575 research outputs found
Chiral symmetry breaking in the Wegner-Houghton approach
The Wegner-Houghton formulation of the exact renormalization group evolution
equation is used in order to study the chiral symmetry breaking of the linear
sigma model coupled to an isospin doublet of quarks. A numerical investigation
for a particular truncation of the equation which includes the scalar field
renormalization function is presented.Comment: 4 pages,4 eps figures. Contribution to CRIS2000, Catania, May 200
Extended radio emission in BL Lac objects - I: the images
We have observed 28 sources selected from the 1Jy sample of BL Lac objects
(Stickel et al. 1991) with the Very Large Array (VLA) in A, B and D
configurations at 1.36, 1.66 and 4.85 GHz, and/or with the Westerbork Synthesis
Radio Telescope (WSRT) at 1.40 GHz. In this paper we present high sensitivity
images at arcsecond resolution of the 18 objects showing extended structure in
our images, and of another source from the FIRST (Faint Images of the Radio Sky
at Twenty-cm) survey (Becker et al. 1995). In general our high sensitivity
images reveal an amount of extended emission larger than previously reported.
In some objects the luminosity of the extended structure is comparable with
that of FR~II radio sources. A future paper will be devoted to the
interpretation of these results.Comment: 12 pages, 35 figures, to appear on A&A Supp. Ser., postscript file
with figures included available at
http://www.ira.noto.cnr.it/staff/carlo/ds1030.ps.g
Topological phase transitions in four dimensions
We show that four-dimensional systems may exhibit a topological phase transition analogous to the well-known Berezinskii-Kosterlitz-Thouless vortex unbinding transition in two-dimensional systems. We study a suitable generalization of the sine-Gordon model in four dimensions and the renormalization group flow equation of its couplings, showing that the critical value of the frequency is the square of the corresponding value in 2D. The value of the anomalous dimension at the critical point is determined (\u3b7=1/32) and a conjecture for the universal jump of the superfluid stiffness (4/\u3c02) presented
Tower sets and other configurations with the Cohen-Macaulay property
Some well-known arithmetically Cohen-Macaulay configurations of linear varieties in Pr as k-configurations, partial intersections and star configurations are generalized by introducing tower schemes. Tower schemes are reduced schemes that are a finite union of linear varieties whose support set is a suitable finite subset of Z+c called tower set. We prove that the tower schemes are arithmetically Cohen-Macaulay and we compute their Hilbert function in terms of their support. Afterwards, since even in codimension 2 not every arithmetically Cohen-Macaulay squarefree monomial ideal is the ideal of a tower scheme, we slightly extend this notion by defining generalized tower schemes (in codimension 2). Our main result consists in showing that the support of these configurations (the generalized tower set) gives a combinatorial characterization of the primary decomposition of the arithmetically Cohen-Macaulay squarefree monomial ideals
Can Activity Worthwhileness Explain OCB-I Change? The Mediating Role of Positive Emotions
The competitiveness of today's markets requires employees to do more than is formally expected from them by collaborating with others to benefit the organization (e.g., organizational citizenship behavior focused on individuals, OCB-I). Based on the idea that eudaimonic wellbeing positively influences OCB-I, and considering that positive emotions lead to optimal functioning and important work outcomes, this study analyzes the mediating role of positive emotions in the relationship between activity worthwhileness and OCB-I. Results of hierarchical regressions in a two-wave longitudinal study with a sample of 108 white collar employees show that activity worthwhileness indirectly (but not directly) explains change in OCB-I through positive emotions. Therefore, when it comes to improving performance in the workplace, investment in both hedonic and eudaimonic wellbeing contributes to more effectively benefitting both employees and organizations
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