Message passing algorithms for non-linear nodes and data compression

The use of parity-check gates in information theory has proved to be very efficient. In particular, error correcting codes based on parity checks over low-density graphs show excellent performances. Another basic issue of information theory, namely data compression, can be addressed in a similar way by a kind of dual approach. The theoretical performance of such a Parity Source Coder can attain the optimal limit predicted by the general rate-distortion theory. However, in order to turn this approach into an efficient compression code (with fast encoding/decoding algorithms) one must depart from parity checks and use some general random gates. By taking advantage of analytical approaches from the statistical physics of disordered systems and SP-like message passing algorithms, we construct a compressor based on low-density non-linear gates with a very good theoretical and practical performance.Comment: 13 pages, European Conference on Complex Systems, Paris (Nov 2005

Quantum discord in finite XY chains

We examine the quantum discord between two spins in the exact ground state of finite spin 1/2 arrays with anisotropic XY couplings in a transverse field B. It is shown that in the vicinity of the factorizing field B_s, the discord approaches a common finite non-negligible limit which is independent of the pair separation and the coupling range. An analytic expression of this limit is provided. The discord of a mixture of aligned pairs in two different directions, crucial for the previous results, is analyzed in detail, including the evaluation of coherence effects, relevant in small samples and responsible for a parity splitting at B_s. Exact results for finite chains with first neighbor and full range couplings and their interpretation in terms of such mixtures are provided.Comment: 9 pages, 6 figure

Prediction of response to escitalopram across multiple outcomes in older adult GAD patients

Anxiety disorders are common in late-life and have detrimental effects of health and well-being (Stanley, Diefenbach, & Hopko, 2003; Wetherell et al., 2004). Generalized Anxiety Disorder (GAD) is the most common anxiety disorder in late-life (Beekman et al., 1998). Beyond the diagnostic symptoms, older adults with anxiety disorders may present with a variety of physical symptoms (Palmer, Jeste, & Sheikh, 1997). As a result, GAD is a heterogeneous disorder. Empirically-supported treatments are available for late-life GAD, but little is known about how people with different constellations of presenting symptoms respond to treatment, and whether they differ according to the way in which improvement is measured. The present study aimed to identify which presenting symptoms differentiated older adults with GAD from those without and how those symptoms predicted outcome across several domains of response. Participants were enrolled in a trial testing the efficacy of escitalopram for treatment of late-life GAD. One hundred and seventy-seven older adults with GAD and 41 older adults with no diagnosis participated. One hundred percent of the cases were correctly classified on the basis of the Anxious Mood and Tension SIGH-A items. A subset of participants with GAD who had been randomly assigned to received escitalopram and had completed 12 weeks of blinded treatment were further analyzed. Neither Anxious Mood nor Tension significantly predicted outcome in any domain. However, baseline scores on several of the outcome measures accounted for a significant amount of variance in week 12 scores, with lower scores being associated with better outcomes. These results indicate that baseline scores are the best predictors of outcome, and could have implications for treatment of GAD in late-life

Emotion Regulation and Threat Estimation as Mediators of the Relation between Cognitive Functioning and Anxiety in Late Life

Background: Rates of anxiety are generally thought to decline in typically aging older adults. Some theorize that this decline is a result of age-related improvements in emotion regulation. Emotion regulation may require the use of complex cognitive processes, however, which can be impacted by cognitive decline. Indeed, the prevalence of anxiety is high among older adults with cognitive impairment. The current study examined emotion regulation and threat perception as possible mediators in the relation between cognitive functioning and anxiety.;Methods: One hundred adults, aged 60 and older, were recruited from nursing homes, assisted living facilities, and the community. All were asked to complete a cognitive screening measure, along with measures of anxiety, emotion regulation, and threat perception. The relation between these variables was examined.;Results: Though cognitive impairment predicted anxiety level, neither emotion regulation nor threat perception mediated the relation.;Conclusions: The data suggest that emotion regulation and threat perception may rely on automatic processing, rather than effortful cognitive processing

Quantum correlations and least disturbing local measurements

We examine the evaluation of the minimum information loss due to an unread local measurement in mixed states of bipartite systems, for a general entropic form. Such quantity provides a measure of quantum correlations, reducing for pure states to the generalized entanglement entropy, while in the case of mixed states it vanishes just for classically correlated states with respect to the measured system, as the quantum discord. General stationary conditions are provided, together with their explicit form for general two-qubit states. Closed expressions for the minimum information loss as measured by quadratic and cubic entropies are also derived for general states of two-qubit systems. As application, we analyze the case of states with maximally mixed marginals, where a general evaluation is provided, as well as X states and the mixture of two aligned states.Comment: 10 pages, 3 figure

Risk Minimization through Portfolio Replication

We use a replica approach to deal with portfolio optimization problems. A given risk measure is minimized using empirical estimates of asset values correlations. We study the phase transition which happens when the time series is too short with respect to the size of the portfolio. We also study the noise sensitivity of portfolio allocation when this transition is approached. We consider explicitely the cases where the absolute deviation and the conditional value-at-risk are chosen as a risk measure. We show how the replica method can study a wide range of risk measures, and deal with various types of time series correlations, including realistic ones with volatility clustering.Comment: 12 pages, APFA5 conferenc

Overcoming doubt in vaccinations. The end justifies the means?

Controversies and scepticism about vaccination have existed as vaccination itself. Today and yester-day, the authority of religious leaders has a fundamental role for convince members of their congregations to accept or reject vaccination. Our contribution tells of the stratagem used by the Italian doctor Luigi Sacco to make the faithful lean towards the vaccination using their faith as a means. The history of yesterday’s end of today opens a current debate on the role and responsibility of religion around vaccination practice. As COVID-19 vaccine mandates grow, so are requests for religious exemptions. (www.actabiomedica.it)

Generalized entropic measures of quantum correlations

We propose a general measure of non-classical correlations for bipartite systems based on generalized entropic functions and majorization properties. Defined as the minimum information loss due to a local measurement, in the case of pure states it reduces to the generalized entanglement entropy, i.e., the generalized entropy of the reduced state. However, in the case of mixed states it can be non-zero in separable states, vanishing just for states diagonal in a general product basis, like the Quantum Discord. Simple quadratic measures of quantum correlations arise as a particular case of the present formalism. The minimum information loss due to a joint local measurement is also discussed. The evaluation of these measures in a few simple relevant cases is as well provided, together with comparison with the corresponding entanglement monotones.Comment: 9 pages, 2 figure