Dependence of Floral Buds Hardiness of Pear Cultivars to Spring Frosts From Stage of Development in Arid Zone of Central Kazakhstan
Автор(ы): Андрианова Н. Г.*
Объем документа:
МРНТИ: 34.35.17
Ключевые слова: аридные зоны Центральной Азии*устойчивость цветковых почек груши*стадии развития цветка*влияние весенних заморозков*
Реферат: Results of research of floral buds hardiness of pear cultivars under conditions of the arid zone of Central Kazakhstan are presented in given article. Investigations have shown that the damage degree of blossom by spring frosts depends on their stage of development. The above the stage of development of floral buds, the more considerably degree of their damage by spring frosts. Blossom of pear cultivars with early beginning vegetation are exposed to the greatest danger from influence of low critical temperatures.
Observational constraints on non-minimally coupled Galileon model
Реферат: As an extension of Dvali-Gabadadze-Porrati (DGP) model, the Galileon theory has been proposed to explain the \"self-accelerating problem\" and \"ghost instability problem\". In this paper, we extend the Galileon theory by considering a non-minimally coupled Galileon scalar with gravity. We find that crossing of the phantom divide line is possible for such model. Moreover we perform the statefinder analysis and Om(z) diagnostic and constraint the model parameters from the latest Union 2 type Ia Supernova (SNe Ia) set and the baryonic acoustic oscillation (BAO). Using these data sets, we obtain the constraints Omega(m0) = 0.263(-0.031)(+0.031), n = 1.53(-0.37)(+0.21) (at the 95 % confidence level) with chi(2)(min) = 473.376. Further we study the evolution of the equation of state parameter for the effective dark energy and observe that SNe Ia + BAO prefers a phantom-like dark energy.
Generalized second law of thermodynamics in f(T) gravity with entropy corrections
Ключевые слова: обобщенный второй закон термодинамики*космология*энтропия*телепараллельная модель*
Реферат: We study the generalized second law (GSL) of thermodynamics in f(T) cosmology, where T is the torsion scalar in teleparallelism. We consider the universe as a closed bounded system filled with n component fluids in the thermal equilibrium with the cosmological boundary. We use two different cosmic horizons: the future event horizon and the apparent horizon. We show the conditions under which the GSL will be valid in specific scenarios of the quintessence and the phantom energy dominated eras. Further we associate two different entropies with the cosmological horizons: with a logarithmic correction term and a power-law correction term. We also find the conditions for the GSL to be satisfied or violated by imposing constraints on model parameters.
Wormholes in a viable f(T) gravity
Автор(ы): (Jamil M.*Momeni D.*Myrzakulov R.*
Объем документа:
МРНТИ: 29.05.45
Ключевые слова: решения статической червоточины*F(T) гравитация*уравнение состояния темной энергии*независимые компоненты давления*энергетические условия*
Реферат: In this paper, we derive some new exact solutions of static wormholes in f(T) gravity. We discuss independent cases of the pressure components including isotropic and anisotropic pressure. Lastly we consider radial pressure satisfying a barotropic equation of state. We also check the behavior of null energy condition (NEC) for each case and observe that it is violated for the anisotropic case, while it is satisfied for isotropic and barotropic cases.
Reconstruction of the equation of state for the cyclic universes in homogeneous and isotropic cosmology
Реферат: We study the cosmological evolutions of the equation of state (EoS) for the universe in the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time. In particular, we reconstruct the cyclic universes by using the Weierstrass and Jacobian elliptic functions. It is explicitly illustrated that in several models the universe always stays in the non-phantom (quintessence) phase, whereas there also exist models in which the crossing of the phantom divide can be realized in the reconstructed cyclic universes.
Analytical Holographic Superconductor with Backreaction Using AdS3/CFT2
Реферат: The holographic model for a two-dimensional superconductor has been investigated by considering the three-dimensional gravity in the bulk. To find the critical temperature, we used the Sturm-Liouville variational method. Where as the same method is applied for calculating the condensation of the dual operators on the boundary. We included the back reactions on the metric by a combination of the perturbation method of the fields with respect to the small parameter and then applying the variational integrals on the resulting equations of the motion. The critical temperature has been successfully obtained on the backreaction effects, and we showed that it dropped with a rise in the backreaction of the fields, and it makes the condensation harder. We can use our analytical results to support the numerical data which was reported previously.
Energy conditions in generalized teleparallel gravity models
Автор(ы): (Jamil M.*Momeni D.*Myrzakulov R.*
Объем документа: С. 263-273
МРНТИ: 29.05.41
Ключевые слова: энергетические условия обобщенной телепараллель гравитация*гравитационная модель*космология*
Реферат: In this paper, we investigate the energy conditions (including null, weak, strong, dominant) in generalized teleparallel gravities including pure F(T) , teleparallel gravity with non-minimally coupled scalar field and F(T) with non-minimally coupled scalar field models. In particular, we apply them to Friedmann-Robertson-Walker cosmology and obtain some corresponding results. Using two specific phenomenological forms of F(T) , we show that some of the energy conditions are violated.
Noether gauge symmetry of modified teleparallel gravity minimally coupled with a canonical scalar field
Реферат: This paper is devoted to the study of Noether gauge symmetries of f(T) gravity minimally coupled with a canonical scalar field. We explicitly determine the unknown functions of the theory: f(T), V(), and W(). We have shown that there are two invariants for this model, one of which defines the Hamiltonian, H, under time invariance (energy conservation) and the other is related to scaling invariance. We show that the equation of state parameter in the present model can cross the cosmological constant boundary. The behavior of the Hubble parameter in our model closely matches to that of the /\CDM model, thus our model is an alternative to the latter.
More on superconductors via gauge/gravity duality with nonlinear Maxwell field
Реферат: We have developed the recent investigations on the second-order phase transition in the holographic superconductor using the probe limit for a nonlinearмMaxwell field strength coupled to a massless scalar field. By analytical methods, based on the variational Sturm-Liouville minimization technique, we study the effects of the spacetime dimension and the nonlinearity parameter on the critical temperature and the scalar condensation of the dual operators on the boundary. Further, as a motivated result, we analytically deduce the DC- conductivity in the lowand zero temperatures regime. Especially in the zero temperature limit and in two dimensional toy model, we thoroughly compute the conductivity analytically.
Planar Symmetry in f(T) gravity
Автор(ы): (Manuel R.*(Houndjo M. J.*Momeni D.*Myrzakulov R.*
Реферат: Exact solutions for planar Weitzenboch geometries in generalized teleparallel gravity with torsion is presented. The model predicted the existence of Moller, Kattler-Wittaker and planar de-Sitter geometries for different forms of action.