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Some specific wormhole solutions in extended f(R,G,T) gravity 扩展 f(R,G,T) 引力中的一些具体虫洞解决方案
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-05-11 DOI: 10.1142/s0218271824500196
M. Ilyas, A. R. Athar, Fawad Khan, Nasreen Ghafoor, Haifa I. Alrebdi, Kottakkaran Sooppy Nisar, Abdel-Haleem Abdel-Aty

This research work provides an exhaustive investigation of the viability of different coupled wormhole (WH) geometries with the relativistic matter configurations in the f(R,G,T) extended gravity framework. We consider a specific model in the context of f(R,G,T)-gravity for this purpose. Also, we assume a static spherically symmetric spacetime geometry and a unique distribution of matter with a set of shape functions (β(r)) for analyzing different energy conditions. In addition to this, we examined WH-models in the equilibrium scenario by employing anisotropic fluid. The corresponding results are obtained using numerical methods and then presented using different plots. In this case, f(R,G,T) gravity generates additional curvature quantities, which can be thought of as gravitational objects that maintain irregular WH-situations. Based on our findings, we conclude that in the absence of exotic matter, WH can exist in some specific regions of the parametric space using modified gravity model as f(R,G,T)=R+αR2+βGn+γGln(G)+λT.

这项研究工作对在 f(R,G,T) 扩展引力框架内不同耦合虫洞(WH)几何与相对论物质构型的可行性进行了详尽的研究。为此,我们考虑了f(R,G,T)引力背景下的一个特定模型。同时,我们假定了静态球对称时空几何和独特的物质分布,并用一组形状函数(β(r))来分析不同的能量条件。此外,我们还采用各向异性流体研究了平衡情景下的 WH 模型。使用数值方法获得了相应的结果,并通过不同的图表进行了展示。在这种情况下,f(R,G,T) 引力会产生额外的曲率量,可以将其视为维持不规则 WH 位置的引力物体。根据我们的研究结果,我们得出结论:在没有奇异物质的情况下,WH 可以存在于参数空间的某些特定区域,其修正引力模型为 f(R,G,T)=R+αR2+βGn+γGln(G)+λT 。
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引用次数: 0
Dark energy based on exotic statistics 基于奇异统计的暗能量
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-04-30 DOI: 10.1142/s0218271824500111
M. Hoyuelos, P. Sisterna

Dark energy is an elusive concept, which has been introduced two decades ago in order to make the acceleration of the universe a comprehensible phenomenon. However, the nature of this energy is far from being understood, both from a fundamental as well as an observational way. In this work, we study cosmological consequences of the existence of particles (which we called “ewkons” in a previous work) which are quasi distinguishable, obey unorthodox statistics, and have an equation of state similar to many existent dark energy candidates (including negative relation between pressure and energy density). We find an effective scalar field description of this ewkon fluid, and obtain cosmological solutions for the dark energy-dominated epoch. This can be considered as a one-parameter class of dark energy models.

暗能量是一个难以捉摸的概念,二十年前提出这个概念是为了让人们理解宇宙加速现象。然而,无论是从基本原理还是从观测的角度来看,人们对这种能量的性质都知之甚少。在这项工作中,我们研究了粒子(我们在以前的工作中称之为 "ewkons")存在的宇宙学后果,这些粒子是准可区分的,服从非正统的统计,其状态方程与许多现存的暗能量候选粒子相似(包括压力与能量密度之间的负相关)。我们找到了对这种电子流体的有效标量场描述,并得到了暗能量主导的纪元的宇宙学解。这可以被视为一类单参数暗能量模型。
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引用次数: 0
Rotating regular black holes and other compact objects with a Tolman-type potential as a regular interior for the Kerr metric 旋转规则黑洞和其他具有托尔曼型势能的紧凑天体作为克尔公度量的规则内部
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-04-13 DOI: 10.1142/s021827182350102x
Angel D. D. Masa, Vilson T. Zanchin

In this paper, we obtain a new class of stationary axisymmetric spacetimes by using the Gürses–Gürsey metric with an appropriate mass function in order to generate a rotating core of matter that may be smoothly matched to the exterior Kerr metric. The same stationary spacetimes may be obtained by applying a slightly modified version of the Newman–Janis algorithm to a nonrotating spherically symmetric seed metric. The starting spherically symmetric configuration represents a nonisotropic de Sitter-type fluid whose radial pressure pr satisfies an state equation of the form pr=ρ, where the energy density ρ is chosen to be the Tolman-type-VII energy density [R. C. Tolman, Phys. Rev.55, 364 (1939)]. The resulting rotating metric is then smoothly matched to the exterior Kerr metric, and the main properties of the obtained geometries are investigated. All the solutions considered in this study are regular in the sense they are free of curvature singularities. Depending on the relative values of the total mass m and rotation parameter a, the resulting stationary spacetimes represent different kinds of rotating compact objects such as regular black holes, extremal regular black holes, and regular starlike configurations.

