1,870 research outputs found
Couplings of N=1 chiral spinor multiplets
We derive the action for chiral spinor multiplets coupled to vector and
scalar multiplets. We give the component form of the action, which contains
gauge invariant mass terms for the antisymmetric tensors in the spinor
superfield and additional Green-Schwarz couplings to vector fields. We observe
that supersymmetry provides mass terms for the scalars in the spinor multiplet
which do not arise from eliminating an auxiliary field. We construct the dual
action by explicitly performing the duality transformations in superspace and
give its component form.Comment: 17 pages, v2 small change
Rigid N=2 superconformal hypermultiplets
We discuss superconformally invariant systems of hypermultiplets coupled to
gauge fields associated with target-space isometries.Comment: Invited talk given at the International Seminar "Supersymmetries and
Quantum Symmetries", July 1997, Dubna. Latex, 9 p
Supersymmetric Randall-Sundrum Scenario
We present the supersymmetric version of the minimal Randall-Sundrum model
with two opposite tension branes.Comment: Latex, 9 pages. Published versio
Spinor Algebras
We consider supersymmetry algebras in space-times with arbitrary signature
and minimal number of spinor generators. The interrelation between super
Poincar\'e and super conformal algebras is elucidated. Minimal super conformal
algebras are seen to have as bosonic part a classical semimisimple algebra
naturally associated to the spin group. This algebra, the Spin-algebra,
depends both on the dimension and on the signature of space time. We also
consider maximal super conformal algebras, which are classified by the
orthosymplectic algebras.Comment: References added, misprints corrected. Version to appear in the
Journal of Geometry and Physic
Identification of Limiting Case Between DBA and SBDBA (CL Break Area Sensitivity): A New Model for the Boron Injection System
Atucha-2 is a Siemens-designed PHWR reactor under construction in the Republic of
Argentina. Its geometrical complexity and (e.g., oblique Control Rods, Positive Void coefficient)
required a developed and validated complex three dimensional (3D) neutron kinetics (NK) coupled
thermal hydraulic (TH) model. Reactor shut-down is obtained by oblique CRs and, during
accidental conditions, by an emergency shut-down system (JDJ) injecting a highly concentrated
boron solution (boron clouds) in the moderator tank, the boron clouds reconstruction is obtained
using a CFD (CFX) code calculation. A complete LBLOCA calculation implies the application of
the RELAP5-3D© system code. Within the framework of the third Agreement âNA-SA â
University of Pisaâ a new RELAP5-3D control system for the boron injection system was developed
and implemented in the validated coupled RELAP5-3D/NESTLE model of the Atucha 2 NPP. The
aim of this activity is to find out the limiting case (maximum break area size) for the Peak Cladding
Temperature for LOCAs under fixed boundary conditions
Bianchi Type I Cosmology in N=2, D=5 Supergravity
The dynamics and evolution of Bianchi type I space-times is considered in the
framework of the four-dimensional truncation of a reduced theory obtained from
the N=2,D=5 supergravity. The general solution of the gravitational field
equations can be represented in an exact parametric form. All solutions have a
singular behavior at the initial/final moment, except when the space-time
geometry reduces to the isotropic flat case. Generically the obtained
cosmological models describe an anisotropic, expanding or collapsing, singular
Universe with a non-inflationary evolution for all times.Comment: revised version to appear in PR
A Neural-based Algorithm for Landslide Detection at Stromboli Volcano: Preliminary Results.
This study presents a neural-based algorithm for the automatic detection
of landslides on Stromboli volcano (Italy). It has been shown that landslides are an
important short-term precursor of effusive eruptions of Stromboli. In particular, an
increase in the occurrence rate of landslides was observed a few hours before the
beginning of the February 2007 effusive eruption. Automating the process of
detection of these signals will help analysts and represents a useful tool for the
monitoring of the stability of the Sciara del Fuoco flank of Stromboli volcano. A
multi-layer perceptron neural network is here applied to continuously discriminate
landslides from other signals recorded at Stromboli (e.g., explosion quakes, tremor
signals), and its output is used by an automatic system for the detection task. To
correctly represent the seismic data, coefficients are extracted from both the
frequency domain, using the linear predictive coding technique, and the time
domain, using temporal waveform parameterization. The network training and
testing was carried out using a dataset of 537 signals, from 267 landslides and 270
records that included explosion quakes and tremor signals. The classification
results were 99.5% predictive for the best net performance, and 98.7% when the
performance was averaged over the different net configurations. Thus, this
detection system was effective when tested on the 2007 effusive eruption period.
