Countable Space

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Jinghai Shao - One of the best experts on this subject based on the ideXlab platform.

  • Criteria for transience and recurrence of regime-switching diffusion processes *
    Electronic Journal of Probability, 2015
    Co-Authors: Jinghai Shao
    Abstract:

    We provide some criteria for recurrence of regime-switching diffusion processes using the theory of M-matrix and the Perron-Frobenius theorem. State-independent and state-dependent regime-switching diffusion processes in a finite Space or in an infinite Countable Space are all studied in this work. Especially, we put forward a finite partition method to deal with switching processes in an infinite Countable Space. As an application, we study the recurrence of regime-switching Ornstein-Uhlenbeck process, and provide a necessary and sufficient condition for a kind of nonlinear regime-switching diffusion processes.

  • criteria for transience and recurrence of regime switching diffusion processes
    Electronic Journal of Probability, 2015
    Co-Authors: Jinghai Shao
    Abstract:

    We provide some criteria for recurrence of regime-switching diffusion processes using the theory of M-matrix and the Perron-Frobenius theorem. State-independent and state-dependent regime-switching diffusion processes in a finite Space or in an infinite Countable Space are all studied in this work. Especially, we put forward a finite partition method to deal with switching processes in an infinite Countable Space. As an application, we study the recurrence of regime-switching Ornstein-Uhlenbeck process, and provide a necessary and sufficient condition for a kind of nonlinear regime-switching diffusion processes.

  • Criteria for transience and recurrence of regime-switching diffusion processes *
    Electronic Journal of Probability, 2015
    Co-Authors: Jinghai Shao
    Abstract:

    We provide some on-off type criteria for recurrence of regime-switching diffusion processes using the theory of M-matrix, the Perron-Frobenius theorem. State-independent and state-dependent regime-switching diffusion processes in a finite Space and an infinite Countable Space are both studied. Especially, we put forward a finite partition method to deal with switching process in an infinite Countable Space. As an application, we study the recurrence of regime-switching Ornstein-Uhlenbeck process, and provide an on-off type criterion for a kind of nonlinear regime-switching diffusion processes.

  • criteria for transience and recurrence of regime switching diffusion processes
    arXiv: Probability, 2014
    Co-Authors: Jinghai Shao
    Abstract:

    We provide some on-off type criteria for recurrence and transience of regime-switching diffusion processes using the theory of M-matrix and the Perron-Frobenius theorem. State-independent and state-dependent regime-switching diffusion processes in a finite Space and a Countable Space are both studied. We put forward a finite partition method to deal with switching process in a Countable Space. As an application, we improve the known criteria for recurrence of linear regime-switching diffusion processes, and provide an on-off type criterion for a kind of nonlinear regime-switching diffusion processes.

Monica Patriche - One of the best experts on this subject based on the ideXlab platform.

Vladimir V. Tkachuk - One of the best experts on this subject based on the ideXlab platform.

  • Some applications of discrete selectivity and Banakh property in function Spaces
    European Journal of Mathematics, 2019
    Co-Authors: Vladimir V. Tkachuk
    Abstract:

    We establish that an unCountable Space X must be essentially unCountable whenever its extent and tightness are Countable. As a consequence, the equality $$\mathrm{ext}(X)= t(X)=\omega $$ ext ( X ) = t ( X ) = ω implies that the Space $$C_{p}(X, [0,1])$$ C p ( X , [ 0 , 1 ] ) is discretely selective. If X is a metrizable Space, then $$C_{p}(X, [0,1])$$ C p ( X , [ 0 , 1 ] ) has the Banakh property if and only if so does $$C_{p}(Y, [0,1])$$ C p ( Y , [ 0 , 1 ] ) for some closed separable $$Y\subset X$$ Y ⊂ X . We apply the above results to show that, for a metrizable X , the Space $$C_{p}(X, [0,1])$$ C p ( X , [ 0 , 1 ] ) is strongly dominated by a second Countable Space if and only if X is homeomorphic to $$D\,{\oplus }\, M$$ D ⊕ M where D is a discrete Space and M is Countable. For a metrizable Space X , we also prove that $$C_{p}(X,[0,1])$$ C p ( X , [ 0 , 1 ] ) has the Lindelöf $$\Sigma $$ Σ -property if and only if the set of non-isolated points of X is second Countable. Our results solve several open questions.

  • If Cp(X) is strongly dominated by a second Countable Space, then X is Countable
    Journal of Mathematical Analysis and Applications, 2017
    Co-Authors: D. Guerrero Sánchez, Vladimir V. Tkachuk
    Abstract:

    Abstract We establish that a Tychonoff Space X is Countable if and only if C p ( X ) is strongly dominated by a second Countable Space. The same is true for a compact Space K such that C p ( K , [ 0 , 1 ] ) is strongly dominated by a second Countable Space. We also prove that strong domination by a second Countable Space of the complement of the diagonal of a Tychonoff Space X implies that X is an ℵ 0 -Space. Our results solve several published open questions.

  • Strong domination by Countable and second Countable Spaces
    Topology and its Applications, 2017
    Co-Authors: Vladimir V. Tkachuk
    Abstract:

    Abstract We show that, for a Lindelof Σ-Space X, if C p ( X , [ 0 , 1 ] ) is strongly dominated by a second Countable Space, then X is Countable. Under Martin's Axiom we prove that there exists a Countable Space Z that strongly dominates the complement of the diagonal of any first Countable compact Space. In particular, strong domination by a Countable Space of the complement of the diagonal of a compact Space X need not imply metrizability of X. It turns out that the same Countable Space Z strongly dominates C p ( X ) for an unCountable Space X. Our results solve several published open problems.

