Dogmatism and Theoretical Pluralism in Modern Cosmology

This work discusses the presence of a dogmatic tendency within modern cosmology, and some ideas capable of neutralizing its negative influence. It is verified that warnings about the dangers of dogmatic thinking in cosmology can be found as early as the 1930's, and we discuss the modern appearance of "scientific dogmatism". The solution proposed to counteract such an influence, which is capable of neutralizing this dogmatic tendency, has its origins in the philosophical thinking of the Austrian physicist Ludwig Boltzmann (1844-1906). In particular we use his two main epistemological theses, scientific theories as representations of nature and theoretical pluralism, to show that once they are embodied in the research practice of modern cosmology, there is no longer any reason for dogmatic behaviours.Comment: 14 pages; LaTeX sourc

Boltzmann's Concept of Reality

In this article we describe and analyze the concept of reality developed by the Austrian theoretical physicist Ludwig Boltzmann. It is our thesis that Boltzmann was fully aware that reality could, and actually was, described by different points of view. In spite of this, Boltzmann did not renounce the idea that reality is real. We also discuss his main motivations to be strongly involved with philosophy of science, as well as further developments made by Boltzmann himself of his main philosophical ideas, namely scientific theories as images of Nature and its consequences. We end the paper with a discussion about the modernity of Boltzmann's philosophy of science.Comment: 13 pages, pdf only. To appear in the book on Ludwig Boltzmann scientific philosophy, published by Nova Science. Edited by A. Eftekhar

A Theory of time-varying Constants

We present a flat (K=0) cosmological model, described by a perfect fluid with the ``constants'' $G,c$ and $\Lambda$ varying with cosmological time $t$. We introduce Planck\'s ``constant'' $\hbar$ in the field equations through the equation of state for the energy density of radiation. We then determine the behaviour of the ``constants'' by using the zero divergence of the second member of the modified Einstein\'s field equations i.e. $div(\frac{G}{c^{4}}T_{i}^{j}+\delta_{i}^{j}\Lambda)=0,$ together with the equation of state and the Einstein cosmological equations. Assuming realistic physical and mathematical conditions we obtain a consistent result with $\hbar c=constant$. In this way we obtain gauge invariance for the Schr\"{o}dinger equation and the behaviour of the remaining ``constants''Comment: 15 pages, RevTeX

Convex separable problems with linear and box constraints

In this work, we focus on separable convex optimization problems with linear and box constraints and compute the solution in closed-form as a function of some Lagrange multipliers that can be easily computed in a finite number of iterations. This allows us to bridge the gap between a wide family of power allocation problems of practical interest in signal processing and communications and their efficient implementation in practice.Comment: 5 pages, 2 figures. Published at IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP 2014

Glass glass transition and new dynamical singularity points in an analytically solvable p-spin glass like model

We introduce and analytically study a generalized p-spin glass like model that captures some of the main features of attractive glasses, recently found by Mode Coupling investigations, such as a glass/glass transition line and dynamical singularity points characterized by a logarithmic time dependence of the relaxation. The model also displays features not predicted by the Mode Coupling scenario that could further describe the attractive glasses behavior, such as aging effects with new dynamical singularity points ruled by logarithmic laws or the presence of a glass spinodal line

Dark energy in motion

Recent large-scale peculiar velocity surveys suggest that large matter volumes could be moving with appreciable velocity with respect to the CMB rest frame. If confirmed, such results could conflict with the Cosmological Principle according to which the matter and CMB rest frames should converge on very large scales. In this work we explore the possibility that such large scale bulk flows are due, not to the motion of matter with respect to the CMB, but to the flow of dark energy with respect to matter. Indeed, when dark energy is moving, the usual definition of the CMB rest frame as that in which the CMB dipole vanishes is not appropriate. We find instead that the dipole vanishes for observers at rest with respect to the cosmic center of mass, i.e. in motion with respect to the background radiation.Comment: 9 pages, 1 figure. Essay selected for "Honorable Mention" in the 2006 Awards for Essays on Gravitation (Gravity Research Foundation

The static potential: lattice versus perturbation theory in a renormalon-based approach

We compare, for the static potential and at short distances, perturbation theory with the results of lattice simulations. We show that a renormalon-dominance picture explains why in the literature sometimes agreement, and another disagreement, is found between lattice simulations and perturbation theory depending on the different implementations of the latter. We also show that, within a renormalon-based scheme, perturbation theory agrees with lattice simulations.Comment: 18 pages, 11 figures, lattice data of Necco and Sommer introduced, references added, some lengthier explanations given, physical results unchange

Dissociating the Role of the Orbitofrontal Cortex and the Striatum in the Computation of Goal Values and Prediction Errors

To make sound economic decisions, the brain needs to compute several different value-related signals. These include goal values that measure the predicted reward that results from the outcome generated by each of the actions under consideration, decision values that measure the net value of taking the different actions, and prediction errors that measure deviations from individuals' previous reward expectations. We used functional magnetic resonance imaging and a novel decision-making paradigm to dissociate the neural basis of these three computations. Our results show that they are supported by different neural substrates: goal values are correlated with activity in the medial orbitofrontal cortex, decision values are correlated with activity in the central orbitofrontal cortex, and prediction errors are correlated with activity in the ventral striatum