We study a flat brane solution in an effective 5D action for cascading gravity and propose a mechanism to screen extrinsic curvature in the presence of a large tension on the brane. The screening mechanism leaves the bulk Riemann-flat, thus making it simpler to generalize large extra dimension dark energy models to higher codimensions. By studying an action with cubic interactions for the brane-bending scalar mode, we find that the perturbed action suffers from ghostlike instabilities for positive tension, whereas it can be made ghost-free for sufficiently small negative tension.
String tension fundamentally determines the properties of strings; yet its value is often assigned arbitrarily, creating a fine-tuning problem. We describe a mechanism for dynamically generating string tension in a flat or almost flat spacetime, using the modified measures formalism, which in turn naturally generates a new type of stringy brane-world scenario. Such a scenario allows strings to achieve near infinite tension confining the strings to two very close expanding surfaces, but the infinite tensions also threatens to distort the near-flat embedding spacetime through large back reaction…
We study the behaviour of weak gravitational fields in the 6D Cascading DGP model using a bulk-based approach. To deal with the ambiguity in the thin limit of branes of codimension higher than one, we consider a specific regularization of the internal structure of the branes where the 5D brane can be considered thin with respect to the 4D one. We consider the solutions corresponding to pure tension sources on the 4D brane, and study perturbations at first order around these background solutions. We adopt a 4D scalar-vector-tensor decomposition, and focus on the scalar sector of perturbations. …
我们引入了具有非恒定张力的膜世界，加强了与流体膜的类比，根据Eötvös建立的经验定律，流体膜表现出温度依赖性。这个新的自由度允许演化引力和宇宙学常数，后者是暗能量的自然候选者。通过考虑非对称嵌入膜和5维时空中的非标准模型场，我们建立了具有可变张力的膜上的协变动力学。然后，我们应用形式主义的一个弗里德曼膜上的完美流体，这是嵌入在一个5维带电Vaidya-Anti de Sitter时空。
We propose an action for unstable Dp-brane with dynamical tension. We show that the equations of motion are equivalent to the equations of motion derived from DBI and WZ actions for non-BPS Dp-brane. We also find Hamiltonian formulation of this action and analyze properties of the solutions corresponding to the tachyon vacuum and zero tension solution.
We compute the holographic quark potential in the realm of brane cosmology. We show that under certain conditions the very geometry due to an inflationary 3-brane induces a D3-D7-brane system. The cosmological constant that appears involved in the original geometry is attributed to the D7-brane position itself in its embedding process. We address the issues of confinement at low distances, screening effects at sufficiently large distances, and quark condensate.
Quantum effects, brane tension and large hierarchy in the brane-world
在S^1/Z2紧化的膜世界情形下，研究了具有负宇宙学常数和共形不变体物质场的五维半经典爱因斯坦方程.当玻色子场和费米子场的个数N_{b,f}满足I<κ ^2 l ^{-3}（N_b-N_f）<32 I时，我们得到了一个精确的半经典解，它有两个正张力的静态膜，并且它的翘曲因子可以任意大.在这里，κ^2是五维引力常量，l是由负五维宇宙学常数决定的长度尺度，而$I$是一个正的无量纲常数。然而，为了获得一个大的翘曲因子，膜张力的微调是必需的。因此，为了解决层级问题，我们需要通过另一种新机制来证明微调的合理性。
There is great interest in the construction of brane worlds, where matter and gravity are forced to be effective only in a lower dimensional surface , the brane . How these could appear as a consequence of string theory is a crucial question and this has been widely discussed. Here we will examine a distinct scenario that appears in dynamical tension theories and where string tension is positive between two surfaces separated by a short distance and at the two surfaces themselves the string tensions become infinite, therefore producing an effective confinement of the strings and therefore of a…
The constraint of trans-Planckian censorship conjecture on brane inflation model is considered. The conjectures put an upper bound on the main parameter including temperature, inflation time, potential, and the tensor-to-scalar ratio parameter $r$. It is determined that the resulting constraint could be more stronger than what we have for the standard inflationary models. The constraint in general depends on the brane tension and it is concluded that the conjecture also confined the value of brane tension in order to have consistency for the model. Confining the brane tension turns into a dete…
