3,540 research outputs found
Three-body forces and proton-rich nuclei
We present the first study of three-nucleon (3N) forces for proton-rich
nuclei along the N=8 and N=20 isotones. Our results for the ground-state
energies and proton separation energies are in very good agreement with
experiment where available, and with the empirical isobaric multiplet mass
equation. We predict the spectra for all N=8 and N=20 isotones to the proton
dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In
all other cases, we provide first predictions based on nuclear forces. Our
results are also very promising for studying isospin symmetry breaking in
medium-mass nuclei based on chiral effective field theory.Comment: 5 pages, 4 figures, minor changes, published versio
Two-neutrino double electron capture on Xe based on an effective theory and the nuclear shell model
We study the two-neutrino double electron capture on Xe based on an
effective theory (ET) and large-scale shell model calculations, two modern
nuclear structure approaches that have been tested against Gamow-Teller and
double-beta decay data. In the ET, the low-energy constants are fit to electron
capture and transitions around xenon. For the nuclear shell model,
we use an interaction in a large configuration space that reproduces the
spectroscopy of nuclei in this mass region. For the dominant transition to the
Te ground state, we find half-lives y for the ET and y for the shell model. The ET uncertainty leads to
a half-life almost entirely consistent with present experimental limits and
largely within the reach of ongoing experiments. The shell model half-life
range overlaps with the ET, but extends less beyond current limits. Our
findings thus suggest that the two-neutrino double electron capture on
Xe has a good chance to be discovered by ongoing or future experiments.
In addition, we present results for the two-neutrino double electron capture to
excited states of Te.Comment: 5 pages, 2 figure
Mimicking anti-viruses with machine learning and entropy profiles
The quality of anti-virus software relies on simple patterns extracted from binary files. Although these patterns have proven to work on detecting the specifics of software, they are extremely sensitive to concealment strategies, such as polymorphism or metamorphism. These limitations also make anti-virus software predictable, creating a security breach. Any black hat with enough information about the anti-virus behaviour can make its own copy of the software, without any access to the original implementation or database. In this work, we show how this is indeed possible by combining entropy patterns with classification algorithms. Our results, applied to 57 different anti-virus engines, show that we can mimic their behaviour with an accuracy close to 98% in the best case and 75% in the worst, applied on Windows’ disk resident malware
Uncertainties in constraining low-energy constants from H decay
We discuss the uncertainties in constraining low-energy constants of chiral
effective field theory from H decay. The half-life is very
precisely known, so that the Gamow-Teller matrix element has been used to fit
the coupling of the axial-vector current to a short-range two-nucleon
pair. Because the same coupling also describes the leading one-pion-exchange
three-nucleon force, this in principle provides a very constraining fit,
uncorrelated with the H binding energy fit used to constrain another
low-energy coupling in three-nucleon forces. However, so far such H
half-life fits have only been performed at a fixed cutoff value. We show that
the cutoff dependence due to the regulators in the axial-vector two-body
current can significantly affect the Gamow-Teller matrix elements and
consequently also the extracted values for the coupling constant. The
degree of the cutoff dependence is correlated with the softness of the employed
NN interaction. As a result, present three-nucleon forces based on a fit to
H decay underestimate the uncertainty in . We explore a range
of values that is compatible within cutoff variation with the
experimental H half-life and estimate the resulting uncertainties for
many-body systems by performing calculations of symmetric nuclear matter.Comment: 9 pages, 11 figures, published version, includes Erratum, which
corrects Figs. 2-6 due to the incorrect c_D relation between 3N forces and
two-body currents use
El respeto a la verdad como límite de la libertad de expresión
The law regulating the press affirms -as do the most renowned texts at
the international level upon the consecration of the right to information- that
freedom of expression cannot be unlimited but rather that it must on the
contrary accommodate itself to some guidelines which layout the frontiers of
this right. Among the restraints most universally imposed upon the freedom
of emission of thought, there exists one which clearly stands out, due to
its generalized acceptance: the respect of truth.
Truth walks hand in hand with sincerity. Any type of duality, any rupture
between intimate thought and the expression of this thought is correctly
understood as the lack of sincerity and therefore as the lack of truth.
The right to information which belongs to the public requires objective
and truthful contento Any kind of manipulation, any falsehood committed by
the social communications media therefore implies a violation of this basic
right.
Commutative justice demands the equilibrium between the counteractions
involved: if the people buy newspapers, it is because they expect to receive
objective information; justice demands that they be given the truth which
they have sought to acquire. Without fraud nor half-truths. For this reason,
moralists and theologians have been able to affirm that truth is a "pars
justitiae-. Truth, however, does not have an absolute value. -It is not always
convenient to say all the truth. the moralists subtlely point out. At times,
a secret can be more respectable than an open indiscretion: the safeguard
of national security, the prudence that must be a guiding principie of courts
of law, and the respect due to the honor and the privacy of the individual
are just a few of the many barriers which must be raised in the stream of
unrestrained information.
However true it may be that it is never licit to consciously communicate
falsehood, in some cases there may exist an excuse for mistakes made by
the professional, especially when he has to work with second-hand materials.
Just the same, no error can ever be allowed to slip by through un excusable
ignorance.
Professional deontology must be very demanding at the hour of programming
retractions in those cases of false information being given. The media
must have the courage to rectify whenever the mendacity of what has been
transmitted has been discovered -a posteriori-; in such an event, there must
not exist any fear of suffering a possible setback stemming from the disavowal
of its editors and collaborators.
For economic reasons, the truth and the information given may clash
head-on in the realm of advertising. There lies the danger of editorial publicity
whereby the message can be distorted or veiled with regard to the public.
Here again, a demanding code of ethics should clearly state -without any
kind of watering-down- the guidelines through which the advertising message
is sufficiently identified
Microwaving Wastes for Producing Syngas
This paper discloses the research carried out at MCAT (INCAR-CSIC) in the last years, which has been aimed to develop a new microwave induced process (MIP) for the conversion of biosolids into syngas. The different organic substrates that can be processed, the operational conditions that lead to a maximum production of syngas and the characteristics of the syngas as well as the by-products obtained are discussed. Particular emphasis is placed on the partial recycling of the solid fraction and its role as microwave susceptor and as a catalyst of some of the gasification reactions taking place during the MIP of the organic residues. Additionally, some insights on the energy costs of the process are also given.Peer reviewe
Coexistence of spherical states with deformed and superdeformed bands in doubly magic 40-Ca; A shell model challenge
Large scale shell model calculations, with dimensions reaching 10**9, are
carried out to describe the recently observed deformed (ND) and superdeformed
(SD) bands based on the first and second excited 0+ states of 40-Ca at 3.35-MeV
and 5.21-MeV respectively. A valence space comprising two major oscillator
shells, sd and pf, can accommodate most of the relevant degrees of freedom of
this problem. The ND band is dominated by configurations with four particles
promoted to the pf-shell (4p-4h in short). The SD band by 8p-8h configurations.
The ground state of 40-Ca is strongly correlated, but the closed shell still
amounts to 65%. The energies of the bands are very well reproduced by the
calculations. The out-band transitions connecting the SD band with other states
are very small and depend on the details of the mixing among the different
np-nh configurations, in spite of that, the calculation describes them
reasonably. For the in-band transition probabilities along the SD band, we
predict a fairly constant transition quadrupole moment Q_0(t)~170 e fm**2 up to
J=10, that decreases toward the higher spins. We submit also that the J=8
states of the deformed and superdeformed band are maximally mixed.Comment: 12 pages, 9 figure
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