Charged Fluid Dynamics in Scalar-Tensor Theories of Gravity with Torsion

n scalar-tensor theories of gravity with torsion, the gravitational field is described in terms of a symmetric metric tensor $g$, a metric-compatible connection $\nabla$ with torsion, and a scalar field $\phi$. The main aim is to explore an interaction of a charged perfect fluid and a scalar field $\phi$ in a background electromagnetic and gravitational field described by \{$g$, $\nabla$, $\phi$\}. The interaction is based on an action functional $S_C$ of a charged perfect fluid that is invariant under global conformal rescalings. Using a variational principle, we obtain equations of motion for the charged perfect fluid. Moreover, we verify that these equations of motion are equivalent to the gauge identities obtained from the invariance of an action functional under spacetime dffeomorphisms and a local U(1) gauge group.Comment: 4 page

Design for a motorized, wearable, and concept sports vehicle

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Gravitational radiations of generic isolated horizons and non-rotating dynamical horizons from asymptotic expansions

Instead of using a three dimensional analysis on quasi-local horizons, we adopt a four dimensional asymptotic expansion analysis to study the next order contributions from the nonlinearity of general relativity. From the similarity between null infinity and horizons, the proper reference frames are chosen from the compatible constant spinors for an observer to measure the energy-momentum and flux near quasi-local horizons. In particular, we focus on the similarity of Bondi-Sachs gravitational radiation for the quasi-local horizons and compare our results to Ashtekar-Kirshnan flux formular. The quasi-local energy momentum and flux of generic isolated horizons and non-rotating dynamical horizons are discussed in this paper.Comment: PRD, 15 page

VARIABILITY OF BARBELL TRAJECTORY DURING SNATCH FOR AN ELITE YOUNG FEMALE WEIGHTLIFTER

The purpose of this study was to investigate the variability of the barbell trajectory for an elite young female weightlifter. One high speed camera (120Hz) was used to film the barbell trajectories of a female lifter during snatch. The subject was asked to lift different barbell mass from 65 to 80 kg (fourteen lifts in total), and thirteen successful lifts were analyzed. The barbell trajectories and movement pattern of different lifts were similar to the results of previous studies, and the barbell paths almost were overlapping for the heaviest four successful lifts. The coefficients of variation (CV) of four kinematic parameters of barbell trajectory were smaller than the results of previous studies. It can be concluded that this female weightlifter has a stable pattern of barbell trajectory under different barbell mass lifting

Domain wall space-times with a cosmological constant

We solve vacuum Einstein's field equations with the cosmological constant in space-times admitting 3-parameter group of isometries with 2-dimensional space-like orbits. The general exact solutions, which are represented in the advanced and retarded null coordinates, have two arbitrary functions due to the freedom of choosing null coordinates. In the thin-wall approximation, the Israel's junction conditions yield one constraint equation on these two functions in spherical, planar, and hyperbolic domain wall space-times with reflection symmetry. The remain freedom of choosing coordinates are completely fixed by requiring that when surface energy density $\sigma_0$ of domain walls vanishes, the metric solutions will return to some well-known solutions. It leads us to find a planar domain wall solution, which is conformally flat, in the de Sitter universe.Comment: 9 pages. no figur