41,762 research outputs found
Cosmology with minimal length uncertainty relations
We study the effects of the existence of a minimal observable length in the
phase space of classical and quantum de Sitter (dS) and Anti de Sitter (AdS)
cosmology. Since this length has been suggested in quantum gravity and string
theory, its effects in the early universe might be expected. Adopting the
existence of such a minimum length results in the Generalized Uncertainty
Principle (GUP), which is a deformed Heisenberg algebra between minisuperspace
variables and their momenta operators. We extend these deformed commutating
relations to the corresponding deformed Poisson algebra in the classical limit.
Using the resulting Poisson and Heisenberg relations, we then construct the
classical and quantum cosmology of dS and Ads models in a canonical framework.
We show that in classical dS cosmology this effect yields an inflationary
universe in which the rate of expansion is larger than the usual dS universe.
Also, for the AdS model it is shown that GUP might change the oscillatory
nature of the corresponding cosmology. We also study the effects of GUP in
quantized models through approximate analytical solutions of the Wheeler-DeWitt
(WD) equation, in the limit of small scale factor for the universe, and compare
the results with the ordinary quantum cosmology in each case.Comment: 11 pages, 4 figures, to appear in IJMP
Thermal analysis of rare earth electrolytic robots under high temperature environment
Rare earth electrolysis robot is an automatic equipment that can realize the process of crucible extraction and dumping of casting mold in electrolytic tank under high temperature and dusty environment. Based on ANSYS software and APDL language, the thermal-structural coupling simulation analysis of the rare earth electrolysis robot is carried out to construct the temperature distribution and thermal deformation model of the robot, and the thermal deformation error and connecting rod machining error are considered comprehensively to obtain the linkage length dimension error model, which provides some theoretical basis for the robot error compensation to improve the accuracy
Cyclic cosmology from Lagrange-multiplier modified gravity
We investigate cyclic and singularity-free evolutions in a universe governed
by Lagrange-multiplier modified gravity, either in scalar-field cosmology, as
well as in one. In the scalar case, cyclicity can be induced by a
suitably reconstructed simple potential, and the matter content of the universe
can be successfully incorporated. In the case of -gravity, cyclicity can
be induced by a suitable reconstructed second function of a very
simple form, however the matter evolution cannot be analytically handled.
Furthermore, we study the evolution of cosmological perturbations for the two
scenarios. For the scalar case the system possesses no wavelike modes due to a
dust-like sound speed, while for the case there exist an oscillation
mode of perturbations which indicates a dynamical degree of freedom. Both
scenarios allow for stable parameter spaces of cosmological perturbations
through the bouncing point.Comment: 8 pages, 3 figures, references added, accepted for publicatio
Bounce and cyclic cosmology in extended nonlinear massive gravity
We investigate non-singular bounce and cyclic cosmological evolutions in a
universe governed by the extended nonlinear massive gravity, in which the
graviton mass is promoted to a scalar-field potential. The extra freedom of the
theory can lead to certain energy conditions violations and drive cyclicity
with two different mechanisms: either with a suitably chosen scalar-field
potential under a given Stuckelberg-scalar function, or with a suitably chosen
Stuckelberg-scalar function under a given scalar-field potential. Our analysis
shows that extended nonlinear massive gravity can alter significantly the
evolution of the universe at both early and late times.Comment: 20 pages, 5 figures, version published at JCA
Long-Term Human Video Generation of Multiple Futures Using Poses
Predicting future human behavior from an input human video is a useful task
for applications such as autonomous driving and robotics. While most previous
works predict a single future, multiple futures with different behavior can
potentially occur. Moreover, if the predicted future is too short (e.g., less
than one second), it may not be fully usable by a human or other systems. In
this paper, we propose a novel method for future human pose prediction capable
of predicting multiple long-term futures. This makes the predictions more
suitable for real applications. Also, from the input video and the predicted
human behavior, we generate future videos. First, from an input human video, we
generate sequences of future human poses (i.e., the image coordinates of their
body-joints) via adversarial learning. Adversarial learning suffers from mode
collapse, which makes it difficult to generate a variety of multiple poses. We
solve this problem by utilizing two additional inputs to the generator to make
the outputs diverse, namely, a latent code (to reflect various behaviors) and
an attraction point (to reflect various trajectories). In addition, we generate
long-term future human poses using a novel approach based on unidimensional
convolutional neural networks. Last, we generate an output video based on the
generated poses for visualization. We evaluate the generated future poses and
videos using three criteria (i.e., realism, diversity and accuracy), and show
that our proposed method outperforms other state-of-the-art works
OM Theory and V-duality
We show that the (M5, M2, M2, MW) bound state solution of eleven
dimensional supergravity recently constructed in hep-th/0009147 is related to
the (M5, M2) bound state one by a finite Lorentz boost along a M5-brane
direction perpendicular to the M2-brane. Given the (M5, M2) bound state as a
defining system for OM theory and the above relation between this system and
the (M5, M2, M2', MW) bound state, we test the recently proposed V-duality
conjecture in OM theory. Insisting to have a decoupled OM theory, we find that
the allowed Lorentz boost has to be infinitesimally small, therefore resulting
in a family of OM theories related by Galilean boosts. We argue that such
related OM theories are equivalent to each other. In other words, V-duality
holds for OM theory as well. Upon compactification on either an electric or a
`magnetic' circle (plus T-dualities as well), the V-duality for OM theory gives
the known one for either noncommutative open string theories or noncommutative
Yang-Mills theories. This further implies that V-duality holds in general for
the little m-theory without gravity.Comment: 17 pages, typos corrected and references adde
Numerical simulation of solid tumor blood perfusion and drug delivery during the “vascular normalization window” with antiangiogenic therapy
This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Hindawi PublishingTo investigate the influence of vascular normalization on solid tumor blood perfusion and drug delivery, we used the generated blood vessel network for simulations. Considering the hemodynamic parameters changing after antiangiogenic therapies, the results show that the interstitial fluid pressure (IFP) in tumor tissue domain decreases while the pressure gradient increases during the normalization window. The decreased IFP results in more efficient delivery of conventional drugs to the targeted cancer cells. The outcome of therapies will improve if the antiangiogenic therapies and conventional therapies are carefully scheduled
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