9 research outputs found
Enlarging the window for radiative leptogenesis
We investigate the scenario of resonant thermal leptogenesis, in which the
leptonic asymmetries are generated through renormalization group corrections
induced at the leptogenesis scale. In the framework of the standard model
extended by three right-handed heavy Majorana neutrinos with masses M1 = M2 <<
M3 at some high scale, we show that the mass splitting and CP-violating effects
induced by renormalization group corrections can lead to values of the CP
asymmetries large enough for a successful leptogenesis. In this scenario, the
low-energy neutrino oscillation data can also be easily accommodated. The
possibility of having an underlying symmetry behind the degeneracy in the
right-handed neutrino mass spectrum is also discussed.Comment: 20 pages, 2 figures, final version to appear in Phys. Lett.
A critique of non-extensive q-entropy for thermal statistics
During the past dozen years there have been numerous articles on a relation
between entropy and probability which is non-additive and has a parameter
that depends on the nature of the thermodynamic system under consideration. For
this relation corresponds to the Boltzmann-Gibbs entropy, but for other
values of it is claimed that it leads to a formalism which is consistent
with the laws of thermodynamics. However, it is shown here that the joint
entropy for systems having {\it different} values of is not defined in this
formalism, and consequently fundamental thermodynamic concepts such as
temperature and heat exchange cannot be considered for such systems. Moreover,
for the probability distribution for weakly interacting systems does
not factor into the product of the probability distribution for the separate
systems, leading to spurious correlations and other unphysical consequences,
e.g. non-extensive energy, that have been ignored in various applications given
in the literature
Atenção humanizada ao recém-nascido de baixo-peso. Método Canguru e cuidado centrado na família: correspondências e especificidades
NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics
Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset