Macroscopic behaviour of ferromagnets with random and statistically vanishing anisotropy

A model is defined in which the anisotropy tensor is a random function of space point characterised by its mean square value σ and a correlation lenght a_c, and the exchange density A is uniform. If the magnetic moment density is M, it is shown that two dimensionless numbers can be defined a_c/a_p, where a_p is a typical Bloch wall width$\text{(}\text{A}\text{δ}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and 4πM²/σ they define four types of macroscopic behaviour. For 4πM²/σ<1, the pole fields are a perturbation; if a_c<a_p, as in rare earth amorphous alloys, there is some frustration in the ground state and if a_p <a_c, as in inhomogeneous weak ferromagnets the magnetization direction is mainly fixed by the local anisotropy. For 4πM²/σ#62; 1, as in iron alloys, if a_p#62;a_c one has the case of soft alloys, the shape anisotropy is the dominant effect and if a_p<a_c the usual domain theory applies.     

Isospectral Mathieu–Hill Operators

In this paper we prove that the spectra of the Mathieu–Hill Operators with potentials ae^{?i2π x}  +be ^{i2π x} and ce^{?i2π x}  +de ^{i2π x} , where a, b, c and d are complex numbers, are the same if and only if ab = cd. This immediately results in a generalization of the extension of the Harrell–Avron–Simon formula.     

Study of the reaction π–<Emphasis Type="Italic">A</Emphasis> π<Superscript>+</Superscript>π<Superscript>–</Superscript>π<Superscript>–</Superscript><Emphasis Type="Italic">A</Emphasis> at large statistics with VES setup

Partial wave analysis of the π–A π⁺π^–π^– system produced by 29 GeV/cπ^– beam on a beryllium target is presented. About 30 × 10⁶ |events in the wide t′|range 0–0.8 GeV²/c ² are collected with upgraded VES setup. The size of the data sample is 2.5 times larger than one previously analyzed by VES. Data are analyzed using formalism of the density matrix with unlimited rank. We discuss status of the a ₁(1420) a ₂(1700) a ₃(1875) states and a structure of exotic ρ(770)π P-wave with J ^PC = 1^-+. Parameters of a ₃(1875) are estimated as M = 1985 ± 20 MeV/c ², Γ = 200 ± 50 MeV/c ² (preliminary).     

Intersecting veins effects of a two-dimensional photonic crystal with a large two-dimensional complete bandgap

Optimal design of a two-dimensional photonic crystal with a square lattice of dielectric rods with intersecting veins in GaAs is investigated numerically using plane wave expansion method. It is shown how a maximum complete two-dimensional bandgap is obtained by optimally connecting the dielectric rods with intersecting veins. The complete two-dimensional photonic bandgap (PBG) of our optimal design reaches Δω = 0.10664(2πc/a) (where a is the lattice constant and c is the speed of light in vacuum) when the radius of dielectric rod is 280.1 nm and the half-vein width is 60 nm. Our result shows 40% the width of PBG higher than that obtained from Ref. [M. Qiu, S. He, J. Opt. Soc. Am. B 17 (2000) 1027] (Δω = 0.0762(2πc/a)). In addition, we found that the complete bandgap can be obtained in a large range of radius R of dielectric rod when the half width of intersecting veins d is larger than 65 nm.     

Multiparticle emission in the interactions of hadrons with complex nuclei at incident momenta from 2 to 4 GeV/c

The charged secondary particles emitted in inelastic reactions of 4 GeV/cπ⁺ and π^? with the nuclei Be, Cu and Ta are thoroughly studied in their multiplicities, particle correlations and the distributions of kinematical variables, with the 1 m hydrogen bubble chamber into which the three nuclear target plates were installed. The numbers of charged secondaries emitted in the π^?(2.3 GeV/c), π⁺(2 GeV/c) and p(4 GeV/c) reactions are also investigated. From these data, characteristic features of the multiplication process of secondaries in nuclear matter are clarified. The experimental results are compared with the calculation of an intra-nuclear cascade model which takes into account the process of pion absorption by two-nucleon clusters in the nucleus. It is found that the experimental results on the properties of charged secondaries are consistently explained by the model. The model can also give an account of the experimental finding that fairly high momentum protons are emitted from the heavier nuclei into the backward hemisphere in the lab system.     

Structure in momentum-transfer for (pπ−) systems produced in diffractive dissociation of neutrons on protons

The four-momentum transfer distribution of (pπ^?) systems produced in the neutron dissociation reaction n + p → (pπ^?) + p has substantial structure which depends strongly on the mass and on the angular decay properties of the produced (pπ^?) system. No significant energy dependence is observed in the data for incident neutrons in the momentum range between 50 GeV/c and 300 GeV/c. The results are compared with a Deck-type of model.     

