首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 295 毫秒
1.
It is shown that for spinorial charges Q(L))α (α = 1, 2, L = 1, …, S) satisfying the commutation relations
{Q(L)α, Q(M)β} = εαβaLMQ,
{Q(L)α, Q(M)+β} = cσμαβPμδLM,
[Q(L))α, Pμ] = 0,
where Q is a scalar charge commuting with the spinor charges as well aswith the energy- momentum vector Pμ, there can exist several different multiplets for free massive scalar and spinor fields.  相似文献   

2.
From the scaling law for the s-channel partial wave amplitudes, which guarantees simultaneously t-channel unitarity at threshold t = 4μ2 and s-channel unitarity, we derive: (i) The intercept α(0) of the Pomeron is always one, if α(4μ2) > 1. (ii) The total and the elastic cross sections are bounded from below for s → ∞.
σtot ? O((logss1)2δ(4μ2)), σel ? O((logss1)4δ(4μ2)?1)
where α(4μ2) and δ(4μ2) are the position and the type of te Pomeron singularity (J ? α(4μ2))?1?δ(4μ2) at t = 4μ2. (iii) The type of the Pomeron singularity δ(4μ2) is restricted: either δ(4μ2) ? 12 or δ(4μ2) ? 12.  相似文献   

3.
The temperature dependence of the field emission flicker noise spectral density functions has been investigated for potassium adsorbed on tungsten (112) planes by a probe hole technique. By integration of the spectral density functions W(?) = Bi??gei the noise power (δn2Δ? for different frequency intervals Δ? is obtained. From the exponential temperature dependence of (δn2Δ? noise power “activation energies” qΔ? are determined. Plots of these energies versus coverage show a similar “oscillating” behaviour as recently found for W(?j) or (δn2Δ?j which indicates phase transitions of the adsorbed potassium submonolayers. The noise activation energies are discussed in terms of existing models and a comparison is made between the experimental q values and surface diffusion energies Ed as determined by conventional methods.  相似文献   

4.
The Coriolis interactions between ν1 and ν3, and between ν2 and ν3 in SO2 have been analyzed to obtain the signs of the products ζ3.1c(a?Q3)(b?Q1) and ζ3.2c(a?Q3)(b?Q2). It has been found that both of the signs of these products are positive. Then, relative signs of (?Q1) have been determined using the calculated values of the Coriolis zeta constants for the present definition of the normal coordinates. The obtained sign combination of (?Qi) is ±(+?+), which agrees with the one predicted by the molecular orbital calculations. Using the sign combination (+?+), the polar tensors of S and O atoms were also calculated.  相似文献   

5.
During the last few years many dynamical systems have been identified, that are completely integrable or even such to allow an explicit solution of the equations of motion. Some of these systems have the form of classical one-dimensional many-body problems with pair interactions; others are more general. All of them are related to Lie algebras, and in all known cases the property of integrability results from the presence of higher (hidden) symmetries. This review presents from a general and universal viewpoint the results obtained in this field during the last few years. Besides it contains some new results both of physical and mathematical interest.The main focus is on the one-dimensional models of n particles interacting pairwise via potentials V(q) = g2ν(q) of the following 5 types: νI(q)=q?2, νII(q)=a?2sinh2(aq), νIII(q)=a2/sin2(aq), νIV=a2P(aq), , νV(q)=q?22q2. Here P(q) is the Weierstrass function, so that the first 3 cases are merely subcases of the fourth. The system characterized by the Toda nearest-neighbor potential, gj2exp[-a(qj?qj+1)], is moreover considered. Various generalizations of these models, naturally suggested by their association with Lie algebras, are also treated.  相似文献   

6.
The relativistic correction (RC) to the deuteron magnetic moment is calculated using the light-cone dynamics. The restrictions imposed by the angular condition on the electromagnetic current operator of the deuteron are discussed in detail. It is shown that the additive model for the current operator of interacting constituents is consistent with the angular condition only for the two first terms of the expansion of the “good” current component j+ = 12(j0 + jz) in powers of the momentum transfer q. The RC to μd is expressed through the matrix element of the “good” component j+ and is found to be equal to (0.6–0.8) × 10?2 eh?/2mpc for realistic NN potentials. Taking account of RC decreases essentially the discrepancy between the theoretical and experimental values of μd. Possible solutions of the angular condition for squared q-terms of the j+ current component are also discussed.  相似文献   

