arXiv subjects

Yi Ling

Publications and source records attributed to Yi Ling.

115 records · Page 7Linked to original sources

arXiv2001

A thermal instability for positive brane cosmological constant in the Randall-Sundrum cosmologies

We describe a novel dynamical mechanism to radiate away a positive four dimensional cosmological constant, in the Randall-Sundrum cosmological scenario. We show that there are modes of the bulk gravitational field for which the brane is effectively a mirror. This will generally give rise to an emission of thermal radiation from the brane into the bulk. The temperature turns out to be nonvanishing only if the effective four dimensional cosmological constant is positive. In any theory where the four dimensional vacuum energy is a function of physical degrees of freedom, there is then a mechanism that radiates away any positive four dimensional cosmological constant.

hep-th↗

arXiv2000

$\hat{Q}$ operator for canonical quantum gravity

We study the properties of $\hat{Q}[ω]$ operator on the kinematical Hilbert space ${\cal H}$ for canonical quantum gravity. Its complete spectrum with respect to the spin network basis is obtained. It turns out that $\hat{Q}[ω]$ is diagonalized in this basis, and it is a well defined self-adjoint operator on ${\cal H}$. The same conclusions are also tenable on the SU(2) gauge invariant Hilbert space with the gauge invariant spin network basis.

gr-qc↗

arXiv2000

Classical Geometry from a Physical State in Canonical Quantum Gravity

We construct a weave state which approximates a degenerate 3-metric of rank 2 at large scales. It turns out that a non-degenerate metric region can be evolved from this degenerate metric by the classical Ashtekar equations, hence the degeneracy of 3-metrics is not preserved by the evolution of Ashtekar's equations. As the s-knot state corresponding to this weave is shown to solve all the quantum constraints in loop quantum gravity, a physical state in canonical quantum gravity is related to the familiar classical geometry.

gr-qc↗

arXiv2000

Eleven dimensional supergravity as a constrained topological field theory

We describe a new first-order formulation of D=11 supergravity which shows that that theory can be understood to arise from a certain topological field theory by the imposition of a set of local constraints on the fields, plus a lagrange multiplier term. The topological field theory is of interest as the algebra of its constraints realizes the D=11 supersymmetry algebra with central charges.

hep-th↗

arXiv2000

Introduction to supersymmetric spin networks

In this paper we give a general introduction to supersymmetric spin networks. Its construction has a direct interpretation in context of the representation theory of the superalgebra. In particular we analyze a special kind of spin networks with superalgebra $Osp(1|2n)$. It turns out that the set of corresponding spin network states forms an orthogonal basis of the Hilbert space $\cal L\mit^2(\cal A\mit/\cal G)$, and this argument holds even in the q-deformed case. The $Osp(n|2)$ spin networks are also discussed briefly. We expect they could provide useful techniques to quantum supergravity and gauge field theories from the point of non-perturbative view.

hep-th↗

arXiv2000

Holographic Formulation of Quantum Supergravity

We show that ${\cal N}=1$ supergravity with a cosmological constant can be expressed as constrained topological field theory based on the supergroup $Osp(1|4)$. The theory is then extended to include timelike boundaries with finite spatial area. Consistent boundary conditions are found which induce a boundary theory based on a supersymmetric Chern-Simons theory. The boundary state space is constructed from states of the boundary supersymmetric Chern-Simons theory on the punctured two sphere and naturally satisfies the Bekenstein bound, where area is measured by the area operator of quantum supergravity.

hep-th↗

arXiv1999

Supersymmetric Spin Networks and Quantum Supergravity

We define supersymmetric spin networks, which provide a complete set of gauge invariant states for supergravity and supersymmetric gauge theories. The particular case of Osp(1/2) is studied in detail and applied to the non-perturbative quantization of supergravity. The supersymmetric extension of the area operator is defined and partly diagonalized. The spectrum is discrete as in quantum general relativity, and the two cases could be distinguished by measurements of quantum geometry.

hep-th↗