28,808 research outputs found
Vacuum stability conditions of the economical 3-3-1 model from copositivity
By applying copositivity criterion to the scalar potential of the economical
model, we derive necessary and sufficient bounded-from-below conditions
at tree level. Although these are a large number of intricate inequalities for
the dimensionless parameters of the scalar potential, we present general
enlightening relations in this work. Additionally, we use constraints coming
from the minimization of the scalar potential by means of the orbit space
method, the positivity of the squared masses of the extra scalars, the Higgs
boson mass, the gauge boson mass and its mixing angle with the SM
boson in order to further restrict the parameter space of this model.Comment: 22 pages, 7 figures, added text and references. Matches published
versio
Interacting social processes on interconnected networks
We propose and study a model for the interplay between two different
dynamical processes --one for opinion formation and the other for decision
making-- on two interconnected networks and . The opinion dynamics on
network corresponds to that of the M-model, where the state of each agent
can take one of four possible values (), describing its level of
agreement on a given issue. The likelihood to become an extremist ()
or a moderate () is controlled by a reinforcement parameter .
The decision making dynamics on network is akin to that of the
Abrams-Strogatz model, where agents can be either in favor () or against
() the issue. The probability that an agent changes its state is
proportional to the fraction of neighbors that hold the opposite state raised
to a power . Starting from a polarized case scenario in which all agents
of network hold positive orientations while all agents of network have
a negative orientation, we explore the conditions under which one of the
dynamics prevails over the other, imposing its initial orientation. We find
that, for a given value of , the two-network system reaches a consensus
in the positive state (initial state of network ) when the reinforcement
overcomes a crossover value , while a negative consensus happens
for . In the phase space, the system displays a
transition at a critical threshold , from a coexistence of both
orientations for to a dominance of one orientation for
. We develop an analytical mean-field approach that gives an
insight into these regimes and shows that both dynamics are equivalent along
the crossover line .Comment: 25 pages, 6 figure
Coexistence of Pairing Tendencies and Ferromagnetism in a Doped Two-Orbital Hubbard Model on Two-Leg Ladders
Using the Density Matrix Renormalization Group and two-leg ladders, we
investigate an electronic two-orbital Hubbard model including plaquette
diagonal hopping amplitudes. Our goal is to search for regimes where charges
added to the undoped state form pairs, presumably a precursor of a
superconducting state.For the electronic density , i.e. the undoped
limit, our investigations show a robust antiferromagnetic ground
state, as in previous investigations. Doping away from and for large
values of the Hund coupling , a ferromagnetic region is found to be stable.
Moreover, when the interorbital on-site Hubbard repulsion is smaller than the
Hund coupling, i.e. for in the standard notation of multiorbital Hubbard
models, our results indicate the coexistence of pairing tendencies and
ferromagnetism close to . These results are compatible with previous
investigations using one dimensional systems. Although further research is
needed to clarify if the range of couplings used here is of relevance for real
materials, such as superconducting heavy fermions or pnictides, our theoretical
results address a possible mechanism for pairing that may be active in the
presence of short-range ferromagnetic fluctuations.Comment: 8 pages, 4 Fig
Thermodynamic modeling of phase separation in manganites
We present a phenomenological model based on the thermodynamics of the phase
separated state of manganites, accounting for its static and dynamic
properties. Through calorimetric measurements on LaPrCaMnO the low temperature free energies of the coexisting
ferromagnetic and charge ordered phases are evaluated. The phase separated
state is modeled by free energy densities uniformly spread over the sample
volume. The calculations contemplate the out of equilibrium features of the
coexisting phase regime, to allow a comparison between magnetic measurements
and the predictions of the model. A phase diagram including the static and
dynamic properties of the system is constructed, showing the existence of
blocked and unblocked regimes which are characteristics of the phase separated
state in manganites.Comment: 7 pages, 5 figures, Submitted to Phys. Rev.
On the \phi(1020)f_0(980) S-wave scattering and the Y(2175) resonance
We have studied the \phi(1020)f_0(980) S-wave scattering at energies around
threshold employing chiral Lagrangians coupled to vector mesons through minimal
coupling. The interaction kernel is obtained by considering the f_0(980) as a
K\bar{K} bound state. The Y(2175) resonance is generated in this approach by
the self-interactions between the \phi(1020) and the f_0(980) resonances. We
are able to describe the e^+e^-\to \phi(1020)f_0(980) recent scattering data to
test experimentally our scattering amplitudes, concluding that the Y(2175)
resonance has a large \phi(1020)f_0(980) meson-meson component.Comment: 20 pages, 8 figure
A PROPOSED METHODOLOGY TO EVALUATE SPECIFIC APPLICATIONS OF EXTENDED SURFACES IN INDUSTRIAL EQUIPMENT
The concept of Passive Cooling fits into a number of technological options involving constructive elements, whereby the heat exchange area of a surface being cooled by a surrounding fluid medium occurs. Thus, the increase in area results in an increase in the surface heat dissipation rate for the refrigerant, inferring only a single cost, i.e. the construction cost. Among the available technical possibilities, the use of extended surfaces, known as fins, stands out. The present work focuses on the use of fins on three very common electrical devices in the industrial environment, which present a great need for cooling.They are: three-phase transformer, frequency inverter and induction electric motor. The study is dedicated to a theoretical evaluation of the use of the fin profiles used in these equipments, since the manufacturers do not make their design data available to the public. Thus, a methodology was developed for this evaluation, including comparison of the results between the original profiles of these equipments with an alternative profile of similar design. Within the process of calculating the heat dissipation rates by the fins, the axial temperature distribution profiles were numerically determined using the Finite Difference discretization method, together with the Gauss-Seidel iterative method for the resolution of the discretized equations. The computational code was developed using MatLab® software. The results of the present work attested to the proper use of the original profiles employed by the manufacturers
Charged Current Neutrino Nucleus Interactions at Intermediate Energies
We have developed a model to describe the interactions of neutrinos with
nucleons and nuclei, focusing on the region of the quasielastic and Delta(1232)
peaks. We describe neutrino nucleon collisions with a fully relativistic
formalism which incorporates state-of-the-art parametrizations of the form
factors for both the nucleon and the N-Delta transition. The model has then
been extended to finite nuclei, taking into account nuclear effects such as
Fermi motion, Pauli blocking (both within the local density approximation),
nuclear binding and final state interactions. The in-medium modification of the
Delta resonance due to Pauli blocking and collisional broadening have also been
included. Final state interactions are implemented by means of the
Boltzmann-Uehling-Uhlenbeck (BUU) coupled-channel transport model. Results for
charged current inclusive cross sections and exclusive channels as pion
production and nucleon knockout are presented and discussed.Comment: 26 pages, 24 figures; v2: 2 figures and discussion added, version
accepted for publication in Phys. Rev.
Determining fundamental parameters from the chargino sector in Left-Right Supersymmetric models
Analytical expressions relating the fundamental parameters describing the
chargino sector in the context of the Left-Right Supersymmetric model are
constructed. A general complex extension of the real non-symmetric chargino
mass matrix including all possible CP-violating phases is considered. The
method used for such a effects is the projector formalism based on the explicit
knowledge of two unitary matrices diagonalizing the chargino mass matrix. Some
possible scenarios allowing us to extract analytical and numerical values for
the unknown parameters are considered. Moreover, an algorithm allowing us to
disentangle the fundamental parameters of the chargino sector, based on
possible measurements of some class of cross-section observables related to the
chargino pair production in annihilation processes, is described.
Some comparisons with the corresponding results in the context of the Minimal
Supersymmetric Standard Model are given.Comment: 48 pages, 13 figure
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