18,895 research outputs found
Naturally light invisible axion in models with large local discrete symmetries
We show that by introducing appropriate local symmetries in
electroweak models it is possible to implement an automatic Peccei-Quinn
symmetry keeping at the same time the axion protected against gravitational
effects. Although we consider here only an extension of the standard model and
a particular 3-3-1 model, the strategy can be used in any kind of electroweak
model. An interesting feature of this 3-3-1 model is that if: {\it i)} we add
right-handed neutrinos, {\it ii)} the conservation of the total lepton number,
and {\it iii)} a symmetry, the and the chiral Peccei-Quinn
are both accidental symmetries in the sense that they are not
imposed on the Lagrangian but they are just the consequence of the particle
content of the model, its gauge invariance, renormalizability and Lorentz
invariance. In addition, this model has no domain wall problem.Comment: Some changes and a new reference added, 7 page
Naturally light invisible axion and local Z_{13} times Z_3 symmetries
We show that by imposing local symmetries in an
electroweak model we can implement an invisible axion in
such a way that (i) the Peccei-Quinn symmetry is an automatic symmetry of the
classical Lagrangian; and (ii) the axion is protected from semi classical
gravitational effects. In order to be able to implement such a large discrete
symmetry, and at the same time allow a general mixing in each charge sector, we
introduce right-handed neutrinos and enlarge the scalar sector of the model.
The domain wall problem is briefly considered.Comment: PQ charges and typos correcte
Monte Carlo Simulations of Ultrathin Magnetic Dots
In this work we study the thermodynamic properties of ultrathin ferromagnetic
dots using Monte Carlo simulations. We investigate the vortex density as a
function of the temperature and the vortex structure in monolayer dots with
perpendicular anisotropy and long-range dipole interaction. The interplay
between these two terms in the hamiltonian leads to an interesting behavior of
the thermodynamic quantities as well as the vortex density.Comment: 10 figure
The Invisible Axion and Neutrino Masses
We show that in any invisible axion model due to the effects of effective
non-renormalizable interactions related to an energy scale near the
Peccei-Quinn, grand unification or even the Planck scale, active neutrinos
necessarily acquire masses in the sub-eV range. Moreover, if sterile neutrinos
are also included and if appropriate cyclic symmetries are imposed, it is
possible that some of these neutrinos are heavy while others are light.Comment: An example included and new references added. To appear in PR
Untangling Fine-Grained Code Changes
After working for some time, developers commit their code changes to a
version control system. When doing so, they often bundle unrelated changes
(e.g., bug fix and refactoring) in a single commit, thus creating a so-called
tangled commit. Sharing tangled commits is problematic because it makes review,
reversion, and integration of these commits harder and historical analyses of
the project less reliable. Researchers have worked at untangling existing
commits, i.e., finding which part of a commit relates to which task. In this
paper, we contribute to this line of work in two ways: (1) A publicly available
dataset of untangled code changes, created with the help of two developers who
accurately split their code changes into self contained tasks over a period of
four months; (2) a novel approach, EpiceaUntangler, to help developers share
untangled commits (aka. atomic commits) by using fine-grained code change
information. EpiceaUntangler is based and tested on the publicly available
dataset, and further evaluated by deploying it to 7 developers, who used it for
2 weeks. We recorded a median success rate of 91% and average one of 75%, in
automatically creating clusters of untangled fine-grained code changes
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