412 research outputs found
Topology in CP(N-1) models: a critical comparison of different cooling techniques
Various cooling methods, including a recently introduced one which smoothes
out only quantum fluctuations larger than a given threshold, are applied to the
study of topology in 2d CP(N-1) models. A critical comparison of their
properties is performed.Comment: Poster at LATTICE99(Topology and confinement), 3 pages, 5 eps
figures, uses espcrc2.st
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
The spin content of the proton in quenched QCD
We present preliminary results on the proton spin structure function at zero
momentum, in the quenched approximation. Our calculation makes use of a
nonperturbative means of determining the multiplicative renormalization of the
topological charge density.Comment: REVTEX, 6 pages, 1 PS figure attached. Pisa preprint IFUP-TH-14/9
Renormalization and topological susceptibility on the lattice: SU(2) Yang-Mills theory
The renormalization functions involved in the determination of the
topological susceptibility in the SU(2) lattice gauge theory are extracted by
direct measurements, without relying on perturbation theory. The determination
exploits the phenomenon of critical slowing down to allow the separation of
perturbative and non-perturbative effects. The results are in good agreement
with perturbative computations.Comment: 12 pages + 4 figures (PostScript); report no. IFUP-TH 10/9
Topology in 2D CP**(N-1) models on the lattice: a critical comparison of different cooling techniques
Two-dimensional CP**(N-1) models are used to compare the behavior of
different cooling techniques on the lattice. Cooling is one of the most
frequently used tools to study on the lattice the topological properties of the
vacuum of a field theory. We show that different cooling methods behave in an
equivalent way. To see this we apply the cooling methods on classical
instantonic configurations and on configurations of the thermal equilibrium
ensemble. We also calculate the topological susceptibility by using the cooling
technique.Comment: 24 pages, 10 figures (from 16 eps files
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
Field-strength correlators in gauge theory
We measure field-strength and their correlators in presence of a static q \bar q pair by numerical simulations. We give an interpretation of these data in terms of quadratic and quartic cumulants
Study of luminescence properties in lapis lazuli diopside crystals during micro-IBIL measurements
Energy States of Colored Particle in a Chromomagnetic Field
The unitary transformation, which diagonalizes squared Dirac equation in a
constant chromomagnetic field is found. Applying this transformation, we find
the eigenfunctions of diagonalized Hamiltonian, that describe the states with
definite value of energy and call them energy states. It is pointed out that,
the energy states are determined by the color interaction term of the particle
with the background chromofield and this term is responsible for the splitting
of the energy spectrum.
We construct supercharge operators for the diagonal Hamiltonian, that ensure
the superpartner property of the energy states.Comment: 25 pages, some calculation details have been removed, typos correcte
Dual superconductivity in the SU(2) pure gauge vacuum: a lattice study
We investigate the dual superconductivity hypothesis in pure SU(2) lattice
gauge theory. We focus on the dual Meissner effect by analyzing the
distribution of the color fields due to a static quark-antiquark pair. We find
evidence of the dual Meissner effect both in the maximally Abelian gauge and
without gauge fixing. We measure the London penetration length. Our results
suggest that the London penetration length is a physical gauge-invariant
quantity. We put out a simple relation between the penetration length and the
square root of the string tension. We find that our extimation is quite close
to the extrapolated continuum limit available in the literature. A remarkable
consequence of our study is that an effective Abelian theory can account for
the long range properties of the SU(2) confining vacuum.Comment: 38 pages, uuencoded compressed (using GNU's gzip) tar file containing
1 LaTeX2e file (to be processed 3 times) + 16 encapsulated Postscript
figures. A full Postscript version of this paper is available at
http://www.ba.infn.it/disk$gruppo_4/cosmai/www/papers/195-95.P
- âŠ