7.
The influence of self-fields on the equilibrium and stability properties of relativistic beam-plasma systems is studied within the framework of the Vlasov-Maxwell equations. The analysis is carried out in linear geometry, where the relativistic electron beam propagates through a background plasma (assumed nonrelativistic) along a uniform guide field B0e?z, It is assumed that νγ0 ? 1 for the beam electrons (ν is Budker's parameter, and γ0mc2 is the electron energy), but no a priori assumption is made that the beam density is small (or large) in comparison with the plasma density, or that conditions of charge neutrality or current neutrality prevail in equilibrium. It is shown that the equilibrium self-electric and self-magnetic fields, Ers(r)e?r and Bθs(r)e?θ, can have a large effect on equilibrium and stability behavior. Equilibrium properties are calculated for beam (j = b) and plasma (j = e, i) distribution functions of the form fb0(H, Pθ, Pz) = F(H ? ωrbPθ) × δ(Pz ? P0)(j = b), and fj0(H, Pθ, Pz) = fj0(H ? ωrjPθ ? VjPz ? miVj22) (j = e, i), where H is the energy, Pθ is the canonical angular momentum, Pz is the axial canonical momentum, and ωrj (the angular velocity of mean rotation for j = b, e, i), Vj (the mean axial velocity for j = e, i), and P0 are constants. The linearized Vlasov-Maxwell equations are then used to investigate stability properties in circumstances where the equilibrium densities of the various components (j = b, e, i) are approximately constant. The corresponding electrostatic dispersion relation and ordinary-mode electromagnetic dispersion relation are derived (including self-field effects) for body-wave perturbations localized to the beam interior (r <Rb). These dispersion relations are analyzed in the limit of a cold beam and cold plasma background, to illustrate the basic effect that lack of charge neutrality and/or current neutrality can have on the two-stream and filamentation instabilities. It is shown that relative rotation (induced by self-fields) between the various components (j = b, e, i) can (a) result in modified two-stream instability for propagation nearly perpendicular to B0e?z, and (b) significantly extend the band of unstable kz-values for axial two-stream instability. Moreover, in circumstances where the beam-plasma system is charge-neutralized but not current-neutralized, it is shown that the azimuthal self-magnetic field Bθs(r)e?θ has a stabilizing influence on the filamentation instability for ordinary-mode propagation perpendicular to B0e?z.  相似文献   

8.
t-channel unitarity equations are derived for n-particle overlap functions. Together with s-channel unitarity they lead to scaling laws for the inelastic s-channel partial-wave amplitudes ?l(n)(s) in the limits s → ∞, l → ∞ x = l (μ√s)3 = fixed. Assuming the validity of the scaling law in the whole range, allowed by s-channel unitarity — i.e. for l > L (s) = (α(4μ2) ? 1) (s) log (ss1) we obtain constant production cross sections σ(n)(s) at high energies s → ∞ up to s factors.  相似文献   

9.
Given a mapping x → ?(λ,x), whose bifurcation points accumulate at λ = Λ, it is shown that the iterates (?α) [?2p?μ/δp, X+y/(?α)p)?X] converge to a function ψ(μ,y)asp→∞, where X maximizes ?(Λ∞,x). The function ψ is universal up to scaling in μ and y, and satisfies ψ(μ/δ,ψ(μ/δ,?y/α)) = ?α?1ψ(μ,y). This result generalizes the well-known Feigenbaum universal function g(y) with g(g(?y/α)) = ?g(y/α, which is the special case for μ = 0.  相似文献   

10.
The threshold behaviour of pion production presented in our earlier work is successfully compared with the new SPEAR data. By using duality and sum rules we derive FT(π+)(x) ≈ FL(π+)(x) ≈ FT(π0)(x) ? FL(π0)(x) for x near 1. An accompanying results is σπA2(s) ≈ 2σπω(s) ≈ 4σππ(s) ≈ 9(m?2/s)3σμμ for large s.  相似文献   

