The DMT classification of real and quaternionic lattice codes

In this paper we consider space-time codes where the code-words are restricted to either real or quaternion matrices. We prove two separate diversity-multiplexing gain trade-off (DMT) upper bounds for such codes and provide a criterion for a lattice code to achieve these upper bounds. We also point out that lattice codes based on Q-central division algebras satisfy this optimality criterion. As a corollary this result provides a DMT classification for all Q-central division algebra codes that are based on standard embeddings.Comment: 6 pages, 1 figure. Conference paper submitted to the International Symposium on Information Theory 201

The Method of Comparison Equations for Schwarzschild Black Holes

We employ the method of comparison equations to study the propagation of a massless minimally coupled scalar field on the Schwarzschild background. In particular, we show that this method allows us to obtain explicit approximate expressions for the radial modes with energy below the peak of the effective potential which are fairly accurate over the whole region outside the horizon. This case can be of particular interest, for example, for the problem of black hole evaporation.Comment: 7 pages, added figures. Version to appear in PR

Child and teenager oral health and dental visiting: results from the National Dental Telephone Interview Survey 2010

This publication reports on oral health, dental visiting and dental treatment needs of Australian children as reported in the National Dental Telephone Interview Survey (NDTIS) 2010. Time series data across all NDTISs conducted since 1994 are presented to provide a picture of how key measures have changed over time. Finally, comparisons with international data are presented to provide a picture of how Australian children fare among their international counterparts.Oral healthThe majority of Australian children report good oral health. However, 7% reported that they had experienced toothache and 10% reported that they had avoided certain foods during the previous 12 months. Children from low income households were more likely to report having fair or poor oral health and to have experienced toothache than children from high income households. There was no significant change over time in these measures.Dental visitingAlmost 70% of children made a dental visit in the previous 12 months and the majority (84%) visited for a check-up. Less than a third of pre-school-aged children had ever made a dental visit. Children from the lowest income households were less likely than those from higher income households to have both made a dental visit and to have visited for a check-up. Both of these measures of dental visiting have remained fairly stable over time.Barriers to dental care useAround 13% of children avoided or delayed making a dental visit due to cost. Around 6% did not have a recommended treatment due to cost. Overall, almost 30% of children avoided or delayed seeking care, did not have recommended treatment or their household experienced a large financial burden due to the cost of dental care. Children from low income households were 7 times as likely than those from high income households to avoid or delay due to cost and 6 times as likely to have not had recommended treatment due to cost.International comparisonsComparable data are available for children in Canada and New Zealand. Overall, Australian children were less likely to report that they had fair or poor oral health, and less likely to have made a dental visit in the previous 12 months than their counterparts in New Zealand. Australian teenagers were less likely than their Canadian counterparts to report fair or poor oral health and were more likely to have avoided or delayed making a dental visit due to cost

Almost universal codes for fading wiretap channels

We consider a fading wiretap channel model where the transmitter has only statistical channel state information, and the legitimate receiver and eavesdropper have perfect channel state information. We propose a sequence of non-random lattice codes which achieve strong secrecy and semantic security over ergodic fading channels. The construction is almost universal in the sense that it achieves the same constant gap to secrecy capacity over Gaussian and ergodic fading models.Comment: 5 pages, to be submitted to IEEE International Symposium on Information Theory (ISIT) 201

Do Liquidity Constraints Matter in Explaining Firm Size and Growth? Some Evidence from the Italian Manufacturing Industry

The paper investigates whether liquidity constraints affect firm size and growth dynamics using a large longitudinal sample of Italian manufacturing firms. We run standard panel-data Gibrat regressions, suitably expanded to take into account liquidity constraints (proxied by cash flow). Moreover, we characterize the statistical properties of firms size, growth, age, and cash flow distributions. Pooled data show that: (i) liquidity constraints engender a negative, statistically significant, effect on growth once one controls for size; (ii) smaller and younger firms grow more (and experience more volatile growth patterns) after controlling for liquidity constraints; (iii) the stronger liquidity constraints, the more size negatively affects firm growth. We find that pooled size distributions depart from log-normality and growth rates are well approximated by fat-tailed, tent-shaped (Laplace) densities. We also study the evolution of growth-size distributions over time. Our exercises suggest that the strong negative impact of liquidity constraints on firm growth which was present in the pooled sample becomes ambiguous when one disaggregates across years. Finally, firms who were young and strongly liquidity-constrained at the beginning of the sample period grew persistently more than those who were old and weakly liquidity-constrained.Firm Size, Liquidity Constraints, Firm Growth, Investment, Gibrat Law

Secret key generation from Gaussian sources using lattice hashing

We propose a simple yet complete lattice-based scheme for secret key generation from Gaussian sources in the presence of an eavesdropper, and show that it achieves strong secret key rates up to 1/2 nat from the optimal in the case of "degraded" source models. The novel ingredient of our scheme is a lattice-hashing technique, based on the notions of flatness factor and channel intrinsic randomness. The proposed scheme does not require dithering.Comment: 5 pages, Conference (ISIT 2013

Work after the Age of Fifty: Switzerland in an international Comparison

Ältere Arbeitskräfte, Arbeitsmarkt, Arbeitsmarktpolitik, Schweiz, Elderly workforce, Labour market, Labour market policy, Switzerland

Dynamics of a Bose-Einstein Condensate of Excited Magnons

The emergence of a non-equilibrium Bose-Einstein-like condensation of magnons in rf-pumped magnetic thin films has recently been experimentally observed. We present here a complete theoretical description of the non-equilibrium processes involved. It it demonstrated that the phenomenon is another example of the presence of a Bose-Einstein-like condensation in non-equilibrium many-boson systems embedded in a thermal bath, better referred-to as Fr\"{o}hlich-Bose-Einstein condensation. The complex behavior emerges after a threshold of the exciting intensity is attained. It is inhibited at higher intensities when the magnon-magnon interaction drives the magnons to internal thermalization. The observed behavior of the relaxation to equilibrium after the end of the pumping pulse is also accounted for and the different processes fully described.Comment: 42 pages, 11 figure