An Exploratory Study of Nucleon-Nucleon Scattering Lengths in Lattice QCD

An exploratory study is made of the nucleon-nucleon $s$-wave scattering lengths in quenched lattice QCD with the Wilson quark action. The $\pi$-$N$ and $\pi$-$\pi$ scattering lengths are also calculated for comparison. The calculations are made with heavy quarks corresponding to $m_\pi/m_\rho\approx 0.73-0.95$. The results show that the $N$-$N$ system has an attractive force in both spin-singlet and triplet channels, with their scattering lengths significantly larger than those for the $\pi$-$N$ and $\pi$-$\pi$ cases, a trend which is qualitatively consistent with the experiment. Problems toward a more realistic calculation for light quarks are discussed.Comment: 9 pages. Latex file. Figures are also included as ps file

Self-Force on a Scalar Charge in Circular Orbit around a Schwarzschild Black Hole

In an accompanying paper, we have formulated two types of regulariz_ation methods to calculate the scalar self-force on a particle of charge $q$ moving around a black hole of mass $M$, one of which is called the ``power expansion regularization''. In this paper, we analytically evaluate the self-force (which we also call the reaction force) to the third post-Newtonian (3PN) order on the scalar particle in circular orbit around a Schwarzschild black hole by using the power expansion regularization. It is found that the $r$-component of the self-force arises at the 3PN order, whereas the $t$- and $\phi$-components, which are due to the radiation reaction, appear at the 2PN and 1.5PN orders, respectively

Quantum-Liouville and Langevin Equations for Gravitational Radiation Damping

From a forward--backward path integral, we derive a master equation for the emission and absorption of gravitons by a massive quantum object in a heat bath of gravitons. Such an equation could describe collapse phenomena of dense stars. We also present a useful approximate Langevin equation for such a system.Comment: Author Information under http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of paper (including all PS fonts) at http://www.physik.fu-berlin.de/~kleinert/31

Thermal comfort in dwellings in the subtropical highlands - Case study in the Ecuadorian Andes

Thermal comfort in dwellings located in different weather conditions have been largely studied. The indoor environmental criteria have been well defined for mechanically conditioned buildings in mid-latitudes and naturally ventilated spaces in the subtropics. The subtropics are known for being hot-humid environments at low altitude. However, the highlands in the tropics have a subtropical-highland climate characterised by narrow annual temperature oscillation, noticeable diurnal temperature variation and high levels of solar radiation and precipitation due to its latitude and altitude. Field thermal comfort studies in housing in the Highlands reveals up to a 90% of user's satisfaction to temperature below 18°C. Indoor temperatures in dwellings in the Andes highlands can be even lower than 18°C as buildings are uninsulated and operate under free-running conditions throughout the year. This study seeks to identify the thermal comfort range and the difference in residents' perception of inhabitants living between 2300 m and 3100 m above sea level, in the Andes highlands. 195 thermal comfort votes were collected during the dry season. Results show that people living in the high-altitude are more sensitive to draught and prefer lower temperatures (16°C - 24°C), while inhabitants living in the low-altitude find temperatures above 26°C pleasant and prefer higher air movement

Mechanism of photodamage of the oxygen evolving Mn Cluster of Photosystem II by excessive light energy

© 2017 The Author(s). Photodamage to Photosystem II (PSII) has been attributed either to excessive excitation of photosynthetic pigments or by direct of light absorption by Mn4CaO5 cluster. Here we investigated the time course of PSII photodamage and release of Mn in PSII-enriched membranes under high light illumination at 460 nm and 660 nm. We found that the loss of PSII activity, assayed by chlorophyll fluorescence, is faster than release of Mn from the Mn4CaO5 cluster, assayed by EPR. Loss of PSII activity and Mn release was slower during illumination in the presence of exogenous electron acceptors. Recovery of PSII activity was observed, after 30 min of addition of electron donor post illumination. The same behavior was observed under 460 and 660 nm illumination, suggesting stronger correlation between excessive excitation and photodamage compared to direct light absorption by the cluster. A unified model of PSII photodamage that takes into account present and previous literature reports is presented

B_K with the Wilson Quark Action: A Non-Perturbative Resolution of Operator Mixing using Chiral Ward Identities

We propose a non-perturbative method to determine the mixing coefficients of $\Delta s=2$ four-quark operators for the Wilson quark action using chiral Ward identities. The method is applied to calculate B_K in quenched QCD.Comment: 3 pages including 3 figures, Talk presented at LATTICE96(phenomenology) by Y. Kuramash

Sea Quark Effects on the Strong Coupling Constant

We present results showing that the strong coupling constant measured in two-flavor full QCD with dynamical Kogut-Susskind quarks at $\beta=5.7$ exhibit a 15\% increase due to sea quarks over that for quenched QCD at the scale $\mu\approx 7$GeV . (talk at lattice93)Comment: 3 pages, compressed, uuencoded PostScript file(name:lat93ch.ps.Z