Spectroscopic Factors in 40^{40}Ca and 208^{208}Pb from (e,e′p)(e,e'p): Fully Relativistic Analysis

We present results for spectroscopic factors of the outermost shells in $^{40}$Ca and $^{208}$Pb, which have been derived from the comparison between the available quasielastic ($e,e'p$) data from NIKHEF-K and the corresponding calculated cross-sections obtained within a fully relativistic formalism. We include exactly the effect of Coulomb distortion on the electron wave functions and discuss its role in the extraction of the spectroscopic factors from experiment. Without any adjustable parameter, we find spectroscopic factors of about 70\%, consistent with theoretical predictions. We compare our results with previous relativistic and nonrelativistic analyses of ($e,e'p$) data. In addition to Coulomb distortion effects we discuss different choices of the nucleon current operator and also analyze the effects due to the relativistic treatment of the outgoing-distorted and bound nucleon wave functions.Comment: 9 pages RevTeX, 5 figures can be obtained from the author

Scalar Particle Contribution to Higgs Production via Gluon Fusion at NLO

We consider the gluon fusion production cross section of a scalar Higgs boson in models where fermion and scalar massive colored particles are present. We report analytic expressions for the matrix elements of $gg\to Hg$, $q\bar{q}\to Hg$, and $qg\to Hq$ processes completing the calculation of the NLO QCD corrections in these extended scenarios. The formulas are written in a complete general case, allowing a flexible use for different theoretical models. Applications of our results to two different models are presented: i) a model in which the SM Higgs sector is augmented by a weak doublet scalar in the $SU(N_c)$ adjoint representation. ii) The MSSM, in the limit of neglecting the gluino contribution to the cross section.Comment: 20 pages, 5 figures. Minor changes. Refs. adde

Relativistic versus Nonrelativistic Optical Potentials in A(e,e'p)B Reactions

We investigate the role of relativistic and nonrelativistic optical potentials used in the analysis of ($e,e'p$) data. We find that the relativistic calculations produce smaller ($e,e'p$) cross sections even in the case in which both relativistic and nonrelativistic optical potentials fit equally well the elastic proton--nucleus scattering data. Compared to the nonrelativistic impulse approximation, this effect is due to a depletion in the nuclear interior of the relativistic nucleon current, which should be taken into account in the nonrelativistic treatment by a proper redefinition of the effective current operator.Comment: Added one new figure, the formalism section has been enlarged and the list of references updated. Added one appendix. This version will appear in Phys. Rev. C. Revtex 3.0, 6 figures (not included). Full postscript version of the file and figures available at http://www.nikhefk.nikhef.nl/projects/Theory/preprints

Microscopic Theory of Josephson Mesoscopic Constrictions

We present a microscopic theory for the d.c. Josephson effect in model mesoscopic constrictions. Our method is based on a non-equilibrium Green function formalism which allows for a self-consistent determination of the order parameter profile along the constriction. The various regimes defined by the different length scales (Fermi wavelength $\lambda_F$, coherence length $\xi_0$ and constriction length $L_C$) can be analyzed, including the case where all these lengths are comparable. For the case $\lambda_F \tilde{<} (L_C,\xi_0)$ phase oscillations with spatial period $\lambda_F/2$ can be observed. In the case of $L_C>\xi_0$ solutions with a phase-slip center inside the constriction can be found, in agreement with previous phenomenological theories.Comment: 4 pages (RevTex 3.0), 3 postscript figures available upon request, 312456-C

On the statistical significance of the conductance quantization

Recent experiments on atomic-scale metallic contacts have shown that the quantization of the conductance appears clearly only after the average of the experimental results. Motivated by these results we have analyzed a simplified model system in which a narrow neck is randomly coupled to wide ideal leads, both in absence and presence of time reversal invariance. Based on Random Matrix Theory we study analytically the probability distribution for the conductance of such system. As the width of the leads increases the distribution for the conductance becomes sharply peaked close to an integer multiple of the quantum of conductance. Our results suggest a possible statistical origin of conductance quantization in atomic-scale metallic contacts.Comment: 4 pages, Tex and 3 figures. To be published in PR

Surface Terms as Counterterms in the AdS/CFT Correspondence

We examine the recently proposed technique of adding boundary counterterms to the gravitational action for spacetimes which are locally asymptotic to anti-de Sitter. In particular, we explicitly identify higher order counterterms, which allow us to consider spacetimes of dimensions d<=7. As the counterterms eliminate the need of ``background subtraction'' in calculating the action, we apply this technique to study examples where the appropriate background was ambiguous or unknown: topological black holes, Taub-NUT-AdS and Taub-Bolt-AdS. We also identify certain cases where the covariant counterterms fail to render the action finite, and we comment on the dual field theory interpretation of this result. In some examples, the case of vanishing cosmological constant may be recovered in a limit, which allows us to check results and resolve ambiguities in certain asymptotically flat spacetime computations in the literature.Comment: Revtex, 18 pages. References updated and few typo's fixed. Final versio

Electronic localization at mesoscopic length scales: different definitions of localization and contact effects in a heuristic DNA model

In this work we investigate the electronic transport along model DNA molecules using an effective tight-binding approach that includes the backbone on site energies. The localization length and participation number are examined as a function of system size, energy dependence, and the contact coupling between the leads and the DNA molecule. On one hand, the transition from an diffusive regime to a localized regime for short systems is identified, suggesting the necessity of a further length scale revealing the system borders sensibility. On the other hand, we show that the lenght localization and participation number, do not depended of system size and contact coupling in the thermodynamic limit. Finally we discuss possible length dependent origins for the large discrepancies among experimental results for the electronic transport in DNA sample

Modelling caregiving interactions during stress

Few studies describing caregiver stress and coping have focused on the effects of informal caregiving for depressed care recipients.The major purpose of this paper was to investigate the dynamics of the informal care support and receipt interactions among caregivers and care recipients using a computational modelling approach.Important concepts in coping skills, strong ties support networks and stress buffering studies were used as a basis for the model design and verification.Simulation experiments for several cases pointed out that the model is able to reproduce interaction among strong tie network members during stress.In addition, the possible equillibria of the model have been determined, and the model has been automatically verified against expected overall properties

Modelling caregiving interactions during stress

Few studies describing caregiver stress and coping have focused on the effects of informal caregiving for depressed care recipients.The major purpose of this paper was to investigate the dynamics of the informal care support and receipt interactions among caregivers and care recipients using a computational modelling approach.Important concepts in coping skills, strong ties support networks and stress buffering studies were used as a basis for the model design and verification.Simulation experiments for several cases pointed out that the model is able to reproduce interaction among strong tie network members during stress.In addition, the possible equillibria of the model have been determined, and the model has been automatically verified against expected overall properties