Nonperturbative model of hot <Emphasis Type="Italic">SU</Emphasis>(2) gluodynamics

A hot-gluodynamics model based on taking consistently into account nonperturbative fluctuations of the gluon field in the temperature-deconfining phase is proposed. In order to perform averaging over nonperturbative fields, the gluon system (partition function) is broken down into a fast and a slow subsystem. In one of these subsystems, nonperturbative fields play the role of rapidly changing (stochastic) degrees of freedom, whose effect on soft gluons is considered within the cluster-expansion method for Green’s functions in the nonperturbative background field. The effect of long-wavelength chromomagnetic fluctuations on hard gluons is studied within adiabatic perturbation theory in the strong-field approximation. The pressure and the energy density of SU(2) gluon matter are calculated for T > T _c .     

Method of vacuum correlation functions: Results and prospects

Basic results obtained within the QCD method of vacuum correlation functions over the past 20 years in the context of investigations into strong-interaction physics at the Institute of Theoretical and Experimental Physics (ITEP, Moscow) are formulated Emphasis is placed primarily on the prospects of the general theory developed within QCD by employing both nonperturbative and perturbative methods. On the basis of ab initio arguments, it is shown that the lowest two field correlation functions play a dominant role in QCD dynamics. A quantitative theory of confinement and deconfinement, as well as of the spectra of light and heavy quarkonia, glueballs, and hybrids, is given in terms of these two correlation functions. Perturbation theory in a nonperturbative vacuum (background perturbation theory) plays a significant role, not possessing drawbacks of conventional perturbation theory and leading to the infrared freezing of the coupling constant α _s.     

Nonperturbative equation of state of quark-gluon plasma: Applications

The vacuum-driven nonperturbative factors L_i for quark and gluon Green’s functions are shown to define the nonperturbative dynamics of QGP in the leading approximation. EoS obtained recently in the framework of this approach is compared in detail with known lattice data for μ = 0 including P/T⁴, ε/T⁴, . The basic role in the dynamics at T ? 3T_c is played by the factors L_i which are approximately equal to the modulus of Polyakov line for quark L_fund and gluon L_adj. The properties of L_i are derived from field correlators and compared to lattice data, in particular the Casimir scaling property follows in the Gaussian approximation valid for small vacuum correlation lengths. Resulting curves for P/T⁴, ε/T⁴, are in a reasonable agreement with lattice data, the remaining difference points out to an effective attraction among QGP constituents.     

Investigation of the semileptonic weak decays of B (s) to S (Scalar Meson) via light-cone QCD sum rules

In this paper, the semileptonic weak decay process of B _(s) → S scalar mesons is investigated by using the light-cone QCD sum rules (LCSR) in the nonperturbative part. The corresponding transition matrix elements leading to form factors and the branching ratio of this process are determined.     

The energy spectral analysis of the strong-coupled superlattice

We study the energy spectrum of the strong-coupled superlattice. The barriers affect the energy spectral statistics in a small scale. The nearest-neighbor energy-level distribution P(s) and the spectral rigidity Δ₃(L) demonstrated the GOE (Gaussian Orthogonal Ensemble) distribution. In the whole scale, with the electric field increasing, the spectral rigidity Δ₃(L) changes from the Poisson-type like distribution to the Wigner-type like distribution due to the change of the energy-level long-correlation, while the P(s) indicates that the system demonstrates to be integrable. The near-degeneracy of levels makes the level statistics complex.     

