暗能量模型的几何甄别与相空间分析
发布时间：2018-11-27 15:02
【摘要】：近些年来许多天文观测结果表明宇宙正在加速膨胀,科学家们用一种被称为“暗能量”的奇异物质来解释这一现象。暗能量在宇宙中几乎均匀分布,它最大的特点就是压强为负。目前,人们已经建立了各种各样的暗能量模型。 由于暗能量模型越来越多,区别不同的暗能量模型很重要。本文运用几何方法,包括Statefinder和om,甄别纯动能K-essence和LCDM暗能量模型。我们作出平面演化图,发现在68.3%置信区,当时,Statefinder不能区别纯动能K-essence和LCDM暗能量模型。om也被广泛的用来区别不同的暗能量模型,然而本文发现,om不能区别纯动能K-essence和LCDM暗能量模型。 对幂形式的K-essence模型进行了详细的相空间分析,我们发现临界点可以分成三类:临界点不稳定但模型稳定;临界点和模型都稳定;临界点稳定但模型不稳定。根据宇宙学理论,第一种和第三种情况都是没有意义的,尽管可能存在宇宙晚期吸引子。为了研究宇宙最后可能的状态,不仅临界点应是稳定的,模型也应该是稳定的。临界点和模型都稳定也可以分为两种情况,一是宇宙不会出现加速膨胀;另外是宇宙有可能加速,有可能减速,有可能匀速,最后的状态取决与势能。同时,仅仅研究临界点的稳定性是不够的,还必需研究模型的稳定性。
[Abstract]:In recent years, many astronomical observations have shown that the universe is expanding at an accelerated rate, and scientists have interpreted the phenomenon with a strange substance called "dark energy". Dark energy is almost uniformly distributed in the universe, and its greatest feature is that the pressure is negative. At present, various dark energy models have been established. Because there are more and more dark energy models, it is important to distinguish different dark energy models. In this paper, geometric methods are used, including Statefinder and om, to identify pure kinetic energy K-essence and LCDM dark energy models. We made the plane evolution diagram and found that in the 68.3% confidence region, at that time, Statefinder could not distinguish pure kinetic energy K-essence from LCDM dark energy model. Om is also widely used to distinguish different dark energy models. Om cannot distinguish between pure kinetic energy K-essence and LCDM dark energy model. A detailed phase space analysis of the power form K-essence model is carried out. We find that the critical points can be classified into three categories: the critical points are unstable but the model is stable; the critical points and the models are stable; the critical points are stable but the models are unstable. According to cosmology, the first and third cases are meaningless, although there may be late attractors in the universe. In order to study the last possible state of the universe, not only the critical point should be stable, but also the model should be stable. The stability of the critical point and the model can also be divided into two situations, one is that the universe does not appear accelerated expansion, the other is that the universe may accelerate, decelerate, or even, and the final state depends on the potential energy. At the same time, it is not enough to study the stability of the critical point, and it is necessary to study the stability of the model.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：P145.9
[Abstract]:In recent years, many astronomical observations have shown that the universe is expanding at an accelerated rate, and scientists have interpreted the phenomenon with a strange substance called "dark energy". Dark energy is almost uniformly distributed in the universe, and its greatest feature is that the pressure is negative. At present, various dark energy models have been established. Because there are more and more dark energy models, it is important to distinguish different dark energy models. In this paper, geometric methods are used, including Statefinder and om, to identify pure kinetic energy K-essence and LCDM dark energy models. We made the plane evolution diagram and found that in the 68.3% confidence region, at that time, Statefinder could not distinguish pure kinetic energy K-essence from LCDM dark energy model. Om is also widely used to distinguish different dark energy models. Om cannot distinguish between pure kinetic energy K-essence and LCDM dark energy model. A detailed phase space analysis of the power form K-essence model is carried out. We find that the critical points can be classified into three categories: the critical points are unstable but the model is stable; the critical points and the models are stable; the critical points are stable but the models are unstable. According to cosmology, the first and third cases are meaningless, although there may be late attractors in the universe. In order to study the last possible state of the universe, not only the critical point should be stable, but also the model should be stable. The stability of the critical point and the model can also be divided into two situations, one is that the universe does not appear accelerated expansion, the other is that the universe may accelerate, decelerate, or even, and the final state depends on the potential energy. At the same time, it is not enough to study the stability of the critical point, and it is necessary to study the stability of the model.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：P145.9
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