1,773 research outputs found
Correlation functions of disorder operators in massive ghost theories
The two-dimensional ghost systems with negative integral central charge
received much attention in the last years for their role in a number of
applications and in connection with logarithmic conformal field theory. We
consider the free massive bosonic and fermionic ghost systems and concentrate
on the non-trivial sectors containing the disorder operators. A unified
analysis of the correlation functions of such operators can be performed for
ghosts and ordinary complex bosons and fermions. It turns out that these
correlators depend only on the statistics although the scaling dimensions of
the disorder operators change when going from the ordinary to the ghost case.
As known from the study of the ordinary case, the bosonic and fermionic
correlation functions are the inverse of each other and are exactly expressible
through the solution of a non-linear differential equation.Comment: 8 pages, late
Harnack and pointwise estimates for degenerate or singular parabolic equations
In this paper we give both an historical and technical overview of the theory
of Harnack inequalities for nonlinear parabolic equations in divergence form.
We start reviewing the elliptic case with some of its variants and geometrical
consequences. The linear parabolic Harnack inequality of Moser is discussed
extensively, together with its link to two-sided kernel estimates and to the
Li-Yau differential Harnack inequality. Then we overview the more recent
developements of the theory for nonlinear degenerate/singular equations,
highlighting the differences with the quadratic case and introducing the
so-called intrinsic Harnack inequalities. Finally, we provide complete proofs
of the Harnack inequalities in some paramount case to introduce the reader to
the expansion of positivity method.Comment: Survey paper, 50 pages, 5 figures. Comments welcom
Subsidence monitoring system for offshore applications: technology scouting and feasibility studies
Because of concern about possible impacts of hydrocarbon production
activities on coastal-area environments and infrastructures, new hydrocarbon
offshore development projects in Italy must submit a monitoring plan to
Italian authorities to measure and analyse real-time subsidence evolution.
The general geological context, where the main offshore Adriatic fields are
located, is represented by young unconsolidated terrigenous sediments. In
such geological environments, sea floor subsidence, caused by hydrocarbon
extraction, is quite probable. Though many tools are available for subsidence
monitoring onshore, few are available for offshore monitoring. To fill the
gap ENI (Ente Nazionale Idrocarburi) started a research program, principally
in collaboration with three companies, to generate a monitoring system tool
to measure seafloor subsidence. The tool, according to ENI design
technical-specification, would be a robust long pipeline or cable, with a
variable or constant outside diameter (less than or equal to 100 mm)
and interval spaced measuring points. The design specifications for the first
prototype were: to detect 1 mm altitude variation, to work up to 100 m
water depth and investigation length of 3 km. Advanced feasibility
studies have been carried out with: Fugro Geoservices B.V. (Netherlands),
D'Appolonia (Italy), Agisco (Italy).
Five design (using three fundamental measurements concepts and five
measurement tools) were explored: cable shape changes measured by cable
strain using fiber optics (Fugro); cable inclination measured using
tiltmeters (D'Appolonia) and measured using fiber optics (Fugro); and
internal cable altitude-dependent pressure changes measured using fiber
optics (Fugro) and measured using pressure transducers at discrete intervals
along the hydraulic system (Agisco). Each design tool was analysed and a rank
ordering of preferences was performed. The third method (measurement of
pressure changes), with the solution proposed by Agisco, was deemed most
feasible. Agisco is building the first prototype of the tool to be installed
in an offshore field in the next few years.
This paper describes design of instruments from the three companies to
satisfy the design specification
Subsidence monitoring system for offshore applications: technology scouting and feasibility studies
Abstract. Because of concern about possible impacts of hydrocarbon production activities on coastal-area environments and infrastructures, new hydrocarbon offshore development projects in Italy must submit a monitoring plan to Italian authorities to measure and analyse real-time subsidence evolution. The general geological context, where the main offshore Adriatic fields are located, is represented by young unconsolidated terrigenous sediments. In such geological environments, sea floor subsidence, caused by hydrocarbon extraction, is quite probable. Though many tools are available for subsidence monitoring onshore, few are available for offshore monitoring. To fill the gap ENI (Ente Nazionale Idrocarburi) started a research program, principally in collaboration with three companies, to generate a monitoring system tool to measure seafloor subsidence. The tool, according to ENI design technical-specification, would be a robust long pipeline or cable, with a variable or constant outside diameter (less than or equal to 100 mm) and interval spaced measuring points. The design specifications for the first prototype were: to detect 1 mm altitude variation, to work up to 100 m water depth and investigation length of 3 km. Advanced feasibility studies have been carried out with: Fugro Geoservices B.V. (Netherlands), D'Appolonia (Italy), Agisco (Italy). Five design (using three fundamental measurements concepts and five measurement tools) were explored: cable shape changes measured by cable strain using fiber optics (Fugro); cable inclination measured using tiltmeters (D'Appolonia) and measured using fiber optics (Fugro); and internal cable altitude-dependent pressure changes measured using fiber optics (Fugro) and measured using pressure transducers at discrete intervals along the hydraulic system (Agisco). Each design tool was analysed and a rank ordering of preferences was performed. The third method (measurement of pressure changes), with the solution proposed by Agisco, was deemed most feasible. Agisco is building the first prototype of the tool to be installed in an offshore field in the next few years. This paper describes design of instruments from the three companies to satisfy the design specification.</p
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