507 research outputs found
Graph Mining for Object Tracking in Videos
International audienceThis paper shows a concrete example of the use of graph mining for tracking objects in videos with moving cameras and without any contextual information on the objects to track. To make the mining algorithm efficient, we benefit from a video representation based on dy- namic (evolving through time) planar graphs. We then define a number of constraints to efficiently find our so-called spatio-temporal graph pat- terns. Those patterns are linked through an occurrences graph to allow us to tackle occlusion or graph features instability problems in the video. Experiments on synthetic and real videos show that our method is effec- tive and allows us to find relevant patterns for our tracking application
Horava-Lifshitz Dark Energy
We formulate Horava-Lifshitz cosmology with an additional scalar field that
leads to an effective dark energy sector. We find that, due to the inherited
features from the gravitational background, Horava-Lifshitz dark energy
naturally presents very interesting behaviors, possessing a varying
equation-of-state parameter, exhibiting phantom behavior and allowing for a
realization of the phantom divide crossing. In addition, Horava-Lifshitz dark
energy guarantees for a bounce at small scale factors and it may trigger the
turnaround at large scale factors, leading naturally to cyclic cosmology.Comment: 17 pages, no figures, version published at EJP
Validity of the Generalized Second Law of Thermodynamics of the Universe Bounded by the Event Horizon in Holographic Dark Energy Model
In this letter, we investigate the validity of the generalized second law of
thermodynamics of the universe bounded by the event horizon in the holographic
dark energy model. The universe is chosen to be homogeneous and isotropic and
the validity of the first law has been assumed here. The matter in the universe
is taken in the form of non-interacting two fluid system- one component is the
holographic dark energy model and the other component is in the form of dust.Comment: 8 page
Entropy and universality of Cardy-Verlinde formula in dark energy universe
We study the entropy of a FRW universe filled with dark energy (cosmological
constant, quintessence or phantom). For general or time-dependent equation of
state the entropy is expressed in terms of energy, Casimir energy,
and . The correspondent expression reminds one about 2d CFT entropy only for
conformal matter. At the same time, the cosmological Cardy-Verlinde formula
relating three typical FRW universe entropies remains to be universal for any
type of matter. The same conclusions hold in modified gravity which represents
gravitational alternative for dark energy and which contains terms growing at
low curvature. It is interesting that BHs in modified gravity are more entropic
than in Einstein gravity. Finally, some hydrodynamical examples testing new
shear viscosity bound, which is expected to be the consequence of the
holographic entropy bound, are presented for the early universe in the plasma
era and for the Kasner metric. It seems that the Kasner metric provides a
counterexample to the new shear viscosity bound.Comment: LaTeX file, 39 pages, references are adde
Renormalization Group Running of Lepton Mixing Parameters in See-Saw Models with Flavor Symmetry
We study the renormalization group running of the tri-bimaximal mixing
predicted by the two typical flavor models at leading order. Although the
textures of the mass matrices are completely different, the evolution of
neutrino mass and mixing parameters is found to display approximately the same
pattern. For both normal hierarchy and inverted hierarchy spectrum, the quantum
corrections to both atmospheric and reactor neutrino mixing angles are so small
that they can be neglected. The evolution of the solar mixing angle
depends on and neutrino mass spectrum, the deviation
from its tri-bimaximal value could be large. Taking into account the
renormalization group running effect, the neutrino spectrum is constrained by
experimental data on in addition to the self-consistency
conditions of the models, and the inverted hierarchy spectrum is disfavored for
large . The evolution of light-neutrino masses is approximately
described by a common scaling factor.Comment: 23 pages, 6figure
Universal procedure to cure future singularities of dark energy models
A systematic search for different viable models of the dark energy universe,
all of which give rise to finite-time, future singularities, is undertaken,
with the purpose to try to find a solution to this common problem. After some
work, a universal procedure to cure all future singularities is developed and
carefully tested with the help of explicit examples corresponding to each one
of the four different types of possible singularities, as classified in the
literature. The cases of a fluid with an equation of state which depends on
some parameter, of modified gravity non-minimally coupled to a matter
Lagrangian, of non-local gravity, and of isotropic turbulence in a dark fluid
universe theory are investigated in detail
Quantization and Compressive Sensing
Quantization is an essential step in digitizing signals, and, therefore, an
indispensable component of any modern acquisition system. This book chapter
explores the interaction of quantization and compressive sensing and examines
practical quantization strategies for compressive acquisition systems.
