Monopole abundance from first-order GUT phase transition of the early Universe

Monopole annihilation and pair creation are investigated in a first order GUT symmetry breaking phase transition without inflation. It is found that even with complete initial monopole suppression, some monopoles are inevitably produced during the transition. According to this, some constraints are obtained for initial and equilibrium monopole densities in order to be compatible with the present observational limits even without inflation.     

Classifying GRB 170817A/GW170817 in a Fermi duration–hardness plane

GRB 170817A, associated with the LIGO-Virgo GW170817 neutron-star merger event, lacks the short duration and hard spectrum of a Short gamma-ray burst (GRB) expected from long-standing classification models. Correctly identifying the class to which this burst belongs requires comparison with other GRBs detected by the Fermi GBM. The aim of our analysis is to classify Fermi GRBs and to test whether or not GRB 170817A belongs—as suggested—to the Short GRB class. The Fermi GBM catalog provides a large database with many measured variables that can be used to explore gamma-ray burst classification. We use statistical techniques to look for clustering in a sample of 1298 gamma-ray bursts described by duration and spectral hardness. Classification of the detected bursts shows that GRB 170817A most likely belongs to the Intermediate, rather than the Short GRB class. We discuss this result in light of theoretical neutron-star merger models and existing GRB classification schemes. It appears that GRB classification schemes may not yet be linked to appropriate theoretical models, and that theoretical models may not yet adequately account for known GRB class properties. We conclude that GRB 170817A may not fit into a simple phenomenological classification scheme.     

Putting together the pieces of the puzzle: Traces of New Zealand in international school geography textbooks

How does a fairly remote space (the islands of New Zealand) contribute to the development of geographical literacy in the geography textbooks of post‐socialist (Romania), Western (Germany) and post‐colonial (Mexico) countries? A four‐step analysis of three textbooks of international selection revealed different regionalisation cultures combined with traditional and recently implemented educational paradigms of geography education and led to a similar result. Despite the many ways in which New Zealand's geographical distinctiveness could be used to enhance geographical literacy, there are few operationalisations of educational targets that might contribute to sustainable long‐term learning. Further, these results also offer a possible explanation for the absence of the ‘southern lands’ on students' cognitive maps of the world.     

Is sky distribution of gamma-ray bursts random?

We investigate the full randomness of the angular distribution of gamma-ray bursts (GRBs) detected by the BATSE (the Burst and Transient Source Experiment). We divided the BATSE sample into 5 subsamples (short1, short2, intermediate, long1, long2 based on their durations and peak fluxes and studied the angular distributions separately. We used three methods, the Voronoi tesselation, minimal spanning tree and multifractal spectra to search for non-randomness in the subsamples. To investigate the eventual non-randomness in the subsamples we defined 13 test-variables (9 from the Voronoi tesselation, 3 from the minimal spanning tree and one from the multifractal spectrum). We performed Monte Carlo simulations taking into account the BATSE sky-exposure function. We tested the randomness by introducing squared Euclidean distances in the parameter space of the test-variables. We concluded that the short1, short2 groups deviate significantly (99.90%, 99.98%) from the full randomness in the distribution of the squared Euclidean distances, however, it is not the case with the long subsamples. In the intermediate group, the squared Euclidean distances also yield a significant deviation (98.51%).     

Exploration of the high-redshift universe enabled by THESEUS

Experimental Astronomy - At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer...