14,248 research outputs found
Off-shell supergravity-matter couplings in three dimensions
We develop the superspace geometry of N-extended conformal supergravity in
three space-time dimensions. General off-shell supergravity-matter couplings
are constructed in the cases N=1,2,3,4.Comment: 73 pages; V5: typos in eqs. (3.4b), (3.17) and (4.24) correcte
Heterotic-Type II duality in the hypermultiplet sector
We revisit the duality between heterotic string theory compactified on K3 x
T^2 and type IIA compactified on a Calabi-Yau threefold X in the hypermultiplet
sector. We derive an explicit map between the field variables of the respective
moduli spaces at the level of the classical effective actions. We determine the
parametrization of the K3 moduli space consistent with the Ferrara-Sabharwal
form. From the expression of the holomorphic prepotential we are led to
conjecture that both X and its mirror must be K3 fibrations in order for the
type IIA theory to have an heterotic dual. We then focus on the region of the
moduli space where the metric is expressed in terms of a prepotential on both
sides of the duality. Applying the duality we derive the heterotic
hypermultiplet metric for a gauge bundle which is reduced to 24 point-like
instantons. This result is confirmed by using the duality between the heterotic
theory on T^3 and M-theory on K3. We finally study the hyper-Kaehler metric on
the moduli space of an SU(2) bundle on K3.Comment: 27 pages; references added, typos correcte
Interpreting physical performance in professional soccer match-play: Should we be more pragmatic in our approach?
Academic and practitioner interest in the physical performance of male professional soccer players in the competition setting determined via time-motion analyses has grown substantially over the last four decades leading to a substantial body of published research and aiding development of a more systematic evidence-based framework for physical conditioning. Findings have forcibly shaped contemporary opinions in the sport with researchers and practitioners frequently emphasising the important role that physical performance plays in match outcomes. Time-motion analyses have also influenced practice as player conditioning programmes can be tailored according to the different physical demands identified across individual playing positions. Yet despite a more systematic approach to physical conditioning, data indicate that even at the very highest standards of competition, the contemporary player is still susceptible to transient and end-game fatigue. Over the course of this article, the author suggests that a more pragmatic approach to interpreting the current body of time-motion analysis data and its application in the practical setting is nevertheless required. Examples of this are addressed using findings in the literature to examine: a) the association between competitive physical performance and âsuccessâ in professional soccer, b) current approaches to interpreting differences in time-motion analysis data across playing positions and, c) whether data can realistically be used to demonstrate the occurrence of fatigue in match-play. Gaps in the current literature and directions for future research are also identified
N=2 supergravity and supercurrents
We address the problem of classifying all N=2 supercurrent multiplets in four
space-time dimensions. For this purpose we consider the minimal formulation of
N=2 Poincare supergravity with a tensor compensator, and derive its linearized
action in terms of three N=2 off-shell multiplets: an unconstrained scalar
superfield, a vector multiplet, and a tensor multiplet. Such an action was
ruled out to exist in the past. Using the action constructed, one can derive
other models for linearized N=2 supergravity by applying N=2 superfield duality
transformations. The action depends parametrically on a constant non-vanishing
real isotriplet g^{ij}=g^{ji} which originates as an expectation value of the
tensor compensator. Upon reduction to N=1 superfields, we show that the model
describes two dually equivalent formulations for the massless multiplet
(1,3/2)+(3/2,2) depending on a choice of g^{ij}. In the case g^{11}=g^{22}=0,
the action describes (i) new minimal N=1 supergravity; and (ii) the
Fradkin-Vasiliev-de Wit-van Holten gravitino multiplet. In the case g^{12}=0,
on the other hand, the action describes (i) old minimal N=1 supergravity; and
(ii) the Ogievetsky-Sokatchev gravitino multiplet.Comment: 40 pages; v2: added references, some comments, new appendi
From correlation functions to scattering amplitudes
We study the correlators of half-BPS protected operators in N=4
super-Yang-Mills theory, in the limit where the positions of the adjacent
operators become light-like separated. We compute the loop corrections by means
of Lagrangian insertions. The divergences resulting from the light-cone limit
are regularized by changing the dimension of the integration measure over the
