Elementary Forces Research Articles

超電導体における磁束ピンニングの理論に関する最近の問題点

A review is given on recent topics on theories of flux pinning in superconductors. It covers the problem of estimate of elementary pinning forces of individual pinning centers interacting with flux lines and the summation problem to calculate the global pinning force density.As pointed out by Thuneberg, the elementary pinning force of pinning centers much smaller than the BCS coherence length should be reestimated by taking account of the electron-scattering effect. And calculations of the elementary pinning force of grain boundaries from the electron-scattering effect are briefly reviewed. Their dependence on the impurity parameter is opposite to the theoretical result of Thuneberg.The summation theories are reviewed and a significance of instabilities of flux lines appeared in the Labusch theory is emphasized. Then, recent two theories, the Larkin-Ovchinnikov theory and the mean field approximation theory are compared and problems contained in two theories are discussed.

About Group Representations in Grand Unified Theories

The main purpose of this article is to systematize group theory methods in Grand Unified Theories (GUTs). An exact representation structure for all admissible groups that unify elementary forces is analysed. The implications of requirements asymptotic freedom for standard SU (3)c ⊗ SU(2)L ⊗ U(1)y model is investigated in detail. It is shown how restrictive are such assumptions in unified model building. As a result the maximal number of families is five independently on the kind of considered model. In several cases this number is even smaller. The maximal horizontal structure of interactions which is possible to embed into unification scheme is also discussed for all admissible models. The number of superheavy particles is evaluated in different unifying schemes.

A grand unified composite model

If certain unusual assumption about chiral symmetry breaking and dynamical mass generation are valid the gauge hierarchy problem is solved naturally and all elementary particle forces are unified into a single semi-simple gauge group. Three ordinary and two exotic families of fermions exist below 1 TeV.

N=8 supergravity and Kaluza-Klein axial anomalies

By consideration of the ten-dimensional supersymmetric string theory which may underly unification of gravity with the other elementary particle forces it is argued that the light fermions must reflect the cancellation of Kaluza-Klein axial anomalies in ten dimensions. Using a gauge group SU(8), and assuming that both dimensional compactification and supersymmetry breaking occur at the Planck scale, we arrive at a set of fermions consistent with the observed light quarks and leptons including the replication of families.

A Unified Theory of Elementary Particles and Forces

A Unified Theory of Elementary Particles and Forces

Can all elementary particle forces be unified at 100-1000 TeV?

A modest proposal to deal with the gauge hierarchy problem is suggested by removing the necessary conditions for a huge ratio of vacuum expectation values. Instead of the grand unification at 10/sup 15/ GeV, we unify the electroweak and strong interactions at a low energy 100 --1000 TeV. The observed values of sin/sup 2/theta/sub W/ and ..cap alpha../sub s/ are used as inputs in the determination of the group in the SU(N) series. The currently favored values of sin/sup 2/theta/sub W/ and ..cap alpha../sub s/ put a limit on N> or =9. In this kind of grand unification, proton stability is a necessity for consistency.

The volume pinning force for periodical interaction forces between defects and the flux line lattice

The volume pinning force for some forms of the interaction potential defect-flux line is calculated without restrictions on the vortex lattice distance and the interaction range of defects. It is shown that for larger maximum elementary interaction forces, the direct summation of pinning forces is realistic. However, if the interaction range of the defects is smaller than the vortex lattice distance, one obtains a region (about one order of magnitude) in which Labusch's quadratic dependence of the volume pinning force on the elementary interaction force is valid. In the region where the direct summation of pinning forces occur, the volume pinning force is proportional the vortex lattice distance and one obtains an additional magnetic field dependence of the volume pinning force.

Weak Interactions: Unification of Elementary Forces and Gauge Theories . Papers from a conference, Batavia, Ill., Oct. 1977. David B. Cline and Frederick E. Mills, Eds. Harwood Academic Publishers, London, 1978 (available in U.S. from P.O. Box 786, Cooper Station, New York, N.Y. 10003). xxii, 770 pp., illus. $39.50

Weak Interactions: <i>Unification of Elementary Forces and Gauge Theories</i> . Papers from a conference, Batavia, Ill., Oct. 1977. David B. Cline and Frederick E. Mills, Eds. Harwood Academic Publishers, London, 1978 (available in U.S. from P.O. Box 786, Cooper Station, New York, N.Y. 10003). xxii, 770 pp., illus. $39.50

