Quantum gravity poses the problem of merging quantum mechanics and general relativity, the two great conceptual revolutions in the physics of the twentieth century. The loop and spinfoam approach, presented in this book, is one of the leading research programs in the field. The first part of the book discusses the reformulation of the basis of classical and quantum Hamiltonian physics required by general relativity. The second part covers the basic technical research directions. Appendices include a detailed history of the (...) subject of quantum gravity, hard-to-find mathematical material, and a discussion of some philosophical issues raised by the subject. This fascinating text is ideal for graduate students entering the field, as well as researchers already working in quantum gravity. It will also appeal to philosophers and other scholars interested in the nature of space and time. (shrink)

The final published book by Nobel Prize-winning author and philosopher Henri Bergson (1859-1941), La pensée et le mouvant (translated here as The Creative Mind), is a masterly autobiography of his philosophical method. Through essays and lectures written between 1903 and 1923, Bergson retraces how and why he became a philosopher, and crafts a fascinating critique of philosophy itself. Until it leaves its false paths, he demonstrates, philosophy will remain only a wordy dialectic that surmounts false problems. With masterful skill and (...) intensity, Bergson shows that metaphysics and science must be rooted in experience for philosophy to become a genuine search for truth. And in the quest for unanswered questions, the spiritual dimension of human life and the importance of intuition must be emphasized. A source of inspiration for physicists as well as philosophers, Bergson's introduction to metaphysics reveals a philosophy that is always on the move, blending man's spiritual drive with his mastery of the material world. (shrink)

On one popular view, the general covariance of gravity implies that change is relational in a strong sense, such that all it is for a physical degree of freedom to change is for it to vary with regard to a second physical degree of freedom. At a quantum level, this view of change as relative variation leads to a fundamentally timeless formalism for quantum gravity. Here, we will show how one may avoid this acute ‘problem of time’. Under our view, (...) duration is still regarded as relative, but temporal succession is taken to be absolute. Following our approach, which is presented in more formal terms in, it is possible to conceive of a genuinely dynamical theory of quantum gravity within which time, in a substantive sense, remains. 1 Introduction1.1 The problem of time1.2 Our solution2 Understanding Symmetry2.1 Mechanics and representation2.2 Freedom by degrees2.3 Voluntary redundancy3 Understanding Time3.1 Change and order3.2 Quantization and succession4 Time and Gravitation4.1 The two faces of classical gravity4.2 Retaining succession in quantum gravity5 Discussion5.1 Related arguments5.2 Concluding remarks. (shrink)

J’étais satisfait, j’avais trouvé quelqu’un qui, comme nous tous, n’avait pas inventé la relativité. Nous avons tous des excuses puisque le grand mathématicien Jacques Hadamard, auteur de l’une des grandes œuvres du XXe siècle, non seulement n’a pas inventé la relativité mais en donne en outre les raisons. Dans cet article au titre attrayant, « Comment je n’ai pas découvert la relativité », du Colloque de philosophie de Naples de 1924, Hadamard...

Résumé Dans les débats métaphysiques contemporains, « endurer » et « perdurer » désignent deux manières irréductibles de persister dans le temps et de subir le changement. Parce qu’ils mobilisent différemment la forme de représentation « espace-temps », ces schèmes conceptuels révèlent peut-être deux figures ou deux aspects du temps lui-même.