1,721,480 research outputs found
Numerical modelling of centrifuge dynamic tests on embedded cantilevered retaining walls
Full text linkThis paper presents the results from the numerical simulation of two dynamic centrifuge tests carried out on embedded cantilevered walls in dry sand, reconstituted at two different values of relative density. Plane strain analyses were performed using an advanced constitutive model for the soil, in which the set of model parameters was calibrated on the basis of standard laboratory tests.
The results show that advanced numerical modelling provides a good description of the seismic response of embedded retaining walls: very good agreement between numerical predictions and centrifuge data is obtained in terms of accelerations, while some discrepancies are observed in terms of displacements and bending moments in the walls, mainly due to experimental factors not
taken into account in the numerical analyses. The dynamic behaviour of embedded cantilevered retaining walls is strongly related to the redistribution of the stress state around the excavation induced by the inertia forces into the soil. More specifically, permanent rotations of the wall induce a progressive mobilization of the soil passive resistance and a consistent increase of the internal forces into the wall. Furthermore, significant displacements can be attained during an earthquake even for maximum accelerations smaller than the limit equilibrium critical value
Asymptotic morphisms and superselection theory in the scaling limit II: analysis of some models
Full text linkWe introduced in a previous paper a general notion of asymptotic morphism of a given local net of observables, which allows to describe the sectors of a corresponding scaling limit net. Here, as an application, we illustrate the general framework by analyzing the Schwinger model, which features confined charges. In particular, we explicitly construct asymptotic morphisms for these sectors in restriction to the subnet generated by the derivatives of the field and momentum at time zero. As a consequence, the confined charges of the Schwinger model are in principle accessible to observation. We also study the obstructions, that can be traced back to the infrared singular nature of the massless free field in d= 2 , to perform the same construction for the complete Schwinger model net. Finally, we exhibit asymptotic morphisms for the net generated by the massive free charged scalar field in four dimensions, where no infrared problems appear in the scaling limit
Permutations, tensor products, and Cuntz algebra automorphisms
Full text linkWe study the reduced Weyl groups of the Cuntz algebras On from a combinatorial point of view. Their elements correspond bijectively to certain permutations of nr elements, which we call stable. We mostly focus on the case r=2 and general n. A notion of rank is introduced, which is subadditive in a suitable sense. Being of rank 1 corresponds to solving an equation which is reminiscent of the Yang-Baxter equation. Symmetries of stable permutations are also investigated, along with an immersion procedure that allows to obtain stable permutations of (n+1)2 objects starting from stable permutations of n2 objects. A complete description of stable transpositions and of stable 3-cycles of rank 1 is obtained, leading to closed formulas for their number. Other enumerative results are also presented which yield lower and upper bounds for the number of stable permutations
Quasi-free isomorphisms of second quantization algebras and modular theory
Full text linkUsing Araki–Yamagami’s characterization of quasi-equivalence for quasi-free representations of the CCRs, we provide an abstract criterion for the existence of isomorphisms of second quantization local von Neumann algebras induced by Bogolubov transformations in terms of the respective one particle modular operators. We discuss possible applications to the problem of local normality of vacua of Klein-Gordon fields with different masses
Simplified formulas for the seismic bearing capacity of shallow strip foundations
No full textThe seismic bearing capacity of shallow foundations is affected by inertia forces acting both on the structure and in the supporting soil. Even though the former have been recognised to play often the major role, by increasing the horizontal load and the overturning moment transferred to the foundation, both of them must be taken into account in the seismic design of foundations. Using a pseudostatic approach and based on the upper bound theorem of limit analysis, a comprehensive set of formulas is derived for the computation of the seismic bearing capacity of strip footings resting on cohesive-frictional and purely cohesive soils. Results are given in terms of: (i) reduction coefficients for the Terzaghi's equation of the vertical bearing capacity and (ii) ultimate failure envelopes in the space of normalised loading variables. These formulas extend to more general conditions other literature results, allowing to take into account easily the effects of inertia forces acting both on the superstructure (load inclination and eccentricity) and into the foundation soil. The reliability of the proposed equations, suitable for the design practice, is verified through a thorough comparison with other rigorous and approximate solutions
Corrigendum to “Fourier theory and C∗-algebras” [J. Geom. Phys. 105 (2016) 2–24]?>(Fourier theory and C^∗-algebras (2016) 105 (2–24), (S0393044016300560), (10.1016/j.geomphys.2016.03.013))
No full textIn Proposition 2.9 of our paper cited above, we asserted that the space of bounded twisted multipliers on a discrete group is independent of the twist. It appears that this statement is not true in general. Only a weaker statement can be deduced from our arguments, as we explain in this short note. The rest of our article is unaffected by this error, except for one assertion in Corollary 2.12, which we also correct
On isometries of spectral triples associated to AF-algebras and crossed products
No full textWe examine the structure of two possible candidates of isometry groups for the spectral triples on AF-algebras introduced by Christensen and Ivan. In particular, we completely determine the isometry group introduced by Park and observe that these groups coincide in the case of the Cantor set. We also show that the construction of spectral triples on crossed products given by Hawkins, Skalski, White, and Zacharias is suitable for the purpose of lifting isometries
Calcolo delle correnti indotte nel corpo umano da campi elettrici e magnetici a frequenza industriale
No full textHeat properties for groups
No full textWe revisit Fourier’s approach to solve the heat equation on the circle in the context of (twisted) reduced group C*-algebras, convergence of Fourier series and semigroups associated to negative definite functions. We introduce some heat properties for countably infinite groups and investigate when they are satisfied. Kazhdan’s property (T) is an obstruction to the weakest property, and our findings leave open the possibility that this might be the only one. On the other hand, many groups with the Haagerup property satisfy the strongest version. We show that this heat property implies that the associated heat problem has a unique solution regardless of the choice of the initial datum
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