CO on Cu (100): Assignment of the Ols and Cls x-ray photoelectron core spectra

A theoretical explanation for the three peak structure observed in both the Cls and Ols XPS spectra of CO chemisorbed on Cu is given. It is found by the calculation of shake-up intensities, that in each case only a small number of the many possible shake-up transitions occur with any appreciable intensity. Using a Cu₅CO cluster model, we find that the chemisorption of CO on Cu splits the unoccupied 2π orbital of CO into two components, one bonding with respect to Cu (2π_b) and the other antibonding (2π_a), with the former partially occupied and the latter empty. The two shake-up satellites accompanying the main peak in each case are due to the transitions: (1) 2π_b→2π_a and (2) 1 π→2π_b and 1 π→2π_a respectively.     

Relative power loss of misalignment based on electro-optical printed circuit board

In this paper, the power loss values between 45° total internal reflecting waveguide mirror (TIRWM) and the polymer optical waveguide layer are obtained by vector finite element method. There are some misalignments during an actual fabrication of electro-optical printed circuit board (EOPCB). And, b, a, c correspond to the error value of alignment in the x-axis, y-axis and z-axis direction, respectively. Another, four effective refractive indices of the 45° TIRWM and polymer optical waveguide layer are calculated, separately. And, n_eff1 = 1.425211 is uniquely chosen. Next, these relative power errors Δ are calculated, when a, b, c separately change. Moreover, these error values are plotted into some curved surface figures. By these figures, it is easy to find the relationship between a, b, c and Δ. Furthermore, it is beneficial for us to avoid the region of larger power loss during an actual fabrication of EOPCB.     

Measurement of π−p→π0π0n at 25 GeV/c

The reaction π^?p→π⁰π⁰n has been measured with a 648 channel hodoscope spectrometer for the detection of the four γ's from the π⁰ decays. The π⁰π⁰ D-wave is fully compatible with the f⁰ contribution as it is determined in high-statistics π⁺π^? experiments. The magnitude of the π⁰π⁰ S-wave and the cosinus of its phase angle (relative to the known D-wave) are determined from fits to the π⁰π⁰ angular distributions. Argand diagrams for the I = 0 amplitude S₀ are given for the range 1000 to 1500 MeV/c². Two solutions exist. One exceeds the unitarity limit above 1200 MeV/c². The other remains within the unitarity limit and is nearly elastic up to 1450 MeV/c². It indicates an S₀ wave resonance around 1300 MeV/c².     

Investigation of the reaction π − p → η′π 0 n at the VES spectrometer

Results obtained by investigating the reaction π ^? p → η′π ⁰ n at the VES spectrometer (Institute for High Energy Physics, Protvino) are presented. The effective-mass spectrum and angular distributions of η′π ⁰ events are compared with their counterparts for ηπ ⁰ and η′π ^? events selected from the same data sample. The ratio R of the branching fractions for the decays of a ₂ ⁰ (1320) mesons into η′π and ηπ is measured. The result is R=0.047±0.018, which agrees with the value measured previously for a ₂ ^? . An investigation of P-wave production in the η′π ⁰ and ηπ ⁰ systems over the effective-mass interval 1.45–1.9 GeV/c2 leads to the conclusion that the coupling of the exotic object π ₁ (1600) to the ρπ channel is suppressed in relation to its coupling to the η′π or the b ₁(1235)π channel.     

1×4光子晶体波导分束器的特性

在完整的二维光子晶体中引入线缺陷,形成了光子晶体波导,光子晶体波导分束器是集成化光学电路的重要组成元件。我们设计了一种线缺陷1×4光子晶体分束器,并且用有限时域差分法研究了它的特性。研究表明,输出端的透射传输特性与入射光的波长和分支的几何形状有关,并且入射波分别相等地流入四个输出端口。为了减少1×4分束器在三个Y型分支区的反射,可以通过调节在分支区的可调介质柱的半径R,使每个输出端口具有很高的透射率。     

Axial-vector mesons and the problem of π<Emphasis Type="Italic">a</Emphasis><Subscript>1</Subscript> mixing

In the framework of the Nambu–Jona-Lasinio (NJL) model, a mechanism for eliminating the off-diagonal πa ₁ transitions from the effective meson Lagrangian is investigated. The problem is considered in the oneloop approximation for the quark loops. We employ the minimal superposition linear in the fields, a _μ ^' = a _μ ? c?_μπ, and show that the covariant transformation properties of both the axial-vector and vector physical fields are affected by this substitution. Contrary to some claims found in the literature, we demonstrate that the discussed change in covariant transformation properties of these fields does not result in various violations of chiral symmetry, but rather reduces to a redefinition of the S-matrix elements beyond the mass shell. At the same time, the covariant and noncovariant approaches yield identical on-shell results.     

