Q 2-Dependence of the Drell-Hearn-Gerasimov integral

The energy and four-momentum (Q²) dependence of the photo-absorption cross section on the proton is calculated for helicity у/2 and х/2 states. An effective Lagrangian model is used, formulated in terms of meson and baryon degrees of freedom, which obeys crossing symmetry, unitarity, Lorentz and gauge invariance. The difference in the cross sections for the two helicity states, the Drell-Hearn-Gerasimov integral I_DHG(Q²), is evaluated at different Q². We find that at small momentum transfer the absolute value of I_DHG(Q²) first increases to reach a maximum at Q² , 0.05 GeV² before decreasing at higher Q².     

Ergodic Actions of Universal Quantum Groups on Operator Algebras

We construct ergodic actions of compact quantum groups on C^*-algebras and von Neumann algebras, and exhibit phenomena of such actions that are of different nature from ergodic actions of compact groups. In particular, we construct: (1) an ergodic action of the compact quantum A_u(Q) on the type III_u Powers factor R_u for an appropriate positive Q ] GL(2, Â); (2) an ergodic action of the compact quantum group A_u(n) on the hyperfinite II₁ factor R; (3) an ergodic action of the compact quantum group A_u(Q) on the Cuntz algebra _boxclose_boxclose{\cal O}_n for each positive matrix Q ] GL(n, ³); (4) ergodic actions of compact quantum groups on their homogeneous spaces, as well as an example of a non-homogeneous classical space that admits an ergodic action of a compact quantum group.     

A scaling for the c-axis resistivity of La1.86Sr0.14CuO4 as a function of temperature, field and field orientation

The c-axis resistivity, A_c(T,rH,r/), of La_1.86 Sr_0.14CuO₄ is experimentally studied as a function of temperature T, magnetic field H and angle / between H and ab-plane. It is argued that the experimental findings cannot be accounted for by previously considered mechanisms. By contrast, they can be explained by a phenomenological model, which is developed by replacing H in the dissipation model for HÁIÁc with the reduced field h=H(sin²/+cos²//%²)^1/2, where % is the anisotropic parameter in magnetic fields. Based on this phenomenological model, it is shown that all the measured A_c(T,rH,r/) curves could consistently map onto a single curve.     

Distribution of Zeros of Random and Quantum Chaotic Sections of Positive Line Bundles

We study the limit distribution of zeros of certain sequences of holomorphic sections of high powers M^N of a positive holomorphic Hermitian line bundle L over a compact complex manifold M. Our first result concerns "random" sequences of sections. Using the natural probability measure on the space of sequences of orthonormal bases {S^N_j} of H⁰(M, L^N), we show that for almost every sequence {S^N_j}, the associated sequence of zero currents &1/NZ_S^N_j; tends to the curvature form y of L. Thus, the zeros of a sequence of sections s_N ] H⁰(M, L^N) chosen independently and at random become uniformly distributed. Our second result concerns the zeros of quantum ergodic eigenfunctions, where the relevant orthonormal bases {S^N_j} of H⁰(M, L^N) consist of eigensections of a quantum ergodic map. We show that also in this case the zeros become uniformly distributed.     

Hadronic weak decays of heavy mesons and nonfactorization

The parameters L_1,2, which measure nonfactorizable soft gluon contributions to hadronic weak decays of mesons, are updated by extracting them from the data of D,rBMPP,r VP decays (P: pseudoscalar meson, V: vector meson). It is found that L₂ ranges from т.36 to т.60 in the decays from DMK¥? to D⁺MJ?⁺,r DMK¥^*?, while it is of order 10% with a positive sign in BMNK,r D?,r D^*?,r DA decays. Therefore, the effective parameter a₂ is process dependent in charm decay, whereas it stays fairly stable in B decay. This is in accordance with the picture that nonfactorizable soft gluon effects become stronger when the relative momentum of the decay particles becomes smaller. As for D,r BMVV decays, the presence of nonfactorizable terms in general prevents a possible definition of effective a₁ and a₂. This is reinforced by the observation of a large longitudinal polarization fraction in BMNK^* decay, implying nonfactorizable effects contributing differently to S-, Pand D-wave amplitudes. We found that A^nf₁/A₁>0> A^nf₂/A₂,r V^nf/V (nf standing for nonfactorization) for BMNK^* decay and 0>A^nf₁/A₁>A^nf₂/A₂,r V^nf/V for DMK¥^*A decay. A measurement of longitudinally and transversely polarized decay rates &_L and &_T in colorsuppressed decay modes B¥⁰MD^*0A⁰, D^*0P and D⁺M JA⁺ is urged.     

