On high Q(2) behavior of the pion form factor for transitions gamma*gamma -> pi(0) and gamma*gamma* -> pi(0) within the nonlocal quark-pion model

The behavior of the transition pion form factor for processes gamma (*)gamma --> pi(0) and gamma (*)gamma (*) --> pi(0) at large values of space-like photon momenta is estimated within the nonlocal covariant quark-pion model. It is shown that, in general, the coefficient of the leading asymptotic term depends dynamically on the ratio of the constituent quark mass and the average virtuality of quarks in the vacuum and kinematically on the ratio of photon virtualities. The kinematic dependence of the transition form factor allows us to obtain the relation between the pion light-cone distribution amplitude and the quark-pion vertex function. The dynamic dependence indicates that the transition form factor gamma (*)gamma -->, pi(0) at high momentum transfers is very sensitive to the nonlocality size of nonperturbative fluctuations in the QCD vacuum. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Pion structure in the instanton liquid model

The covariant quark model of the pion based on the effective nonlocal quark-hadron Lagrangian involving nonlocality induced by instanton fluctuations of the QCD vacuum is reviewed. Explicit gauge invariant formalism allows us to construct the conserved vector and axial currents and to demonstrate their consistency with the Ward-Takahashi identities and low-energy theorems. The spontaneous breaking of chiral symmetry results in the dynamic quark mass and the vertex of the quark-pion interaction, both momentum-dependent. The parameters of the instanton vacuum, the average size of the instantons, and the effective quark mass are expressed in terms of the vacuum expectation values of the lowest dimension quark-gluon operators and low-energy pion observables. The transition pion form factor for the processes gamma*gamma --> pi (0) and gamma*gamma* --> pi (0) is analyzed in detail. The kinematic dependence of the transition form factor at high momentum transfers allows one to determine the relationship between the light-cone amplitude of the quark distribution in the pion and the quark-pion vertex function. Its dynamic dependence implies that the transition form factor gamma*gamma --> pi (0) at high momentum transfers is acutely sensitive to the size of the nonlocality of nonperturbative fluctuations in the QCD vacuum. In the leading twist, the distribution amplitude and the distribution function of the valence quarks in the pion are calculated at a low normalization point of the order of the inverse average instanton size rho (-1)(c). The QCD results are evolved to higher momentum transfers and are in reasonable agreement with available experimental data on the pion structure.

A path integral approach to the full Dicke model with dipole-dipole interaction

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dual superconformal symmetry, and the amplitude/Wilson loop connection

We show that tree level superstring theories on certain supersymmetric backgrounds admit a symmetry which we call "fermionic T-duality". This is a non-local redefinition of the fermionic worldsheet fields similar to the redefinition we perform on bosonic variables when we do an ordinary T-duality. This duality maps a supersymmetric background to another supersymmetric background with different RR fields and a different dilaton. We show that a certain combination of bosonic and fermionic T-dualities maps the full superstring theory on AdS(5) x S-5 back to itself in such a way that gluon scattering amplitudes in the original theory map to something very close to Wilson loops in the dual theory. This duality maps the "dual superconformal symmetry" of the original theory to the ordinary superconformal symmetry of the dual model. This explains the dual superconformal invariance of planar scattering amplitudes of N = 4 super Yang Mills and also sheds some light on the connection between amplitudes and Wilson loops. In the appendix, we propose a simple prescription for open superstring MHV tree amplitudes in a flat background.

Three-body model of the final state interaction in heavy meson decay

We develop a relativistic three-body model for the final state interaction in D(+) -> K(-) pi(+) pi(+) decay based on the ladder approximation of the Bethe-Salpeter equation. The decay amplitude has the standard two-meson resonant transition matrix modulated by a spectator amplitude that carries a fully interacting three-body contribution and a smooth background term from the partonic amplitude. Our calculations are compared with D decay data.

THE HIGGS PORTAL and AN UNIFIED MODEL FOR DARK ENERGY and DARK MATTER

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Towards brane-antibrane inflation in type IIA: the holographic MQCD mode

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

STRONG COUPLING LIMITS and QUANTUM ISOMORPHISMS of THE GAUGED THIRRING MODEL

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

First study of the radiation-amplitude zero in W gamma production and limits on anomalous WW gamma couplings at root s=1.96 TeV

We present results from a study of p (p) over bar -> W gamma+X events utilizing data corresponding to 0.7 fb(-1) of integrated luminosity at root s = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We set limits on anomalous WW gamma couplings at the 95% C.L. The one-dimensional 95% C.L. limits are 0.49 model radiation-amplitude zero in the W gamma system.

Path integral approach to the full Dicke model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Search for the standard model Higgs boson in the H -> ZZ -> l(+)l(-)tau(+)tau(-) decay channel in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Phase-Locked loops lock-in range in Frequency Modulated-Atomic Force Microscope nonlinear control system

Since the mid 1980s the Atomic Force Microscope is one the most powerful tools to perform surface investigation, and since 1995 Non-Contact AFM achieved true atomic resolution. The Frequency-Modulated Atomic Force Microscope (FM-AFM) operates in the dynamic mode, which means that the control system of the FM-AFM must force the micro-cantilever to oscillate with constant amplitude and frequency. However, tip-sample interaction forces cause modulations in the microcantilever motion. A Phase-Locked loop (PLL) is used to demodulate the tip-sample interaction forces from the microcantilever motion. The demodulated signal is used as the feedback signal to the control system, and to generate both topographic and dissipation images. As a consequence, a proper design of the PLL is vital to the FM-AFM performance. In this work, using bifurcation analysis, the lock-in range of the PLL is determined as a function of the frequency shift (Q) of the microcantilever and of the other design parameters, providing a technique to properly design the PLL in the FM-AFM system. (C) 2011 Elsevier B.V. All rights reserved.

A note on the attenuation of the sommerfeld effect of a non-ideal system taking into account a MR damper and the complete model of a DC motor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

EXPANSION OF THE DISTURBING FUNCTION FOR HIGH ECCENTRICITY AND LARGE-AMPLITUDE OF LIBRATION

Following some ideas, developed by Woltjer (1928), Message (1989), Yokoyama (1988, 1989) and Duriez (1990) an expansion of the disturbing function is given for high values of the eccentricity and large amplitude of libration. The classical expansion can be obtained as a particular case of the present model. Several asteroids with high eccentricity and large amplitude of libration are tested and the results are much better than those obtained from the classical theory.

The dead core model applied to beads with immobilized cells in a fed-batch cephalosporin C production bioprocess

Viable cells immobilized in inert supports are currently studied for a wide range of bioprocesses. The intrinsic advantages of such systems over suspended cultures incite new research, including studies on fundamental aspects as well as on the industrial viability of these non-conventional processes. In aerobic culture of filamentous fungi, scale-up is hindered by oxygen mass transfer limitation through the support material and bioprocess kinetics must be studied together with mass transfer limitation. In this work, experimental and simulated data of cephalosporin C production were compared. Concentrations in the bulk fermentation medium and cellular mass profiles inside the bioparticles are focused. Immobilized cells were used in a tower bioreactor, operated in fed-batch mode. To describe the radial variation of oxygen concentration within the pellet, a dead core model was used. Despite the extremely low sugar concentrations, bioreaction rates in the pellets were limited by the dissolved oxygen concentration. Cell growth occurs only in the outer layers, a result also confirmed by scanning electron microscopy. (C) 2001 Elsevier B.V. Ltd. All rights reserved.