2,121 research outputs found
Inflaton Decay in an Alpha Vacuum
We study the alpha vacua of de Sitter space by considering the decay rate of
the inflaton field coupled to a scalar field placed in an alpha vacuum. We find
an {\em alpha dependent} Bose enhancement relative to the Bunch-Davies vacuum
and, surprisingly, no non-renormalizable divergences. We also consider a
modified alpha dependent time ordering prescription for the Feynman propagator
and show that it leads to an alpha independent result. This result suggests
that it may be possible to calculate in any alpha vacuum if we employ the
appropriate causality preserving prescription.Comment: 16 pages, 1 figure, Revtex 4 preprin
Lagrangian subcategories and braided tensor equivalences of twisted quantum doubles of finite groups
We classify Lagrangian subcategories of the representation category of a
twisted quantum double of a finite group. In view of results of 0704.0195v2
this gives a complete description of all braided tensor equivalent pairs of
twisted quantum doubles of finite groups. We also establish a canonical
bijection between Lagrangian subcategories of the representation category of a
twisted quantum double of a finite group G and module categories over the
category of twisted G-graded vector spaces such that the dual tensor category
is pointed. This can be viewed as a quantum version of V. Drinfeld's
characterization of homogeneous spaces of a Poisson-Lie group in terms of
Lagrangian subalgebras of the double of its Lie bialgebra. As a consequence, we
obtain that two group-theoretical fusion categories are weakly Morita
equivalent if and only if their centers are equivalent as braided tensor
categories.Comment: 26 pages; several comments and references adde
Affine equation of state from quintessence and k-essence fields
We explore the possibility that a scalar field with appropriate Lagrangian
can mimic a perfect fluid with an affine barotropic equation of state. The
latter can be thought of as a generic cosmological dark component evolving as
an effective cosmological constant plus a generalized dark matter. As such, it
can be used as a simple, phenomenological model for either dark energy or
unified dark matter. Furthermore, it can approximate (up to first order in the
energy density) any barotropic dark fluid with arbitrary equation of state. We
find that two kinds of Lagrangian for the scalar field can reproduce the
desired behaviour: a quintessence-like with a hyperbolic potential, or a purely
kinetic k-essence one. We discuss the behaviour of these two classes of models
from the point of view of the cosmological background, and we give some hints
on their possible clustering properties.Comment: 9 pages, 6 figures. Minor updates, accepted by CQ
Small Quadrupole Deformation for the Dipole Bands in 112In
High spin states in In were investigated using Mo(O,
p3n) reaction at 80 MeV. The excited level have been observed up to 5.6 MeV
excitation energy and spin 20 with the level scheme showing three
dipole bands. The polarization and lifetime measurements were carried out for
the dipole bands. Tilted axis cranking model calculations were performed for
different quasi-particle configurations of this doubly odd nucleus. Comparison
of the calculations of the model with the B(M1) transition strengths of the
positive and negative parity bands firmly established their configurations.Comment: 10 pages, 11 figures, 2 table
Numerical computation of electric field and potential along silicone rubber insulators under contaminated and dry band conditions
A Lower Limit on the Mass of Our Galaxy from the H3 Survey
The timing argument provides a lower limit on the mass of the Milky Way. We
find, using a sample of 32 stars at kpc drawn from the H3
Spectroscopic Survey and mock catalogs created from published numerical
simulations, that M M with 90% confidence.
We recommend using this limit to refine the allowed prior mass range in more
complex and sophisticated statistical treatments of Milky Way dynamics. The use
of such a prior would have significantly reduced many previously published
uncertainty ranges. Our analysis suggests that the most likely value of
M is M, but establishing this as the
Milky Way mass requires a larger sample of outer halo stars and a more complete
analysis of the inner halo stars in H3. The imminent growth in the sample of
outer halo stars due to ongoing and planned surveys will make this possible.Comment: 8 pages, submitted for publicatio
Does the revised cardiac risk index predict cardiac complications following elective lung resection?
Background:
Revised Cardiac Risk Index (RCRI) score and Thoracic Revised Cardiac Risk Index (ThRCRI) score were developed to predict the risks of postoperative major cardiac complications in generic surgical population and thoracic surgery respectively. This study aims to determine the accuracy of these scores in predicting the risk of developing cardiac complications including atrial arrhythmias after lung resection surgery in adults.
Methods:
We studied 703 patients undergoing lung resection surgery in a tertiary thoracic surgery centre. Observed outcome measures of postoperative cardiac morbidity and mortality were compared against those predicted by risk.
Results:
Postoperative major cardiac complications and supraventricular arrhythmias occurred in 4.8% of patients. Both index scores had poor discriminative ability for predicting postoperative cardiac complications with an area under receiver operating characteristic (ROC) curve of 0.59 (95% CI 0.51-0.67) for the RCRI score and 0.57 (95% CI 0.49-0.66) for the ThRCRI score.
Conclusions:
In our cohort, RCRI and ThRCRI scores failed to accurately predict the risk of cardiac complications in patients undergoing elective resection of lung cancer. The British Thoracic Society (BTS) recommendation to seek a cardiology referral for all asymptomatic pre-operative lung resection patients with > 3 RCRI risk factors is thus unlikely to be of clinical benefit
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