Is There Unification in the 21st Century?

The Spirit of Unification: The Wei of Physics

We review, in a historical perspective, developments in physics which led to the emergence of unifying ideas and theories. Some attention is paid to the theoretical programme that started in the second decade of the XXth century and whose objective was to reach a unified description of gravity and electromagnetism. These attempts can be regarded as conceptually akin to the contemporary "theories of everything" which aim to unify all interactions of Nature.

Exploring the unification of quantum theory and general relativity with a Bose-Einstein condensate

Despite almost a century's worth of study, it is still unclear how general relativity (GR) and quantum theory (QT) should be unified into a consistent theory. The conventional approach is to retain the foundational principles of QT, such as the superposition principle, and modify GR. This is referred to as `quantizing gravity', resulting in a theory of `quantum gravity'. The opposite approach is `gravitizing QT' where we attempt to keep the principles of GR, such as the equivalence principle, and consider how this leads to modifications of QT. What we are most lacking in understanding which ro…

源于膨胀非减速宇宙模型的弱相互作用与引力相互作用的统一

Unification of Weak and Gravitational Interactions Stemming from Expansive Nondecelerative Universe Model

广义相对论与膨胀非减速宇宙模型中的弱相互作用有着深刻的内在联系。这一事实允许独立确定矢量玻色子Z和W的质量，以及电磁相互作用和弱相互作用分离的时间。

Gravity and Unification: A review

We review various classical unified theories of gravity and other interactions that have appeared in the literature, paying special attention to scenarios in which spacetime remains four-dimensional, while an "internal" space is enlarged. The starting point for each such unification scenario is a particular formalism for General Relativity. We thus start by reviewing, besides the usual Einstein-Hilbert and Palatini formulations, the Einstein-Cartan, MacDowell-Mansouri and BF (both non-chiral and chiral) formulations. Each of these introduces some version of "internal" bundle and a dynamical va…

引力与电磁的度规统一解决了宇宙学常数问题

Metric Unification of Gravitation and Electromagnetism Solves the Cosmological Constant Problem

我们首先回顾了宇宙学常数问题，然后提到了费曼的一个猜想，根据这个猜想，广义相对论引力理论应该以这样一种方式重新表述，即能量不耦合到引力。我们指出，我们最近的统一引力和电磁通过一个对称张量的性质，自由电磁能和真空能量不显着贡献的时空曲率像自由引力能。因此，在广义相对论的这个公式中，真空能量密度在今天和早期宇宙一样具有非常大的值，而宇宙学常数则根本不存在。

High Energy Physics and Cosmology at the Unification Frontier: Opportunities and Challenges in the coming years

We give here an overview of recent developments in high energy physics and cosmology and their interconnections that relate to unification, and discuss prospects for the future. Thus there are currently three empirical data that point to supersymmetry as an underlying symmetry of particle physics: the unification of gauge couplings within supersymmetry, the fact that nature respects the supersymmetry prediction that the Higgs boson mass lie below 130 GeV, and vacuum stability up to the Planck scale with a Higgs boson mass at $\sim 125$ GeV while the standard model does not do that. Coupled wit…