在本文中,我们利用具有适当质量函数的 Gürses-Gürsey 度量,生成了一类新的静止轴对称时空,其旋转物质核心可与外部克尔度量平滑匹配。对非旋转球面对称种子度量应用稍加修改的纽曼-简尼斯算法,也可以得到相同的静止时空。起始球对称构型代表一种非各向同性的德西特流体,其径向压力 pr 满足形式为 pr=-ρ 的状态方程,其中能量密度 ρ 被选作托尔曼型-VII 能量密度[R. C. Tolman, Phys. Rev.55, 364 (1939)]。然后将得到的旋转度量与外部克尔度量进行平滑匹配,并研究得到的几何图形的主要性质。本研究中考虑的所有解都是正则解,即不存在曲率奇异性。根据总质量 m 和旋转参数 a 的相对值,得到的静止时空代表了不同类型的旋转紧凑天体,如规则黑洞、极端规则黑洞和规则星状构型。
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引用次数: 0
Numerical analyses of M31 dark matter profiles M31 暗物质剖面的数值分析
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-04-10 DOI: 10.1142/s0218271824500160
Kuantay Boshkayev, Talgar Konysbayev, Yergali Kurmanov, Orlando Luongo, Marco Muccino, Hernando Quevedo, Gulnur Zhumakhanova

In this paper, we reproduce the rotation curve of the Andromeda galaxy (M31) by taking into account its bulge, disk and halo components, considering the last one to contain the major part of dark matter mass. Hence, our prescription is to split the galactic bulge into two components, namely, the inner and main bulges, respectively. Both bulges are thus modeled by exponential density profiles since we underline that the widely accepted de Vaucouleurs law fails to reproduce the whole galactic bulge rotation curve. In addition, we adopt various well-known phenomenological dark matter profiles to estimate the dark matter mass in the halo region. Moreover, we apply the least-squares fitting method to determine from the rotation curve the model free parameters, namely, the characteristic (central) density, scale radius and consequently the total mass. To do so, we perform Markov chain Monte Carlo statistical analyses based on the Metropolis algorithm, maximizing our likelihoods adopting velocity and radii data points of the rotation curves. We do not fit separately the components for bulges, disk and halo, but we perform an overall fit including all the components and employing all the data points. Thus, we critically analyze our corresponding findings and, in particular, we employ the Bayesian information criterion to assess the most accredited model to describe M31 dark matter dynamics.

在本文中,我们通过考虑仙女座星系(M31)的隆起、圆盘和光环部分,重现了它的旋转曲线,并认为最后一个部分包含了暗物质质量的主要部分。因此,我们将星系隆起分成两个部分,分别是内隆起和主隆起。由于我们强调广为接受的德-沃库勒(de Vaucouleurs)定律无法再现整个银河系隆起的旋转曲线,因此两个隆起都采用指数密度曲线建模。此外,我们还采用了各种著名的暗物质现象剖面来估算光环区域的暗物质质量。此外,我们还采用最小二乘拟合方法,从旋转曲线中确定模型的自由参数,即特征(中心)密度、尺度半径以及总质量。为此,我们根据 Metropolis 算法进行了马尔科夫链蒙特卡罗统计分析,通过旋转曲线的速度和半径数据点来最大化我们的似然。我们没有分别拟合凸起、圆盘和光环的成分,而是进行了包括所有成分和采用所有数据点的整体拟合。因此,我们对相应的研究结果进行了批判性分析,特别是采用贝叶斯信息准则来评估最适合描述 M31 暗物质动力学的模型。
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引用次数: 0
Qualitative probe of interacting dark energy with redshift-space distortions 利用红移空间扭曲定性探测相互作用暗能量
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-03-26 DOI: 10.1142/s0218271824500123
Didam G. A. Duniya

The imprint of interacting dark energy (IDE) needs to be correctly identified in order to avoid bias in constraints on IDE. This paper investigates the large-scale imprint of IDE in redshift-space distortions (RSDs), using Euclid-like photometric prescriptions. A first attempt at incorporating the IDE dynamics in the galaxy (clustering and evolution) biases is made. Without IDE dynamics taken into account in the galaxy biases, as is conventionally done, the results suggest that for a constant dark energy (DE) equation of state parameter, an IDE model where the DE transfer rate is proportional to the DE density exhibits an alternating, positive–negative effect in the RSDs angular power spectrum. However, when the IDE dynamics is incorporated in the galaxy biases, it is found that the apparent positive–negative alternating effect vanishes: implying that neglecting IDE dynamics in the galaxy biases can result in “artifacts” that can lead to incorrect identification of the IDE imprint. In general, the results show that multi-tracer analysis will be needed to beat down cosmic variance in order for the RSDs angular power spectrum as a statistic to be a viable diagnostic of IDE. Moreover, it is found that RSDs hold the potential to constrain IDE on large scales, at redshifts z1, with the scenario having IDE dynamics incorporated in the biases showing better potential.

