6,078 research outputs found
FCNC in the minimal 3-3-1 model revisited
We show that in the minimal 3-3-1 model the flavor changing neutral currents
(FCNCs) do not impose necessarily strong constraints on the mass of the
of the model if we also consider the neutral scalar contributions to
such processes, like the neutral mesons mass difference and rare semileptonic
decays. We first obtain numerical values for all the mixing matrices of the
model i.e., the unitary matrices that rotate the left- and right-handed quarks
in each charge sector which give the correct mass of all the quarks and the CKM
mixing matrix. Then, we find that there is a range of parameters in which the
neutral scalar contributions to these processes may interfere with those of the
, implying this vector boson may be lighter than it has been thought.Comment: Extended version including the effect of a pseudoscalar. 37 pags. and
12 figures. New references added. Version matches the published versio
Complex Scalar DM in a B-L Model
In this work, we implement a complex scalar Dark Matter (DM) candidate in a
gauge extension of the Standard Model. The model contains three
right handed neutrinos with different quantum numbers and a rich scalar sector,
with extra doublets and singlets. In principle, these extra scalars can have
VEVs ( and for the extra doublets and singlets,
respectively) belonging to different energy scales. In the context of
, which allows to obtain naturally
light active neutrino masses and mixing compatible with neutrino experiments,
the DM candidate arises by imposing a symmetry on a given complex
singlet, , in order to make it stable. After doing a study of the
scalar potential and the gauge sector, we obtain all the DM dominant processes
concerning the relic abundance and direct detection. Then, for a representative
set of parameters, we found that a complex DM with mass around GeV, for
example, is compatible with the current experimental constraints without
resorting to resonances. However, additional compatible solutions with heavier
masses can be found in vicinities of resonances. Finally, we address the issue
of having a light CP-odd scalar in the model showing that it is safe concerning
the Higgs and the boson invisible decay widths, and also the energy
loss in stars astrophysical constraints.Comment: 20 pages, 3 figure
Quantum interference oscillations of the superparamagnetic blocking in an Fe8 molecular nanomagnet
We show that the dynamic magnetic susceptibility and the superparamagnetic
blocking temperature of an Fe8 single molecule magnet oscillate as a function
of the magnetic field Hx applied along its hard magnetic axis. These
oscillations are associated with quantum interferences, tuned by Hx, between
different spin tunneling paths linking two excited magnetic states. The
oscillation period is determined by the quantum mixing between the ground S=10
and excited multiplets. These experiments enable us to quantify such mixing. We
find that the weight of excited multiplets in the magnetic ground state of Fe8
amounts to approximately 11.6%.Comment: Accepted in Phys. Rev. Let
Natural PQ symmetry in the 3-3-1 model with a minimal scalar sector
In the framework of a 3-3-1 model with a minimal scalar sector we make a
detailed study concerning the implementation of the PQ symmetry in order to
solve the strong CP problem. For the original version of the model, with only
two scalar triplets, we show that the entire Lagrangian is invariant under a
PQ-like symmetry but no axion is produced since an U(1) subgroup remains
unbroken. Although in this case the strong CP problem can still be solved, the
solution is largely disfavored since three quark states are left massless to
all orders in perturbation theory. The addition of a third scalar triplet
removes the massless quark states but the resulting axion is visible. In order
to become realistic the model must be extended to account for massive quarks
and invisible axion. We show that the addition of a scalar singlet together
with a Z_N discrete gauge symmetry can successfully accomplish these tasks and
protect the axion field against quantum gravitational effects. To make sure
that the protecting discrete gauge symmetry is anomaly free we use a discrete
version of the Green-Schwarz mechanism.Comment: 18 pages, 1 figure, 3 table
Gravitational waves from the Papaloizou-Pringle instability in black hole-torus systems
Black hole (BH)--torus systems are promising candidates for the central
engine of gamma-ray bursts (GRBs), and also possible outcomes of the collapse
of supermassive stars to supermassive black holes (SMBHs). By three-dimensional
general relativistic numerical simulations, we show that an
nonaxisymmetric instability grows for a wide range of self-gravitating tori
orbiting BHs. The resulting nonaxisymmetric structure persists for a timescale
much longer than the dynamical one, becoming a strong emitter of large
amplitude, quasiperiodic gravitational waves. Our results indicate that both,
the central engine of GRBs and newly formed SMBHs, can be strong gravitational
wave sources observable by forthcoming ground-based and spacecraft detectors.Comment: 4 pages, 4 figure, to be published in PR
Towards an Unsupervised Speaking Style Voice Building Framework:Multi-Style Speaker Diarization
When are entrepreneurs more environmentally oriented? An analysis of stakeholders' pressures at different stages of evolution of the venture
Entrepreneurs are subjected to increased institutional pressures that encourage them to include environmental issues in their overall business objectives. Despite this, entrepreneurs do not always place the same importance on environmental issues in the overall objectives, but some are more environmentally oriented than others. We contend that these differences are explained by two factors: the stage of evolution of the venture and the intensity of coercive and normative environmental pressures on entrepreneurs. Using a sample of 9781 entrepreneurs from 27 countries, our research shows that entrepreneurs are more environmentally oriented (1) in early stages of evolution, (2) in countries with high coercive pressures, and (3) in countries with high normative pressures. Additionally, our results indicate that the differences in the environmental orientation in the early and late stages are reduced in countries with high normative pressures and that these differences are not influenced by the intensity of coercive pressures
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