Determination des efforts exerces par le vent sur un brise-vent

When it is planned to erect artificial windbreaks, it is necessary to estimate the stress that will be exerted by the wind in order to calculate the mechanical characteristics of the supports. To that end, this paper proposes simple fomulas to calculate the drag coefficients of artificial windbreaks, based on their geometrical characteristics. The drag force exerted by the wind on a windbreak having an height H can be written: $$D = \tfrac{1}{2}C_{dh} \rho u^2 \left( H \right) \cdot H$$ for unit length and taking the reference wind speed u(H) at H level. The drag coefficient C dh is calculated by integrating elementary drag forces between ground level and H level, which can be written as: $${\text{d}}D = \tfrac{1}{2}C_d \rho u^2 \left( z \right){\text{d}}z$$ C d being the drag coefficient of a grid element as determined in an uniform flow. Considering the logarithmic wind profile u(z)= u */k ln z/z 0 and integrating between z 0 and H leads to the following relation between C dh and C d: $$\frac{{C_{dh} }}{{C_d }} = 1 - \frac{2}{{\ln H/z_0 }} + \frac{2}{{\left( {\ln H/z_0 } \right)^2 }}$$ which is illustrated by Figure 2. The drag coefficient C d may be determined as a function of windbreak porosity φ following the works of Valensi and Rebont (1959) and Castro (1971). Valensi and Rebont propose: $$C_d = 2.\frac{{1 - m^2 \phi ^2 }}{{1 + m^2 \phi ^2 }}$$ with m = 0.95 for a metal web and 0.9 < m < 0.95 for a perforated plate (Figure 1). From Castro's work, lower C d values may be derived by adjusting his experimental values to a fourth-degree polynomial: $$C_d = 1.85 - 1.74\phi - 0.85\phi ^2 + 1.73\phi ^3 - \phi ^4$$ . Using these relationships, it is possible to calculate C dh knowing φ and H/z 0. The results of computations for H/z 0 = 200 are compared with the experimental results of Tani (1958), Hagen and Skidmore (1971), Seginer (1975) and de Bray (1971) in Figure 3. While C dh estimations based on C d values derived from Valensi and Rebont (1969) are in good agreement with experimental values of Tani, Hagen and Skidmore and Seginer, calculations derived from Castro's data agree well with de Bray's results. It is not possible at the present time to decide which is the more suitable relationship, but it seems preferable for structure computations to adopt C d values based on the work of Valensi and Rebont. The determination of the application point of the drag force leads to the relation $$\frac{{z_1 }}{H} = \frac{1}{2}\frac{{\left( {\ln H/z_0 } \right)^2 - \ln H/z_0 + \tfrac{1}{2}}}{{\left( {\ln H/z_0 } \right)^2 - 2\ln H/z_0 + 2}}$$ giving the z 1 level of this point. The variation of z 1/H as a function of H/z 0 is given in Figure 4.

Radiation-induced flux pinning in type II superconductors

In monocyrstalline foils of oxygen-doped niobium and niobium—zirconium alloys, statistically distributed or regularly arranged voids were created during irradiation with high-energy 58Ni+ ions (3.5MeV, up to 8.1 × 1016 ions/cm2) at temperatures between 750 and 900°C. The voids exhibit a strong interaction with flux lines, which was determined from measurements of the (anisotropic) critical currents as a function of transverse magnetic field, temperature, and defect geometry. The experimentally determined volume pinning forces obey scaling laws and lead to elementary interaction forces between voids and fluxoids that are larger than theoretical values calculated for various possible mechanisms of interaction. The validity of the statistical summation of elementary forces is discussed.

Geometrical gauge theory of gravity and elementary particle forces

The basic forces of nature, mediated by spin-one and spin-two particles, are unified within a geometrical gauge theory. Gravity, electromagnetism, and strong forces are described by two nonsymmetric fields ${g}_{\ensuremath{\mu}\ensuremath{\nu}}$ and ${s}_{\ensuremath{\mu}\ensuremath{\nu}}$. Field equations are derived from a variational principle. The field equations possess an exact (classical) nonsingular solution that corresponds to a geometrical object called a gheon (gravitational-hadronic-electromagnetic entity). Space inside a gheon is Euclidean four-dimensional and a gheon can have event horizons. The gheons describe hadrons and at the classical level permanently confine quarks. The event horizons trap normal hadrons and can also radiate them, producing a thermal hadronic spectrum. There exists a limit in which the field equations reduce to Einstein-Maxwell equations. In this limit, the gheons shrink to point singularities. By matching the boundary conditions of the solutions of a scalar field equation on the surface of a gheon, a discrete mass spectrum for a scalar particle is obtained. A hadronic mass formula of the Gell-Mann-Okubo type is derived for an isolated black gheon.

