The take-over of the philosophy of mathematics by mathematical logic is not complete. The central problems examined in this book lie in the fringe area between the two, and by their very nature will no doubt continue to fall partly within the philosophical re­ mainder. In seeking to treat these problems with a properly sober mixture of rhyme and reason, I have tried to keep philosophical jargon to a minimum and to avoid excessive mathematical compli­ cation. The reader with a philosophical background should be familiar with the formal syntactico-semantical explications of proof and truth, especially if he wishes to linger on Chapter 1, after which it is easier philosophical sailing; while the mathematician need only know that to "explicate" a concept consists in clarifying a heretofore vague notion by proposing a clearer (sometimes formal) definition or formulation for it. More seriously, the interested mathematician will find occasional recourse to EDWARD'S Encyclopedia of Philos­ ophy (cf. bibliography) highly rewarding. Sections 2. 5 and 2. 7 are of interest mainly to philosophers.

This book provides a comprehensive analysis of the existence of weak solutions of unsteady problems with variable exponents. The central motivation is the weak solvability of the unsteady p(.,.)-Navier–Stokes equations describing the motion of an incompressible electro-rheological fluid. Due to the variable dependence of the power-law index p(.,.) in this system, the classical weak existence analysis based on the pseudo-monotone operator theory in the framework of Bochner–Lebesgue spaces is not applicable. As a substitute for Bochner–Lebesgue spaces, variable Bochner–Lebesgue spaces are introduced and analyzed. In the mathematical framework of this substitute, the theory of pseudo-monotone operators is extended to unsteady problems with variable exponents, leading to the weak solvability of the unsteady p(.,.)-Navier–Stokes equations under general assumptions.

This expanded second edition of Relativity and the Nature of Spacetime c- tains several major changes and a number of additions to different ch- ters. Two chapters (Chaps. 6 and 7), which discussed two speci?c groups of arguments against the reality of spacetime, have been transformed into - pendices (A and B). Two new chapters (Chaps. 6 and 10) have been added. Chapter 6, entitled Why Is the Issue of the Nature of Spacetime So Imp- tant?, elaborates on what was Sect. 5. 6 of the ?rst edition, and addresses some recent work on the nature of spacetime – for example, the growing (or evolving) block universe model of the world, which has recently been - vived by several physicists as what appears to be the last remaining alter- tive to the Minkowski absolute four-dimensional world (after it had become an undeniable fact that three-dimensionalism, or presentism, contradicts the relativistic experimental evidence). Chapter 10, entitled Spacetime and the Nature of Quantum Objects and based on what used to be Sects. 6. 2 and 6. 3 in the ?rst edition, explores the implications of the issue of the nature of spacetime for quantum physics, in order to see whether it can provide some insight into the nature of quantum objects. Two new sections have been included, namely, Sect. 5. 6 entitled Re- tivization of Existence and Observers in General Relativity and Sect. 7. 6 - titled Probing the Anisotropic Velocity of Light by a Terrestrial Experiment.