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

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

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

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 $p_i,q_i$ 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 $99\%$, 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 $163$ 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 $(3.3\pm 1.0)\%$ for very inclined air showers at $25\, \mathrm{m}$ to $(20.3\pm 1.3)\%$ for almost vertical showers at $225\, \mathrm{m}$. Both dependencies are in qualitative agreement with theoretical predictions.Comment: 22 pages, 14 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.

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