Cosmological dynamics of non-minimally coupled scalar field system and its late time cosmic relevance

We investigate the cosmological dynamics of non-minimally coupled scalar field system described by $F(\phi)R$ coupling with $F(\phi)=(1-\xi\phi^N)R$($N\ge2$) and the field potential, $V(\phi)=V_0\phi^n$. We use a generic set of dynamical variables to bring out new asymptotic regimes of the underlying dynamics. However, our dynamical variables miss the most important fixed point$-$ the de Sitter solution. We make use of the original form of system of equations to investigate the issues related to this important solution. In particular, we show that the de-Sitter solution which is a dynamical attractor of the system lies in the region of negative effective gravitational constant $G_N$ thereby leading to a ghost dominated universe in future and a transient quintessence(phantom) phase with $G_N>0$ around the present epoch (however, as demonstrated by Starobinsky in 1981, the ghost dominated universe, if exists, can not be accessed from the Universe we live in, we shall say more about this important result in the last section). We also carry out comparison of the model with other competing models of dark energy such as galileon modified gravity and others.Comment: 22 pages and 7 figures, minor clarifications added, revised version to appear in PR

Water use vs. socio-economic factors in a water stressed urban area having economic affluence

The paper presents household water-use data collected from a water use survey in an urban area located in a water stressed region in the Middle East. The purpose of the survey was to investigate the effect and relationships of water shortage, economic effluence and socioeconomic attributes of house holds on per capita water use in the area. Results indicated wide variation of water uses in smaller districts of the urban area. In small areas socioeconomic factors are significantly related to per capita water use. However, when total urban area is considered, same set of factors do not show any meaningful relationship to per capita water use. Water use in summer is about 2-6 times more than that in winter. Over all per capita water use in the area is recorded to be one the highest in the world

SENSITIVITY OF JET CHARACTERISTICS ON DREDGING OF BED-SEDIMENTS IN A WATER-BODY

The use of a suction field aided by a jet system in a dredging process is one of the recent hydraulic methods in underwater dredging. The jet parameters have a great influence on the dredging efficiency. Jet induced impact energy that is required to initiate the bed motion and sediment pulsation is considered. Parametric sensitivity of various factors on dredging performance was carried out in an experimental set-up. Effects of changing the number of jets, jet geometry, suspension concentration, horizontal and vertical distances between jets and suction inlet on the dredging efficiency and the geometry of the excavation hole have been investigated. The results showed that several of these parameters have variable and significant effects on the dredging efficiency as well as the resulting geometry of the excavation

Cosmological dynamics of a nonminimally coupled scalar field system and its late time cosmic relevance

We investigate the cosmological dynamics of a nonminimally coupled scalar field system described by F()R coupling with F()=(1-ξN)R(N2) and the field potential V()=V 0n. We use a generic set of dynamical variables to bring out new asymptotic regimes of the underlying dynamics. However, our dynamical variables miss the most important fixed point-the deSitter solution. We make use of the original form of the system of equations to investigate the issues related to this important solution. In particular, we show that the deSitter solution which is a dynamical attractor of the system lies in the region of negative effective gravitational constant G N, thereby leading to a ghost-dominated universe in the future and a transient quintessence (phantom) phase with G N>0 around the present epoch. We also carry out a comparison of the model with other competing models of dark energy, such as Galileon-modified gravity and others. © 2012 American Physical Society