Entropy Production during Asymptotically Safe Inflation

The Asymptotic Safety scenario predicts that the deep ultraviolet of Quantum Einstein Gravity is governed by a nontrivial renormalization group fixed point. Analyzing its implications for cosmology using renormalization group improved Einstein equations we find that it can give rise to a phase of inflationary expansion in the early Universe. Inflation is a pure quantum effect here and requires no inflaton field. It is driven by the cosmological constant and ends automatically when the renormalization group evolution has reduced the vacuum energy to the level of the matter energy density. The quantum gravity effects also provide a natural mechanism for the generation of entropy. It could easily account for the entire entropy of the present Universe in the massless sector.Comment: 17 pages, 4 figures, Invited contribution to the special issue of Entropy on "Entropy in Quantum Gravity

Inflation in asymptotically safe f(R) theory

We discuss the existence of inflationary solutions in a class of renormalization group improved polynomial f(R) theories, which have been studied recently in the context of the asymptotic safety scenario for quantum gravity. These theories seem to possess a nontrivial ultraviolet fixed point, where the dimensionful couplings scale according to their canonical dimensionality. Assuming that the cutoff is proportional to the Hubble parameter, we obtain modified Friedmann equations which admit both power law and exponential solutions. We establish that for sufficiently high order polynomial the solutions are reliable, in the sense that considering still higher order polynomials is very unlikely to change the solution.Comment: Presented at 14th Conference on Recent Developments in Gravity: NEB 14, Ioannina, Greece, 8-11 Jun 201

Maurice Caruana Curran : guardian of heritage and justice

The cycle of frescoes of Mal Millieri constitutes a unique treasure-house of inestimable value in Malta's cultural heritage. Along with Din l-Art Helwa, the association founded and presided over by him for more than thirty years, Maurice Caruana Curran played a crucial role in the discovery and preservation of this treasure. His role in the discovery and initial measures for the restoration and valorisation of the Annunciation church and its frescoes are dealt with in other contributions in this volume. Because of word limit constraints, I shall also refrain from going into much detail about the excavation which was conducted by Tom Blagg, Anthony Luttrell and myself in the spring of 1977, the conclusion of which might, or might not, have contributed to the change of the state of health of the frescoes. My contribution will dwell on that episode in the history of Din l-Art Helwa's guardianship of the Annunciation Church of Mal Millieri concerning the urgent measures that needed to be taken to preserve this cycle of paintings after a serious alarm was raised on their deterioration. The solutions that were presented to the Association and the solutions it selected reflect the important and fundamental shift that took place at that time concerning the methodology of preservation of fresco painting from one of 'restoration' (including radical intervention) to the current one of 'conservation' (based on minimal intervention and reversibility).peer-reviewe

Solar Dynamo and Toroidal Field Instabilities

The possibility of non-axisimmetric (kink) instabilities of a toroidal field seated in the tachocline is much discussed in the literature. In this work, the basic properties of kink and quasi-interchange instabilities, produced by mixed toroidal and poloidal configuration, will be briefly reviewed. In particular it will be shown that the unstable modes are strongly localized near the Equator and not near the Poles as often claimed in the literature. Based on the results of recent numerical simulations, it is argued that a non-zero helicity can already be produced at a non-linear level. A mean-field solar dynamo is then constructed with a positive $\alpha$-effect in the overshoot layer localized near the Equator and a meridional circulation with a deep return flow. Finally, the possibility that the solar cycle is driven by a $\alpha\Omega$ dynamo generated by the negative subsurface shear in the supergranulation layer will also be discussed.Comment: to appear in Solar Physic

Contextual significance of ritual evidence in Malta

Archaeology has not yet provided us with the proper tools and the right means for reading the minds of our prehistoric ancestors from the material evidence they left us. When and if such means are ever made available, we may rest assured they will be the product of science and technology rather than of archaeology itself. TiII then such a scenario is bound to remain in the realm of wishful thinking and science fiction. With our feet planted firmly in the ground the most we can hope to do, in the meantime, in the field of religious thought, is to try to reconstruct, by using that same material evidence. the rituals through which our ancestors might have expressed their beliefs in the supernatural.peer-reviewe

The Algorithmic Information Content for randomly perturbed systems

In this paper we prove estimates on the behaviour of the Kolmogorov-Sinai entropy relative to a partition for randomly perturbed dynamical systems. Our estimates use the entropy for the unperturbed system and are obtained using the notion of Algorithmic Information Content. The main result is an extension of known results to study time series obtained by the observation of real systems.Comment: 17 pages, 1 figur

Solitons in gauge theories: existence and dependence on the charge

In this paper we review recent results on the existence of non-topological solitons in classical relativistic nonlinear field theories. We follow the Coleman approach, which is based on the existence of two conservation laws, energy and charge. In particular we show that under mild assumptions on the nonlinear term it is possible to prove the existence of solitons for a set of admissible charges. This set has been studied for the nonlinear Klein-Gordon equation, and in this paper we state new results in this direction for the Klein-Gordon-Maxwell system.Comment: 18 pages, proceedings of the "International Workshop on Variational Problems and PDEs", Sao Paulo, September 201

Archaeological fragments and other sources of information

Although the medium I have chosen to discuss, sculpture, is an artistic one and involves by its own nature strong elements of aesthetics and iconography, I shall deal with it also from the archaeological perspective. This distinction between these two disciplines was brought to the fore in my mind by a recent article in an Italian archaeological magazine which commemorated a man who rightly deserves to be considered the founder of ancient Classical art history, namely, Johann Joachim Winkelmann (1717-1767). Winkelmann set down and published the first history of Greco-Roman art in 1764. The authors of the article declared him to be the first archaeologist and to have introduced the archaeological method in the study of ancient art. At first I found this attribution questionable since it is nowhere recorded that he was ever involved in archaeological field work, but then I realized that this attitude is, or was, quite standard in continental academic circles, as opposed to AngloSaxon ones. I should have known better since I had my professional training in both of them, having studied in the lstituto di Archeologia e Storia dell'Arte Antica of the University of Palermo and at the Institute of Archaeology of the University of London.peer-reviewe