291 research outputs found
A strong-coupling analysis of two-dimensional O(N) sigma models with on square, triangular and honeycomb lattices
Recently-generated long strong-coupling series for the two-point Green's
functions of asymptotically free lattice models are
analyzed, focusing on the evaluation of dimensionless renormalization-group
invariant ratios of physical quantities and applying resummation techniques to
series in the inverse temperature and in the energy . Square,
triangular, and honeycomb lattices are considered, as a test of universality
and in order to estimate systematic errors. Large- solutions are carefully
studied in order to establish benchmarks for series coefficients and
resummations. Scaling and universality are verified. All invariant ratios
related to the large-distance properties of the two-point functions vary
monotonically with , departing from their large- values only by a few per
mille even down to .Comment: 53 pages (incl. 5 figures), tar/gzip/uuencode, REVTEX + psfi
LAFOSSAITE E DIMORPHITE: DUE NUOVE SPECIE PER IL VESUVIO
La presenza di lafossaite, la cui località-tipo è il cratere de La Fossa all’Isola di Vulcano (Roberts et al., 2006),
è stata rilevata su due piccoli campioni provenienti dal Vesuvio (eruzione del 1906), facenti parte di una
vecchia collezione già appartenuta all’“Istituto Geomineralogico Italiano”, una società attiva negli anni ’20
del secolo scorso. Nei campioni esaminati la lafossaite forma minuscoli aggregati di cristalli cubici incolori,
associati a realgar, dimorphite, anidrite e a un cloruro di tallio e arsenico attualmente in fase di studio. La
dimorphite, la cui località-tipo è la Solfatara di Pozzuoli, fu descritta per la prima volta da Scacchi (1849) ed è
associata a realgar e mascagnite
Parity effects in the scaling of block entanglement in gapless spin chains
We consider the Renyi alpha-entropies for Luttinger liquids (LL). For large
block lengths l these are known to grow like ln l. We show that there are
subleading terms that oscillate with frequency 2k_F (the Fermi wave number of
the LL) and exhibit a universal power-law decay with l. The new critical
exponent is equal to K/(2 alpha), where K is the LL parameter. We present
numerical results for the anisotropic XXZ model and the full analytic solution
for the free fermion (XX) point.Comment: 4 pages, 5 figures. Final version accepted in PR
Nuove specie minerali al Somma-Vesuvio: wulfenite
To the 247 species, of which 20 are doubtful, occurring at the Somma-Vesuvius volcanic complex, after the
recent updating of the fluoro-edenite (despite the collecting ban) it has to be added the identification of a
new common species, never occurred before. A sample belonging to Luigi Chiappino, found in 1989 at
San Vito quarry, Ercolano, Napoli, was analyzed through SEM-EDX and the analysis identified the wulfenite
on massive galena, as millimetrical, bipyramidal crystals, resinous, of yellow-orange colour, associated with
calcite, cerussite and sphalerite
Ritrovamento di Atacamite in cristalli al Vesuvio
In the small vacuoles of an older lava from one
of the quarries of Villa Inglese (Torre del Greco,
Napoli) atacamite as crystalline have been
discovered. This is a rare event in this volcanic
complex
Nuovo ritrovamento di corindone al Monte Somma
After the occurrence described by of Balassone et al. (2001), a second finding of corundum, Al2O3, occurred
in a small fragment of carbonatic rock at San Vito quarry, Ercolano, Napoli, Campania. It is the section
of a 2 mm bluish crystal. The identification was done through SEM-EDX analysis at 30 kV excitation
Vulcano : tre secoli di mineralogia
Va ricordato, con immenso motivo di orgoglio e senza pecca di retorica, che il sito delle isole Eolie è “un
eccezionale esempio dell’attività di costruzione e distruzione di isole operata dal vulcanesimo e testimoniano
un fenomeno vulcanico tuttora in corso”, rivestendo “una importanza internazionale per la vulcanologia” e
che, “studiate già a partire dal XVIII secolo, hanno fornito alle opere di vulcanologia la descrizione di due tipi
di eruzione (vulcaniana e stromboliana)”, rappresentando da oltre due secoli, una tappa importante nella
formazione di tutti i geologi: questa la motivazione suggellata dell’Unesco per il prestigioso riconoscimento
attribuito all’arcipelago di “Patrimonio dell’Umanità”..
Nuove specie minerali al Somma-Vesuvio: fluoro-edenite
Despite the impossibility to make mineralogical researches on the field, the volcanic complex of Monte
Somma-Vesuvius keeps surprising with new findings of mineral species for that locality. In an “old” sample
belonging to Domenico Preite, picked up at Le Novelle quarry, Ercolano, Napoli, thanks to EDX and micro-
FTIR analysis the fluoro-edenite was identified. This is the second Italian finding for the species after the one
of the Etnean type locality of Monte Calvario, Biancavilla, Catania (Gianfagna & Oberti, 2001)
Critical renormalized coupling constants in the symmetric phase of the Ising models
Using a novel finite size scaling Monte Carlo method, we calculate the four,
six and eight point renormalized coupling constants defined at zero momentum in
the symmetric phase of the three dimensional Ising system. The results of the
2D Ising system that were directly measured are also reported. Our values of
the six and eight point coupling constants are significantly different from
those obtained from other methods.Comment: 7 pages, 2 figure
Two dimensional SU(N)xSU(N) Chiral Models on the Lattice (II): the Green's Function
Analytical and numerical methods are applied to principal chiral models on a
two-dimensional lattice and their predictions are tested and compared. New
techniques for the strong coupling expansion of SU(N) models are developed and
applied to the evaluation of the two-point correlation function. The
momentum-space lattice propagator is constructed with precision O(\beta^{10})
and an evaluation of the correlation length is obtained for several different
definitions. Three-loop weak coupling contributions to the internal energy and
to the lattice and functions are evaluated for all N, and the
effect of adopting the ``energy'' definition of temperature is computed with
the same precision. Renormalization-group improved predictions for the
two-point Green's function in the weak coupling ( continuum ) regime are
obtained and successfully compared with Monte Carlo data. We find that strong
coupling is predictive up to a point where asymptotic scaling in the energy
scheme is observed. Continuum physics is insensitive to the effects of the
large N phase transition occurring in the lattice model. Universality in N is
already well established for and the large N physics is well
described by a ``hadronization'' picture.Comment: Revtex, 37 pages, 16 figures available on request by FAX or mai
- …