22,782 research outputs found
Quantum Theory at Planck Scale, Limiting Values, Deformed Gravity and Dark Energy Problem
Within a theory of the existing fundamental length on the order of Planck's a
high-energy deformation of the General Relativity for the space with horizon
has been constructed. On this basis, Markov's work of the early eighties of the
last century has been given a new interpretation to show that the heuristic
model considered by him may be placed on a fundamental footing. The obtained
results have been applied to solving of the dark energy problem, making it
possible to frame the following hypothesis: a dynamic cosmological term is a
measure of deviation from a thermodynamic identity (the first law of
thermodynamics) of the high-energy (Planck's) deformation of Einstein equations
for horizon spaces in their thermodynamic interpretation.Comment: 30 pages, Latex. arXiv admin note: substantial text overlap with
arXiv:1003.4523, arXiv:0911.5597, arXiv:1006.497
Flux and Instanton Effects in Local F-theory Models and Hierarchical Fermion Masses
We study the deformation induced by fluxes and instanton effects on Yukawa
couplings involving 7-brane intersections in local F-theory constructions. In
the absence of non-perturbative effects, holomorphic Yukawa couplings do not
depend on open string fluxes. On the other hand instanton effects (or gaugino
condensation on distant 7-branes) do induce corrections to the Yukawas. The
leading order effect may also be captured by the presence of closed string
(1,2) IASD fluxes, which give rise to a non-commutative structure. We check
that even in the presence of these non-perturbative effects the holomorphic
Yukawas remain independent of magnetic fluxes. Although fermion mass
hierarchies may be obtained from these non-perturbative effects, they would
give identical Yukawa couplings for D-quark and Lepton masses in SU(5) F-theory
GUT's, in contradiction with experiment. We point out that this problem may be
solved by appropriately normalizing the wavefunctions. We show in a simple toy
model how the presence of hypercharge flux may then be responsible for the
difference between D-quarks and Lepton masses in local SU(5) GUT's.Comment: 84 pages, 1 figure. v2: minor corrections and references adde
3D performance capture for facial animation
This work describes how a photogrammetry based 3D capture system can be used as an input device for animation. The 3D Dynamic Capture System is used to capture the motion of a human face, which is extracted from a sequence of 3D models captured at TV frame rate. Initially the positions of a set of landmarks on the face are extracted. These landmarks are then used to provide motion data in two different ways. First, a high level description of the movements is extracted, and these can be used as input to a procedural animation package (i.e. CreaToon). Second the landmarks can be used as registration points for a conformation process where the model to be animated is modified to match the captured model. This approach gives a new sequence of models, which have the structure of the drawn model but the movement of the captured sequence
Scalable Estimation of Precision Maps in a MapReduce Framework
This paper presents a large-scale strip adjustment method for LiDAR mobile
mapping data, yielding highly precise maps. It uses several concepts to achieve
scalability. First, an efficient graph-based pre-segmentation is used, which
directly operates on LiDAR scan strip data, rather than on point clouds.
Second, observation equations are obtained from a dense matching, which is
formulated in terms of an estimation of a latent map. As a result of this
formulation, the number of observation equations is not quadratic, but rather
linear in the number of scan strips. Third, the dynamic Bayes network, which
results from all observation and condition equations, is partitioned into two
sub-networks. Consequently, the estimation matrices for all position and
orientation corrections are linear instead of quadratic in the number of
unknowns and can be solved very efficiently using an alternating least squares
approach. It is shown how this approach can be mapped to a standard key/value
MapReduce implementation, where each of the processing nodes operates
independently on small chunks of data, leading to essentially linear
scalability. Results are demonstrated for a dataset of one billion measured
LiDAR points and 278,000 unknowns, leading to maps with a precision of a few
millimeters.Comment: ACM SIGSPATIAL'16, October 31-November 03, 2016, Burlingame, CA, US
Non-linear fire-resistance analysis of reinforced concrete beams
The non-linear structural analysis of reinforced concrete beams in fire consists of three separate steps: (i) The estimation of the rise of surrounding air temperature due to fire; (ii) the determination of the distribution of the temperature within the beam during fire; (iii) the evaluation of the mechanical response due to simultaneous time-dependent thermal and mechanical loads. Steps (ii) and (iii) are dealt with in the present paper. We present a two-step computational procedure where a 2D transient thermal analysis over the cross-sections of beams are made first, followed by mechanical analysis of the structure. Fundamental to the accuracy of the mechanical analysis is a new planar beam finite element. The effects of plasticity in concrete, and plasticity and viscous creep in steel are taken into consideration. The properties of concrete and steel along with the values of their thermal and mechanical parameters are taken according to the European standard ENV 1992-1-2 (1995). The comparison of our numerical and full-scale experimental results shows that the proposed mechanical and 2D thermal computational procedure is capable to describe the actual response of reinforced concrete beam structures to fire
A Global Plate Model Including Lithospheric Deformation Along Major Rifts and Orogens Since the Triassic
Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 × 106 km2 in the Late Jurassic (~160–155 Ma), driven by a vast network of rift systems. After a mid‐Cretaceous drop in deformation, it reaches a high of 48 x 106 km2 in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plate‐mantle system
Statistical Physics of Rupture in Heterogeneous Media
The damage and fracture of materials are technologically of enormous interest
due to their economic and human cost. They cover a wide range of phenomena like
e.g. cracking of glass, aging of concrete, the failure of fiber networks in the
formation of paper and the breaking of a metal bar subject to an external load.
Failure of composite systems is of utmost importance in naval, aeronautics and
space industry. By the term composite, we refer to materials with heterogeneous
microscopic structures and also to assemblages of macroscopic elements forming
a super-structure. Chemical and nuclear plants suffer from cracking due to
corrosion either of chemical or radioactive origin, aided by thermal and/or
mechanical stress. Despite the large amount of experimental data and the
considerable effort that has been undertaken by material scientists, many
questions about fracture have not been answered yet. There is no comprehensive
understanding of rupture phenomena but only a partial classification in
restricted and relatively simple situations. This lack of fundamental
understanding is indeed reflected in the absence of reliable prediction methods
for rupture, based on a suitable monitoring of the stressed system. Not only is
there a lack of non-empirical understanding of the reliability of a system, but
also the empirical laws themselves have often limited value. The difficulties
stem from the complex interplay between heterogeneities and modes of damage and
the possible existence of a hierarchy of characteristic scales (static and
dynamic).
The paper presents a review of recent efforts from the statistical physics
community to address these points.Comment: Enlarged review and updated references, 21 pages with 2 figure
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