Inflationary dynamics in the braneworld scenarios

We analyze the attractor behaviour of the inflation field in braneworld scenarios using the Hamilton-Jacobi formalism, where the Friedmann equation has the form ofH2 = p ＋ εx/2poporH2 = p ＋εp2/2σ, with ε = ±1. We find that in all models the linear homogeneous perturbation can decay exponentially as the scalar field rolls down its potential. However, in the case of a -p2 correction to the standard cosmology with p 〈 or, the existence of an attractor solution requires （σ- p）/φ2 〉 1. Our results show that the perturbation decays more quickly in models with positive-energy correction than in the standard cosmology, which is opposite to the case of negative-energy correction. Thus, the positive-energy modification rather than the negative one can assist the inflation and widen the range of initial conditions.

Spherically Symmetric Wormhole Gravitational Lens Deflection Angle Signifying Braneworld Cosmology

Previously, the gravitational lens of a wormhole was introduced by various researchers. Their treatment was focused basically on the lens signature that describes wormhole geometrical character such as the differences from a black hole or between any various types of wormhole models. The braneworld scenario provides the idea of spacetime with underlying extra-dimensions. The inclusion of extra-dimensional terms in the lens object spacetime line element will result in some variation in the expression for its gravitational lens deflection angle. Thus in this paper we investigate such variation by deriving this deflection angle expression. As such, this paper not only shows the existence of such variation but also suggests the potential utilization of gravitational lensing to prove the existence of extra dimensions by studying the deflection angle characteristic in accordance with the spacetime expansion rate of the universe.

Braneworld Black Hole Gravitational Lensing

A class of braneworld black holes, which I called as Bronnikov–Melnikov–Dehen(BMD) black holes,are studied as gravitational lenses. I obtain the deflection angle in the strong deflection limit, and further calculate the angular positions and magnifications of relativistic images as well as the time delay between different relativistic images. I also compare the results with those obtained for Schwarzschild and two braneworld black holes, i.e., the tidal Reissner-Nordstr¨om(R-N) and the Casadio–Fabbri–Mazzacurati(CFM) black holes.

Traversable braneworld wormholes supported by astrophysical observations

In this study, we investigate the characteristics and properties of a traversable wormhole constrained by the current astrophysical observations in the framework of modified theories of gravity （MOG）. As a concrete case, we study traversable wormhole space-time configurations in the Dvali-Gabadadze- Porrati （DGP） braneworld scenario, which are supported by the effects of the gravity leakage of extra dimensions. We find that the wormhole space-time structure will open in terms of the 2o confidence level when we utilize the joint constraints supernovae （SNe） Ia ＋ observational Hubble parameter data （OHD） ＋ Planck ＋ gravitational wave （GW） and z 〈 0.2874. Furthermore, we obtain several model-independent conclusions, such as （i） the exotic matter threading the wormholes can be divided into four classes during the evolutionary processes of the universe based on various energy conditions; （ii） we can offer a strict restriction to the local wormhole space-time structure by using the current astrophysical observations; and （iii） we can clearly identify a physical gravitational resource for the wormholes supported by astrophysical observations, namely the dark energy components of the universe or equivalent space-time curvature effects from MOG. Moreover, we find that the strong energy condition is always violated at low redshifts.

D-term Chaotic Braneworld in Supergravity Constrained by WMAP9 Data

We study a supergravity D-term chaotic inflationary model, in the context of the braneworld scenario, in particular we consider the Randal1-Sundrum model type 2. Using the latest release from the combination of WMAP9, eCMB, BAO, and Ho, we show that the inflation observables depend only on the number ore-folds N. We also derive all known spectrum inflationary parameters, which are widely consistent with WMAP9 data for a particular choice of values N specially for the scalar spectral index ns and the ratio r. However, the running of the scalar spectral index dns/dlnk is now excluded from the range given by the latest observational measurements.

额外维与厚膜模型简介

额外维概念的提出已有近百年的历史,但直到最近二十余年,人们对额外维物理的认识才发生了实质性的转变。例如,人们开始注意到额外维的尺度可以达到Te V-1量级甚至是无穷大的,而不与当前的实验观测相违背。一些额外维模型还可以对粒子物理学中的规范层次问题以及宇宙学中的暗物质问题给出全新的解释。此外,如果将我们所处的四维世界看成是更高维时空中的拓扑缺陷,例如五维时空中的一个四维畴壁,则可以通过场论的方法得到局域在畴壁上的各种四维物质场。如果进一步要使四维牛顿引力也能被局域在畴壁上,一般需要假设五维时空按照某种方式弯曲。这种弯曲时空中的畴壁称为厚膜。最简单的解析厚膜解可以在广义相对论中通过引入最小耦合的背景标量场得到。随着宇宙学的发展,越来越多的扩展引力理论和非最小耦合的标量场相继被提出并被应用于宇宙学和高能物理的各种问题中。因此研究各种扩展引力和非最小耦合标量场理论中的解析厚膜解和各种场的局域化机制就成了一个重要而又有趣的方向。目前国内外对厚膜模型的研究已经取得了一系列的研究成果,我们将对这一领域的相关研究进行简单的介绍。本文先对几种常见的额外维模型包括Kaluza-Klein理论、大额外维模型、Randall-Sundrum模型和标准的厚膜模型进行简单介绍,并分析线性涨落和引力场的局域化。然后介绍厚膜背景下各种物质场的局域化机制。最后以非正则标量场论和几种常见的扩展引力理论为例,介绍厚膜模型的相关研究进展。

膜模型中黑洞的Dirac似正规模

讨论了Randall-Sundrum双膜模型中Reissner-Nordstrom-like黑洞的无质量Dirac场扰动.随着参数Q*的增加,扰动场势函数的势垒峰值逐渐减小,而峰值所在的位置则沿着x轴向右移动.在低频条件下,三阶WKB近似方法给出了无质量Dirac似正规模频率的数值结果.研究表明,Randall-Sundrum双膜模型中的黑洞在无质量Dirac扰动随时间的演化过程中是趋于稳定的.

