42,823 research outputs found
A non-hyponormal operator generating Stieltjes moment sequences
A linear operator in a complex Hilbert space \hh for which the set
\dzn{S} of its -vectors is dense in \hh and is a Stieltjes moment sequence for every f \in \dzn{S}
is said to generate Stieltjes moment sequences. It is shown that there exists a
closed non-hyponormal operator which generates Stieltjes moment sequences.
What is more, \dzn{S} is a core of any power of . This is
established with the help of a weighted shift on a directed tree with one
branching vertex. The main tool in the construction comes from the theory of
indeterminate Stieltjes moment sequences. As a consequence, it is shown that
there exists a non-hyponormal composition operator in an -space (over a
-finite measure space) which is injective, paranormal and which
generates Stieltjes moment sequences. In contrast to the case of abstract
Hilbert space operators, composition operators which are formally normal and
which generate Stieltjes moment sequences are always subnormal (in fact
normal). The independence assertion of Barry Simon's theorem which
parameterizes von Neumann extensions of a closed real symmetric operator with
deficiency indices is shown to be false
Track clustering with a quantum annealer for primary vertex reconstruction at hadron colliders
Clustering of charged particle tracks along the beam axis is the first step
in reconstructing the positions of hadronic interactions, also known as primary
vertices, at hadron collider experiments. We use a 2036 qubit D-Wave quantum
annealer to perform track clustering in a limited capacity on artificial events
where the positions of primary vertices and tracks resemble those measured by
the Compact Muon Solenoid experiment at the Large Hadron Collider. The
algorithm, which is not a classical-quantum hybrid but relies entirely on
quantum annealing, is tested on a variety of event topologies from 2 primary
vertices and 10 tracks up to 5 primary vertices and 15 tracks. It is
benchmarked against simulated annealing executed on a commercial CPU
constrained to the same processor time per anneal as time in the physical
annealer, and performance is found to be comparable for small numbers of
vertices with an intriguing advantage noted for 2 vertices and 16 tracks
Ferromagnetic Domain Structure of La0.78Ca0.22MnO3 Single Crystals
The magneto-optical technique has been employed to observe spontaneous
ferromagnetic domain structures in La0.78Ca0.22MnO3 single crystals. The
magnetic domain topology was found to be correlated with the intrinsic twin
structure of the investigated crystals. With decreasing temperature the regular
network of ferromagnetic domains undergoes significant changes resulting in
apparent rotation of the domain walls in the temperature range of 70-150 K. The
apparent rotation of the domain walls can be understood in terms of the
Jahn-Teller deformation of the orthorhombic unit cell, accompanied by
additional twinning.Comment: 7 pages, 5 figures, to be published in PR
On the distribution of career longevity and the evolution of home run prowess in professional baseball
Statistical analysis is a major aspect of baseball, from player averages to
historical benchmarks and records. Much of baseball fanfare is based around
players exceeding the norm, some in a single game and others over a long
career. Career statistics serve as a metric for classifying players and
establishing their historical legacy. However, the concept of records and
benchmarks assumes that the level of competition in baseball is stationary in
time. Here we show that power-law probability density functions, a hallmark of
many complex systems that are driven by competition, govern career longevity in
baseball. We also find similar power laws in the density functions of all major
performance metrics for pitchers and batters. The use of performance-enhancing
drugs has a dark history, emerging as a problem for both amateur and
professional sports. We find statistical evidence consistent with
performance-enhancing drugs in the analysis of home runs hit by players in the
last 25 years. This is corroborated by the findings of the Mitchell Report [1],
a two-year investigation into the use of illegal steroids in major league
baseball, which recently revealed that over 5 percent of major league baseball
players tested positive for performance-enhancing drugs in an anonymous 2003
survey.Comment: 5 pages, 5 figures, 2-column revtex4 format. Revision has change of
title, a figure added, and minor changes in response to referee comment
Quantum and classical echoes in scattering systems described by simple Smale horseshoes
We explore the quantum scattering of systems classically described by binary
and other low order Smale horseshoes, in a stage of development where the
stable island associated with the inner periodic orbit is large, but chaos
around this island is well developed. For short incoming pulses we find
periodic echoes modulating an exponential decay over many periods. The period
is directly related to the development stage of the horseshoe. We exemplify our
studies with a one-dimensional system periodically kicked in time and we
mention possible experiments.Comment: 7 pages with 6 reduced quality figures! Please contact the authors
([email protected]) for an original good quality pre-prin
From patriarchal socialism to grassroots capitalism: The role of female entrepreneurs in the transition of North Korea
© 2018 Elsevier Ltd Since the collapse of North Korea's command economy in the 1990s, a large number of women have become entrepreneurs. This remarkable feature of North Korean marketisation cannot be adequately explained by female entrepreneur (FE) deficit premises, which highlight women's supposed shortcomings in what is considered a male enterprise. Based on in-depth interviews with female North Korean defectors, and viewing entrepreneurship as a catalyst for socio-cultural change, this paper questions how FEs emerged in North Korea and whether women's market participation influences gender relations, or attitudes toward the North Korean regime. There have been noticeable changes in gender roles, son preference and choice of marriage partners. Our findings suggest that female entrepreneurship has the potential to both challenge and support the North Korean system. This research significantly advances scholarship on gender and entrepreneurship by adopting a constructionist approach to gender and transcending the prevalence of descriptive analysis of gendered entrepreneurial practices
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