Expansion Law Research Articles

Holographic Dark Energy Cosmological Models in f(G) Theory

In this paper, Locally Rotationally Symmetric (LRS) Bianchi type-I models with holographic dark energy within the framework of f(G) theory of gravitation are thought about. So as to get determinate solutions, volumetric exponential expansion, power law expansion and hybrid expansion law are mentioned. The physical interpretations of the solution have been studied by using some physical quantizes. Additionally to make the interpretation more clear for that the statefinder diagnostic pair {r, s} and jerk parameter are analyzed to characterize completely different phases of the universe.

Criminal Policy of Adultery in Indonesia

Judge courage needed in deciding adultery cases in article 284 of the Criminal Code for perpetrators who have not been bound by marriage, the judge can apply based on the 1945 Constitution and the Law on Judicial Power, which states the source of law is not only the Law (expansion of the principle of material legality) but can also source from code that lives in the community (customary law). This research is intended to analyze and describe the penal policy (criminal law policy and politics of criminal law) concerning adultery in Indonesia. This research uses normative legal research, where the Author analyze and compare all laws and regulations concerning to adultery in Indonesia and some theories of adultery in global context. This paper emphasized that adultery not only against religious values but also customary values (customary law). The formulation of adultery concept in Indonesian Penal Code affected by religious teachings and national ideology of Pancasila.

Electron temperature of the solar wind

Solar wind provides an example of a weakly collisional plasma expanding from a thermal source in the presence of spatially diverging magnetic-field lines. Observations show that in the inner heliosphere, the electron temperature declines with the distance approximately as [Formula: see text], which is significantly slower than the adiabatic expansion law [Formula: see text] Motivated by such observations, we propose a kinetic theory that addresses the nonadiabatic evolution of a nearly collisionless plasma expanding from a central thermal source. We concentrate on the dynamics of energetic electrons propagating along a radially diverging magnetic-flux tube. Due to conservation of their magnetic moments, the electrons form a beam collimated along the magnetic-field lines. Due to weak energy exchange with the background plasma, the beam population slowly loses its energy and heats the background plasma. We propose that no matter how weak the collisions are, at large enough distances from the source a universal regime of expansion is established where the electron temperature declines as [Formula: see text] This is close to the observed scaling of the electron temperature in the inner heliosphere. Our first-principle kinetic derivation may thus provide an explanation for the slower-than-adiabatic temperature decline in the solar wind. More broadly, it may be useful for describing magnetized collisionless winds from G-type stars.

Accelerating Bianchi type dark energy cosmological model with cosmic string in $f(T)$ gravity

In this paper, we have investigated some features of anisotropic accelerating Bianchi type-I cosmological model in the presence of two non-interacting fluids, i.e. one usual string and other dark energy fluid towards the gravitational field equations for the linear form of $f(T)$ gravity, where \textit{T }be the torsion. To achieve a physically realistic solution of the field equations, we have considered an exact matter dominated volumetric power law expansion. The aspects of derived model are discussed with the help of solution and make the model at late times turn out to be flat Universe. Also, observed that the model has initially non-singular and stable while for whole expansion it is unstable. At an initial expansion $0.01\le t\le 0.05$ when the Universe start to expand to infinite expansion $t>1.73$ (break away from for small interval of cosmic time $0.06\le t\le 1.73$), there is a matter dominated era while for $0.06\le t\le 1.73$ it approaches the quintessence region. Also, the string exists in the early universe which is in agreement with constraints of CMBR data but with the expansion the string phase of the Universe disappears, i.e. we have an anisotropic fluid of particles.

Anisotropic dark energy models in Brans Dicke theory of gravitation with different expansion laws: A comparative study

In this paper, we have derived the general solutions of the field equations of the Scalar–Tensor theory of gravitation, proposed by Brans and Dicke (1961) within the framework of a locally rotationally symmetric (LRS) metric. We have discussed the anisotropic dark energy models by assuming the time-dependent general scale factor [Formula: see text]. Further, we have discussed the physical and geometric behaviors of the model using different forms of the scale factors. We have also performed a comparative study of the results obtained in various cases. We have observed that the solutions obtained using Hybrid Expansion Law (HEL) are more consistent with recent observations as compared to the rest. Stability of the solutions is also compared using metric perturbations.

