Studies of Classical and Quantum Effects in Gravity

重力的经典效应和量子效应研究

• 批准号: 0556292
• 负责人: Paul Anderson
• 金额: $ 6.34万
• 依托单位: Wake Forest University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-15 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0556292&HistoricalAwards=false
• 关键词: Studies; Classical; Quantum; Effects; Gravity

This award supports several projects which involve studying quantum effects as they relate to both cosmology and black holes. The same techniques will be used to compute the force a particle feels due to the gravitational radiation that is emitted as it orbits a black hole. One of the most important ideas in cosmology today is that early in its history the universe underwent a process of extremely rapid expansion called inflation. Quantum effects were very important both during and shortly after this period of inflation. They are almost always computed using an approximation to quantum field theory called the semiclassical approximation. The validity of this approximation as it relates to the period of inflation and to particle production that occurs immediately after this period will be investigated. In addition, studies will be made of the effects that quantum fields have on the event horizons of black holes. The event horizon is the boundary in space between where light can get away from the black hole and where it cannot. A study will also be made of the difference between the effects quantum fields have on the geometry far from the event horizon of a black hole versus the effects they have on the geometry far from the surface of a static star. When a particle orbits a black hole gravitational radiation is emitted whose effect can change the subsequent orbit. If the particle is charged electromagnetic radiation is also emitted. These can be modeled by using a simpler type of radiation called scalar radiation. Projects will be worked on that involve the computation of the force this scalar radiation exerts on a particle as it orbits a black hole.Some of the most important predictions of inflation including the creation of density fluctuations that eventually evolve into galaxies depend on quantum effects which are computed using semiclassical approximations. It is thus extremely important to determine whether these approximations are valid both during and immediately after inflation. If calculations for reheating in some chaotic inflation scenarios are invalidated, then much more difficult calculations will be necessary. In the case of black holes there are indications that there are special cases where it is possible that quantum effects might have such a significant effect on the event horizon of the black hole that they prevent that type of black hole from existing. It is not clear how likely it is that this will happen but it is important to investigate whether or not it does happen. One of the important sources of gravitational waves for the proposed space based gravitational wave detector called LISA is a neutron star or black hole formed from the collapse of a star which orbits a supermassive black hole at the center of a galaxy. The detailed nature of the waves emitted depend upon the trajectory of the orbiting body. This in turn depends on the force that the emitted gravitational radiation emits on the orbiting body. Thus it is very important to compute this force. It will be possible to involve both undergraduate and graduate students in many of these projects. There is along history of undergraduate and graduate students working on these types of projects and gaining training in both numerical and analytical research techniques as well as being coauthors on publications.

该奖项支持几个涉及研究量子效应的项目，因为它们与宇宙学和黑洞有关。同样的技术将被用于计算粒子在绕黑洞运行时因引力辐射而产生的力。当今宇宙学中最重要的观点之一是，在其历史的早期，宇宙经历了一个被称为暴胀的极其迅速的膨胀过程。量子效应在暴胀期间和之后不久都非常重要。它们几乎总是使用量子场论的近似计算，称为半经典近似。这个近似的有效性，因为它涉及到膨胀周期和粒子产生后，将进行研究。此外，还将研究量子场对黑洞视界的影响。视界是光可以离开黑洞和不能离开黑洞的空间边界。还将研究量子场对远离黑洞视界的几何形状的影响与它们对远离静态恒星表面的几何形状的影响之间的差异。当粒子绕黑洞运行时，会发出引力辐射，其影响可以改变随后的轨道。如果粒子带电，也会发射电磁辐射。这些可以用一种更简单的辐射——标量辐射来模拟。将进行的项目涉及计算标量辐射在粒子绕黑洞运行时对粒子施加的力。一些最重要的暴胀预测，包括最终演化成星系的密度波动的产生，都依赖于使用半经典近似计算的量子效应。因此，确定这些近似在暴胀期间和暴胀之后是否有效是极其重要的。如果在一些混乱的暴胀情景中重新加热的计算是无效的，那么将需要更困难的计算。在黑洞的情况下，有迹象表明，在某些特殊情况下，量子效应可能对黑洞的视界产生如此重大的影响，以至于它们阻止了这种类型的黑洞的存在。目前尚不清楚这种情况发生的可能性有多大，但调查这种情况是否会发生是很重要的。对于拟建的空间引力波探测器LISA来说，引力波的重要来源之一是中子星或黑洞，它是由一颗围绕星系中心的超大质量黑洞运行的恒星坍缩形成的。发射波的具体性质取决于绕轨道运行的天体的轨道。这反过来又取决于所发射的引力辐射对轨道天体所发射的力。因此计算这个力是非常重要的。在这些项目中，本科生和研究生都有可能参与。本科生和研究生从事这些类型的项目，并在数值和分析研究技术方面获得培训，以及成为出版物的合著者，这是一个悠久的历史。