Paired states on a torus

We analyze the modular properties of the effective CFT description for paired states, proposed in cond-mat/0003453, corresponding to the non-standard filling nu =1/(p+1). We construct its characters for the twisted and the untwisted sector and the diagonal partition function. We show that the degrees of freedom entering our partition function naturally go to complete a Z_2-orbifold construction of the CFT for the Halperin state. Different behaviours for the p even and p odd cases are also studied. Finally it is shown that the tunneling phenomenon selects out a twist invariant CFT which is identified with the Moore-Read model.Comment: 24 pages, 1 figure, Late

A conformal field theory description of the paired and parafermionic states in the quantum Hall effect

We extend the construction of the effective conformal field theory for the Jain hierarchical fillings proposed in cond-mat/9912287 to the description of a quantum Hall fluid at non standard fillings nu=m/(pm+2). The chiral primary fields are found by using a procedure which induces twisted boundary conditions on the m scalar fields; they appear as composite operators of a charged and neutral component. The neutral modes describe parafermions and contribute to the ground state wave function with a generalized Pfaffian term. Correlators of Ne electrons in the presence of quasi-hole excitations are explicitly given for m=2.Comment: 11 pages, plain Late

A conformal field theory description of magnetic flux fractionalization in Josephson junction ladders

We show how the recently proposed effective theory for a Quantum Hall system at "paired states" filling v=1 (Mod. Phys. Lett. A 15 (2000) 1679; Nucl. Phys. B641 (2002) 547), the twisted model (TM), well adapts to describe the phenomenology of Josephson Junction ladders (JJL) in the presence of defects. In particular it is shown how naturally the phenomenon of flux fractionalization takes place in such a description and its relation with the discrete symmetries present in the TM. Furthermore we focus on closed geometries, which enable us to analyze the topological properties of the ground state of the system in relation to the presence of half flux quanta.Comment: 16 pages, 2 figure, Latex, revised versio

New Results on the Phase Diagram of the FFXY Model: A Twisted CFT Approach

The issue of the number, nature and sequence of phase transitions in the fully frustrated XY (FFXY) model is a highly non trivial one due to the complex interplay between its continuous and discrete degrees of freedom. In this contribution we attack such a problem by means of a twisted conformal field theory (CFT) approach and show how it gives rise to the U (1)$\otimes Z_{2}$ symmetry and to the whole spectrum of excitations of the FFXY model.Comment: 7 pages; talk given by G. Niccoli at "Path Integrals - New Trends and Perspectives International Conference", Max-Planck-Institut, Dresden, Germany, September 23 - 28, 200

Self-consistent variational approach to the minimal left-right symmetric model of electroweak interactions

The problem of mass generation is addressed by a Gaussian variational method for the minimal left-right symmetric model of electroweak interactions. Without any scalar bidoublet, the Gaussian effective potential is shown to have a minimum for a broken symmetry vacuum with a finite expectation value for both the scalar Higgs doublets. The symmetry is broken by the fermionic coupling that destabilizes the symmetric vacuum, yielding a self consistent fermionic mass. In this framework a light Higgs is only compatible with the existence of a new high energy mass scale below 2 TeV.Comment: 5 pages, 3 figures. New comments added and typing errors in eq. 8 and 11 correcte

Tecnologie dell’informazione e nuovi processi di vittimizzazione

Le nuove tecnologie, da un lato, hanno prodotto indubbi effetti positivi, dall’accelerazione della diffusione culturale alla comunicazione tra “mondi” prima sconosciuti, dall’altro sono diventate anche strumento di nuove modalità devianti e criminali. Nel lavoro si discutono i processi di vittimizzazione in rapporto ad alcuni reati (furto d’identità, pedopornografia on line, cyberstalking), nonché alle nuove forme di dipendenza, dovuti ai new media, allo scopo di metterne in evidenza i pericoli di un loro uso distorto o abuso per le potenziali vittime. S'il est vrai que les nouvelles technologies de communication ont produit des effets positifs indéniables, comme l'accélération de la diffusion culturelle et l'échange entre « mondes » jusque-là inconnus, elles n'en sont pas moins devenues un moyen de commettre des actes déviants et criminels nouveaux. Cet article expose les processus de victimisation liés à certains crimes (comme l'usurpation d'identité, la pédopornographie en ligne, le cyber-harcèlement), et de nouvelles formes de dépendance, afin de mettre en évidence les dangers d'un usage pervers ou délictueux des nouveaux médias. New technologies, on the one hand, have produced undeniable positive effects, from the acceleration of cultural diffusion to the communication between "worlds" previously unknown; on the other hand, they have become now an instrument to commit new crimes and deviants acts. In the article we will discuss the processes of victimization related to specific offenses (digital identity theft, online paedopornography, cyberstalking) and to new forms of addiction due to the new media. The aim is to highlight the dangers of the misuse or abuse of new technologies

Structural breaks in the lending interest rate pass-through and the euro

This paper investigates whether size and speed of the pass-through of market rates into short term business lending rates have increased in the wake of the introduction of the euro. Allowing for multiple unknown structural breaks we find two in four EMU countries, and in the UK as well, and a single one in five other countries. The pattern of dates fits national banking systems adjusting slowly to the new monetary regime and suggests caution in associating structural changes to the introduction of the euro. The estimated equilibrium pass-through in the last break-free period is on average more incomplete, hinting at a reduced effectiveness of the single monetary policy. This results runs against the economic intuition that a reduced volatility in money market rates is bound to mitigate uncertainty and to ease therefore the transfer of policy rate changes to retail rates; the run up to Basel 2 and a deterioration of competition in loan markets could be the motivations. Caution in extrapolating to more recent periods these findings is suggested by the differences between the unharmonized and the new harmonized retail rates

Are defined contribution pension schemes socially sustainable? A conceptual map from a macroprudential perspective

If the combined retirement income, provided by public and private defined contribution (DC) pension schemes, falls below socially acceptable standards, there is a political risk that consensus seeker policymakers could yield to pressures to commit future fiscal revenues. These contingent liabilities, when incorporated in markets\u2019 expectations, are bound to create spillovers on sovereign risk, with negative feedback loops on the capital adequacy of banks and of other intermediaries, owing to losses on their government paper. Among the causes of reduced annuities out of the final assets in DC pension funds is an equity risk premium much lower than the commonly values advertised by the industry and by policymakers. From a macroprudential perspective, this political risk should be taken into account in stress tests assessing banks\u2019 resilience to financial shocks