A new class of holographic dark energy models in conharmonically flat space-time

In this paper, we have obtained general exact solutions of the Einstein’s field equations from the use of conharmonically flat space in relation to a isotropic and spatially homogeneous Friedmann-Robertson-Walker(FRW) model by taking Granda and Oliveros IR cut-off and also by considering the cosmological scale factor in the form of hybrid expansion law (HEL). We investigated the derived model with the help of evolutionary trajectories of deceleration parameter, equation of state (EoS) parameter, energy densities of matter and dark energy, energy density parameters of matter and dark energy, for which model shows suitable behaviour. We also study classical stability of the model by analyzing the squared sound speed, which shows that the model is stable initially. For dynamical analysis of the model, the statefinder diagnostic and ωD−ωD′ pair analysis were performed. Additionally, we also plan to reconcile the dark energy by a method of reconstructing the evolution of the scalar field potential. For this analysis, we take into account the quintessence field for this reconstruction.

Dynamics Of Frw Type Kaluza-Klein Mhrde Cosmological Model In Self-Creation Theory

ABSTRACT In this work, we have studied Friedmann–Robertson–Walker type Kaluza–Klein universe filled with pressureless matter and modified holographic Ricci dark energy in the frame work of Barber’s self-creation theory. While solving field equations we have considered hybrid expansion law of average scale factor. Also we have studied differences between open, flat and closed models. We have calculated some physical properties such as deceleration parameter(q), EoS parameter(ωde ), spatial volume(V ), expansion scalar(θ). The physical and geometrical aspects of the statefinder parameters(r, s) and ωde − ω ′ de plane are also discussed. In ω de− ω ′ de plane discussion we have observed that the flat model lies in freezing region and the closed model lies in thawing region. Also we have observed that for flat model ωde crosses the phantom divide line( i.e. ωde = -1) and shows quintom like behavior. Among the three models the flat model is in good agreement with recent observational data.

Design and study on the tailorable directional thermal expansion of dual-material planar metamaterial

Current studies on tailoring the coefficient of thermal expansion of metamaterials focused on either complex bending-dominated lattice or the stretching-dominated lattice which transforms the spaces of triangle and tetrahedron. This paper proposes a kind of dual-material rectangular cell of tailorable thermal expansion, which reduces the complexities of design, calculation, and manufacture of lattice materials. The theoretical derivation using the matrix displacement method is adopted to study the thermal expansion properties of rectangular cell in the direction of height, the analytical expressions of coefficient of thermal expansion and optimization model are used to design the sizes of rectangular cell, and experimental verification is carried out. It is found that the middle cell of lattice had the same thermal expansion law as that of the unit cell. The rectangular cells of negative coefficient of thermal expansion −7 ppm/℃, zero coefficient of thermal expansion, and large positive coefficient of thermal expansion 36.2 ppm/℃ in the direction of height were realized, respectively. The consistency of theory, simulation, and experiment verifies that rectangular lattice material made of two kinds of common materials with a different coefficient of thermal expansions can achieve the design of coefficient of thermal expansion in the direction of height by choosing different material distribution and geometric parameters.

Friedmann–Robertson–Walker accelerating Universe with interactive dark energy

We have developed an accelerating cosmological model for the present universe which is phantom for the period $ (0 \leq z \leq 1.99)$ and quintessence phase for $(1.99 \leq z \leq 2.0315)$. The universe is assumed to be filled with barotropic and dark energy(DE) perfect fluid in which DE interact with matter. For a deceleration parameter(DP) having decelerating-accelerating transition phase of universe, we assume hybrid expansion law for scale factor. The transition red shift for the model is obtained as $z_t = 0.956$. The model satisfies current observational constraints.