需要正确识别相互作用暗能量(IDE)的印记,以避免对 IDE 的约束产生偏差。本文利用类似欧几里得的测光规定,研究了IDE在红移空间扭曲(RSDs)中的大尺度印记。首次尝试将 IDE 动态纳入星系(聚类和演化)偏差。结果表明,在暗能量(DE)状态方程参数不变的情况下,暗能量转移速率与暗能量密度成正比的IDE模型在RSD角功率谱中表现出正负交替的效应。然而,当把 IDE 动力学纳入星系偏差时,发现明显的正负交替效应消失了:这意味着在星系偏差中忽略 IDE 动力学会导致 "伪影",从而导致 IDE 印记的错误识别。总之,研究结果表明,需要进行多追踪器分析来消除宇宙差异,才能使 RSDs 角功率谱作为一种统计量成为 IDE 的可行诊断方法。此外,研究还发现 RSDs 有可能在大尺度上对 z≤1 的红移进行 IDE 约束,而将 IDE 动力学纳入偏差的方案则显示出更好的潜力。
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引用次数: 0
Plane-fronted electromagnetic waves and an asymptotic limit of Liénard–Wiechert fields 平面电磁波和李纳-维切特场的渐近极限
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-03-23 DOI: 10.1142/s0218271824500093
Peter A. Hogan, Dirk Puetzfeld

Colliding or noncolliding plane-fronted electromagnetic or gravitational waves are the asymptotic limit of Robinson–Trautman spherical electromagnetic or gravitational waves. Noncolliding plane-fronted waves contain no information about their sources whereas colliding waves contain information about possibly the motion of their sources. As a first step to investigate the latter phenomenon, we construct an asymptotic limit of Liénard–Wiechert electromagnetic fields in the context of Minkowskian spacetime. This has the advantage that the source is well known and the calculations can be carried out in full detail. The final result is an algebraically general Maxwell field which consists of colliding plane-fronted waves in a subregion of Minkowskian spacetime and an interesting byproduct is a novel perspective on a Maxwell field originally discovered by Bateman.

碰撞或非碰撞平面电磁波或引力波是罗宾逊-特劳特曼球面电磁波或引力波的渐近极限。非对撞平面波不包含任何有关其来源的信息,而对撞波则包含可能有关其来源运动的信息。作为研究后一种现象的第一步,我们在闵科夫斯基时空中构建了李纳-维切特电磁场的渐近极限。这样做的好处是,源是众所周知的,可以进行全面详细的计算。最后的结果是一个代数上一般的麦克斯韦场,它由明科夫斯基时空中一个子区域中碰撞的平面波组成,一个有趣的副产品是对贝特曼最初发现的麦克斯韦场的一个新视角。
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引用次数: 0
Universe bouncing its way to inflation 宇宙反弹通胀
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-03-22 DOI: 10.1142/s0218271824500068
Manjeet Kaur, Debottam Nandi, Debajyoti Choudhury, T. R. Seshadri

Cosmological models with inflation and those with bounce have their own strengths and weaknesses. Here, we construct a model in which a phase of bounce is followed by a viable inflationary phase. This incorporates several advantages of both and hence, is a more viable model for cosmic evolution. We explore scenarios wherein the bouncing phase smoothly transits to an inflationary one, with the pivot scale leaving the Hubble horizon during the latter era, thereby maintaining consistency with observations. Staying within the ambit of Einstein–Hilbert gravity augmented by the inflation, we ensure a pre-inflationary bounce by introducing a second scalar field that helps engineer the requisite violation of the null energy condition. Potential ghost instabilities can be mitigated by invoking a nontrivial coupling between the two scalar fields.

