202 research outputs found
Contract-Driven Implementation of Choreographies
Choreographies and Contracts are important concepts in Service Oriented Computing. Choreographies are the description of the behaviour of a service system from a global point of view, while contracts are the description of the externally observable message-passing behaviour of a given service. Exploiting some of our previous results about choreography projection and contract refinement, we show how to solve the problem of implementing a choreography via the composition of already available services that are retrieved according to their contracts
Conformal Gauge Transformations in Thermodynamics
In this work we consider conformal gauge transformations of the geometric
structure of thermodynamic fluctuation theory. In particular, we show that the
Thermodynamic Phase Space is naturally endowed with a non-integrable
connection, defined by all those processes that annihilate the Gibbs 1-form,
i.e. reversible processes. Therefore the geometry of reversible processes is
invariant under re-scalings, that is, it has a conformal gauge freedom.
Interestingly, as a consequence of the non-integrability of the connection, its
curvature is not invariant under conformal gauge transformations and,
therefore, neither is the associated pseudo-Riemannian geometry. We argue that
this is not surprising, since these two objects are associated with
irreversible processes. Moreover, we provide the explicit form in which all the
elements of the geometric structure of the Thermodynamic Phase Space change
under a conformal gauge transformation. As an example, we revisit the change of
the thermodynamic representation and consider the resulting change between the
two metrics on the Thermodynamic Phase Space which induce Weinhold's energy
metric and Ruppeiner's entropy metric. As a by-product we obtain a proof of the
well-known conformal relation between Weinhold's and Ruppeiner's metrics along
the equilibrium directions. Finally, we find interesting properties of the
almost para-contact structure and of its eigenvectors which may be of physical
interest
Adaptable processes
We propose the concept of adaptable processes as a way of overcoming the
limitations that process calculi have for describing patterns of dynamic
process evolution. Such patterns rely on direct ways of controlling the
behavior and location of running processes, and so they are at the heart of the
adaptation capabilities present in many modern concurrent systems. Adaptable
processes have a location and are sensible to actions of dynamic update at
runtime; this allows to express a wide range of evolvability patterns for
concurrent processes. We introduce a core calculus of adaptable processes and
propose two verification problems for them: bounded and eventual adaptation.
While the former ensures that the number of consecutive erroneous states that
can be traversed during a computation is bound by some given number k, the
latter ensures that if the system enters into a state with errors then a state
without errors will be eventually reached. We study the (un)decidability of
these two problems in several variants of the calculus, which result from
considering dynamic and static topologies of adaptable processes as well as
different evolvability patterns. Rather than a specification language, our
calculus intends to be a basis for investigating the fundamental properties of
evolvable processes and for developing richer languages with evolvability
capabilities
Scaling symmetries and canonoid transformations in Hamiltonian systems
We investigate various types of symmetries and their mutual relationships in
Hamiltonian systems defined on manifolds with different geometric structures:
symplectic, cosymplectic, contact and cocontact. In each case we pay special
attention to non-standard (non-canonical) symmetries, in particular scaling
symmetries and canonoid transformations, as they provide new interesting tools
for the qualitative study of these systems. Our main results are the
characterizations of these non-standard symmetries and the analysis of their
relation with conserved (or dissipated) quantities.Comment: 22 pages. Comments are welcom
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