Showing papers on "Spin-½ published in 1977"
Book•
27 May 1977
TL;DR: The theory of the complex angular momentum plane (Regge theory) as discussed by the authors was proposed by Regge in the early 1970s to explain the forces between these particles and predict the results of high-energy scattering experiments.
Abstract: Originally published in 1977, this book presents an extended introduction to the theory of hadrons, the elementary particles which occur in the atomic nucleus The main emphasis is on the theory of the complex angular momentum plane 'Regge theory', which has grown from Regge's demonstration in 1959 that it is useful to regard angular momentum as a complex variable when discussing solutions of the Schrodinger equation for non-relativistic potential scattering This theory helps to classify the many different particles which have been discovered in recent years, to explain the forces between these particles and to predict the results of high-energy scattering experiments Regge theory thus serves as a unifying concept drawing together many different features of high-energy physics This monograph is intended primarily for research students just beginning to concern themselves with particle physics, but more experienced workers will also find much to interest them in this detailed survey of the basic ideas and results of Regge theory
1,024 citations
Proceedings Article•
22 Aug 1977TL;DR: In this article, the authors propose a method to solve the problem of "anymore": anymore.anymore, anymore, ANY MORE, any more, etc., etc.
Abstract: ANY MORE.
356 citations
TL;DR: In this article, an alternative definition of single transition operators is given for the description of selective excitation and detection experiments in multilevel spin systems, which has the virtues of a simple physical interpretation and easy application to arbitrarily complicated systems.
Abstract: An alternative definition of single transition operators is given for the description of selective excitation and detection experiments in multilevel spin systems. This definition has the virtues of a simple physical interpretation and easy application to arbitrarily complicated systems. Some applications to the excitation and detection of multiple quantum transitions in spin 1 and spin 3/2 systems as well as in coupled spin systems are described.
352 citations
TL;DR: In this article, the ground state energy and momentum distribution of the electrons are expanded from the atomic limit for the half-filled Hubbard model by using the spin correlation functions of the spin 1/2 Heisenberg model.
Abstract: The ground-state energy E and momentum distribution nk of the electrons are expanded from the atomic limit for the half-filled Hubbard model. The coefficients of expansion are represented by the spin correlation functions of the spin 1/2 Heisenberg model. Using the spin-wave theory, approximate values of coefficients are calculated for the square lattice and the simple cubic lattice. In one dimension, the theory shows a good agreement with the exact solution. An effective spin Hamiltonian for the half-filled Hubbard model with arbitrary hopping integrals is obtained up to the fifth order. It is shown that the fourth term contains four spin interactions.
319 citations
TL;DR: In this paper, the decay of a spin 1 2 leptons was studied in a manner which is applicable to a large class of models, assuming that the decay process is induced by one loop diagram.
297 citations
TL;DR: In this paper, the properties of magnetic systems with competing ferromagnetic and antiferromagnetic inter-actions are investigated and a few exact results are obtained; the possibility of exact solutions comes from the fact that the distribution of ferro-and antiferromeagnetic bonds is assumed to obey certain rules, instead of being completely random.
Abstract: Magnetic systems with competing ferromagnetic and antiferromagnetic inter- actions are investigated and a few exact results are obtained. The possibility of exact solutions comes from the fact that the distribution of ferro- and antiferromagnetic bonds is assumed to obey certain rules, instead of being completely random. The ground state, however, has the character of a spin glass. Two of our models have the property that they have no phase transi- tion in the case of one-dimensional (Ising) spins, whereas there is a phase transition for two- dimensional (XY) spins. The phase transition disappears again for high values of the spin dimensionality n. In a particular case of a three-dimensional. X Y model, the susceptibility has been calculated at high and IOW temperatures; it has a maximum at some temperature, but a speculative argument is given that there is actually no kink.
294 citations
TL;DR: The physical and mathematical formulation of the two-fraction fast exchange model is investigated in this article, where a region R containing spins within which these spins migrate via diffusion and also decay (flip) is considered.
251 citations
TL;DR: In this paper, the hydrodynamic theory of spin waves is extended to a magnetic system such as a spin glass or a crystal with helical spin order, in which there are equilibrium magnetizations on different sites, with spin directions that are not collinear.
Abstract: The hydrodynamic theory of spin waves is extended to a magnetic system such as a spin glass or a crystal with helical spin order, in which there are equilibrium magnetizations on different sites, with spin directions that are not collinear. If the total magnetization is zero and if the interactions are assumed to be isotropic in spin space, one predicts well-defined spin waves at small wave vectors $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$, with a linear dispersion relation, and three polarizations for each value of $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$. The hydrodynamic assumption of a finite spin-stiffness constant may be questionable, however, for the spin glass. Nonzero magnetization is discussed briefly.
169 citations
TL;DR: In this article, the frequency dependance of the proton spin-lattice relaxation time T1 at several temperatures and pressures in TTF-TCNQ(D4) and TTF(D 4)-TCNsQ was analyzed.
