Fields, Strings and Lattices: From the Inflationary Universe to High-Energy Colliders

场、弦和晶格：从暴胀宇宙到高能对撞机

• 批准号: ST/P00055X/1
• 负责人: Gert Aarts
• 金额: $ 126.78万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FP00055X%2F1
• 关键词: Fields; Strings; Lattices; Inflationary; Universe

Research in particle physics and cosmology connects the largest scales, those of the Universe as a whole, with the smallest, namely those of fundamental particles and strings. By trying to understand how the Universe evolved after the Big Bang, we may gain insight into which particles are yet to be discovered at e.g. the Large Hadron Collider at CERN, and vice versa, a fascinating prospect!It is commonly assumed that the early Universe went through a period of rapid expansion, dubbed inflation. The mechanisms underlying inflation can be investigated in a number of ways. In the so-called bottom-up approach, one aims to find predictions that are independent of details of models, but only depend on symmetries and the nature of the source of inflation. It is then possible to extract universal features leading to observational predictions and point towards physics beyond our currently known Standard Models of Particle Physics and Cosmology. In the complementary top-down approach, one starts with the given theory, e.g. one that is motivated by string theory, and derives its consequences, which, again might be testable by observations. These approaches can also be used to study the period of cosmic acceleration our Universe is currently going through, i.e. dark energy.String theory is a theory of gravity (and other forces) operating at very high-energy scales. Besides its possible role as a fundamental theory, it has many intricate aspects which require a level of understanding deeply rooted in symmetries and dualities (a transformation that leads to two 'dual' formulations which are superficially very different but yet equivalent). By studying those, one may not only understand string theory better, but also arrive at dual theories which are relevant for e.g. physics beyond the Standard Model (BSM) probed at the LHC, especially if the BSM model is strongly coupled.In order to make predictions for the LHC, it is necessary to perform very precise calculations, in BSM models and in the Standard Model itself. Some of these calculations can be done by expanding in a small parameter. This does not mean that the computation is easy though, since many scattering processes may contribute. However, it might be that by re-organising these contributions a new, more efficient, formulation can be found.When there is no small parameter, a theory has to be solved as it stands. Often this can be attempted numerically, by formulating it on a space-time lattice. Since this involves very many degrees of freedom, typically one has to employ the largest supercomputers in the world. The theory of the strong interaction, Quantum Chromodynamics (QCD), is one of those theories in which a small parameter is absent. Although it is formulated in the terms of quarks (as matter particles) and gluons (as force carriers), these are not the particles that appear in the spectrum, which are instead protons, neutrons, pions etc. However, since QCD is so hard to solve, there may be other particles not yet detected and also not yet understood theoretically: examples are so-called glueballs and hybrid mesons. By studying QCD on the lattice, these ideas can be tested quantitatively.A related question concerns what happens with all these particles when the temperature (as in the early Universe) or the matter density (as in neutron stars) is increased. Also this can be studied numerically and a transition to a new phase of matter at high temperature, the quark-gluon plasma, has been observed. Since this phase is currently being explored at the LHC, by colliding heavy ions, quantitative predictions on the spectrum and on transport properties, such as how viscous the plasma is, are needed here as well. Some BSM models also lack a small parameter and hence are studied using similar lattice computing techniques. By scanning models with distinct features, again hints for the LHC may be found, e.g. with regard to unusual spectral features.