Extensive Properties of the Complex Ginzburg–Landau Equation

We study the set of solutions of the complex Ginzburg-Landau equation in R^d, d <3. We consider the global attracting set (i.e., the forward map of the set of bounded initial data), and restrict it to a cube Q_L of side L. We cover this set by a (minimal) number N_QL(l) of balls of radius l in $L^infin(Q_L). We show that the Kolmogorov l-entropy per unit length, $L^infin(Q_L). We show that the Kolmogorov l-entropy per unit length, H_\epsilon =\lim_{L\to\infty} L^{-d} \logtwo N_{Q_L}(\epsilon)< /FORMULA > exists. In particular, we bound < FORMULA FORM=ÏNLINE» exists. In particular, we bound H_\epsilon< /FORMULA > by < FORMULA FORM=ÏNLINE» by \OO\bigl(\logtwo(1/\epsilon )\bigr)< /FORMULA > , which shows that the attracting set is < SMALL > smaller < /SMALL > than the set of bounded analytic functions in a strip. We finally give a positive lower bound: < FORMULA FORM=ÏNLINE», which shows that the attracting set is smaller than the set of bounded analytic functions in a strip. We finally give a positive lower bound: H_\epsilon>\OO\bigl (\logtwo(1/\epsilon)\bigr)$.     

A DYNAMICAL MODEL FOR THE GLUON DISTRIBUTION FUNCTION

In this paper the forms of the gluon distribution function at different Q² are discussed with the aid of the three-quarks model associated with dynamical calculations of QCD (the LLA approximation). The Buras-Gaemers parametrization is improved and the gluon distribution functions are obtained. It can be described by a simple parameter form: xG(x, Q²)=xG₁(x, Q²)+xG₂(x, Q²)=[1+B(s)]1(Q²)>2(1-x)^[B(s)]+[1+D(s)]2)>(1-x)^D(s), The form satisfies the QCD evolution equations and does not contradict evidently with existing experimental data. Then the properties of the constituent gluons in a nucleon are analyzed on these basis and it is indicated that the gluon distribution function could be considered as to be made of two different parts-soft and hard parts.     

The E1 and E2 capture amplitudes in 12C(α,γ0)16O

Excitation functions of the %₀ capture transition in ¹²C(!,%)¹⁶O at /_% = 90^§ were obtained using a 4 2 4' BGO crystal in close geometry (E = 0.94 to 3.39 MeV) and a 2 2 2' BGO crystal in far geometry (E = 1.69 to 3.29 MeV), where the study of the reaction was initiated in inverse kinematics involving a windowless gas target. The small crystal detected essentially the E1 multipole component in the %₀ capture transition, while the large crystal observed approximately the angle-integrated sum of the E1 and E2 multipole components. Analysis of the two data sets together with data from previous work provided strong evidence that both multipoles are of equal importance at the relevant stellar energy E₀ = 0.3 MeV.     

Lifetime measurement of the first excited state of 64Ga

The half-life of the first excited state of ⁶⁴Ga has been measured with a pulsed beam technique. The half-life was determined to be T_1/2 = 21.9 - 0.7 7s. The corresponding B(E2) = 13.6 - 0.4 e²fm⁴ shows good agreement with the Weisskopf estimate, i.e., 15.2 e²fm⁴, thereby establishing the 2⁺ assignment to this state and the single particle nature of the 42.89 keV transition.     

Self-duality in dimensions 2n>4: equivalence of various definitions and the derivation of the octonionic instanton solution

We show that the notion of strong self-duality of 2-forms in dimensions 2n, defined by the equality of the absolute values of the eigenvalues of the matrix of P with respect to an orthonormal basis (Bilge et al. 1996a), is equivalent to the self-duality in the Hodge sense of P^n/2 (used in Grossman et al. 1984) and to the equality ^*P=kP^n-1 (used in Trautman 1977). We show that the octonionic instanton solution of Grossman et al. (1984), is uniquely determined from the minimality requirement of the second Pontrjagin number p₂.     

Higher-Twist Effects on the Nucleon Spin Structure Functions in the Small Q2 Range

Based on the quark model, the Q² evolution of the nucleon spin structure functions in the small Q² region is calculated. The higher-twist effects a₂(Q²) and d₂(Q²) are investigated. Comparison with other model calculations is also proceeded.     

Photoluminescence spectra of MOCVD-grown P-doped GaAS/Alx Ga1-x As MQW

PhotoLuminescence (PL) measurement techniques have been used to investigate on MOCVD grown P-doped GaAs/Al_xGa_1mx As (x=0.3) Multiple Quantum Wells (MQW). The spectra reveal extrinsic luminescence characteristics of e-A⁰ transitions for interface and centre of well acceptors in addition to both bound and free exciton emissions.     

