Constant entropy hybrid stars: a first approximation of cooling evolution

We aim to study the possibility of a hadron-quark phase transition in the interior of neutron stars, taking into account different schematic evolutionary stages at finite temperature. We also discuss the strange quark matter stability in the quark matter phase. Furthermore, we aim to analyze the astrophysical properties of hot and cold hybrid stars, considering the constraint on maximum mass given by the pulsars J1614-2230 and J0348+0432. We have developed a computational code to construct semi-analytical hybrid equations of state at fixed entropy per baryon and to obtain different families of hybrid stars. An analytical approximation of the Field Correlator Method is developed for the quark matter equation of state. For the hadronic equation of state we use a table based on the relativistic mean field theory, without hyperons. We solved the relativistic structure equations of hydrostatic equilibrium and mass conservation for hybrid star configurations. For the different equations of state obtained, we calculated the stability window for the strange quark matter, lepton abundances, temperature profiles and contours profiles for the maximum mass star depending on the parameters of the Field Correlator Method. We also computed the mass-radius and gravitational mass-baryonic mass relationships for different hybrid star families. We have analyzed different stages of hot hybrid stars as a first approximation of the cooling evolution of neutron stars with quark matter cores. We obtain cold hybrid stars with maximum masses $\geq 2 M_\odot$ for different combinations of the Field Correlator Method parameters. In addition, our study based on the gravitational mass - baryonic mass plane shows a late phase transition between hadronic and quark matter during the proto-hybrid star evolution, in contrast with previous studies of proto-neutron stars.Comment: 12 pages, 14 figures, published in A&A 601, A21 (2017

Dirichlet's and Thomson's principles for non-selfadjoint elliptic operators with application to non-reversible metastable diffusion processes

We present two variational formulae for the capacity in the context of non-selfadjoint elliptic operators. The minimizers of these variational problems are expressed as solutions of boundary-value elliptic equations. We use these principles to provide a sharp estimate for the transition times between two different wells for non-reversible diffusion processes. This estimate permits to describe the metastable behavior of the system

Fractional charges in pyrochlore lattices

A pyrochlore lattice is considered where the average electron number of electrons per site is half--integer, concentrating on the case of exactly half an electron per site. Strong on-site repulsions are assumed, so that all sites are either empty or singly occupied. Where there are in addition strong nearest--neighbour repulsions, a tetrahedron rule comes into effect, as previously suggested for magnetite. We show that in this case, there exist excitations with fractional charge (+/-) e/2. These are intimately connected with the high degeneracy of the ground state in the absence of kinetic energy terms. When an additional electron is inserted into the system, it decays into two point like excitations with charge -e/2, connected by a Heisenberg spin chain which carries the electron's spin.Comment: 10 pages, 4 eps figures. To appear in Decemeber issue of Annalen der Physi

Penerapan Model Pembelajaran Kooperatif Tipe Make A Match untuk Meningkatkan Motivasi Belajar Siswa pada Mata Pelajaran IPS Siswa Kelas Viii.d SMP Negeri 1 Simpang Kanan

This study aims to increase students' motivation in social studies class of VIII. D SMPN 1 Simpang Kanan, Rokan Hilir through the implementation of learning model of Make A Match on the subject matter even semester in the academic year 2015/2016. The subjects of this study were 20 students consisting of 10 male students and 10 female students. From the research activity of teacher has increased in the first cycle obtained a score of 70.83% both categories, the percentage increased to 95.83% with the category very well. Activities of students in the first cycle only get a percentage 71.67% both categories, increased in the second cycle to a percentage of 86.67% with a good category. Student's motivation is also seen to rise, it is evident from the percentage of student motivation in the first cycle that only earn a percentage of 75.00% in both categories, the percentage increased to 83.75% in both categories. According to the results of the data analysis and discussion of the implementation of this study can be concluded that the use of learning model Make A Match with media cards can increase students' motivation in social studies class VIII D SMPN 1 Simpang Kanan, Simpang Kanan Rokan Hilir in the academic year 2015/2016

Supporting the active learning of collaborative database browsing techniques

We describe the implications of a study of database browsing behaviour for the development of a system to support more effective browsing. In particular we consider the importance of collaborative working, both in learning browsing skills and in co‐operating on a shared information‐retrieval task. From our study, we believe that an interface to support collaboration should promote the awareness of the activities of others, better visualization of the information data structures being browsed, and effective communication of the browsing process