A note on the theory of spin wave resonance in spiral structures

The appearance of two resonant modes of spin waves with different non-zero wave vectors is theoretically predicted for a magnetic arrangement of the type of an antiferromagnetic spiral combined with weak antiferromagnetism in the direction of the spiral axis. A study is made of the question of the Hamiltonian suitable for possible applications of the chosen magnetic arrangement, and the possibility of energetic stability of the considered magnetic structure for two concrete realistic forms of the Hamiltonian is pointed out.The author expresses his sincere thanks for valuable discussions and stimulating comments to Dr. S. Krupika and Dr. J. Loos, P. Novák and I. Veltruský of the Institute of Solid State Physics of the Czechoslovak Academy of Sciences, and to Assoc. Prof. J. Morkowski and Assoc. Prof. L. Kowalewski of the Polish Academy of Sciences and Poznan University.     

Lopsided spiral galaxies

The light distribution in the disks of many galaxies is ‘lopsided’ with a spatial extent much larger along one half of a galaxy than the other, as seen in M101. Recent observations show that the stellar disk in a typical spiral galaxy is significantly lopsided, indicating asymmetry in the disk mass distribution. The mean amplitude of lopsidedness is 0.1, measured as the Fourier amplitude of the m=1$m=1$ component normalized to the average value. Thus, lopsidedness is common, and hence it is important to understand its origin and dynamics. This is a new and exciting area in galactic structure and dynamics, in contrast to the topic of bars and two-armed spirals (m=2)$(m=2)$ which has been extensively studied in the literature. Lopsidedness is ubiquitous and occurs in a variety of settings and tracers. It is seen in both stars and gas, in the outer disk and the central region, in the field and the group galaxies. The lopsided amplitude is higher by a factor of two for galaxies in a group.     

Magnetic fields in spiral galaxies

Radio polarization observations have revealed large-scale magnetic fields in spiral galaxies. The average total field strength most probably increases with the rate of star formation. The uniform field generally follows the orientation of the optical spiral arms, but is often strongest outside the arms. Long magnetic-field filaments are seen, sometimes up to a 30 kpc length. The field seems to be anchored in large gas clouds and is inflated out of the disk, e.g. by a galactic wind. The field in radio halos around galaxies is highly uniform in limited regions, resembling the structure of the solar corona. The detection of Faraday rotation in spiral galaxies excludes the existence of large amounts of antimatter. The distribution of Faraday rotation in the disks shows two different large-scale structures of the interstellar field; axisymmetric-spiral and bisymmetric-spiral, which are interpreted as two modes of the galactic dynamo driven by differential rotation     

Gravitational lensing by spiral galaxies

Spiral galaxies at moderate redshifts and oriented optimally could form characteristic multiple images of extended background sources from which the mass distribution in the galaxy can be estimated. The absorption profile due to the galaxy provides a reliable tool for the chemical and thermal diagnostic of the lens.     

The Hubble law and the spiral structures of galaxies from equations of motion in general relativity

Fully exploiting the Lie group that characterizes the underlying symmetry of general relativity theory, Einstein's tensor formalism factorizes, yielding a generalized (16-component) quaternion field formalism. The associated generalized geodesic equation, taken as the equation of motion of a star, predicts the Hubble law from one approximation for the generally covariant equations of motion, and the spiral structure of galaxies from another approximation. These results depend on the imposition of appropriate boundary conditions. The Hubble law follows when the boundary conditions derive from the oscillating model cosmology, and not from the other cosmological models. The spiral structures of the galaxies follow from the same boundary conditions, but with a different time scale than for the whole universe. The solutions that imply the spiral motion areFresnel integrals. These predict the star's motion to be along the “Cornu Spiral.” The part of this spiral in the first quadrant is the imploding phase of the galaxy, corresponding to a motion with continually decreasing radii, approaching the galactic center as time increases. The part of the “Cornu Spiral” in the third quadrant is the exploding phase, corresponding to continually increasing radii, as the star moves out from the hub. The spatial origin in the coordinate system of this curve is the inflection point, where the explosion changes to implosion. The two- (or many-) armed spiral galaxies are explained here in terms of two (or many) distinct explosions occurring at displaced times, in the domain of the rotating, planar galaxy.     

