Constrained Dynamics of Tachyon Field in FRWL Spacetime

In this paper we continue study of tachyon scalar field described by a Dirac-Born-Infeld (DBI) type action with constraints in the cosmological context. The proposed extension of the system introducing an auxiliary field in the minisuperspace framework is discussed. A new equivalent set of constraints is constructed, satisfying the usual regularity conditions.Comment: 10 pages, to be published in the Special Issue of the Facta Universitatis Series: Physics, Chemistry and Technology devoted to the SEENET-MTP Balkan Workshop BSW2019 (3-14 June 2018, Nis, Serbia

CONSTRAINED DYNAMICS OF TACHYON FIELD IN FRWL SPACETIME

In this paper, we continue the study of tachyon scalar field described by a Dirac-Born-Infeld (DBI) type action with constraints in the cosmological context. The proposed extension of the system introducing an auxiliary field in the minisuperspace framework is discussed. A new equivalent set of constraints is constructed, satisfying the usual regularity conditions

Inflationary RSII Model with a Matter in the Bulk and Exponential Potential of Tachyon Field

In this paper we study a tachyon cosmological model based on dynamics of a 3-brane in the second Randall-Sundrum (RSII) model extended to include matter in the bulk. The presence of matter in the bulk changes warp factor which leads to modification of inflationary dynamics. The additional brane behaves effectively as a tachyon. We calculate numerically observation parameters of inflation: the scalar spectral index ($n_s$) and the tensor-to-scalar ratio ($r$) for the exponential potential of tachyon field.Comment: 9 pages, 1 figure, will be published in the Special Issue of Facta Universitatis, Series: Physics, Chemistry and Technology devoted to the SEENET-MTP Balkan Workshop BSW2018 (3-14 June 2018

Numerical Calculation of Hubble Hierarchy Parameters and Observational Parameters of Inflation

We present results obtained by a software we developed for computing observational cosmological inflation parameters: the scalar spectral index ($n_s$) and the tensor-to-scalar ratio ($r$) for a standard single field and tachyon inflation, as well as for a tachyon inflation in the second Randall-Sundrum model with an additional radion field. The calculated numerical values of observational parameters are compared with the latest results of observations obtained by the Planck Collaboration. The program is written in C/C++. The \textit{GNU Scientific Library} is used for some of the numerical computations and R language is used for data analysis and plots.Comment: 8 pages, 5 figures, based on talk presented at The 10th Jubilee Conference of the Balkan Physical Union (BPU10), 26-30 August 2018 (Sofia, Bulgaria

A new model for the structure of the DACs and SACs regions in the Oe and Be stellar atmospheres

In this paper we present a new mathematical model for the density regions where a specific spectral line and its SACs/DACs are created in the Oe and Be stellar atmospheres. In the calculations of final spectral line function we consider that the main reasons of the line broadening are the rotation of the density regions creating the spectral line and its DACs/SACs, as well as the random motions of the ions. This line function is able to reproduce the spectral feature and it enables us to calculate some important physical parameters, such as the rotational, the radial and the random velocities, the Full Width at Half Maximum, the Gaussian deviation, the optical depth, the column density and the absorbed or emitted energy. Additionally, we can calculate the percentage of the contribution of the rotational velocity and the ions' random motions of the DACs/SACs regions to the line broadening. Finally, we present two tests and three short applications of the proposed model.Comment: 9 pages, 5 figures, accepted for publication in PAS

Model characteristics of motor abilities, morphological characteristics and life habits of the academy of criminalistic and police studies female students

Osnovni cilj istraživanja bio je usmeren na utvrđivanje relacija između aktuelnog stanja motoričkih sposobnosti, morfoloških karakteristika i životnih navika kod studentkinja Kriminalističko-policijske akademije. Ukupan uzorak sastojao se od 218 ispitanica podeljenih u četiri grupe: 83 studentkinje I godine, 53 studentkinje II godine, 50 studentkinja III godine i 32 studentkinje IV godine studija. Procena motoričkih sposobnosti obuhvatila je ispitivanje maksimalne izometrijske sile mišića, mišićne snage i opšte aerobne izdržljivosti, korišćena je standardna baterija testova propisana nastavnim planom i programom predmeta Specijalno fizičko obrazovanje. Morfološke karakteristike su utvrđene metodom multi segmentalne električne bioimpedance - aparatom InBody 720. Podaci o životnim navikama su dobijeni korišćenjem ankete i intervjua. Utvrđeno je da se nivo motoričkih sposobnosti povećava tokom studija, ali ne dostiže ciljni nivo. Rezultati korelacione matrice pokazale su veliki broj veza između varijabli motorike i morfologije. Komponente mišićnog i bezmasnog tkiva imaju pozitivan uticaj na ispoljavanje motoričkih sposobnosti, dok komponente masti negativno koreliraju sa opštim aerobnim sposobnostima i različitim oblicima mišićne snage. Navike u ishrani zajedno sa ukupnim skorovima životnih navika pozitivno utiču na morfološke karakteristike a posebno na komponente bezmasnog i mišićnog tkiva. Poželjan model za posmatrane prostore ima 53.66% studentkinja. Studentkinje se u funkciji godine studija najviše razlikuju po nivoima motoričkih sposobnosti, gde je viši nivo utvrđen kod studentkinja završnih godina. Studentkinje III i IV godine imaju bolji morfološki status i životne navike u odnosu na studentkinje I i II godine. Između posmatranih prostora postoje statistički značajne zavisnosti, a najveće stepen je utvrđen između prostora motoričkih sposobnosti i morfoloških karakteristika. Dobijeni rezultati nameću potrebu za dizajniranjem novih istraživanja u pravcu unapređenja stanja u posmatranim prostorima.The main aim of the research was determination of relations between the existing state of motor abilities, morphological characteristics and life habits among the Academy of Criminalistic and Police Studies female students. The total sample consisted of 218 female subjects divided in four groups: 83 students of the 1st, 53 students of the 2nd, 50 students of the 3rd and 32 students of the final 4th year of study. Assessment of the motor abilities included testing of maximal isometric muscle force, muscle strength and the general aerobic endurance, the standard battery of tests predicted by Specialized Physical Education curriculum was performed. Morphological characteristics were determined by electrical multi segmental bioimpedance – with apparatus InBody 720. Data of the life habits were obtained using the method of survey and interview. It was found that the level of motor abilities increases during the studies, but does not reach the aimed level. The results of the correlation matrix showed a large number of relations between variables of the motoric and morphology. The components of muscle tissue and fat free mass have a positive impact on the manifestation of the motor abilities, while the components of fat tissue negatively correlate with the general aerobic endurance and various forms of muscular strength. The eating habits along with total score of life habits positively influence on the morphological characteristics, especially on the components of fat free mass and muscle tissue. A desirable model for the observed areas has 53.66% of students. In the function of the year of studies, the students most differ in the motor abilities levels where higher levels was observed in two final years off studies. Also, the students of 3rd and 4th year have a better morphological characteristics and life habits compared to the student of 1st and 2nd year. Between the observed areas there are statistically significant dependencies and the highest level were found between motor abilities and morphological characteristics. The obtained results impose the need for designing new researches directed to improvement of the existing condition in the observed areas

Investigation of solidification behavior of the Sn-rich ternary Sn-Bi-Zn alloys

Solidification properties and microstructure of six as-cast Sn-Bi-Zn alloys with 80 at.% of Sn and variable contents of Bi and Zn were experimentally investigated using the scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and differential scanning calorimetry (DSC). The experimentally obtained results were compared with predicted phase equilibria according to the calculation of phase diagram (CALPHAD) method and by the Scheil solidification simulation.