Phantom-Like Effects on Warped DGP Brane

We study phantom-like effect on the DGP brane embedded in a five-dimensional AdS bulk. We show that this effect can be realized without phantom matter on this warped DGP brahe. We investigate the role played by the bulk cosmological constant on the phantom-like effect on the brane and we show that it tends to reduce this effect. Also, warped compactification of the bulk manifold increases the values of the effective and total equation of state parameters of the model relative to the case with Minkowski bulk. We extend our study to the ease that induced curvature on the brahe is modified in the spirit of the f（R）-gravity.

Variation of Vacuum Energy if Scale Factor Becomes Infinitely Small, with Fixed Entropy Due to a Non Pathological Big Bang Singularity Accessible to Modified Einstein Equations

When initial radius Rinitial 0 if Stoica actually derived Einstein equations in a formalism which remove the big bang singularity pathology, then the reason for Planck length no longer holds. The implications of Rinitial 0 are the first part of this manuscript. Then the resolution is alluded to by work from Muller and Lousto, as to implications of entanglement entropy. We present entanglement entropy in the early universe with a steadily shrinking scale factor, due to work from Muller and Lousto, and show that there are consequences due to initial entanged Sentropy=0.3rH2/a2 for a time dependent horizon radius rH in cosmology, with for flat space conditions rH= for conformal time. In the case of a curved, but not flat space version of entropy, we look at vacuum energy as proportional to the inverse of scale factor squared times the inverse of initial entropy, effectively when there is no initial time in line with ~H2/G H≈a-1. The consequences for this initial entropy being entangled are elaborated in this manuscript. No matter how small the length gets, Sentropy if it is entanglement entropy, will not go to zero. The requirement is that the smallest length of time, t, re scaled does not go to zero. Even if the length goes to zero. This preserves a minimum non zero vacuum energy, and in doing so keep the bits, for computational bits cosmological evolution even if Rinitial 0.

Cosmic Initial Singularities in a Single Repeating Universe as Opposed to Their Behavior in a Multiverse

When the initial radius of the universe is set in four dimensions and if there is only ONE repeating universe, then the initial radii of the universe is R → 0 or gets very close to zero if we use the Einstein Equations modified by Stoica. The Einstein Equations are reset by Stoical in a formalism which removes in four dimensions, the big bang singularity pathology. So then the reason for Planck length no longer holds. This manuscript assumes a repeating single universe. We present entanglement entropy in the early universe with a shrinking scale factor, due to Muller and Lousto, and show that there are consequences due to initial entangled for a time dependent horizon radius in cosmology, with (flat space conditions) for conformal time. Even if the 3-dimensional spatial length goes to zero. Our new manuscript presentation sets as a starting point a cosmology with a non-zero Λ vacuum energy. The non-zero Λ vacuum energy, initial configuration of the universe permits us to keep in an information theory stand point (information theory), computational bits for our configuration of cosmological expansion. This assemblage of computational bits occurs in cosmological evolution even if in an initial four-dimensional cosmology, we have the initial radii of the universe R → 0. We also find that in the case of a multiverse, such considerations will not hold and that cosmic singularities have a more different characteristic in the multiverse setting than in the single universe repeated over and over again, i.e. using an argument borrowed and modified from Kauffman, the multiverse will not mandate “perfect” singularities. The existence of a multiverse may allow for non zero singularities in lieu with the Kauffman argument cited at the end of the document, plus the lower pre big bang temperatures which may allow for the survival of gravitons just before the onset of the cosmological expansion phase, if a multiverse exists embedding our present universe.

Asking If the Existence of Vacuum Energy to Keep Computational “Bits” Present at Start of Cosmological Evolution, Even If Spatial Radius Goes to Zero, Not Planck Length, Is Possible

When initial radius Rinitial →0 if Stoica actually presents Einstein equations in a formalism which remove the big bang singularity pathology, then the reason for Planck length no longer holds. We present entanglement entropy in the early universe with a shrinking scale factor, due to Muller and Lousto, and show that there are consequences due to initial entangled SEntropy = 0.3r2h/a2 for a time dependent horizon radius rH = in cosmology, with (flat space conditions) for conformal time. Even if the 3 dimensional spatial length goes to zero, this construction preserves a minimum non-zero L vacuum energy, and in doing so keep the bits, for computational bits cosmological evolution even if Rinitial →0 . We state that the presence of computational bits is necessary for cosmological evolution to commence.

Kalb-Ramond field localization on a thick de Sitter brane

In this paper,we explore the localization condition of Kalb-Ramond(KR)tensorial gauge field on a thick de Sitter(dS)brane.Following the localization mechanism in the work by Chumbes et al(2012 Phys.Rev.D 85085003),we analyze the localization of KR tensorial gauge field on a non-flat three-brane.We propose three kinds of coupling methods and two of them support the localization of zero mode.In addition,there exist resonant Kaluza-Klein modes on the thick dS brane.The effects of three parameters on the localization and the resonant mode for the KR field are also discussed.