11.
Nuclear spectroscopic quadrupole moments of the radioactive isotopes 131Cs, 132Cs, and 136Cs have been determined from the hyperfine structure of the 62P32 state by the level crossing method. The results including a Sternheimer correction are: Qs(131Cs) = ?0.625(6) b, Qs(132Cs) = +0.508(7) b, Qs(136Cs) = +0.225(10) b. The quadrupole moments of all the Cs isotopes from A = 131 to A = 137 are recalculated. It is shown, that nuclear quadrupole moments of a specific isotope obtained from different atomic P-states only agree within the limits of error after application of the Sternheimer correction. The increase of Qs with decreasing neutron number conforms with other observations and theoretical calculations stating that for elements around Z = 55 nuclear deformation develops below N = 82. The staggering of the sign of Qs may be interpreted as consequence of an oblate-prolate degeneracy of the nuclear energy surface. Some magnetic moments have been slightly improved: μI(132Cs) = 2.219(7) μN, μI(136Cs) = 3.705(15)μN (corrected for diamagnetism).  相似文献   

12.
E. Hagn  E. Zech 《Nuclear Physics A》1982,373(2):256-266
The magnetic hyperfine splitting vM=|gμNBHF/h| of 196mAu (jπ=12?; configuration ¦(π112(v132+)〉12?; T12 = 9.7 h) as dilute impurity in Ni has been determined with nuclear magnetic resonance on oriented nuclei as 96.0(2) MHz. With the known hyperfine field BHF = ?264.4(3.9) kG corrected for hyperfine anomalies the g-factor and magnetic moment of 196mAu are deduced to be |g| = 0.476(7) and |μ| = 5.72(8) μN. Taking into account the known magnetic properties of π12? and v132+ isomeric states in the neighbouring odd Pt, Au and Hg nuclei the structure of the 12? state is discussed.  相似文献   

13.
The model assumes that when two high energy particles collide each behaves as a geometrical object which has a Gaussian density and is spherically symmetric except for the Lorentz-contraction in the incident direction. Folding the two spatial distribution together we obtain the slope (b) of the elastic diffraction peak in terms of the c.m. velocities (βi and βj) and the sizes (Ai and Aj) of the two incident particles. These sizes are assumed to have the experimental s-dependence of σtotπA2 for each reaction. The combined s-dependence of the σtot's and the β's gives the s-dependence of the elastic slope bij(s) = 12(Ai2βi2 + Aj2βj2)σijtot(s)σijtot(∞). This formula agrees with the experimental slope for p-p, p-p, K+-p, K?-p and π±-p elastic scattering from 3 to 1500 GeV/c, with only 3 parameters: Aπ2 = 6.1, AK2 = 3.3 and Ap2 = 10.5 (GeV/c)?2.  相似文献   

14.
We give asymptotic forms for the high- and low-field magnetic susceptibility for the SU(3) linear dispersion Kondo model for T = 0. The ratio TKTH is also calculated for the standard SU(2j + 1) Kondo model for general j. From these results the Wilson number Wj, defined by χ0 =Wj(gμ)2j(j + 1)3kTK where χ0 is the zero-temperature zero-field susceptibility, which has been calculated by Andrei and Lowenstein for j = 12, is deduced for the SU(3) model j = 1.  相似文献   

15.
No perturbation between two valence states of NO has ever been identified, although many valence-Rydberg and several Rydberg-Rydberg perturbations have been extensively studied. The first valence-valence crossing to be experimentally documented for NO is reported here and occurs between the 15N18O B2Π (v = 18) and B2Δ (v = 1) levels. No level shifts larger than the detection limit of 0.1 cm?1 are observed at the crossings near J = 6.5 [B 2Π(F1) ~ B′ 2Δ(F2)] and J = 12.5 [B 2Π(F1) ~ B′ 2Δ(F1)]; two crossings involving higher rotational levels could not be examined. Semi-empirical calculations of spin-orbit and Coriolis perturbation matrix elements indicate that although the electronic part of the B 2Π ~ B′ 2Δ interaction is large, a small vibrational factor renders the 15N18O B (v = 18) ? B′ (v = 1) perturbation unobservable. Semi-empirical estimates are given for all perturbation matrix elements of the operators Σia?ili·si and B(L±S? ? J±L?) which connect states belonging to the configurations (σ2p)2(π2p)412p), (σ2p)(π2p)412p)2, and (σ2p)2(π2p)312p)2.  相似文献   

