431 research outputs found
On boundary RG-flows in coset conformal field theories
We propose a new rule for boundary renormalization group flows in fixed-point
free coset models. Our proposal generalizes the 'absorption of boundary
spin'-principle formulated by Affleck and Ludwig to a large class of
perturbations in boundary conformal field theories. We illustrate the rule in
the case of unitary minimal models.Comment: 3 pages, uses RevTeX
Brane dynamics in CFT backgrounds
In this note we discuss bound states of un- or meta-stable brane configurations in various non-trivial (curved) backgrounds. We begin by reviewing some known results concerning brane dynamics on group manifolds. These are then employed to study condensation in cosets of the WZW model. While the basic ideas are more general, our presentation focuses on parafermion theories and, closely related, superconformal minimal models. We determine the (non-commutative) low energy effective actions for all maximally symmetric branes in a decoupling limit of the two theories. These actions are used to show that the lightest branes can be regarded as elementary constituents for all other maximally symmetric branes
Scattering States of Plektons (PARTICLES with Braid Group Statistics) in 2+1 Dimensional Quantum Field Theory
A Haag-Ruelle scattering theory for particles with braid group statistics is
developed, and the arising structure of the Hilbert space of multiparticle
states is analyzed.Comment: 18 pages, LATEX, DAMTP-94-9
Ultraviolet Finite Quantum Field Theory on Quantum Spacetime
We discuss a formulation of quantum field theory on quantum space time where
the perturbation expansion of the S-matrix is term by term ultraviolet finite.
The characteristic feature of our approach is a quantum version of the Wick
product at coinciding points: the differences of coordinates q_j - q_k are not
set equal to zero, which would violate the commutation relation between their
components. We show that the optimal degree of approximate coincidence can be
defined by the evaluation of a conditional expectation which replaces each
function of q_j - q_k by its expectation value in optimally localized states,
while leaving the mean coordinates (q_1 + ... + q_n)/n invariant.
The resulting procedure is to a large extent unique, and is invariant under
translations and rotations, but violates Lorentz invariance. Indeed, optimal
localization refers to a specific Lorentz frame, where the electric and
magnetic parts of the commutator of the coordinates have to coincide *).
Employing an adiabatic switching, we show that the S-matrix is term by term
finite. The matrix elements of the transfer matrix are determined, at each
order in the perturbative expansion, by kernels with Gaussian decay in the
Planck scale. The adiabatic limit and the large scale limit of this theory will
be studied elsewhere.
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*) S. Doplicher, K. Fredenhagen, and J.E.Roberts, Commun. Math. Phys. 172,
187 (1995) [arXiv:hep-th/0303037]Comment: LaTeX (using amsmath, amssymb), 23 pages, 1 figure. Dedicated to
Rudolf Haag on the occasion of his 80th birthday. See also: hep-th/0303037,
hep-th/0201222. Second version: minor changes in exposition, two references
added. To appear on Commun. Math. Phy
D-branes in the diagonal SU(2) coset
The symmetry preserving D-branes in coset theories have previously been
described as being centered around projections of products of conjugacy classes
in the underlying Lie groups. Here, we investigate the coset where a diagonal
action of SU(2) is divided out from SU(2)\times SU(2). The corresponding target
space is described as a (3-dimensional) pillow with four distinguished corners.
It is shown that the (fractional) brane which corresponds to the fixed point
that arises in the CFT description, is spacefilling. Moreover, the spacefilling
brane is the only one that reaches all of the corners. The other branes are 3,
1 and 0 - dimensional.Comment: v2: reference added, 9 page
DBI analysis of generalised permutation branes
We investigate D-branes on the product GxG of two group manifolds described
as Wess-Zumino-Novikov-Witten models. When the levels of the two groups
coincide, it is well known that there exist permutation D-branes which are
twisted by the automorphism exchanging the two factors. When the levels are
different, the D-brane charge group demands that there should be
generalisations of these permutation D-branes, and a geometric construction for
them was proposed in hep-th/0509153. We give further evidence for this proposal
by showing that the generalised permutation D-branes satisfy the
Dirac-Born-Infeld equations of motion for arbitrary compact, simply connected
and simple Lie groups G.Comment: 19 pages, computation in section 3.5.1 corrected, conclusions
unchange
Field Theory on Noncommutative Spacetimes: Quasiplanar Wick Products
We give a definition of admissible counterterms appropriate for massive
quantum field theories on the noncommutative Minkowski space, based on a
suitable notion of locality. We then define products of fields of arbitrary
order, the so-called quasiplanar Wick products, by subtracting only such
admissible counterterms. We derive the analogue of Wick's theorem and comment
on the consequences of using quasiplanar Wick products in the perturbative
expansion.Comment: 22 pages, 2 figures, v2: minor changes, v3: minor changes, reference
adde
The Spin-Statistics Theorem for Anyons and Plektons in d=2+1
We prove the spin-statistics theorem for massive particles obeying braid
group statistics in three-dimensional Minkowski space. We start from first
principles of local relativistic quantum theory. The only assumption is a gap
in the mass spectrum of the corresponding charged sector, and a restriction on
the degeneracy of the corresponding mass.Comment: 21 pages, 2 figures. Citation added; Minor modifications of Appendix
Symmetries of perturbed conformal field theories
The symmetries of perturbed conformal field theories are analysed. We explain
which generators of the chiral algebras of a bulk theory survive a perturbation
by an exactly marginal bulk field. We also study the behaviour of D-branes
under current-current bulk deformations. We find that the branes always
continue to preserve as much symmetry as they possibly can, i.e. as much as is
preserved in the bulk. We illustrate these findings with several examples,
including permutation branes in WZW models and B-type D-branes in Gepner
models.Comment: 30 pages, 3 figures. V2: Small error in eq. (2.14) correcte
D-branes and matrix factorisations in supersymmetric coset models
Matrix factorisations describe B-type boundary conditions in N=2
supersymmetric Landau-Ginzburg models. At the infrared fixed point, they
correspond to superconformal boundary states. We investigate the relation
between boundary states and matrix factorisations in the Grassmannian
Kazama-Suzuki coset models. For the first non-minimal series, i.e. for the
models of type SU(3)_k/U(2), we identify matrix factorisations for a subset of
the maximally symmetric boundary states. This set provides a basis for the RR
charge lattice, and can be used to generate (presumably all) other boundary
states by tachyon condensation.Comment: 63 pages, 2 figure
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