886 research outputs found
Propagation of high-energy neutrinos in a background of ultralight scalar dark matter
If high-energy neutrinos propagate in a background of ultralight scalar field
particles of dark matter (eV), neutrino-dark matter
interactions can play a role and affect the neutrino flux. In this work we
analyse this effect using transport equations that account for the neutrino
regeneration as well as absorption, and we consider the neutrino flux
propagation in the extragalactic medium and also through the galactic halo of
dark matter. We show the results for the final flux to arrive on Earth for
different cases of point and diffuse neutrino fluxes. {We conclude that this
type of neutrino interactions with ultralight scalar particles as dark matter
can yield very different results in the neutrino flux and in the flavor ratios
that can be measured in neutrino detectors such as IceCube.Comment: 11 pages, 11 figures, accepted for publication in Astroparticle
Physic
Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: Disordered Case
We study theoretically the \emph{return probability experiment}, used to
measure the dephasing time , in a double quantum dot (DQD) in
semiconducting carbon nanotubes (CNTs) with spin-orbit coupling and disorder
induced valley mixing. Dephasing is due to hyperfine interaction with the spins
of the C nuclei. Due to the valley and spin degrees of freedom four
bounded states exist for any given longitudinal mode in the quantum dot. At
zero magnetic field the spin-orbit coupling and the valley mixing split those
four states into two Kramers doublets. The valley mixing term for a given dot
is determined by the intra-dot disorder and therefore the states in the Kramers
doublets belonging to different dots are different. We show how nonzero
single-particle interdot tunneling amplitudes between states belonging to
different doublets give rise to new avoided crossings, as a function of
detuning, in the relevant two particle spectrum, crossing over from the two
electrons in one dot states configuration, , to the one electron in each
dot configuration, . In contrast to the clean system, multiple
Landau-Zener processes affect the separation and the joining stages of each
single-shot measurement and they affect the outcome of the measurement in a way
that strongly depends on the initial state. We find that a well-defined return
probability experiment is realized when, at each single-shot cycle, the (0,2)
ground state is prepared. In this case, valley mixing increases the saturation
value of the measured return probability, whereas the probability to return to
the (0,2) ground state remains unchanged. Finally, we study the effect of the
valley mixing in the high magnetic field limit; for a parallel magnetic field
the predictions coincide with a clean nanotube, while the disorder effect is
always relevant with a magnetic field perpendicular to the nanotube axis.Comment: 22 pages, 11 figure
On the Radio Polarization Signature of Efficient and Inefficient Particle Acceleration in Supernova Remnant SN 1006
We present a radio polarization study of SN 1006, based on combined VLA and
ATCA observations at 20 cm that resulted in sensitive images with an angular
resolution of 10 arcsec. The fractional polarization in the two bright radio
and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern
sector, where the radio and non-thermal X-ray emission are much weaker, the
polarization fraction reaches a value of 0.6 +- 0.2, close to the theoretical
limit of 0.7. We interpret this result as evidence of a disordered, turbulent
magnetic field in the lobes, where particle acceleration is believed to be
efficient, and a highly ordered field in the southeast, where the acceleration
efficiency has been shown to be very low. Utilizing the frequency coverage of
our observations, an average rotation measure of ~12 rad/m2 is determined from
the combined data set, which is then used to obtain the intrinsic direction of
the magnetic field vectors. While the orientation of magnetic field vectors
across the SNR shell appear radial, a large fraction of the magnetic vectors
lie parallel to the Galactic Plane. Along the highly polarized southeastern
rim, the field is aligned tangent to the shock, and therefore also nearly
parallel to the Galactic Plane. These results strongly suggest that the ambient
field surrounding SN 1006 is aligned with this direction (i.e., from northeast
to southwest) and that the bright lobes are due to a polar cap geometry. Our
study establishes that the most efficient particle acceleration and generation
of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic
field direction and shock normal are quasi-parallel, while inefficient
acceleration and little to no generation of magnetic turbulence obtains for the
quasi-perpendicular case.Comment: Accepted for publication in Astronomical Journa
Post-Dollarization Narratives of Economic Literacy in Ecuador
Research Topic
This study addresses how the economic narratives of conversation participants in Ecuador after dollarization permeates the concepts of self, and quality of life, binding both into a personal economic story that describes a person\u27s economic narrative towards a definition of economic literacy.
Research Theory and Protocol
Through critical hermeneutic theory formulated by Paul Ricoeur (1992) and the inquiry protocol developed by Ellen Herda (1999), the interpretive categories of narrative identi-ty, text, and imagination were applied to this study.
Research Categories
The narratives describe the stories of the people of Ecuador pursuing daily tasks in their economy. The text refers to meaningful activity associated with the economic sphere, which is later defined as economic text. Imagination provides the medium for the people of Ecuador to realize their economic goals through entrepreneurship.
Findings
The study revealed the following four findings: dollarization promotes suspicion towards nefarious activities such as money laundering; in the course of daily cash transactions, the lack of smaller coin denominations creates challenges; the people of Ecuador still yearn for and identify with their prior currency, the sucre; lastly, imagination plays an active role in the development of entrepreneurship. This study provides a perspective on how economic literacy influences quality of life and the need for people to become economically literate. This study also substantiates how the influence of economic activities on the quality of life is of such magnitude that some people are driven to poverty while others continue to thrive
On hadronic beam models for quasars and microquasars
Most of the hadronic jet models for quasars (QSOs) and microquasars (MQs)
found in literature represent beams of particles (e.g. protons). These
particles interact with the matter in the stellar wind of the companion star in
the system or with crossing clouds, generating gamma-rays via proton-proton
processes. Our aim is to derive the particle distribution in the jet as seen by
the observer, so that proper computation of the -ray and neutrino
yields can be done. We use relativistic invariants to obtain the transformed
expressions in the case of a power-law and power-law with a cutoff particle
distribution in the beam. We compare with previous expressions used earlier in
the literature. We show that formerly used expressions for the particle
distributions in the beam as seen by the observer are in error, differences
being strongly dependent on the viewing angle. For example, for
( is the Lorentz factor of the blob) and angles larger than , the earlier-used calculation entails an over-prediction (order of
magnitude or more) of the proton spectra for , whereas it always
over-predicts (two orders of magnitude) the proton spectrum at lower energies,
disregarding the viewing angle. All the results for photon and neutrino fluxes
in hadronic models in beams that have made use of the earlier calculation are
affected. Given that correct gamma-ray fluxes will be in almost any case
significantly diminished in comparison with published results, and that the
time of observations in Cherenkov facilities grows with the square of the
flux-reduction factor in a statistically limited result, the possibility of
observing hadronic beams is undermined.Comment: Accepted for publication in A&A Letter
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