30,550 research outputs found
Gauge Theories with Lorentz-Symmetry Violation by Symplectic Projector Method
The violation of Lorentz symmetry is studied from the point of view of a
canonical formulation. We make the usual analysis on the constraints structure
of the Carroll-Field-Jackiw model. In this context we derive the equations of
motion for the physical variables and check out the dispersion relations
obtained from them. Therefore, by the analysis using Symplectic Projector
Method (SPM), we can check the results about this type of Lorentz breaking with
those in the recent literature: in this sense we can confirm that the
configuration of space-like is stable, and the time-like
carry tachionic modes.Comment: 7 pages and no figure
Cosmological scenarios from multiquintessence
In this work we derive and analyse cosmological scenarios coming from
multi-component scalar field models. We consider a direct sum of a sine-Gordon
with a Z2 model, and also a combination of those with a BNRT model. Moreover,
we work with a modified version of the BNRT model, which breaks the Z2 x Z2
symmetry of the original BNRT potential, coupled with the sine-Gordon and with
the standard Z2 models. We show that our approach can be straightforwardly
elevated to fields. All the computations are made analytically and some
parameters restriction is put forward in order to get in touch with complete
and realistic cosmological scenarios
Activity Recognition based on a Magnitude-Orientation Stream Network
The temporal component of videos provides an important clue for activity
recognition, as a number of activities can be reliably recognized based on the
motion information. In view of that, this work proposes a novel temporal stream
for two-stream convolutional networks based on images computed from the optical
flow magnitude and orientation, named Magnitude-Orientation Stream (MOS), to
learn the motion in a better and richer manner. Our method applies simple
nonlinear transformations on the vertical and horizontal components of the
optical flow to generate input images for the temporal stream. Experimental
results, carried on two well-known datasets (HMDB51 and UCF101), demonstrate
that using our proposed temporal stream as input to existing neural network
architectures can improve their performance for activity recognition. Results
demonstrate that our temporal stream provides complementary information able to
improve the classical two-stream methods, indicating the suitability of our
approach to be used as a temporal video representation.Comment: 8 pages, SIBGRAPI 201
On the Temperley-Lieb reflection matrices
This work concerns the boundary integrability of the spin-s
Temperley-Lieb model. A systematic computation method is
used to constructed the solutions of the boundary Yang-Baxter equations. For
half-integer, a general free parameter solution is presented.
It turns that for integer, the general solution has free
parameters. Moreover, some particular solutions are discussed.Comment: LaTex 17 page
Constraining the redshift evolution of the Cosmic Microwave Background black-body temperature with PLANCK data
We constrain the deviation of adiabatic evolution of the Universe using the
data on the Cosmic Microwave Background (CMB) temperature anisotropies measured
by the {\it Planck} satellite and a sample of 481 X-ray selected clusters with
spectroscopically measured redshifts. To avoid antenna beam effects, we bring
all the maps to the same resolution. We use a CMB template to subtract the
cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ)
anisotropies; next, we remove galactic foreground emissions around each cluster
and we mask out all known point sources. If the CMB black-body temperature
scales with redshift as , we constrain deviations of
adiabatic evolution to be , consistent with the
temperature-redshift relation of the standard cosmological model. This result
could suffer from a potential bias associated with the CMB
template, that we quantify it to be and with the same
sign than the measured value of , but is free from those biases
associated with using TSZ selected clusters; it represents the best constraint
to date of the temperature-redshift relation of the Big-Bang model using only
CMB data, confirming previous results.Comment: ApJ, in press. Manuscript matches the accepted version: 10 pages, 7
figures, 3 table
Initial development of eucalyptus grandis (eucalyptus) in field benefited with biochar in Sinop / MT
Atomic Bose-Fermi mixtures in an optical lattice
A mixture of ultracold bosons and fermions placed in an optical lattice
constitutes a novel kind of quantum gas, and leads to phenomena, which so far
have been discussed neither in atomic physics, nor in condensed matter physics.
We discuss the phase diagram at low temperatures, and in the limit of strong
atom-atom interactions, and predict the existence of quantum phases that
involve pairing of fermions with one or more bosons, or, respectively, bosonic
holes. The resulting composite fermions may form, depending on the system
parameters, a normal Fermi liquid, a density wave, a superfluid liquid, or an
insulator with fermionic domains. We discuss the feasibility for observing such
phases in current experiments.Comment: 4 pages, 1 eps figure, misprints correcte
Avaliação de clones de mandioca (Manihot esculenta Crantz) em seis épocas de colheita.
A mandioca possui elevada importância social para os paÃses em desenvolvimento devido à sua ampla utilização. É uma das culturas mais importantes na alimentação humana, principalmente para a população de menor poder aquisitivo (LEONEL & CEREDA, 2002). Os carotenoides são importantes como fonte de vitamina A, pela sua ação antioxidante e por atuarem na prevenção de doenças crônicas não transmissÃveis. A carência da vitamina A pode causar a morte em milhares de crianças no mundo e constitui-se como um dos principais problemas nutricionais de populações de paÃses em desenvolvimento, incluindo o Brasil (AMANCIO & SILVA, 2012). O objetivo deste trabalho foi avaliar três clones de mandioca em seis épocas de colheita (6 a 11 meses), com relação aos teores de carotenoides totais, compostos cianogênicos, amilose e matéria seca
Moire bands in twisted double-layer graphene
A moire pattern is formed when two copies of a periodic pattern are overlaid
with a relative twist. We address the electronic structure of a twisted
two-layer graphene system, showing that in its continuum Dirac model the moire
pattern periodicity leads to moire Bloch bands. The two layers become more
strongly coupled and the Dirac velocity crosses zero several times as the twist
angle is reduced. For a discrete set of magic angles the velocity vanishes, the
lowest moire band flattens, and the Dirac-point density-of-states and the
counterflow conductivity are strongly enhanced
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