M-theory Compactifications to Three Dimensions with M2-brane Potentials

We study a class of compactifications of M-theory to three dimensions that preserve N=2 supersymmetry and which have the defining feature that a probe space-time filling M2 brane feels a non-trivial potential on the internal manifold. Using M-theory/F-theory duality such compactifications include the uplifts of 4-dimensional N=1 type IIB compactifications with D3 potentials to strong coupling. We study the most general 8-dimensional manifolds supporting these properties, derive the most general flux that induces an M2 potential, and show that it is parameterised in terms of two real vectors. We study the supersymmetry equations when only this flux is present and show that over the locus where the M2 potential is non-vanishing the background takes the form of a Calabi-Yau three-fold fibered over a 2-dimensional base spanned by the flux vectors, while at the minima of the potential the flux vanishes. Allowing also for non-vanishing four-form flux with one leg in the internal directions we find that the Calabi-Yau three-fold in the fibration is replaced by an SU(3)-structure manifold with torsion classes satisfying 2 W_4=-W_5.Comment: 40 page

Kosovo's Independence and the Serbian Coalitions against the Kosovar Self-determination

The study addresses the influence that the Kosovo-Serbia binomial has on the regional security architecture in the Western Balkans, comparatively analyzing the two stages of the relations between Belgrade and Pristina, namely the autonomy and the independence. The first section deals with the post-conflict reconstruction of the ex-Yugoslav space, focusing on Kosovo`s status, but above all on the redefinition of the power relations between the central authority and the regional administration. The paper also covers the previous before Kosovo's Declaration of Independence was adopted, presenting Montenegrin separatism as a precedent for the irredentism from southern Serbia and for the formation of the Republic of Kosovo. On this occasion, the international debate on the self-determination of the province, focusing on the nuances between the Euro-Atlantic community and the traditional allies of Serbia, is being pursued, the legality of the argument being deduced from the strategies of the interests of the that exerciceses influence in the Southeastern European space. As such, the friction points during the confrontation transposed into the post-conflict phase, the act of independence being the catalyst for an East-West rupture in terms of the perspective on the principle of self-determination.        At the macro-structural level, the study exposes the post-Cold War transformations of the former the Yugoslav space suffered. Conceptually, the Kosovo war as the first conflictto be fought in the logic of the doctrine of humanitarian intervention, which as a fact is not legally codified. Alongside this, the violation of the sovereignty of a UN state by an intervention unauthorized under a resolution issued by the Security Council would provide support for the hypothesis that Kosovo status is illegal as a result of a violation of the Serbian sovereignty and international law

Posterior Perforation of Gastric Ulcer with Giant Retroperitoneal Abscess – a Rare Case

Spontaneous perforation of a gastric ulcer is a rare entity and can often be overlooked considering the frequently silent clinical picture. The posterior erosion of the ulcer through the omental bursa in the retroperitoneal space determines local inflammation which, together with the fibrosis of the retroperitoneal tissue facilitates the enclosure of the gastric content. We present the case of a 49-year old patient investigated for pain in the upper abdomen. The endoscopy performed one month before the admission described a retractile area with a central ulcer on the posterior surface of the stomach, adjacent to the lesser curvature. Given the fact that the abdominal x-ray was normal, a CT scan was performed and a voluminous retroperitoneal cystic lesion was discovered. Combining all the preoperative information the diagnosis was of retroperitoneal abscess by posterior perforation of a gastric ulcer. Surgical intervention was performed, the abscess was evacuated and its wall was completely resected; because of local conditions a distal hemigastrectomy with Roux en Y gastro-enteroanastomosis was chosen over gastrorhaphy and omentoplasty

M-theory on seven-dimensional manifolds with SU(3) structure

In this paper we study M-theory compactifications on seven-dimensional manifolds with SU(3) structure. As such manifolds naturally pick out a specific direction, the resulting effective theory can be cast into a form which is similar to type IIA compactifications to four dimensions. We derive the gravitino mass matrix in four dimensions and show that for different internal manifolds (torsion classes) the vacuum preserves either no supersymmetry, or N=2 supersymmetry or, through spontaneous partial supersymmetry breaking, N=1 supersymmetry. For the latter case we derive the effective N=1 theory and give explicit examples where all the moduli are stabilised without the need of non-perturbative effects

A Note on Moduli Stabilisation in Heterotic Models in the Presence of Matter Fields

In this brief note we analyse a toy model which can be derived from heterotic string compactifications on half-flat manifolds with SU(3) structure at first order in \alpha' (ie including matter fields). We show that for this model, finding solutions with viable gauge group poses the same problems as finding solutions in the absence of matter fields.Comment: 8 pages; minor changes; version to appear in Physics Letters

Heterotic compactifications and nearly-Kahler manifolds

We propose that under certain conditions heterotic string compactifications on half-flat and nearly-Kahler manifolds are equivalent. Based on this correspondence we argue that the moduli space of the nearly-Kahler manifolds under discussion consists only of the Kahler deformations moduli space and there is no correspondent for the complex structure deformations.Comment: 5 pages, references added, typos correcte

INDUCTIVE COUPLING BETWEEN OVERHEAD POWER LINES AND NEARBY METALLIC PIPELINES. A NEURAL NETWORK APPROACH

The current paper presents an artificial intelligence based technique applied in the investigation of electromagnetic interference problems between high voltage power lines (HVPL) and nearby underground metallic pipelines (MP). An artificial neural network (NN) solution has been implemented by the authors to evaluate the inductive coupling between HVPL and MP for different constructive geometries of an electromagnetic interference problem considering a multi-layer soil structure. Obtained results are compared to solutions provided by a finite element method (FEM) based analysis and considered as reference. The advantage of the proposed method yields in a simplified computation model compared to FEM, and implicitly a lower computational time

Casimir Effect in the Presence of Minimal Lengths

It is expected that the implementation of minimal length in quantum models leads to a consequent lowering of Planck's scale. In this paper, using the quantum model with minimal length of Kempf et al \cite{kempf0}, we examine the effect of the minimal length on the Casimir force between parallel plates.Comment: 10 pages, 2 figure