3,408 research outputs found
Moderate Growth Time Series for Dynamic Combinatorics Modelisation
Here, we present a family of time series with a simple growth constraint.
This family can be the basis of a model to apply to emerging computation in
business and micro-economy where global functions can be expressed from local
rules. We explicit a double statistics on these series which allows to
establish a one-to-one correspondence between three other ballot-like
strunctures
Recipe theorem for the Tutte polynomial for matroids, renormalization group-like approach
Using a quantum field theory renormalization group-like differential
equation, we give a new proof of the recipe theorem for the Tutte polynomial
for matroids. The solution of such an equation is in fact given by some
appropriate characters of the Hopf algebra of isomorphic classes of matroids,
characters which are then related to the Tutte polynomial for matroids. This
Hopf algebraic approach also allows to prove, in a new way, a matroid Tutte
polynomial convolution formula appearing in W. Kook {\it et. al., J. Comb.
Series} {\bf B 76} (1999).Comment: 14 pages, 3 figure
The mechanics of shuffle products and their siblings
We carry on the investigation initiated in [15] : we describe new shuffle
products coming from some special functions and group them, along with other
products encountered in the literature, in a class of products, which we name
-shuffle products. Our paper is dedicated to a study of the latter
class, from a combinatorial standpoint. We consider first how to extend
Radford's theorem to the products in that class, then how to construct their
bi-algebras. As some conditions are necessary do carry that out, we study them
closely and simplify them so that they can be seen directly from the definition
of the product. We eventually test these conditions on the products mentioned
above
Phantom Black Holes in Einstein-Maxwell-Dilaton Theory
We obtain the general static, spherically symmetric solution for the
Einstein-Maxwell-dilaton system in four dimensions with a phantom coupling for
the dilaton and/or the Maxwell field. This leads to new classes of black hole
solutions, with single or multiple horizons. Using the geodesic equations, we
analyse the corresponding Penrose diagrams revealing, in some cases, new causal
structures.Comment: Latex file, 32 pages, 15 figures in eps format. Typo corrected in Eq.
(3.18
HI emission from the red giant Y CVn with the VLA and FAST
Imaging studies with the VLA have revealed HI emission associated with the
extended circumstellar shells of red giants. We analyse the spectral map
obtained on Y CVn, a J-type carbon star on the AGB. The HI line profiles can be
interpreted with a model of a detached shell resulting from the interaction of
a stellar outflow with the local interstellar medium. We reproduce the spectral
map by introducing a distortion along a direction corresponding to the star's
motion in space. We then use this fitting to simulate observations expected
from the FAST radiotelescope, and discuss its potential for improving
ourdescription of the outer regions of circumstellar shells.Comment: accepted for publication in RA
Microscopic nanomechanical dissipation in gallium arsenide resonators
We report on a systematic study of nanomechanical dissipation in
high-frequency (approximatively 300 MHz) gallium arsenide optomechanical disk
resonators, in conditions where clamping and fluidic losses are negligible.
Phonon-phonon interactions are shown to contribute with a loss background
fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina
at the surface modifies the quality factor of resonators, pointing towards the
importance of surface dissipation. The temperature evolution is accurately
fitted by two-level systems models, showing that nanomechanical dissipation in
gallium arsenide resonators directly connects to their microscopic properties.
Two-level systems, notably at surfaces, appear to rule the damping and
fluctuations of such high-quality crystalline nanomechanical devices, at all
temperatures from 3 to 300K
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