Cylindrical solutions in braneworld gravity

In this article we investigate exact cylindrically symmetric solutions to the modified Einstein field equations in the brane world gravity scenarios. It is shown that for the special choice of the equation of state $2U+P=0$ for the dark energy and dark pressure, the solutions found could be considered formally as solutions of the Einstein-Maxwell equations in 4-D general relativity.Comment: 12 pages, RevTex format, typos corrected and references added. Accepted for publication in PR

Tetrads in Geometrodynamics

A new tetrad is introduced within the framework of geometrodynamics for non-null electromagnetic fields. This tetrad diagonalizes the electromagnetic stress-energy tensor and allows for maximum simplification of the expression of the electromagnetic field. The Einstein-Maxwell equations will also be simplified

Sifat-sifat Quasi-ideal-γ Pada Semigrup-γ

Semigrup-Г S merupakan generalisasi dari semigrup. Semigrup- Г S adalah semigrup yang memuat pemetaan S×Г×S→S , yaitu (a ,γ,b) ↦aγb∈S dan memenuhi aγbμc=aγbμc untuk semua a,b,c∈S dan γ,μ∈Г . Quasi-ideal- Г Q dimana Q merupakan himpunan bagian tak kosong dari semigrup- Г S disebut quasi-ideal-Г Q jika SГQ∩QГS⊆Q . Irisan dari semua quasi-ideal-Г Q yang memuat A dengan A merupakan himpunan bagian dari semigrup- Г S , sehingga quasi-ideal- Г Q merupakan quasi-ideal-Г Q terkecil yang memuat A

Purely electromagnetic spacetimes

Electrovacuum solutions devoid of usual mass sources are classified in the case of one, two and three commuting Killing vectors. Three branches of solutions exist. Electromagnetically induced mass terms appear in some of them.Comment: 8 page

A new time-machine model with compact vacuum core

We present a class of curved-spacetime vacuum solutions which develope closed timelike curves at some particular moment. We then use these vacuum solutions to construct a time-machine model. The causality violation occurs inside an empty torus, which constitutes the time-machine core. The matter field surrounding this empty torus satisfies the weak, dominant, and strong energy conditions. The model is regular, asymptotically-flat, and topologically-trivial. Stability remains the main open question.Comment: 7 page

PENYELESAIAN SENGKETA DI PERBANKAN SYARIAH KHUSUSNYA PEMBIAYAAN AKAD MURABAHAH

Title disputes in Islamic banking, especially in murabaha financing agreement. The purpose of this study was to determine the development of the Islamic banking law in the world, especially in financing murabaha contract, thus standardizing contracts particularly in dispute resolution will ensure legal protection and legal certainty in every transaction made and can be used as a reference in the resolution that appears in the cult. Types of research used in this study is a normative legal research, legislation and approach of this study requires secondary data (material law) primary data, and tertiary legal materials to equip.Data used consists of primary legal materials are materials that consist of laws and regulations applicable to the problem under study. Secondary legal materials or literature consists of books, articles, working in the legal field, magazines, and materials related to the study of law. Tertiary legal materials legal materials that explain the legal materials of primary and secondary legal materials, the use of Indonesian dictionary. Results from this study is for those who aspire to conduct transactions in Islamic banking, especially in murabaha financing agreement must meet the requirements of Islamic law. In view of the scholars, the general power of attorney is not justified because it does not meet the requirements in harmony and power. This can lead wakalah contract null and void. When the lifeboat issue in accordance with the provisions of Law No. 21 of 2008 outlines the settlement of disputes in accordance with the Treaty

Comparison of CFD and DSMC Using Calibrated Transport Parameters

Hypersonic re-entry flows span a wide range of length scales where regions of both rarefied and continuum flow exist. Traditional computational fluid dynamics (CFD) techniques do not provide an accurate solution for the rarefied regions of such mixed flow fields. Although direct simulation Monte Carlo (DSMC) can be used to accurately capture both the continuum and rarefied features of mixed flow fields, they are computationally expensive when employed to simulate the low Knudsen number continuum regimes. Thus, a hybrid framework for seamlessly combining the two methodologies, CFD and DSMC, continues to be a topic of significant research effort. Ensuring consistency in the reaction kinetics and transport models employed within CFD and DSMC is a crucial requirement for obtaining a reliable solution from a hybrid framework for combined continuum/rarefied high speed flows. This paper represents one of the first studies to utilize the calibrated transport parameters developed to ensure consistency between CFD and DSMC solvers. The new variable soft sphere (VSS) parameters are compared to both previous standard variable hard sphere (VHS) parameters and also to solutions from the CFD transport properties that the new parameters were developed to reproduce

Noncommutative Einstein-Maxwell pp-waves

The field equations coupling a Seiberg-Witten electromagnetic field to noncommutative gravity, as described by a formal power series in the noncommutativity parameters $\theta^{\alpha\beta}$, is investigated. A large family of solutions, up to order one in $\theta^{\alpha\beta}$, describing Einstein-Maxwell null pp-waves is obtained. The order-one contributions can be viewed as providing noncommutative corrections to pp-waves. In our solutions, noncommutativity enters the spacetime metric through a conformal factor and is responsible for dilating/contracting the separation between points in the same null surface. The noncommutative corrections to the electromagnetic waves, while preserving the wave null character, include constant polarization, higher harmonic generation and inhomogeneous susceptibility. As compared to pure noncommutative gravity, the novelty is that nonzero corrections to the metric already occur at order one in $\theta^{\alpha\beta}$.Comment: 19 revtex pages. One refrence suppressed, two references added. Minor wording changes in the abstract, introduction and conclusio