Theoretical Studies of Particles & Strings

我们的最终目标是理解物质和力的本质，以及整个宇宙的内容和演化。物理学家尤金·维格纳（Eugene Wigner）称之为“数学在自然科学中的不合理的有效性”，它能够为观察到的现象提供准确和预测性的描述。作为理论物理学家，我们通过激发和构建物理系统的数学模型来利用这一点，我们也尽可能地设计实验测试-因为这些最终是真理的仲裁者。我们的重点是物质的基本组成部分-粒子和可能构成它们的假设“弦”。创造和研究基本粒子需要像欧洲核子研究中心的大型强子对撞机这样的加速器。我们还利用自然粒子束，如南极冰立方实验研究的极端天体物理环境中产生的高能中微子。我们的研究解决了粒子和弦理论中的大多数当前问题。这个提议的一个新方向是设计新的实验室实验，使用量子传感器来寻找新物理现象的微妙影响。我们提议的第一部分是改进对强相互作用影响的预测，强相互作用主导了LHC碰撞中粒子的产生。这些碰撞产生了大量已知粒子的阵雨，这些粒子必须被过滤掉，以便能够看到指示新粒子存在的非常罕见的事件。希格斯玻色子的发现依赖于这样的计算;更多新粒子的发现和对其性质的有效分析将取决于更高精度的计算。我们将采用复杂的数学技术来计算复杂过程的“振幅”。强、弱和电磁相互作用的标准模型（SM）以极高的精度描述了实验数据，但它是不完整的。它不能解释为什么弱相互作用标度相对较低，或者为什么有三代夸克和轻子，并且它不包含引力。而且它也没有解释为什么宇宙中有物质而没有反物质，什么是暗物质。我们的研究探索了可能弥补这些缺陷的模型，并确定了什么样的实验测试对他们预测的新的“超越标准模型”的物理学敏感。大型强子对撞机也会碰撞重离子产生夸克胶子等离子体，这种等离子体很快达到热平衡，并影响高能粒子通过它的行为。为了了解这种强耦合流体的性质，我们将联合收割机与其他技术相结合的规范弦对偶技术。我们将探讨黑洞热力学之间的有趣联系。 标准模型的扩展经常预测新的粒子，这些粒子不能在LHC直接检测到，但可以影响天体物理学和宇宙学过程。一个例子是在大多数弦理论中自然产生的类轴子粒子，它的存在可以在天体物理信号中看到。我们建议的一个重要部分是详细建立这些粒子的签名，并设计新的策略，使用新型量子传感器在“桌面”实验中检测它们。我们也将使用高能宇宙微中子来探测新的现象，这些现象远远超出了大型强子对撞机所能达到的能量。弦理论是统一SM与引力的一个有希望的候选者。然而，一般来说，它们包含许多在自然界中没有观察到的状态;我们将继续我们的计划，以找到那些与SM一致的状态，并计算对应于观察到的粒子质量的“汤川耦合”。我们将探索数学模型，如“因果动力学三角剖分”，看看这些模型是否可以捕捉量子引力的物理学。

Our ultimate aim is to understand the nature of matter & forces, and the content & evolution of the universe as a whole. One of the most intriguing features of reality is what the physicist Eugene Wigner called "the unreasonable effectiveness of mathematics in the natural sciences" in being able to provide an accurate & predictive description of observed phenomena. As theoretical physicists we exploit this by motivating and constructing mathematical models of physical systems, for which we also devise experimental tests whenever possible - as these are ultimately the arbiter of truth.Our focus is on the fundamental constituents of matter - particles and the hypothetical 'strings' that may underlie them. To create and study elementary particles requires accelerators like the Large Hadron Collider at CERN. We also make use of natural particle beams like the high energy neutrinos generated in extreme astrophysical environments that are studied by the IceCube experiment at the South Pole. Our research addresses most of the current issues in particle & string theory. A new direction in this proposal is devising novel laboratory experiments using quantum sensors to look for subtle effects of new physical phenomena.The first part of our proposal is to improve predictions of the effects of the strong interactions that dominate the production of particles in collisions at the LHC. These collisions create showers of large numbers of known particles which have to be filtered out so that the very rare events indicating the presence of a new particle become visible. The discovery of the Higgs boson depended on such calculations; the discovery of further new particles and the efficient analysis of their properties will depend on doing those calculations to even higher precision. We will employ sophisticated mathematical techniques to calculate the 'amplitudes' which yield rates for complex processes. The Standard Model (SM) of the strong, weak & electromagnetic interactions describes experimenal data with exquisite precision but it is incomplete. It does not explain why the weak interaction scale is relatively low or why there are 3 generations of quarks & leptons, and it does not contain gravity. Moreover it does not explain why there is matter but no antimatter in the universe and what is the dark matter. Our research explores models that might remedy these defects and determine what experimental tests would be sensitive to the new 'beyond the Standard Model' physics they predict. The LHC also collides heavy ions producing a quark-gluon plasma which reaches thermal equilibrium quickly and affects the behaviour of energetic particles passing through it. To understand the properties of this strongly coupled fluid we will combine the gauge-string duality technique with other techniques. There are intriguing connections to the thermodynamics of black holes which we will explore. Extensions of the Standard Model often predict new particles that cannot be detected directly at the LHC but which can affect astrophysical & cosmological processes. An example is the axion-like-particle which arises naturally in most string theories and whose presence may be seen in astrophysical signals. An important part of our proposal is to establish in detail the signatures of such particles and devise new strategies using novel quantum sensors for detecting them in 'table top' experiments as well. We will also use high energy cosmic neutrinos to probe new phenomena well beyond the energies achievable at the LHC.String theories are a promising candidate for unifying the SM with gravity. However generally they contain many states not observed in Nature; we will continue our programme to find those consistent with the SM and calculate the 'Yukawa couplings' that correspond to observed particle masses. We will explore mathematical models such as 'causal dynamical triangulations' to see if these can capture the physics of quantum gravity.