5,262 research outputs found
Symmetry-preserving contact interaction model for heavy-light mesons
We use a symmetry-preserving regularization method of ultraviolet divergences
in a vector-vector contact interac- tion model for low-energy QCD. The contact
interaction is a representation of nonperturbative kernels used Dyson-Schwinger
and Bethe-Salpeter equations. The regularization method is based on a
subtraction scheme that avoids standard steps in the evaluation of divergent
integrals that invariably lead to symmetry violation. Aiming at the study of
heavy-light mesons, we have implemented the method to the pseudoscalar pion and
Kaon mesons. We have solved the Dyson-Schwinger equation for the u, d and s
quark propagators, and obtained the bound-state Bethe-Salpeter amplitudes in a
way that the Ward-Green-Takahashi identities reflecting global symmetries of
the model are satisfied for arbitrary routing of the momenta running in loop
integrals
Accelerating universes driven by bulk particles
We consider our universe as a 3d domain wall embedded in a 5d dimensional
Minkowski space-time. We address the problem of inflation and late time
acceleration driven by bulk particles colliding with the 3d domain wall. The
expansion of our universe is mainly related to these bulk particles. Since our
universe tends to be permeated by a large number of isolated structures, as
temperature diminishes with the expansion, we model our universe with a 3d
domain wall with increasing internal structures. These structures could be
unstable 2d domain walls evolving to fermi-balls which are candidates to cold
dark matter. The momentum transfer of bulk particles colliding with the 3d
domain wall is related to the reflection coefficient. We show a nontrivial
dependence of the reflection coefficient with the number of internal dark
matter structures inside the 3d domain wall. As the population of such
structures increases the velocity of the domain wall expansion also increases.
The expansion is exponential at early times and polynomial at late times. We
connect this picture with string/M-theory by considering BPS 3d domain walls
with structures which can appear through the bosonic sector of a
five-dimensional supergravity theory.Comment: To appear in Phys. Rev. D, 16 pages, 3 eps figures, minor changes and
references adde
Cosmology in the Universe with distance dependent Lorentz-violating bakground
We consider a cosmological setup with the inflaton field in the presence of a
redshift dependent Lorentz-violating time-like background to address the
inflationary regime and other phases of the Universe. We also show that the
regime of dark energy at large distances (low redshifts) is essentially
dominated by the presence of the Lorentz-violating background.Comment: 8 pages, no figure, Latex, to appear in AHE
Scaffolding MATLAB and octave software comprehension through visualization
Multiple view interactive environments (MVIEs) provide visual resources to support the comprehension of a specific domain dataset. For any domain, different views can be selected and configured in a real time fashion to be better adjusted to the user needs. This paper focuses on the use of a MVIE called OctMiner to support the comprehension of MATLAB and GNU/Octave programs. The authors conducted a case study to characterize the use of OctMiner in the context of comprehension activities. Results provide preliminary evidence of the effectiveness of OctMiner to support the comprehension of programs written in MATLAB and Octave.info:eu-repo/semantics/acceptedVersio
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