Optimization of quasiperiodic structures in a linear resonance ion accelerator

A method is proposed for optimizing the parameters of a linear ion accelerator with rectangular or trapezoidal shape of the accelerating voltage between the tubes, systematic allowance being made for the quasiperiodicity of their arrangement. Numerical calculations have demonstrated the effectiveness of the method and also the fairly simple structure of its realization. A detailed algorithm is given. An estimate is made of the interval of entrance phases, the maximal value of which exceeds by several percent the limits previously predicted.Translated from Izvestiya Vysshikh Uchebnykh" Zavedenii, Fizika, No. 6, pp. 81–85, June, 1980.     

Higgs scalar–tensor theory for gravity and the flat rotation curves of spiral galaxies

The scalar–tensor theory of gravity with the Higgs field as scalar field is presented. For central symmetry it reproduces the empirically measured flat rotation curves of galaxies. We approximate the galaxy by a polytropic gas sphere with the polytropic index γ = 2 and a massive core.     

Three-dimensional spiral structures in a ferromagnet

New types of three-dimensional spiral structures are found in an isotropic ferromagnet.     

Parabolic drift towards homogeneity in large-scale structures of galaxies

To describe the progressive transition in large-scale structures of galaxies from a seemingly fractal behavior at small scales to a homogeneous distribution at large scales, we use a new geometrical framework called entropic-skins geometry which is based on a diffusion equation of scale entropy through scale space. In the case of an equipartition of scale entropy losses in scale space, it is shown that fractal dimension (varying from 0 to 3) depends linearly on the logarithm of scale from the average size l_c of galaxies until a characteristic length scale l₀ beyond which distribution becomes homogeneous. A simple parabolic expression for correlation function can be derived: ln(1+ξ_i)=(β/2)ln²(l_o/l_i) with β=3/ln(l₀/l_c)≈0.32 and . This law has been verified using correlation functions measured on several redshift surveys.     

A theory of the cyclotron resonance klystron

A new type of cyclotron resonance generator which has a klystron mechanism for bunching the electrons (a CRK) is studied from a theoretical standpoint. Expressions are obtained for the starting and optimal currents and for the efficiency of the CRK when the initial spreads in the energy of the electrons and in their angle of injection are taken into account. It is shown that efficiency may exceed 50% in a CRK constructed as a two-cavity klystron and reaches 60% in a CRK constructed as a three-cavity klystron. When this happens, the requirements on beam quality are fairly low. Thus, in high-power CRKs the initial spread in energy of the electrons and their angle of injection may be several percent with no major loss of efficiency.Electrophysics Institute, Uralsk Department, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 2, pp. 177–189, February, 1991.     

A faulted matrix model for the spiral growth of polytype structures

A faulted matrix model for the spiral growth of polytype structures is proposed and takes into account the presence of stacking faults in the basic structure. The most probable structures theoretically deduced from such a model are shown to be in excellent agreement with those actually observed in PbI₂.     

A convergent star product for linear Poisson structures

An explicit star product ⋆ _α ^Γ on the dual of a general Lie algebra equipped with the linear Poisson bracket is constructed. An equivalence operator between this star product and the Kontsevich star product in [K₁] is given and diverse properties of the star product ⋆ _α ^Γ are studied. It is also proved that the star product ⋆ _α ^Γ provides a convergent deformation quantization in the sense of Rieffel [R₁].     

A remark on an anomaly of the spin-wave spectrum in spiral spin structures

It is shown that magnetic dipolar interaction gives rise to a discontinuity in the magnon dispersion relation for antiferromagnetic spiral spin structures. Some numerical results for the magnon energy in dysprosium are presented.     

