7,520 research outputs found
Self modulated dynamics of a relativistic charged particle beam in plasma wake field excitation
Self modulated dynamics of a relativistic charged particle beam is reviewed
within the context of the theory of plasma wake field excitation. The
self-consistent description of the beam dynamics is provided by coupling the
Vlasov equation with a Poisson-type equation relating the plasma wake potential
to the beam density. An analysis of the beam envelope self-modulation is then
carried out and the criteria for the occurrence of the instability are
discussed thereby.Comment: This is a 10 pages manuscript which contain 4 figures. This
manuscript is recently submitted in 'Nuclear Instruments and Methods in
Physics Research Section A' as a proceeding of the conference 'EAAC 2015
Classical and Quantum-like approaches to Charged-Particle Fluids in a Quadrupole
A classical description of the dynamics of a dissipative charged-particle
fluid in a quadrupole-like device is developed. It is shown that the set of the
classical fluid equations contains the same information as a complex function
satisfying a Schrodinger-like equation in which Planck's constant is replaced
by the time-varying emittance, which is related to the time-varying temperature
of the fluid. The squared modulus and the gradient of the phase of this complex
function are proportional to the fluid density and to the current velocity,
respectively. Within this framework, the dynamics of an electron bunch in a
storage ring in the presence of radiation damping and quantum-excitation is
recovered. Furthermore, both standard and generalized (including dissipation)
coherent states that may be associated with the classical particle fluids are
fully described in terms of the above formalism.Comment: LaTex, to appear in Physica Script
Specifying and Analysing SOC Applications with COWS
COWS is a recently defined process calculus for specifying and combining service-oriented applications, while modelling their dynamic behaviour. Since its introduction, a number of methods and tools have been devised to analyse COWS specifications, like e.g. a type system to check confidentiality properties, a logic and a model checker to express and check functional properties of services. In this paper, by means of a case study in the area of automotive systems, we demonstrate that COWS, with some mild linguistic additions, can model all the phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, orchestration, deployment, reconfiguration and execution. We also provide a flavour of the properties that can be analysed by using the tools mentioned above
Entropic uncertainty relations for electromagnetic beams
The symplectic tomograms of 2D Hermite--Gauss beams are found and expressed
in terms of the Hermite polynomials squared. It is shown that measurements of
optical-field intensities may be used to determine the tomograms of
electromagnetic-radiation modes. Furthermore, entropic uncertainty relations
associated with these tomograms are found and applied to establish the
compatibility conditions of the the field profile properties with
Hermite--Gauss beam description. Numerical evaluations for some Hermite--Gauss
modes illustrating the corresponding entropic uncertainty relations are finally
given.Comment: Invited talk at the XV Central European Workshop on Quantum Optics
(Belgrade, Serbia, 30 May -- 3 June 2008), to appear in Physica Scripta
Towards a Formal Verification Methodology for Collective Robotic Systems
We introduce a UML-based notation for graphically modeling
systems’ security aspects in a simple and intuitive
way and a model-driven process that transforms graphical
specifications of access control policies in XACML. These
XACML policies are then translated in FACPL, a policy
language with a formal semantics, and the resulting policies
are evaluated by means of a Java-based software tool
New uncertainty relations for tomographic entropy: Application to squeezed states and solitons
Using the tomographic probability distribution (symplectic tomogram)
describing the quantum state (instead of the wave function or density matrix)
and properties of recently introduced tomographic entropy associated with the
probability distribution, the new uncertainty relation for the tomographic
entropy is obtained. Examples of the entropic uncertainty relation for squeezed
states and solitons of the Bose--Einstein condensate are considered.Comment: 18 pages, 2 figures, to be published in European Physical Journal
- …