and the scattering phase shifts are modified. Four effects are observed due to the applied field: (i) A suppression of the Pauli-blocking below nuclear matter densities, (ii) the onset of pairing occurs already at higher temperatures due to the field, (iii) a field dependent finite lifetime of deuterons and (iv) the imaginary part of the quasiparticle self-energy changes its sign for special values of density and temperatures indicating a phase instability. The latter effect may influence the fragmentation processes. The lifetime of deuterons in a strong Coulomb field is given explicitly. 相似文献