Abstract: Let $\Omega = {\Omega _1} \times \cdots \times {\Omega _n}(n > 1)$ be a product of $n$ Brelot harmonic spaces each of which has a bounded potential, and let $K$ be a compact subset of $\Omega$...
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Abstract: Let $\Omega = {\Omega _1} \times \cdots \times {\Omega _n}(n > 1)$ be a product of $n$ Brelot harmonic spaces each of which has a bounded potential, and let $K$ be a compact subset of $\Omega$. Then, $K$ is an $n$-polar set with the property that every $i$-section $(1 \leqslant i < n)$ of $K$ through any point in $\Omega$ is $(n - i)$ polar if and only if every positive continuous function on $K$ can be extended to a continuous potential on $\Omega$. Further, it has been shown that if $f$ is a nonnegative continuus function on $\Omega$ with compact support, then $MRf$, the multireduced function of $f$ over $\Omega$, is also a continuous function on $\Omega$.
It can be traced back to Brouwer that continuous functions of type StrA -> B, where StrA is the type of infinite streams over elements of A, can be represented by well founded, A-branching trees whose leafs are ele...
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It can be traced back to Brouwer that continuous functions of type StrA -> B, where StrA is the type of infinite streams over elements of A, can be represented by well founded, A-branching trees whose leafs are elements of B. This paper generalises the above correspondence to functions defined on final coalgebras for power-series functors on the category of sets and functions. While our main technical contribution is the characterisation of all continuous functions, defined on a final coalgebra and taking values in a discrete space by means of inductive types, a methodological point is that these inductive types are most conveniently formulated in a framework of dependent type theory.
It is shown that quasi all continuous functions on the unit circle have the property that for many small subsets E of the circle the partial sums of their Fourier series considered as functions restricted to E exhibit...
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It is shown that quasi all continuous functions on the unit circle have the property that for many small subsets E of the circle the partial sums of their Fourier series considered as functions restricted to E exhibit certain universality properties (C) 2010 Academie des sciences Published by Elsevier Masson SAS All rights reserved
Abstract: We prove that if $\{ {a_n}\} _{n = 1}^\infty$ is such that ${a_n} \searrow 0$ and \[ \lim \limits _{n \to \infty } ({a_n}_{ + 1}/{a_n}) = 1,\] then for the typical continuous function $f$ we have \[ ...
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Abstract: We prove that if $\{ {a_n}\} _{n = 1}^\infty$ is such that ${a_n} \searrow 0$ and \[ \lim \limits _{n \to \infty } ({a_n}_{ + 1}/{a_n}) = 1,\] then for the typical continuous function $f$ we have \[ {S_{{n_0}}}: = \sum \limits _{n = {n_0}}^\infty | f({x_n}_{ + 1}) - f({x_n})| = + \infty \] whenever $x \in [0,1 - {a_{{n_0}}}]$ and ${x_n} \in [x + {a_{n + 1}},x + {a_n}]$. Based on our result in a previous paper, we know that the above theorem fails to hold if ${a_{n + 1}}/{a_n} = \lambda < 1$. We also prove that if $\{ {a_n}\} _{n = 1}^\infty$ is such that ${a_n} \searrow 0$, then for the typical continuous function $f$ we have ${S_{{n_0}}} = + \infty {\text { if }}{x_n} = x + {a_n}$ and $x \in [0,1 - {a_{{n_0}}}]$.
In a previous paper we gave a representation of, and simultaneously a way of programming with, continuous functions on streams, whether discrete-valued functions, or functions between streams. We also defined a combin...
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In a previous paper we gave a representation of, and simultaneously a way of programming with, continuous functions on streams, whether discrete-valued functions, or functions between streams. We also defined a combinator on the representations of such continuous functions that reflects composition. Streams are one of the simplest examples of non-trivial final coalgebras. Here we extend our previous results to cover the case of final coalgebras for a broader class of functors than that giving rise to streams. Among the functors we can deal with are those that arise from countable signatures of finite-place untyped operators. These have many applications. The topology we put on the final coalgebra for such a functor is that induced by taking for basic neighbourhoods the set of infinite objects which share a common ` prefix', a la Baire space. The datatype of prefixes is defined together with the set of ` growth points' in a prefix, simultaneously. This we call beheading. To program and reason about representations of continuous functions requires a language whose type system incorporates the dependent function and pair types, inductive definitions at types Set, I -> Set and (Sigma I : Set) Set(I), coinductive definitions at types Set and I -> Set, as well as universal arrows for such definitions.
Let be a second countable Brelot harmonic space with a positive potential. If is a compact subset of with more than one point, then is a polar set iff every positive continuous function on can be extended to a continu...
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Let be a second countable Brelot harmonic space with a positive potential. If is a compact subset of with more than one point, then is a polar set iff every positive continuous function on can be extended to a continuous potential on . This is a generalization of the result proved by H. Wallin for the special case with Laplace harmonic space.
Theorem: every normal operator is a continuous function of a Hermitian one. Corollary: every normal operator on a separable Hilbert space is the sum of a diagonal operator and a compact one.
Theorem: every normal operator is a continuous function of a Hermitian one. Corollary: every normal operator on a separable Hilbert space is the sum of a diagonal operator and a compact one.
Let ℝn be the n-dimensional Euclidean space, and let { • } be a norm in Rn. Two lines l1 and l2 in ℝn are said to be { • }-orthogonal if their { • }-unit direction vectors e 1 and e 2 satisfy {e 1 + e 2} = {e 1 - e 2}...
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