86,225 research outputs found
On the anomalous mass defect of strange stars in the Field Correlator Method
We investigate general aspects of the mass defects of strange stars in the
context of the Field Correlator Method, without magnetic field. The main
parameters of the model that enter the corresponding nonperturbative equation
of state of the quark gluon plasma are the gluon condensate and the large
distance static potential . We calculate mass defects of
stellar configurations in the central density range . In
general, the mass defects are strongly dependent on the model parameters. For a
large range of values of and , we obtain anomalous mass defects with
magnitudes around erg\,, of the same order of the observed energies
of gamma-ray bursts and neutrino emissions in SN1987A, and of the theoretically
predicted energies of the quark-novae explosions.Comment: 24 pages, 6 figure
Strange stars properties calculated in the framework of the Field Correlator Method
We calculate the strange star properties in the framework of the Field
Correlator Method. We find that for the values of the gluon condensate
and , which give a critical
temperature at , the sequences of strange
stars are compatible with some of the semi-empirical mass-radius relations and
data obtained from astrophysical observations.Comment: 26 pages, 10 figure
Second harmonic spectroscopy to optically detect valley polarization in 2D materials
Valley polarization (VP), an induced imbalance in the populations of a
multi-valley electronic system, allows emission of second harmonic (SH) light
even in centrosymmetric crystals such as graphene. Whereas in systems such as
MoS or BN this adds to their intrinsic quadratic response, SH
generation in a multi-valley inversion-symmetric crystal can provide a direct
measure of valley polarization. By computing the nonlinear response and
characterizing theoretically the respective SH as a function of polarization,
temperature, electron density, and degree of VP, we demonstrate the possibility
of disentangling and individually quantifying the intrinsic and valley
contributions to the SH. A specific experimental setup is proposed to obtain
direct quantitative information about the degree of VP and allow its remote
mapping. This approach could prove useful for direct, contactless, real-space
monitoring of valley injection and other applications of valley transport and
valleytronics.Comment: Updating with published version, including typesetting corrections to
eqs 3 and 4; 7 pages, 5 figure
The whole mesh Deformation Model for 2D and 3D image segmentation
In this paper we present a novel approach for image segmentation using Active Nets and Active Volumes. Those solutions are based on the Deformable Models, with slight difference in the method for describing the shapes of interests - instead of using a contour or a surface they represented the segmented objects with a mesh structure, which allows to describe not only the surface of the objects but also to model their interiors. This is obtained by dividing the nodes of the mesh in two categories, namely internal and external ones, which will be responsible for two different tasks. In our new approach we propose to negate this separation and use only one type of nodes. Using that assumption we manage to significantly shorten the time of segmentation while maintaining its quality
PUBLIC INVESTMENT IN TRANSPORTATION INFRASTRUCTURES AND INDUSTRY PERFORMANCE IN PORTUGAL
The objective of this paper is to evaluate the effects at the industry level of public investment in transportation infrastructures in Portugal. The empirical results are based on VAR/ECM models for the Portuguese economy and for eighteen industries covering the whole spectrum of economic activity in the country. These models consider private-sector output, employment and investment as well as public investment. Empirical results at the aggregate level indicate that public investment has a positive effect on both private inputs as well as on private output and that it affects labor productivity positively. These aggregate results, however, hide a wide variety of industry-level effects. In absolute terms, the industries that benefit the most from public investment are Construction, Trade, Transportation, Finance, Real Estate, and Services. In turn, relative to their size, the industries that benefit the most are Mining, Non-Metal Products, Metal Products, Construction, Restaurants, Transportation, and Finance, and, therefore, public investment tends to shift the industry mix toward these industries. Accordingly, our empirical results suggest that although public investment has been a powerful instrument to enhance the long-term economic performance in Portugal it does so in a way that is rather unbalanced across industries.Infrastructures, Industry Performance, Portugal
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