Free will, the self and the brain

The free will problem is defined and three solutions are discussed: no-freedom theory, libertarianism, and compatibilism. Strict determinism is often assumed in arguing for libertarianism or no-freedom theory. It assumes that the history of the universe is fixed, but modern physics admits a certain degree of randomness in the determination of events. However, this is not enough for a compatibilist position—which is favored here—since freedom is not randomness. It is the I that chooses what to do. It is argued that the core of the free will problem is what this I is. A materialist view is favored: The I is an activity of the brain. In addition to absence of external and internal compulsion, freedom involves absence of causal sufficiency of influences acting on the I. A more elaborate compatibilist view is proposed, according to which causal determination is complete when we add events occurring in the I (of which the subject is not conscious). Contrary to what several authors have argued, the onset of the readiness potential before the decision to act is no problem here. The experience of agency is incomplete and fallible, rather than illusory. Some consequences of different views about freedom for the ascription of responsibility are discussed

pi pi scattering, pion form factors and chiral perturbation theory

I discuss recent progress in our understanding of the pi pi scattering amplitude at low energy thanks to the combined use of chiral perturbation theory and dispersion relations. I also comment on the criticism raised by Pelaez and Yndurain on this work.Comment: 10 pages, 5 figures. Invited talk at the "Quark Confinement and the Hadron Spectrum" VI Conference, Villasimius, Sardinia, Italy, 21-25 September 200

Theoretical progress on pi pi scattering lengths and phases

pi pi scattering at low energy is sensitive to the structure of the QCD vacuum. I review the calculations of the pi pi scattering lengths and phases, and group them in three cathegories: 1. those based on very general theoretical constraints (like dispersion relations and crossing symmetry) and phenomenology, 2. those which in addition make explicit use of chiral symmetry, 3. the first-principle ones, done with lattice QCD. I then compare these to the experimental results. Thanks to recent progress in all these and in the experimental determination of the scattering lengths we are improving substantially our knowledge of the QCD vacuum.Comment: 11 pages, talk given at the KAON International Conference, May 21-25 2007 Laboratori Nazionali di Frascati dell'INFN, Rome, Ital

Interpretation and reduction of attribute grammars

An attribute grammar (AG) is in reduced form if in all its derivation trees every attribute contributes to the translation. We prove that, eventhough AG are generally not in reduced form, they can be reduced, i.e., put into reduced form, without modifying their translations. This is shown first for noncircular AG and then for arbitrary AG. In both cases the reduction consists of easy (almost syntactic) transformations which do not change the semantic domain of the AG. These easy transformations are formalized by introducing the notion of AG interpretation as an extension to AG of the concept of context-free grammar form. Finally we prove that any general algorithm for reducing even the simple class of L-AG needs exponential time (in the size of the input AG) infinitely often