Screening and conductance relaxations in insulating granular aluminium thin films

We have recently found in insulating granular Al thin film a new experimental feature (Delahaye et al., Phys. Rev. Lett. 106, 186602, 2011), namely the existence of a conductance relaxation that is not sensitive to gate voltage changes. This conductance relaxation is related to the existence of a metallic-like screening in the film and can be used to estimate its characteristic length scale. In the present paper, we give some experimental details on how this feature was measured and present our first results on the screening length temperature dependence.Comment: 14th Transport in interacting disordered systems (TIDS14) conference, September 5-8 2011, Acre (Israel

The Limits of Discipline: Ownership and Hard Budget Constraints in the Transition Economies

This paper argues that the imposition of financial discipline is not sufficient to remedy ownership and governance-related deficiencies of corporate performance. Using evidence from the postcommunist transition economies, the paper shows that a policy of hard budget constraints falters when state firms, because of inferior revenue performance and lesser willingness to meet payment obligations, continue to pose higher credit risk than privatized firms. The brunt of state firms' lower creditworthiness falls on state creditors. But the "softness" of these creditors is unavoidable if it prevents a demise of firms that are in principle capable of successful restructuring through ownership changes.OWNERSHIP; FINANCIAL DISCIPLINE; PERFORMANCE; TRANSITION.

PARAMETRIC ESTIMATION OF HAZARD FUNCTIONS WITH STOCHASTIC COVARIATE PROCESSES

Let X(t), t âÂÂ¥ 0, be a real or vector valued stochastic process and T a random killing-time of the process which generally depends on the sample function. In the context of survival analysis, T represents the time to a prescribed event (e.g. system failure, time of disease symptom, etc.) and X(t) is a stochastic covariate process, observed up to time T. The conditional distribution of T, given X(t), t âÂÂ¥ 0, is assumed to be of a known functional form with an unknown vector parameter ø; however, the distributions of X(â¢) are not specified. For an arbitrary fixed ñ > 0 the observable data from a single realization of T and X(â¢) is min(T, ñ), X(t), 0 ⤠t ⤠min(T, ñ). For n âÂÂ¥ 1 the maximum likelihood estimator of ø is based on n independent copies of the observable data. It is shown that solutions of the likelihood equation are consistent and asymptotically normal and efficient under specified regularity conditions on the hazard function associated with the conditional distribution of T. The Fisher information matrix is represented in terms of the hazard function. The form of the hazard function is very general, and is not restricted to the commonly considered cases where it depends on X(â¢) only through the present point X(t). Furthermore, the process X(â¢) is a general, not necessarily Markovian process.Statistics Working Papers Serie

Ulta-slow relaxation in discontinuous-film based electron glasses

We present field effect measurements on discontinuous 2D thin films which are composed of a sub monolayer of nano-grains of Au, Ni, Ag or Al. Like other electron glasses these systems exhibit slow conductance relaxation and memory effects. However, unlike other systems, the discontinuous films exhibit a dramatic slowing down of the dynamics below a characteristic temperature $T^*$. $T^*$ is typically between 10-50K and is sample dependent. For $T<T^*$ the sample exhibits a few other peculiar features such as repeatable conductance fluctuations in millimeter size samples. We suggest that the enhanced system sluggishness is related to the current carrying network becoming very dilute in discontinuous films so that the system contains many parts which are electrically very weakly connected and the transport is dominated by very few weak links. This enables studying the glassy properties of the sample as it transitions from a macroscopic sample to a mesocopic sample, hence, the results provide new insight on the underlying physics of electron glasses.Comment: 4 pages, 4 figure

Perfect state transfers by selective quantum interferences within complex spin networks

We present a method that implement directional, perfect state transfers within a branched spin network by exploiting quantum interferences in the time-domain. That provides a tool to isolate subsystems from a large and complex one. Directionality is achieved by interrupting the spin-spin coupled evolution with periods of free Zeeman evolutions, whose timing is tuned to be commensurate with the relative phases accrued by specific spin pairs. This leads to a resonant transfer between the chosen qubits, and to a detuning of all remaining pathways in the network, using only global manipulations. As the transfer is perfect when the selected pathway is mediated by 2 or 3 spins, distant state transfers over complex networks can be achieved by successive recouplings among specific pairs/triads of spins. These effects are illustrated with a quantum simulator involving 13C NMR on Leucine's backbone; a six-spin network.Comment: 5 pages, 3 figure