Spatio-temporal Chaos in Systems of Broken Symmetry

这个实验凝聚态物理项目处理气体和流体中出现的非线性现象和模式。研究了耗散模式形成系统中破缺对称性对时空混沌的影响。作为一个原型系统，我们将对大横向范围流体层的对流进行实验研究。首先研究热、剪切驱动失稳共存区域。将特别注意局部湍流爆发及其与剪切流驱动湍流的关系。其次，研究了空间强迫对倾斜层和水平层对流时空混沌的影响。参与该项目的研究生接受基础实验技术培训，如高分辨率数字图像捕获，数字图像处理，精密温度测量和控制技术。此外，研究生将参加康奈尔大学跨学科的NSF非线性系统研究项目。这种培训将使他们为21世纪充满挑战的跨学科工作场所做好准备。这个实验凝聚态物理项目处理气体和流体中出现的非线性现象和模式。有序模式在自然界中无处不在。我们可以在尺度上观察到它们，从几厘米的风吹沙涟漪到几公里的云街道。在这两种情况下，这种模式都是由风或从地球表面上升的热空气推动的。事实上，这样的模式出现在许多驱动系统中。通常，这些模式在空间上是无序的，并且不断变化。我们称这种行为为时空混沌。迄今为止，对时空混沌的统一理解还不存在。然而，对时空混沌的理解是非常重要的，因为它可能导致像心脏颤动和湍流产生这样复杂的系统的控制。我们将研究外部调制如何改变流体对流中的时空混沌和湍流爆发。参与该项目的研究生接受基础实验技术和前沿技术的培训。此外，研究生将参加康奈尔大学跨学科的NSF非线性系统研究项目。这种培训将使他们为21世纪充满挑战的跨学科工作场所做好准备。

This experimental condensed matter physics project deals with non-linear phenomena and patterns appearing in gases and fluids. The research is focused on the influence of broken symmetries on spatio-temporal chaos in dissipative pattern forming systems. As a prototype system the convection of a fluid layer with large lateral extent will be studied experimentally. First the coexistence region between thermal and shear driven instability will be investigated. Special attention will be given to the localized turbulent bursts and their relation to shear flow driven turbulence. Second the influence of spatial forcing on spatio-temporal chaos for convection in inclined and horizontal layers will be studied. Graduate students involved in the project receive training in fundamental experimental techniques, like high resolution digital image capture, digital image processing, precision temperature measurement and control techniques. In addition the graduate students will participate in the Cornell's interdisciplinary NSF IGERT program on Nonlinear Systems. This training will prepare them especially well for the challenging interdisciplinary workplace of the 21st century.%%%This experimental condensed matter physics project deals with non-linear phenomena and patterns appearing in gases and fluids. Ordered patterns are ubiquitous in nature. We can observe them on scales from a few centimeters in the ripples of the windblown sand to kilometers in cloud streets. In both cases the patterns are fueled by wind or by hot air rising from the earth's surface. Indeed such patterns occur in many driven systems. Usually those patterns are disordered in space and are changing constantly. We call such a behavior spatio-temporal chaotic. To date a unifying understanding of spatio-temporal chaos does not exist. However, an understanding of spatio-temporal chaos is very important since it may lead to the control of systems as complex as cardiac fibrillation and the generation of turbulence. We will investigate, how external modulations alter spatio-temporal chaos and turbulent bursts in convection of fluids. Graduate students involved in the project receive training in fundamental experimental techniques and cutting edge technologies. In addition the graduate students will participate in Cornell's interdisciplinary NSF IGERT program on Nonlinear Systems. This training will prepare them especially well for the challenging interdisciplinary workplace of the 21st century.