4,361 research outputs found
Support for the value 5/2 for the spin glass lower critical dimension at zero magnetic field
We study numerically various properties of the free energy barriers in the
Edwards-Anderson model of spin glasses in the low-temperature region both in
three and four spatial dimensions. In particular, we investigated the
dependence of height of free energy barriers on system size and on the distance
between the initial and final states (i.e. the overlap distance). A related
quantity is the distribution of large local fluctuations of the overlap in
large three-dimensional samples at equilibrium. Our results for both quantities
(barriers and large deviations) are in agreement with the prediction obtained
in the framework of mean field theory. In addition, our result supports
as the lower critical dimension for the model.Comment: 11 pages, 4 figures. To appear in PNA
Public libraries in the social accountability of local administrations
This work represents a first reflection with respect to certain issues such as:
- the importance of social reporting, and in particular the use of the social accountability for
public libraries Italian in order to communicate more effectively on the outside their values; being
generally recognized the effectiveness of the balance for the purposes of reporting, there does not
seem to be any reasons why libraries should not take advantage of such an instrument;
- a higher visibility of public libraries, perceived not only by the professionals in the industry,
but also by the public administrations, in order to make more significant component the local
librarian within the administrations of reference, as agency for change in the community and
therefore of necessary service;
- analysis of best practices to recognized today, in order to highlight the methodologies and
the main features of some excellent Italian examples;
- Proposal for a methodology of investigation, through which retrieve the information
necessary for the preparation of a social accountability, based on standard can also be used in scope
librarian, as ISO 2789, 11620, 16489
A numerical study of planar arrays of correlated spin islands
We present our analysis of a system of interacting islands of XY spins on a
triangular lattice that has been introduced a few years ago by Eley et al. to
account for the phenomenology in experiments on tunable arrays of proximity
coupled long superconductor-normal metal-superconductor junctions. The main
features of the model are the separation of a local and a global interaction
energy scale and the mesoscopic character of the spin islands. Upon lowering
the temperature the model undergoes two crossovers corresponding to an
increasing phase coherence on a single island and to the onset of global
coherence across the array; the latter is a thermodynamical phase transition in
the Ising universality class. The dependence of the second transition on the
island edge-to-edge spacing is related to the proximity-effect of the coupling
constant.Comment: 6 pages, 5 figures, accepted for publication in EPJ
MIOCENE QUANTITATIVE CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY FROM SOUTHERN APENNINES FOREDEEP DEPOSITS AND MEDITERRANEAN DSDP SITE 372
A quantitative biostratigraphic study based on calcareous nannofossil assemblages was carried out in nine Miocene calcareous and siliciclastic foredeep sections, cropping out in the outer part of the Southern Apennines and generally ascribed to the external Irpinian units. Several biozonal events were recognised by means of quantitative analyses, according to the biostratigraphic schemes of Fornaciari & Rio (1996) and Fornaciari et al. (1996) for the lower and middle Miocene and of Theodoridis (1984) for the upper Miocene. In the lower and middle Miocene interval some biohorizons such as the first common occurrence of Helicosphaera walbersdorfensis and last common occurrence of Calcidiscus premacintyrei are not always detectable in the studied sections and the first common occurrence of Calcidiscus macintyrei appears to be a better biohorizon in the MNN6b/7 than the last common occurrence of C. premacintyrei. New data on abundance patterns of selected calcareous nannofossils have been collected, thus improving the biostratigraphic resolution of the zonal schemes: a paracme interval of small Reticulofenestra pseudoumbilicus was noted within Zone MNN4b and MNN5a; the beginning and the end of the paracme are useful events in the studied sections for stratigraphic correlations. Moreover the occurrence of R. pseudoumbilicus has been recorded from Zone MNN2b on upwards, fairly below the FCO of the species that defines the base of Zone MNN6b. The distributions observed in the on-land sections are consistent with those recognised in DSDP Site 372 located in the western Mediterranean Sea, confirming their potential biostratigraphic utility within the Mediterranean region. 
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