3D and 1D micromagnetic calculation for hard/soft bilayers with in-plane easy axes

Macroscopic hysteresis loops and microscopic magnetic moment distributions have been determined by three-dimensional (3D) as well as one-dimensional (1D) micromagnetic models for exchange-coupled Nd₂Fe₁₄B/α–Fe bilayers and carefully compared with each other. It is found that the results obtained from the two methods are consistent with each other, where the nucleation and coercive fields decrease monotonically as the soft layer thickness L^s increases whilst the largest maximum energy products (roughly 600 kJ/m³) occur at L^s=5 nm. Moreover, the calculated angular distributions in the thickness direction for the magnetic moments are similar. Nevertheless, the calculated critical fields and energy products by 3D OOMMF are systematically smaller than those given by the 1D model, mainly due to the local demagnetization fields, which are taken into account in the 3D calculation and ignored in the 1D calculation. It is demonstrated by the 3D calculation that the large demagnetization fields in the corners of the soft layers reduce the nucleation fields and thus facilitate the magnetic reversal. Such an effect enhances as L^s increases. When L^s=20 nm, the differences between the coercivity is as large as 30%, while the nucleation fields obtained by the two methods have opposite signs.     

Perturbative expansions in QCD and analytic properties of α s

It is shown that analytic properties of standard QCD perturbation theory contradict known spectral properties and contain, in particular, infrared-generated Landau ghost poles and cuts. As an outcome, a rigorous background perturbation theory is developed and its analytic properties are shown to be in agreement with general requirements. In the limiting case of large N _c, where QCD amplitudes contain only pole singularities, the strong coupling constant α _s(Q ²) is shown to be a meromorphic function of external momenta as well. Some simple models and examples are given where nonperturbative β function and α _s(Q ²) can be written explicitly. The general form of amplitudes at large N _c is given in the framework of background perturbation theory, and its correspondence with standard perturbation theory at highmomenta is demonstrated in the example of e ⁺ e ^? annihilation. For timelike momenta, the background coupling constant differs drastically from the standard one, but the background series averaged over energy intervals has the same (AF) behavior at high momenta in the Euclidean and in the Minkowskian region.     

Crosstalk in double-pumped fiber optic parametric amplifiers for wavelength division multiplexing systems

We study experimentally inter-channel crosstalk in double-pumped fiber optic parametric amplifiers constructed with conventional dispersion shifted fibers (DSFs) having different lengths (L_A = 13.8, L_B = 6.8, L_C = 4.3, and L_D = 0.8 km). For long fibers (L_A and L_B), eye diagram measurements in a 5-channel (100 GHz spacing) system show that in order to have negligible crosstalk, the output signal power per channel, P_s, should be limited to P_s < 0 dBm. By decreasing the fiber length (to L_C) it is possible to increase the output signal power and/or the number of signals while keeping the crosstalk on negligible levels. This trend was further confirmed by using a very short DSF (L_D = 0.8 km).Finally, we experimentally demonstrate that a general trend in 2P-FOPAs is that spurious FWM increases with the number of signal channels up to a given number of channels when a saturation regime is reached. This saturation of the generation of spurious tones occurs when the bandwidth occupied by the signals exceeds ∼4-5 nm.     

Stark interaction in then s n p z 3 P 1 levels of zinc and cadmium

The tensor polarizabilities of then s n p z ³ P ₁ levels of Zn and Cd were measured using optical double resonance. From the rf-resonance signals in parallel electric and magnetic fields, the following tensor polarizabilities were deduced: Zn,α _ten(4s4pz ³ P ₁)=1.83(8) kHz/(kV/cm)²; Cd,α _ten(5s5pz ³ P ₁)=1.77(8) kHz/(kV/cm)². Theoretical values were calculated using Coulomb approximation. The results were then compared with previous theoretical and experimental values and, in addition, with values for Hg. Theoretical results obtained by a modified Sternheimer method (E.J. Robinson: J. Opt. Soc. Am.59, 782 (1969)) are in better agreement with the experimental values than the results of the Coulomb approximation calculations.     

Symmetries and the mass ratio of the electron and muon

A model of symmetries and gauge interactions relating the electron and muon is considered. The model is based on the U_L(1)?U_R(1)?R_L?R_R group where U_L(1)?U_R(1) denotes the chiral e-μ rotation and R_L?R_R the chiral reflection of the electron field. The invariance under this group is spontaneously broken by the vacuum expectation values of scalar fields. A zeroth-order vacuum is found for which the zeroth-order electron mass vanishes, while one-loop corrections lead to a finite $\text{m}{}_{\mathrm{<mtext>e</mtext>}}\text{mμ}$ ratio. The decay process μ → e + γ is strictly forbidden in this model.     

