Second harmonic generation in anisotropic stratified media: A generalization of the Berreman method and its application to photonic materials

We have developed a numerical method for calculating the second harmonic generation (SHG) generated by an anisotropic material whose optical properties present an arbitrary modulation in one dimension. The method is based on the Berreman 4x4 matrix formalism, which is generalized to include nonlinear optical phenomena. It can be used under oblique incidences of the input beam, and is valid even when the SHG frequency is close to photonic bands, where the usual slowly-varying-amplitude approximation breaks down. As an example of application, we have studied the SHG performance of ferroelectric and helielectric nematic liquid crystals. The latter present a helicoidal structure that can be distorted under electric field. In the different tests of the method we have analyzed the conditions for the most efficient SHG, and compared with previous results in the case there were any. The obtained results indicate that the present procedure may contribute to improve the structural design and enlarge the variety of nonlinear optical materials for their application in optical devices.Comment: 14 pages, 6 figure

Non-Perturbative Effects on a Fractional D3-Brane

In this note we study the N=1 abelian gauge theory on the world volume of a single fractional D3-brane. In the limit where gravitational interactions are not completely decoupled we find that a superpotential and a fermionic bilinear condensate are generated by a D-brane instanton effect. A related situation arises for an isolated cycle invariant under an orientifold projection, even in the absence of any gauge theory brane. Moreover, in presence of supersymmetry breaking background fluxes, such instanton configurations induce new couplings in the 4-dimensional effective action, including non-perturbative contributions to the cosmological constant and non-supersymmetric mass terms.Comment: 18 pages, v3: refs adde

A natural renormalizable model of metastable SUSY breaking

We propose a model of metastable dynamical supersymmetry breaking in which all scales are generated dynamically. Our construction is a simple variant of the Intriligator-Seiberg-Shih model, with quark masses induced by renormalizable couplings to an auxiliary supersymmetric QCD sector. Since all scales arise from dimensional transmutation, the model has no fundamental dimensionful parameters. It also does not rely on higher-dimensional operators.Comment: 9 pages; v2: typos correcte

Meta-Stable Brane Configurations by Adding an Orientifold-Plane to Giveon-Kutasov

In hep-th/0703135, they have found the type IIA intersecting brane configuration where there exist three NS5-branes, D4-branes and anti-D4-branes. By analyzing the gravitational interaction for the D4-branes in the background of the NS5-branes, the phase structures in different regions of the parameter space were studied in the context of classical string theory. In this paper, by adding the orientifold 4-plane and 6-plane to the above brane configuration, we describe the intersecting brane configurations of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of these gauge theories.Comment: 21 pp, 6 figures; reduced bytes of figures, DBI action analysis added and to appear in JHE

Four-modulus "Swiss Cheese" chiral models

We study the 'Large Volume Scenario' on explicit, new, compact, four-modulus Calabi-Yau manifolds. We pay special attention to the chirality problem pointed out by Blumenhagen, Moster and Plauschinn. Namely, we thoroughly analyze the possibility of generating neutral, non-perturbative superpotentials from Euclidean D3-branes in the presence of chirally intersecting D7-branes. We find that taking proper account of the Freed-Witten anomaly on non-spin cycles and of the Kaehler cone conditions imposes severe constraints on the models. Nevertheless, we are able to create setups where the constraints are solved, and up to three moduli are stabilized.Comment: 40 pages, 10 figures, clarifying comments added, minor mistakes correcte

Magnetic properties of cherts from the basque-cantabrian basin and surrounding regions: Archeological implications

