11,657 research outputs found
Spin Axioms in Relativistic Continuum Physics
The 24 components of the relativistic spin tensor consist of 3+3 basic spin
fields and 9+9 constitutive fields. Empirically only 3 basic spin fields and 9
constitutive fields are known. This empirem can be expressed by two spin
axioms, one of them identifying 3 spin fields, and the other one 9 constitutive
fields to each other. This identification by the spin axioms is
material-independent and does not mix basic spin fields with constitutive
properties. The approaches to the Weyssenhoff fluid and the Dirac-electron
fluid found in literature are discussed with regard to these spin axioms. The
conjecture is formulated, that another reduction from 6 to 3 basic spin fields
which does not obey the spin axioms introduces special material properties by
not allowed mixing of constitutive and basic fields.Comment: 15 pages, dirac-electron example has been rewritte
On the Shape of the Tail of a Two Dimensional Sand Pile
We study the shape of the tail of a heap of granular material. A simple
theoretical argument shows that the tail adds a logarithmic correction to the
slope given by the angle of repose. This expression is in good agreement with
experiments. We present a cellular automaton that contains gravity, dissipation
and surface roughness and its simulation also gives the predicted shape.Comment: LaTeX file 4 pages, 4 PS figures, also available at
http://pmmh.espci.fr
Flavour violating bosonic squark decays at LHC
We study quark flavour violation (QFV) in the squark sector of the Minimal
Supersymmetric Standard Model (MSSM). We assume mixing between the second and
the third squark generations, i.e. sc_R-st_{L,R} mixing mixing. We focus on QFV
effects in bosonic squark decays, in particular on the decay into the lightest
Higgs boson h0, su_2 -> su_1 h0, where su_{1,2} are the lightest up-type
squarks. We show that the branching ratio of this QFV decay can be quite large
(up to 50 %) due to large QFV trilinear couplings, and large sc_R-st_{L, R} and
st_L-st_R mixing, despite the strong constraints on QFV from B meson data. This
can result in characteristic QFV final states with significant rates at LHC (14
TeV), such as pp -> gluino gluino X -> t + h0 + 3jets + Etmiss + X and pp ->
gluino gluino X -> t t (or tbar tbar) + h0 + 2jets + Etmiss + X. The QFV
bosonic squark decays can have an influence on the squark and gluino searches
at LHC.Comment: Figure 3 replaced, Section 4 revise
Flavour violating squark and gluino decays at LHC
We study the effects of squark generation mixing on squark and gluino
production and decays at LHC in the Minimal Supersymmetric Standard Model
(MSSM) with focus on the mixing between second and third generation squarks.
Taking into account the constraints from B-physics experiments we show that
various regions in parameter space exist where decays of squarks and/or gluinos
into quark flavour violating (QFV) final states can have large branching
ratios. Here we consider both fermionic and bosonic decays of squarks. Rates of
the corresponding QFV signals, e.g. pp -> t t bar{c} bar{c} missing-E_T X, can
be significant at LHC(14 TeV). We find that the inclusion of flavour mixing
effects can be important for the search of squarks and gluinos and the
determination of the underlying model parameters of the MSSM at LHC.Comment: 7 pages, 4 figures, a reference updated, Proceedings of The 36th
International Conference on High Energy Physics (ICHEP2012), Melbourne,
Australia, July 4-11, 201
Velocity statistics in excited granular media
We present an experimental study of velocity statistics for a partial layer
of inelastic colliding beads driven by a vertically oscillating boundary. Over
a wide range of parameters (accelerations 3-8 times the gravitational
acceleration), the probability distribution P(v) deviates measurably from a
Gaussian for the two horizontal velocity components. It can be described by
P(v) ~ exp(-|v/v_c|^1.5), in agreement with a recent theory. The characteristic
velocity v_c is proportional to the peak velocity of the boundary. The granular
temperature, defined as the mean square particle velocity, varies with particle
density and exhibits a maximum at intermediate densities. On the other hand,
for free cooling in the absence of excitation, we find an exponential velocity
distribution. Finally, we examine the sharing of energy between particles of
different mass. The more massive particles are found to have greater kinetic
energy.Comment: 27 pages, 13 figures, to appear in Chaos, September 99, revised 3
figures and tex
Eg versus x relation from photoluminescence and electron microprobe investigations in p-type Hg1âxCdxTe (0.35 =< x =< 0.7)
Combined photoluminescence (at 10 T 300 K) and electron microprobe investigations have been carried out with HgCdTe samples grown from the melt or from solution. By exciting the samples through metallic masks with 200 ÎŒm diameter holes fixed with respect to the sample care was taken to pick-up both characteristic X-ray radiation as well as the photoluminescence from the same sample area. The Eg versus x relation determined in this way at T = 30 K has been compared with data from the interband absorption edge by other authors
Constitutive Theory in General Relativity and Einstein-Cartan Theory: Spin Balances, Energy-Momentum Balances and Weyssenhoff Fluid
It is shown, that the usually considered spin balances are too restrictive and only valid for pointlike particles. Furthermore, we will derive the full spin balance and discuss the Weyssenhoff-Fluid
Cluster counting: The Hoshen-Kopelman algorithm vs. spanning tree approaches
Two basic approaches to the cluster counting task in the percolation and
related models are discussed. The Hoshen-Kopelman multiple labeling technique
for cluster statistics is redescribed. Modifications for random and aperiodic
lattices are sketched as well as some parallelised versions of the algorithm
are mentioned. The graph-theoretical basis for the spanning tree approaches is
given by describing the "breadth-first search" and "depth-first search"
procedures. Examples are given for extracting the elastic and geometric
"backbone" of a percolation cluster. An implementation of the "pebble game"
algorithm using a depth-first search method is also described.Comment: LaTeX, uses ijmpc1.sty(included), 18 pages, 3 figures, submitted to
Intern. J. of Modern Physics
Some physical-metallurgical properties of scandium, yttrium
In the continuing effort to learn more about the nature of metals, the rare earth elements in particular, the crystal structures and precision lattice parameters of these metals were investigated. High purity metals were examined by powder, single crystal and back reflection x-ray diffraction techniques. All but four of the back reflection samples were prepared by distillation in high vacuum (approximately 2 x 10-7 mm. mercury). The back reflection examinations, by which very accurate lattice parameters can be determined, were considered necessary if quantitative comparisons of the properties of the rare earths are to be made. Although scandium and yttrium are not classified as rare earths, they were considered similar enough in their behavior to include them in this study
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