scholarly journals Generalised Ellis–Bronnikov wormholes embedded in warped braneworld background and energy conditions

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Vivek Sharma ◽  
Suman Ghosh
Keyword(s):  
Extra Dimension ◽  
Shape Function ◽  
The Other ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Warp Factor ◽  
Simple Modification ◽  
The Status ◽  
Warped Extra Dimension

AbstractEllis–Bronnikov (EB) wormholes require violation of null energy conditions at the ‘throat’. This problem was cured by a simple modification of the ‘shape function’, which introduces a new parameter $$m\ge 2$$ m ≥ 2 ($$m=2$$ m = 2 corresponds to the EB model). This leads to a generalised (GEB) version. In this work, we consider a model where the GEB wormhole geometry is embedded in a five dimensional warped background. We studied the status of all the energy conditions in detail for both EB and GEB embedding. We present our results analytically (wherever possible) and graphically. Remarkably, the presence of decaying warp factor leads to satisfaction of weak energy conditions even for the EB geometry, while the status of all the other energy conditions are improved compared to the four dimensional scenario. Besides inventing a new way to avoid the presence of exotic matter, in order to form a wormhole passage, our work reveals yet another advantage of having a warped extra dimension.

scholarly journals Wormhole modeling in R2 gravity with linear trace term

2020 ◽  
Vol 35 (08) ◽  
pp. 2050045
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
General Relativity ◽  
General Theory ◽  
Significant Contribution ◽  
Shape Function ◽  
Exotic Matter ◽  
Geometric Configuration ◽  
Energy Conditions ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Traversable Wormholes

Morris and Thorne1 proposed traversable wormholes, hypothetical connecting tools, using the concept of Einstein’s general theory of relativity. In this paper, the modification of general relativity (in particular [Formula: see text] theory of gravity defined by Harko et al.2) is considered, to study the traversable wormhole solutions. The function [Formula: see text] is considered as [Formula: see text], where [Formula: see text] and [Formula: see text] are controlling parameters. The shape and redshift functions appearing in the metric of wormhole structure have significant contribution in the development of wormhole solutions. We have considered both variable and constant redshift functions with a logarithmic shape function. The energy conditions are examined, geometric configuration is analyzed and the radius of the throat is determined in order to have wormhole solutions in absence of exotic matter.

scholarly journals Wormhole modeling supported by non-exotic matter

2019 ◽  
Vol 34 (28) ◽  
pp. 1950224 ◽  
Author(s):  
Gauranga C. Samanta ◽  
Nisha Godani
Keyword(s):  
Shape Function ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Traversable Wormholes ◽  
Geometric Nature

In the present paper, the modeling of traversable wormholes, proposed by Morris and Thorne [Am. J. Phys. 56, 395 (1988)], is performed within the [Formula: see text] gravity with particular viable case [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text]. The energy conditions are analyzed using the shape function [Formula: see text] defined by Godani and Samanta [Int. J. Mod. Phys. D 28, 1950039 (2018)] and the geometric nature of wormholes is analyzed.

Wormhole models with exotic matter in Rastall gravity

2020 ◽  
Vol 17 (10) ◽  
pp. 2050146
Author(s):  
G. Mustafa ◽  
Tie-Cheng Xia
Keyword(s):  
Shape Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Shape Functions ◽  
Anisotropic Models ◽  
Specific Shape

In this paper, we examine the wormhole solutions by taking two different anisotropic models in Rastall gravity. For this purpose, we shall discuss anisotropic fluid to construct two different anisotropic models. Further, we shall employ two specific shape functions to calculate the behavior of energy conditions. The presence of exotic matter is confirmed in all the cases of this study due to the violation of the null energy condition. All the properties of shape function under both anisotropic models are fulfilled. It is noticed that wormhole solutions exist under the particular values of involved parameters in different cases in Rastall gravity.

