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Let T be an operator on a separable Hilbert space H , then it is called supercyclic if there exists an xH , (called supercyclic vector for T ) such that the set { λT n x : λ ∊ ℂ} is dense in H . Let T = ( T 1 , ..., T N ) be a system of N commuting contractions defined on a separable Hilbert space, in this article we will show that if there exists at least a point of the Harte spectrum on
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{bbm} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\mathbb{T}^N$$ \end{document}
(where
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{bbm} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\mathbb{T}$$ \end{document}
is the unit circle), then there exists a vector such that is not supercyclic for any of the N -contractions. This result complements recent results of M. Kosiek and A. Octavio (see [4]) and extend results in [7].
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Although there is considerable consensus that Finance, Management and Marketing are ‘science’, some debate remains with regard to whether these three areas comprise autonomous, organized and settled scientific fields of research. In this paper we aim to explore this issue by analyzing the occurrence of citations in the top-ranked journals in the areas of Finance, Management, and Marketing. We put forward a modified version of the model of science as a network, proposed by Klamer and Van Dalen (J Econ Methodol 9(2):289–315, <cite>2002</cite>), and conclude that Finance is a ‘Relatively autonomous, organized and settled field of research’, whereas Management and (to a larger extent) Marketing are relatively non-autonomous and hybrid fields of research’. Complementary analysis based on sub-discipline rankings using the recursive methodology of Liebowitz and Palmer (J Econ Lit 22:77–88, <cite>1984</cite>) confirms the results. In conclusions we briefly discuss the pertinence of Whitley’s (The intellectual and social organization of the sciences, <cite>1984</cite>) theory for explaining cultural differences across these sub-disciplines based on its dimensions of scholarly practices, ‘mutual dependency’ and ‘task uncertainty’.

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Despite the vitality and dynamism that the field of entrepreneurship has experienced in the last decade, the issue of whether it comprises an effective network of (in)formal communication linkages among the most influential scholars within the area has yet to be examined in depth. This study follows a formal selection procedure to delimit the ‘relational environment’ of the field of entrepreneurship and to analyze the existence and characterization of (in)visible college(s) based on a theoretically well-grounded framework, thus offering a comprehensive and up-to-date empirical analysis of entrepreneurship research. Based on more than a 1,000 papers published between 2005 and 2010 in seven core entrepreneurship journals and the corresponding (85,000) citations, we found that entrepreneurship is an (increasingly) autonomous, legitimate and cohesive (in)visible college, fine tuned through the increasing visibility of certain subject specialties (e.g., family business, innovation, technology and policy). Moreover, the rather dense formal links that characterize the entrepreneurship (in)visible college are accompanied by a reasonably solid network of informal relations maintained and sustained by the mobility of ‘stars’ and highly influential scholars. The limited internationalization of the entrepreneurship community, reflected in the almost total absence of non-English-speaking authors/studies/outlets, stands as a major quest for the field.

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The study of university–industry (U–I) relations has been the focus of growing interest in the literature. However, to date, a quantitative overview of the existing literature in this field has yet to be accomplished. This study intends to fill this gap through the use of bibliometric techniques. By using three different yet interrelated databases—a database containing the articles published on U–I links, which encompass 534 articles published between 1986 and 2011; a ‘roots’ database, which encompasses over 20,000 references to the articles published on U–I relations; and a ‘influences’ database which includes more than 15,000 studies that cited the articles published on U–I relations—we obtained the following results: (1) ‘Academic spin offs’, ‘Scientific and technological policies’ and (to a greater extent) ‘Knowledge Transfer Channels’ are topics in decline; (2) ‘Characteristics of universities, firms and scientists’, along with ‘Regional spillovers’, show remarkable growth, and ‘Measures and indicators’ can be considered an emergent topic; (3) clear tendency towards ‘empirical’ works, although ‘appreciative and empirical’ papers constitute the bulk of this literature; (4) the multidisciplinary nature of the intellectual roots of the U–I literature—an interesting blending of neoclassical economics (focused on licensing, knowledge transfer and high-tech entrepreneurship) and heterodox approaches (mainly related to systems of innovation) is observed in terms of intellectual roots; (5) the influence of the U–I literature is largely concentrated on the industrialized world and on the research area of innovation and technology (i.e., some ‘scientific endogamy’ is observed).

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headings in the title field including variant names such as Arctic or North Pole or subpolar or aurora (not Aurora Australis) or polar. Arctic Polar regions include the Arctic Ocean, the edge of the coastal land and islands, the Arctic tundra and taiga such

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