Entanglement entropy for non-coplanar regions in quantum field theory

We study the entanglement entropy in a relativistic quantum field theory for regions which are not included in a single spatial hyperplane. This geometric configuration cannot be treated with the Euclidean time method and the replica trick. Instead, we use a real time method to calculate the entropy for a massive free Dirac field in two dimensions in some approximations. We find some specifically relativistic features of the entropy. First, there is a large enhancement of entanglement due to boosts. As a result, the mutual information between relatively boosted regions does not vanish in the limit of zero volume and large relative boost. We also find extensivity of the information in a deeply Lorentzian regime with large violations of the triangle inequalities for the distances. This last effect is relevant to an interpretation of the amount of entropy enclosed in the Hawking radiation emitted by a black hole.Comment: 20 pages, 7 figure

Localization of Negative Energy and the Bekenstein Bound

A simple argument shows that negative energy cannot be isolated far away from positive energy in a conformal field theory and strongly constrains its possible dispersal. This is also required by consistency with the Bekenstein bound written in terms of the positivity of relative entropy. We prove a new form of the Bekenstein bound based on the monotonicity of the relative entropy, involving a "free" entropy enclosed in a region which is highly insensitive to space-time entanglement, and show that it further improves the negative energy localization bound.Comment: 5 pages, 1 figur

ECONOMIC EVALUATION OF NEWBORN HEARING SCREENING PROCEDURES

In the past few years, there has been a growing interest in the medical literature about the study of the different existing screening procedures to detect hearing impairment in infants and young children. However, concerning their economic evaluation, there are some important aspects, such as indirect costs, which are not considered by that literature. Here, we present an economic evaluation of these screening procedures, using utility theory, to measure benefits of a health care program, i.e. a cost-utility analysis. The analysis is presented from different points of view, depending on the cost we would like to compute. If we only consider direct costs, then targeted procedures, based on high risk criteria are preferred. On the other hand, if indirect costs, such as special education, and disability allowances were computed, then cost-utility analysis would advocate for the implementation of universal screening procedures.Economic Evaluation; Cost Utility Analysis; Cost-Sensitivity Ratios;

Multiplicative versus additive noise in multi-state neural networks

The effects of a variable amount of random dilution of the synaptic couplings in Q-Ising multi-state neural networks with Hebbian learning are examined. A fraction of the couplings is explicitly allowed to be anti-Hebbian. Random dilution represents the dying or pruning of synapses and, hence, a static disruption of the learning process which can be considered as a form of multiplicative noise in the learning rule. Both parallel and sequential updating of the neurons can be treated. Symmetric dilution in the statics of the network is studied using the mean-field theory approach of statistical mechanics. General dilution, including asymmetric pruning of the couplings, is examined using the generating functional (path integral) approach of disordered systems. It is shown that random dilution acts as additive gaussian noise in the Hebbian learning rule with a mean zero and a variance depending on the connectivity of the network and on the symmetry. Furthermore, a scaling factor appears that essentially measures the average amount of anti-Hebbian couplings.Comment: 15 pages, 5 figures, to appear in the proceedings of the Conference on Noise in Complex Systems and Stochastic Dynamics II (SPIE International