Approximating chiral SU(3) amplitudes

We construct large-N_c motivated approximate chiral SU(3) amplitudes of next-to-next-to-leading order. The amplitudes are independent of the renormalization scale. Fitting lattice data with those amplitudes allows for the extraction of chiral coupling constants with the correct scale dependence. The differences between approximate and full amplitudes are required to be at most of the order of N^3LO contributions numerically. Applying the approximate expressions to recent lattice data for meson decay constants, we determine several chiral couplings with good precision. In particular, we obtain a value for F_0, the meson decay constant in the chiral SU(3) limit, that is more precise than all presently available determinations.Comment: 19 pages, 4 figures, improved presentation, results unchanged, version to appear in EPJ

Changes of instability thresholds of rotor due to bearing misalignments

The influence of bearing misalignment upon the dynamic characteristics of statistically indeterminant rotor bearing systems is investigated. Both bearing loads and stability speed limits of a rotor may be changed significantly by magnitude and direction of bearing misalignment. The useful theory of short journal bearings is introduced and simple analytical expressions, governing the misalignment problem, are carried out. Polar plots for the bearing load capacities and stability maps, describing the speed limit in terms of misalignment, are presented. These plots can be used by the designer to estimate deviations between calculation and experimental data due to misalignment effects

Isospin violation in epsilon'

On the basis of a next-to-leading-order calculation in chiral perturbation theory, the first complete analysis of isospin breaking for direct CP violation in K^0 -> 2 pi decays is performed. We find a destructive interference between three different sources of isospin violation in the CP violation parameter epsilon'. Within the uncertainties of large-N_c estimates for the low-energy constants, the isospin violating correction for epsilon' is below 15 %.Comment: 4 page

Radiative Non-Leptonic Kaon Decays

We investigate to what extent DA$\Phi$NE will be able to test the Standard Model in the confinement regime with radiative kaon decays. We concentrate on processes which can be detected at DA$\Phi$NE and we review briefly those decays where only upper limits can be expected. The Standard Model predictions for these decays are analyzed in the framework of chiral perturbation theory.Comment: 41 pages, latex file, 10 figures added in a separate uufil

Microcanonical Thermodynamics of First Order Phase Transitions studied in the Potts Model

Phase transitions of first and second order can easily be distinguished in small systems in the microcanonical ensemble. Configurations of phase coexistence, which are suppressed in the canonical formulation, carry important information about the main characteristics of first order phase transitions like the transition temperature, the latent heat, and the interphase surface tension. The characterisitc backbending of the micro- canonical caloric equation of state T(E) (not to be confused with the well known Van der Waals loops in ordinary thermodynamics) leading to a negative specific heat is intimatly linked to the interphase surface entropy.Comment: Latex, 4 eps-figures, graphicx.st

The CP-violating asymmetry in K_L -> pi+ pi- e+ e-

We update the theoretical analysis of the CP-violating asymmetry in the decay K_L -> pi+ pi- e+ e-, relying on chiral perturbation theory and on the most recent phenomenological information. With the experimentally determined magnetic amplitude and branching ratio as input, the asymmetry can be calculated with good accuracy. The theoretical interpretation of the sign of the asymmetry is discussed.Comment: 11 page

Electromagnetism in nonleptonic weak interactions

We construct a low-energy effective field theory that permits the complete treatment of isospin-breaking effects in nonleptonic weak interactions to next-to-leading order. To this end, we enlarge the chiral Lagrangian describing strong and Delta S=1 weak interactions by including electromagnetic terms with the photon as additional dynamical degree of freedom. The complete and minimal list of local terms at next-to-leading order is given. We perform the one-loop renormalization at the level of the generating functional and specialize to K -> pi pi decays.Comment: 17 pages, 1 figure; 2 references added, final version for publication in Nucl. Phys.

Multi-informant investigation of college student drinking behaviors and social anxiety : the role of perceived descriptive and injunctive norms

Problematic alcohol use in college is a major public health concern. Identification of variables related to development of alcohol-related problems is an important research goal. Social anxiety and perceived social norms are two such variables. Social anxiety is associated with concurrent experience of alcohol-related problems and development of future problems with alcohol. Perceived norms, especially norms related to perceived approval of risky alcohol use (i.e., injunctive norms), are related to greater drinking problems among college students with higher social anxiety. College students typically overestimate the amount that other students in general use alcohol, and the discrepancy between perceived and actual norms is related to problems with alcohol. However, discrepancies between perceived and actual norms have not been evaluated for proximal peer group alcohol quantity, frequency, alcohol-related problems, and approval of risky drinking. The current study sought to identify if such discrepancies existed by asking 56 undergraduate online survey respondents to complete measures of alcohol use, alcohol-related problems, and perceived norms, and to refer one close friend who would complete a battery of self-report measures of their own alcohol use and actual norms. Results supported that students overestimated their friends’ injunctive norms and alcohol problems, but not descriptive norms. Social anxiety was negatively correlated with drinking frequency and not significantly correlated with alcohol-related problems. Higher misperception of friends’ problems was related to greater alcohol use quantity and alcohol-related problems. Higher injunctive norms discrepancy was related to fewer drinking occasions. Results highlight the importance of considering proximal peer groups when investigating the role of perceived norms and drinking behaviors

Enhanced Utilization of structural Damping of rotating Machines using impulsively shaped torsional Moments

The reduction of torsional vibrations of rotating machines is an important issue, as they may lead to a decrease of the performance, or in the worst case, to a damage of the machinery. In particular, self-excited vibrations have to be suppressed in any case due to their hazardous nature. In this contribution, a method is proposed, which allows utilizing the structural damping inherent to every rotating machine much more effectively by introducing impulsively shaped torsional moments, resulting in repeated modal transfers of vibration energy. Depending on the chosen impulsive strength, the energy transfers are accompanied by feeding external energy to, or extracting energy from the mechanical system. It is shown theoretically by approximating the impulses by Dirac-delta functions that an impulsive strength exists, where no energy crosses the system boundary, i.e. energy extracted from one mode is fed entirely to another mode of vibration. In the case of a conservative system, a repeated application of such impulses induces a periodic exchange of energy between lower and higher modes. Taking into account the structural damping reveals the advantages of transferring energy across modes. As higher modes possess higher damping ratios than lower ones, the structural damping of the rotating machine can be utilized much more effectively, which leads to a significant reduction of torsional vibrations. The underlying equations of motion of the impulsively excited system can be written as recursive difference equations with constant coefficients. Hence, the stability properties of the system can be investigated according to the Floquet theory. It is shown that the proposed concept is capable of suppressing self-excited vibrations. Stability charts are presented which allow to identify stable areas of operation. Finally, some numerical results of a test-rig are shown, underlining the effectivity of the proposed method

Radiative Four--Meson Amplitudes in Chiral Perturbation Theory

We present a general discussion of radiative four--meson processes to $O(p^4)$ in chiral perturbation theory. We propose a definition of ``generalized bremsstrahlung'' that takes full advantage of experimental information on the corresponding non--radiative process. We also derive general formulae for one--loop amplitudes which can be applied, for instance, to \eta \ra 3\pi\gamma, \pi \pi \ra \pi \pi \gamma and K \ra 3\pi\gamma.Comment: 8 pages, LaTex file, 1 figure. Full postscript version at this URL http://hpteor.lnf.infn.it/dafnepapers.htm