Abstract: This paper presents the frequency dependance of the proton spin-lattice relaxation time T1 at several temperatures and pressures in TTF-TCNQ(D4) and TTF(D4)-TCNQ. It is shown that only backward (q = 2 kF) and forward (q = 0) scatterings contribute to the nuclear relaxation induced by the modulation of the hyperfine field in these one-dimensional conductors. At medium fields, H 0 ~ 30 kOe, the frequency dependence of T1 originates from the diffuse character of the spin density wave excitations around q = 0, leading to T1-1 αH0- 1/2 . The enhancement of T1 -1, is at low fields, limited by the existence of a finite interchain coupling (tunnelling type). We find, within a RPA analysis, close correlations between the pressure and temperature dependences of the spin excitations diffusion constant and the collision time derived from the longitudinal conductivity. The interpretation of the NMR data in terms of a Hubbard model excludes both big U and small U pictures. However, we point out the importance of the electron-electron interactions on the relaxation rate of TTF-TCNQ. We derive a ratio U/4 t II ~ 0.9 for the TCNQ chain. We also assume that besides charge density waves fluctuations existing between 300 K and the phase transition at 53 K, electron-electron interactions make an important contribution to the temperature dependence of the spin susceptibility. Finally, we give a unified description of quasi one dimensional conductors in which the various systems are classified according to the transverse tunnelling coupling and the electron lifetime. It follows from this description that for TTF-TCNQ and its derivatives, transverse couplings (tunnelling and Coulomb) are large enough to justify the use of a mean-field theory.
163 citations
TL;DR: In this paper, momentum-shell recursion relations for classical fixed-length spins in 2 + ε 2 + √ √ ε ϵ 2 dimensions were constructed.
Abstract: We describe in detail how to construct momentum-shell recursion relations for classical fixed-length spins in $d=2+\ensuremath{\epsilon}$ dimensions. The theory is then applied to anisotropic spin systems and to a model of nematic liquid crystals. We also develop a trajectory-integral formalism, which is used to produce the free energy, magnetization, and susceptibilities of isotropic spin systems to first order in $\ensuremath{\epsilon}=d\ensuremath{-}2$.
163 citations
TL;DR: In this paper, the authors showed that the contribution from P-wave charmed mesons can be suppressed either by phase space or by the nodes if their masses lie within a certain range.
Abstract: An extension of the locally supersymmetric theory of the spin- (2,3/2) gravitational multiplet and the spin- (1,1/2) Abelian gauge multiplet is obtained in which the spin-1 field becomes an axial-gauge field coupled to both the spin-3/2 and spin-1/2 fields.
TL;DR: In this paper, the authors provided the space of distributions solutions of the mass 0, spin s equations with a Hilbert space structure H s, such that the representation U s, will act unitarily on H s.
TL;DR: In this article, the utility of cluster expansion of the wave function was discussed and a pseudo-orbital theory was proposed, which constitutes a generalization of the orbital-theoretic idea.
TL;DR: In this paper, the spin-dependent parameter G'0, the coefficient of σ1·σ2τ1·τ2 δ(r1−r2) in the Fermi-liquid interaction, and to the tensor invariants, are related back to elementary-particle exchange.
TL;DR: In this article, the analytical properties of spin-weighted angular spheroidal functions introduced by Teukolsky are investigated by means of a series involving Jacobi polynomials.
Abstract: The analytic properties of the spin‐weighted angular spheroidal functions introduced by Teukolsky are investigated by means of a series involving Jacobi polynomials. This approach facilitates the numerical determination of eigenvalues, particularly in the case of complex frequencies.
TL;DR: In this paper, the time independent diagrammatic technique based on the mathematical methods of quantum electrodynamics (second quantization, Wick's theorem, Feynman-like diagrams) is combined with graphical techniques of spin algebras to derive general expressions for the matrix elements of spin independent one-and two-particle operators between spin symmetry adapted ground, mono-and bi-excited configurations of a closed shell system.
Abstract: The time independent diagrammatic technique based on the mathematical methods of quantum electrodynamics (second quantization, Wick's theorem, Feynman-like diagrams) is combined with graphical techniques of spin algebras to derive general expressions for the matrix elements of spin independent one- and two-particle operators between spin symmetry adapted ground, mono- and bi-excited configurations of a closed shell system. Two coupling schemes are considered for bi-excited states and their relative merits are discussed. Finally, the results are used to derive compact expressions for the coupling coefficients of the direct configuration interaction from molecular integrals (CIMI) method.
TL;DR: In this article, the dynamics of the spin orientation, including relaxation, were studied in a two-fluid model, in which the changes in macroscopic physical quantities arising from variation of the Cooper-pair wavefunction are associated with the superfluid component, while those arising from changes in the statistical occupation factors are attributed to the normal components.
TL;DR: The power of the Young tableau scheme for labeling a complete spin-adapted basis set in the theory of complex spectra lies in one's ability to evaluate matrix elements of irreducible tensor operators directly in terms of the tableau labels and shapes.
