5,582 research outputs found
Neutrinoless double beta decay with and without Majoron-like boson emission in a 3-3-1 model
We consider the contributions to the neutrinoless double beta decays in a
electroweak model. We show that for a range of the
parameters in the model there are diagrams involving vector-vector-scalar and
trilinear scalar couplings which can be potentially as contributing as the
light massive Majorana neutrino exchange one. We use these contributions to
obtain constraints upon some mass scales of the model, like the masses of the
new charged vector and scalar bosons. We also consider briefly the decay in
which besides the two electrons a Majoron-like boson is emitted.Comment: Revtex, 10 pages and 8 eps figures. Extended version to be published
in Physical Review
Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors
We consider a real massless scalar field inside a cavity with two moving
mirrors in a two-dimensional spacetime, satisfying Dirichlet boundary condition
at the instantaneous position of the boundaries, for arbitrary and relativistic
laws of motion. Considering vacuum as the initial field state, we obtain
formulas for the exact value of the energy density of the field and the quantum
force acting on the boundaries, which extend results found in previous papers.
For the particular cases of a cavity with just one moving boundary,
non-relativistic velocities, or in the limit of infinity length of the cavity
(a single mirror), our results coincide with those found in the literature.Comment: 6 pages 9 figure
Phase diagram of the antiferromagnetic XY model in two dimensions in a magnetic field
The phase diagram of the quasi-two-dimensional easy-plane antiferromagnetic
model, with a magnetic field applied in the easy plane, is studied using the
self-consistent harmonic approximation. We found a linear dependence of the
transition temperature as a function of the field for large values of the
field. Our results are in agreement with experimental data for the spin-1
honeycomb compound BaNi_2V_2O_3Comment: 3 page
Sustainability Assessment of indicators for integrated water resources management
The scientific community strongly recommends the adoption of indicators for the evaluation and monitoring of progress towards sustainable development. Furthermore, international organizations consider that indicators are powerful decision-making tools. Nevertheless, the quality and reliability of the indicators depends on the application of adequate and appropriate criteria to assess them. The general objective of this study was to evaluate how indicators related to water use and management perform against a set of sustainability criteria. Our research identified 170 indicators related to water use and management. These indicators were assessed by an international panel of experts that evaluated whether they fulfil the four sustainability criteria: social, economic, environmental, and institutional. We employed an evaluation matrix that classified all indicators according to the DPSIR (Driving Forces, Pressures, States, Impacts and Responses) framework. A pilot study served to test and approve the research methodology before carrying out the full implementation. The findings of the study show that 24 indicators comply with the majority of the sustainability criteria; 59 indicators are bi-dimensional (meaning that they comply with two sustainability criteria); 86 are one-dimensional indicators (fulfilling just one of the four sustainability criteria) and one indicator do not fulfil any of the sustainability criteria.Postprint (author's final draft
Current differential line protection using a pattern recognition method
This paper presents a new approach to a numerical current differential protection for the transmission lines. The current differential algorithm uses a pattern recognition method. First the acquired current signals are transformed into “dqo” components by applying the Park transformation. The transformed currents will originate typical patterns according the fault type. Using a pattern recognition algorithm the different faulty conditions are identified. Several tests under different fault conditions were performed. The obtained results allow verifying the effectiveness of the proposed approach
Searching for new thermally emitting isolated neutron stars in the 2XMMp catalogue - Discovery of a promising candidate
The group of 7 thermally emitting and radio-quiet isolated neutron stars
(INSs) discovered by ROSAT constitutes a nearby population which locally
appears to be as numerous as that of the classical radio pulsars. So far,
attempts to enlarge this particular group of INSs finding more remote objects
failed to confirm any candidate. We found in the 2XMMp catalogue a handful of
sources with no catalogued counterparts and with X-ray spectra similar to those
of the ROSAT discovered INSs, but seen at larger distances and thus undergoing
higher interstellar absorptions. In order to rule out alternative
identifications such as an AGN or a CV, we obtained deep ESO-VLT and SOAR
optical imaging for the X-ray brightest candidates. We report here on the
current status of our search and discuss the possible nature of our candidates.
We focus particularly on the X-ray brightest source of our sample, 2XMM
J104608.7-594306, observed serendipitously over more than four years by the
XMM-Newton Observatory. A lower limit on the X-ray to optical flux ratio of ~
300 together with a stable flux and soft X-ray spectrum make it the most
promising thermally emitting INS candidate. Beyond the finding of new members,
our study aims at constraining the space density of this population at large
distances and at determining whether their apparently high local density is an
anomaly or not.Comment: 3 pages, 2 figures, proceedings of the conference "40 Years of
Pulsars", 12-17 August 2007, Montreal, Canad
Neutrino Decay and Neutrinoless Double Beta Decay in a 3-3-1 Model
In this work we show that the implementation of spontaneous breaking of the
lepton number in the 3-3-1 model with right-handed neutrinos gives rise to fast
neutrino decay with majoron emission and generates a bunch of new contributions
to the neutrinoless double beta decay.Comment: Version accepted for publication in the Phys. Rev.
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