Flux pinning in heavy ion irradiated type II superconductors

In single crystalline foils of type II superconducting Nb and Nb alloys, dislocation loops and voids were created during high temperature (400–1000°C) irradiation with Ni ions (3.2–3.5 MeV, up to 8 × 10 16 ions/cm 2 ). Both defect agglomerates exhibit a strong interaction with flux lines, which was determined from measurements of transverse critical currents or volume pinning forces P υ. P υ , as a function of field and temperature, obeys a scaling law (for samples containing voids) and permits the determination of elementary pinning forces, which are compared with theoretical models. The validity of the statistical summation is discussed.

The volume pinning force for different shapes of the interaction potential between defects and flux lines

The volume pinning force in superconductors with randomly distributed line defects nearly perpendicular to the flux lines is calculated for model as well as realistic interaction potentials between single defects and single flux lines. Both attractive and repulsive interactions defect — flux line were considered. The line defects were constructed from point defects distributed with constant density on straight lines. The deviations of the results from the theory of Labusch are considerable for small elementary interaction forces between defects and flux lines. The deviations (as well as the differences between repulsive and attractive interaction potentials) are larger for the realistic interaction potential than those for the different model potentials. The threshold values for the flux line distortion (under which no net volume pinning can exist) is also given.

Infrared singularities and massive fields

We examine some problems associated with the low-momentum behavior of gauge theories and other renormalizable field theories. Our main interest is in the infrared structure of unbroken non-Abelian gauge theories and how this is affected by the presence of other heavy fields coupled to the massless gauge fields. It is shown in the context of a simple model of gauge mesons coupled to massive fermions that the heavy fields decouple at low momenta except for their contribution to renormalization effects. This result is used to discuss the mass-shell structure of the fermion propagator. The decoupling theorem is then stated for a general renormalizable theory and applied to some interesting examples. One is a more general gauge theory which makes use of the Higgs mechanism and attempts to unify the elementary particle forces. Another is the connection of the linear and nonlinear $\ensuremath{\sigma}$ models in the limit ${m}_{\ensuremath{\sigma}}\ensuremath{\rightarrow}\ensuremath{\infty}$.

Investigation of the relation between the force of friction and “Elementary forces”. (in Russian) : A. V. Bulgadaev. Doklady akademii nauk SSSR, v. 97, no. 5, Aug. 11, 1954, p. 805–808

Investigation of the relation between the force of friction and “Elementary forces”. (in Russian) : A. V. Bulgadaev. Doklady akademii nauk SSSR, v. 97, no. 5, Aug. 11, 1954, p. 805–808

The Concept "Social Forces" in American Sociology. Section V. The "Interest" Concept

With the publication of his General Sociology in 1905, Small advertised a new type of classification of human motives, designated by the term interest. He gave Ratzenhofer credit for the term and for the general idea, but Small's interests concept seems to be something quite different from anything he found in Ratzenhofer's writings. Ellwood, Blackmar and Gillin, Ross, and Southard and Jarrett have referred with approval and with varying degrees of emphasis tot he interests concept as developed by Small; most of these writers treat it as a term designating a class of social forces which subsist alongside of the more elementary social forces. The interest concept is one which is still at the time of writing involved in a process of competition with several others for prestige and utilization.

INHIBITORY ACTION OF THE CEREBRUM.

Irritability and contractility are primary properties of protoplasm. In their earliest forms they express the simple play of elementary chemical and physical forces. In undifferentiated protoplasm, they exist as general diffused properties of reacting to incident forces indifferently in all directions. The progressive differentiation of form and function expressive of organic progress implies the development of specific irritability or susceptibility to specific excitants, along with the capacity to react in definite ways to these excitants. It implies further the development of a nervous mechanism by which this special irritability is manifested, and through which the reactionary impulses are transmitted to be developed into organic activities. The special senses are special developments of this irritability, and the varied motor activities of animals are derivatives of this primary contractility manifested by protoplasm. All organic reactions involve a reflex element or factor in that they are in a sense responses to stimuli