Fresh perspectives for QED in intense backgrounds: first quantised techniques in strong field QED

强背景下 QED 的新视角：强场 QED 中的首个量化技术

• 批准号: EP/X02413X/1
• 负责人: James Edwards
• 金额: $ 30.51万
• 依托单位: Plymouth University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX02413X%2F1
• 关键词: Fresh; perspectives; QED; intense; backgrounds

Quantum electrodynamics (QED) governs the way that light and matter interact and it is our best-tested theory of fundamental physics. Problems in QED can very often be approached, as with other physics problems, in an approximate scheme called perturbation theory. Here one performs calculations to low order in a suitably small expansion parameter, which in QED is the well-known "fine structure constant" proportional to the square of the electric charge. Going to sequentially higher orders in perturbation theory may provide higher precision results, but advances are now required in regimes of very high orders, or even all orders, to obtain meaningful theoretical insight and make sufficiently precise experimental predictions. Such a situation occurs in laser-matter interactions, and the associated higher order calculations are prohibitively challenging. Modern laser facilities create pulses of intense light with very high photon density, often focussing the equivalent of the total light emitted by the sun onto the head of a pin. The interaction of laser photons with matter adds coherently, so these great numbers of incident photons imply that the laser-matter coupling effectively becomes enhanced, from the fine-structure constant to the so-called "dimensionless intensity parameter." This parameter easily exceeds unity at current facilities - and future experiments will reach values of 10 to 100 - which clearly demands a non-perturbative treatment. Fortunately, such an approach to laser-matter interactions is made possible by the "Furry expansion," can be thought of as an improved perturbation theory that includes the effects of laser photons, thereby accounting for large values of the dimensionless intensity parameter. This is the theoretical backbone of essentially all previous, current, and future intense laser experiments.However, the Ritus-Narozhny conjecture states that as we go ever higher intensities, quantum "loop" effects, which are typically neglected even in the Furry expansion, also become enhanced by laser intensity, to such an extent that all loop orders need to be accounted for -- in effect, the Furry expansion breaks down, leaving us without our key theoretical tool. More than simply a technical or mathematical problem, the intriguing implication of the Ritus-Narozhny conjecture is that the high-intensity regime of QED is fully non-perturbative, or "strongly coupled" and therefore inaccessible to standard approximation schemes. We are therefore currently unable to give any concrete predictions for the physics of this regime, or to answer other questions on the very high intensity behaviour of QED, because non-perturbative calculations in strong fields are prohibitively difficult, at least with the standard techniques employed by the community. Understanding the physics of the high-intensity regime, and identifying "smoking gun" signals of new effects which can be searched for at future experiments, is therefore a challenge which requires new methods.Worldline techniques are highly valued in quantum field theory for their calculational efficiency, yet their usefulness in SFQED has only recently been noticed, and the take-up of such methods in the UK has been very limited. This project will develop the worldline methods required for studying QFT in electromagnetic backgrounds and apply them to strong field problems. Of particular interest is the ability, in the worldline formalism, to derive "master formulae" for whole classes of higher-order processes; this is something which is currently lacking in strong fields, but which is required if we are to understand the physics of the high-intensity regime where higher order effects become important. The project will support national diffusion of expertise in the worldline approach, to the UK and EU SFQED community, and will shed new light on perturbative and non-perturbative aspects of matter in intense laser fields.

量子电动力学（QED）控制着光与物质相互作用的方式，这是我们最好的基本物理学理论。 QED中的问题通常与其他物理问题一样，在称为扰动理论的近似方案中也可以解决。在这里，一个人在适当的膨胀参数中执行计算，该参数在QED中是众所周知的“良好结构常数”，与电荷正方形成正比。在扰动理论中依次更高的阶段可以提供更高的精度结果，但是现在在非常高阶甚至所有秩序的制度中需要进步才能获得有意义的理论洞察力并做出足够精确的实验预测。这种情况发生在激光互动中，相关的高阶计算受到了极大的挑战。现代激光设施创造出具有很高光子密度的强光的脉冲，通常将相当于太阳发出的总光的等效物放在销钉的头上。激光光子与物质的相互作用相互添加，因此这些大量的入射光子暗示激光耦合有效地增强，从细胞结构常数到所谓的“无量纲强度参数”。该参数很容易超过当前设施的统一 - 未来的实验将达到10至100的值，这显然需要非扰动治疗。幸运的是，通过“毛茸茸的膨胀”使这种激光相互作用的方法成为可能，可以将其视为一种改进的扰动理论，其中包括激光光子的效果，从而考虑了无量纲强度参数的较大值。这是本质上所有以前的，现在和未来强烈激光实验的理论骨干。但是，但是，无论如何，随着我们的强度越高，量子“循环”的效果，即使在毛茸茸的效果中也可以增强，因此，在激光范围内，量子的扩展也很可能会忽略 - 在这种范围内，这些效果也通常是忽略的 - 在这种范围内也可以在此范围内延伸，以至于有范围的效果 - 在此类范围内，这是在此类范围内的效果，以至于范围内的效果，以至于范围内的效果，以至于有范围的效果，以至于有范围的效果，以至于范围内的效果，这一效果是在此类范围内的效果，并且可以在此范围内延伸。让我们没有关键的理论工具。不仅仅是技术或数学问题，Ritus-narozhny猜想的有趣含义是，QED的高强度制度是完全非扰动性的，或“强烈耦合”，因此与标准近似方案无法访问。因此，我们目前无法对该制度的物理学给出任何具体的预测，或者回答有关QED高强度行为的其他问题，因为在强领域中的非扰动计算非常困难，至少在社区采用的标准技术方面非常困难。因此，了解高强度制度的物理学，并确定可以在未来实验中搜索的“吸烟枪”信号，因此是一个需要新方法的挑战。Worldline技术在量子现场理论中高度重视其计算效率，但在SFQED中的实用性最近才注意到了这类方法，并且已经非常有限地受到了限制。该项目将开发在电磁背景中研究QFT所需的世界方法，并将其应用于强烈的现场问题。特别令人感兴趣的是，在全球形式主义中，能够为整个高阶过程提供“主公式”。这是目前缺乏强大领域的东西，但是如果我们要了解高阶效应变得重要的高强度制度的物理学，这是必需的。该项目将支持全国范围内的专业知识在全球范围内，英国和欧盟SFQED社区的扩散，并将为强烈激光领域的物质扰动和非扰动方面提供新的启示。

项目成果

Master formulas for N -photon tree level amplitudes in plane wave backgrounds

平面波背景中N光子树级振幅的主公式

• DOI: 10.1103/physrevd.109.065003
• 发表时间: 2024
• 期刊: Physical Review D
• 影响因子: 5
• 作者: Copinger P