In this paper we suggest an approach to analyse the motion of a test particle in the spacetime of a global monopole within a $f(R)$-like modified gravity. The field equations are written in a more simplified form in terms of $F(R)=\frac{df(R)}{dR}$. Since we are dealing with a spherically symmetric problem, $F(R)$ is expressed as a radial function ${\cal F}(r)\equiv{F(R(r))}$. So, the choice of a specific form for $f(R)$ will be equivalent to adopt an Ansatz for ${\cal F}(r)$. By choosing an explicit functional form for ${\cal F}(r)$ we obtain the weak field solutions for the metric tensor, compute the time-like geodesics and analyse the motion of a massive test particle. An interesting feature is an emerging attractive force exerted by the monopole on the particle.
The neutrino behavior in the Einstein$\text{-}$Hilbert$\text{-}$Bumblebee gravity around global monopole field
College Pharmacy, Guizhou University of Traditional Chinese Medicine（贵州中医药大学药学院）；School of Science, Guiyang University（贵阳学院理学院）；College of Physics, Guizhou University（贵州大学物理学院）
We will construct a loop space formalism for general relativity, and construct the Polyakov variables as connections for such a loop space. We will use these Polyakov variables to construct a dual theory of gravity beyond linear approximation. It will be demonstrated that this loop space duality reduces to the Hodge duality for linearized gravity. Furthermore, a loop space curvature will be constructed from this Polyakov variable. It will be shown that this loop space curvature vanishes in the absence of topological defects, and so it can be used to investigate gravitational monopoles. We will…
Gravitating magnetic monopole via the spontaneous symmetry breaking of pure $R^2$ gravity
纯$R^2$引力等价于具有宇宙学常数和无质量标量场的爱因斯坦引力，并具有比标度对称性更大的所谓限制外尔对称性。考虑了由纯$R^2$引力、SU（2）Yang-Mills场和非最小耦合的无质量Higgs场（标量的三重态）组成的限制Weyl不变作用量。当限制的外尔对称自发破缺时，它等价于具有宇宙学常数的爱因斯坦-杨-米尔斯-希格斯（EYMH）作用量和大质量的希格斯粒子与引力的非最小耦合，即通过一个项$\tildeξ R |Φ|^2$。当限制外尔对称性没有自发破缺时，闵可夫斯基时空的线性化不会在原始$R^2$引力中产生引力子，因此它不会引力。然而，我们表明，在我们的理论的破规范部门，希格斯场获得非零真空期望值，闵可夫斯基时空是一个可行的引力背景解决方案。然后，我们得到了非零耦合常数$\tildeξ=1/6$在三种不同背景下的数值引力磁解：Minkowski，反德西特（AdS）和德西特（dS），所有这些都是在我们的限制Weyl不变量理论实现。
In this paper, we derive an exact black hole spacetime metric in the Einstein-Hilbert-Bumblebee (EHB) gravity around global monopole field. We study the horizon, temperature, and the photon sphere of the black hole. Using the null geodesics equation, we obtain the shadow cast by the Schwarzschild-like black hole with a topological defect in bumblebee gravity. Interestingly, the radius of shadow of the black hole increases with increase in the global monopole parameter. We also visualize the shadows and energy emission rates for different values of parameters. Moreover, using the Gauss-Bonnet t…
A theory with a global $O(3)$ symmetry broken at a scale $η$ admits topological configurations: global monopoles realized by Goldstone fields winding around the core of false vacuum. One may expect them to behave as heavy, big composite objects, difficult to make and therefore mostly harmless. However, after gravity is turned on, as long as Equivalence Principle holds, one finds that global monopoles have a negative mass, $M \sim - η/\sqrtλ$, where $λ$ is the field theory coupling. This could catalyze an instability in the space of a global monopole, by the production of additional global mono…
We investigate a braneworld model generated by a global monopole in the context of Brans-Dicke gravity. After solving the dynamical equations we found a model capable to alleviate the so-called hierarchy problem. The obtained framework is described by a hybrid compactification scheme endowed with a seven-dimensional spacetime, in which the brane has four non-compact dimensions and two curled extra dimensions. The relevant aspects of the resulting model are studied and the requirements to avoid the well known seesaw-like behavior are discussed. We show that under certain conditions it is possib…
我们证明了在拓扑质量电动力学的Maxwell-Chern-Simons理论中，狄拉克弦在反德西特空间中成为一个锥，锥的开角由拓扑质量决定，而拓扑质量又与宇宙学常数的平方根有关.这被证明是一个物理系统的例子，{ \it a priory}与引力完全无关，然而它的存在需要弯曲的时空。在Deser，Jackiw和Templeton的理论框架下，我们将这一结果推广到拓扑大质量引力与拓扑大质量电动力学的耦合。这些是具有圆锥亏额的齐次空间。耦合到麦克斯韦-陈-西蒙斯场的纯爱因斯坦引力不承认这样的解。
We investigate spin- and velocity-dependent contributions to the gravitational inter-particle potential. The methodology adopted here is based on the expansion of the effective action in terms of form factors encoding quantum corrections. Restricting ourselves to corrections up to the level of the graviton propagator, we compute, in terms of general form factors, the non-relativistic gravitational potential associated with the scattering of spin-0 and -1/2 particles. We discuss comparative aspects concerning different types of scattered particles and we also establish some comparisons with the…