A Study on the Rights and Protection of Indigenous People in Bangladesh

Indigenous people represent the ethnic groups of people around the world who are usually alienated from dominant societies, for their distinct custom, tradition and religious beliefs. Due to their ethnicity they have some limitations to exercise all human rights. Although the Universal Declaration of Human Rights is designed to protect the human rights of all human beings, it does not have any special mention for the group rights of indigenous people. The International Labor Organization (ILO) adopted the Indigenous and Tribal Populations Convention, 1957(No.107) for ensuring their rights and protections. Considering the development of international law and socio-economic expansion of indigenous community, the ILO revised this convention in 1989 (No. 169). Finally, the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP), 2007 has been adopted for promoting the inherent rights of indigenous people. In Bangladesh among 160 million people with heterogeneous religion, culture and tradition, nearly two-three million indigenous people from around fifty ethnic groups have been living for centuries. The Constitution of Bangladesh ensures the rights of indigenous people with special emphasis. This country has ratified major international human rights instruments including the ILO Convention No.107. Following the norms of these instruments some special laws have enacted for protecting their rights. But a major portion of them continues to be deprived of their rights due to legal inconsistency and inadequate implementations of existing laws. In this given context, this paper aims to analyze the actual legal status of indigenous people in Bangladesh from the view point of domestic and international law. Based upon such assessment, some suggestions will be put forth to the policy and law makers of Bangladesh to protect and promote the rights of indigenous people through exhaustive implementations of domestic and international law.

The late cosmic acceleration and the coincidence problem in Bianchi type I Universe

In locally rotationally symmetric (LRS) Bianchi-I spacetime, we are considering a special kind of a scale factor, called the hybrid expansion law (HEL). The HEL provides a description of the transition from deceleration to cosmic acceleration. A non-minimal interaction between dark energy (DE) and dark matter (DM) allows to combine the transition from matter dominance to the era of the DE dominance with the transition from decelerated to accelerated expansion. In the proposed model, the linear interaction of the two components solves the coincidence problem of our present Universe. We present examples of numerical values of the HEL parameters compatible with the constructed model and the observational data.

Tsallis holographic dark energy in Bianchi-I Universe using hybrid expansion law with k-essence

In this paper, the proposed dark energy, Tsallis holographic dark energy (THDE), infrared cut-off with the Hubble horizon has been investigated in the Bianchi-I (axially symmetric) anisotropic model with a hybrid expansion law. It has been observed that the THDE is in tune with the accelerating Universe with equation of state (EoS) parameter ( $$\omega _{\mathrm {T}}<-1/3$$ ) in the k-essence region. We have used the statefinder diagnostic in our model. In addition, we try to accommodate the perspective of dark energy by the avenue of reconstructing the evolution of scalar field potential. We have considered the k-essence for the analysis of this reconstruction, showing the accelerated expansion at present.

The change of the Universe epochs within the scope of Bianchi type-V model

We investigate the Bianchi type-V cosmological model with dark matter and anisotropic dark energy. It is assumed that the two sources minimally interact, so their energy-momentum tensors are conserved separately. The proportionality condition that relates the shear scalar $$(\sigma )$$ with the expansion scalar $$(\theta )$$ and the assumption of a diagonal energy–momentum tensor lead to some restriction on the metric functions. A special law is introduced for skewness parameter that describes the deviation of pressure from isotropy. This law can lead to models: the little rip, the big rip and the hybrid expansion. The hybrid expansion law provides a description of the transition of the Universe from deceleration to acceleration. The Universe behavior is discussed depending on the numerical parameters of the models.

FRW dark energy cosmological model with hybrid expansion law

In this work, we study a cosmological model of spatially homogeneous and isotropic accelerating universe which exhibits a transition from deceleration to acceleration. For this, Friedmann Robertson Walker(FRW) metric is taken and Hybrid expansion law a(t)=tαexp(βt) is proposed and derived. We consider the universe to be filled with two types of fluids barotropic and dark energy which have variable equations of state. The evolution of dark energy, Hubble, and deceleration parameters etc., have been described in the form of tables and figures. We consider 581 data’s of observed values of distance modulus of various SNe Ia type supernovae from union 2.1 compilation to compare our theoretical results with observations and found that model satisfies current observational constraints. We have also calculated the time and redshift at which acceleration in the Universe had commenced.

A Cosmological Scenario from the Starobinsky Model within the f(R,T) Formalism

In this paper we derive a novel cosmological model from the f(R,T) theory of gravitation, for which R is the Ricci scalar and T is the trace of the energy-momentum tensor. We consider the functional form f(R,T)=f(R)+f(T), with f(R) being the Starobinsky Model, named R+αR2, and f(T)=2γT, with α and γ being constants. We show that a hybrid expansion law form for the scale factor is a solution for the derived Friedmann-like equations. In this way, the model is able to predict both the decelerated and the accelerated regimes of expansion of the universe, with the transition redshift between these stages being in accordance with recent observations. We also apply the energy conditions to our material content solutions. Such an application makes us able to obtain the range of acceptability for the free parameters of the model, named α and γ.

