From ten to four and back again: how to generalize the geometry

We discuss the four-dimensional N=1 effective approach in the study of warped type II flux compactifications with SU(3)x SU(3)-structure to AdS_4 or flat Minkowski space-time. The non-trivial warping makes it natural to use a supergravity formulation invariant under local complexified Weyl transformations. We obtain the classical superpotential from a standard argument involving domain walls and generalized calibrations and show how the resulting F-flatness and D-flatness equations exactly reproduce the full ten-dimensional supersymmetry equations. Furthermore, we consider the effect of non-perturbative corrections to this superpotential arising from gaugino condensation or Euclidean D-brane instantons. For the latter we derive the supersymmetry conditions in N=1 flux vacua in full generality. We find that the non-perturbative corrections induce a quantum deformation of the internal generalized geometry. Smeared instantons allow to understand KKLT-like AdS vacua from a ten-dimensional point of view. On the other hand, non-smeared instantons in IIB warped Calabi-Yau compactifications 'destabilize' the Calabi-Yau complex structure into a genuine generalized complex one. This deformation gives a geometrical explanation of the non-trivial superpotential for mobile D3-branes induced by the non-perturbative corrections.Comment: LaTeX, 47 pages, v2, references, hyperref added, v3, correcting small inaccuracies in eqs. (2.6a) and (5.16

The energy and stability of D-term strings

Cosmic strings derived from string theory, supergravity or any theory of choice should be stable if we hope to observe them. In this paper we consider D-term strings in D=4, N=1 supergravity with a constant Fayet-Iliopoulos term. We show that the positive deficit angle supersymmetric D-term string is non-perturbatively stable by using standard Witten-Nester techniques to prove a positive energy theorem. Particular attention is paid to the negative deficit angle D-term string, which is known to violate the dominant energy condition. Within the class of string solutions we consider, this violation implies that the negative deficit angle D-term string must have a naked pathology and therefore the positive energy theorem we prove does not apply to it. As an interesting aside, we show that the Witten-Nester charge calculates the total gravitational energy of the D-term string without the need for a cut-off, which may not have been expected.Comment: 18 pages. v2: minor changes and references adde

Dirac equation for the supermembrane in a background with fluxes from a component description of the D=11 supergravity-supermembrane interacting system

We present a simple derivation of the 'Dirac' equation for the supermembrane fermionic field in a D=11 supergravity background with fluxes by using a complete but gauge-fixed description of the supergravity-supermembrane interacting system previously developed. We also discuss the contributions linear in the supermembrane fermions -the Goldstone fields for the local supersymmetry spontaneously broken by the superbrane- to the field equations of the supergravity-supermembrane interacting system. The approach could also be applied to more complicated dynamical systems such as those involving the M5-brane and the D=10 Dirichlet branes.Comment: 1+22 pages, JHEP style. v2: cosmetic changes and references added to conform to the JHEP published versio

Flavor brane on the baryonic branch of moduli space

We study an extra flavor in the cascading SU((k+1)M)xSU(k M) gauge theory by adding probe D7-brane to the geometry. By finding a solution to the kappa-symmetry equation we establish that the D7-brane is mutually supersymmetric with the background everywhere on the baryonic branch of moduli space. We also discuss possible applications of this result.Comment: 15 pages; v2 typo corrected, references adde

D-branes on AdS flux compactifications

We study D-branes in N=1 flux compactifications to AdS_4. We derive their supersymmetry conditions and express them in terms of background generalized calibrations. Basically because AdS has a boundary, the analysis of stability is more subtle and qualitatively different from the usual case of Minkowski compactifications. For instance, stable D-branes filling AdS_4 may wrap trivial internal cycles. Our analysis gives a geometric realization of the four-dimensional field theory approach of Freedman and collaborators. Furthermore, the one-to-one correspondence between the supersymmetry conditions of the background and the existence of generalized calibrations for D-branes is clarified and extended to any supersymmetric flux background that admits a time-like Killing vector and for which all fields are time-independent with respect to the associated time. As explicit examples, we discuss supersymmetric D-branes on IIA nearly Kaehler AdS_4 flux compactifications.Comment: 43 pages, 2 pictures, 1 table; v2: added references, color to figure and corrected typo in (6.21b

Statistical trend analysis and extreme distribution of significant wave height from 1958 to 1999 – an application to the Italian Seas

The study is a statistical analysis of sea states timeseries derived using the wave model WAM forced by the ERA-40 dataset in selected areas near the Italian coasts. For the period 1 January 1958 to 31 December 1999 the analysis yields: (i) the existence of a negative trend in the annual- and winter-averaged sea state heights; (ii) the existence of a turning-point in late 80's in the annual-averaged trend of sea state heights at a site in the Northern Adriatic Sea; (iii) the overall absence of a significant trend in the annual-averaged mean durations of sea states over thresholds; (iv) the assessment of the extreme values on a time-scale of thousand years. The analysis uses two methods to obtain samples of extremes from the independent sea states: the <i>r-largest annual maxima</i> and the <i>peak-over-threshold</i>. The two methods show statistical differences in retrieving the return values and more generally in describing the significant wave field. The <i>r-largest annual maxima</i> method provides more reliable predictions of the extreme values especially for small return periods (<100 years). Finally, the study statistically proves the existence of decadal negative trends in the significant wave heights and by this it conveys useful information on the wave climatology of the Italian seas during the second half of the 20th century

