SEMINAR       Monday, 13th October 2003 - h. 14:30  Aula Seminari (A34)     Prof. Sanjeev Dhurandhar IUCAA (Pune, India)        "Algebraic Structures Underlying LISA data analysis"           Abstract LISA consists of three freely flying space-craft forming a giant interferometric triangle each arm being 5 million kilometres in length. The purpose of LISA is to detect low frequency gravitational wave radiation. Cancellation of laser frequency noise is crucial for LISA attaining the requisite sensitivity. In this seminar, a scheme based on commutative algebra will be described which gives all the data combinations cancelling laser frequency noise. The scheme can be used to cancel some other systematic noises as well. Having access to all such data combinations has many potential applications. We use it to optimise the signal-to-noise for nearly  monochromatic sources and also to optimise the directional sensitivity for such sources by tracking the source by switching the data combinations optimally.