共查询到20条相似文献,搜索用时 140 毫秒
1.
Let X be a realcompact space and ${H:C(X)\rightarrow\mathbb{R}}$ be an identity and order preserving group homomorphism. It is shown that H is an evaluation at some point of X if and only if there is ${\varphi\in C(\mathbb{R})}$ with ${\varphi(r)>\varphi(0)}$ for all ${r\in\mathbb{R}-\{0\}}$ for which ${H\circ\varphi=\varphi\circ H}$ . This extends (and unifies) classical results by Hewitt and Shirota. 相似文献
2.
In this paper, we construct a new family of harmonic morphisms ${\varphi:V^5\to\mathbb{S}^2}In this paper, we construct a new family of harmonic morphisms
j:V5?\mathbbS2{\varphi:V^5\to\mathbb{S}^2}, where V
5 is a 5-dimensional open manifold contained in an ellipsoidal hypersurface of
\mathbbC4 = \mathbbR8{\mathbb{C}^4\,=\,\mathbb{R}^8}. These harmonic morphisms admit a continuous extension to the completion V*5{{V^{\ast}}^5}, which turns out to be an explicit real algebraic variety. We work in the context of a generalization of the Hopf construction
and equivariant theory. 相似文献
3.
Let
J:\mathbbR ? \mathbbRJ:\mathbb{R} \to \mathbb{R}
be a nonnegative, smooth compactly supported function such that
ò\mathbbR J(r)dr = 1. \int_\mathbb{R} {J(r)dr = 1.}
We consider the nonlocal diffusion problem
$
u_t (x,t) = \int_\mathbb{R} {J\left( {\frac{{x - y}}
{{u(y,t)}}} \right)dy - u(x,t){\text{ in }}\mathbb{R} \times [0,\infty )}
$
u_t (x,t) = \int_\mathbb{R} {J\left( {\frac{{x - y}}
{{u(y,t)}}} \right)dy - u(x,t){\text{ in }}\mathbb{R} \times [0,\infty )}
相似文献
4.
Let j{\varphi} be an analytic self-map of the unit disk
\mathbbD{\mathbb{D}},
H(\mathbbD){H(\mathbb{D})} the space of analytic functions on
\mathbbD{\mathbb{D}} and
g ? H(\mathbbD){g \in H(\mathbb{D})}. The boundedness and compactness of the operator DCj : H¥ ? Z{DC_\varphi : H^\infty \rightarrow { \mathcal Z}} are investigated in this paper. 相似文献
5.
Wojciech Kucharz 《Mathematische Annalen》2010,346(4):829-856
Every compact smooth manifold M is diffeomorphic to the set
X(\mathbbR){X(\mathbb{R})} of real points of a nonsingular projective real algebraic variety X, which is called an algebraic model of M. Each algebraic cycle of codimension k on the complex variety
X\mathbbC=X×\mathbbR\mathbbC{X_{\mathbb{C}}=X\times_{\mathbb{R}}\mathbb{C}} determines a cohomology class in
H2k(X(\mathbbR);\mathbbD){H^{2k}(X(\mathbb{R});\mathbb{D})} , where
\mathbbD{\mathbb{D}} denotes
\mathbbZ{\mathbb{Z}} or
\mathbbQ{\mathbb{Q}} . We investigate the behavior of such cohomology classes as X runs through the class of algebraic models of M. 相似文献
6.
Let ${s,\,\tau\in\mathbb{R}}
7.
A. S. Morozov 《Algebra and Logic》2012,51(1):66-88
It is proved that every two Σ-presentations of an ordered field \mathbbR \mathbb{R} of reals over \mathbbH\mathbbF ( \mathbbR ) \mathbb{H}\mathbb{F}\,\left( \mathbb{R} \right) , whose universes are subsets of \mathbbR \mathbb{R} , are mutually Σ-isomorphic. As a consequence, for a series of functions f:\mathbbR ? \mathbbR f:\mathbb{R} \to \mathbb{R} (e.g., exp, sin, cos, ln), it is stated that the structure \mathbbR \mathbb{R} = 〈R, +, ×, <, 0, 1, f〉 lacks such Σ-presentations over \mathbbH\mathbbF ( \mathbbR ) \mathbb{H}\mathbb{F}\,\left( \mathbb{R} \right) . 相似文献
8.
We characterize when an ideal of the algebra ${A(\mathbb{R}^d)}
9.
David Fried 《Journal of Fixed Point Theory and Applications》2009,6(1):87-92
When X is a finite complex and p1X\pi_{1}X acts on
\mathbbR2{\mathbb{R}}^2 by translations we give criteria involving H2X for an equivariant map
F : [(X)\tilde] ? \mathbbR2F : \tilde{X} \rightarrow {\mathbb{R}}^2 to be onto. Following work of Manning and Shub, this leads to entropy bounds related to Shub’s entropy conjecture. 相似文献
10.
Igor V. Protasov 《Algebra Universalis》2009,62(4):339-343
Let ${\mathbb{A}}
11.
Let X be a normed space and V be a convex subset of X. Let a\colon \mathbbR+ ? \mathbbR+{\alpha \colon \mathbb{R}_+ \to \mathbb{R}_+}. A function f \colon V ? \mathbbR{f \colon V \to \mathbb{R}} is called α-midconvex if
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