621 research outputs found
N=1,2 supersymmetric vacua of IIA supergravity and SU(2) structures
We consider backgrounds of (massive) IIA supergravity of the form of a warped
product , where is a six-dimensional compact
manifold and is or a four-dimensional Minkowski space. We
analyse conditions for and supersymmetry on
manifolds of SU(2) structure. We prove the absence of solutions in certain
cases.Comment: 24 pages; v2: reference adde
Towards reduction of type II theories on SU(3) structure manifolds
We revisit the reduction of type II supergravity on SU(3) structure
manifolds, conjectured to lead to gauged N=2 supergravity in 4 dimensions. The
reduction proceeds by expanding the invariant 2- and 3-forms of the SU(3)
structure as well as the gauge potentials of the type II theory in the same set
of forms, the analogues of harmonic forms in the case of Calabi-Yau reductions.
By focussing on the metric sector, we arrive at a list of constraints these
expansion forms should satisfy to yield a base point independent reduction.
Identifying these constraints is a first step towards a first-principles
reduction of type II on SU(3) structure manifolds.Comment: 20 pages; v2: condition (2.13old) on expansion forms weakened,
replaced by (2.13new), (2.14new
Canonical differential geometry of string backgrounds
String backgrounds and D-branes do not possess the structure of Lorentzian
manifolds, but that of manifolds with area metric. Area metric geometry is a
true generalization of metric geometry, which in particular may accommodate a
B-field. While an area metric does not determine a connection, we identify the
appropriate differential geometric structure which is of relevance for the
minimal surface equation in such a generalized geometry. In particular the
notion of a derivative action of areas on areas emerges naturally. Area metric
geometry provides new tools in differential geometry, which promise to play a
role in the description of gravitational dynamics on D-branes.Comment: 20 pages, no figures, improved journal versio
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
Shot, scene and keyframe ordering for interactive video re-use
This paper presents a complete system for shot and scene detection in broadcast videos, as well as a method to select the best representative key-frames, which could be used in new interactive interfaces for accessing large collections of edited videos. The final goal is to enable an improved access to video footage and the re-use of video content with the direct management of user-selected video-clips
Non-Kaehler attracting manifolds
We observe that the new attractor mechanism describing IIB flux vacua for
Calabi-Yau compactifications has a possible extension to the landscape of
non-Kaehler vacua that emerge in heterotic compactifications with fluxes. We
focus on the effective theories coming from compactifications on generalized
half-flat manifolds, showing that the Minkowski "attractor points'' for 3-form
fluxes are special-hermitian manifolds.Comment: 18 pages. v2: Minor polishing, reference added. v3: More cleanup,
final version for JHE
Burkitt's lymphoma in pregnant woman: Difficult management of a rare case
Introduction: Burkitt's lymphoma (BL), an aggressive subtype of non-Hodgkin lymphoma (NHL), is extremely rare during pregnancy. In the case of bowel localization, diagnosis can be very difficult. Moreover, signs and symptoms of the primary small intestine lymphoma are nonspecific, mostly attributable to the “mass effect” of the tumor. The most frequent symptom is abdominal cramp-like pain, associated with nausea and vomiting. Presentation of case: We report a rare case of a 37-year-old pregnant woman, at the 33rd week of gestation, with an abdominal-pelvic mass of uncertain nature. Surgical strategy consisted of a two-step procedure, which involved a cesarean section and typing of the mass: extemporaneous examination hypothesized intestinal lymphoma. The definitive histological examination confirmed the diagnosis of rare case of BL in pregnancy. Discussion: The clinical case reported, representing a rare occurrence of BL in pregnancy, was associated with difficult interpretation and complex management. Lymphoma of the small intestine is often overlooked in the early stages of the disease, due to the fact that symptoms are non-specific and consequently underestimated. In our case, based on gestational age, it was possible to perform a multidisciplinary approach, a cesarean section with surgical intestinal exploration, achieving at the same time delivery of the child and a definitive diagnosis of BL with intestinal involvement. Conclusion: The involvement of multiple professionals is undoubtedly the best way to deal with the above referred to situation, with the main point being to keep in mind the possibility of this type of occurrence
Conifolds and Geometric Transitions
Conifold geometries have recieved a lot of attention in string theory and
string-inspired cosmology recently, in particular the Klebanov-Strassler
background that is known as the "warped throat". It is our intention in this
article to give a pedagogical explanation for the singularity resolution in
this geometry and emphasise its connection to geometric transitions. The first
part focuses on the gauge theory dual to the Klebanov-Strassler background,
which we also explain from a T-dual intersecting branes scenario. We then make
the connection to the Gopakumar-Vafa conjecture for open/closed string duality
and summarise a series of papers verifying this model on the supergravity
level.
An appendix provides extensive background material about conifold geometries.
We pay special attention to their complex structures and re-evaluate the
supersymmetry conditions on the background flux in constructions with
fractional D3-branes on the singular (Klebanov-Tseytlin) and resolved (Pando
Zayas-Tseytlin) conifolds. We agree with earlier results that only the singular
solution allows a supersymmetric flux, but point out the importance of using
the correct complex structure to reach this conclusion.Comment: 37 pages, v3: accepted for publication in Reviews of Modern Physic
Efficacy of 90Y ibritumomab-tiuxetan treatment in a case of resistant gastric MALT non-Hodgkin’s lymphoma
Treatment modalities for resistant/relapsing gastric mucosa associated lymphoid tissue (MALT) non-Hodgkin’s lymphoma (NHL) are not yet well standardized. In the past, most patients were treated surgically with a gastrectomy, while, more recently, radiotherapy and systemic approaches (chemotherapy and immunotherapy) have been used with improving results
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