How to add a boundary condition

Given a conformal QFT local net of von Neumann algebras B_2 on the two-dimensional Minkowski spacetime with irreducible subnet A\otimes\A, where A is a completely rational net on the left/right light-ray, we show how to consistently add a boundary to B_2: we provide a procedure to construct a Boundary CFT net B of von Neumann algebras on the half-plane x>0, associated with A, and locally isomorphic to B_2. All such locally isomorphic Boundary CFT nets arise in this way. There are only finitely many locally isomorphic Boundary CFT nets and we get them all together. In essence, we show how to directly redefine the C* representation of the restriction of B_2 to the half-plane by means of subfactors and local conformal nets of von Neumann algebras on S^1.Comment: 20 page

On local boundary CFT and non-local CFT on the boundary

The holographic relation between local boundary conformal quantum field theories (BCFT) and their non-local boundary restrictions is reviewed, and non-vacuum BCFT's, whose existence was conjectured previously, are constructed.Comment: 16 pages. Contribution to "Rigorous Quantum Field Theory", Symposium in honour of J. Bros, Paris, July 2004. Based on joint work math-ph/0405067 with R. Long

Photometric redshifts for Quasars in multi band Surveys

MLPQNA stands for Multi Layer Perceptron with Quasi Newton Algorithm and it is a machine learning method which can be used to cope with regression and classification problems on complex and massive data sets. In this paper we give the formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (SDSS, GALEX, UKIDSS and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able i) to achieve a very high accuracy; ii) to drastically reduce the number of outliers and catastrophic objects; iii) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of DeltaZnorm (i.e. (zspec-zphot)/(1+zspec)), to an average of DeltaZnorm = 0.004, a standard deviation sigma = 0.069 and a Median Absolute Deviation MAD = 0.02 over the whole redshift range (i.e. zspec <= 3.6), defined by the 4-survey cross-matched spectroscopic sample. The fraction of catastrophic outliers, i.e. of objects with photo-z deviating more than 2sigma from the spectroscopic value is < 3%, leading to a sigma = 0.035 after their removal, over the same redshift range. The method is made available to the community through the DAMEWARE web application.Comment: 38 pages, Submitted to ApJ in February 2013; Accepted by ApJ in May 201

Metallicity of the polar disk in NGC4650A: constraints for cold accretion scenario

We used high resolution spectra in the optical and near-infrared wavelength range to study the abundance ratios and metallicities of the HII regions associated with the polar disk in NGC4650A, in order to put constraints on the formation of the polar disk through cold gas accretion along a filament; this might be the most realistic way by which galaxies get their gas. We have compared the measured metallicities for the polar structure in NGC4650A with those of different morphological types and we have found that they are similar to those of late-type galaxies: such results is consistent with a polar disk formed by accretion from cosmic web filaments of external cold gas.Comment: Proceeding of the conference "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 200

Specificity and coherence of body representations

Bodily illusions differently affect body representations underlying perception and action. We investigated whether this task dependence reflects two distinct dimensions of embodiment: the sense of agency and the sense of the body as a coherent whole. In experiment 1 the sense of agency was manipulated by comparing active versus passive movements during the induction phase in a video rubber hand illusion (vRHI) setup. After induction, proprioceptive biases were measured both by perceptual judgments of hand position, as well as by measuring end-point accuracy of subjects' active pointing movements to an external object with the affected hand. The results showed, first, that the vRHI is largely perceptual: passive perceptual localisation judgments were altered, but end-point accuracy of active pointing responses with the affected hand to an external object was unaffected. Second, within the perceptual judgments, there was a novel congruence effect, such that perceptual biases were larger following passive induction of vRHI than following active induction. There was a trend for the converse effect for pointing responses, with larger pointing bias following active induction. In experiment 2, we used the traditional RHI to investigate the coherence of body representation by synchronous stimulation of either matching or mismatching fingers on the rubber hand and the participant's own hand. Stimulation of matching fingers induced a local proprioceptive bias for only the stimulated finger, but did not affect the perceived shape of the hand as a whole. In contrast, stimulation of spatially mismatching fingers eliminated the RHI entirely. The present results show that (i) the sense of agency during illusion induction has specific effects, depending on whether we represent our body for perception or to guide action, and (ii) representations of specific body parts can be altered without affecting perception of the spatial configuration of the body as a whole

Body image distortions following spinal cord injury

Background: Following spinal cord injury (SCI) or anaesthesia, people may continue to experience feelings of the size, shape, and posture of their body, suggesting that the conscious body image is not fully determined by immediate sensory signals. How this body image is affected by changes in sensory inputs from, and motor outputs to the body remains unclear. Methods: We tested paraplegic and tetraplegic SCI patients on a task that yields quantitative measures of body image. Participants were presented with an anchoring stimulus on a computer screen and told to imagine that the displayed body part was part of a standing mirror image of themselves. They then identified the position on the screen, relative to the anchor, where each of several parts of their body would be located. Veridical body dimensions were identified based on measurements and photographs of participants. Results: Compared to age-matched controls, paraplegic and tetraplegic patients alike perceived their torso and limbs as elongated relative to their body width. No effects of lesion level were found. Conclusions: The common distortions in body image across patient groups, despite differing SCI levels, imply that a body image may be maintained despite chronic sensory and motor loss. Systematic alterations in body image follow SCI, though our results suggest these may reflect prolonged changes in body posture and wheelchair use, rather than loss of specific sensorimotor pathways. These findings provide new insight into how the body image is maintained, and may prove useful in treatments that intervene to manipulate the body image

The Conformal Spin and Statistics Theorem

We prove the equality between the statistics phase and the conformal univalence for a superselection sector with finite index in Conformal Quantum Field Theory on $S^1$. A relevant point is the description of the PCT symmetry and the construction of the global conjugate charge.Comment: plain tex, 22 page

Steps toward a classifier for the Virtual Observatory. I. Classifying the SDSS photometric archive

Modern photometric multiband digital surveys produce large amounts of data that, in order to be effectively exploited, need automatic tools capable to extract from photometric data an objective classification. We present here a new method for classifying objects in large multi-parametric photometric data bases, consisting of a combination of a clustering algorithm and a cluster agglomeration tool. The generalization capabilities and the potentialities of this approach are tested against the complexity of the Sloan Digital Sky Survey archive, for which an example of application is reported.Comment: To appear in the Proceedings of the "1st Workshop of Astronomy and Astrophysics for Students" - Naples, 19-20 April 200