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

Dark Matter, Dark Energy and Modern Cosmology: The Case For a Kuhnian Paradigm Shift

Several works in the last few years devoted to measure fundamental probes of contemporary cosmology have suggested the existence of a delocalized dominant component (the "dark energy”), in addition to the several-decade-old evidence for "dark matter” other than ordinary baryons, both assuming the description of gravity to be correct. Either we are faced to accept the ignorance of at least 95 % of the content of the universe or consider a deep change of the conceptual framework to understand the data. Thus, the situation seems to be completely favorable for a Kuhnian paradigm shiftin either particle physics or cosmology. We attempt to offer here a brief discussion of these issues from this particular perspective, arguing that the situation qualifies as a textbook Kuhnian anomaly, and offer a tentative identification of some of the actual elements typically associated with the paradigm shift process "in the works” in contemporary science

Ten Years Of Latin-American Journal Of Astronomy Education RELEA: Achievements And Challenges For International Astronomy Education Development

This study reviews 10 years of Latin-American Journal of Astronomy Education (RELEA), showing that the journal has become a valuable resource for publishing and highlights its pathway as scholarly journal. Furthermore, it is also a call to astronomy education specialists to consolidate their efforts considering similar journals worldwide. Publishing policies of the RELEA and their context are presented in relation to submission, refereeing and publication. The 75 articles published in 18 editions are analyzed and classified. The results showed an acceptance rate of 60.2%; an average of 7.5 articles per year/4.2 per issue. RELEA´s authors are mostly based in Brazil (81.3%); articles target chiefly a school level (university education: 28.0%, high school: 28.0%); their main study focus is learning and teaching (34.7%) and general astronomy content (33.3%). Our results show that compared to other Brazilian journals of education, RELEA had twice as much astronomy articles. In the international scene there has been about a half of astronomy education research, but twice of astronomy in science education research. The challenges related to improve the article submission are discussed: how to increase their number, the submission of Latin American countries, and how to bring in the issues and subjects not addressed until now. It is also encouraged graduate studies, new lines of research in astronomy education, and advertising the journal in universities and schools for professors and teachers. Finally, future possibilities are mentioned given the International Astronomical Union’s development programs

Effects of Gamma Ray Bursts in Earth Biosphere

We continue former work on the modeling of potential effects of Gamma Ray Bursts on Phanerozoic Earth. We focus on global biospheric effects of ozone depletion and show a first modeling of the spectral reduction of light by NO2 formed in the stratosphere. We also illustrate the current complexities involved in the prediction of how terrestrial ecosystems would respond to this kind of burst. We conclude that more biological field and laboratory data are needed to reach even moderate accuracy in this modelingComment: Accepted for publication in Astrophysics & Space Scienc

Strangelet spectra from type II supernovae

We study in this work the fate of strangelets injected as a contamination in the tail of a ‘‘strange matterdriven’’ supernova shock. A simple model for the fragmentation and braking of the strangelets, when they pass through the expanding oxygen shell is presented and solved to understand the reprocessing of this component. We find that the escaping spectrum is a scaled-down version of the one injected at the base of the oxygen shell. The supernova source is likely to produce low-energy particles of A∼100– 1000 quite independently of the initial conditions. However, it is difficult that ultrarrelativistic strangelets (such as the hypothetical Centauro primaries) can have an origin in those explosive events.Facultad de Ciencias Astronómicas y Geofísica