5,005 research outputs found
A Whitney map onto the Long Arc
In a recent paper, Garc\'{\i}a-Velazquez has extended the notion of Whitney
map to include maps with non-metrizable codomain and left open the question of
whether there is a continuum that admits such a Whitney map. In this paper, we
consider two examples of hereditarily indecomposable, chainable continua of
weight constructed by Michel Smith; we show that one of them admits
a Whitney function onto the long arc and the other admits no Whitney maps at
all
Far points and discretely generated spaces
We give a partial solution to a question by Alas, Junqueria and Wilson by
proving that under PFA the one-point compactification of a locally compact,
discretely generated and countably tight space is also discretely generated.
After this, we study the cardinal number given by the smallest possible
character of remote and far sets of separable metrizable spaces. Finally, we
prove that in some cases a countable space has far points
Complete confined bases for beam propagation in Cartesian coordinates
Complete bases that are useful for beam propagation problems and that present
the distinct property of being spatially confined at the initial plane are
proposed. These bases are constructed in terms of polynomials of Gaussians, in
contrast with standard alternatives such as the Hermite-Gaussian basis that are
given by a Gaussian times a polynomial. The property of spatial confinement
implies that, for all basis elements, the spatial extent at the initial plane
is roughly the same. This property leads to an optimal scaling parameter that
is independent of truncation order for the fitting of a confined initial field.
Given their form as combinations of Gaussians, the paraxial propagation of
these basis elements can be modeled analytically.Comment: 6 pages, 4 figures, \c{opyright} 2017 Optical Society of America. One
print or electronic copy may be made for personal use only. Systematic
reproduction and distribution, duplication of any material in this paper for
a fee or for commercial purposes, or modifications of the content of this
paper are prohibite
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