9,676 research outputs found
TAPAs: A Tool for the Analysis of Process Algebras
Process algebras are formalisms for modelling concurrent systems that permit mathematical reasoning with respect to a set of desired properties. TAPAs is a tool that can be used to support the use of process algebras to specify and analyze concurrent systems. It does not aim at guaranteeing high performances, but has been developed as a support to teaching. Systems are described as process algebras terms that are then mapped to labelled transition systems (LTSs). Properties are verified either by checking equivalence of concrete and abstract systems descriptions, or by model checking temporal formulae over the obtained LTS. A key feature of TAPAs, that makes it particularly suitable for teaching, is that it maintains a consistent double representation of each system both as a term and as a graph. Another useful didactical feature is the exhibition of counterexamples in case equivalences are not verified or the proposed formulae are not satisfied
-algebras and quantum dynamics: some existence results
We discuss the possibility of defining an algebraic dynamics within the
settings of -algebras. Compared with our previous results on this
subject, the main improvement here is that we are not assuming the existence of
some hamiltonian for the {\em full} physical system. We will show that, under
suitable conditions, the dynamics can still be defined via some limiting
procedure starting from a given {\em regularized sequence}
Unitary equivalence between ordinary intelligent states and generalized intelligent states
Ordinary intelligent states (OIS) hold equality in the Heisenberg uncertainty
relation involving two noncommuting observables {A, B}, whereas generalized
intelligent states (GIS) do so in the more generalized uncertainty relation,
the Schrodinger-Robertson inequality. In general, OISs form a subset of GISs.
However, if there exists a unitary evolution U that transforms the operators
{A, B} to a new pair of operators in a rotation form, it is shown that an
arbitrary GIS can be generated by applying the rotation operator U to a certain
OIS. In this sense, the set of OISs is unitarily equivalent to the set of GISs.
It is the case, for example, with the su(2) and the su(1,1) algebra that have
been extensively studied particularly in quantum optics. When these algebras
are represented by two bosonic operators (nondegenerate case), or by a single
bosonic operator (degenerate case), the rotation, or pseudo-rotation, operator
U corresponds to phase shift, beam splitting, or parametric amplification,
depending on two observables {A, B}.Comment: published version, 4 page
Characterizing quantum theory in terms of information-theoretic constraints
We show that three fundamental information-theoretic constraints--the
impossibility of superluminal information transfer between two physical systems
by performing measurements on one of them, the impossibility of broadcasting
the information contained in an unknown physical state, and the impossibility
of unconditionally secure bit commitment--suffice to entail that the
observables and state space of a physical theory are quantum-mechanical. We
demonstrate the converse derivation in part, and consider the implications of
alternative answers to a remaining open question about nonlocality and bit
commitment.Comment: 25 pages, LaTe
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