743 research outputs found

    Liquid-Droplet as a model for the rotation curve problem

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    The dynamics of large scale gravitational structures like galaxies, local groups and clusters is studied based on the so-called {\it Liquid-Droplet} model describing the saturation property of the nuclear force. Using the assumption that the gravitational force is also saturated over large scale structures, it is argued that the Newtonian gravitational potential may be replaced by an effective {\it Machian} gravitational potential. Application of this new potential at these large scale structures may give the rotation curves in good agreement with observations. Then, the virial theorem for this kind of gravitational interaction is developed and also the Tully-Fisher relation is obtained. A physical explanation is given for the so-called {\it constant} acceleration in the MOND as the {\it effective} gravitational strength of these structures. Finally, a brief argument is given for comparison with dark matter models.Comment: 14 pages, major revisio

    Classical and quantum wormholes in a 5D compact Kaluza-Klein theory

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    We study the classical and quantum Euclidean wormholes for an empty (4+1) dimensional Kaluza-Klein universe with a positive cosmological constant and a spatially flat Robertson-Walker type metric. It is shown that classical wormholes do not exist neither for the spacetime sector nor the extra dimensional sector of this model, but two spectrums of quantum wormholes as the solutions of Wheeler-DeWitt equation exist which are consistent with the Hawking-Page conjecture about the necessary boundary conditions. In the spectrum where the external scale factor RR shapes the quantum wormholes the internal scale factor aa may play the role of effective matter source, and in the spectrum where the internal scale factor aa shapes the quantum wormholes the external scale factor RR may play the role of effective matter source.Comment: 10 pages, Major revisio