706 research outputs found
Spin-1 gravitational waves. Theoretical and experimental aspects
Exact solutions of Einstein field equations invariant for a non-Abelian
2-dimensional Lie algebra of Killing fields are described. Physical properties
of these gravitational fields are studied, their wave character is checked by
making use of covariant criteria and the observable effects of such waves are
outlined. The possibility of detection of these waves with modern detectors,
spherical resonant antennas in particular, is sketched
Effect of the Gribov horizon on the Polyakov loop and vice versa
We consider finite temperature SU(2) gauge theory in the continuum
formulation, which necessitates the choice of a gauge fixing. Choosing the
Landau gauge, the existing gauge copies are taken into account by means of the
Gribov-Zwanziger (GZ) quantization scheme, which entails the introduction of a
dynamical mass scale (Gribov mass) directly influencing the Green functions of
the theory. Here, we determine simultaneously the Polyakov loop (vacuum
expectation value) and Gribov mass in terms of temperature, by minimizing the
vacuum energy w.r.t. the Polyakov loop parameter and solving the Gribov gap
equation. Inspired by the Casimir energy-style of computation, we illustrate
the usage of Zeta function regularization in finite temperature calculations.
Our main result is that the Gribov mass directly feels the deconfinement
transition, visible from a cusp occurring at the same temperature where the
Polyakov loop becomes nonzero. In this exploratory work we mainly restrict
ourselves to the original Gribov-Zwanziger quantization procedure in order to
illustrate the approach and the potential direct link between the vacuum
structure of the theory (dynamical mass scales) and (de)confinement. We also
present a first look at the critical temperature obtained from the Refined
Gribov-Zwanziger approach. Finally, a particular problem for the pressure at
low temperatures is reported.Comment: 19 pages, 8 .pdf figures. v2: extended section 3 + extra references;
version accepted for publication in EPJ
Double non-perturbative gluon exchange: an update on the soft Pomeron contribution to pp scattering
We employ a set of recent, theoretically motivated, fits to non-perturbative
unquenched gluon propagators to check in how far double gluon exchange can be
used to describe the soft sector of pp scattering data (total and differential
cross section). In particular, we use the refined Gribov--Zwanziger gluon
propagator (as arising from dealing with the Gribov gauge fixing ambiguity) and
the massive Cornwall-type gluon propagator (as motivated from Dyson-Schwinger
equations) in conjunction with a perturbative quark-gluon vertex, next to a
model based on the non-perturbative quark-gluon Maris-Tandy vertex, popular
from Bethe-Salpeter descriptions of hadronic bound states. We compare the cross
sections arising from these models with "older" ISR and more recent TOTEM and
ATLAS data. The lower the value of total energy \sqrt{s}, the better the
results appear to be.Comment: 14 pages, 8 .pdf figures. To appear in Phys.Rev.
Education in Soil Science: the Italian approach
The Italian Society of Soil Science (SISS) was founded in Florence on February 18th, 1952.
It is an association legally acknowledged by Decree of the President of the Italian Republic in February 1957.
The Society is member of the International Union of Soil Sciences (IUSS) of the European Confederation of Soil
Science Societies (ECSSS) and collaborates with several companies, institutions and organizations having similar
objectives or policy aspects.
SISS promotes progress, coordination and dissemination of soil science and its applications encouraging relationships
and collaborations among soil lovers.
Within the SISS there are Working Groups and Technical Committees for specific issues of interest. In particular:
\u2022 the Working Group on Pedotechniques;
\u2022 the Working Group on Hydromorphic and Subaqueous Soils and
\u2022 the Technical Committee for Soil Education and Public Awareness.
In this communication we wish to stress the activities developed since its foundation by SISS to spread soil
awareness and education in Italy through this last Technical Committee, focusing also the aspect concerning grants
for young graduates and PhD graduates to stimulate the involvement of young people in the field of soil science
Analytic multi-Baryonic solutions in the SU(N)-Skyrme model at finite density
5siopenWe construct explicit analytic solutions of the SU(N)-Skyrme model (for generic N) suitable to describe different phases of nuclear pasta at finite volume in (3 + 1) dimensions. The first type are crystals of Baryonic tubes (nuclear spaghetti) while the second type are smooth Baryonic layers (nuclear lasagna). Both, the ansatz for the spaghetti and the ansatz for the lasagna phases, reduce the complete set of Skyrme field equations to just one integrable equation for the profile within sectors of arbitrary high topological charge. We compute explicitly the total energy of both configurations in terms of the flavor number, the density and the Baryonic charge. Remarkably, our analytic results allow to compare explicitly the physical properties of nuclear spaghetti and lasagna phases. Our construction shows explicitly that, at lower densities, configurations with N = 2 light flavors are favored while, at higher densities, configurations with N = 3 are favored. Our construction also proves that in the high density regime (but still well within the range of validity of the Skyrme model) the lasagna configurations are favored while at low density the spaghetti configurations are favored. Moreover, the integrability property of the present configurations is not spoiled by the inclusion of the subleading corrections to the Skyrme model arising in the ’t Hooft expansion. Finally, we briefly discuss the large N limit of our configurations.openCacciatori, Sergio L.; Canfora, Fabrizio; Lagos, Marcela; Muscolino, Federica; Vera, AldoCacciatori, Sergio L.; Canfora, Fabrizio; Lagos, Marcela; Muscolino, Federica; Vera, Ald
Cooking pasta with Lie groups
We extend the (gauged) Skyrme model to the case in which the global isospin group (which usually is taken to be SU(N)) is a generic compact connected Lie group G. We analyze the corresponding field equations in (3+1) dimensions from a group theory point of view. Several solutions can be constructed analytically and are determined by the embeddings of three dimensional simple Lie groups into G, in a generic irreducible representation. These solutions represent the so-called nuclear pasta state configurations of nuclear matter at low energy. We employ the Dynkin explicit classification of all three dimensional Lie subgroups of exceptional Lie group to classify all such solutions in the case G is an exceptional simple Lie group, and give all ingredients to construct them explicitly. As an example, we construct the explicit solutions for G=G2. We then extend our ansatz to include the minimal coupling of the Skyrme field to a U(1) gauge field. We extend the definition of the topological charge to this case and then concentrate our attention to the electromagnetic case. After imposing a \u201cfree force condition\u201d on the gauge field, the complete set of coupled field equations corresponding to the gauged Skyrme model minimally coupled to an Abelian gauge field is reduced to just one linear ODE keeping alive the topological charge. We discuss the cases in which such ODE belongs to the (Whittaker-)Hill and Mathieu types
Machine-Readable Privacy Certificates for Services
Privacy-aware processing of personal data on the web of services requires
managing a number of issues arising both from the technical and the legal
domain. Several approaches have been proposed to matching privacy requirements
(on the clients side) and privacy guarantees (on the service provider side).
