Applying Friedmann models to describe the evolution of the Universe based on data from the SAI Supernovae Catalog

In the recent years thanks to the modern and sophisticated technologies the astronomers and astrophysicists were able to look deep into the Universe. This vast data poses some new problem to the cosmologists. One of the problems is to develop an adequate theory. Another one is to fit the theoretical results with the observational one. In this report within the scope of the isotropic and homogeneous Friedman-Lemaitre-Robertson-Walker (FLRW) cosmological model we study the evolution of the Universe filled with dust or cosmological constant. The reason to consider this model is the present universe surprisingly homogeneous and isotropic in large scale. We also compare our results with the data from the SAI Supernovae Catalog. Since the observational data are given in terms of Hubble constant (????) and redshift (????) we rewrite the corresponding equations as a functions of ????. The task is to find the set of parameters for the mathematical model of an isotropic and homogeneous Universe that fits best with the astronomical data obtained from the study of supernovae: magnitude (????), redshift (????).

Redshifting Cosmic Photons in a Non-Expanding Universe

Cosmologists present clear observational evidences that stellar objects like stars and galaxies do carry out pronounced proper motions, and the question may be raising how these peculiar motions might evolve in time. In this article we study these peculiar motions of single objects, independent whether of microscopic or macroscopic nature, embedded in a globally homogeneous, static, massive universe with inherent gravity. Aims: We show that these objects at their motions, even in a homogeneous universe around them, are permanently subject to net gravitational forces due to the fact that in a post-Newtonian relativistic treatment the sources of cosmic masses are seen under retarded positions, retarded by the time it takes to communicate via gravitons the positions of these masses to the moving object. Methods: This “aberrational” recognition of massive source points on the one hand leads to a braking power permanently decelerating the peculiar motion of any cosmic object, on the other hand it also effects the wave lengths of all photons freely propagating through cosmic space under the action of cosmic gravity. Photons, even in a static homogeneous universe, undergo a permanent red-shifting, since working permanently against a net gravitational force from the direction opposite to the photon’s propagation direction. Results: We do show that the observationally confirmed redshifts of photons from distant galaxies under the new auspices appear as a pure measure of the distance which the photons passed from its galactic emitter to us. In this view redshifts have nothing to do with the Hubble dynamics of the universe and its emitters. Since, however, the existence of Hubble-induced redshifts cannot be excluded, we also look into a combination of both, gravitationally induced redshifts zg and Hubble-induced redshifts zH. We show that gravitationally induced redshifts zg of course also appear in an expanding universe, and it can be demonstrated that for instance in a “coasting universe” with a constant expansion rate R˙ and with R α t both these redshifts zg and zH would lead to similar results.

The Homogeneous Universe

This chapter discusses Albert Einstein's (1917) proposal, from pure thought, that a philosophically sensible universe is homogeneous and isotropic: no preferred center or direction, no observable edges to the universe as we see it around us. That of course is apart from the minor irregularities of matter concentrated in people and planets and stars. Einstein's homogeneity is essential to the thought that one might be able to find a theory of the universe as a whole rather than of one or another of its parts. It was an inspired intuitive vision or maybe just a lucky guess; Einstein certainly had no observational evidence that suggested it. The history of how Einstein's thought was received and tested exemplifies the interplay in science between theory and practice, sometimes reinforcing each other; sometimes in serious tension; and, as in this case, sometimes aided by unexpected developments. The chapter then considers the development of the evidence that supports what became known as Einstein's cosmological principle.

Evaluation of Attitude Towards Collaboration in Physicians and Nurses: A Cross-Sectional Research

