6,681 research outputs found
Depolarization remote sensing by orthogonality breaking
A new concept devoted to sensing the depolarization strength of materials
from a single measurement is proposed and successfully validated on a variety
of samples. It relies on the measurement of the orthogonality breaking between
two orthogonal states of polarization after interaction with the material to be
characterized. The two fields orthogonality being preserved after propagation
in birefringent media, this concept is shown to be perfectly suited to
depolarization remote sensing through fibers, opening the way to real time
depolarization endoscopy.Comment: 5 pages, 4 figure
S-Restricted Compositions Revisited
An S-restricted composition of a positive integer n is an ordered partition
of n where each summand is drawn from a given subset S of positive integers.
There are various problems regarding such compositions which have received
attention in recent years. This paper is an attempt at finding a closed- form
formula for the number of S-restricted compositions of n. To do so, we reduce
the problem to finding solutions to corresponding so-called interpreters which
are linear homogeneous recurrence relations with constant coefficients. Then,
we reduce interpreters to Diophantine equations. Such equations are not in
general solvable. Thus, we restrict our attention to those S-restricted
composition problems whose interpreters have a small number of coefficients,
thereby leading to solvable Diophantine equations. The formalism developed is
then used to study the integer sequences related to some well-known cases of
the S-restricted composition problem
Character amenability of Banach algebras
We introduce the notion of character amenable Banach algebras. We prove that character amenability for either of the group algebra L(1)(G) or the Fourier algebra A(G) is equivalent to the amenability of the underlying group G. Character amenability of the measure algebra M(G) is shown to be equivalent to G being a discrete amenable group. We also study functorial properties of character amenability. For a commutative character amenable Banach algebra A, we prove all cohomological groups with coefficients in finite-dimensional Banach A-bimodules, vanish. As a corollary we conclude that all finite-dimensional extensions of commutative character amenable Banach algebras split strongly
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