Hypersurface-homogeneous modified holographic Ricci dark energy cosmological model by hybrid expansion law in Saez–Ballester theory of gravitation

The main motive of this investigation is to study the behavior of cosmological model in the presence of matter and a modified holographic Ricci dark energy for homogeneous hypersurface in the scalar tensor theory of gravitation, proposed by Saez–Ballester (Phys. Lett. A, 113, 467 (1986)). The hybrid expansion law (Akarsu et al., JCAP, 01, 022 (2014)) has been used to get a determinate solution. The physical condition that is shear scalar proportional to the expansion scalar is used to obtain the solution of the field equations. The various physical and geometrical aspects of the model are also discussed.

Accelerating universe with variable EoS parameter of dark energy in Brans–Dicke theory of gravitation

We have investigated the spatially homogeneous and isotropic Friedmann–Robertson–Walker (FRW) universe filled with barotropic fluid and dark energy in the framework of the Brans–Dicke theory of gravitation. Here we have discussed three models: (i) law of variation for Hubble’s parameter, which leads to a constant value of deceleration parameter, (ii) hybrid expansion law model, and (iii) special form of deceleration parameter model. We have found that among all these derived models, the most suitable standard cosmological model according to the recent cosmological observations is the model with special form of deceleration parameter.

Second-order two-temperature model of heat transfer processes in a thin metal film subjected to an ultrashort laser pulse

Thermal processes in domain of thin metal film subjected to an ultrashort laser pulse are considered. A mathematical description of the process discussed is based on the system of four equations. Two of them describe the electrons and lattice temperature, while third and fourth equations represent the generalized Fourier law, it means the dependencies between the electrons (lattice) heat flux and the electrons (lattice) temperature gradient. In the generalized Fourier law the heat fluxes are delayed in relation to the temperature gradients which consequently causes the appearance of heat fluxes time derivatives in the appropriate equations. Depending on the order of the generalized Fourier law expansion into the Taylor series, the first- and the second-order model can be obtained. In contrast to the commonly used first-order model, here the second-order two-temperature model is proposed. The problem is solved using the implicit scheme of the finite difference method. The examples of computations are also presented. It turns out that for the low laser intensities the results obtained using the first- and the second-order models are very similar.

Structure and expansion law of H ii regions in structured molecular clouds

Abstract We present radiation-magnetohydrodynamic simulations aimed at studying evolutionary properties of H ii regions in turbulent, magnetized, and collapsing molecular clouds formed by converging flows in the warm neutral medium. We focus on the structure, dynamics, and expansion laws of these regions. Once a massive star forms in our highly structured clouds, its ionizing radiation eventually stops the accretion (through filaments) towards the massive star-forming regions. The new overpressured H ii regions push away the dense gas, thus disrupting the more massive collapse centres. Also, because of the complex density structure in the cloud, the H ii regions expand in a hybrid manner: they virtually do not expand towards the densest regions (cores), while they expand according to the classical analytical result towards the rest of the cloud, and in an accelerated way, as a blister region, towards the diffuse medium. Thus, the ionized regions grow anisotropically, and the ionizing stars generally appear off-centre of the regions. Finally, we find that the hypotheses assumed in standard H ii-region expansion models (fully embedded region, blister-type, or expansion in a density gradient) apply simultaneously in different parts of our simulated H ii regions, producing a net expansion law (R∝ tα, with α in the range of 0.93–1.47 and a mean value of 1.2 ± 0.17) that differs from any of those of the standard models.

Dynamics of anisotropic dark energy universe embedded in one-directional magnetized fluid

In this work, we have constructed an anisotropic dark energy cosmological model in a two-fluid situation, such as the usual dark energy and the magnetized fluid. We have assumed the dark energy pressure to be anisotropic in different spatial directions. In order to develop the mathematical formalism of the model, we have considered the scale factor as hybrid scale factor which is a combination of both power law and exponential volumetric expansion law. The physical parameters are derived and analyzed and found to be in agreement with the observational limits.