876 research outputs found
The Galactic cosmic-ray Sun shadow observed by HAWC
The magnetic field of the Solar corona is difficult to measure directly.
However, indirect observations of the solar corona are possible using the
deficit in flux of cosmic rays coming from the direction of the Sun. Low-energy
cosmic rays (~GeV) are deflected by the inner magnetic field of the Sun and the
interplanetary magnetic field frozen into the solar wind. In contrast,
high-energy cosmic rays (~TeV and above) are absorbed in the Sun's photosphere
producing a shadow in the Sun's nominal position viewed from Earth. Several
ground-based instruments have observed the effects of the heliospheric magnetic
field on the size of the sun shadow and its position. The High-Altitude Water
Cherenkov Observatory (HAWC) is an air shower array located in the central
region of Mexico that observes TeV cosmic rays at a rate of about 15 kHz. in
this work, we present preliminary images of the sun shadow from data collected
by HAWC during 2013 and 2014 for different energy ranges.Comment: Presented at the 34th International Cosmic Ray Conference (ICRC2015),
The Hague, The Netherlands. See arXiv:1508.03327 for all HAWC contribution
Individual decision-making by top executives as a valuable resource for strategic management – A resource-based view and dynamic capability approach
Strategy is highly important for organisational success and the achievement of competitive advantage.
Strategy is dynamic and it depends on accurate individual decision-making from medium and high-level
managers and executives. Since managers always formulate strategy, its formulation depends mostly on
their assertive decisions. Making good decisions is a complex task, even more in today’s business world
where a large quantity of information and a dynamic environment forces people to decide without having
complete information. As Shafir, Simonson, & Tversky (1993) point out, "the making of decisions, both big
and small, is often difficult because of uncertainty and conflict". In this paper the author will explain a basic
theoretical framework about top manager's individual decision-making, showing how complex the process
of making high-impact decisions is; then, he will compare this theory with one of the most important
streams in strategic management, the Resource-Based View (RBV) of the firm. Finally, within the context
of individual decision-making and the RBV stream, the author will show how individual decision makers
in top management positions constitute a valuable, rare, non-imitable and non-substitutable resource that
provides sustained competitive advantage
Resource-based view and dynamic capabilities - Achieving competitive advantage through internal resources and competences
Strategy has always been important for success. Whether strategy is applied for military purposes, in large
firms, or even for personal objectives, there are certain key characteristics that every successful strategy
carries on: clear, objective and simple goals; deep knowledge and understanding of the competitive environment;
objective understanding and exploitation of resources; and an effective plan implementation. In this paper, the author’s attention will be focused on the role of internal resources, routines and processes as the bases of sustained competitive advantage (hereafter SCA) into what is now known as the resourcebased
view of the firm (RBV) and Dynamic Capabilities (DC). First, the relevance of RBV and DC approaches
and the main characteristics of those are briefly mentioned. Second, RBV and DC are examined
as an important piece to achieve SCA. Later on, the author deepens into some examples and the manager’s
importance when using these RBV and DC approaches. Then issues related with complexity and undefined
concepts in RBV and DC are briefly mentioned. Finally, conclusions and personal comments are presented
Riemann surfaces, separation of variables and classical and quantum integrability
We show that Riemann surfaces, and separated variables immediately provide
classical Poisson commuting Hamiltonians. We show that Baxter's equations for
separated variables immediately provide quantum commuting Hamiltonians. The
construction is simple, general, and does not rely on the Yang--Baxter
equation.Comment: 10 pages. Fixed a typo, added a referenc
On the Quantum Inverse Problem for the Closed Toda Chain
We reconstruct the canonical operators of the quantum closed Toda
chain in terms of Sklyanin's separated variables.Comment: 16 page
Polarized radio emission from extensive air showers measured with LOFAR
We present LOFAR measurements of radio emission from extensive air showers.
We find that this emission is strongly polarized, with a median degree of
polarization of nearly , and that the angle between the polarization
direction of the electric field and the Lorentz force acting on the particles,
depends on the observer location in the shower plane. This can be understood as
a superposition of the radially polarized charge-excess emission mechanism,
first proposed by Askaryan and the geomagnetic emission mechanism proposed by
Kahn and Lerche. We calculate the relative strengths of both contributions, as
quantified by the charge-excess fraction, for individual air showers. We
find that the measured charge-excess fraction is higher for air showers
arriving from closer to the zenith. Furthermore, the measured charge-excess
fraction also increases with increasing observer distance from the air shower
symmetry axis. The measured values range from for very
inclined air showers at to for almost
vertical showers at . Both dependencies are in qualitative
agreement with theoretical predictions.Comment: 22 pages, 14 figures, accepted for publication in JCA
The radio emission pattern of air showers as measured with LOFAR - a tool for the reconstruction of the energy and the shower maximum
The pattern of the radio emission of air showers is finely sampled with the
Low-Frequency ARray (LOFAR). A set of 382 measured air showers is used to test
a fast, analytic parameterization of the distribution of pulse powers. Using
this parameterization we are able to reconstruct the shower axis and give
estimators for the energy of the air shower as well as the distance to the
shower maximum.Comment: 15 pages, 10 figures, accepted for publication in JCA
A method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles
The mass composition of cosmic rays contains important clues about their
origin. Accurate measurements are needed to resolve long-standing issues such
as the transition from Galactic to extragalactic origin, and the nature of the
cutoff observed at the highest energies. Composition can be studied by
measuring the atmospheric depth of the shower maximum Xmax of air showers
generated by high-energy cosmic rays hitting the Earth's atmosphere. We present
a new method to reconstruct Xmax based on radio measurements. The radio
emission mechanism of air showers is a complex process that creates an
asymmetric intensity pattern on the ground. The shape of this pattern strongly
depends on the longitudinal development of the shower. We reconstruct Xmax by
fitting two-dimensional intensity profiles, simulated with CoREAS, to data from
the LOFAR radio telescope. In the dense LOFAR core, air showers are detected by
hundreds of antennas simultaneously. The simulations fit the data very well,
indicating that the radiation mechanism is now well-understood. The typical
uncertainty on the reconstruction of Xmax for LOFAR showers is 17 g/cm^2.Comment: 12 pages, 10 figures, submitted to Phys. Rev.
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