2,290 research outputs found
Hermitian symmetric polynomials and CR complexity
Properties of Hermitian forms are used to investigate several natural
questions from CR Geometry. To each Hermitian symmetric polynomial we assign a
Hermitian form. We study how the signature pairs of two Hermitian forms behave
under the polynomial product. We show, except for three trivial cases, that
every signature pair can be obtained from the product of two indefinite forms.
We provide several new applications to the complexity theory of rational
mappings between hyperquadrics, including a stability result about the
existence of non-trivial rational mappings from a sphere to a hyperquadric with
a given signature pair.Comment: 19 pages, latex, fixed typos, to appear in Journal of Geometric
Analysi
Migrants at work: perspectives, perceptions and new connections. Work, Employment and Society, 34 (5) . pp. 745-748. ISSN 0950-0170
Migration â and the experiences of migrants â continue to occupy an important and controversial place in the scholarly and political debates on contemporary labour markets and societies. As new scenarios emerge at local, national and global levels, new insights and perspectives become necessary. The articles in this themed issue reflect the interest Work, Employment and Society has had in the topic of labour migrations and migrants at work for well over a decade and which led, for example, to the themed issue Migration at Work: Spaces, Borders and Boundaries in 32(5), 2018. Migration has of course been a prominent issue across the social sciences, and in recent years particularly in relation to the ârefugee crisisâ of 2015 and to intra-European migration ahead of and in light of Brexit. The experiences of migrants from Eastern and Central Europe in the workplace, their overqualification and devaluing of their cultural capital, and their positioning within segmented labour markets have produced a number of articles in past issues (e.g. Ciupijus, 2011; Samaluk, 2016; Sirkeci et al., 2018) to which those in the current issue (Leschke and Weiss; Rydzik and Anitha) make an important addition. [...
A COMPREHENSIVE ENERGETIC, EXERGETIC AND HEAT TRANSFER ANALYSIS OF A SOLAR ORGANIC RANKINE SYSTEM
Environmental concerns have been motivating the use of renewable energysources to meet sustainable requirements. In this context, concentrated solarpower driven by organic Rankine cycles has been classified as an up-andcomingtechnology to generate energy under low and moderate temperatures.In order to have a better understanding of the availability and utilization of thisenergy resource, the purpose of the present study is to perform acomprehensive energetic, exergetic and heat transfer analysis of a 200 kWsolar organic Rankine cycle through the presentation of the energy and exergyefficiencies and losses for each component; the exergy destruction at all stagesof the process; and the heat transfer behavior along the receiver. The thermalmodel was developed in Engineering Equation Solver and validated withliterature data. The solar collector was operated with Therminol 66 and theworking fluid employed in the power block was cyclohexane. The energeticefficiencies achieved in the solar field, power block, and overall system were64.97; 21.36; and 13.87 %, respectively. Considering the exergetic efficiencies,they were 27.37; 54.45; and 14.89 %, respectively. The solar resource variationshowed that the higher DNI value, the better the system performance
Tomographic test of Bell's inequality for a time-delocalized single photon
Time-domain balanced homodyne detection is performed on two well-separated
temporal modes sharing a single photon. The reconstructed density matrix of the
two-mode system is used to prove and quantify its entangled nature, while the
Wigner function is employed for an innovative tomographic test of Bell's
inequality based on the theoretical proposal by Banaszek and Wodkiewicz [Phys.
Rev. Lett. 82, 2009 (1999)]. Provided some auxiliary assumptions are made, a
clear violation of Banaszek-Bell's inequality is found.Comment: 7 pages, 3 figures: revised version with additional material;
accepetd for publication in Phys. Rev.
High-Resolution Spectroscopy of FUors
High-resolution spectroscopy was obtained of the FUors FU Ori and V1057 Cyg
between 1995 and 2002 with SOFIN at NOT and with HIRES at Keck I. During those
years FU Ori remained about 1 mag. (in B) below its 1938-39 maximum brightness,
but V1057 Cyg (B ~ 10.5 at peak in 1970-71) faded from about 13.5 to 14.9 and
then recovered slightly. Their photospheric spectra resemble a rotating G0 Ib
supergiant, with v_eq sin i = 70 km/s for FU Ori and 55 km/s for V1057 Cyg. As
V1057 Cyg faded, P Cyg structure in Halpha and the IR CaII lines strengthened
and a complex shortward-displaced shell spectrum increased in strength,
disappeared in 1999, and reappeared in 2001. Night-to-night changes in the wind
structure of FU Ori show evidence of sporadic infall. The strength of P Cyg
absorption varied cyclically with a period of 14.8 days, with phase stability
maintained over 3 seasons, and is believed to be the rotation period. The
structure of the photospheric lines also varies cyclically, but with a period
of 3.54 days. A similar variation may be present in V1057 Cyg. As V1057 Cyg has
faded, the emission lines of a pre-existing low-excitation chromosphere have
emerged, so we believe the `line doubling' in V1057 Cyg is produced by these
central emission cores in the absorption lines, not by orbital motion in an
inclined Keplerian disk. No dependence of v_eq sin i on wavelength or
excitation potential was detected in either star, again contrary to expectation
for a self-luminous accretion disk. Nor are critical lines in the near infrared
accounted for by synthetic disk spectra. A rapidly rotating star near the edge
of stability (Larson 1980), can better explain these observations. FUor
eruptions may not be a property of ordinary TTS, but may be confined to a
special subspecies of rapid rotators having powerful quasi-permanent winds.Comment: 41 pages (including 32 figures and 9 tables); ApJ, in press; author
affiliation, figs. 3 and 9 correcte
Internationalisation, cultural distance and country characteristics: a Bayesian analysis of SME's financial performance
Relying on the accounting data of a panel of 403 Italian manufacturing SMEs collected over a period of 5 years, we find results suggesting that multinationality per se does not impact on the economic performance of international small and medium sized firms. It is the characteristics of the country selected i.e. the political hazard, the financial stability and the economic performance that significantly influence SMEs financial performance. The management implication for small and medium sized firms selecting and entering new geographic markets is significant, since our results show that for SMEs it is the market selection process that really matters and not the degree of multinationality
Tameness of holomorphic closure dimension in a semialgebraic set
Given a semianalytic set S in a complex space and a point p in S, there is a
unique smallest complex-analytic germ at p which contains the germ of S, called
the holomorphic closure of S at p. We show that if S is semialgebraic then its
holomorphic closure is a Nash germ, for every p, and S admits a semialgebraic
filtration by the holomorphic closure dimension. As a consequence, every
semialgebraic subset of a complex vector space admits a semialgebraic
stratification into CR manifolds satisfying a strong version of the condition
of the frontier.Comment: Published versio
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