Gravastars have been considered as a serious alternative to black holes in the past couple of decades. Stable models of gravastar have been constructed in many of the alternate gravity models besides ...standard general relativity (GR). The Randall-Sundrum (RS) braneworld model has been a popular alternative to GR, especially in the cosmological and astrophysical context. Here, we consider a gravastar model in RS brane gravity. The mathematical solutions in different regions have been obtained with calculation of matching conditions. Various important physical parameters for the shell have been calculated and plotted to note their variation with radial distance. We also calculate and plot the surface redshift to provide a very cursory check on the stability of the gravastar within the purview of RS brane gravity.
The addition of ribociclib to hormone therapy showed a greater benefit with regard to overall survival than hormone therapy alone in women with hormone-receptor–positive, human epidermal growth ...factor receptor 2–negative advanced breast cancer.
Performance optimization of different layers of a perovskite solar cell is really important to augment its efficiency. Taking this into consideration, potential semiconductor materials for the ...electron transport layer have been studied using density functional theory. In this work, first-principle calculation of room temperature phase TiO2, SnO2, ZrO2 and HfO2 have been performed using meta-generalized gradient approximation functional (meta-GGA) with strongly constrained and appropriately normed (SCAN), the semi-local exschange-correlation function. For structural properties, we have optimized the unit cell structures of all the oxides and obtained the lattice parameters. In the electronic properties, the band structures and density of states are calculated and analyzed in detail. Also, real and imaginary parts of dielectric function, absorption coefficient, extinction coefficient, reflectivity and refractive index are calculated for in-depth analysis of the important optical properties. TiO2 and SnO2 have shown good characteristics that are required for photovoltaic applications. Further, the loss spectrum and optical conductivity have been estimated. Moreover, the elastic properties are also evaluated for examining the mechanical stability and hence the related elastic parameters such as bulk and shear moduli, Young's modulus, Pugh and Poisson's ratios and hardness parameters.
•First principle study of room temperature phase TiO2, SnO2, ZrO2 and HfO2 have been studied.•Structural, electronic, optical and mechanical properties are calculated using meta-GGA density functional.•Optical properties of the oxides have been studied exclusively for electron transport layer application.•Mechanical stability has been explored by calculating elastic properties.•Calculated results are compared with the literature and are found fairly consistent.
We have investigated the accelerating behaviour of the Universe in
f
(
Q
,
T
) gravity in an isotropic and homogeneous space-time. We have initially derive the dynamical parameters in the general ...form of
f
(
Q
,
T
)
=
α
Q
m
+
β
T
(Xu et al. in Eur Phys J C 79:708, 2019) and then split it into two cases (i) one with
m
=
1
and the (ii) other with
β
=
0
. In the first case, it reduces to the linear form of the functional
f
(
Q
,
T
) and second case leads to the higher power of the nonmetricity
Q
. In an assumed form of the hyperbolic scale factor, the models are constructed and its evolutionary behaviours are studied. The geometrical parameters as well the equation of state parameter are obtained and found to be in the preferred range of the cosmological observations. Marginal variation has been noticed in the behaviour of
ω
and
ω
eff
at present time. The violation of strong energy conditions in both the cases are shown. The dynamical system analysis for the models has been performed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