However, continuing investigations into different time intervals are needed, to
further define and optimize the algorithm
Metastable de Sitter vacua in N=2 to N=1 truncated supergravity
We study the possibility of achieving metastable de Sitter vacua in general
N=2 to N=1 truncated supergravities without vector multiplets, and compare with
the situations arising in N=2 theories with only hypermultiplets and N=1
theories with only chiral multiplets. In N=2 theories based on a quaternionic
manifold and a graviphoton gauging, de Sitter vacua are necessarily unstable,
as a result of the peculiar properties of the geometry. In N=1 theories based
on a Kahler manifold and a superpotential, de Sitter vacua can instead be
metastable provided the geometry satisfies some constraint and the
superpotential can be freely adjusted. In N=2 to N=1 truncations, the crucial
requirement is then that the tachyon of the mother theory be projected out from
the daughter theory, so that the original unstable vacuum is projected to a
metastable vacuum. We study the circumstances under which this may happen and
derive general constraints for metastability on the geometry and the gauging.
We then study in full detail the simplest case of quaternionic manifolds of
dimension four with at least one isometry, for which there exists a general
parametrization, and study two types of truncations defining Kahler
submanifolds of dimension two. As an application, we finally discuss the case
of the universal hypermultiplet of N=2 superstrings and its truncations to the
dilaton chiral multiplet of N=1 superstrings. We argue that de Sitter vacua in
such theories are necessarily unstable in weakly coupled situations, while they
can in principle be metastable in strongly coupled regimes.Comment: 40 pages, no figure
Anatomska rekonstrukcija prednjeg kriĆŸnog ligamenta
Tears of the anterior cruciate ligament (ACL) are one of the most common injuries to active individuals. The history of reconstructing a ruptured ACL has undergone many advances from open, extra-articular reconstructions, to modern day advanced arthroscopic techniques. Some of these new arthroscopic techniques use small incisions and standardized instruments reducing the surgical time, however, they fail to restore the native ACL anatomy. Recent studies have shown that non-anatomical reconstruction might result in suboptimal clinical outcomes. As a result, anatomic ACL reconstruction has gained popularity. The cornerstone of anatomic ACL reconstruction is the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. This article is meant to provide the most up-to-date literature review regarding anatomic ACL reconstruction.Ozljede prednjeg kriĆŸnog ligament (PKL) spadaju meÄu najÄeĆĄÄe sportske ozljede koljena. Povijest rekonstrukcije PKL-a preĆĄla je dug put od otvorenih metoda do danaĆĄnji modernih artroskopskih tehnika. Pri nekim artroskopskim tehnikama koriste se male incizije uz upotrebu standardiziranih instrumenata, Äime se znaÄajno skraÄuje vrijeme operacije, ali se ne uspijeva u cijelosti rekonstruirati anatomsko hvatiĆĄte PKL-a. Novije studije pokazale su da se takvim rekonstrukcijama ne uspijevaju postiÄi zadovoljavajuÄi kliniÄki rezultati. Cilj anatomske rekonstrukcije jest rekonstukcija prirodne duljine i promjera PKL-a, orijetnacije kolagenih vlakana i anatomskih hvatiĆĄta. U ovom radu dajemo pregled najnovije literature koja se bavi anatomskom rekonstrukcijom PKL-a
Alleviating the non-ultralocality of coset sigma models through a generalized Faddeev-Reshetikhin procedure
The Faddeev-Reshetikhin procedure corresponds to a removal of the
non-ultralocality of the classical SU(2) principal chiral model. It is realized
by defining another field theory, which has the same Lax pair and equations of
motion but a different Poisson structure and Hamiltonian. Following earlier
work of M. Semenov-Tian-Shansky and A. Sevostyanov, we show how it is possible
to alleviate in a similar way the non-ultralocality of symmetric space sigma
models. The equivalence of the equations of motion holds only at the level of
the Pohlmeyer reduction of these models, which corresponds to symmetric space
sine-Gordon models. This work therefore shows indirectly that symmetric space
sine-Gordon models, defined by a gauged Wess-Zumino-Witten action with an
integrable potential, have a mild non-ultralocality. The first step needed to
construct an integrable discretization of these models is performed by
determining the discrete analogue of the Poisson algebra of their Lax matrices.Comment: 31 pages; v2: minor change
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