New compounds in the Mn-X-Bi system where X = Ni, Cu, RhorPd

A new class of magnetic compounds has been discovered in the temary system Mn-X-Bi where X is Ni, Cu, Rh or Pd. The approximate compositions of these compounds are Mn₅Ni₂Bi₄, Mn₃Cu₄Bi₄, Mn₅Rh₂Bi₄, and Mn₅Pd₂Bi₄. The Bravais lattice is face-centered cubic, and the lattice constants are 12.16 Å (X = Ni), 12.18 Å (X = Cu), 12.31 Å (X = Rh) and 12.44 Å (X = Pd). These compounds are probably ferromagnetic and have Curie temperatures in the range -7°C to 183°C. A crystal structure is proposed for these compounds which contains 88 atoms/unit cell.     

A universal covering group of SU(p, q)

A universal covering group of SU(p, q) is parametrized and its groups law in this parametrization is established.     

Factorizable Z(N) models

The factorizable S-matrix with Z(N) symmetry is constructed. It is speculated that the field theory belonging to this S-matrix matrix is related to the scaling limit of Z(N) generalizations of the Ising model.     

Thermoelectric power of quasi-one-dimensional Nb3X4 with X=S, Se andTe

The thermoelectric power of linear chain synthetic metals Nb₃X₄ (with X=S, Se and Te) was measured from 5 to 300 K. The thermopower is negative indicating a dominant transport by electrons. Common to three compounds, in lower temperature regions the thermopower rises linearly with temperature but soon saturates. With respect to Nb₃S₄ and Nb₃Se₄ we have found no special anomaly of the thermopower except for a little higher magnitude.With respect to Nb₃Te₄ anomalies in the thermopower vs temperature appear at about 80 and 20 K which are explained in terms of the charge- density-wave phase transition from the simultaneous measurement of the resistivity and the observation of the electron diffraction patterns.     

Nonadiabatic effects in the B, C, B′, and D states of H2

The Kolos-Wolniewicz potentials for the H₂$\text{B}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and C¹Π_u states were used together with the hypothesis of pure precession for the rotation-electronic interaction, to calculate the nonadiabatic energy levels of these states for J = 1 to 5. The complete coupling matrix was computed using accurate numerical vibrational wavefunctions. The calculated Λ-doubling of the v = 0 to 12 C vibrational levels generally agrees well with experimental values, and the nonadiabatic shifts in the B rotational constants qualitatively explain the difference between the theoretical and RKR potentials for this state.The interaction of the B′${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and D¹Π_u states was also investigated, but only qualitatively since adiabatic potentials of sufficient accuracy do not exist for these states. The Λ-doubling of the Dv = 0 rotational levels agrees well with the experimental values. An appreciable “background” nonadiabatic shift in the B′ rotational constants was found. This shift, which is nearly 5 percent of B_v, is in addition to that of strong local two-level interactions and was not “deperturbed” in constructing the B′ RKR potential. The result is that the RKR turning points differ by about 0.04 au from the “true” adiabatic turning points. This conclusion is supported by a Hartree-Fock calculation of the B′ potential to the left of R_e.     

The magnetic properties of some R5Pt3 compounds (R = Gd, Tb, Dy, Ho)

The magnetic susceptibility and magnetization of the R₅Pt₃ intermetallic compounds have been studied. Gd₅Pt₃ is ferromagnetic while Tb₅Pt₃, Dy₅Pt₃ and Ho₅Pt₃ possess rather a non-linear magnetic structure, with strong ferromagnetic interaction and high anisotropy effects at low temperatures.     

Preparation and semiconductive properties of rock salt type solid solution systems,Cd1−xMxS (M = Sr, Ca, Mg, Pb, Sn)

Measurements have been made of the semiconductive properties of rock salt type solid solution systems, Cd_1?xM_xS (M = Sr, Ca, Mg, Pb, Sn) synthezised at high pressures. The Cd_1?xCa_xS system has a high electrical resistivity of more than 3 × 10¹⁰Ω-cm, and a band gap estimated from its optical absorption edge which varies from 1.9–2.6 eV with Cd_1?xPb_xS system is between 1 and 10Ω-cm, and decreases with increase in the substitution ratio. This system is photoconductive, similar to the normal pressure phase of CdS, and the photoconductivity peak shifts from 0.75–0.96μm with increase in the substitution ratio from 0.1–0.5. The above results are extrapolated to pure CdS and give for CdS having a rock salt type structure high resistivity, photoconductivity, and a band gap of 1.7–1.8 eV at room temperature and normal pressure.     

A theory of the J/gY→η(η′)γ decays

It is argued that the $\text{J}\text{gY}\text{→η(η′)γ}$ decay rates are directly calculable within quantum chromodynamics. The calculation of $\text{Γ(}\text{J}\text{Ψ}\text{→ηγ)}$ is most straightforward and involves no new hypotheses as compared to, say, the $\text{J}\text{Ψ}\text{→}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}$ decay in detail earlier. To the contrary, evaluation of the $\text{J}\text{Ψ}\text{→η′γ}$ width puts on trial dynamical results concerning the η′ coupling to gluons. The latter depends crucially on non-perturbative power terms in the QCD sum rules. The calculated numbers for $\text{Γ(}\text{J}\text{Ψ}\text{→ηγ)}$ and $\text{Γ(}\text{J}\text{Ψ}\text{→η′γ)}$ agree well with the data.     