INTRODUCTION: In this study, it was aimed to investigate the attitudes of physicians and nurses working in a aducational and research hospital towards collaboration according to socio-demographic variables. METHODS: This study was conducted in a aducational andr esearch hospital between April-May 2018. 1292 physicians and nurses constituted the universe and the sample size was 297 for this non-homogeneous universe. The questionnaires prepared in accordance with the aim of the study were completed by physicians and nurses on a voluntary basis. ‘Jefferson Scale of Attitudes Toward Physician-Nurse Collaboration’ was used to evaluate the collaboration score. For statistical analysis, t-test, One-way Anova test, and after the Anova test, Scheffe was used as complementary post-hoc analysis to determine the differences. The p value of <0.05 was accepted for statistical significance. RESULTS: According to the occupational variable, nurses have a more positive attitude and are more prone to collaboration than physicians. There was a statistically significant relationship between the variables of profession, gender, age, education level and nursing study area. There was no statistically significant relationship between demographic characteristics such as physician study area, experience and visit status (p>0,05). DISCUSSION AND CONCLUSION: It was concluded that the implementation of joint vocational training programs that will strengthen the collaboration attitude and the creation of an atmosphere of Professional respect will provide positive results in health service delivery.

Intermediate inflation with non-canonical scalar field in the low anisotropy Universe

The behavior of a non-canonical scalar field within an anisotropic Bianchi type I, spatially homogeneous Universe in the framework of the intermediate inflation will be studied. It will be examined on the condition that both the anisotropy and non-canonical sources come together if there is any improvement in compatibility with the observational data originated from Planck 2015. Based on this investigation, it can be observed that automatically a steep potential which can manage inflation in a better way will be obtained. Additionally, as a common procedure for an inflationary study, we shall try to calculate the related inflationary observables such as the amplitude of the scalar perturbations, scalar and tensor spectral indices, tensor-to-scalar ratio, the running spectral index and the number of e-folds. As an exciting part of our results, we will find that our model has a good consistency compared to data resulting from CMB and different Planck results. To justify our claims, the well-known canonical inflationary scenario in an anisotropic Bianchi type I Universe will also be evaluated.

Dynamical Stability of Bulk Viscous Isotropic and Homogeneous Universe

In this paper, we study the phase space portrait of homogeneous and isotropic universe by taking different coupling functions between dark energy models and bulk viscous dark matter. The dimensionless quantities are introduced to establish an autonomous set of equations. To analyze the stability of the cosmos, we evaluate critical points and respective eigenvalues for different dynamical quantities. For bulk viscous matter and radiation in tachyon coupled field, these points show stable evolution when γ ≫ δ but accelerated expansion of the universe for δ > 1 9 . The stability of the universe increases for some stationary points which may correspond to the late-time expansion for the coupled phantom field.

Stability analysis of coupled phantom and tachyon field models in nonlinear electrodynamics

This paper is devoted to studying the phase space portrait of FRW universe by taking different linear forms of coupling between scalar field models and dark matter with nonlinear electromagnetic effects. We introduce normalized dimensionless quantities to construct an autonomous system of equations. We evaluate critical points and respective eigenvalues for different parameters to analyze the stability of the cosmos. These points show saddle/unstable behavior for tachyon coupled field with the nonaccelerating universe. In the case of phantom energy, the stability decreases for some critical points which also represent the nonaccelerating universe. We conclude that the dynamical stability of the isotropic and homogeneous universe model reduces in the presence of nonlinear electrodynamics for tachyon as well as the phantom field.

Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation

Context. Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. Aims. We investigate the Be abundance in the extremely metal-poor star 2MASS J1808-5104 ([Fe/H] = −3.84) with the aim of constraining inhomogeneities or the presence of late decaying particles. Methods. High resolution, high signal-to-noise ratio (S/N) UV spectra were acquired at ESO with the Kueyen 8.2 m telescope and the UVES spectrograph. Abundances were derived using several model atmospheres and spectral synthesis code. Results. We measured log(Be/H) = −14.3 from a spectrum synthesis of the region of the Be line. Using a conservative approach, however we adopted an upper limit two times higher, i.e. log(Be/H) < −14.0. We measured the O abundance from UV–OH lines and find [O/H] = −3.46 after a 3D correction. Conclusions. Our observation reinforces the existing upper limit on primordial Be. There is no observational indication for a primordial production of 9Be. This places strong constraints on the properties of putative relic particles. This result also supports the hypothesis of a homogeneous Universe, at the time of nucleosynthesis. Surprisingly, our upper limit of the Be abundance is well below the Be measurements in stars of similar [O/H]. This may be evidence that the Be–O relation breaks down in the early Galaxy, perhaps due to the escape of spallation products from the gas clouds in which stars such as 2MASS J1808-5104 have formed.