1,604 research outputs found
Cylindrical Wigner Measures
No full textIn this paper we study the semiclassical behavior of quantum states acting on the C*-algebra of canonical commutation relations, from a general perspective. The aim is to provide a unified and flexible approach to the semiclassical analysis of bosonic systems. We also give a detailed overview of possible applications of this approach to mathematical problems of both axiomatic relativistic quantum field theories and nonrelativistic many body systems. If the theory has infinitely many degrees of freedom, the set of Wigner measures, i.e. the classical counterpart of the set of quantum states, coincides with the set of all cylindrical measures acting on the algebraic dual of the space of test functions for the field, and this reveals a very rich semiclassical structure compared to the finite-dimensional case. We characterize the cylindrical Wigner measures and the a priori properties they inherit from the corresponding quantum states
Concentration of cylindrical Wigner measures
No full text In this paper, we aim to characterize the cylindrical Wigner measures associated to regular quantum states in the Weyl C*-algebra of canonical commutation relations. In particular, we provide conditions at the quantum level sufficient to prove the concentration of all the corresponding cylindrical Wigner measures as Radon measures on suitable topological vector spaces. The analysis is motivated by variational and dynamical problems in the semiclassical study of bosonic quantum field theories. </jats:p
Major inter-annual variations in microbial dynamics in the Gulf of Trieste (Northern Adriatic Sea) and their ecosystem implications.
No full textComprehensive, multi-year studies of microbial processes in an ecosystem context are important in understanding microbial regulation of ecosystem structure, function and variability. A 3 yr study on microbial community was carried out in a coastal area in the northern Adriatic Sea (Gulf of Trieste). It is a semi-enclosed shallow system, mostly controlled by pulsed external inputs, which determine a high variability of plankton communities. Samples were collected monthly at 2 stations from January 1999 to December 2001. Data illustrate remarkable inter- and intra-annual variability in parameters relevant to carbon biogeochemistry and ecosystem energy flow patterns. Integrated primary production (PP; 135 g C m–2 yr–1) in 1999 tripled (414 g C m–2 yr–1) in 2000, returning to a low level (150 g C m–2 yr–1) in 2001. Bacterial production (by 3H-leucine incorporation) accounted, on average, for 35.3% of net PP in 1999, 9.5% in 2000 and 29.4% in 2001. Flux into the microbial loop via bacteria
Debris flow risk assessment in the aguas calientes village (cusco, perù )
No full textIn this paper a landslide risk assessment in the area of Aguas Calientes village (Machu Picchu, Cusco, Perù) is applied. A study carried out into a capacity building project (FORGEO) was focused on localising source areas and runout of debris flows triggered by heavy rainfall in the Alcamayo catchment and on assessing debris flow intensity. Starting from an inventory of several previous debris flows occurred in the area, an evaluation of the local predisposing parameters to these events was used as input for susceptibility and hazard GIS based analysis. Empirical formulas reported in the literature were adapted to the research area context to estimate the runout of potential events. An analysis of exposure of structures and infrastructures was also performed during the project and high residual risk conditions were found for the Aguas Calientes village. These results may aid local authorities involved in land use planning, management policies and landslide risk reduction. © Springer-Verlag Berlin Heidelberg 2013
Landslide hazard assessment project in the Messina municipality area (Sicily, Italy)
No full textIn the last 4 years Messina Municipality has been hit by rainfall events that triggered a great number of debris flows. Due to 2009 event ENEA started landslide hazard researches in the south of the Municipality. Messina territory (210 km2) is located at the NE culmination of Peloritani Range, formed by seven metamorphic Units covered by late orogenic terrigenous formations and by Plio-Pleistocene deposits. Steep slopes lead to high erosion rates, that increased in last years because of intense rainfall. The first step of the hazard assessment method is an inventory of landslides, followed by the detection of landslide parameters. Through GIS analysis of this parameters landslide susceptibility is assessed. Geomorphological analysis allows evaluating the runout and energy of the future events. Rainfalls data analysis allows definition of triggering threshold for the area. These parameters will be tested in a test site field for the measurement of soil saturation. © Springer-Verlag Berlin Heidelberg 2013
Geomorphological processes and cultural heritage of Maca and Lari Villages: An opportunity for sustainable tourism development in the Colca Valley (Province of Caylloma, Arequipa, South Perù)
No full textFamous because of its deepness and beauty of the landscape, Colca Valley is one of the main places of tourist attraction in Peru. Maca and Lari are two of the valley villages, facing each other on opposite banks of the Colca River. High slope energy is only one of the factors causing a widespread landslide activity, triggered primarily by seismic activity. A study carried out into a capacity building project (FORGEO) was focused on mapping landslide source areas in the territory of both the villages. Starting from an inventory of several previous phenomena occurred in the area, an evaluation of the local predisposing parameters to these events was used as input for susceptibility and hazard GIS based analysis. An assessment of exposure of structures and infrastructures was also performed, detecting residual risk condition in the territories of both villages. The role of rainfall and groundwater in local landslide processes is stressed in this paper as well as the effectiveness of an adequate water management in landslide risk reduction and sustainable land use planning. © Springer-Verlag Berlin Heidelberg 2013
Author response to: Survival after active surveillance versus upfront surgery for incidental small pancreatic neuroendocrine tumours
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Low cost curvature correction of bandgap references for integrated sensors
No full textDue to increasing demands on the accuracy of integrated sensors, it is very important to improve the accuracy of bandgap voltage references. Since the second order non linearity of the function V-BE(T) is generally the main limit to the accuracy of calibrated bandgap voltage references, several methods for the curvature-correction of V-BE(T) have been reported in literature; unfortunately these methods require quite complex circuitry. In this paper we investigate a low cost curvature correction method, consisting in taking advantage of the temperature dependence of integrated resistors and in using PTAT/R collector currents; furthermore we introduce two new circuit topologies which permit to take full advantage of this approach in spite of technological limitations. (C) 2004 Elsevier B.V All rights reserved
The Dilute Fermi Gas via Bogoliubov Theory
No full textWe study the ground state properties of interacting Fermi gases in the dilute regime, in three dimensions. We compute the ground state energy of the system, for positive interaction potentials. We recover a well-known expression for the ground state energy at second order in the particle density, which depends on the interaction potential only via its scattering length. The first proof of this result has been given by Lieb, Seiringer and Solovej (Phys Rev A 71:053605, 2005). In this paper, we give a new derivation of this formula, using a different method; it is inspired by Bogoliubov theory, and it makes use of the almost-bosonic nature of the low-energy excitations of the systems. With respect to previous work, our result applies to a more regular class of interaction potentials, but it comes with improved error estimates on the ground state energy asymptotics in the density
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