Branes, Strings and Defects in Cosmology

宇宙学中的膜、弦和缺陷

• 批准号: ST/G000476/1
• 负责人: Mairi Sakellariadou
• 金额: $ 23.2万
• 依托单位: King's College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FG000476%2F1
• 关键词: Branes; Strings; Defects; Cosmology

For a number of years, inflation and topological defects have been considered either as two incompatible or as two competing aspects of modern cosmology. Historically, one of the reasons for which inflation was proposed is to rescue the standard hot Big Bang model from the monopole problem. However, such a mechanism could also dilute cosmic strings unless they were produced at the end or after inflation. Later on, inflation and topological defects competed as the two alternative mechanisms generating the density perturbations which led to the observed large-scale structure and the anisotropies in the Cosmic Microwave Background (CMB). The past decade has seen tremendous advances in cosmology. A plethora of data on the CMB has revealed an early universe in striking agreement with the basic predictions of inflation, while there is a clear inconsistency between predictions from topological defect models and CMB data. This indicates a clear preference for inflation. However, even though inflation provides a robust field theoretic mechanism which answers the shortcomings of the hot Big Bang cosmological model and is in a surprising agreement with CMB experiments, it still lacks a precise theoretical model. As the cosmological data keep improving fast, it becomes essential to find a specific inflationary model having a solid theoretical foundation. At present, it is widely believed that string theory is the fundamental theory of all matter and forces, including a consistent quantum gravity sector. If this is the case, then there must exist a natural inflationary scenario within string theory. Such an approach will allow the identification of the inflaton and the determination of its properties, while at the same time cosmological measurements will provide important insight on the precise stringy description of our universe. Since the 'discovery' of Dirichlet (D) branes, a natural realisation of our universe in string theory is the brane-world scenario. In this context, a simple, realistic and well-motivated inflationary model is brane inflation, where inflation takes place while two branes move towards each other, and their annihilation releases the brane tension energy that heats up the universe to start the hot Big Bang era. Typically, strings of all sizes and types may be produced during the collision. Large fundamental (F) strings and/or D1-branes (D-strings) that survive the cosmological evolution become cosmic superstrings. By observing strings in the sky, we will be able to test, for the first (and maybe only) time, string theory. It is now widely accepted that cosmic strings are generically formed in both supersymmetric grand unified theories and brane inflation, where the inflaton potential is of the hybrid type and the inflationary phase ends with a phase transition, leaving behind a network of cosmic strings. Thus, strings and inflation must reconciliate. The aim of our proposal is to identify a successful cosmological model motivated by string theory, which can explain the dimensionality of space-time and give origin to an inflationary model, as well as to seek observational tests of string theory, through mainly the imprint of cosmic superstrings. In the framework of type IIB string theory we will develop a mechanism which can account for the origin of space-time dimensionality through brane interactions. In such a context brane inflation may appear and its phenomenological characteristics will constrain the model. Brane annihilation will release the energy of the branes, reheating the universe which will thus enter the radiation-dominated era. By studying properties of such networks, which have a number of similarities but also a number of differences from field theory cosmic strings, and their phenomenological consequences, we expect to pin down the successful and 'natural' inflationary model.

多年来，暴胀和拓扑缺陷被认为是现代宇宙学中两个不相容或相互竞争的方面。从历史上看，提出暴胀理论的原因之一是为了将标准的热大爆炸模型从单极子问题中拯救出来。然而，这种机制也会稀释宇宙弦，除非它们是在膨胀结束或之后产生的。后来，膨胀和拓扑缺陷作为产生密度扰动的两种替代机制相互竞争，导致了宇宙微波背景（CMB）中观测到的大尺度结构和各向异性。过去的十年见证了宇宙学的巨大进步。关于CMB的大量数据揭示了一个与暴胀基本预测惊人一致的早期宇宙，而拓扑缺陷模型的预测与CMB数据之间存在明显的不一致。这表明美联储明显倾向于通胀。然而，尽管暴胀提供了一个强大的场论机制，弥补了热大爆炸宇宙学模型的缺陷，并且与CMB实验惊人地一致，但它仍然缺乏一个精确的理论模型。随着宇宙学数据的快速改进，寻找一个具有坚实理论基础的特定暴胀模型变得至关重要。目前，人们普遍认为弦理论是所有物质和力的基本理论，包括一致的量子引力。如果是这样的话，那么在弦理论中必然存在一个自然的暴胀情景。这种方法将使我们能够识别暴胀并确定其性质，同时，宇宙学测量将为我们宇宙的精确弦描述提供重要的见解。自从“发现”狄利克雷(D)膜以来，在弦理论中我们的宇宙的一个自然实现是膜世界的场景。在这种背景下，一个简单、现实且动机良好的暴胀模型是膜暴胀，当两个膜相互靠近时发生暴胀，它们的湮灭释放出膜张力能量，使宇宙升温，开始了热大爆炸时代。通常，所有大小和类型的字符串都可能在碰撞期间产生。大的基本弦(F)和/或d1膜（d弦）在宇宙演化中幸存下来，成为宇宙超弦。通过观察天空中的弦，我们将能够第一次（也可能是唯一一次）检验弦理论。现在人们普遍认为，宇宙弦一般是在超对称大统一理论和膜暴胀中形成的，其中暴胀势是混合型的，暴胀阶段以相变结束，留下一个宇宙弦网络。因此，字符串和膨胀必须协调一致。我们的提议的目的是确定一个由弦理论驱动的成功的宇宙学模型，该模型可以解释时空的维度并给出暴胀模型的起源，同时主要通过宇宙超弦的印记寻求弦理论的观测测试。在IIB型弦理论的框架下，我们将发展一种机制来解释时空维度通过膜相互作用的起源。在这种情况下，可能会出现膜膨胀，其现象学特征将约束模型。膜湮灭将释放膜的能量，重新加热宇宙，从而进入辐射主导的时代。通过研究这些网络的特性，它们与场论宇宙弦有许多相似之处，但也有许多不同之处，以及它们的现象学结果，我们希望能确定成功的“自然”暴胀模型。

项目成果

On degenerate models of cosmic inflation

• DOI: 10.1088/1475-7516/2014/10/005
• 发表时间: 2014-06
• 期刊: Journal of Cosmology and Astroparticle Physics
• 影响因子: 6.4
• 作者: R. Gwyn;G. Palma;M. Sakellariadou;Spyros Sypsas

Zipping and unzipping in string networks: Dynamics of Y-junctions

弦网络中的压缩和解压缩：Y 形结点的动力学

• DOI: 10.1103/physrevd.91.025022
• 发表时间: 2015
• 期刊: Physical Review D
• 影响因子: 5
• 作者: Avgoustidis A

Theoretical constraints on brane inflation and cosmic superstring radiation

膜膨胀和宇宙超弦辐射的理论约束

• DOI: 10.1007/jhep09(2011)075
• 发表时间: 2011
• 期刊: Journal of High Energy Physics
• 影响因子: 5.4
• 作者: Gwyn R

Effective field theory of weakly coupled inflationary models

• DOI: 10.1088/1475-7516/2013/04/004
• 发表时间: 2012-10
• 期刊: Journal of Cosmology and Astroparticle Physics
• 影响因子: 6.4
• 作者: R. Gwyn;G. Palma;M. Sakellariadou;Spyros Sypsas

Initial Conditions for Non-Canonical Inflation

非典型通货膨胀的初始条件

• DOI: 10.48550/arxiv.1002.2639
• 发表时间: 2010
• 作者: Franche P