16.
The deep inelastic structure function D(ω, q2) is calculated in the leading log approximation for (2π22S (q02) 1n ω < 0.84 1n(1αS(q2)). For larger ω up to (2π22S) 1n ω < 0.42 α2S (q02)α2S(q2) the influence of reggeon cuts proves to slow down the growth of the structure function. A reggeon diagram technique is developed, and D is calculated up to a pre-exponent O(1), leading to D(ω, q2) ∝ q2 for (2π22S(q20) 1n ω ? 0.42 α 2S(q02)αS2(q2). By assuming the reggeon diagrams when ω is still greater, one can expect to obtain a strong coupling behaviour: D(ω, q2) ∝ q2(ln ω)η (η <2).  相似文献   

17.
It is rigorously shown that the superconducting transition temperature of any material for which the Eliashberg theory is valid must satisfy kBTc ? 0.2309 A, where A is the area under its electron-phonon spectral function α2F(ω). This relation is a least upper bound, not just an upper bound, in the sense that there is an optimal situation in which the equality holds. This occurs when the Coulomb pseudopotential parameter μ1 is zero and the spectral function is the Einstein spectrum (ω ? 1.750 A). These results are generalized in an approximate, but sufficiently accurate, way to the case μ1 ≠ 0 to obtain the more useful least upper bound kBTc ? c(μ1) A and the corresponding optimal spectrum Aδ[ω ? d(μ1)A]. Numerical results for the functions c(μ1) and d1) are presented for 0 ? μ1 ? 0.20. It is shown that the Tc's of many materials (including Nb3Sn), for which experimental values of A and μ1 are available, do not lie very far below the upper bound.  相似文献   

18.
The difference of the cross sections for deep inelastic scattering of muons with average momenta 21 GeV/c with right and left helicity at large angles, i.e., with large momentum transfer, has been measured. No statistically-significant dependence of cross sections on the longitudinal polarization of muons has been found, i.e. no parity-nonconservation effects in deep inelastic μN interaction have been observed. The magnitude of the cross-section asymmetry R = [〈σR〉 ? 〈σL〉][〈σR〉+ + 〈σL〉] may be represented as R = βQ2〉 = (? 4 ± 6) × 10?3Q2, (GeV/c)2〉. The limitations Go(μ) = (+ 6 ± 10)G have been obtained for the constant Go(μ) of vector-axial interaction (Go(μ)2) [μγα(1 + γ5)μ] Jαo (hadron, V-A).  相似文献   

19.
Hyperfine structure of the (0, 0, 1) - (1, 0, 1) transition of methanol has been investigated by beam absorption and of the (J, 1, 3?) → (J, 1, 3+) transitions for J = 2, 3, and 6 by beam-maser spectroscopy. The best-fit results for the spin-rotation and spin-spin coupling constants CJKτ±(i) and DJKτ±(i), respectively, are in kHz1: C101(1) = 2.4(10), C101(2) = ?0.6(10), D101(1) = ?13.8(9), D101(2) = 7.0(9), C213?(1) = ?5.0(10), C213?(2) = ?5.5(10) and (CJ13?(2) - CJ13+(2)) = 0.98(9).  相似文献   

20.
In the presence of neutral lepton currents, the characteristics of the reaction νμ(νμ) + Z → νμ(νμ) + μ? + μ+ + Z are modified from those expected in the conventional V-A theory. We show that in a very general class of intermediate boson theories, the modification produced can be specified entirely in terms of the cross sections for νμ(νμ) + e? → νμ(νμ) + e?. Such a constraint does not necessarily exist in models with four-fermion interaction.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号