3,334 research outputs found
Retardation effects in the rotating string model
A new method to study the retardation effects in mesons is presented.
Inspired from the covariant oscillator quark model, it is applied to the
rotating string model in which a non zero value is allowed for the relative
time between the quark and the antiquark. This approach leads to a retardation
term which behaves as a perturbation of the meson mass operator. It is shown
that this term preserves the Regge trajectories for light mesons, and that a
satisfactory agreement with the experimental data can be obtained if the quark
self-energy contribution is added. The consequences of the retardation on the
Coulomb interaction and the wave function are also analyzed.Comment: 4 figure
Was an Outburst of Aquila X-1 a Magnetic Flare?
I point to an interesting similarity in the radio and the soft X-ray light
curves between the November 2009 outburst of the X-ray binary Aquila X-1 and
some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila
X-1 in that outburst is also similar to some weak solar flares, and so is the
radio spectrum near 8 GHz. Based on these, as well as on some other recent
studies that point to some similar properties of accretion disk coronae and
stellar flares, such as ratio of radio to X-ray luminosities (Laor & Behar
2008), I speculate that the soft X-ray outburst of Aquila X-1 was related to a
huge magnetic flare from its disk corona.Comment: accepted by ApJ Letter
Drum Beating and a Martial Art Bojutsu Performed by a Humanoid Robot
Over the past few decades a considerable number of studies have been made on impact dynamics. Zheng and Hemami discussed a mathematical model of a robot that collides with an environment (Zheng & Hemami, 1985). When a robot arm fixed on the ground collides with a hard environment, the transition from the free space to constrained space may bring instabilit
Episodic Volunteering in Sport Events : A Seven-Country Analysis
Given its ubiquitous nature, sport events are one of the most popular venues for episodic volunteering around the world. This article explores the rare dataset of volunteering in sport events in seven countries-Finland, Ghana, India, Japan, Switzerland, Tanzania, United States-to overview the differences and similarities identified in demography, volunteers' reactions to hosts' management strategies, satisfaction, and intention to volunteer again. Key findings include differences in the level of satisfaction, where responses among American volunteers were the highest. We also find that although well-organized management strategies such as quality training, communication, and proper appreciation led to higher satisfaction, these factors did not contribute to volunteers' intent to volunteer again. Such management style might be too impersonal with less autonomy on the part of volunteers that they may not feel needed in future events. Somewhat messy management might motivate volunteers to participate again.Peer reviewe
Vortex Charging Effect in a Chiral -Wave Superconductor
Quasiparticle states around a single vortex in a -wave
superconductor are studied on the basis of the Bogoliubov-de Gennes (BdG)
theory, where both charge and current screenings are taken into account. Due to
the violation of time reversal symmetry, there are two types of vortices which
are distinguished by their winding orientations relative to the angular
momentum of the chiral Cooper pair. The BdG solution shows that the charges of
the two types of vortices are quite different, reflecting the rotating Cooper
pair of the -wave paring state.Comment: 10 pages, 5 figures, revtex, to be published in Phys. Rev.
Social Capital and Mental Health in Japan: A Multilevel Analysis
A national cross-sectional survey was conducted in Japan. This is because the growing recognition of the social determinants of health has stimulated research on social capital and mental health. In recent years, systematic reviews have found that social capital may be a useful factor in the prevention of mental illness. Despite these studies, evidence on the association between social capital and mental health is limited as there have been few empirical discussions that adopt a multilevel framework to assess whether social capital at the ecological level is associated with individual mental health. The aim of this study was to use the multilevel approach to investigate the association between neighborhood social capital and mental health after taking into account potential individual confounders.We conducted a multilevel analysis on 5,956 individuals nested within 199 neighborhoods. The outcome variable of self-reported mental health was measured by the one dimension of SF-36 and was summed to calculate a score ranging from 0 to 100. This study showed that high levels of cognitive social capital, measured by trust (regression coefficient = 9.56), and high levels of structural social capital, measured by membership in sports, recreation, hobby, or cultural groups (regression coefficient = 8.72), were associated with better mental health after adjusting for age, sex, household income, and educational attainment. Furthermore, after adjusting for social capital perceptions at the individual level, we found that the association between social capital and mental health also remained.Our findings suggest that both cognitive and structural social capital at the ecological level may influence mental health, even after adjusting for individual potential confounders including social capital perceptions. Promoting social capital may contribute to enhancing the mental health of the Japanese
Effect of Band Structure on the Symmetry of Superconducting States
Effects of the band structure on the symmetry of superconducting (SC) states
are studied. For a square lattice system with a nearest-neighbor attractive
interaction, SC states with various symmetries are found by changing the band
structure, or, the shape of the Fermi surface. The spin-triplet (-wave) and spin-singlet (- or s-wave) SC states, and states with their
coexistence (, ) can be stabilized within the same type of
interaction. The stability of interlayer-pairing states with line nodes is also
examined, and its relation to the SC state of SrRuO is discussed.Comment: 4 pages, 4 figure
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