有通货膨胀的宇宙学模型和有反弹的宇宙学模型各有优缺点。在这里,我们构建了一个模型,在这个模型中,反弹阶段之后是一个可行的暴胀阶段。这个模型融合了两者的若干优点,因此是一个更可行的宇宙演化模型。我们探讨了反弹阶段平稳过渡到暴胀阶段的情景,在暴胀阶段,中枢尺度离开哈勃视界,从而与观测结果保持一致。在通货膨胀增强的爱因斯坦-希尔伯特引力范围内,我们通过引入第二个标量场来确保通货膨胀前的反弹,该标量场有助于设计必要的违反空能条件。潜在的幽灵不稳定性可以通过调用两个标量场之间的非难耦合来缓解。
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引用次数: 0
Noncommutative effects on wormholes in Rastall–Rainbow gravity 拉斯塔尔-彩虹引力中虫洞的非交换效应
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-03-20 DOI: 10.1142/s0218271824500081
Anirudh Pradhan, Safiqul Islam, M. Zeyauddin, Ayan Banerjee

In this paper, we explore the physical properties and characteristics of static, spherically symmetric wormholes in the background of Rastall–Rainbow gravity. The Rastall–Rainbow gravity theory has recently been proposed as a combination of two theories, namely, the Rastall theory and the Rainbow description. We implemented noncommutativity by adopting two different distributions of energy density (Gaussian and Lorentzian) in the Morris and Thorne metric. We solve the field equations analytically and discuss all the properties of wormholes depending on the two model parameters. Notably, for specific parameter ranges, one can alleviate the violation of the WEC at the throat and its neighborhood.

本文探讨了在拉斯托尔-彩虹引力背景下静态球对称虫洞的物理特性和特征。最近提出的拉斯托尔-彩虹引力理论是两种理论的结合,即拉斯托尔理论和彩虹描述。我们在莫里斯和索恩公设中采用了两种不同的能量密度分布(高斯分布和洛伦兹分布),从而实现了非交换性。我们对场方程进行了分析求解,并讨论了取决于两个模型参数的虫洞的所有特性。值得注意的是,在特定的参数范围内,我们可以减轻虫洞及其邻近地区的虫洞违反行为。
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引用次数: 0
Null geodesic structure for the Barriola–Vilenkin spacetime via k-essence 巴里奥拉-维伦金时空的空大地结构(通过 k-等价性
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-03-15 DOI: 10.1142/s0218271824500056
Bivash Majumder, Saibal Ray, Goutam Manna

Based on the work of Chandrasekhar [The Mathematical Theory of Black Holes, Chap. 3, Sec. 20 (Oxford University Press, 1992)], we investigate the null geodesic structure of the emergent Barriola–Vilenkin (BV) spacetime in the context of k-essence theory. For k-essence, the emergent gravity metric is a one-to-one correspondence with the BV metric connected to the Schwarzschild background, where the global monopole charge is replaced by the dark energy density. This equivalence holds specifically for a certain class of k-essence scalar fields that have been constructed by Gangopadhyay and Manna [Eur. Phys. Lett. 100, 49001 (2012)]. We have traced out different trajectories for null geodesic in the presence of dark energy for the k-essence emergent BV spacetime. It is demonstrated that the outcomes deviate from the typical Schwarzschild spacetime owing to the fundamental configuration with a constant dark energy density.

基于钱德拉塞卡(Chandrasekhar)的研究成果[《黑洞数学理论》,第 3 章,第 20 节(牛津大学出版社,1992 年)],我们研究了 k-essence 理论背景下出现的巴里奥拉-维伦金(BV)时空的空大地结构。对于 k-essence,新兴引力度量与与施瓦兹柴尔德背景相连的 BV 度量是一一对应的,其中全局单极电荷被暗能量密度所取代。这种等价性特别适用于 Gangopadhyay 和 Manna 构建的某类 k-essence标量场[《欧洲物理快报》100, 49001 (2012)]。在暗能量存在的情况下,我们为 k-essence 出现的 BV 时空追踪了空大地线的不同轨迹。结果表明,由于暗能量密度恒定的基本构型,这些轨迹偏离了典型的施瓦兹柴尔德时空。
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引用次数: 0
Effective potential in non-perturbative gauge theories 非微扰规整理论中的有效势
IF 2.2 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-02-21 DOI: 10.1142/s0218271823501110
Gianluca Calcagni, Marco Frasca, Anish Ghoshal

We consider a formalism to describe the false-vacuum decay of a scalar field in gauge theories in non-perturbative regimes. We find that the larger the gauge coupling with respect to the self-coupling of the scalar, the shallower the local minimum of the unstable vacuum, to the point where it disappears. This offers the possibility to obtain a consistent picture of early universe cosmology: at high temperatures, a false-vacuum decay is strongly favored and the universe naturally evolves towards a stable state.

我们考虑用一种形式主义来描述非微扰状态下规理论中标量场的假真空衰变。我们发现,相对于标量的自耦合而言,量规耦合越大,不稳定真空的局部最小值就越浅,甚至消失。这为获得早期宇宙学的一致图景提供了可能:在高温下,假真空衰变受到强烈青睐,宇宙自然会向稳定状态演化。
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引用次数: 0
期刊
International Journal of Modern Physics D
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