Strange quark matter fragmentation in astrophysical events

The conjecture of Bodmer-Witten-Terazawa suggesting a form of quark matter (Strange Quark Matter) as the ground state of hadronic interactions has been studied in laboratory and astrophysical contexts by a large number of authors. If strange stars exist, some violent events involving these compact objects, such as mergers and even their formation process, might eject some strange matter into the interstellar medium that could be detected as a trace signal in the cosmic ray flux. To evaluate this possibility, it is necessary to understand how this matter in bulk would fragment in the form of strangelets (small lumps of strange quark matter in which finite effects become important). We calculate the mass distribution outcome using the statistical multifragmentation model and point out several caveats affecting it. In particular, the possibility that strangelets fragmentation will render a tiny fraction of contamination in the cosmic ray flux is discussed.Comment: 13 pages, 4 figure

Interaction of strangelets with ordinary nuclei

Strangelets (hypothetical stable lumps of strange quarkmatter) of astrophysical origin may be ultimately detected in specific cosmic ray experiments. The initial mass distribution resulting from the possible astrophysical production sites would be subject to reprocessing in the interstellar medium and in the earth's atmosphere. In order to get a better understanding of the claims for the detection of this still hypothetic state of hadronic matter, we present a study of strangelet-nucleus interactions including several physical processes of interest (abrasion, fusion, fission, excitation and de-excitation of the strangelets), to address the fate of the baryon number along the strangelet path. It is shown that, although fusion may be important for low-energy strangelets in the interstellar medium (thus increasing the initial baryon number A), in the earth's atmosphere the loss of the baryon number should be the dominant process. The consequences of these findings are briefly addressed

Nucleosynthesis in Strange Star Mergers

The possible existence of deconfined matter in the cores of neutron stars has been studied for over three decades without a firm indication either for or against this proposition. Analysis mostly rely on the comparison of mass-radius curves obtained for different compositions with observational data on the mass of the most massive objects of this kind accurately determined. Nevertheless, there are other possibilities for indirectly studying the internal composition of this class of compact objects, e.g, analyzing cooling behavior, X-ray bursts, supernova’s neutrinos. We present calculations on the expected nucleosynthesis spectra for the strange star-strange star merger scenario as means to test the strange quark matter hypothesis and its realization inside such objects. This would result very different from the typical r-process nucleosynthesis expected in neutron star mergers since the high temperature deconfinement of strange matter would produce large amounts of neutrons and protons and the mass buildup would proceed in a Big-Bang nucleosynthesis like scenario. The neutron to proton ratio would allow to reach the iron peak only, a very different prediction from the standard scenario. The resultant light curve indicate it may be compatible with that of a kilonova depending on the specific details of the ejecta.Facultad de Ciencias Astronómicas y Geofísica

Tidal deformability of strange stars and the GW170817 event

In this work we consider strange stars formed by quark matter in the color-flavor-locked (CFL) phase of color superconductivity. The CFL phase is described by a Nambu-Jona-Lasinio model with four-fermion vector and diquark interaction channels. The effect of the color superconducting medium on the gluons are incorporated into the model by including the gluon self-energy in the thermodynamic potential. We construct parametrizations of the model by varying the vector coupling GV and comparing the results to the data on tidal deformability from the GW170817 event, the observational data on maximum masses from massive pulsars such as the MSP J0740+6620, and the mass/radius fits to NICER data for PSR J003+0451. Our results point out to windows for the GV parameter space of the model, with and without gluon effects included, that are compatible with all these astrophysical constraints, namely, 0.2

Magnetic color-flavor-locked stars

Using the solutions of the gap equations of the magnetic-color-flavor-locked (MCFL) phase of paired quark matter in a magnetic field, and taking into consideration the separation between the longitudinal and transverse pressures due to the field-induced breaking of the spatial rotational symmetry, the equation of state (EoS) of the MCFL phase is self-consistently determined. Implications for stellar models of magnetized (self-bound) strange stars and hybrid (MCFL core) stars are discussed.FAPESPCNPqOffice of Nuclear Theory of the Department of Energy de-sc000217

Quality of life of medicine students in the pandemic: a prospective observational cross-sectional study

The COVID-19 pandemic has had major impacts on the mental and psychological health of young students. Stress, anxiety, depression, and a sedentary lifestyle are some of the consequences generated during the necessary social isolation. In this way, medical education has transformed due to the current Covid 19 epidemic, which has affected students and teachers of medical education in the country. In this way, the present research intends to collect data to evaluate the affected areas of the students in terms of quality of life, health, and other areas of their lives, thus being able to bring new information that can be used for a better approach to the theme. Therefore, this study evaluated the quality of life of medical students during the pandemic through the application of a remote questionnaire

Teaching astronomy : a didactic approach based on the Theory of General Relativity

A partir da análise de uma articulação entre as perspectivas cognitivistas da aprendizagem significativa de David Ausubel e educacionais das comunidades de investigação presentes no programa de filosofia de Matthew Lipman, este artigo discute o desenvolvimento de um produto educacional acerca de tópicos de astronomia. A aplicação foi feita em uma turma do terceiro ano do ensino médio da rede pública do Distrito Federal. As aulas foram distribuídas em quatro grandes temas: gravitação universal e sistema solar; relatividade geral; buracos negros; e lentes gravitacionais. Conteúdos, atividades e abordagens diversificados foram mediados por tecnologias educacionais digitais e as avaliações consideraram a proficiência como níveis de expressão das respectivas teorias psicológica e educacional. Os resultados revelaram o entusiasmo e interesse dos estudantes pelos temas propostos. Também foi possível verificar indicadores do desenvolvimento de habilidades de raciocínio, formação de conceitos, investigação, tradução e indícios de aprendizagem significativa. Por fim, foi possível concluir que a inserção de temas ligados `a astronomia e `a física moderna e contemporânea são viáveis no ensino médio, mesmo no contexto precário da escola pública, em contraposição ao currículo atual de física, desgastado e baseado principalmente na física clássica e em abordagens metodológicas muitas vezes difusas.From the analysis of an articulation between the cognitive perspectives of David Ausubel’s meaningful learning and the educational ones of the research communities present in Matthew Lipman’s philosophy program, this article discusses the development of an educational product on astronomy topics. The application was made in a third-year class of public high school in the Federal District. The classes were divided into four major themes: universal gravitation and the solar system; general relativity; black holes; and gravitational lenses. Diversified content, activities and approaches were mediated by digital educational technologies and the evaluations considered proficiency as levels of expression of the respective psychological and educational theories. The results revealed the students’ enthusiasm and interest in the proposed themes. It was also possible to verify indicators of the development of reasoning skills, concept formation, investigation, translation, and evidence of significant learning. Finally, it was possible to conclude that the insertion of themes related to astronomy and modern and contemporary physics are viable in high school, even in the precarious context of the public school, in contrast to the current physics curriculum, worn out and based mainly on classical and methodological approaches that are often diffuse