145 research outputs found
Potential one-forms for hyperk\"ahler structures with torsion
It is shown that an HKT-space with closed parallel potential 1-form has
-symmetry. Every locally conformally hyperk\"ahler manifold
generates this type of geometry. The HKT-spaces with closed parallel potential
1-form arising in this way are characterized by their symmetries and an
inhomogeneous cubic condition on their torsion.Comment: 16 pages, Latex, no figure
Supersymmetric heterotic string backgrounds
We present the main features of the solution of the gravitino and dilatino
Killing spinor equations derived in hep-th/0510176 and hep-th/0703143 which
have led to the classification of geometric types of all type I backgrounds. We
then apply these results to the supersymmetric backgrounds of the heterotic
string. In particular, we solve the gaugino Killing spinor equation together
with the other two Killing spinor equations of the theory. We also use our
results to classify all supersymmetry conditions of ten-dimensional gauge
theory.Comment: 12 pages, v2: gauge theory applications are stressed and references
adde
Highest weight modules over quantum queer Lie superalgebra U_q(q(n))
In this paper, we investigate the structure of highest weight modules over
the quantum queer superalgebra . The key ingredients are the
triangular decomposition of and the classification of finite
dimensional irreducible modules over quantum Clifford superalgebras. The main
results we prove are the classical limit theorem and the complete reducibility
theorem for -modules in the category .Comment: Definition 1.5 and Definition 6.1 are changed, and a remark is added
in the new versio
Potentials for hyper-Kahler metrics with torsion
We prove that locally any hyper-K\"ahler metric with torsion admits an HKT
potential.Comment: 9 page
The odd side of torsion geometry
We introduce and study a notion of `Sasaki with torsion structure' (ST) as an
odd-dimensional analogue of K\"ahler with torsion geometry (KT). These are
normal almost contact metric manifolds that admit a unique compatible
connection with 3-form torsion. Any odd-dimensional compact Lie group is shown
to admit such a structure; in this case the structure is left-invariant and has
closed torsion form.
We illustrate the relation between ST structures and other generalizations of
Sasaki geometry, and explain how some standard constructions in Sasaki geometry
can be adapted to this setting. In particular, we relate the ST structure to a
KT structure on the space of leaves, and show that both the cylinder and the
cone over an ST manifold are KT, although only the cylinder behaves well with
respect to closedness of the torsion form. Finally, we introduce a notion of
`G-moment map'. We provide criteria based on equivariant cohomology ensuring
the existence of these maps, and then apply them as a tool for reducing ST
structures.Comment: 34 pages; v2: added a small generalization (Proposition 3.6) of the
cone construction; two references added. To appear on Ann. Mat. Pura App
Instructor feedback versus no instructor feedback on performance in a laparoscopic virtual reality simulator: a randomized educational trial
<p>Abstract</p> <p>Background</p> <p>Several studies have found a positive effect on the learning curve as well as the improvement of basic psychomotor skills in the operating room after virtual reality training. Despite this, the majority of surgical and gynecological departments encounter hurdles when implementing this form of training. This is mainly due to lack of knowledge concerning the time and human resources needed to train novice surgeons to an adequate level. The purpose of this trial is to investigate the impact of instructor feedback regarding time, repetitions and self-perception when training complex operational tasks on a virtual reality simulator.</p> <p>Methods/Design</p> <p>The study population consists of medical students on their 4<sup>th </sup>to 6<sup>th </sup>year without prior laparoscopic experience. The study is conducted in a skills laboratory at a centralized university hospital. Based on a sample size estimation 98 participants will be randomized to an intervention group or a control group. Both groups have to achieve a predefined proficiency level when conducting a laparoscopic salpingectomy using a surgical virtual reality simulator. The intervention group receives standardized instructor feedback of 10 to 12 min a maximum of three times. The control group receives no instructor feedback. Both groups receive the automated feedback generated by the virtual reality simulator. The study follows the CONSORT Statement for randomized trials. Main outcome measures are time and repetitions to reach the predefined proficiency level on the simulator. We include focus on potential sex differences, computer gaming experience and self-perception.</p> <p>Discussion</p> <p>The findings will contribute to a better understanding of optimal training methods in surgical education.</p> <p>Trial Registration</p> <p><a href="http://www.clinicaltrials.gov/ct2/show/NCT01497782">NCT01497782</a></p
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