4,232 research outputs found
Governing dynamics by squeezing in a system of cold trapped ions
We consider a system of laser-cooled ions in a linear harmonic trap and study
the phenomenon of squeezing exchange between their internal and motional
degrees of freedom. An interesting relation between the quantum noise reduction
(squeezing) and the dynamical evolution is found when the internal and motional
subsystems are prepared in properly squeezed (intelligent) states.
Specifically, the evolution of the system is fully governed by the relative
strengths of spectroscopic and motional squeezing, including the phenomenon of
total cancellation of the interaction when the initial squeezing parameters are
equal.Comment: REVTeX, 5 pages, 2 figures, to appear in Phys. Rev.
Radiation from matter entrainment in astrophysical jets: the AGN case
Jets are found in a variety of astrophysical sources, from young stellar
objects to active galactic nuclei. In all the cases the jet propagates with a
supersonic velocity through the external medium, which can be inhomogeneous,
and inhomogeneities could penetrate into the jet. The interaction of the jet
material with an obstacle produces a bow shock in the jet in which particles
can be accelerated up to relativistic energies and emit high-energy photons. In
this work, we explore the active galactic nuclei scenario, focusing on the
dynamical and radiative consequences of the interaction at different jet
heights. We find that the produced high-energy emission could be detectable by
the current gamma-ray telescopes. In general, the jet-clump interactions are a
possible mechanism to produce (steady or flaring) high-energy emission in many
astrophysical sources in which jets are present.Comment: 4 pages, 2 figures. Accepted for publication in the Proceedings of
the 275 IAU Symposium: "Jets at all Scales", held in Buenos Aires, September
13-17, 201
Relaciones entre nutrientes y clorofila "a" en las aguas de la albufera de AlcĂşdia (Mallorca). Primeros resultados
Why Are some Filipino Children not in School?
What are the factors that contribute to the nonparticipation of children in school? Who are the ones accountable to this complicating issue? This Note identifies some factors and looks deeper into each of them.poverty, education, Philippines, carbon tax, carbon dioxide emission, school participation, out-of-school children
High-energy emission from jet-clump interactions in microquasars
High-mass microquasars are binary systems consisting of a massive star and an
accreting compact object from which relativistic jets are launched. There is
considerable observational evidence that winds of massive stars are clumpy.
Individual clumps may interact with the jets in high-mass microquasars to
produce outbursts of high-energy emission. Gamma-ray flares have been detected
in some high-mass X-ray binaries, such as Cygnus X-1, and probably in LS 5039
and LS I+61 303. We predict the high-energy emission produced by the
interaction between a jet and a clump of the stellar wind in a high-mass
microquasar. Assuming a hydrodynamic scenario for the jet-clump interaction, we
calculate the spectral energy distributions produced by the dominant
non-thermal processes: relativistic bremsstrahlung, synchrotron and inverse
Compton radiation, for leptons, and for hadrons, proton-proton collisions.
Significant levels of emission in X-rays (synchrotron), high-energy gamma rays
(inverse Compton), and very high-energy gamma rays (from the decay of neutral
pions) are predicted, with luminosities in the different domains in the range ~
10^{32}-10^{35} erg/s. The spectral energy distributions vary strongly
depending on the specific conditions. Jet-clump interactions may be detectable
at high and very high energies, and provide an explanation for the fast TeV
variability found in some high-mass X-ray binary systems.
Our model can help to infer information about the properties of jets and
clumpy winds by means of high-sensitivity gamma-ray astronomy.Comment: Accepted for publication in A&A (10 pages, 8 figures
Some Issues on Low Participation Rates in Basic Education
Despite the various efforts to improve the Philippines` education system, why does this country still have low participation rates in education? What are the reasons behind the growing numbers of out-of-school children? What are the reasons for their nonattendance? This Note delves deeper into the issue.Philippines, basic education, school participation, out-of-school children
Optimal discrimination of quantum states with a fixed rate of inconclusive outcomes
In this paper we present the solution to the problem of optimally
discriminating among quantum states, i.e., identifying the states with maximum
probability of success when a certain fixed rate of inconclusive answers is
allowed. By varying the inconclusive rate, the scheme optimally interpolates
between Unambiguous and Minimum Error discrimination, the two standard
approaches to quantum state discrimination. We introduce a very general method
that enables us to obtain the solution in a wide range of cases and give a
complete characterization of the minimum discrimination error as a function of
the rate of inconclusive answers. A critical value of this rate is identified
that coincides with the minimum failure probability in the cases where
unambiguous discrimination is possible and provides a natural generalization of
it when states cannot be unambiguously discriminated. The method is illustrated
on two explicit examples: discrimination of two pure states with arbitrary
prior probabilities and discrimination of trine states
Why some Firms Innovate and Why others Do not
What are the factors that make some firms innovate while others do not? Does location matter? Or firm size? How about the presence of more female workers in a firm? This Policy Note cites the factors.innovation, Philippines, process innovation, product innovation, organizational innovation
Gamma-ray emission from massive young stellar objects
Massive stars form in dense and massive molecular cores. The exact formation
mechanism is unclear, but it is possible that some massive stars are formed by
processes similar to those that produce the low-mass stars, with
accretion/ejection phenomena occurring at some point of the evolution of the
protostar. This picture seems to be supported by the detection of a collimated
stellar wind emanating from the massive protostar IRAS 16547-4247. A triple
radio source is associated with the protostar: a compact core and two radio
lobes. The emission of the southern lobe is clearly non-thermal. Such emission
is interpreted as synchrotron radiation produced by relativistic electrons
locally accelerated at the termination point of a thermal jet. Since the
ambient medium is determined by the properties of the molecular cloud in which
the whole system is embedded, we can expect high densities of particles and
infrared photons. Because of the confirmed presence of relativistic electrons,
inverse Compton and relativistic Bremsstrahlung interactions are unavoidable.
Proton-proton collision should also occur, producing an injection of neutral
pions. In this paper we aim at making quantitative predictions of the spectral
energy distribution of the non-thermal spots generated by massive young stellar
objects, with emphasis on the particular case of IRAS 16547-4247. We present
spectral energy distributions for the southern lobe of this source, for a
variety of conditions. We show that high-energy emission might be detectable
from this object in the gamma-ray domain (MeV to TeV). The source may also be
detectable at X-rays through long exposures with current X-ray instruments.Comment: 8 pages, 6 figures, accepted for publication in A&
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