The Landscape, the Swampland, and Information

阿尔伯特·爱因斯坦的“最大错误”至今仍困扰着理论物理学。爱因斯坦最初在他的引力方程中引入了一个“宇宙常数”，以模拟一个静态的宇宙，但当哈勃发现宇宙实际上是在膨胀时，他放弃了这个术语。然而，放弃宇宙常数被证明是错误的：1998年的仔细测量（导致2011年诺贝尔物理学奖）表明，宇宙的膨胀实际上正在加速，最简单的解释是一个非常小的宇宙常数。问题在于试图从理论物理中计算宇宙常数。朴素估计给出的答案比与测量相关联的值大1000亿亿亿古戈尔。弦理论提出了一种可能的解决方案，这是一种亚原子物理理论，也描述了引力：弦理论的状态似乎有一个巨大的“景观”，每个状态都有不同的宇宙常数。我们所处的宇宙可能只是处在一个宇宙常数非常小的状态。问题是，景观模型是基于四维物理的假设，而弦理论本身是十维的。一些物理学家推测，景观的四维理论实际上属于“沼泽地”，四维理论看起来合理，但实际上与弦理论不相容。作为世界公认的10D和4D物理之间联系的专家，我正在努力解决这个争论。答案将对我们理解宇宙的起源和命运产生深远的影响。与此同时，最近对量子引力和黑洞的研究提出了另一种方法；越来越多的证据表明，万有引力可以被理解为一种信息理论，即计算机中熟悉的比特。我正在从信息的角度构建宇宙常数的理论，将量子引力这一可能的基本原理与“景观vs沼泽”辩论的各个方面联系起来。我的工作是解决理论物理学中最大的问题，无论是在误差的大小还是在概念上的含义上，它都将加拿大置于该领域的前沿。

Albert Einstein's "biggest blunder" still haunts theoretical physics. Einstein originally introduced a "cosmological constant" term into his equations for gravity in order to model a static universe, but he dropped it when Hubble discovered that the universe is in fact expanding. Giving up on the cosmological constant turns out to be the mistake, though: careful measurements in 1998 (leading to the 2011 Nobel Prize in Physics) showed that the universe's expansion is in fact accelerating, and the simplest explanation is a very small cosmological constant. The problem lies in trying to calculate the cosmological constant from theoretical physics. The naive estimate gives an answer that is 100 billion billion googol larger than the value associated with measurements. One possible solution is suggested by string theory, a theory of subatomic physics that also describes gravity: there seems to be a gigantic "landscape" of states of string theory, each with a different cosmological constant. Our section of the universe may just lie in a state with a very small cosmological constant. The problem is that the landscape models are based on assumptions about four-dimensional physics, while string theory is itself ten-dimensional. Some physicists have conjectured that the 4D theories of the landscape actually belong to the "swampland," 4D theories that look reasonable but are actually incompatible with string theory. As a world-recognized expert on the connection between 10D and 4D physics, I am working to settle this debate. The answer will have profound implications for our understanding of the origins and fate of the universe. Meanwhile, recent insights into quantum gravity and black holes suggest another approach; there is increasing evidence that gravity can be understood as a theory of information, the bits familiar from computing. I am building theories of the cosmological constant in terms of information, connecting this possibly fundamental principle of quantum gravity to aspects of the "landscape vs swampland" debate. My work is solving the biggest problem in theoretical physics, both in terms of the size of the error and in the conceptual implications, and it is positioning Canada at the forefront of the field.