3,900 research outputs found
Exact and Scaling Form of the Bipartite Fidelity of the Infinite XXZ Chain
We find an exact expression for the bipartite fidelity f=|'|^2,
where |vac> is the vacuum eigenstate of an infinite-size antiferromagnetic XXZ
chain and |vac>' is the vacuum eigenstate of an infinite-size XXZ chain which
is split in two. We consider the quantity -ln(f) which has been put forward as
a measure of quantum entanglement, and show that the large correlation length
xi behaviour is consistent with a general conjecture -ln(f) ~ c/8 ln(xi), where
c is the central charge of the UV conformal field theory (with c=1 for the XXZ
chain). This behaviour is a natural extension of the existing conformal field
theory prediction of -ln(f) ~ c/8 ln(L) for a length L bipartite system with
0<< L <<xi.Comment: 6 page
Bi-partite entanglement entropy in integrable models with backscattering
In this paper we generalise the main result of a recent work by J. L. Cardy
and the present authors concerning the bi-partite entanglement entropy between
a connected region and its complement. There the expression of the leading
order correction to saturation in the large distance regime was obtained for
integrable quantum field theories possessing diagonal scattering matrices. It
was observed to depend only on the mass spectrum of the model and not on the
specific structure of the diagonal scattering matrix. Here we extend that
result to integrable models with backscattering (i.e. with non-diagonal
scattering matrices). We use again the replica method, which connects the
entanglement entropy to partition functions on Riemann surfaces with two branch
points. Our main conclusion is that the mentioned infrared correction takes
exactly the same form for theories with and without backscattering. In order to
give further support to this result, we provide a detailed analysis in the
sine-Gordon model in the coupling regime in which no bound states (breathers)
occur. As a consequence, we obtain the leading correction to the sine-Gordon
partition function on a Riemann surface in the large distance regime.
Observations are made concerning the limit of large number of sheets.Comment: 22 pages, 2 figure
Alkali-Alumina Sorbents for Regenerable SO_2 Removal in Fluidized-Coal Combustion
Sodium and sodium-lithium oxides supported on porous alumina have been investigated as regenerable SO_2 sorbents for fluidized coal combustion. In adsorption the oxides are converted to sulfates. In regeneration, carried out by reduction with CO, the sulfates are converted back to oxides while sulfur is removed in elemental form (S_2), SO_2 and COS. The transient composition of sorbent and gaseous products was measured in a thermogravimetric analyzer and a packed-bed microreactor in order to delineate the basic chemistry of regeneration and determine conditions that maximize the yield of elemental sulfur
Mapping quantum Hall edge states in graphene by scanning tunneling microscopy
Quantum Hall edge states are the paradigmatic example of the bulk-boundary
correspondence. They are prone to intricate reconstructions calling for their
detailed investigation at high spatial resolution. Here, we map quantum Hall
edge states of monolayer graphene at a magnetic field of 7 T with scanning
tunneling microscopy. The graphene sample features a gate-tunable lateral
interface between areas of different filling factor. We compare the results
with detailed tight-binding calculations quantitatively accounting for the
perturbation by the tip-induced quantum dot. We find that the edge state
pattern is mapped with little perturbation by adequate choice of gate voltage.
We observe extended compressible regions, the antinodal structure of edge
states and their meandering along the lateral interface.Comment: 23 pages, 23 figure
Derivation of Matrix Product Ansatz for the Heisenberg Chain from Algebraic Bethe Ansatz
We derive a matrix product representation of the Bethe ansatz state for the
XXX and XXZ spin-1/2 Heisenberg chains using the algebraic Bethe ansatz. In
this representation, the components of the Bethe eigenstates are expressed as
traces of products of matrices which act on , the tensor
product of auxiliary spaces. By changing the basis in , we
derive explicit finite-dimensional representations for the matrices. These
matrices are the same as those appearing in the recently proposed matrix
product ansatz by Alcaraz and Lazo [Alcaraz F C and Lazo M J 2006 {\it J. Phys.
A: Math. Gen.} \textbf{39} 11335.] apart from normalization factors. We also
discuss the close relation between the matrix product representation of the
Bethe eigenstates and the six-vertex model with domain wall boundary conditions
[Korepin V E 1982 {\it Commun. Math. Phys.}, \textbf{86} 391.] and show that
the change of basis corresponds to a mapping from the six-vertex model to the
five-vertex model.Comment: 24 pages; minor typos are correcte
Hyperuniversality of Fully Anisotropic Three-Dimensional Ising Model
For the fully anisotropic simple-cubic Ising lattice, the critical
finite-size scaling amplitudes of both the spin-spin and energy-energy inverse
correlation lengths and the singular part of the reduced free-energy density
are calculated by the transfer-matrix method and a finite-size scaling for
cyclic L x L x oo clusters with L=3 and 4. Analysis of the data obtained shows
that the ratios and the directional geometric means of above amplitudes are
universal.Comment: RevTeX 3.0, 24 pages, 2 figures upon request, accepted for
publication in Phys. Rev.
