Tensors versus Matrices, usefulness and unexpected properties

invited KeynoteInternational audienceSince the nineties, tensors are increasingly used in Signal Processing and Data Analysis. There exist striking differences between tensors and matrices, some being advantages, and others raising difficulties. These differences are pointed out in this paper while briefly surveying the state of the art. The conclusion is that tensors are omnipresent in real life, implicitly or explicitly, and must be used even if we still know quite little about their properties