Generalized permutation symmetry and the flavour problem inSU(2)L×U(1)

A generalized permutation group is introduced as a possible horizontal symmetry forSU(2)_L×U(1) gauge theories. It leads to the unique two generation quark mass matrices with a correct prediction for the Cabibbo angle. For three generations the model exhibits spontaneousCP violation, correlates the Kobayashi-Maskawa mixing parameterss ₁ ands ₃ and predicts an upper bound for the running top quark mass of approximately 45 GeV. The hierarchy of generations is due to a hierarchy of vacuum expectation values rather than of Yukawa coupling constants.     

Contributions of stochastic background fields to the shear and bulk viscosities of the gluon plasma

The contributions of confining as well as nonconfining nonperturbative self-interactions of stochastic background fields to the shear and bulk viscosities of the gluon plasma in SU(3) Yang-Mills theory are calculated. The nonconfining self-interactions change (specifically, diminish) the values of the shear and bulk viscosities by 15%, that is close to the 17% which the strength of the nonconfining self-interaction amounts to the full strength of nonperturbative self-interactions. The ratios to the entropy density of the obtained nonperturbative contributions to the shear and bulk viscosities are compared with the results of perturbation theory and the predictions of N = 4 SYM.     

Einfaches Modell für monoatomare klassische Flüssigkeiten

A simple approximation for the conditional time-dependent pair distribution functionP(r′t ¦ rt) is proposed. With this approximation the van Hove-correlation-functionG _d (rt) is computed and compared with Ludwig's¹ computer results for liquid A1. Then we determine the velocity autocorrelationfunction ψ(t) under special assumptions for the particle motion. That function is compared with Rahman's² computer results for liquid Ar.     

Spin density functional theory of the temperature-dependent spin susceptibility: Pd and Pt

The finite temperature spin density functional (SDF) formalism is used to derive a variational expression for the temperature-dependent spin susceptibility χ_p(T) of an inhomogeneous electron gas. The use of a simple trial function in the variational expression results in a Stoner form for χ_p(T), i.e., χ_p(T) ≥ χ_s(T)/[1 - I(T) χ_s (T)] where χ_s(T) is the single-particle spin susceptibility including exchange-correlation (XC) effects on the band structure within the framework of the density functional formalism and I(T) is the SDF analog of the Stoner parameter. It should be emphasized that this form for χ_p(T) is derived for a general XC free energy functional F_xc[n, m; T]. χ_s(T) has been calculated self-consistently, including relativi stic effects, using the local approximation for F_xc for Pd and Pt. These results have been used to investigate the temperature dependence of I(T) required to explain their experimental susceptibilities. It is found that when the spin-orbit interaction is included in the calculation of χ_s(T), the temperature variation of I(T) is stronger than that of χ_s(T).     

Low-energy parity restoration and unification mass scale within maximal symmetries

We investigate the hierarchy of gauge boson masses in the maximal grand unified theory by studying the renormalization group equations for the running coupling constants associated with the symmetry breaking of SU(16)viaSU(12) _q×SU(4) _l×U(1) _|B|?|L| chain. Particular attention is given to the contribution of Higgs scalars to these equations. It is found that the intermediate mass scale M_L, associated with right-handed gauge bosons could be as low as 10 ³ GeV only for sin ²θ _w(M _L) as high as 0.265 with α _s(M _L)=0.13. In this chain of symmetry breaking, we have also examined the lowest unification mass that is allowed by the low-energy data for sin ²θ _w(M _L) and the assumed gauge hierarchy. This has been done in two cases; first for the case where SU(3) ^c is vectorial, second, for the case where SU(3) ^c is axial. In both cases the lowest unification mass scales were found to be 10 ¹³, 10 ¹¹, 10 ⁸ and 10 ⁷ GeV for sin ²θ _w(M _L) = 0.22, 0.24, 0.26,and0.265 respectively with α _s(M _L) = 0.13. The implication of these low unification masses on baryon non-conserving processes is also discussed.     

