1,740 research outputs found
Asymmetrical bloch branes and the hierarchy problem
We investigate a two scalar fields split braneworld model which leads to a
possible approach to the hierarchy problem within the thick brane scenario. The
model exhibits a resulting asymmetric warp factor suitable for this purpose.
The solution is obtained by means of the orbit equation approach for a specific
value of one of the parameters. Besides, we analyze the model qualitative
behaviour for arbitrary parameters by inspecting the underlying dynamical
system defined by the equations which give rise to the braneworld model. We
finalize commenting on the metric fluctuation and stability issues.Comment: 8 pages, 7 figure
Assessment of Orchid Surfaces Using Top-Down Contact Angle Mapping
© 2013 IEEE. Top-down contact angle (CA) measurements are used to characterize the green leaves and purple flowers of both old and young the Cattleya warneri orchids. The top-down CA allows the characterization of large surfaces away from the leaf edge, avoiding traditional cutting required for side view CA measurement. This allows large area mapping without damaging leaves making the method amenable to fieldwork and useful in environmental diagnostics. Young leaves are found to be hydrophobic whilst old leaves become practically hydrophilic across their entirety, mostly as a result of continued exposure to changes in the environment over time. The flowers are hydrophobic because of their visual and tactile attractor function for pollinating animals and the self-cleaning of dirt and pathogens. Real-time measurement and mapping of CA of surfaces open a new tool to assess the long-term impact of plant aging, pollution, and more of organisms in the field. The method has clear applications elsewhere such as in industrial probing of surfaces and products
Quadratic Effective Action for QED in D=2,3 Dimensions
We calculate the effective action for Quantum Electrodynamics (QED) in D=2,3
dimensions at the quadratic approximation in the gauge fields. We analyse the
analytic structure of the corresponding nonlocal boson propagators
nonperturbatively in k/m. In two dimensions for any nonzero fermion mass, we
end up with one massless pole for the gauge boson . We also calculate in D=2
the effective potential between two static charges separated by a distance L
and find it to be a linearly increasing function of L in agreement with the
bosonized theory (massive Sine-Gordon model). In three dimensions we find
nonperturbatively in k/m one massive pole in the effective bosonic action
leading to screening. Fitting the numerical results we derive a simple
expression for the functional dependence of the boson mass upon the
dimensionless parameter e^{2}/m .Comment: 10 pages, 2 figure
Dark matter effects in modified teleparallel gravity
This work investigates dark matter (DM) effects in compact objects in
modified teleparallel gravity (MTG) in which a modification of Teleparallel
Equivalent to General Relativity is used. We applied a tetrad to the modified
field equations where a set of relations is found. The conservation equation
allows us to rewrite our Tolman-Oppenheimer-Volkoff equations with an effective
gravitational coupling constant. As input to these new equations, we use a
relativistic mean-field (RMF) model with dark matter content included, obtained
from a Lagrangian density with both, hadronic and dark particle degrees of
freedom, as well as the Higgs boson, used as a mediator in both sectors of the
theory. Through numerical calculations, we analyze the mass-radius diagrams
obtained from different parametrizations of the RMF-DM model, generated by
assuming different values of the dark particle Fermi momentum and running the
free parameter coming from the MTG. Our results show that it is possible for
the system simultaneously support more DM content, and be compatible with
recent astrophysical data provided by LIGO and Virgo Collaboration, as well as
by NASA's Neutron star Interior Composition Explorer (NICER).Comment: 8 pages, 2 figure
Field quantization in inhomogeneous anisotropic dielectrics with spatio-temporal dispersion
A quantum damped-polariton model is constructed for an inhomogeneous
anisotropic linear dielectric with arbitrary dispersion in space and time. The
model Hamiltonian is completely diagonalized by determining the creation and
annihilation operators for the fundamental polariton modes as specific linear
combinations of the basic dynamical variables. Explicit expressions are derived
for the time-dependent operators describing the electromagnetic field, the
dielectric polarization and the noise term in the latter. It is shown how to
identify bath variables that generate the dissipative dynamics of the medium.Comment: 24 page
Umidade do solo estimada por TDR em vertissolo e luvissolo na regiĂŁo da Campanha do RS.
CONGREGA URCAMP 2012
Skyrme Interaction and Nuclear Matter Constraints
This paper presents a detailed assessment of the ability of the 240 Skyrme
interaction parameter sets in the literature to satisfy a series of criteria
derived from macroscopic properties of nuclear matter in the vicinity of
nuclear saturation density at zero temperature and their density dependence,
derived by the liquid drop model, experiments with giant resonances and
heavy-ion collisions. The objective is to identify those parameterizations
which best satisfy the current understanding of the physics of nuclear matter
over a wide range of applications. Out of the 240 models, only 16 are shown to
satisfy all these constraints. Additional, more microscopic, constraints on
density dependence of the neutron and proton effective mass beta-equilibrium
matter, Landau parameters of symmetric and pure neutron nuclear matter, and
observational data on high- and low-mass cold neutron stars further reduce this
number to 5, a very small group of recommended Skyrme parameterizations to be
used in future applications of the Skyrme interaction of nuclear matter related
observables. Full information on partial fulfillment of individual constraints
by all Skyrme models considered is given. The results are discussed in terms of
the physical interpretation of the Skyrme interaction and the validity of its
use in mean-field models. Future work on application of the Skyrme forces,
selected on the basis of variables of nuclear matter, in Hartree-Fock
calculation of properties of finite nuclei, is outlined.Comment: 86 pages, 14 figure
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