Angular distributions of light projectile fragments in deep inelastic Pb + Em interactions at 160 A GeV

The nuclear emulsion was exposed at CERN by the lead projectile at 160 A GeV. The angles between any pair of fragments with Z = 2-4 have been measured in the emulsion plane for the events which did not contain heavy fragments. The constant characterizing the normal angle (J) distribution of the fragment momentum projection onto the emulsion plane with respect to initial projectile momentum p₀ is found to be C_J = (0.37 - 0.02) mrad. Corresponding value C₀ = (121 - 6) MeV/c of nucleon momentum distribution in the lead nucleus coincides with that expected from Fermi momentum distribution for this nucleus. The peak in the pair-angle distribution of double-charged fragments, ⁸Be M 2!, is presented for the region of small angles (<0.1 mrad). The fraction of !-particles coming from the decay of the ground state ⁸Be is found to be (13 - 2)% of their whole number.     

Representations of Vertex Operator Algebra V L + for Rank One Lattice L

We classify the irreducible modules for the fixed point vertex operator subalgebra V_L⁺ of the vertex operator algebra V_L associated to a positive definite even lattice of rank 1 under the automorphism lifted from the у isometry of L.     

The W-boson mass and precision tests of the Standard Model

We have examined the electroweak radiative corrections in the LEP precision data in view of the new measurements of M_W and m_t as well as the recent progress in the higher order radiative corrections. From the minimal L²-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program), we predict that M_W=80.29(4)(2)rGeV where the first error is due to the uncertainty in the fitted m_t for a fixed m_H and the second error comes from the m_H in the range 60􊖸rGeV, which is to be compared with the current world average M_W=80.23(18)rGeV. The current world average value of M_W and the 1994 LEP data definitely favor nonvanishing electroweak radiative corrections and are consistent with a heavy m_t as measured by the recent CDF report but with a heavy Higgs scalar of about 400rGeV within the context of the minimal standard model. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling !_s(M_Z) and !(M_Z) are also studied carefully. In addition we discuss how the future precision measurements of M_W can provide a decisive test for the standard model with radiative corrections and give a profound implication for the measurement of t-quark and Higgs masses.     

First identification of excited states in the N = Z nucleus 70Br

Excited states in the T_z = 0 nucleus ⁷⁰Br have been investigated using the reaction ⁵⁸Ni(¹⁶O,1p3n). % rays were detected with one EUROBALL CLUSTER detector and three single HPGe detectors. Charged particles and neutrons were registered with the Rossendorf silicon ball and six modules of the EUROBALL neutron wall, respectively. The identification of % transitions in ⁷⁰Br is based on the analysis of %%-proton-neutron coincidences. A level scheme of ⁷⁰Br has been established for the first time. It shows a multiplet-like structure of probably isospin T = 0 while T = 1 isobaric analogue states are not observed.     

Gleason's Theorem for Rectangular JBW-Triples

A JBW^*-triple B is said to be rectangular if there exists a W^*-algebra A and a pair (p,q) of centrally equivalent elements of the complete orthomodular lattice P(A)\mathcal{P}(A) of projections in A such that B is isomorphic to the JBW^*-triple pAq. Any weak^*-closed injective operator space provides an example of a rectangular JBW^*-triple. The principal order ideal CP(A)_(p,q)\mathcal{C}\mathcal{P}(A)_{(p,q)} of the complete ^*-lattice CP(A)\mathcal{C}\mathcal{P}(A) of centrally equivalent pairs of projections in a W^*-algebra A, generated by (p,q), forms a complete lattice that is order isomorphic to the complete latticeI(B)\mathcal{I}(B) of weak^*-closed inner ideals in B and to the complete lattice S(B)\mathcal{S}(B) of structural projections on B. Although not itself, in general, orthomodular, CP(A)_(p,q)\mathcal{C}\mathcal{P}(A)_{(p,q)} possesses a complementation that allows for definitions of orthogonality, centre, and central orthogonality to be given. A less familiar notion in lattice theory, that is well-known in the theory of Jordan algebras and Jordan triple systems, is that of rigid collinearity of a pair (e₂,f²) and (e₂,f²) of elements of CP(A)_(p,q)\mathcal{C}\mathcal{P}(A)_{(p,q)}. This is defined and characterized in terms of properties of P(A)\mathcal{P}(A). A W^*-algebra A is sometimes thought of as providing a model for a statistical physical system. In this case B, or, equivalently, pAq, may be thought of as providing a model for a fixed sub-system of that represented by A. Therefore, CP(A)_(p,q)\mathcal{C}\mathcal{P}(A)_{(p,q)} may be considered to represent the set consisting of a particular kind of sub-system of that represented by pAq. Central orthogonality and rigid collinearity of pairs of elements of CP(A)_(p,q)\mathcal{C}\mathcal{P}(A)_{(p,q)} may be regarded as representing two different types of disjointness, the former, classical disjointness, and the latter, decoherence, of the two sub-systems. It is therefore natural to consider bounded measures m on CP(A)_(p,q)\mathcal{C}\mathcal{P}(A)_{(p,q)} that are additive on centrally orthogonal and rigidly collinear pairs of elements. Using results of J.D.M. Wright, it is shown that, provided that neither of the two hereditary sub-W^*-algebras pAp and qAq of A has a weak^*-closed ideal of Type I², such measures are precisely those that are the restrictions of bounded sesquilinear functionals {_m on pAp 2 qAq with the property that the action of the centroid Z(B) of B commutes with the adjoint operation. When B is a complex Hilbert space of dimension greater than two, this result reduces to Gleason's Theorem.     