  • Calibers, $$\omega $$ -continuous maps and function Spaces
    Revista de la Real Academia de Ciencias Exactas Fisicas y Naturales. Serie A. Matematicas, 2014
    Co-Authors: Oleg G. Okunev, Vladimir V. Tkachuk
    Abstract:

    The operation of extending functions from $$\scriptstyle X$$ to $$\scriptstyle \upsilon X$$ is $$\scriptstyle \omega $$ -continuous, so it is natural to study $$\scriptstyle \omega $$ -continuous maps systematically if we want to find out which properties of $$\scriptstyle C_p(X)$$ “lift” to $$\scriptstyle C_p(\upsilon X)$$ . We study the properties preserved by $$\scriptstyle \omega $$ -continuous maps and bijections both in general Spaces and in $$\scriptstyle C_p(X)$$ . We show that $$\scriptstyle \omega $$ -continuous maps preserve primary $$\scriptstyle \Sigma $$ -property as well as Countable compactness. On the other hand, existence of an $$\scriptstyle \omega $$ -continuous injection of a Space $$\scriptstyle X$$ to a second Countable Space does not imply $$\scriptstyle G_\delta $$ -diagonal in $$\scriptstyle X$$ ; however, existence of such an injection for a countably compact $$\scriptstyle X$$ implies metrizability of $$\scriptstyle X$$ . We also establish that $$\scriptstyle \omega $$ -continuous injections can destroy caliber $$\scriptstyle \omega _1$$ in pseudocompact Spaces. In the context of relating the properties of $$\scriptstyle C_p(X)$$ and $$\scriptstyle C_p(\upsilon X)$$ , a countably compact subSpace of $$\scriptstyle C_p(X)$$ remains countably compact in the topology of $$\scriptstyle C_p(\upsilon X)$$ ; however, compactness, pseudocompactness, Lindelöf property and Lindelöf $$\scriptstyle \Sigma $$ -property can be destroyed by strengthening the topology of $$\scriptstyle C_p(X)$$ to obtain the Space $$\scriptstyle C_p(\upsilon X)$$ . We show that Lindelöf $$\scriptstyle \Sigma $$ -property of $$\scriptstyle C_p(X)$$ together with $$\scriptstyle \omega _1$$ being a caliber of $$\scriptstyle C_p(X)$$ implies that $$\scriptstyle X$$ is cosmic.

  • Calibers, \omega -continuous maps and function Spaces
    Revista de la Real Academia de Ciencias Exactas Fisicas y Naturales. Serie A. Matematicas, 2012
    Co-Authors: Oleg Okunev, Vladimir V. Tkachuk
    Abstract:

    The operation of extending functions from \(\scriptstyle X\) to \(\scriptstyle \upsilon X\) is \(\scriptstyle \omega \)-continuous, so it is natural to study \(\scriptstyle \omega \)-continuous maps systematically if we want to find out which properties of \(\scriptstyle C_p(X)\) “lift” to \(\scriptstyle C_p(\upsilon X)\). We study the properties preserved by \(\scriptstyle \omega \)-continuous maps and bijections both in general Spaces and in \(\scriptstyle C_p(X)\). We show that \(\scriptstyle \omega \)-continuous maps preserve primary \(\scriptstyle \Sigma \)-property as well as Countable compactness. On the other hand, existence of an \(\scriptstyle \omega \)-continuous injection of a Space \(\scriptstyle X\) to a second Countable Space does not imply \(\scriptstyle G_\delta \)-diagonal in \(\scriptstyle X\); however, existence of such an injection for a countably compact \(\scriptstyle X\) implies metrizability of \(\scriptstyle X\). We also establish that \(\scriptstyle \omega \)-continuous injections can destroy caliber \(\scriptstyle \omega _1\) in pseudocompact Spaces. In the context of relating the properties of \(\scriptstyle C_p(X)\) and \(\scriptstyle C_p(\upsilon X)\), a countably compact subSpace of \(\scriptstyle C_p(X)\) remains countably compact in the topology of \(\scriptstyle C_p(\upsilon X)\); however, compactness, pseudocompactness, Lindelof property and Lindelof \(\scriptstyle \Sigma \)-property can be destroyed by strengthening the topology of \(\scriptstyle C_p(X)\) to obtain the Space \(\scriptstyle C_p(\upsilon X)\). We show that Lindelof\(\scriptstyle \Sigma \)-property of \(\scriptstyle C_p(X)\) together with \(\scriptstyle \omega _1\) being a caliber of \(\scriptstyle C_p(X)\) implies that \(\scriptstyle X\) is cosmic.

João Correia-da-silva - One of the best experts on this subject based on the ideXlab platform.

Yan-kui Song - One of the best experts on this subject based on the ideXlab platform.

  • Remarks on absolutely star Countable Spaces
    Open Mathematics, 2013
    Co-Authors: Yan-kui Song
    Abstract:

    We prove the following statements: (1) every Tychonoff linked-Lindelof (centered-Lindelof, star Countable) Space can be represented as a closed subSpace in a Tychonoff pseudocompact absolutely star Countable Space; (2) every Hausdorff (regular, Tychonoff) linked-Lindelof Space can be represented as a closed Gδ-subSpace in a Hausdorff (regular, Tychonoff) absolutely star Countable Space; (3) there exists a pseudocompact absolutely star Countable Tychonoff Space having a regular closed subSpace which is not star Countable (hence not absolutely star Countable); (4) assuming \(2^{\aleph _0 } = 2^{\aleph _1 }\), there exists an absolutely star Countable normal Space having a regular closed subSpace which is not star Countable (hence not absolutely star Countable).