Centrifugal instability in rotating shallow water and the problem of the spiral structure in galaxies

A new instability predicte by theory to occur in rotating shallow water in which the rotation velocity has a discontinuity, in a regime where the flow velocity exceeds the characteristics velocity of the waves, has been found experimentally. The instability develops when the radial gradient of the angular velocity across the discontinuity is negative; such an instability is likely to be responsible for the formation of the spiral structure in galaxies which have a similar rotational velocity profile.     

A new theory on scattering of electrons due to spiral dislocations

The topologically singular lattice structure around a spiral dislocation scatters electrons in a manner much different from the deformation-potential-scattering. Thet-matrix is represented ast(k, k)=t ₀ sin (k _z/2) exp (±i _kk/2)/sin ( _kk/2) with the scattering angle _kk, the componentk _z of the wave vector parallel to the dislocation, andt ₀(Fermi energy). This kind of scattering alone does not cause a perpendicular resistivity, but in a dirty limit a specific dislocation resistivity does exist, whose relaxation time per unit length of dislocation is of the order of/(Fermi energy).Work performed within the research program of the Sonderforschungsbereich 125 Aachen-Jülich-KölnOn leave of absence from Department of Materials Science, Hiroshima University, Higashisenda-machi, Hiroshima, Japan     

由同时具有磁谐振和电谐振结构组成的左手材料

为了在同一结构中同时实现负介电常数和负磁导率(双负),采用一种“巨”字形结构,利用丝网印刷技术在氧化铝基板上进行加工制作,并通过仿真和实验测试证实了这种结构的“双负”特性. 与利用磁谐振器和电谐振器组阵实现左手材料的方法相比,这种单一结构可以同时实现负介电常数和负磁导率,制作方便,等效电路简单,双负频段较宽. 利用丝网印刷技术进行样品的制作,工艺简单,成本低廉. 关键词： 左手材料 磁谐振 电谐振     

基于宽边耦合螺旋结构的低频小型化极化不敏感超材料吸波体

设计、仿真并实验验证了基于宽边耦合螺旋结构的低频小型化超材料吸波体. 实验测试结果表明, 该超材料吸波体在1.39 GHz吸收率达到最大为98%, 其单元尺寸和总厚度均为6.8 mm, 约为1/32工作波长, 实现小型化窄带吸波. 由于吸波体中螺旋结构是旋转对称排列的, 因而其对垂直入射电磁波的极化方向是不敏感的. 此外, 该超材料吸波体对斜入射横电和横磁极化电磁波在60°时, 仍具有强吸收. 关键词： 超材料 吸波体 小型化     

Dual resonance theory

It is suggested that a dual model could provide a Born approximation to a complete theory of hadrons. After reviewing various properties of Veneziano model amplitudes, including their underlying algebraic structure, more recent developments are discussed. The spectrum generating algebra is constructed and used to prove the no-ghost theorem for space-time dimension d ? 26. A modification of the Veneziano model incorporating SU(N) symmetry in a dynamical fashion is shown to have critical dimension 26?N. A detailed discussion of the dual pion model and its extension to fermions is presented. It is proved that both the meson and fermion sectors are ghost free for d ? 10. Finally, there is a discussion of nonplanar models and their possible connection with the pomeron singularities arising from nonplanar loop diagrams.     

Intergalactic obscuring matter and holes between cluster structures of galaxies

Summary The location of individual intergalactic dark clouds, as well as the search for obscuring matter in some scantly populated areas between clustering structures so far has led to no final conclusion. In several cases, however, arguments can be set forth in favour of the thesis that some dark clouds are located in regions of space scantly populated with galaxies. Paper presented at the Congress “Galactic and Extragalactic Dark Matter”, Roma, 28 to 30 June 1983.     

Nonlinear dynamics of breathers in the spiral structures of magnets

The structure and properties of pulsating solitons (breathers) in the spiral structures of magnets are analyzed within the sine-Gordon model. The breather core pulsations are shown to be accompanied by local shifts and oscillations of the spiral structure with the formation of “precursors” and “tails” in the moving soliton. The possibilities for the observation and excitation of breathers in the spiral structures of magnets and multiferroics are discussed.