9,305 research outputs found
On Logical Depth and the Running Time of Shortest Programs
The logical depth with significance of a finite binary string is the
shortest running time of a binary program for that can be compressed by at
most bits. There is another definition of logical depth. We give two
theorems about the quantitative relation between these versions: the first
theorem concerns a variation of a known fact with a new proof, the second
theorem and its proof are new. We select the above version of logical depth and
show the following. There is an infinite sequence of strings of increasing
length such that for each there is a such that the logical depth of the
th string as a function of is incomputable (it rises faster than any
computable function) but with replaced by the resuling function is
computable. Hence the maximal gap between the logical depths resulting from
incrementing appropriate 's by 1 rises faster than any computable function.
All functions mentioned are upper bounded by the Busy Beaver function. Since
for every string its logical depth is nonincreasing in , the minimal
computation time of the shortest programs for the sequence of strings as a
function of rises faster than any computable function but not so fast as
the Busy Beaver function.Comment: 12 pages LaTex (this supercedes arXiv:1301.4451
Asymptotic behaviour and numerical approximation of optimal eigenvalues of the Robin Laplacian
We consider the problem of minimising the eigenvalue of the Robin
Laplacian in . Although for and a positive boundary
parameter it is known that the minimisers do not depend on ,
we demonstrate numerically that this will not always be the case and illustrate
how the optimiser will depend on . We derive a Wolf-Keller type result
for this problem and show that optimal eigenvalues grow at most with ,
which is in sharp contrast with the Weyl asymptotics for a fixed domain. We
further show that the gap between consecutive eigenvalues does go to zero as
goes to infinity. Numerical results then support the conjecture that for
each there exists a positive value of such that the eigenvalue is minimised by disks for all and,
combined with analytic estimates, that this value is expected to grow with
Absence of Gluonic Components in Axial and Tensor Mesons
A quarkonium-gluonium mixing scheme previously developed to describe the
characteristic of the pseudoscalar mesons is applied to axial and tensor
mesons. The parameters of the model are determined by fitting the eigenvalues
of a mass matrix. The corresponding eigenvectors give the proportion of light
quarks, strange quarks and glueball in each meson. However the predictions of
the model for branching ratios and electromagnetic decays are incompatible with
the experimental results. These results suggest the absence of gluonic
components in the states of axial and tensor isosinglet mesons analyzed here.Comment: 12 page
Thermoelectric response of FeTeSe: evidence for strong correlation and low carrier density
We present a study of the Seebeck and Nernst coefficients of
FeTeSe extended up to 28 T. The large magnitude of the
Seebeck coefficient in the optimally doped sample tracks a remarkably low
normalized Fermi temperature, which, like other correlated superconductors, is
only one order of magnitude larger than T. We combine our data with other
experimentally measured coefficients of the system to extract a set of
self-consistent parameters, which identify FeTeSe as a
low-density correlated superconductor barely in the clean limit. The system is
subject to strong superconducting fluctuations with a sizeable vortex Nernst
signal in a wide temperature window.Comment: 4 pages including 4 figure
Elastic properties of carbon nanotubes and their heterojunctions
Comprehensive studies on the modelling and numerical simulation of the mechanical behaviour under tension, bending and torsion of single-walled carbon nanotubes and their heterojunctions are performed. It is proposed to deduce the mechanical properties of the carbon nanotubes heterojunctions from the knowledge of the mechanical properties of the single-walled carbon nanotubes, which are their constituent key unit
EstratĂ©gias comunicacionais da Embrapa Trigo e pĂșblico-alvo.
Orientadora: Joseani Mesquita Antunes
A new method based on noise counting to monitor the frontend electronics of the LHCb muon detector
A new method has been developed to check the correct behaviour of the
frontend electronics of the LHCb muon detector. This method is based on the
measurement of the electronic noise rate at different thresholds of the
frontend discriminator. The method was used to choose the optimal discriminator
thresholds. A procedure based on this method was implemented in the detector
control system and allowed the detection of a small percentage of frontend
channels which had deteriorated. A Monte Carlo simulation has been performed to
check the validity of the method
Predicting the critical density of topological defects in O(N) scalar field theories
O(N) symmetric field theories describe many critical
phenomena in the laboratory and in the early Universe. Given N and ,
the dimension of space, these models exhibit topological defect classical
solutions that in some cases fully determine their critical behavior. For N=2,
D=3 it has been observed that the defect density is seemingly a universal
quantity at T_c. We prove this conjecture and show how to predict its value
based on the universal critical exponents of the field theory. Analogously, for
general N and D we predict the universal critical densities of domain walls and
monopoles, for which no detailed thermodynamic study exists. This procedure can
also be inverted, producing an algorithm for generating typical defect networks
at criticality, in contrast to the canonical procedure, which applies only in
the unphysical limit of infinite temperature.Comment: 4 pages, 3 figures, uses RevTex, typos in Eq.(11) and (14) correcte
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