38,860 research outputs found
Posing 3D Models from Drawing
Inferring the 3D pose of a character from a drawing is a complex and under-constrained problem. Solving it may help automate various parts of an animation production pipeline such as pre-visualisation. In this paper, a novel way of inferring the 3D pose from a monocular 2D sketch is proposed. The proposed method does not make any external assumptions about the model, allowing it to be used on different types of characters. The inference of the 3D pose is formulated as an optimisation problem and a parallel variation of the Particle Swarm Optimisation algorithm called PARAC-LOAPSO is utilised for searching the minimum. Testing in isolation as well as part of a larger scene, the presented method is evaluated by posing a lamp, a horse and a human character. The results show that this method is robust, highly scalable and is able to be extended to various types of models
Exact Algorithms for Maximum Independent Set
We show that the maximum independent set problem (MIS) on an -vertex graph
can be solved in time and polynomial space, which even is
faster than Robson's -time exponential-space algorithm
published in 1986. We also obtain improved algorithms for MIS in graphs with
maximum degree 6 and 7, which run in time of and
, respectively. Our algorithms are obtained by using fast
algorithms for MIS in low-degree graphs in a hierarchical way and making a
careful analyses on the structure of bounded-degree graphs
The Family SU(2)_l x SU(2)_h x U(1) Model
We consider extension of the standard model where the first two families of quarks and leptons transform according to
the group and the third family according to the group. In
this approach, the largeness of top-quark mass is associated with the large
vacuum expectation value of the corresponding Higgs field. The model predicts
almost degenerate heavy and bosons with non-universal couplings, and
extra Higgs bosons. We present in detail the symmetry breaking mechanism, and
carry out the subsequent phenomenology of the gauge sector. We compare the
model with electroweak precision data, and conclude that the extra gauge bosons
and the Higgs bosons whose masses lie in the TeV range, can be discovered at
the LHC.Comment: Latex 18 pages. No figure. Some references added. Version appeared in
PR
Factorization and Unitarity in Superstring Theory
The overall coefficient of the two-loop 4-particle amplitude in superstring
theory is determined by making use of the factorization and unitarity. To
accomplish this we computed in detail all the relevant tree and one-loop
amplitudes involved and determined their overall coefficients in a consistent
way.Comment: LaTex file, 19 pages, 4 figures; v2, minor corrections and figures
corrected; v3, minor corrections with the English, to be published in JHE
Charmless decays and new physics effects in the mSUGRA model
By employing the QCD factorization approach, we calculate the new physics
contributions to the branching radios of the two-body charmless and
decays in the framework of the minimal supergravity (mSUGRA) model.
we choose three typical sets of the mSUGRA input parameters in which the Wilson
coefficient can be either SM-like (the case A and C) or has
a flipped-sign (the case B). We found numerically that (a) the SUSY
contributions are always very small for both case A and C; (b) for those
tree-dominated decays, the SUSY contributions in case B are also very small;
(c) for those QCD penguin-dominated decay modes, the SUSY contributions in case
B can be significant, and can provide an enhancement about to
the branching ratios of and decays, but a
reduction about to decays; and (d) the
large SUSY contributions in the case B may be masked by the large theoretical
errors dominated by the uncertainty from our ignorance of calculating the
annihilation contributions in the QCD factorization approach.Comment: 34 pages, 8 PS figures, this is the correct version
Driving light pulses with light in two-level media
A two-level medium, described by the Maxwell-Bloch (MB) system, is engraved
by establishing a standing cavity wave with a linearly polarized
electromagnetic field that drives the medium on both ends. A light pulse,
polarized along the other direction, then scatters the medium and couples to
the cavity standing wave by means of the population inversion density
variations. We demonstrate that control of the applied amplitudes of the
grating field allows to stop the light pulse and to make it move backward
(eventually to drive it freely). A simplified limit model of the MB system with
variable boundary driving is obtained as a discrete nonlinear Schroedinger
equation with tunable external potential. It reproduces qualitatively the
dynamics of the driven light pulse
Factorization of the Two Loop Four-Particle Amplitude in Superstring Theory Revisited
We study in detail the factorization of the newly obtained two-loop
four-particle amplitude in superstring theory. In particular some missing
factors from the scalar correlators are obtained correctly, in comparing with a
previous study of the factorization in two-loop superstring theory. Some
details for the calculation of the factorization of the kinematic factor are
also presented.Comment: 11 pages, 1 figure; v2, minor corrections and references update
Orbital order and ferrimagnetic properties of the new compound
By means of the LSDA+U method and the Green function method, we investigate
the electronic and magnetic properties of the new material of
SrCaReCuO. Our LSDA+U calculation shows that this system is
an insulator with a net magnetic moment of 1.01 /f.u., which is in
good agreement with the experiment. Magnetic moments are mainly located at Cu
atoms, and the magnetic moments of neighboring Cu sites align anti-parallel. It
is the non-magnetic Re atoms that induce an orbital order of electrons of
Cu atoms, which is responsible for the strong exchange interaction and the high
magnetic transition temperature. Based on the LSDA+U results, we introduce an
effective model for the spin degrees of freedom, and investigate the
finite-temperature properties by the Green function method. The obtained
results are consistent with the experimental results, indicating that the
spin-alternating Heisenberg model is suitable for this compound.Comment: 8 pages and 5 figur
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