Note on the structure constants for the diffeomorphisms of the two-sphere

On The BRST Formulation of Diffeomorphism Invariant 4D Quantum Gravity

In this note we give some remarks on the BRST formulation of a renormalizable and diffemorphism invariant 4D quantum gravity recently proposed by the author, which satisfies the integrability condition by Riegard, Fradkin and Tseytlin at the 2-loop level. Diffeomorphism invariance requires an addition of the Wess-Zumino action, from which the Weyl action can be induced by expanding around a vacuum expectation value of the conformal mode. This fact suggests the theory has in itself a mechanism to remove extra negative-metric states dynamically.

The Majorana representation of spins and the relation between $SU(\infty)$ and $SDiff(S^2)$

The Majorana representation of spin-$\frac{n}{2}$ quantum states by sets of points on a sphere allows a realization of SU(n) acting on such states, and thus a natural action on the two-dimensional sphere $S^2$. This action is discussed in the context of the proposed connection between $SU(\infty)$ and the group $SDiff(S^2)$ of area-preserving diffeomorphisms of the sphere. There is no need to work with a special basis of the Lie algebra of SU(n), and there is a clear geometrical interpretation of the connection between the two groups. It is argued that they are {\it not} isomorphic, and commen…

Gravity on a fuzzy sphere

We propose an action for gravity on a fuzzy sphere, based on a matrix model. We find striking similarities with an analogous model of two dimensional gravity on a noncommutative plane, i.e. the solution space of both models is spanned by pure U(2) gauge transformations acting on the background solution of the matrix model, and there exist deformations of the classical diffeomorphisms which preserve the two-dimensional noncommutative gravity actions.

Diffeomorphism on Horizon as an Asymptotic Isometry of Schwarzschild Black Hole

It is argued that the diffeomorphism on the horizontal sphere can be regarded as a nontrivial asymptotic isometry of the Schwarzschild black hole. We propose a new boundary condition of asymptotic metrics near the horizon and show that the condition admits the local time-shift and diffeomorphism on the horizon as the asymptotic symmetry.

A note on the M2-M5 brane system and fuzzy spheres

This note covers various aspects of recent attempts to describe membranes ending on fivebranes using fuzzy geometry. In particular, we examine the Basu-Harvey equation and its relation to the Nahm equation as well as the consequences of using a non-associative algebra for the fuzzy three-sphere. This produces the tantalising result that the fuzzy funnel solution corresponding to Q coincident membranes ending on a five-brane has $Q^{3/2}$ degrees of freedom.

Diffeomorphism Symmetry in Two Dimensions and Celestial Holography

Two-dimensional diffeomorphism symmetry can be described by an operator algebra extension of the well-known Virasoro algebra description of conformal symmetry. Utilizing this extension, this note explains why the conformal symmetry that appears in celestial holography should not be extended to diffeomorphism symmetry, a possibility that several authors have proposed. The description of the two-dimensional diffeomorphism algebra presented here might be useful for other purposes.

A note on the gauge symmetries of pure Chern-Simons theories with p-form gauge fields

The gauge symmetries of pure Chern-Simons theories with p-form gauge fields are analyzed. It is shown that the number of independent gauge symmetries depends crucially on the parity of p. The case where p is odd appears to be a direct generalization of the p=1 case and presents the remarkable feature that the timelike diffeomorphisms can be expressed in terms of the spatial diffeomorphisms and the internal gauge symmetries. By constrast, the timelike diffeomorphisms may be an independent gauge symmetry when p is even. This happens when the number of fields and the spacetime dimension fulfills …

关于主丛垂直微分同胚群及其与Frölicher-Nijenhuis括号关系的注记

Note on the group of vertical diffeomorphisms of a principal bundle, and its relation to the Frölicher-Nijenhuis bracket

本文指出主丛垂直微分同胚群对应的扩展规范参数括号可由Frölicher-Nijenhuis括号导出，将其纳入形式导子框架，并探讨了广义规范变换的独特性质。

A note on the fuzzy sphere area spectrum, black hole luminosity, and the quantum nature of spacetime

Non-commutative corrections to the classical expression for the fuzzy sphere area are found out through the asymptotic expansion for its heat kernel trace. As an important consequence, some quantum gravity deviations in the luminosity of black holes must appear. We calculate these deviations for a static, spherically symmetric, black-hole with a horizon modeled by a fuzzy sphere. The results obtained could be verified through the radiation of black holes formed in the Large Hadron Collider (LHC).

关于Berger球面上eta不变量的一个数值等式的注记

Note on a numerical equality regarding the eta invariant on Berger spheres

本文通过数值计算发现Berger球面上的Dirac APS eta不变量与圆球面上的Dirac共形反常一致，并用广义Bernoulli多项式验证了已知猜想，同时得到了Weingart生成函数。

关于模糊球面上共形生成元显式构造的注记

Note on explicit construction of conformal generators on the fuzzy sphere

本研究针对三维共形场论的模糊球正则化方案，提出借助微观哈密顿量显式构造平移与特殊共形变换生成元的方法，可精准识别自旋和标度维数满足特定条件的共形初级态。