insertion points. Switching from coordinates to dual momenta, we show that the
logarithm of the correlator is identical with twice the logarithm of the
matching MHV gluon scattering amplitude. We present a number of examples of
this new relation, at one and two loops.Comment: typos corrected, references adde
Acute-on-chronic liver failure in cirrhosis
The definition of acute-on-chronic liver failure (ACLF) remains contested. In Europe and North America, the term is generally applied according to the European Association for the Study of the Liver-Chronic Liver Failure (EASL-CLIF) Consortium guidelines, which defines this condition as a syndrome that develops in patients with cirrhosis and is characterized by acute decompensation, organ failure and high short-term mortality. One-third of patients who are hospitalized for acute decompensation present with ACLF at admission or develop the syndrome during hospitalization. ACLF frequently occurs in a closed temporal relationship to a precipitating event, such as bacterial infection or acute alcoholic, drug-induced or viral hepatitis. However, no precipitating event can be identified in approximately 40% of patients. The mechanisms of ACLF involve systemic inflammation due to infections, acute liver damage and, in cases without precipitating events, probably intestinal translocation of bacteria or bacterial products. ACLF is graded into three stages (ACLF grades 1â3) on the basis of the number of organ failures, with higher grades associated with increased mortality. Liver and renal failures are the most common organ failures, followed by coagulation, brain, circulatory and respiratory failure. The 28-day mortality rate associated with ACLF is 30%. Depending on the grade, ACLF can be reversed using standard therapy in only 16â51% of patients, leaving a considerable proportion of patients with ACLF that remains steady or progresses. Liver transplantation in selected patients with ACLF grade 2 and ACLF grade 3 increases the 6-month survival from 10% to 80%
Acute-on-Chronic Liver Failure: Definition, Diagnosis, and Clinical Characteristics
Acute-on-chronic liver failure (ACLF) is a recently recognized syndrome in cirrhosis characterized by acute decompensation (AD), organ failure(s), and high short-term mortality. Organ failure(s) is defined by the Chronic Liver Failure-Sequential Organ Failure (CLIF-SOFA) score or by its simplified version Chronic Liver Failure-Organ Failure Assessment (CLIF-OF) score. They include six types of organ failure: liver, renal, coagulation, cerebral, respiratory, and circulatory. One third of patients hospitalized with AD present with ACLF at admission or develop ACLF during hospitalization. Acute-on-chronic liver failure frequently occurs in a closed relationship to a precipitating event. According to the number of organ failures, ACLF is graded into three stages: ACLF-1â=âsingle renal failure or single nonrenal organ failure if associated with renal dysfunction and/or cerebral dysfunction; ACLF-2â=âtwo organ failures; and ACLF-3â=âthree to six organ failures, with increasing 28-day mortality rate (from 23%â74%). Acute-on-chronic liver failure may develop at any phase during the clinical course of the disease. Patients without prior AD develop a severe form of ACLF
A validation of the Oswestry Spinal Risk Index
Purpose
The purpose of this study was to validate the Oswestry Spinal Risk Index (OSRI) in an external population. The OSRI predicts survival in patients with metastatic spinal cord compression (MSCC).
Methods
We analysed the data of 100 patients undergoing surgical intervention for MSCC at a tertiary spinal unit and recorded the primary tumour pathology and Karnofsky performance status to calculate the OSRI. Logistic regression models and survival plots were applied to the data in accordance with the original paper.
Results
Lower OSRI scores predicted longer survival. The OSRI score predicted survival accurately in 74% of cases (p = 0.004).
Conclusions
Our study has found that the OSRI is a significant predictor of survival at levels similar to those of the original authors and is a useful and simple tool in aiding complex decision making in patients presenting with MSC
Global Properties of Topological String Amplitudes and Orbifold Invariants
We derive topological string amplitudes on local Calabi-Yau manifolds in
terms of polynomials in finitely many generators of special functions. These
objects are defined globally in the moduli space and lead to a description of
mirror symmetry at any point in the moduli space. Holomorphic ambiguities of
the anomaly equations are fixed by global information obtained from boundary
conditions at few special divisors in the moduli space. As an illustration we
compute higher genus orbifold Gromov-Witten invariants for C^3/Z_3 and C^3/Z_4.Comment: 34 pages, 3 figure
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