Modeling of traversable wormholes in exponential f(R,T) gravity

2021 ◽  
Author(s):  
Chanchal Chawla ◽  
Archana Dixit ◽  
Anirudh Pradhan
Keyword(s):  
Shape Function ◽  
Anisotropy Parameter ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Physical Parameters ◽  
Asymptotically Flat ◽  
Physical Constraints ◽  
Traversable Wormholes ◽  
Necessary Constraints ◽  
The Universe

In the present communication, we have studied the existence of wormholes described by a logarithmic shape function, in the exponential f(R, T) gravity given by f(R, T) = R + 2ξe^{ςt} where ξ and ς are arbitrary constants, under three different set of physical constraints. The logarithmic shape function is found to be well behaved satisfying all the necessary constraints for traversable and asymptotically flat wormholes. The obtained wormhole solutions are analyzed from the energy conditions for different values of involved physical constants. It has been observed that our proposed shape function for the exponential form of f(R, T) gravity, represents the existence of exotic matter with a standard violation of the NEC. Moreover, for the trace T=0 i.e. for the general relativity case with R being replaced by R+2, the wormhole geometry has been analyzed to prove the existence of exotic matter. Further, the behaviour of physical parameters such as the energy density ρ, the trace T, anisotropy parameter △ describing the geometry of the universe has been presented with the help of graphs.

Influence of modification of gravity on spherical wormhole models

2017 ◽  
Vol 32 (30) ◽  
pp. 1750163 ◽  
Author(s):  
Z. Yousaf ◽  
M. Ilyas ◽  
M. Z. Bhatti
Keyword(s):  
Equation Of State ◽  
Gravity Model ◽  
Modified Gravity ◽  
Shape Function ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Barotropic Equation ◽  
The Stability

This paper explores some wormhole (WH) solutions in the background of additional matter contents of f(R, T) modified gravity. For this purpose, we have considered WH geometry filled with two physically different fluid configurations: one is anisotropic and another is anisotropic characterized by the barotropic equation of state. The energy conditions are examined with particular modified gravity model and found the existence of WH solutions even in the absence of exotic matter. Also, we have analyzed the behavior of shape function in this framework. The stability and physical existence of these solutions is studied with different fluid configurations. We conclude that in the absence of exotic matter, one can find WH solutions with particular model of modified gravity.

Wormhole models in R2-gravity for f(R, T) theory with a hybrid shape function

2021 ◽  
Author(s):  
Ambuj Kumar Mishra ◽  
Umesh Kumar Sharma
Keyword(s):  
Significant Contribution ◽  
Functional Form ◽  
Shape Function ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Ricci Scalar ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Specific Shape ◽  
Geometric Term

In the present paper, we explore wormholes in R<sup>2</sup>-gravity within the f(R,T) formalism by using b(r)= re<sup>r0-r</sup> (hybrid shape function). The functional form f(R, T)= R + αR<sup>2</sup> +λT is considered with R and T as the Ricci scalar and trace of energy-momentum tensor, respectively, α and β are controlling parameters. With the help of the EoS, ω= \frac{p_r}{\rho}, geometric behavior is analyzed and energy conditions are discussed in anisotropic scenario. In this investigation, significant contribution of the quadratic geometric term (R<sup>2</sup>) and linear trace term (T) are shown for validating energy conditions for specific shape function and analyzing wormhole solutions in absence of exotic matter. Also, we observe that the energy conditions are valid in whole range (r ≥ r0) in the case of constant redshift function with this shape function.

Stable Morris Thorne wormholes supported by non-exotic matter

2021 ◽  
pp. 2150170
Author(s):  
Nisha Godani
Keyword(s):  
General Relativity ◽  
Gravity Model ◽  
Stability Condition ◽  
Modified Gravity ◽  
Shape Function ◽  
Exotic Matter ◽  
Energy Conditions ◽  
Traversable Wormholes ◽  
The Stability ◽  
Metric Function

The present work is focused on the study of traversable wormholes, proposed by Morris and Thorne [Wormholes in spacetime and their use for interstellar travel: A tool for teaching general relativity, Am. J. Phys. 56 (1988) 395], using the background of modified gravity. It is performed by using the models: I. [Formula: see text], II. [Formula: see text] and III. [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are constants. The Model I belongs to the theory of [Formula: see text] gravity, Model II belongs to the theory of [Formula: see text] gravity and Model III is a combination of Models I and II. These functions have been taken into account for the exploration of wormhole solutions. The shape function, a wormhole metric function, is newly defined which satisfies the flare out condition. Further, the stability condition and energy conditions, namely null, weak and dominant energy conditions, have been examined with respect to each model.