Impact mitigation in environmental impact assessment: paper promises or the basis of consent conditions?
Large-scale Nonlinear Variable Selection via Kernel Random Features
We propose a new method for input variable selection in nonlinear regression.
The method is embedded into a kernel regression machine that can model general
nonlinear functions, not being a priori limited to additive models. This is the
first kernel-based variable selection method applicable to large datasets. It
sidesteps the typical poor scaling properties of kernel methods by mapping the
inputs into a relatively low-dimensional space of random features. The
algorithm discovers the variables relevant for the regression task together
with learning the prediction model through learning the appropriate nonlinear
random feature maps. We demonstrate the outstanding performance of our method
on a set of large-scale synthetic and real datasets.Comment: Final version for proceedings of ECML/PKDD 201
Decomposition of automotive manufacturing machines through a mechanism taxonomy within a product lifecycle management framework
The automotive sector as with other manufacturing industries is under continual pressure from the consumer to deliver greater levels of product customisation at a higher quality and at reduced costs. Maintaining market position is therefore increasingly determined by a company's ability to innovate design changes quickly and produce greater numbers of product
variants on leaner production lines with shorter times to market. In response manufacturers are attempting to accommodate product customisation and change through the use of reconfigurable production machines. Besides the need for flexibility, production facilities represent a significant investment for automotive manufacturers which is increasingly critical to commercial success; consequently the need to reduce costs through the reuse of assembly and manufacturing hardware on new product programs is becoming crucial. The aim of this research is to enable production machines to be more easily and cost effectively built and subsequently reconfigurable through the adoption of a component-based approach to their implementation utilising virtual manufacturing tools such as Product Lifecycle Management (PLM). It is suggested that through the decomposition of manufacturing machines into standardised mechanisms and their associated data structures a revised business model can be
defined. The mechanisms are classified and deployed as part of a consistent integrated data structure that encompasses product, process and plant information. An objective is to properly integrate manufacturing data with more established Product Data Management (PDM) processes. The main areas of research reported in this article are, (1) development of a method for identifying and mapping data producers, consumers and flow, (2) development of standardised data structures for the management of manufacturing data within a PLM tool, (3) development of a taxonomy for the decomposition of manufacturing and assembly lines into a library of standard physical, logical and structural mechanisms and their associated interfaces. An automotive OEM case study is presented to illustrate the classification and management of production mechanisms focusing on an engine assembly line
The Primordial Inflation Polarization Explorer (PIPER)
The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne
cosmic microwave background (CMB) polarimeter designed to search for evidence
of inflation by measuring the large-angular scale CMB polarization signal.
BICEP2 recently reported a detection of B-mode power corresponding to the
tensor-to-scalar ratio r = 0.2 on ~2 degree scales. If the BICEP2 signal is
caused by inflationary gravitational waves (IGWs), then there should be a
corresponding increase in B-mode power on angular scales larger than 18
degrees. PIPER is currently the only suborbital instrument capable of fully
testing and extending the BICEP2 results by measuring the B-mode power spectrum
on angular scales = ~0.6 deg to 90 deg, covering both the reionization
bump and recombination peak, with sensitivity to measure the tensor-to-scalar
ratio down to r = 0.007, and four frequency bands to distinguish foregrounds.
PIPER will accomplish this by mapping 85% of the sky in four frequency bands
(200, 270, 350, 600 GHz) over a series of 8 conventional balloon flights from
the northern and southern hemispheres. The instrument has background-limited
sensitivity provided by fully cryogenic (1.5 K) optics focusing the sky signal
onto four 32x40-pixel arrays of time-domain multiplexed Transition-Edge Sensor
(TES) bolometers held at 140 mK. Polarization sensitivity and systematic
control are provided by front-end Variable-delay Polarization Modulators
(VPMs), which rapidly modulate only the polarized sky signal at 3 Hz and allow
PIPER to instantaneously measure the full Stokes vector (I, Q, U, V) for each
pointing. We describe the PIPER instrument and progress towards its first
flight.Comment: 11 pages, 7 figures. To be published in Proceedings of SPIE Volume
9153. Presented at SPIE Astronomical Telescopes + Instrumentation 2014,
conference 915
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