We present the first rock magnetic study of archeologically-relevant chert samples from the Basque-Cantabrian basin (BCB) and surrounding regions, which was conducted in order to test the usefulness of non-destructive magnetic properties for assessing chert quality, distinguishing source areas, and identifying heated samples in the archeological record. Our results indicate that the studied BCB cherts are diamagnetic and have very low amounts of magnetic minerals. The only exception is the chert of Artxilondo, which has a median positive magnetic susceptibility associated with larger concentrations of magnetic minerals. But even in this case, the magnetic susceptibility is within the lower range of other archeologically-relevant cherts elsewhere, which indicates that the studied BCB cherts can be considered as flint. The similar median values for all magnetic properties, along with their associated large interquartile ranges, indicates that rock magnetic methods are of limited use for sourcing different types of flint except in some specific contexts involving the Artxilondo flint. With regards to the identification of chert heating in the archeological record, our results indicate only a minor magnetic enhancement of BCB natural flint samples upon heating, which we attribute to the low amount of non-silica impurities. In any case, the diamagnetic behavior of most BCB natural flints, along with the local use only of the Artxilondo type, suggests that any flint tool within the core of the BCB with positive magnetic susceptibility values is likely to have been subjected to heating for improving its knapping properties. Further studies are necessary to better identify the type, origin and grain size of magnetic minerals in BCB natural flints, and to apply non-destructive magnetic properties to flint tools in order to identify the use of heat treatment in the BCB archeological record. © 2016 Larrasoaña, Beamud, Olivares, Murelaga, Tarriño, Baceta and Etxebarria.This study was funded by project GUI15/34 of the Universidad del País Vasco.Peer reviewe

Toric AdS4/CFT3 duals and M-theory Crystals

We study the recently proposed crystal model for three dimensional superconformal field theories arising from M2-branes probing toric Calabi-Yau four-fold singularities. We explain the algorithms mapping a toric Calabi-Yau to a crystal and vice versa, and show how the spectrum of BPS meson states fits into the crystal model.Comment: 24 pages, 24 figure

D-brane instantons and the effective field theory of flux compactifications

We provide a description of the effects of fluxes on euclidean D-brane instantons purely in terms of the 4d effective action. The effect corresponds to the dressing of the effective non-perturbative 4d effective vertex with 4d flux superpotential interactions, generated when the moduli fields made massive by the flux are integrated out. The description in terms of effective field theory allows a unified description of non-perturbative effects in all flux compactifications of a given underlying fluxless model, globally in the moduli space of the latter. It also allows us to describe explicitly the effects on D-brane instantons of fluxes with no microscopic description, like non-geometric fluxes. At the more formal level, the description has interesting connections with the bulk-boundary map of open-closed two-dimensional topological string theory, and with the \NN=1 special geometry.Comment: 33 page

Structural analysis of APOB variants, p.(Arg3527Gln), p.(Arg1164Thr) and p.(Gln4494del), causing Familial Hypercholesterolaemia provides novel insights into variant pathogenicity

Free PMC Article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672294/Familial hypercholesterolaemia (FH) is an inherited autosomal dominant disorder resulting from defects in the low-density lipoprotein receptor (LDLR), in the apolipoprotein B (APOB) or in the proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. In the majority of the cases FH is caused by mutations occurring within LDLR, while only few mutations in APOB and PCSK9 have been proved to cause disease. p.(Arg3527Gln) was the first mutation in APOB being identified and characterized. Recently two novel pathogenic APOB variants have been described: p.(Arg1164Thr) and p.(Gln4494del) showing impaired LDLR binding capacity, and diminished LDL uptake. The objective of this work was to analyse the structure of p.(Arg1164Thr) and p.(Gln4494del) variants to gain insight into their pathogenicity. Secondary structure of the human ApoB100 has been investigated by infrared spectroscopy (IR) and LDL particle size both by dynamic light scattering (DLS) and electron microscopy. The results show differences in secondary structure and/or in particle size of p.(Arg1164Thr) and p.(Gln4494del) variants compared with wild type. We conclude that these changes underlie the defective binding and uptake of p.(Arg1164Thr) and p.(Gln4494del) variants. Our study reveals that structural studies on pathogenic variants of APOB may provide very useful information to understand their role in FH disease