Weyl collineations that are not curvature collineations

Though the Weyl tensor is a linear combination of the curvature tensor, Ricci tensor and Ricci scalar, it does not have all and only the Lie symmetries of these tensors since it is possible, in principle, that "asymmetries cancel". Here we investigate if, when and how the symmetries can be different. It is found that we can obtain a metric with a finite dimensional Lie algebra of Weyl symmetries that properly contains the Lie algebra of curvature symmetries. There is no example found for the converse requirement. It is speculated that there may be a fundamental reason for this lack of "duality".Comment: 9 page

Photochemical Electrocyclic Ring Closure and Leaving Group Expulsion from N-(9-oxothioxanthenyl)Benzothiophene Carboxamides

N-(9-Oxothioxanthenyl)benzothiophene carboxamides bearing leaving groups (LG− = Cl−, PhS−, HS−, PhCH2S−) at the C-3 position of the benzothiophene ring system photochemically cyclize with nearly quantitative release of the leaving group, LG−. The LG− photoexpulsions can be conducted with 390 nm light or with a sunlamp. Solubility in 75% aqueous CH3CN is achieved by introducing a carboxylate group at the C-6 position of the benzothiophene ring. The carboxylate and methyl ester derivatives regiospecifically cyclize at the more hindered C-1 position of the thioxanthone ring. Otherwise, the photocyclization favors the C-3 position of the thioxanthone. Quantum yields for reaction are 0.01–0.04, depending on LG− basicity. Electronic structure calculations for the triplet excited state show that excitation transfer occurs from the thioxanthone to the benzothiophene ring. Subsequent cyclization in the triplet excited state is energetically favourable and initially generates the triplet excited state of the zwitterionic species. Expulsion of LG− is thought to occur once this species converts to the closed shell ground state

Toxicity induced by Solanapyrone A in Chickpea shoots and its metabolism through Glutathione/Glutathione-S-Transferase system

Solanapyrone A and C were isolated from a Pakistani isolate of Ascochyta rabiei, Pk-1. Two experiments were conducted to investigate the phytotoxic effects of the most potent toxin, solanapyrone A on chickpea cultivars and its subsequent detoxification through glutathion/glutathion-s-transferase(GST) system. When the shoots of cultivars were fed solanapyrone A, symptoms mimicking to Ascochyta blight appeared and extent of manifestation of symptoms varied with the cultivar. In the first experiment, the effect of three different plant ages of 2 cultivars with different levels of resistance to toxin was determined in terms of GST activity unit. GST activity in Balkasar-2000 (a resistant cultivar) increased 1.92 times, 1.72 and 1.65 times in two-week-old seedling, eight-week-old and adult plants (all treated) respectively as compared to their respective controls. In the highly susceptible cultivar, AUG-424, a slight increase (1.14 times) over control was noticed in GST activity at all the three ages. In the second experiment, where shoots of three cultivars were tested against 2 doses of the toxin, an increase in GST activity in Noor-91 (a moderately susceptible cultivar) and AUG-424 was significantly less than resistant cultivar, Balkasar-2000 showing direct relationship between resistance and activity of the enzyme. It may be concluded that it is a reason for difference in response of cultivars to the disease

Spherically Symmetric Gravitational Collapse

In this paper, we discuss gravitational collapse of spherically symmetric spacetimes. We derive a general formalism by taking two arbitrary spherically symmetric spacetimes with $g_{00}=1$. Israel's junction conditions are used to develop this formalism. The formulae for extrinsic curvature tensor are obtained. The general form of the surface energy-momentum tensor depending on extrinsic curvature tensor components is derived. This leads us to the surface energy density and the tangential pressure. The formalism is applied to two known spherically symmetric spacetimes. The results obtained show the regions for the collapse and expansion of the shell.Comment: 12 pages, 4 figures, accepted for publication in Mod. Phys. Lett.

Gravitational wave scintillation by a stellar cluster

The diffraction effects on gravitational waves propagating through a stellar cluster are analyzed in the relevant approximation of Fresnel diffraction limit. We find that a gravitational wave scintillation effect - similar to the radio source scintillation effect - comes out naturally, implying that the gravitational wave intensity changes in a characteristic way as the observer moves.Comment: 9 pages, in press in IJMP

Asymptotic Behaviour of the Proper Length and Volume of the Schwarzschild Singularity

Though popular presentations give the Schwarzschild singularity as a point it is known that it is spacelike and not timelike. Thus it has a "length" and is not a "point". In fact, its length must necessarily be infinite. It has been proved that the proper length of the Qadir-Wheeler suture model goes to infinity [1], while its proper volume shrinks to zero, and the asymptotic behaviour of the length and volume have been calculated. That model consists of two Friedmann sections connected by a Schwarzschild "suture". The question arises whether a similar analysis could provide the asymptotic behaviour of the Schwarzschild black hole near the singularity. It is proved here that, unlike the behaviour for the suture model, for the Schwarzschild essential singularity $\Delta s$ $\thicksim$ $K^{1/3}\ln K$ and $V\thicksim$ $K^{-1}\ln K$, where $K$ is the mean extrinsic curvature, or the York time.Comment: 13 pages, 1 figur

Planck view of the M82 galaxy

Planck data towards the galaxy M82 are analyzed in the 70, 100 and 143 GHz bands. A substantial north-south and East-West temperature asymmetry is found, extending up to 1 degree from the galactic center. Being almost frequency-independent, these temperature asymmetries are indicative of a Doppler-induced effect regarding the line-of-sight dynamics on the halo scale, the ejections from the galactic center and, possibly, even the tidal interaction with M81 galaxy. The temperature asymmetry thus acts as a model-independent tool to reveal the bulk dynamics in nearby edge-on spiral galaxies, like the Sunyaev-Zeldovich effect for clusters of galaxies.Comment: 4 pages, 3 figures, in press on A&

Planck revealed bulk motion of Centaurus A lobes

Planck data towards the active galaxy Centaurus A are analyzed in the 70, 100 and 143 GHz bands. We find a temperature asymmetry of the northern radio lobe with respect to the southern one that clearly extends at least up to 5 degrees from the Cen A center and diminishes towards the outer regions of the lobes. That transparent parameter - the temperature asymmetry - thus has to carry a principal information, i.e. indication on the line-of-sight bulk motion of the lobes, while the increase of that asymmetry at smaller radii reveals the differential dynamics of the lobes as expected at ejections from the center.Comment: 4 pages, 3 figures, Astronomy & Astrophysics, Letter to the Editor (in press

Messier 81's Planck view vs its halo mapping

This paper is a follow-up of a previous paper about the M82 galaxy and its halo based on Planck observations. As in the case of M82, so also for the M81 galaxy a substantial North-South and East-West temperature asymmetry is found, extending up to galactocentric distances of about $1.5^\circ$. The temperature asymmetry is almost frequency independent and can be interpreted as a Doppler-induced effect related to the M81 halo rotation and/or triggered by the gravitational interaction of the galaxies within the M81 Group. Along with the analogous study of several nearby edge-on spiral galaxies, the CMB temperature asymmetry method thus is shown to act as a direct tool to map the galactic haloes and/or the intergalactic bridges, invisible in other bands or by other methods.Comment: 5 pages, 3 figures, in press in Astronomy and Astrophysics, Main Journa