6,662 research outputs found
The XRF080109-SN2008D and a decade of GRB-Jet-SN connection
Last and nearest GRB-XRF 080109 has been an exceptional lesson on GRB nature.
After a decade (since 25 April 08) we know that Supernovae may often contain a
Jet. Its persistent activity may shine on axis as a GRBs. Such a persistent,
thin beamed gamma jet may be powered by either a BH (Black Holes) or Pulsars.
Late stages of these jets may loose the SN traces and appear as a short GRB or
a long orphan GRB (depending on jet angular velocity and view angle). XRF are
peripherical viewing of the jets. These precessing and spinning gamma jet are
originated by Inverse Compton and-or Synchrotron Radiation at pulsars or
micro-quasars sources, by ultra-relativistic electrons. These Jets are most
powerful at Supernova birth, blazing, once on axis, to us and flashing GRB
detector. The trembling of the thin jet explains naturally the observed erratic
multi-explosive structure of different GRBs. The jets are precessing (by binary
companion or inner disk asymmetry) and decaying by power on time scales of few
hours, but they keep staying inside the observer cone view only a few seconds
duration times (GRB); the jet is thinner in gamma and wider in X band. This
explain the wider and longer X GRB afterglow duration and the rare presence of
X-ray precursors.Comment: 11 pages, 12 figure
Critical Endpoint and Inverse Magnetic Catalysis for Finite Temperature and Density Quark Matter in a Magnetic Background
In this article we study chiral symmetry breaking for quark matter in a
magnetic background, , at finite temperature and quark chemical
potential, , making use of the Ginzburg-Landau effective action formalism.
As a microscopic model to compute the effective action we use the renormalized
quark-meson model. Our main goal is to study the evolution of the critical
endpoint, , as a function of the magnetic field strength, and
investigate on the realization of inverse magnetic catalysis at finite chemical
potential. We find that the phase transition at zero chemical potential is
always of the second order; for small and intermediate values of ,
moves towards small , while for larger it moves
towards moderately larger values of . Our results are in agreement with
the inverse magnetic catalysis scenario at finite chemical potential and not
too large values of the magnetic field, while at larger direct magnetic
catalysis sets in.Comment: 6 pages, 2 figure
La soberanĂa argentina en el Continente Antártico - Por JosĂ© Carlos Vittone - Buenos Aires, El Ateneo, 1944.
Fil: Oliva, Enrique P..
Universidad Nacional de Cuyo. Facultad de FilosofĂa y Letra
A type system for Continuation Calculus
Continuation Calculus (CC), introduced by Geron and Geuvers, is a simple
foundational model for functional computation. It is closely related to lambda
calculus and term rewriting, but it has no variable binding and no pattern
matching. It is Turing complete and evaluation is deterministic. Notions like
"call-by-value" and "call-by-name" computation are available by choosing
appropriate function definitions: e.g. there is a call-by-value and a
call-by-name addition function. In the present paper we extend CC with types,
to be able to define data types in a canonical way, and functions over these
data types, defined by iteration. Data type definitions follow the so-called
"Scott encoding" of data, as opposed to the more familiar "Church encoding".
The iteration scheme comes in two flavors: a call-by-value and a call-by-name
iteration scheme. The call-by-value variant is a double negation variant of
call-by-name iteration. The double negation translation allows to move between
call-by-name and call-by-value.Comment: In Proceedings CL&C 2014, arXiv:1409.259
Dynamic shear suppression in quantum phase space
© 2019 American Physical Society. All rights reserved.Classical phase space flow is inviscid. Here we show that in quantum phase space Wigner's probability current J can be effectively viscous. This results in shear suppression in quantum phase space dynamics which enforces Zurek's limit for the minimum size scale of spotty structures that develop dynamically. Quantum shear suppression is given by gradients of the quantum terms of J's vorticity. Used as a new measure of quantum dynamics applied to several evolving closed conservative 1D bound state systems, we find that shear suppression explains the saturation at Zurek's scale limit and additionally singles out special quantum states.Peer reviewe
The design and analysis of a reconfigurable flight control system for advanced civil aircraft
This work is concerned with the design of a pitch-rate-command-attitude-hold command and stability augmentation system in order that the augmented aircraft meets the Gibson dropback criterion, the Gibson phase-rate criterion and MIL-F-8785C requirements. The work shows two methods of design, pole-placement and optimal control, and discusses the design procedures, the advantages and disadvantages of each method. The work is also concerned with the redundancy aspect of the control law design, and so not only a sensor based design bu also an observer-based design are investigated. In order to design the observer-based control law. a Doyle-Stein observer was implemented. Two methods showing how to design the observer are discussed and presented, and the special characteristics of this kind of observer are also considered. The performance of the observer-based control law was compared with that of the sensor-based control law. The failure transients and characteristics of the control law are also studied and presented. Finally an evaluation of the control law was carried out with a non-linear model of the B-747 aircraft, and a simple altitude-hold autopilot was designed to work together with the stability augmentation control law
The TNG Near Infrared Camera Spectrometer
NICS (acronym for Near Infrared Camera Spectrometer) is the near-infrared
cooled camera-spectrometer that has been developed by the Arcetri Infrared
Group at the Arcetri Astrophysical Observatory, in collaboration with the
CAISMI-CNR for the TNG (the Italian National Telescope Galileo at La Palma,
Canary Islands, Spain).
As NICS is in its scientific commissioning phase, we report its observing
capabilities in the near-infrared bands at the TNG, along with the measured
performance and the limiting magnitudes. We also describe some technical
details of the project, such as cryogenics, mechanics, and the system which
executes data acquisition and control, along with the related software.Comment: 7 pages, 5 figures, compiled with A&A macros. A&A in pres
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