arXiv subjects

Marcelo Byrro Ribeiro

Publications and source records attributed to Marcelo Byrro Ribeiro.

4 recordsLinked to original sources

arXiv2022

Theory assessment and reality in Boltzmann's epistemological thinking

This paper discusses how theories can be assessed within the epistemological viewpoint advanced by the Austrian physicist Ludwig E. Boltzmann. It builds upon, and further develops, the perspective of Boltzmann's thinking as advanced by Ribeiro and Videira (1998, arXiv:physics/9806011). Boltzmann's epistemological viewpoint accepts that reality is real and proposes that reality can be described by different points of view because his main philosophical thesis states that scientific theories are images of Nature. We present the historical context that witnessed the genesis of Boltzmann's ideas and expand Ribeiro and Videira's (Ibid.) perspective by arguing that later in his life Boltzmann realized the insufficiency of his thesis as justification for theoretical pluralism and avoidance of dogmatism. Consequently, his thinking went beyond epistemology, the nature of scientific knowledge, to include realism, the nature of the represented objects.

physics.hist-ph↗

arXiv2021

Testing cosmological models with the brightness profile of distant galaxies

This work uses observed galaxy surface brightness profiles at high redshifts to determine the cosmological model best suited to interpret these observations. Theoretical predictions of galactic surface brightness profiles are compared to observational data in two cosmological models, $Λ$CDM and Einstein-de Sitter, to calculate the evolutionary effects of different spacetime geometries in these profiles in order to try to find out if the available data is capable of indicating the cosmology that best represents actual galactic brightness profiles observations. Starting from the connection between the angular diameter distance and the galactic surface brightness as advanced by Ellis and Perry (1979), we derived scaling relations using data from the Virgo galactic cluster in order to obtain theoretical predictions of the galactic surface brightness modeled by the Sersic profile at redshift values equal to a sample of galaxies in the range $1.5 \lesssim z \lesssim 2.3$ composed by a subset of Szomoru's et al. (2012) observations. We then calculated the difference between theory and observation in order to determine the changes required in the effective radius and effective surface brightness so that the observed galaxies may evolve to have features similar to the Virgo cluster ones. Our results show that within the data uncertainties of this particular subset of galaxies it is not possible to distinguish which of the two cosmological models used here predicts theoretical curves in better agreement with the observed ones, that is, one cannot identify a clear and detectable difference in galactic evolution incurred by the galaxies of our sample when applying each cosmology. We also concluded that the Sersic index $n$ does not seem to play a significant effect in the evolution of these galaxies.

astro-ph.CO↗

arXiv2021

Bianchi VI0 viscous fluid cosmology with magnetic field

A spatially homogeneous Bianchi type VI0 model containing a viscous fluid in the presence of an axial magnetic field has been studied. A barotropic equation of state together with a pair of linear relations among the square root of matter density, shear scalar, and expansion scalar have been assumed. Solutions are obtained in the presence of a magnetic field, only in two special cases, which are comparatively simpler. The complete solutions for this model in the absence of a magnetic field are also obtained. The presence of a magnetic field in the former case however, does not in effect cause any major modification in the fundamental nature of the initial singularity of the expanding model.

gr-qc↗

arXiv2013

Cosmologia e Representação

This work presents a brief and non-technical description of the main results and concepts of the modern scientific cosmology, viewing it from an epistemological perspective which allows a dialog with other modes of thinking like e.g. history, philosophy, sociology and religion. This epistemological viewpoint is based on the philosophical theses advanced by Ludwig Boltzmann (1844-1906) which states that scientific theories are nothing more than representations, or images, of nature (arXiv:physics/0701308v1). By being representations one cannot know how nature really is because the intrinsic and indispensable properties that characterize nature are unreachable by science. In other words, the true essences that constitute nature are unknowable. Therefore, all answers proposed by science are partial, simplified and replaceable. Another way of putting forward this viewpoint is to state that all scientific truths are provisional, a result which naturally leads to the conclusion that the same set of phenomena, or scientific questions, may have various answers, or representations. This conclusion is generally known as theoretical pluralism (arXiv:physics/9806011). It is exactly such a plurality for conceiving, or representing, nature that opens the way for a possibly fruitful dialog among the various forms of thinking, since this dialog can take place in the realm of the representations. A few examples taken from cosmology, sociology and theology are discussed in the context of this epistemological framework.

physics.hist-ph↗