Abstract: The power of the Young tableau scheme for labeling a complete spin-adapted basis set in the theory of complex spectra lies in one's ability to evaluate matrix elements of irreducible tensor operators directly in terms of the tableau labels and shapes. We show that the matrix-element rules stated by Harter for one-body operators can be easily derived from simple vector-coupling considerations. The graphical method of angular momentum analysis is used to derive closed-form expressions for the matrix elements of two-body operators. This study yields several interesting new relationships between spin-dependent operators and purely orbital operators.
TL;DR: In this article, the quantum chromodynamics with massless quarks and an infinite number of colors is represented as a theory of the noninteracting mesons which lie on rising Regge trajectories.
TL;DR: In this paper, the distance between the spins of the radical and the other paramagnetic centre (PC) can be determined from the change of the transverse-and especially from the longitudinal relaxation times of theradical due to the dipole-dipole interaction between the radical, and the PC.
TL;DR: In this paper, the causal properties of higher-spin spin equations were analyzed in 2(2J + 1)-component Schroedinger form, where the coefficients of all the space derivatives depend on the external field.
Abstract: The two-component Sakata-Taketani (ST) spin-0 theory and the single-component Klein-Gordon theory are obtained from the five-component Duffin-Kemmer-Petiau (DKP) theory with six types of external field interactions by means of a Peirce decomposition. Whereas the DKP equation manifests the covariance, the ST equation manifests the causal properties. In particular, the presence of noncausal wave propagation when there is coupling to a second-rank tensor field is apparent from the form of the ST equation, in which the coefficients of all the space derivatives depend on the external field. The results indicate that the causal properties of higher-spin equations should also be obvious when they are expressed in 2(2J + 1)-component Schroedinger form
TL;DR: In this paper, the authors describe the use of nuclear magnetic relaxation in strongly coupled spin systems for determining all three rotational diffusion constants of rigid, planar molecules with C2v symmetry.
Abstract: In this paper we describe the use of nuclear magnetic relaxation in strongly coupled spin systems for determining all three rotational diffusion constants of rigid, planar molecules with C2v symmetry. The complete evaluation of the motional parameters rests on the accurate measurement of the cross‐correlation terms relating the reorientation of two proton–proton internuclear vectors. This term, as well as more familiar auto correlation terms, may be extracted from an analysis of the recovery of individual lines in the strongly coupled proton spin system following a nonselective 180° pulse. The principles, procedure, and practical considerations of this approach to studies of anisotropic motion are illustrated for the AB2 spin systems of 1,2,3‐trichlorobenzene, 2,6‐dichloroanisole, and 2,6‐dichlorophenol‐0‐d.
TL;DR: In this paper, a program of rewriting field theories in terms of particle-string variables is described, and a functional bridge from quantum chromodynamics to the Bardeen-Bars-Hanson-Peccei string is presented.
Abstract: Essential tools are provided for a program of rewriting field theories in terms of particle-string variables. The general methods are illustrated in the case of quantum chromodynamics: (1) One finds the particle-trajectoy representation for the quark Green's functional. (2) One derives directly correct end-point terms for quarks at the ends of strings. (1) and (2) are for any number of dimensions. (3) In two dimensions, one finds a functional bridge from quantum chromodynamics to the Bardeen-Bars-Hanson-Peccei string.
TL;DR: Small polymer beads with graduated pore sizes are used to show that collisional broadening has a marked dependence on the long-range structure of the diffusion environment.
TL;DR: In this paper, it was shown that if massless fermions of spin 3 2 have non-vanishing low-energy couplings, then all particles to which the couplings couple must display supersymmetry.
TL;DR: The spin state of camphor-bound cytochrome P-450 is shown to depend largely on medium and temperature in aqueous as well as in mixed organic buffer as discussed by the authors.
Abstract: The spin state of camphor-bound cytochrome P-450 is shown to depend largely on medium and temperature in aqueous as well as in mixed organic buffer. At sub-zero temperatures a variation of paH, ionic strength or camphor concentration modifies the spin equilibrium from nearly pure high-spin form to nearly pure low-spin form. Since the apparent pKa of transition is a linear function of log I, the spin state seems to be controlled by the electrostatic potential in the heme proximity. K+ is found to have a specific effect on the spin state.
The change of enthalpy, ΔH values, of the spin transition depends on the same parameters as the equilibrium constant, in the organic cosolvent as well as in aqueous buffer. As the cosolvent effect is reflected by higher ΔH values, and KCI and pH tend to lower ΔH, the cosolvent effect can easily be compensated. Therefore kinetic studies of the spin conversion might well be undertaken at sub-zero temperature in this solvent.
TL;DR: In this paper, core polarisation calculations taken beyond first order perturbation theory provide a mechanism to explain the breakdown in the additivity rule for magnetic moments in high spin isomers of configuration.