1,180 research outputs found
Gravity localization on hybrid branes
This work deals with gravity localization on codimension-1 brane worlds
engendered by compacton-like kinks, the so-called hybrid branes. In such
scenarios, the thin brane behaviour is manifested when the extra dimension is
outside the compact domain, where the energy density is non-trivial, instead of
asymptotically as in the usual thick brane models. The zero mode is trapped in
the brane, as required. The massive modes, although are not localized in the
brane, have important phenomenological implications such as corrections to the
Newton's law. We study such corrections in the usual thick domain wall and in
the hybrid brane scenarios. By means of suitable numerical methods, we attain
the mass spectrum for the graviton and the corresponding wavefunctions. The
spectra possess the usual linearly increasing behaviour from the Kaluza-Klein
theories. Further, we show that the 4D gravitational force is slightly
increased at short distances. The first eigenstate contributes highly for the
correction to the Newton's law. The subsequent normalized solutions have
diminishing contributions. Moreover, we find out that the phenomenology of the
hybrid brane is not different from the usual thick domain wall. The use of
numerical techniques for solving the equations of the massive modes is useful
for matching possible phenomenological measurements in the gravitational law as
a probe to warped extra dimensions.Comment: 15 pages, 11 figure
Transiting Disintegrating Planetary Debris around WD 1145+017
More than a decade after astronomers realized that disrupted planetary
material likely pollutes the surfaces of many white dwarf stars, the discovery
of transiting debris orbiting the white dwarf WD 1145+017 has opened the door
to new explorations of this process. We describe the observational evidence for
transiting planetary material and the current theoretical understanding (and in
some cases lack thereof) of the phenomenon.Comment: Invited review chapter. Accepted March 23, 2017 and published October
7, 2017 in the Handbook of Exoplanets. 15 pages, 10 figure
Extrasolar planetary dynamics with a generalized planar Laplace-Lagrange secular theory
The dynamical evolution of nearly half of the known extrasolar planets in
multiple-planet systems may be dominated by secular perturbations. The commonly
high eccentricities of the planetary orbits calls into question the utility of
the traditional Laplace-Lagrange (LL) secular theory in analyses of the motion.
We analytically generalize this theory to fourth-order in the eccentricities,
compare the result with the second-order theory and octupole-level theory, and
apply these theories to the likely secularly-dominated HD 12661, HD 168443, HD
38529 and Ups And multi-planet systems. The fourth-order scheme yields a
multiply-branched criterion for maintaining apsidal libration, and implies that
the apsidal rate of a small body is a function of its initial eccentricity,
dependencies which are absent from the traditional theory. Numerical results
indicate that the primary difference the second and fourth-order theories
reveal is an alteration in secular periodicities, and to a smaller extent
amplitudes of the planetary eccentricity variation. Comparison with numerical
integrations indicates that the improvement afforded by the fourth-order theory
over the second-order theory sometimes dwarfs the improvement needed to
reproduce the actual dynamical evolution. We conclude that LL secular theory,
to any order, generally represents a poor barometer for predicting secular
dynamics in extrasolar planetary systems, but does embody a useful tool for
extracting an accurate long-term dynamical description of systems with small
bodies and/or near-circular orbits.Comment: 14 pages, 12 figures, 1 table, accepted for publication in Ap
Manejo correto da ordenha e qualidade do leite.
Muitas vezes o produtor se questiona quais as vantagens de adotar duas ou três ordenhas diárias. A resposta para esta pergunta tem que considerar uma série de fatores, tais como o custo da mão de obra, custos adicionais conseqüentes da realização de uma terceira ordenha (luz, material de limpeza, etc.), incremento na produção de leite obtido e o valor recebido pelo leite.bitstream/item/55815/1/CR27-02.pd
Dynamical mass and multiplicity constraints on co-orbital bodies around stars
Objects transiting near or within the disruption radius of both main sequence (e.g. KOI 1843) and white dwarf (WD 1145+017) stars are now known. Upon fragmentation or disintegration, these planets or asteroids may produce co-orbital configurations of nearly equal-mass objects. However, as evidenced by the co-orbital objects detected by transit photometry in the WD 1145+017 system, these bodies are largely unconstrained in size, mass, and total number (multiplicity). Motivated by potential future similar discoveries, we perform N-body simulations to demonstrate if and how debris masses and multiplicity may be bounded due to second-to-minute deviations and the resulting accumulated phase shifts in the osculating orbital period amongst multiple co-orbital equal point masses. We establish robust lower and upper mass bounds as a function of orbital period deviation, but find the constraints on multiplicity to be weak. We also quantify the fuzzy instability boundary, and show that mutual collisions occur in less than 5%, 10% and 20% of our simulations for masses of 10^{21}, 10^{22} and 10^{23} kg. Our results may provide useful initial rough constraints on other stellar systems with multiple co-orbital bodies
Strangelet dwarfs
If the surface tension of quark matter is low enough, quark matter is not
self bound. At sufficiently low pressure and temperature, it will take the form
of a crystal of positively charged strangelets in a neutralizing background of
electrons. In this case there will exist, in addition to the usual family of
strange stars, a family of low-mass large-radius objects analogous to white
dwarfs, which we call "strangelet dwarfs". Using a generic parametrization of
the equation of state of quark matter, we calculate the mass-radius
relationship of these objects.Comment: 10 pages, LaTeX, added discussion of CFL phase and strangelet
pollution, version to appear in journal. arXiv admin note: text overlap with
arXiv:0808.067
Diabetic Foot Ulcers Classification using a fine-tuned CNNs Ensemble
Diabetic Foot Ulcers (DFU) are lesions in the foot region caused by diabetes mellitus. It is essential to define the appropriate treatment in the early stages of the disease once late treatment may result in amputation. This article proposes an ensemble approach composed of five modified convolutional neural networks (CNNs) - VGG-16, VGG-19, Resnet50, InceptionV3, and Densenet-201 - to classify DFU images. To define the parameters, we fine-tuned the CNNs, evaluated different configurations of fully connected layers, and used batch normalization and dropout operations. The modified CNNs were well suited to the problem; however, we observed that the union of the five CNNs significantly increased the success rates. We performed tests using 8,250 images with different resolution, contrast, color, and texture characteristics and included data augmentation operations to expand the training dataset. 5-fold cross-validation led to an average accuracy of 95.04%, resulting in a Kappa index greater than 91.85%, considered Excellent
Formation, Survival, and Detectability of Planets Beyond 100 AU
Direct imaging searches have begun to detect planetary and brown dwarf
companions and to place constraints on the presence of giant planets at large
separations from their host star. This work helps to motivate such planet
searches by predicting a population of young giant planets that could be
detectable by direct imaging campaigns. Both the classical core accretion and
the gravitational instability model for planet formation are hard-pressed to
form long-period planets in situ. Here, we show that dynamical instabilities
among planetary systems that originally formed multiple giant planets much
closer to the host star could produce a population of giant planets at large
(~100 AU - 100000 AU) separations. We estimate the limits within which these
planets may survive, quantify the efficiency of gravitational scattering into
both stable and unstable wide orbits, and demonstrate that population analyses
must take into account the age of the system. We predict that planet scattering
creates a population of detectable giant planets on wide orbits that decreases
in number on timescales of ~10 Myr. We demonstrate that several members of such
populations should be detectable with current technology, quantify the
prospects for future instruments, and suggest how they could place interesting
constraints on planet formation models.Comment: 13 pages (emulateapj format), 10 figures, accepted for publication in
Ap
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