标题： quintessence 无标量场 显示英文标题

标题： Quintessence without scalar fields

摘要： 宇宙学中关于 quintessence（宇宙学常数）和宇宙加速膨胀的问题可以在不一定包含标量场的理论框架下讨论。可以通过考虑从基础物理推导出的有效理论（如引力的扩展理论）或者简单地推广物质的状态方程，来定义新组分的压力和能量密度。 在几种方案中可以得到精确的加速膨胀解：要么是在包含高阶曲率和挠率项的模型中，要么是在通过二阶范德瓦尔斯项校正物质状态方程的模型中。 本文综述了这些新方法，并将其与观测结果进行了比较。 显示英文摘要

摘要： The issues of quintessence and cosmic acceleration can be discussed in the framework of theories which do not include necessarily scalar fields. It is possible to define pressure and energy density for new components considering effective theories derived from fundamental physics like the extended theories of gravity or simply generalizing the state equation of matter. Exact accelerated expanding solutions can be achieved in several schemes: either in models containing higher order curvature and torsion terms or in models where the state equation of matter is corrected by a second order Van der Waals terms. In this review, we present such new approaches and compare them with observations.