16,151 research outputs found
Non-Abelian quantized Hall states of electrons at filling factors 12/5 and 13/5 in the first excited Landau level
We present results of extensive numerical calculations on the ground state of
electrons in the first excited (n=1) Landau level with Coulomb interactions,
and including non-zero thickness effects, for filling factors 12/5 and 13/5 in
the torus geometry. In a region that includes these experimentally-relevant
values, we find that the energy spectrum and the overlaps with the trial states
support the previous hypothesis that the system is in the non-Abelian k = 3
liquid phase we introduced in a previous paper.Comment: 5 pages (Revtex4), 7 figure
The periodic sl(2|1) alternating spin chain and its continuum limit as a bulk Logarithmic Conformal Field Theory at c=0
The periodic sl(2|1) alternating spin chain encodes (some of) the properties
of hulls of percolation clusters, and is described in the continuum limit by a
logarithmic conformal field theory (LCFT) at central charge c=0. This theory
corresponds to the strong coupling regime of a sigma model on the complex
projective superspace , and the spectrum of critical exponents can be
obtained exactly. In this paper we push the analysis further, and determine the
main representation theoretic (logarithmic) features of this continuum limit by
extending to the periodic case the approach of [N. Read and H. Saleur, Nucl.
Phys. B 777 316 (2007)]. We first focus on determining the representation
theory of the finite size spin chain with respect to the algebra of local
energy densities provided by a representation of the affine Temperley-Lieb
algebra at fugacity one. We then analyze how these algebraic properties carry
over to the continuum limit to deduce the structure of the space of states as a
representation over the product of left and right Virasoro algebras. Our main
result is the full structure of the vacuum module of the theory, which exhibits
Jordan cells of arbitrary rank for the Hamiltonian.Comment: 69pp, 8 fig
New multi-channel electron energy analyzer with cylindrically symmetrical electrostatic field
This paper discusses an electron energy analyzer with a cylindrically
symmetrical electrostatic field, designed for rapid Auger analysis. The device
was designed and built. The best parameters of the analyzer were estimated and
then experimentally verified.Comment: 5 pages, 4 figure
Dense loops, supersymmetry, and Goldstone phases in two dimensions
Loop models in two dimensions can be related to O(N) models. The
low-temperature dense-loops phase of such a model, or of its reformulation
using a supergroup as symmetry, can have a Goldstone broken-symmetry phase for
N<2. We argue that this phase is generic for -2< N <2 when crossings of loops
are allowed, and distinct from the model of non-crossing dense loops first
studied by Nienhuis [Phys. Rev. Lett. 49, 1062 (1982)]. Our arguments are
supported by our numerical results, and by a lattice model solved exactly by
Martins et al. [Phys. Rev. Lett. 81, 504 (1998)].Comment: RevTeX, 5 pages, 3 postscript figure
Spin-Peierls states of quantum antiferromagnets on the lattice
We discuss the quantum paramagnetic phases of Heisenberg antiferromagnets on
the 1/5-depleted square lattice found in . The possible phases of
the quantum dimer model on this lattice are obtained by a mapping to a
quantum-mechanical height model. In addition to the ``decoupled'' phases found
earlier, we find a possible intermediate spin-Peierls phase with
spontaneously-broken lattice symmetry. Experimental signatures of the different
quantum paramagnetic phases are discussed.Comment: 9 pages; 2 eps figure
Universal low-temperature properties of quantum and classical ferromagnetic chains
We identify the critical theory controlling the universal, low temperature,
macroscopic properties of both quantum and classical ferromagnetic chains. The
theory is the quantum mechanics of a single rotor. The mapping leads to an
efficient method for computing scaling functions to high accuracy.Comment: 4 pages, 2 tables and 3 Postscript figure
Entanglement creation and distribution on a graph of exchange-coupled qutrits
We propose a protocol that allows both the creation and distribution of
entanglement, resulting in two distant parties (Alice and Bob) conclusively
sharing a bipartite Bell State. The system considered is a graph of three-level
objects ("qutrits") coupled by SU(3) exchange operators. The protocol begins
with a third party (Charlie) encoding two lattice sites in unentangled states,
and allowing unitary evolution under time. Alice and Bob perform a projective
measurement on their respective qutrits at a given time, and obtain a
maximally-entangled Bell state with a certain probablility. We also consider
two further protocols, one based on simple repetition and the other based on
successive measurements and conditional resetting, and show that the cumulative
probability of creating a Bell state between Alice and Bob tends to unity.Comment: Added seven references, clarified argument for eqn (16
Can grey ravens fly? Beyond Frayling's categories
This paper analyses the effect of Christopher Frayling's (1993) categorisation of artistic research ‘research into art and design, research through art and design and research for art and design’ on the debate surrounding the efficacy of studio-based artistic research as being valid within the university. James Elkins (2009:128) describes this as ‘the incommensurability of studio art production and university life’. Through an exploration of the positive and negative responses to Frayling this paper seeks to explore the influence that these initial definitions have come to have on framing the scope of the debate. The paper presents a range of responses and analyses them and focuses especially on the alternative frameworks that have been suggested and examines why they have so far not created a coherent and uncontested frame-work for practice-led research in the art and design field especially in relation to fine art
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