Intersecting Brane Vacua and Non-perturbative Transitions

We discuss the process of transmutation of branes into Abelian magnetic flux on the worldvolume of $D9$ branes. This phenomenon is T-dual to the recombination of branes in the intersecting-brane description. In the low energy limit this can be described by a Higgs mechanism involving bifundamental scalars. The Abelian magnetic background arises as a consequence of the compactness of the internal space. Explicit (six-dimensional) examples based on the supersymmetric and the Brane Supersymmetry Breaking (BSB) \mathbb{T}^4/\mathbb{Z}_2 orientifold are analyzed.Comment: 5 pages, LaTex. Contribution to the proceedings of the 2011 Europhysics Conference on High Energy Physics, EPS-HEP 2011. Reference added in v

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

Open Strings and Electric Fields in Compact Spaces

We analyse open strings with background electric fields in the internal space, T-dual to branes moving with constant velocities in the internal space. We find that the direction of the electric fields inside a two torus, dual to the D brane velocities, has to be quantised such that the corresponding direction is compact. This implies that D-brane motion in the internal torus is periodic, with a periodicity that can be parametrically large in terms of the internal radii. By S-duality, this is mapped into an internal magnetic field in a three torus, a quantum mechanical analysis of which yields a similar result, i.e. the parallel direction to the magnetic field has to be compact. Furthermore, for the magnetic case, we find the Landau level degeneracy as being given by the greatest common divisor of the flux numbers. We carry on the string quantisation and derive the relevant partition functions for these models. Our analysis includes also the case of oblique electric fields which can arise when several stacks of branes are present. Compact dimensions and/or oblique sectors influence the energy loss of the system through pair-creation and thus can be relevant for inflationary scenarios with branes. Finally, we show that the compact energy loss is always larger than the non-compact one.Comment: 44 pages, 4 figures; v2 corrections in section 8, one reference adde

Stringy Instanton Effects in Models with Rigid Magnetised D-branes

We compute instantonic effects in globally consistent T^6/Z2xZ2 orientifold models with discrete torsion and magnetised D-branes. We consider fractional branes and instantons wrapping the same rigid cycles. We clarify and analyse in detail the low-energy effective action on D-branes in these models. We provide explicit examples where instantons induce linear terms in the charged fields, or non-perturbative mass terms are generated. We also find examples where the gauge theory on fractional branes has conformal symmetry at one-loop, broken by instantonic mass terms at a hierarchically small energy scale.Comment: 60 pages. Refs added. Typos corrected in some eqs. Modified comments in subsection 4.

Gauged supergravities and non-geometric Q/R-fluxes from asymmetric orbifold CFT's

We investigate the orbifold limits of string theory compactifications with geometric and non-geometric fluxes. Exploiting the connection between internal fluxes and structure constants of the gaugings in the reduced supergravity theory, we can identify the types of fluxes arising in certain classes of freely-acting symmetric and asymmetric orbifolds. We give a general procedure for deriving the gauge algebra of the effective gauged supergravity using the exact CFT description at the orbifold point. We find that the asymmetry is, in general, related to the presence of non-geometric Q- and R- fluxes. The action of T-duality is studied explicitly on various orbifold models and the resulting transformation of the fluxes is derived. Several explicit examples are provided, including compactifications with geometric fluxes, Q-backgrounds (T-folds) and R-backgrounds. In particular, we present an asymmetric Z4xZ2 orbifold in which all geometric and non-geometric fluxes {\omega}, H, Q, R are turned on simultaneously. We also derive the corresponding flux backgrounds, which are not in general T-dual to geometric ones, and may even simultaneously depend non-trivially on both the coordinates and their winding T-duals.Comment: 49p, updated reference

HPV-Positive Oral Squamous Cell Carcinoma

Head and neck malignancies represent the sixth most frequent type of cancer currently in worldwide statistics. Of these, oral and pharyngeal cancers have steadily increased, being linked with the increase in HPV infection pandemic. This rise is not due to one cause, but rather multiple factors such as lifestyle and sexual behavior pattern changes and globalization. Because of the anatomy of the oral cavity and oropharynx, the proper diagnosis is easily delayed, and patients present with advanced stage disease, which requires aggressive and extensive surgery along with neck dissection and chemoradiotherapy. Patients with advanced stage disease have a high recurrence risk with a low 5-year survival rate. Preventing the HPV infection is of course desirable, but right now, for adults which already are infected and have a higher risk of developing HPV-related neoplasias, as well as for our head and neck cancer patients, alternative treatment algorithms are necessary

T-duality and non-geometric solutions from double geometry

Although the introduction of generalised and extended geometry has been motivated mainly by the appearance of dualities upon reductions on tori, it has until now been unclear how (all) the duality transformations arise from first principles in extended geometry. A proposal for solving this problem is given in the framework of double field theory. It is based on a clearly defined extension of the definition of gauge symmetry by isometries of an underlying pseudo-Riemannian manifold. The ensuing relation between transformations of coordinates and fields, which is now derived from first principles, differs from earlier proposals.Comment: 13 pp., plain te

Orbital complications of acute rhinosinusitis

Introduction. Rhinosinusitis is the infection and inflammation of at least one of the 4 paranasal sinuses (frontal, maxillary, ethmoid and sphenoid). Their correct diagnosis is generally determined by examining the patient clinically and by rhinosinusal endoscopic examination. There are also cases that show complications or continued evolution despite the correct treatment, and then we will use some imaging investigations to find out more about affection(radiography of anterior sinuses of the face, sinus computerized tomography, sinus magnetic resonance imaging). In particular, acute rhinosinusitis should be carefully managed to avoid complications such as the local ones: orbital cellulitis, orbital abscess, osteomyelitis, cavernous sinus thrombosis; and intracranial complications: meningitis, epidural abscess, subdural abscess, cerebral abscess.Materials and methods. There will be presented all orbital complications according to the cases treated in the ENT Clinic of the Coltea Clinical Hospital.Conclusions. Diagnosis of rhinosinusitis is largely clinical and endoscopic.When complications of the condition arise, these should be investigated imagistically to determine their exact extent and to institute the correct treatment as soon as possible. The complications of rhinosinusitis are medical and surgical life-threatening emergencies, which is why in order to diagnose and correct and quickly institute therapy requires a multidisciplinary approach

Asymmetric Orbifolds, Non-Geometric Fluxes and Non-Commutativity in Closed String Theory

In this paper we consider a class of exactly solvable closed string flux backgrounds that exhibit non-commutativity in the closed string coordinates. They are realized in terms of freely-acting asymmetric Z_N-orbifolds, which are themselves close relatives of twisted torus fibrations with elliptic Z_N-monodromy (elliptic T-folds). We explicitly construct the modular invariant partition function of the models and derive the non-commutative algebra in the string coordinates, which is exact to all orders in {\alpha}'. Finally, we relate these asymmetric orbifold spaces to inherently stringy Scherk-Schwarz backgrounds and non-geometric fluxes.Comment: 30 page