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Search Results: 1 - 10 of 7517 matches for " Yidun Wan "
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On Braid Excitations in Quantum Gravity
Yidun Wan
Physics , 2007,
Abstract: We propose a new notation for the states in some models of quantum gravity, namely 4-valent spin networks embedded in a topological three manifold. With the help of this notation, equivalence moves, namely translations and rotations, can be defined, which relate the projections of diffeomorphic embeddings of a spin network. Certain types of topological structures, viz 3-strand braids as local excitations of embedded spin networks, are defined and classified by means of the equivalence moves. This paper formulates a mathematical approach to the further research of particle-like excitations in quantum gravity.
2D Ising Model with non-local links - a study of non-locality
Yidun Wan
Physics , 2005,
Abstract: Markopoulou and Smolin have argued that the low energy limit of LQG may suffer from a conflict between locality, as defined by the connectivity of spin networks, and an averaged notion of locality that emerges at low energy from a superposition of spin network states. This raises the issue of how much non-locality, relative to the coarse grained metric, can be tolerated in the spin network graphs that contribute to the ground state. To address this question we have been studying statistical mechanical systems on lattices decorated randomly with non-local links. These turn out to be related to a class of recently studied systems called small world networks. We show, in the case of the 2D Ising model, that one major effect of non-local links is to raise the Curie temperature. We report also on measurements of the spin-spin correlation functions in this model and show, for the first time, the impact of not only the amount of non-local links but also of their configuration on correlation functions.
Effective Theory of Braid Excitations of Quantum Geometry in terms of Feynman Diagrams
Yidun Wan
Physics , 2008, DOI: 10.1016/j.nuclphysb.2008.10.025
Abstract: We study interactions amongst topologically conserved excitations of quantum theories of gravity, in particular the braid excitations of four-valent spin networks. These have been shown previously to propagate and interact under evolution rules of spin foam models. We show that the dynamics of these braid excitations can be described by an effective theory based on Feynman diagrams. In this language, braids which are actively interacting are analogous to bosons, in that the topological conservation laws permit them to be singly created and destroyed. Exchanges of these excitations give rise to interactions between braids which are charged under the topological conservation rules.
C, P, and T of Braid Excitations in Quantum Gravity
Song He,Yidun Wan
Physics , 2008, DOI: 10.1016/j.nuclphysb.2008.06.022
Abstract: We study the discrete transformations of four-valent braid excitations of framed spin networks embedded in a topological three-manifold. We show that four-valent braids allow seven and only seven discrete transformations. These transformations can be uniquely mapped to C, P, T, and their products. Each CPT multiplet of actively-interacting braids is found to be uniquely characterized by a non-negative integer. Finally, braid interactions turn out to be invariant under C, P, and T.
Conserved Quantities and the Algebra of Braid Excitations in Quantum Gravity
Song He,Yidun Wan
Physics , 2008, DOI: 10.1016/j.nuclphysb.2008.06.021
Abstract: We derive conservation laws from interactions of braid-like excitations of embedded framed spin networks in Quantum Gravity. We also demonstrate that the set of stable braid-like excitations form a noncommutative algebra under braid interaction, in which the set of actively-interacting braids is a subalgebra.
Propagation and interaction of chiral states in quantum gravity
Lee Smolin,Yidun Wan
Physics , 2007, DOI: 10.1016/j.nuclphysb.2007.12.018
Abstract: We study the stability, propagation and interactions of braid states in models of quantum gravity in which the states are four-valent spin networks embedded in a topological three manifold and the evolution moves are given by the dual Pachner moves. There are results for both the framed and unframed case. We study simple braids made up of two nodes which share three edges, which are possibly braided and twisted. We find three classes of such braids, those which both interact and propagate, those that only propagate, and the majority that do neither.
Conserved Quantities for Interacting Four Valent Braids in Quantum Gravity
Jonahan Hackett,Yidun Wan
Physics , 2008, DOI: 10.1088/0264-9381/26/12/125008
Abstract: We derive conservation laws from interactions of actively-interacting braid-like excitations of embedded framed spin networks in Quantum Gravity. Additionally we demonstrate that actively-interacting braid-like excitations interact in such a way that the product of interactions involving two actively-interacting braid-like excitations produces a resulting actively-interacting form.
Infinite Degeneracy of States in Quantum Gravity
Jonathan Hackett,Yidun Wan
Physics , 2008, DOI: 10.1088/1742-6596/306/1/012053
Abstract: The setting of Braided Ribbon Networks is used to present a general result in spin-networks embedded in manifolds: the existence of an infinite number of species of conserved quantities. Restricted to three-valent networks the number of such conserved quantities in a given network is shown to be invariant barring a single case. The implication of these conserved quantities is discussed in the context of Loop Quantum Gravity.
A K matrix Construction of Symmetry Enriched Phases of Matter
Ling-Yan Hung,Yidun Wan
Physics , 2013, DOI: 10.1103/PhysRevB.87.195103
Abstract: We construct in the K matrix formalism concrete examples of symmetry enriched topological phases, namely intrinsically topological phases with global symmetries. We focus on the Abelian and non-chiral topological phases and demonstrate by our examples how the interplay between the global symmetry and the fusion algebra of the anyons of a topologically ordered system determines the existence of gapless edge modes protected by the symmetry and that a (quasi)-group structure can be defined among these phases. Our examples include phases that display charge fractionalization and more exotic non-local anyon exchange under global symmetry that correspond to general group extensions of the global symmetry group.
Revisiting Entanglement Entropy of Lattice Gauge Theories
Ling-Yan Hung,Yidun Wan
Physics , 2015, DOI: 10.1007/JHEP04(2015)122
Abstract: Casini et al raise the issue that the entanglement entropy in gauge theories is ambiguous because its definition depends on the choice of the boundary between two regions.; even a small change in the boundary could annihilate the otherwise finite topological entanglement entropy between two regions. In this article, we first show that the topological entanglement entropy in the Kitaev model which is not a true gauge theory, is free of ambiguity. Then, we give a physical interpretation, from the perspectives of what can be measured in an experiement, to the purported ambiguity of true gauge theories, where the topological entanglement arises as redundancy in counting the degrees of freedom along the boundary separating two regions. We generalize these discussions to non-Abelian gauge theories.
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