Dr. Tijana Prodanović

University of Novi Sad, Serbia

v ponedeljek, 25. novembra 2013, ob 13h v F5

A discrepancy between primordial lithium abundance predicted by the Big Bang Nucleosynthesis theory, and measurements of pre-galactic lithium abundance in low metallicity systems, has been, for mode than a decade, known as the lithium problem. While measured abundances of other primordial elements are in agreement with their predicted values, lithium in low-metallicity halo stars has been observed to be a factor of 2-4 lower than its expected primordial abundance. No mechanism has been successful in destroying lithium to the observed level so far. Furthermore, the existing lithium problem can become even more severe if any additional pre-galactic source of lithium is present. Possible contaminants could be in the form of cosmic rays that arise during the process of large scale structure formation, or during tidal interactions between galaxies. Gamma-ray observations of the extragalactic gamma-ray background and of galaxy clusters can be used to constrain possible structure-formation cosmic rays and their additional lithium production. On the other hand, measurements of lithium abundance in systems that have recently experienced close fly-bys with neighboring galaxies, such as the Small Magellanic Cloud, can be used to constrain lithium production by tidal cosmic-ray population. Moreover, since lithium has recently been observed in the SMC as its first gas-phase measurement in a low-metallicity system, in order to test the origin of the lithium problem, the importance of determining if lithium was also tidally produced in such system is even greater.