On the effect of the width of the scattering indicatrix on the dispersion of photon density waves in a strongly scattering medium

The dispersion of photon density waves in strongly scattering media with different widths of the scattering indicatrix is studied by the spherical harmonics method using approximations of various orders (up to the P ₇ approximation inclusive). It is shown that, beginning from the P ₃ approximation, the reduction in the velocity of photon density waves that is characteristic of the P ₁ approximation is eliminated and, independently of the width of the scattering indicatrix in the region of modulation frequencies exceeding 10¹⁰ Hz, the velocity of photon density waves asymptotically approaches the speed of light. Our study of the damping of photon density waves has shown that the formula obtained previously for the calculation of the damping coefficient (Imk(μ _s ^′ , ω)) as a function of the transport scattering coefficient and the velocity is valid at Imk ≤ μ_s (μ_s is the light scattering coefficient). The maximum growth in the damping coefficient of photon density waves with a further increase in the frequency is limited by the value of the light scattering coefficient Imk _max ≈ μ_s.     

Secondary vacuum trajectories and scalar meson exchange

A new second vacuum trajectory passing throughf*(1515) and σ(548), α(t)=? 0.3+t, is proposed, which, together with α_p″(t=0)=? 0.5, overcomes the failure of Igi's original superconvergent πN sum rule and avoids the ghost-state of the conventionalP′-trajectory. The negative residue att=0 confirms the repulsive contribution of a vacuum pole component withJ=0 to the generalizeds-reaction potential, as postulated by Chew (1965). TheP- andP′-poles can build the non resonating background. The Gell-Mann nonsense mechanism at the negative integers with wrong signature explains the dips in the elastic π^± p-scattering att=?0.7, ?2.7 and ?4.5 (GeV/c)². σ(∞) for πN reactions turns out to be 24.3 mb, if α _p (t=0)=1, but the best fits to the total πN cross sections for pion momenta between 2 and 29 GeV/c yield α _p (t=0)=0.93.     

Stark effect investigations of the 4f 14 6s 6p 3 P 1 and1 P 1 levels of ytterbium

The tensor polarizabilities of the 4f ¹⁴ 6s 6p ³ P ₁ level were investigated for all stable Ytterbium isotopes by the method of optical double resonance. The tensor polarizabilities were deduced from the rf-resonance signals in parallel electric and magnetic fields. The value obtained for the even Yb isotopes is in good agreement with the results derived from the measurements on the odd isotopes. The mean value isα _ten(³ P ₁)0=5.99(34)kHz/(kV/cm)². The tensor polarizability of the 4f ¹⁴ 6s 6p ¹ P ₁ level of¹⁷¹Yb was measured by means of the level crossing technique with parallel electric and magnetic fields. The experimental result isα _ten(¹ P ₁)=?14.3(1.4)kHz/(kV/cm)². This is compared with the prediction of the LS coupling approximation using the experimental data of the³ P ₁ level. Only poor agreement is obtained which is due to the configuration mixing in the¹P₁ level.     

Low-temperature deposition of α-Al2O3 films by laser chemical vapor deposition using a diode laser

We prepared Al₂O₃ films by laser chemical vapor deposition (LCVD) using a diode laser and aluminum acetylacetonate (Al(acac)₃) precursors and investigated the effects of laser power (P_L), deposition temperature (T_dep), and total pressure (P_tot) in a reaction chamber on the crystal phase, microstructure, and deposition rate (R_dep). An amorphous phase was obtained at P_L = 50 W, whereas an α-phase was obtained at P_L > 100 W. At P_L = 150 and 200 W (1 0 4)- and (0 1 2)-oriented α-Al₂O₃ films were obtained, respectively. The R_dep of α-Al₂O₃ films increases with decreasing P_L and P_tot. Single-phase α-Al₂O₃ film was obtained at T_dep = 928 K, which is about 350 K lower than that obtained by conventional thermal CVD using Al(acac)₃ precursor.