Weak Value in Wave Function of Detector

A simple formula to read out the weak value from the wave function of the measuring device after the postselection with the initial Gaussian profile is proposed. We apply this formula for the weak value to the classical experiment of the realization of the weak measurement by the optical polarization and obtain the weak value for any pre- and post-selections. This formula automatically includes the interference effect which is necessary to yields the weak value as an outcome of the weak measurement.Comment: 3 pages, no figures, Published in Journal of the Physical Society of Japa

Cytokine Profiles of Stimulated Blood Lymphocytes in Asthmatic and Healthy Adolescents Cross the School Year

T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-γ (IFN-γ), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th 1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-γ:IL-4 and IFN-γ:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation

Indistinguishable Particles in Quantum Mechanics: An Introduction

In this article, we discuss the identity and indistinguishability of quantum systems and the consequent need to introduce an extra postulate in Quantum Mechanics to correctly describe situations involving indistinguishable particles. This is, for electrons, the Pauli Exclusion Principle, or in general, the Symmetrization Postulate. Then, we introduce fermions and bosons and the distributions respectively describing their statistical behaviour in indistinguishable situations. Following that, we discuss the spin-statistics connection, as well as alternative statistics and experimental evidence for all these results, including the use of bunching and antibunching of particles emerging from a beam splitter as a signature for some bosonic or fermionic states.Comment: To appear in Contemp. Phy

Inelastic collapse of a randomly forced particle

We consider a randomly forced particle moving in a finite region, which rebounds inelastically with coefficient of restitution r on collision with the boundaries. We show that there is a transition at a critical value of r, r_c\equiv e^{-\pi/\sqrt{3}}, above which the dynamics is ergodic but beneath which the particle undergoes inelastic collapse, coming to rest after an infinite number of collisions in a finite time. The value of r_c is argued to be independent of the size of the region or the presence of a viscous damping term in the equation of motion.Comment: 4 pages, REVTEX, 2 EPS figures, uses multicol.sty and epsf.st

On the geometry of quantum indistinguishability

An algebraic approach to the study of quantum mechanics on configuration spaces with a finite fundamental group is presented. It uses, in an essential way, the Gelfand-Naimark and Serre-Swan equivalences and thus allows one to represent geometric properties of such systems in algebraic terms. As an application, the problem of quantum indistinguishability is reformulated in the light of the proposed approach. Previous attempts aiming at a proof of the spin-statistics theorem in non-relativistic quantum mechanics are explicitly recast in the global language inherent to the presented techniques. This leads to a critical discussion of single-valuedness of wave functions for systems of indistinguishable particles. Potential applications of the methods presented in this paper to problems related to quantization, geometric phases and phase transitions in spin systems are proposed.Comment: 24 page

Optimization of R(e+e-) and "Freezing" of the QCD Couplant at Low Energies

The new result for the third-order QCD corrections to R_{e^+e^-}, unlike the old, incorrect result, is nicely compatible with the principle-of-minimal-sensitivity optimization method. Moreover, it leads to infrared fixed-point behaviour: the optimized couplant, alpha_s/pi, for R(e+e-) does not diverge at low energies, but "freezes" to a value 0.26 below about 300 MeV. This provides some direct theoretical evidence, purely from perturbation theory, for the "freezing" of the couplant -- an idea that has long been a popular and successful phenomenological hypothesis. We use the "smearing" method of Poggio, Quinn, and Weinberg to compare the resulting theoretical prediction for R(e+e-) with experimental data down to the lowest energies, and find excellent agreement.Comment: 27 pages, LaTeX, 8 uuencoded figures, DE-FG05-92ER40717-

Covariant and Heavy Quark Symmetric Quark Models

There exist relativistic quark models (potential or MIT-bag) which satisfy the heavy quark symmetry (HQS) relations among meson decay constants and form factors. Covariant construction of the momentum eigenstates, developed here, can correct for spurious center-of-mass motion contributions.Proton form factor and M1 transitions in quarkonia are calculated. Explicit expression for the Isgur-Wise function is found and model determined deviations from HQS are studied. All results depend on the model parameters only. No additional ad hoc assumptions are needed.Comment: 34 pages (2 figures not included but avaliable upon request), LATEX, (to be published in Phys.Rev.D

Sigma-term physics in the perturbative chiral quark model

We apply the perturbative chiral quark model (PCQM) at one loop to analyse meson-baryon sigma-terms. Analytic expressions for these quantities are obtained in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). Our result for the piN sigma term of about 45 MeV is in good agreement with the value deduced by Gasser, Leutwyler and Sainio using dispersion-relation techniques and exploiting the chiral symmetry constraints.Comment: 19 pages, LaTeX-file, 2 Figure

Quantum Particles as Conceptual Entities: A Possible Explanatory Framework for Quantum Theory

We put forward a possible new interpretation and explanatory framework for quantum theory. The basic hypothesis underlying this new framework is that quantum particles are conceptual entities. More concretely, we propose that quantum particles interact with ordinary matter, nuclei, atoms, molecules, macroscopic material entities, measuring apparatuses, ..., in a similar way to how human concepts interact with memory structures, human minds or artificial memories. We analyze the most characteristic aspects of quantum theory, i.e. entanglement and non-locality, interference and superposition, identity and individuality in the light of this new interpretation, and we put forward a specific explanation and understanding of these aspects. The basic hypothesis of our framework gives rise in a natural way to a Heisenberg uncertainty principle which introduces an understanding of the general situation of 'the one and the many' in quantum physics. A specific view on macro and micro different from the common one follows from the basic hypothesis and leads to an analysis of Schrodinger's Cat paradox and the measurement problem different from the existing ones. We reflect about the influence of this new quantum interpretation and explanatory framework on the global nature and evolutionary aspects of the world and human worldviews, and point out potential explanations for specific situations, such as the generation problem in particle physics, the confinement of quarks and the existence of dark matter.Comment: 45 pages, 10 figure