754 research outputs found
ICT Diffusion and Economic Growth in New Zealand
Two different theoretical treatments of technology diffusion in an economy are examined. The traditional model based on the aggregate production function approach first introduced by Solow (1957) assumes technology is unstructured and arrives as a continuous exogenous flow. This model predicts that the diffusion of new technologies will be contemporaneously correlated with growth in economic performance indicators. An alternative view explicitly models technological structure in the form of complementarities. It also incorporates the observation that new general purpose technologies (GPTs) invariably emerge in a crude form lacking many of the complementarities that enable them to become productive. This view predicts that when new technologies emerge costly investment in developing complementary technologies must take place and thus there will be a lag between the new technologyâs introduction and observed growth in economic performance indicators. These two views articulate two general empirically testable hypotheses that are captured in a number of specific tests. One such test measures diffusion of information and communication technologies (ICT) as an independent phenomenon and compares its times series pattern to that of the growth of total factor productivity (TFP) in New Zealand. New Zealandâs experience in consistent with other OECD economies where the diffusion of ICT has occurred at the same time as a TFP slowdown. Another test measures relative ICT-skilled labour demand. Findings support the non-traditional viewâs prediction that ICT-skilled labour will increase with the diffusion of ICT technology in New Zealand.ICT, Productivity, Diffusion Technology
On Local Equivalence, Surface Code States and Matroids
Recently, Ji et al disproved the LU-LC conjecture and showed that the local
unitary and local Clifford equivalence classes of the stabilizer states are not
always the same. Despite the fact this settles the LU-LC conjecture, a
sufficient condition for stabilizer states that violate the LU-LC conjecture is
missing. In this paper, we investigate further the properties of stabilizer
states with respect to local equivalence. Our first result shows that there
exist infinitely many stabilizer states which violate the LU-LC conjecture. In
particular, we show that for all numbers of qubits , there exist
distance two stabilizer states which are counterexamples to the LU-LC
conjecture. We prove that for all odd , there exist stabilizer
states with distance greater than two which are LU equivalent but not LC
equivalent. Two important classes of stabilizer states that are of great
interest in quantum computation are the cluster states and stabilizer states of
the surface codes. To date, the status of these states with respect to the
LU-LC conjecture was not studied. We show that, under some minimal
restrictions, both these classes of states preclude any counterexamples. In
this context, we also show that the associated surface codes do not have any
encoded non-Clifford transversal gates. We characterize the CSS surface code
states in terms of a class of minor closed binary matroids. In addition to
making connection with an important open problem in binary matroid theory, this
characterization does in some cases provide an efficient test for CSS states
that are not counterexamples.Comment: LaTeX, 13 pages; Revised introduction, minor changes and corrections
mainly in section V
Feynman graph polynomials
The integrand of any multi-loop integral is characterised after Feynman
parametrisation by two polynomials. In this review we summarise the properties
of these polynomials. Topics covered in this article include among others:
Spanning trees and spanning forests, the all-minors matrix-tree theorem,
recursion relations due to contraction and deletion of edges, Dodgson's
identity and matroids.Comment: 35 pages, references adde
The Effects of Central Bank Digital Currency Communication and Associated Social Media Sentiment on Cryptocurrency Markets
The creation of central bank digital currency (CBDC) has been seen as a potential mechanism for addressing some of the negative consequences of increased cryptocurrency popularity. It has also been linked to the introduction or strengthening of regulations related to digital money, with some central banks identifying the need for a comprehensive regulatory framework as a precondition for successful CBDC implementation. However, this type of central bank intervention can be seen by market participants as a threat to both confidentiality and potential cryptocurrency profitability. Linking computationally analyzed social media data with hand-coded data from the websites of major central banks, we test the effects of CBDC-related announcements and social media sentiment. on 210 blockchain and cryptocurrency fund products. We find that for a large majority of theseproducts, central bank announcements elicit significant returns and volatility responses, with somevariation in response related to geographical region. Both central bank announcements and positivesocial media CBDC-related sentiment are associated with reduced cryptocurrency exchange tradedfund (ETF) returns and increased volatility. Our results provide evidence of a largely negativemarket response to the threat of potential cryptocurrency regulation that can be directly linked toCBDC developmen
Nonpolar resistance switching of metal/binary-transition-metal oxides/metal sandwiches: homogeneous/inhomogeneous transition of current distribution
Exotic features of a metal/oxide/metal (MOM) sandwich, which will be the
basis for a drastically innovative nonvolatile memory device, is brought to
light from a physical point of view. Here the insulator is one of the
ubiquitous and classic binary-transition-metal oxides (TMO), such as Fe2O3,
NiO, and CoO. The sandwich exhibits a resistance that reversibly switches
between two states: one is a highly resistive off-state and the other is a
conductive on-state. Several distinct features were universally observed in
these binary TMO sandwiches: namely, nonpolar switching, non-volatile threshold
switching, and current--voltage duality. From the systematic sample-size
dependence of the resistance in on- and off-states, we conclude that the
resistance switching is due to the homogeneous/inhomogeneous transition of the
current distribution at the interface.Comment: 7 pages, 5 figures, REVTeX4, submitted to Phys. Rev. B (Feb. 23,
2007). If you can't download a PDF file of this manscript, an alternative one
can be found on the author's website: http://staff.aist.go.jp/i.inoue
Self-avoiding walks crossing a square
We study a restricted class of self-avoiding walks (SAW) which start at the
origin (0, 0), end at , and are entirely contained in the square on the square lattice . The number of distinct
walks is known to grow as . We estimate as well as obtaining strict upper and lower bounds,
We give exact results for the number of SAW of
length for and asymptotic results for .
We also consider the model in which a weight or {\em fugacity} is
associated with each step of the walk. This gives rise to a canonical model of
a phase transition. For the average length of a SAW grows as ,
while for it grows as
. Here is the growth constant of unconstrained SAW in . For we provide numerical evidence, but no proof, that the
average walk length grows as .
We also consider Hamiltonian walks under the same restriction. They are known
to grow as on the same lattice. We give
precise estimates for as well as upper and lower bounds, and prove that
Comment: 27 pages, 9 figures. Paper updated and reorganised following
refereein
Measurement of the Electric and Magnetic Polarizabilities of the Proton
The Compton scattering cross section on the proton has been measured at
laboratory angles of 90 and 135 using tagged photons in the
energy range 70--100 MeV and simultaneously using untagged photons in the range
100--148~MeV. With the aid of dispersion relations, these cross sections were
used to extract the electric and magnetic polarizabilities, and
respectively, of the proton. We find
in agreement with a model-independent dispersion sum rule, and
where the errors shown are statistical, systematic, and model-dependent,
respectively. A comparison with previous experiments is given and global values
for the polarizabilities are extracted.Comment: 35 pages, 11 PostScript figures, uses RevTex 3.
Molecular dynamics simulations of oxide memory resistors (memristors)
Reversible bipolar nano-switches that can be set and read electronically in a
solid-state two-terminal device are very promising for applications. We have
performed molecular-dynamics simulations that mimic systems with oxygen
vacancies interacting via realistic potentials and driven by an external bias
voltage. The competing short- and long-range interactions among charged mobile
vacancies lead to density fluctuations and short-range ordering, while
illustrating some aspects of observed experimental behavior, such as memristor
polarity inversion.Comment: 15 pages, 5 figure
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