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）所说的“数学在自然科学中不可思议的有效性”是现实中最有趣的特征之一，它能够对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，为此我们还尽可能设计实验测试——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想“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，比如在极端天体物理环境中产生的高能中微子，南极冰立方实验研究了这种粒子束。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的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，强相互作用在大型强子对撞机的碰撞中主导着粒子的产生。这些碰撞产生了大量的已知粒子，这些粒子必须被过滤掉，这样才能使表明新粒子存在的非常罕见的事件变得可见。希格斯玻色子的发现就依赖于这样的计算；进一步新粒子的发现和对其性质的有效分析将依赖于更高精度的计算。我们将采用复杂的数学技术来计算复杂过程的产率的“振幅”。强、弱和电磁相互作用的标准模型（SM）对实验数据的描述非常精确，但它是不完整的。它没有解释为什么弱相互作用尺度相对较低，或者为什么有3代夸克和轻子，而且它不包含重力。此外，它也没有解释为什么宇宙中有物质而没有反物质，以及什么是暗物质。我们的研究探索可能弥补这些缺陷的模型，并确定哪些实验测试将对他们预测的新的“超越标准模型”物理学敏感。大型强子对撞机还会碰撞重离子，产生夸克-胶子等离子体，这种等离子体能迅速达到热平衡，并影响穿过它的高能粒子的行为。为了了解这种强耦合流体的性质，我们将把量规管柱对偶技术与其他技术结合起来。这与我们将要探索的黑洞热力学有着有趣的联系。标准模型的扩展通常预测无法在大型强子对撞机直接检测到的新粒子，但它们会影响天体物理和宇宙学过程。一个例子是在大多数弦理论中自然出现的类轴子粒子，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特征，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。我们还将使用高能宇宙中微子来探测远远超出大型强子对撞机所能达到的能量的新现象。弦理论是统一SM和引力的一个很有希望的候选者。然而，它们通常包含许多在自然界中没有观察到的状态；我们将继续我们的程序来找到那些与SM一致的，并计算与观测到的粒子质量相对应的“汤川耦合”。我们将探索数学模型，如“因果动态三角测量”，看看它们是否能捕捉量子引力的物理特性。

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.