740 research outputs found
Massless scalar free Field in 1+1 dimensions I: Weyl algebras Products and Superselection Sectors
This is the first of two papers on the superselection sectors of the
conformal model in the title, in a time zero formulation. A classification of
the sectors of the net of observables as restrictions of solitonic (twisted)
and non-solitonic (untwisted) sector automorphisms of proper extensions of the
observable net is given. All of them are implemented by the elements of a field
net in a non-regular vacuum representation and the existence of a global
compact Abelian gauge group is proved. A non-trivial center in the fixed-point
net of this gauge group appears, but in an unphysical representation and
reducing to the identity in the physical one. The completeness of the described
superselection structure, to which the second paper is devoted, is shown in
terms of Roberts' net cohomology. Some general features of physical field
models defined by twisted cross products of Weyl algebras in non-regular
representations are also presented.Comment: published final versio
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Analisys of transformation of norms and sources (i.e. Constituttions) during periods of crisis and emergenc
The new challenge of constitutional Courts. global markets, terrorism, and immigration. the itaian case
the new challenge of constitutional courts is take into considerations both rights and powers , national protctions and immigrations flows. the deep problem is to extend the national guarantee to the non citoyens people
Causal posets, loops and the construction of nets of local algebras for QFT
We provide a model independent construction of a net of C*-algebras
satisfying the Haag-Kastler axioms over any spacetime manifold. Such a net,
called the net of causal loops, is constructed by selecting a suitable base K
encoding causal and symmetry properties of the spacetime. Considering K as a
partially ordered set (poset) with respect to the inclusion order relation, we
define groups of closed paths (loops) formed by the elements of K. These groups
come equipped with a causal disjointness relation and an action of the symmetry
group of the spacetime. In this way the local algebras of the net are the group
C*-algebras of the groups of loops, quotiented by the causal disjointness
relation. We also provide a geometric interpretation of a class of
representations of this net in terms of causal and covariant connections of the
poset K. In the case of the Minkowski spacetime, we prove the existence of
Poincar\'e covariant representations satisfying the spectrum condition. This is
obtained by virtue of a remarkable feature of our construction: any Hermitian
scalar quantum field defines causal and covariant connections of K. Similar
results hold for the chiral spacetime with conformal symmetry
Il Senato della riforma tra forma e sostanza
Il bicameralismo permette un dialogo continuo tra le due Camere e permette al PArlamento di usufruire di unamigliora attività di controllo e di qualità della legisalzione, ma soprattutto di integrare la rappresentanza. Quest'ultima funzione è assai rilevante nelle società pluraliste ma fortemente frammentate. L'inserimento nella seconda camera di una rapresentanza differenziata può consolidare quella benefica tensione tra unità e complessità che sono alla base del modello di democrazia pluralista.The most important function of bicameralism is a different representation in two chambers. this is importan for a democratic pluralism. The italian reforme does not have as goal this type of pluralism and the role of second chamber is weak
The universal C*-algebra of the electromagnetic field
A universal C*-algebra of the electromagnetic field is constructed. It is
represented in any quantum field theory which incorporates electromagnetism and
expresses basic features of this field such as Maxwell's equations, Poincar\'e
covariance and Einstein causality. Moreover, topological properties of the
field resulting from Maxwell's equations are encoded in the algebra, leading to
commutation relations with values in its center. The representation theory of
the algebra is discussed with focus on vacuum representations, fixing the
dynamics of the field.Comment: 17 pages, 1 figure; v2: minor corrections, version as to appear in
Lett. Math. Phys. Dedicated to the memory of D. Kastler and J.E. Roberts; v3
improvement of layou
La riforma del titolo v e il contenzioso di fronte alla corte costituzionale
SOMMARIO: 1. Premessa; 2. La genesi del nuovo Titolo V; 3. Le nuove forme di differenziazione (estese alle Regioni a statuto speciale); 4. Il riassetto delle competenze legislative e il tentativo di riduzione del contenzioso attraverso l’accentramento delle competenze in capo allo Stato; 5. L’elenco di materie, la potestà legislativa esclusiva dello Stato e il possibile aumento del contenzioso; 6. La dissoluzione della potestà legislativa concorrente? Tra mistificazione e realtà ; 7. Le disposizioni generali e comuni come nuova potestà concorrente?; 8. La clausola di supremazia e la sua eventuale giustiziabilità ; 9. Lo strano mantenimento delle funzioni amministrative: il 118 Cost. resta inalterato laddove tutto intorno cambia...; 10. L’art 119 Cost.: come le modifiche già apportate con L. cost 1/2012 pesino sulla riforma attuale; 11. Considerazioni conclusive
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