A new parametrization for the N/D method

A new treatment of the left-hand cut for N/D problems is presented whereby, instead of poles, the cut is parametrized by a Legendre expansion which fixes the discontinuity. The method is tested through the use of analytic forms, and is found to work very well in a wide variety of circumstances. An extension is made to situations where there are errors in the input, and resulting problems are discussed. The method is applied to elastic pion-pion scattering. Both the rho and f₀ mesons are produced dynamically, but trouble is encountered for the s-waves. The relation of this trouble to ambiguities found in other s-wave calculations is discussed.     

Transition Probabilities in the BΣ-XΣ and the BΣ-AΠ Electronic Systems of MgO

Transition probabilities for the B¹Σ⁺-X¹Σ⁺ and the B¹Σ⁺-A¹Π electronic systems are presented for v=0-4 and J=0-150 in each electronic state. The functional form of the electronic transition moment for the B-X transition is taken from published ab initio results. The B-A moment is assumed to have the same form and is scaled using empirical branching ratio data. The R_e(r) are used with Rydberg-Klein-Rees (RKR) wavefunctions to calculate transition probabilities for v=0-4 and J=0-150. The RKR potentials were calculated based on empirical spectroscopic constants.     

The inverse problem for the third order equation uxxx + q(x)ux + r(x)u = −iζ3u

The spectral problem u_xxx + q(x)u_x + r(x)u = ?iξ³u is considered. A set of spectral data which is sufficient for the reconstruction of the potentials q(x) and r(x) is found and the problem of this reconstruction, this inverse problem solved.     

N Law for bosons in 2D

A rigorous upper bound is derived for the exact ground-state energy of N negative charged bosons and N motionless, i.e. fixed, positive charges with Coulomb interactions in 2D for arbitrary N ? 4 giving rise to an N²-upper bound. The consistency of such an N² behaviour is also investigated by examining a lower bound to the ground-state energy.     

t/s scaling in exclusive and inclusive proton reactions

A model is developed in order to account for the previously observed large-angle behaviour in elastic scattering, and to predict the analogous inclusive effects. Data of (pp, p) distributions and pp → pN^* reactions are examined in regions of high transverse momenta and fitted by the functional forms of the model. The fits show the expected features of this new type of high-energy scaling.     

Description of spin reorientation transition in Au/Co/Au sandwich with Co film thickness within a simple phenomenological model of ferromagnetic film

Simple phenomenological model of ferromagnetic film characterized by equal energies of surface anisotropies at two sides of a film (symmetric film) is considered. The model is used to describe a two-step spin reorientation transition (SRT) in Au/Co/Au sandwich with Co film thickness: the SRT from perpendicular to canted noncollinear (CNC) state at N_⊥=6.3 atomic layers and the subsequent SRT from CNC to in-plane state at _N∥=10.05$N_{\parallel }=10.05$ atomic layers. Analytic expressions for the stability criterion of collinear perpendicular and in-plane states of a film are derived with account of discrete location of atomic layers. The dependence of borders that separate regions corresponding to various magnetic states of a film in the (k_B,k_S)-diagram on film thickness N is established. k_S(k_B) is surface (bulk) reduced anisotropy constant. The comparison of theory with experiment related to Au/Co/Au sandwich shows that there is a whole region in the (k_B,k_S)-diagram corresponding to experimentally determined values of threshold film thicknesses N_⊥=6.3 and _N∥=10.05$N_{\parallel }=10.05$. The comparison of this region with similar region determined earlier for a bare Co/Au film within the same model of asymmetric film and characterized by N_⊥=3.5, _N∥=5.5$N_{\parallel }=5.5$ shows that the intersection of these regions is not empty. Hence, both the SRT in Au/Co/Au sandwich and in bare Co/Au film with Co film thickness can be described within the same model using the same magnitudes of model parameters k_S, k_B. Based on this result we conclude that the energy of Neel surface anisotropy at free Co surface is negligible compared to the energy of Co–Au interface anisotropy. It is demonstrated that the destabilization of collinear states in symmetric film leads to occurrence of the ground CNC state and two novel metastable CNC states. These three CNC states exhibit different kinds of symmetry. In case of asymmetric film only ground CNC state occurs on destabilization of collinear states of a film.     

An inequality for spin-s XY ferromagnets

It is proved that correlation functions for a general spin $\text{1}\text{2}\text{XY}$ ferromagnet are bounded above by correlation functions for a corresponding Ising ferromagnet.     

B−L non-conserving proton decay in guts

It is shown that B?L non-conserving proton decay (p→e^?π⁺π⁺ etc.) is allowed through gauge boson mixing in both SO(10) and E(6) GUTs, but not in the SU(5) GUT. The lifetime for this decay mode is estimated.     

Force field of A(I)B(III)−S2 chalcopyrite compounds at zero wave vector

Published experimental frequencies are used to calculate Urey-Bradley force fields and ionic charges of some ABS₂ chalcopyrite compounds. The values obtained for the A?S and B?S force constants as well as the ionic charges are discussed.     

On the Q(M) depolarization metric

In this work, we have derived a depolarization metric, named Q(M) here, from the nine bilinear constraints between the 16 Mueller-Jones matrix elements, reported previously by several authors following different approaches. This metric Q(M) is sensitive to the internal nature of the depolarization Mueller matrix and does not depend on the incident Stokes vector. Q(M) provides explicit information about the inner 3 × 3 internal matrix. Four bounds are associated to Q(M) for a totally depolarizing, partially depolarizing, non-depolarizing diattenuating or partially depolarizing, and non-depolarizing non-diattenuating optical system, respectively. To our best knowledge, Q(M) is the unique depolarization metric that provides such information in one single number.