Still, the assurance of effective data protection (when possible) relies on
substantial human effort and exposes organizations to significant
(non-)compliance risks. In this paper we put forward the idea that a privacy
certification scheme producing and managing machine-readable artifacts in the
form of privacy certificates can play an important role towards the solution of
this problem. Digital privacy certificates represent the reasons why a privacy
property holds for a service and describe the privacy measures supporting it.
Also, privacy certificates can be used to automatically select services whose
certificates match the client policies (privacy requirements).
Our proposal relies on an evolution of the conceptual model developed in the
Assert4Soa project and on a certificate format specifically tailored to
represent privacy properties. To validate our approach, we present a worked-out
instance showing how privacy property Retention-based unlinkability can be
certified for a banking financial service.Comment: 20 pages, 6 figure
Spatial microbial community structure and biodiversity analysis in "extreme" hypersaline soils of a semiarid Mediterranean area
In recent years specific attention has been paid on the biotechnological potential of microorganisms in extreme soils, in particular in saline soils. Salinity is one of the most widespread soil degradation processes on the Earth, and saline soils can be defined as extreme soils or border line habitats in which several factors, as high salt content, may limit the growth of organisms. In this study, the physical, chemical and microbiological soil properties were investigated in the shallower horizon of natural salt-affected soils in Sicily (Italy). The main aim of the research was to evaluate the structure and diversity of bacterial and archaeal communities by terminal-restriction fragment length polymorphism (T-RFLP) according to arbitrary different classes of vegetation and salt crust cover in soils. Furthermore, the structure of microbial communities was assessed considering the heterogeneity of physical-chemical properties of the habitat under investigation, as a function of vegetation, crust cover, and salinity classes. The results provided information on the type of distribution of different microbial community composition and diversity as a function of both vegetation and crust cover as well as salinity classes. In particular, the archaeal community showed a richness and diversity significantly affected by the spatial gradients of soil salinity, conversely, the bacterial one showed a decreasing trend with increasing gradient of soil salinity. The T-RFLP cluster analysis showed the formation of two groups for both bacterial and archaeal community, significantly (. p<. 0.05) influenced by sand and silt content, electrical conductivity (EC. e), vegetation cover percentage, salt crust and for by texture composition. In particular, the discriminant analysis obtained for the different salt crust classes for archaeal community stressed the membership of one of the two clusters to the class with the lower salt crust percentage (0-40%)
Distribution patterns of fungi and bacteria in saline soils
Saline soils are environments characterized by uneven temporal and spatial water distribution
and localized high concentrations of salts. Spatial distribution patterns of fungi and bacteria in
saline soils, and the link between microbial community dynamics and salts accumulation are
critical issues throughout the world (Ettema, Wardle 2002).
This study was focused on spatial distribution patterns of soil fungi and bacteria in a saline soil
located in Piana del Signore (Gela, Italy) where some ecological variables acted as shaping
factors in aboveground and belowground communities distribution. Bacterial, archaeal, and
fungal communities diversity and distribution in ten soil sites (A horizons, 0-10cm), were
characterized by 16S rDNA genes with T-RFLP method. Pyrosequencing-based analysis of the
V2-V3 16S rRNA gene region was performed to characterize the sites on the basis of bacterial
groups distribution, diversity and assemblage. To better investigate the ecological niches of
some of the main culturable species of this environment, it was carried out the isolation and
identification of the fungal flora from soil, using Warcup plating within two different salt
concentrations (NaCl 5% and 15%), combined with a metabolic screening of some
representative isolates (Di Lonardo et al., 2013).
A natural gradient of soil salinity shaped the distribution of microbial species in the environment.
The different concentration of salt (NaCl), and calcium sulfate (Ca2SO4) in soil influenced the
structure and distribution of the microbial communities even when comparing neighboring areas
within a 50 m scale.
Some bacterial phyla, together with some fungal species, appeared spread in the whole area,
independently of the salinity gradient, thus highlighting the presence of organisms with a very
different survival strategy in such an extreme environment.
In conclusion, the organization and diversity of microbial taxa at a spatial scale reflected the
scales of heterogeneity of physical and chemical properties of the habitat under investigation
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