Holographic quantum fluids

量子流体是一种非传统类型的流体(气体或液体)，具有奇异的性质，只能用量子力学来解释。例如，量子流体有一种叫做超流体成分的无粘组分，在非常低的温度范围内(在绝对零度附近)，它的百分比趋于100%；这种性质使非常冷的量子流体几乎永远随着粘性而运动，导致水或蜂蜜等经典流体在时间上变慢，趋于零。超流体成分的另一个显著特性是能够容纳涡旋(流体旋转的区域)，这些涡旋只有离散的循环值，换句话说，它们的强度是量化的。尽管大约100年前在极低温度下冷却液氦时被发现，但今天所知的大多数量子流体直到最近20年才在实验中实现。它们的技术用途仍然非常有限，但前景看好，因为人们相信，在未来几十年里，它们可能会越来越多地被用于制造令人难以置信的精确传感器，在量子计算中，以及作为非常有效的热传输介质。然而，为了实现这些目标，更好地了解它们的性质是至关重要的。这一提议旨在更好地理解具有强相互作用特征的量子流体，例如冷液氦。由于它们的强相互作用，标准的理论方法，如微扰方法，不能为这类系统提供模型。我们建议使用过去二十年在高能粒子物理和弦理论领域发展起来的称为全息对偶/全息理论的理论框架来解决建模问题。简而言之，全息术可以通过将强相互作用系统映射到弯曲时空中更高维度的弱相互作用系统来找到强相互作用系统的模型描述。这种方法当然增加了问题的复杂性，但允许在弱相互作用的对应物中应用标准的微扰方法。更准确地说，可以尝试理论和数值方法，因此可以有效地对强相互作用系统进行建模。全息对偶性已经应用于凝聚态物质和粒子物理中的各种物理系统，包括量子流体。然而，直到最近几年，由于新的数值方法的发展和计算能力的提高，量子流体的动力学模拟才成为可能。拟议的研究将极大地扩展这些工作，并允许对与实验设置更相关的系统进行建模，并有望发现新的物理学！

A quantum fluid is an unconventional type of fluid (gas or liquid) with exotic properties that can only be explained invoking quantum mechanics. For example, a quantum fluid possesses an inviscid component called superfluid component, whose percentage tends to 100% in the limit of very small temperatures (around the absolute zero); such property makes a very cold quantum fluid moving almost forever as viscosity, causing a classical fluid like water or honey to slow down in time, tends to zero. Another striking property of the superfluid component is the ability to host vortices (regions where the fluid rotates) that have only discrete values of circulation, in other words meaning that their strength is quantised.Despite being discovered about a hundred years ago when cooling down liquid helium at very low temperatures, most of the quantum fluids known today have only been experimentally realised in the last two decades. Their technological uses are still very limited but promising, as it is believed that in the next decades they could be used more and more to make incredibly precise sensors, in quantum computing, and as very efficient media to transport heat. However, in order to achieve these goals, a better understanding of their properties is of paramount importance.This proposal aims at better understanding quantum fluids characterised by strong interactions like for example, cold liquid helium. Due to their strong interactions, standard theoretical methods like perturbative methods fail to provide models for such systems. We propose to tackle the modelling by using a theoretical framework developed in the past two decades in the field of high energy particle physics and string theory called holographic duality / holography theory. In a nutshell, holography allows to find a model description of strong interacting systems by mapping them into weakly interacting systems at higher dimensions in curved space-time. This method certainly increases the complexity of the problem but allows to apply standard perturbative methods within the weakly interacting counterparts. More precisely, theoretical and numerical approaches can be attempted, therefore allowing to effectively model strongly interacting systems.The holographic duality has been applied to a great variety of physical systems in condensed matter and particle physics, including quantum fluids before. However, only in the last couple of years, dynamical modelling of quantum fluids have been feasible thanks to the development of novel numerical methods and the improvement of computational power. The proposed research will greatly extend these works and allow to model systems which are more relevant to experimental setups and discover, hopefully, new physics!