MRI and Clinical Biomarkers Overlap between Glaucoma and Alzheimer’s Disease

glaucoma is the leading cause of blindness worldwide. It is classically associated with structural and functional changes in the optic nerve head and retinal nerve fiber layer, but the damage is not limited to the eye. The involvement of the central visual pathways and disruption of brain network organization have been reported using advanced neuroimaging techniques. the brain structural changes at the level of the areas implied in processing visual information could justify the discrepancy between signs and symptoms and underlie the analogy of this disease with neurodegenerative dementias, such as alzheimer’s disease, and with the complex group of pathologies commonly referred to as “disconnection syndromes.” this review aims to summarize the current state of the art on the use of advanced neuroimaging techniques in glaucoma and alzheimer’s disease, highlighting the emerging biomarkers shared by both diseases

Wilson Loop, Regge Trajectory and Hadron Masses in a Yang-Mills Theory from Semiclassical Strings

We compute the one-loop string corrections to the Wilson loop, glueball Regge trajectory and stringy hadron masses in the Witten model of non supersymmetric, large-N Yang-Mills theory. The classical string configurations corresponding to the above field theory objects are respectively: open straight strings, folded closed spinning strings, and strings orbiting in the internal part of the supergravity background. For the rectangular Wilson loop we show that besides the standard Luescher term, string corrections provide a rescaling of the field theory string tension. The one-loop corrections to the linear glueball Regge trajectories render them nonlinear with a positive intercept, as in the experimental soft Pomeron trajectory. Strings orbiting in the internal space predict a spectrum of hadronic-like states charged under global flavor symmetries which falls in the same universality class of other confining models.Comment: 52 pages, latex 3 times, v3: references adde

Ground-based retrieval of continental and marine warm cloud microphysics

A technique for retrieving warm cloud microphysics using synergistic ground based remote sensing instruments is presented. The SYRSOC (SYnergistic Remote Sensing Of Cloud) technique utilises a K<sub><i>a</i></sub>-band Doppler cloud RADAR, a LIDAR (or ceilometer) and a multichannel microwave radiometer. SYRSOC retrieves the main microphysical parameters such as cloud droplet number concentration (CDNC), droplets effective radius (<i>r</i><sub>eff</sub>), cloud liquid water content (LWC), and the departure from adiabatic conditions within the cloud. Two retrievals are presented for continental and marine stratocumulus advected over the Mace Head Atmospheric Research Station. Whilst the continental case exhibited high CDCN (<span style="border-top: 1px solid #000; color: #000;"><i>N</i></span> = 382 cm<sup>−3</sup>; 10th-to-90th percentile [9.4–842.4] cm<sup>−3</sup>) and small mean effective radius (<span style="border-top: 1px solid #000; color: #000;"><i>r</i><sub>eff</sub></span> = 4.3; 10th-to-90th percentile [2.9–6.5] μm), the marine case showed low CDNC and large mean effective radius (<span style="border-top: 1px solid #000; color: #000;"><i>N</i></span> = 25 cm<sup>−3</sup>, 10th-to-90th percentile [1.5–69] cm<sup>−3</sup>; <span style="border-top: 1px solid #000; color: #000;"><i>r</i><sub>eff</sub></span> = 28.4 μm, 10th-to-90th percentile [11.2–42.7] μm) as expected since continental air at this location is typically more polluted than marine air. The mean LWC was comparable for the two cases (continental: 0.19 g m<sup>−3</sup>; marine: 0.16 g m<sup>−3</sup>) but the 10th–90th percentile range was wider in marine air (continental: 0.11–0.22 g m<sup>−3</sup>; marine: 0.01–0.38 g m<sup>−3</sup>). The calculated algorithm uncertainty for the continental and marine case for each variable was, respectively, σ<sub><i>N</i></sub> = 161.58 cm<sup>−3</sup> and 12.2 cm<sup>−3</sup>, σ<sub><i>r</i><sub>eff</sub></sub> = 0.86 μm and 5.6 μm, σ<sub>LWC</sub> = 0.03 g m<sup>−3</sup> and 0.04 g m<sup>−3</sup>. The retrieved CDNC are compared to the cloud condensation nuclei concentrations and the best agreement is achieved for a supersaturation of 0.1% in the continental case and between 0.1%–0.75% for the marine stratocumulus. The retrieved <i>r</i><sub>eff</sub> at the top of the clouds are compared to the MODIS satellite <i>r</i><sub>eff</sub>: 7 μm (MODIS) vs. 6.2 μm (SYRSOC) and 16.3 μm (MODIS) vs. 17 μm (SYRSOC) for continental and marine cases, respectively. The combined analysis of the CDNC and the <i>r</i><sub>eff</sub>, for the marine case shows that the drizzle modifies the droplet size distribution and <span style="border-top: 1px solid #000; color: #000;"><i>r</i><sub>eff</sub></span> especially if compared to <i>r</i><sub>eff</sub><sup>MOD</sup>. The study of the cloud subadiabaticity and the LWC shows the general sub-adiabatic character of both clouds with more pronounced departure from adiabatic conditions in the continental case than in the marine