粒子物理学和宇宙学的研究将最大的量表（与整个宇宙的尺度联系在一起，即最小的尺度，即基本颗粒和弦的尺度。通过试图了解大爆炸后宇宙的发展，我们可能会深入了解哪些粒子尚未在例如CERN的大型强子对撞机，反之亦然，这是一个引人入胜的前景！通常认为早期的宇宙经历了一个快速扩张的时期，称为通货膨胀。通货膨胀基础的机制可以通过多种方式进行研究。在所谓的自下而上的方法中，一个人的目的是找到独立于模型细节的预测，但仅取决于对称性和通货膨胀来源的性质。然后，可以提取通用特征，从而导致观察性预测，并指向我们当前已知的粒子物理和宇宙学标准模型之外的物理学。在互补的自上而下的方法中，一个从给定理论开始，例如一个是由弦理论激励的，并导致其后果，这再次可以通过观察结果来检验。这些方法也可以用来研究我们宇宙目前正在经历的宇宙加速期的时期，即暗能理论是一种在非常高的能量尺度上运行的重力理论（和其他力）。除了它作为基本理论的可能作用外，它还具有许多复杂的方面，这些方面需要一定程度的理解水平，根深蒂固地植根于对称性和二元性（这种转换会导致两个“双重”表达式，它们表面上非常不同，但相当于相等）。通过研究这些，人们不仅可以更好地了解弦理论，而且还达到了与例如在LHC上探测的标准模型（BSM）之外的物理学，尤其是如果BSM模型紧密耦合。为了对LHC进行预测，必须在BSM模型和标准模型本身中执行非常精确的计算。这些计算中的一些可以通过扩展小参数来完成。但是，这并不意味着计算很容易，因为许多散射过程可能会造成任何贡献。但是，可能是通过重新组织这些贡献，可以找到一种新的，更有效的表述。当没有小参数时，必须在其上解决这一理论。通常，可以通过在时空晶格上对其进行数字尝试。由于这涉及非常多的自由度，因此通常必须使用世界上最大的超级计算机。强相互作用的理论量子染色体动力学（QCD）是缺乏小参数的理论之一。尽管它是按照夸克（作为颗粒）和弹性（作为力载体）的术语进行的，但这些不是出现在频谱中的颗粒，而是质子，中子，山皮等。但是，由于QCD很难求解，因此可能尚未检测到其他粒子，并且尚未被检测到的其他粒子，也尚未被理解为理论上的glue bliue and the the the the the bellue and hy n. nhybrid nor brid blar ner grid brid brid brid。通过在晶格上研究QCD，可以定量测试这些想法。一个相关的问题涉及当温度（如早期宇宙中）或物质密度（如中子恒星中）增加时，所有这些颗粒会发生什么。同样，这可以在数值上进行研究，并在高温下向新的物质阶段过渡，已经观察到了夸克 - 杜伦等离子体。由于目前正在LHC探索此阶段，因此在这里也需要在频谱和传输特性上进行定量预测，例如等离子体的粘性等离子。一些BSM模型也缺乏小参数，因此使用类似的晶格计算技术研究了。通过具有不同特征的扫描模型，可以找到LHC的提示，例如关于异常光谱特征。

项目成果

Medium effects and parity doubling of hyperons across the deconfinement phase transition

超子在解禁相变过程中的中等效应和宇称倍增

• DOI: 10.1051/epjconf/201817507016
• 发表时间: 2018
• 期刊: EPJ Web of Conferences
• 作者: Aarts G

Mesonic correlators at non-zero baryon chemical potential

非零重子化学势的介子相关器

• DOI: 10.48550/arxiv.2001.04415
• 发表时间: 2020
• 作者: Aarts G

Heavy-flavor production and medium properties in high-energy nuclear collisions --What next?

• DOI: 10.1140/epja/i2017-12282-9
• 发表时间: 2016-12
• 期刊: The European Physical Journal A
• 作者: G. Aarts;J. Aichelin;C. Allton;R. Arnaldi;S. Bass;C. Bedda;N. Brambilla;E. Bratkovskaya

Lattice QCD at nonzero temperature and density

• DOI: 10.1088/1742-6596/2207/1/012055
• 发表时间: 2021-11
• 期刊: Journal of Physics: Conference Series
• 作者: G. Aarts;C. Allton;S. Hands;B. Jäger;S. Kim;M. Lombardo;A. Nikolaev;S. Ryan;J. Skullerud

Parity doubling of nucléons, Delta and Omega baryons across the deconfinement phase transition

核子、Delta 和 Omega 重子在解禁闭相变过程中宇称倍增

• DOI: 10.1051/epjconf/201713707004
• 发表时间: 2017
• 期刊: EPJ Web of Conferences
• 作者: Aarts G