Quantitative ferroelectric characterization of single submicron grains in Bi-layered perovskite thin films

The local polarization state and the electromechanical properties of ferroelectric thin films can be probed via the converse piezoelectric effect using scanning force microscopy (SFM) combined with a lock-in technique. This method, denominated as piezoresponse SFM, was used to characterize at the nanoscale level ferroelectric SrBi₂Ta₂O₉ and Bi₄Ti₃O₁₂ thin films, grown by pulsed laser deposition. Two types of samples were studied: polycrystalline films, with grains having random orientations, and epitaxial films, consisting of (100)_orth- or (110)_orth-oriented crystallites, 100 nm to 2 7m in lateral size, which are embedded into a (001)-oriented matrix. The ferroelectric domain structure was imaged and the piezoelectric response under different external conditions was locally measured for each type of sample. Different investigation procedures are described in order to study the ferroelectric properties via the electromechanical response. A distinct ferroelectric behavior was found for single grains of SrBi₂Ta₂O₉ as small as 200 nm in lateral size, as well as for 1.2 7m쏿 nm crystallites of Bi₄Ti₃O₁₂. By probing separately the crystallites and the matrix the investigations have demonstrated at the nanoscale level that SrBi₂Ta₂O₉ has no spontaneous polarization along its crystallographic c-axis, whereas Bi₄Ti₃O₁₂ exhibits a piezoelectric behavior along both the a- and c-directions. The electrostriction coefficients were estimated to be 3᎒^-2 m⁴/C² for polycrystalline SrBi₂Ta₂O₉ and 7.7᎒^-3 m⁴/C² for c-orientedBi₄Ti₃O₁₂. Quantitative measurements at the nanoscale level, within the experimental errors give the same values for remanent polarization and coercive field as macroscopic ferroelectric measurements performed on the same samples.     

Trace Construction of a Basis for the Solution Space¶of sl N qKZ Equation

The trace of intertwining operators over the level one irreducible highest weight modules of the quantum affine algebra of type A_Nу⁽¹⁾ is studied. It is proved that the trace function gives a basis of the solution space of the qKZ equation at a generic level. The highest-highest matrix elements of the composition of intertwining operators are explicitly determined as rational functions up to an overall scalar function. The integral formula for the trace is presented.     

Influence of the substrate voltage on the random telegraph signal parameters in submicron n-channel metal-oxide-semiconductor field-effect transistors under a constant inversion charge density

In this paper, the impact of the substrate bias U_BS on the parameters of a repulsive random telegraph signal in an n-channel metal-oxide-semiconductor field-effect transistor is studied. Particular attention is paid to the variation of the capture time constant F_c with the channel current I in linear operation. It is shown that the strong reduction of F_c with I can be explained by the Coulomb blockade effect. The corresponding Coulomb energy (E of the charged-near-interface oxide trap is shown to be a strong function of the substrate bias. From the analysis of the experimental results considering surface quantization effects follows that the variation of (E with U_BS is caused by the change in both the inversion layer surface charge density N_s and in the surface electric field F_s that influences the distance between the centroid of the inversion layer and the interface. In fact, it will be demonstrated that (E can be expressed in function of a single parameter (N_sF_s²). Finally, the impact of the substrate bias on the other parameters, i.e., the amplitude (I, the emission time constant F_e and the distance d of the trap from the interface, will also be addressed.