9 research outputs found
A new twist on dS/CFT
We stress that the dS/CFT correspondence should be formulated using unitary
principal series representations of the de Sitter isometry group/conformal
group, rather than highest-weight representations as originally proposed. These
representations, however, are infinite-dimensional, and so do not account for
the finite gravitational entropy of de Sitter space in a natural way. We then
propose to replace the classical isometry group by a q-deformed version. This
is carried out in detail for two-dimensional de Sitter and we find that the
unitary principal series representations deform to finite-dimensional unitary
representations of the quantum group. We believe this provides a promising
microscopic framework to account for the Bekenstein-Hawking entropy of de
Sitter space.Comment: 21 pages, revtex, v2 references adde
Dwelling on de Sitter
A careful reduction of the three-dimensional gravity to the Liouville
description is performed, where all gauge fixing and on-shell conditions come
from the definition of asymptotic de Sitter spaces. The roles of both past and
future infinities are discussed and the conditions space-time evolution imposes
on both Liouville fields are explicited. Space-times which correspond to
non-equivalent profiles of the Liouville field at past and future infinities
are shown to exist. The qualitative implications of this for any tentative dual
theory are presented.Comment: RevTeX 4, 8 pages, v3: Small clarifications on sections III and IV
and references added/corrected, v4: typo
Perioperative care of the elderly oncology patient: A report from the SIOG task force on the perioperative care of older patients with cancer
Perioperative Medicine: Efficacy, Safety and Outcom
Perioperative care of the elderly oncology patient: a report from the SIOG task force on the perioperative care of older patients with cancer
The increasing number of older cancer patients seen in daily practice demands reflection on how to optimize their care during the perioperative period. Optimally tailored surgical management, at present the most successful cancer treatment, firmly rests on an accurate and careful anesthesiological management.The unique peculiarities of anesthesia in older cancer patients prompted the International Society of Geriatric Oncology (SIOG) to put together a panel of international experts with the aim of reviewing the literature and drafting a consensus document. This article summarizes their views
Episodes of cross-polar transport in the Arctic troposphere during July 2008 as seen from models, satellite, and aircraft observations
During the POLARCAT summer campaign in 2008, two episodes (2g-5 July and 7g-10 July 2008) occurred where low-pressure systems traveled from Siberia across the Arctic Ocean towards the North Pole. The two cyclones had extensive smoke plumes from Siberian forest fires and anthropogenic sources in East Asia embedded in their associated air masses, creating an excellent opportunity to use satellite and aircraft observations to validate the performance of atmospheric transport models in the Arctic, which is a challenging model domain due to numerical and other complications. Here we compare transport simulations of carbon monoxide (CO) from the Lagrangian transport model FLEXPART and the Eulerian chemical transport model TOMCAT with retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite. The main aspect of the comparison is how realistic horizontal and vertical structures are represented in the model simulations. Analysis of CALIPSO lidar curtains and in situ aircraft measurements provide further independent reference points to assess how reliable the model simulations are and what the main limitations are. The horizontal structure of mid-latitude pollution plumes agrees well between the IASI total column CO and the model simulations. However, finer-scale structures are too quickly diffused in the Eulerian model. Applying the IASI averaging kernels to the model data is essential for a meaningful comparison. Using aircraft data as a reference suggests that the satellite data are biased high, while TOMCAT is biased low. FLEXPART fits the aircraft data rather well, but due to added background concentrations the simulation is not independent from observations. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. In addition to the very good agreement between simulated and observed total column CO fields, the results also highlight the difficulty to identify a data set that most realistically represents the actual pollution state of the Arctic atmosphere. © 2011 Adis Data Information BV. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe