15,234 research outputs found

    Quantum-mechanical effects in a linear time-dependent potential

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    The solution of the time-dependent Schr\"odinger equation is discussed for a particle confined in half-space x>0x>0 with a linear potential V(x)=KxV(x)=Kx in the following situations: (a) sudden removal of the wall and switching on the linear potential V(x)=KxV(x)=Kx at x≤0x \leq 0, (b) sudden removal of the wall and the potential and (c) sudden removal of the potential. A brief discussion of the quantum statistic is presented.Comment: 9 pages, 6 figure

    On the stability of Einstein static universe at background level in massive bigravity

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    We study the static cosmological solutions and their stability at background level in the framework of massive bigravity theory with Friedmann-Robertson-Walker (FRW) metrics. By the modification proposed in the cosmological equations subject to a perfect fluid we obtain new solutions interpreted as the Einstein static universe. It turns out that the non-vanishing size of initial scale factor of Einstein static universe depends on the non-vanishing three-dimensional spatial curvature of FRW metrics and also the graviton's mass. By dynamical system approach and numerical analysis, we find that the extracted solutions for closed and open universes can be stable for some viable ranges of equation of state parameter, viable values of fraction of two scale factors, and viable values of graviton's mass obeying the hierarchy m<<MPlm << M_Pl which is more cosmologically motivated.Comment: 14 pages, 8 figures, 5 tables, major revisio

    Vacuum spherically symmetric solutions in f(T)f(T) gravity

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    Spherically symmetric static vacuum solutions have been built in f(T)f(T) models of gravity theory. We apply some conditions on the metric components; then the new vacuum spherically symmetric solutions are obtained. Also, by extracting metric coefficients we determine the analytical form of f(T)f(T).Comment: 8 pages,typos corrected, Refs. adde
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