The present thesis is concerned with the local quantum physics of relativistic particles and fields in three space-time dimensions, whose statistics is to be described by a representation of the braid group -- so-called plektons or, if the representation is Abelian, anyons. In particular the issue of the existence of free anyonic fields is addressed. In our context, these are operators affiliated with the `local´ field algebras and creating only single particle vectors from the vacuum. (Localizability here refers to regions extending to infinity in some spacelike direction.) Under a mild regularity condition for these fields, we can derive commutation relations which are not compatible with braid group statistics. Further, model-independent results concerning the PCT operator and the connection of spin and statistics are obtained. Assuming the observable algebra to satisfy the Bisognano-Wichmann theorem, a PCT theorem for plektons is derived. For anyons it is shown that the Bisognano-Wichmann property of the observable algebra lifts, in a `twisted´ version, to the field algebra. In particular, the PCT-operator coincides, up to a `twist operator´, with the modular conjugation of the field algebra associated to a standard wedge region. From this fact, the spin-statistics theorem for anyons is derived. The structure of the Hilbert space of scattering states of plektons and anyons is further clarified. It is known to be fixed by the relevant representations of the braid group and by the rules which determine the charges contained in the scattering states (the `fusion´ rules). We present Møller operators W+ and W- from the spaces of outgoing and incoming scattering states into a reference Hilbert space, which translate the physical ray representation of the Poincaré group on the spaces of scattering states into a canonical ray representation on the reference Hilbert space. A new result concerns the `incoming free PCT operator´, i.e. the product of the PCT operator with the S-matrix S = ( W+)* W- : It is exhibited how this model-independent operator acts in the reference Hilbert space. In the case of anyons, the fusion rules are trivial and the relevant representations of the braid group are classified by a finite set of complex numbers, namely the statistics parameters of the particles under consideration. Hence in the anyonic case the above results yield explicit formulae for the ray representation of the Poincaré group and for the incoming free PCT-operator. In view of the Bisognano-Wichmann property, we have thereby constructed the product of the Tomita operator associated to any given wedge region with the S-matrix, i.e. the `incoming free´ Tomita-operator of the anyonic field algebra.
It has been discussed earlier that ( weak quasi-) quantum groups allow for conventional interpretation as internal symmetries in local quantum theory. From general arguments and explicit examples their consistency with (braid-) statistics and locality was established. This work addresses to the reconstruction of quantum symmetries and algebras of field operators. For every algebra A of observables satisfying certain standard assumptions, an appropriate quantum symmetry is found. Field operators are obtained which act on a positive definite Hilbert space of states and transform covariantly under the quantum symmetry. As a substitute for Bose/Fermi (anti-) commutation relations, these fields are demonstrated to obey local braid relation. Contents 1 Introduction 1 2 The Notion of Quantum Symmetry 5 3 Algebraic Methods for Field Construction 9 3.1 Observables and superselection sectors in local quantum field theory . . . . 10 3.2 Localized endomorphisms and fusion structure . . . . . ....
Abstract In the previous sections we treated the irreducible representation space associated with the vacuum state. In this chapter we treat other representation spaces necessary to describe particle systems with the vacuum as a background. Such representation spaces are characterized as transportable localized excitations on the vacuum background. If we assume Haag’s duality of the vacuum representation, such a localized excitation is described by a localized endomorphism of the observables and its equivalence classes correspond to different representations called sectors(eigensubspaces of the superselection rules in each of which unrestricted superposition principle holds). From the discussion about composition and conjugation of localized endomorphisms, we define the statistics (of a sector) which represents the behaviour of more than two equivalent localized excitations under permutation, and we derive the connection of spin and statistics. We also introduce the lattice of local field algebras as operators intertwining different sectors, and the gauge group acting on them. Then the local observable algebras are the gauge invariant part of the local field algebras and sectors are inequivalent representations of the gauge group. The local field algebras can be chosen to satisfy the standard commutation or anticommutation relations between space-like separated regions and we can derive the connection of spin and statistics of sectors. In this way we obtain a deep understanding of the reason why Fermi fields in spatially separated regions anticommute.
String and particle braiding statistics are examined in a class of topological orders described by discrete gauge theories with a gauge group
G and a 4-cocycle twist ${\ensuremath{\omega}}_{4}$ of
G's cohomology group
H4(G,R/Z) in three-dimensional space and one-dimensional time
(3+1D). We establish the topological spin and the spin-statistics relation for the closed strings and their multistring braiding statistics. The
3+1D twisted gauge theory can be characterized by a representation of a modular transformation group,
SL(3,Z). We express the
SL(3,Z) generators
Sxyz and
Txy in terms of the gauge group
G and the 4-cocycle ${\ensuremath{\omega}}_{4}$. As we compactify one of the spatial directions
z into a compact circle with a gauge flux
b inserted, we can use the generators
Sxy and
Txy of an
SL(2,Z) subgroup to study the dimensional reduction of the 3D topological order
C3D to a direct sum of degenerate states of 2D topological orders
Cb2D in different flux
b sectors: ${\mathcal{C}}^{3\mathrm{D}}={\ensuremath{\bigoplus}}_{b}{\mathcal{C}}_{b}^{2\mathrm{D}}$. The 2D topological orders
Cb2D are described by 2D gauge theories of the group
G twisted by the 3-cocycle ${\ensuremath{\omega}}_{3(b)}$, dimensionally reduced from the 4-cocycle ${\ensuremath{\omega}}_{4}$. We show that the
SL(2,Z) generators,
Sxy and
Txy, fully encode a particular type of three-string braiding statistics with a pattern that is the connected sum of two Hopf links. With certain 4-cocycle twists, we discover that, by threading a third string through two-string unlink into a three-string Hopf-link configuration, Abelian two-string braiding statistics is promoted to non-Abelian three-string braiding statistics.
The article arXiv:2410.21454 constructed a braided
W∗-tensor category of superselection sectors associated to a net of von Neumann algebras on a suitably geometric poset using localized and transportable endomorphisms. In this article, we construct an equivalent tensor product and braiding using the Connes fusion tensor product without localizing, using ideas from arXiv:1812.04470 for conformal nets. As an application, we prove that the category of superselection sectors associated to the 2D braided quantum spin system constructed from a unitary braided fusion category
B in arXiv:2506.19969 is equivalent to
Hilb(B)op, the opposite of the unitary ind-completion of
B, as a braided
W∗-tensor category.
In this paper we study a class of theories of free particles on the complex plane satisfying a non-Abelian statistics. This kind of particles are generalizations of the anyons and are sometimes called plectons. The peculiarity of these theories is that they are associated to free conformal field theories defined on Riemann surfaces with a discrete and non-Abelian group of authomorphisms Dm. More explicitly, the plectons appear here as “induced vertex operators” that simulate, on the complex plane, the nontrivial topology of the Riemann surface. In order to express the local exchange algebra of the particles, one is led to introduce an R matrix satisfying a multiparameter generalization of the usual Yang-Baxter equations. It is interesting that analogous generalizations have already been investigated in connection with integrable models, in which the spectral parameter takes its values on a Riemann surface that is in many respects similar to the Riemann surfaces we are studying here. The explicit form of the R matrices mentioned above can be also used to define a multiparameter version of the quantum complex hyperplane.