Partial-wave analysis of the π+π+π− system through the region of the A3 meson

A recent spin-parity analysis of the π⁺π⁺π^? system formed opposite a proton and a coherent deuteron by incident 13 GeV/c²π⁺ mesons, is extended to a three-pion mass of 1.9 GeV/c. Relative proportions of the contributing partial waves are presented, from threshold, and the A₃ region is discussed in detail. Contrary to results with the (3π)^? system, a change in phase is noted for the 2^? amplitude decaying to f⁰π⁺via am S-wave.The method employs the University of Illinois three-body partial-wave-analysis program.     

Seeking and investigating isospin-two narrow dibaryon resonances in neutron-proton interactions at P n =5.20±0.13 Gev/c

The results are presented that are obtained from searches for and an investigation of isospin-two narrow resonances in the effective-mass spectrum of ppπ⁺ combinations originating from the reaction np → ppπ⁺π^?π^? induced by P _n =5.20±0.13 GeV/c neutrons. Data subjected to our analysis come from the 1-m hydrogen bubble chamber installed at the Laboratory for High Energies, Joint Institute for Nuclear Research (Dubna), and exposed to a beam of quasimonochromatic neutrons. Narrow structures in the effective-mass spectrum of ppπ⁺ combinations are found at 2175, 2221, 2321, 2398, 2471, 2525, 2596, and 2709 MeV/c ². The experimental widths of the resonances are determined primarily by the instrumental resolution. The branching fractions for various channels through which the 2596-MeV/c ² resonance decays are determined to be (83±23)% for the Δ ₃₃ ⁺⁺ p channel, (10±3)% for the (BB) ₂₀₉₅ ⁺⁺ π⁺ channel, and (7 _?7 ⁺¹⁵ for the ppπ⁺ channel; here, (BB) ₂₀₉₅ ⁺⁺ is a dibaryon in the two-proton system with a mass around 2095 MeV/c ². A qualitative analysis of the spins of the 2596-and 2709-MeV/c ² resonances is performed.     

Algebra of Regge residues and chiral symmetry

The algebraic properties of isospin T_a, axial charge X_a, and Regge residues ?, A₁, π, f are studied by means of a combination of low-energy theorems of current algebra and finite energy sum rules. The algebra of SU(2) × SU(2) × O(5) is derived. A meson saturation scheme with π, A₁, ? and σ mesons provides a representation of this algebra and gives couplings in good agreement with experiment.     

Gravitational radiation from a particle with zero orbital angular momentum plunging into a Kerr black hole

We have computed the energy ΔE, the momentum ΔP and the angular momentum ΔJ of gravitational radiation induced by a particle of mass μ and of zero orbital angular momentum plunging in the θ = π/2 plane into a Kerr black hole of mass M(?μ) and angular momentum Ma. It is found that ΔE for a = 0.99M is 4.45 × 10^-2 (μ²/M)c², which is 4.27 times larger than that for the a = 0 case.     

Coherent production of theK −π+π− system inK −d interactions at 4.5 GeV/c

After summarizing the properties of the socalled Dalitz Array (DA), which is a genuine characteristics of a resonance, we determine those of the well known ε, γ, andA ₂ resonances produced in theK ^? p→π⁺π^?π⁰ Λ final state at 4.2 Ge V/c. A tentative measurement of the DA of theA ₁ meson produced backwards in the reactionK ^? p→π⁺π⁺π^?Σ^? is also presented. The data for this analysis come from the high statistics (130 events/μb) experiment performed by the ACNO Collaboration.     

A study of final state deuteron events in 1.825 GeV/c pd interactions

The study of pd → ndπ⁺ and pd → pdπ^O reactions shows that the “slow deuteron” inelastic events are dominated by peripheral processes. Box diagrams are presented for the production mechanism of the 2.2 GeV/c² dπ enhancements. Evidence is presented that for ‘fast deuteron’ events d¹⁺⁺ and d¹⁺ resonances at 2.375 ± 0.010 GeV/c² with a width of 0.075 ± 0.015 GeV/c² are produced via baryon exchange. The elastic events have been compared with Glauber multiple scattering theory with reasonable agreement.     

Inclusive π0 and η production in the all neutral mode from 100 GeV/cπ−p collisions

Results are givenfor π⁰ and η production in 100 GeV/cπ^?p collisions, summed over all final states with no charged particles present (the all neutral final states). The data are fitted for x?0.6 to a modification of triple Regge theory suggested by the multiperipheral model. We find good agreement between the values of the ? and A₂ trajectories determined in the all neutral process, the full inclusive mode, π^?p → (π⁰, η)X, and the exclusive reactions, π^?p → (π⁰, η)n. The ? exchange residue function shows evidence for a dip at t ≈ ?0.5 (GeV/c)² (the ? wrong signature nonsense zero), whereas the η data are quite smooth in this region. These successful predictions for both the trajectory and residue function are striking evidence for the validity of triple Regge theory.