Status of Family Fissidentaceae in Gujarat

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
D.G. Shah ◽  
D.N. Mehta ◽  
R.V. Gujar
Keyword(s):  
Distinct Species ◽  
The State ◽  
The Other ◽  
Land Plants ◽  
Reproductive Structures ◽  
The Family ◽  
The Status ◽  
Vegetative Characters ◽  
First Time ◽  
Different Parts

Bryophytes are the second largest group of land plants and are also known as the amphibians of the plant kingdom. 67 species of bryophytes have been reported from select locations across the state of Gujrat. The status of family fissidentaceae which is a large moss family is being presented in this paper. Globally the family consists of 10 genera but only one genus, Fissidens Hedw. has been collected from Gujarat. Fissidens is characterized by a unique leaf structure and shows the presence of three distinct lamina, the dorsal, the ventral and the vaginant lamina. A total of 8 species of Fissidens have been reported from the state based on vegetative characters as no sporophyte stages were collected earlier. Species reported from the neighboring states also showed the absence of sporophytes. The identification of different species was difficult due to substantial overlap in vegetative characters. Hence a detailed study on the diversity of members of Fissidentaceae in Gujarat was carried out between November 2013 and February 2015. In present study 8 distinct species of Fissidens have been collected from different parts of the state. Three species Fissidens splachnobryoides Broth., Fissidens zollingerii Mont. and Fissidens curvato-involutus Dixon. have been identified while the other five are still to be identified. Fissidens zollingerii Mont. and Fissidens xiphoides M. Fleisch., which have been reported as distinct species are actually synonyms according to TROPICOS database. The presence of sexual reproductive structures and sporophytes for several Fissidens species are also being reported for the first time from the state.

Practical Necessity and Moral Heroism

2017 ◽  
Author(s):  
Kyle Fruh
Keyword(s):  
The Other ◽  
Moral Exemplars ◽  
Other Hand ◽  
Practical Necessity ◽  
The Status ◽  
Illuminating Light

Discussions of closely associated notions of practical necessity, volitional necessity, and moral incapacity have profited from a focus on cases of agential crisis to further our understanding of how features of an agent’s character might bind her. This paper turns to agents in crises in order to connect this way of being bound to the phenomenon of moral heroism. The connection is fruitful in both directions. Importing practical necessity into examinations of moral heroism can explain the special sense of bindingness moral heroes frequently express while preserving the status of heroic acts as supererogatory. It also helps explain how heroes persevere and act as so few others do. On the other hand, the context of moral heroism allows a fuller development of some features of the concept of practical necessity, shedding more illuminating light on the roots of practical necessity in character through recent findings in the psychology of moral exemplars.

On Presumption

2017 ◽  
Author(s):  
Edna Ullmann-Margalit
Keyword(s):  
Status Quo ◽  
The Other ◽  
Specific Change ◽  
Ordinary Life ◽  
The Status ◽  
Difficult Situations

Some of the most difficult decisions in law and ordinary life are simplified by the use of some kind of presumption. Accused criminals are presumed to be innocent, and most of the time, legislative acts are presumed to be constitutional. And when people do not know what to do, they often adopt a presumption of some kind—for example, sticking with the status quo, or perhaps in favor of making a specific change. In countless domains, presumptions help people to extricate themselves from difficult situations. They can serve as a way of breaking an initial symmetrical situation by using a supposition not fully justified, yet not quite rash either—favoring one action over the other.

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