Resin composition

The invention relates to an incombustible resin composition produced by blending a compound with a specific ester bond and imide bond in a combustible resin

1/S-expansion study of spin waves in a two-dimensional Heisenberg antiferromagnet

We study the effects of quantum fluctuations on excitation spectra in the two-dimensional Heisenberg antiferromagnet by means of the 1/S expansion. We calculate the spin-wave dispersion and the transverse dynamical structure factor up to the second order of 1/S in comparison with inelastic neutron scattering experiments. The spin-wave energy at momentum $(\pi,0)$ is found to be about 2% smaller than that at $(\pi/2,\pi/2)$ due to the second-order correction. In addition, we study the dimensional crossover from two dimensions to one dimension by weakening exchange couplings in one direction. It is found that the second-order correction becomes large with approaching the quasi-one dimensional situation and makes the spin-wave energy approach to the des Cloizeaux-Pearson boundary for $S=1/2$. The transverse dynamical structure factor is also calculated up to the second order of 1/S. It is shown that the intensity of spin-wave peak is strongly reduced while the intensity of three-spin-wave continuum becomes large and exceeds that of the spin-wave peak in the quasi-one dimensional situation.Comment: 20 pages, 6 figures, revised text, added curves in Figs. 3 and 6 for J'/J=0.075 and corrected typos in Table

Spin Excitations and Sum Rules in the Heisenberg Antiferromagnet

Various bounds for the energy of collective excitations in the Heisenberg antiferromagnet are presented and discussed using the formalism of sum rules. We show that the Feynman approximation significantly overestimates (by about 30\% in the $S={1\over2}$ square lattice) the spin velocity due to the non negligible contribution of multi magnons to the energy weighted sum rule. We also discuss a different, Goldstone type bound depending explicitly on the order parameter (staggered magnetization). This bound is shown to be proportional to the dispersion of classical spin wave theory with a q-independent normalization factor. Rigorous bounds for the excitation energies in the anisotropic Heisenberg model are also presented.Comment: 26 pages, Plain TeX including 1 PostScript figure, UTF-307-10/9

Magnetic Impurity in the two-dimensional Heisenberg Antiferromagnet

We analyze the ground state properties of the two-dimensional quantum antiferromagnet with a S=1/2 Kondo impurity. Perturbation theory around the strong Kondo coupling limit is developed and the results compared with studies, based on exact diagonalization of small clusters. We find that at intermediate coupling the impurity is partially screened and the magnetization locally suppressed. A local singlet between the impurity and the host spin is formed asymptotically.Comment: 12 REVTex pages, 4 Postscript figure

Type Reconstruction for the Linear π-Calculus with Composite and Equi-Recursive Types

We extend the linear π-calculus with composite and equi-recursive types in a way that enables the sharing of data containing linear values, provided that there is no overlapping access on such values. We show that the extended type system admits a complete type reconstruction algorithm and, as a by-product, we solve the problem of reconstruction for equi-recursive session types

A theory of the electric quadrupole contribution to resonant x-ray scattering: Application to multipole ordering phases in Ce_{1-x}La_{x}B_{6}

We study the electric quadrupole (E2) contribution to resonant x-ray scattering (RXS). Under the assumption that the rotational invariance is preserved in the Hamiltonian describing the intermediate state of scattering, we derive a useful expression for the RXS amplitude. One of the advantages the derived expression possesses is the full information of the energy dependence, lacking in all the previous studies using the fast collision approximation. The expression is also helpful to classify the spectra into multipole order parameters which are brought about. The expression is suitable to investigate the RXS spectra in the localized f electron systems. We demonstrate the usefulness of the formula by calculating the RXS spectra at the Ce L_{2,3} edges in Ce_{1-x}La_{x}B_{6} on the basis of the formula. We obtain the spectra as a function of energy in agreement with the experiment of Ce_{0.7}La_{0.3}B_{6}. Analyzing the azimuthal angle dependence, we find the sixfold symmetry in the \sigma-\sigma' channel and the threefold onein the \sigma-\pi' channel not only in the antiferrooctupole (AFO) ordering phase but also in the antiferroquadrupole (AFQ) ordering phase, which behavior depends strongly on the domain distribution. The sixfold symmetry in the AFQ phase arises from the simultaneously induced hexadecapole order. Although the AFO order is plausible for phase IV in Ce_{1-x}La_{x}B_{6}, the possibility of the AFQ order may not be ruled out on the basis of azimuthal angle dependence alone.Comment: 12 pages, 6 figure

Interaction Effect in the Kondo Energy of the Periodic Anderson-Hubbard Model

We extend the periodic Anderson model by switching on a Hubbard $U_d$ for the conduction electrons. The nearly integral valent (Kondo) limit of the Anderson--Hubbard model is studied with the Gutzwiller variational method. The new formula for the Kondo energy contains the $U_d$-dependent chemical potential of the Hubbard subsystem in the exponent, and the correlation-induced band narrowing in the prefactor. Both effects tend to suppress the Kondo scale, which can be understood to result from the blocking of hybridization (this behaviour is the opposite of that found for Kondo--Hubbard models). At half-filling, we find a Brinkman--Rice-type transition which leads from a small-gap Kondo insulator to a Mott insulator.Comment: 4 pages (ReVTeX), submitted for publicatio