Specifically, we first provide a brief overview of quantization and examine
fundamental performance bounds applicable to any quantization approach. Next,
we consider several forms of scalar quantizers, namely uniform, non-uniform,
and 1-bit. We provide performance bounds and fundamental analysis, as well as
practical quantizer designs and reconstruction algorithms that account for
quantization. Furthermore, we provide an overview of Sigma-Delta
() quantization in the compressed sensing context, and also
discuss implementation issues, recovery algorithms and performance bounds. As
we demonstrate, proper accounting for quantization and careful quantizer design
has significant impact in the performance of a compressive acquisition system.Comment: 35 pages, 20 figures, to appear in Springer book "Compressed Sensing
and Its Applications", 201
Generalized Chaplygin gas model: Cosmological consequences and statefinder diagnosis
The generalized Chaplygin gas (GCG) model in spatially flat universe is
investigated. The cosmological consequences led by GCG model including the
evolution of EoS parameter, deceleration parameter and dimensionless Hubble
parameter are calculated. We show that the GCG model behaves as a general
quintessence model. The GCG model can also represent the pressureless CDM model
at the early time and cosmological constant model at the late time. The
dependency of transition from decelerated expansion to accelerated expansion on
the parameters of model is investigated. The statefinder parameters and
in this model are derived and the evolutionary trajectories in plane are
plotted. Finally, based on current observational data, we plot the evolutionary
trajectories in and planes for best fit values of the parameters of
GCG model. It has been shown that although, there are similarities between GCG
model and other forms of chaplygin gas in statefinder plane, but the distance
of this model from the CDM fixed point in diagram is shorter
compare with standard chaplygin gas model.Comment: 10 pages, 5 figures, accepted in Astrophys Space Sci. (2011
The 3-3-1 model with S_4 flavor symmetry
We construct a 3-3-1 model based on family symmetry S_4 responsible for the
neutrino and quark masses. The tribimaximal neutrino mixing and the diagonal
quark mixing have been obtained. The new lepton charge \mathcal{L} related to
the ordinary lepton charge L and a SU(3) charge by L=2/\sqrt{3} T_8+\mathcal{L}
and the lepton parity P_l=(-)^L known as a residual symmetry of L have been
introduced which provide insights in this kind of model. The expected vacuum
alignments resulting in potential minimization can origin from appropriate
violation terms of S_4 and \mathcal{L}. The smallness of seesaw contributions
can be explained from the existence of such terms too. If P_l is not broken by
the vacuum values of the scalar fields, there is no mixing between the exotic
and the ordinary quarks at the tree level.Comment: 20 pages, revised versio
Unifying inflation with dark energy in modified F(R) Horava-Lifshitz gravity
We study FRW cosmology for a non-linear modified F(R) Horava-Lifshitz gravity
which has a viable convenient counterpart. A unified description of early-time
inflation and late-time acceleration is possible in this theory, but the
cosmological dynamic details are generically different from the ones of the
convenient viable F(R) model. Remarkably, for some specific choice of
parameters they do coincide. The emergence of finite-time future singularities
is investigated in detail. It is shown that these singularities can be cured by
adding an extra, higher-derivative term, which turns out to be qualitatively
different when compared with the corresponding one of the convenient F(R)
theory.Comment: LaTeX 12 pages, typos are correcte
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