446 research outputs found
Correlation Functions in -Deformed N=6 Supergravity
Gauged N=8 supergravity in four dimensions is now known to admit a
deformation characterized by a real parameter lying in the interval
. We analyse the fluctuations about its anti-de Sitter
vacuum, and show that the full N=8 supersymmetry can be maintained by the
boundary conditions only for . For non-vanishing , and
requiring that there be no propagating spin s>1 fields on the boundary, we show
that N=3 is the maximum degree of supersymmetry that can be preserved by the
boundary conditions. We then construct in detail the consistent truncation of
the N=8 theory to give -deformed SO(6) gauged N=6 supergravity, again
with in the range . We show that this theory
admits fully N=6 supersymmetry-preserving boundary conditions not only for
, but also for . These two theories are related by a
U(1) electric-magnetic duality. We observe that the only three-point functions
that depend on involve the coupling of an SO(6) gauge field with the
U(1) gauge field and a scalar or pseudo-scalar field. We compute these
correlation functions and compare them with those of the undeformed N=6 theory.
We find that the correlation functions in the theory
holographically correspond to amplitudes in the U(N)_k x U(N)_{-k} ABJM model
in which the U(1) Noether current is replaced by a dynamical U(1) gauge field.
We also show that the -deformed N=6 gauged supergravities can be
obtained via consistent reductions from the eleven-dimensional or
ten-dimensional type IIA supergravities.Comment: 38 pages, one figur
3D ANALYSIS OF THE BODY CENTRE OF MASS IN ROCK CLIMBING
The purposes of this study were: to test an experimental protocol for the analysis of basic rock climbing movements; to find whether it is possible to identify a golden standard strategy for the proposed movements. 12 recreational climbers were involved in the study. Each subject climbed a 3m horizontal shift followed by a 3m ascent. Climbers could choose their own style, their preferred speed and holds. Acquisition were performed using an optoelectronic system with reflective passive markers, attached to the subjects' joints. Results show that two main climbing strategies can be identified: the first preferring agility over force and the second preferring force over agility; we also found out that, good climbers try to minimize power, during the whole trial. These results would be our starting point for new experimental sessions
Phase-dependent absorption features in X-ray spectra of X-ray Dim Isolated Neutron Stars
A detailed phase-resolved spectroscopy of archival XMM-Newton observations of X-ray Dim Isolated Neutron Stars (XDINSs) led to the discovery of narrow and strongly phase-dependent absorption features in two of these sources. The first was discovered in the X-ray spectrum of RX J0720.4-3125, followed by a new possible candidate in RX J1308.6+2127. Both spectral lines have similar properties: they are detected for only ∼ 20% of the rotational cycle and appear to be stable over the timespan covered by the observations. We performed Monte Carlo simulations to test the significance of these phase-variable features and in both cases the outcome has confirmed the detection with a confidence level > 4.6σ. Because of the narrow width and the strong dependence on the pulsar rotational phase, the most likely interpretation for these spectral features is in terms of resonant proton cyclotron absorption scattering in a confined high-B structure close to the stellar surface. Within the framework of this interpretation, our results provide evidence for deviations from a pure dipole magnetic field on small scales for highly magnetized neutron stars and support the proposed scenario of XDINSs being aged magnetars, with a strong non-dipolar crustal B-field component
Minimal Stability in Maximal Supergravity
Recently, it has been shown that maximal supergravity allows for
non-supersymmetric AdS critical points that are perturbatively stable. We
investigate this phenomenon of stability without supersymmetry from the
sGoldstino point of view. In particular, we calculate the projection of the
mass matrix onto the sGoldstino directions, and derive the necessary conditions
for stability. Indeed we find a narrow window allowing for stable SUSY breaking
points. As a by-product of our analysis, we find that it seems impossible to
perturb supersymmetric critical points into non-supersymmetric ones: there is a
minimal amount of SUSY breaking in maximal supergravity.Comment: 27 pages, 1 figure. v2: two typos corrected, published versio
Clustering the lexicon in the brain: a meta-analysis of the neurofunctional evidence on noun and verb processing
Although it is widely accepted that nouns and verbs are functionally independent linguistic entities, it is less clear whether their processing recruits different brain areas. This issue is particularly relevant for those theories of lexical semantics (and, more in general, of cognition) that suggest the embodiment of abstract concepts, i.e., based strongly on perceptual and motoric representations. This paper presents a formal meta analysis of the neuroimaging evidence on noun and verb processing in order to address this dichotomy more effectively at the anatomical level. We used a hierarchical clustering algorithm that grouped fMRI/PET activation peaks solely on the basis of spatial proximity. Cluster specificity for grammatical class was then tested on the basis of the noun verb distribution of the activation peaks included in each cluster. 32 clusters were identified: three were associated with nouns across different tasks (in the right inferior temporal gyrus, the left angular gyrus, and the left inferior parietal gyrus); one with verbs across different tasks (in the posterior part of the right middle temporal gyrus); and three showed verb specificity in some tasks and noun specificity in others (in the left and right inferior frontal gyrus and the left insula). These results do not support the popular tenets that verb processing is predominantly based in the left frontal cortex and noun processing relies specifically on temporal regions; nor do they support the idea that verb lexical semantic representations are heavily based on embodied motoric information. Our findings suggest instead that the cerebral circuits deputed to noun and verb processing lie in close spatial proximity in a wide network including frontal, parietal, and temporal regions. The data also indicate a predominant \u2013 but not exclusive \u2013 left lateralization of the network
Renewed activity from the magnetar CXOU J164710.2-455216
On 2018 February 5 at 19:27:11 UT, Swift BAT detected a new burst from a direction consistent with the magnetar CXOU J164710.2-455216 (trigger=808755; Barthelmy et al. 2018, GCN #22389)
Using Virtual Reality to Rehabilitate Neglect
Purpose: Virtual Reality (VR) platforms gained a lot of attention in the rehabilitation field due to their ability to engage patients and the opportunity they offer to use real world scenarios. As neglect is characterized by an impairment in exploring space that greatly affects daily living, VR could be a powerful tool compared to classical paper and pencil tasks and computer training. Nevertheless, available platforms are costly and obstructive. Here we describe a low cost platform for neglect rehabilitation, that using consumer equipments allows the patient to train at home in an intensive fashion.
Method: We tested the platform on IB, a chronic neglect patient, who did not benefit from classical rehabilitation.
Results: Our results show that IB improved both in terms of neglect and attention. Importantly, these ameliorations lasted at a follow up evaluation 5 months after the last treatment session and generalized to everyday life activities.
Conclusions: VR platforms built using equipment technology and following theoretical principles on brain functioning may induce greater ameliorations in visuo-spatial deficits than classical paradigms possibly thanks to the real world scenarios in association with the "visual feedback" of the patient's own body operating in the virtual environmen
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