449 research outputs found
Exact Transformation for Spin-Charge Separation of Spin-half Fermions without Constraints
We demonstrate an exact local transformation which maps a purely Fermionic
manybody system to a system of spinfull Bosons and spinless Fermions,
demonstrating a possible path to a non-Fermi liquid state. We apply this to the
half-filled Hubbard model and show how the transformation maps the ordinary
spin half Fermionic degrees of freedom exactly and without introducing Hilbert
space constraints to a charge-like ``quasicharge'' fermion and a spin-like
``quasispin'' Boson while preserving all the symmetries of the model. We
present approximate solutions with localized charge which emerge naturally from
the Hubbard model in this form. Our results strongly suggest that charge tends
to remain localized for large values of the Hubbard U
Advection Dominated Accretion Flows Around Kerr Black Holes
We derive all relevant equations needed for constructing a global general
relativistic model of advectively cooled, very hot, optically thin accretion
disks around black holes and present solutions which describe advection
dominated flows in the gravitational field of a Kerr black hole.Comment: ApJ submitte
Different Disease Profiles for Women and Men with Abdominal Aortic Aneurysms
ObjectiveThe overall aim with this study was to investigate causes of death and mortality rates for women and men treated for abdominal aortic aneurysm (AAA) in Sweden.Materials and methodAll patients treated for ruptured and non-ruptured AAA 1987–2002 in Sweden were identified in national registries (n=12917). Age, sex, diagnosis, surgical procedure and mortality were analysed on a patient specific level. Logistic regression and analysis of standardised mortality rates (SMR) were performed.ResultsPost operative mortality was similar between the sexes. Age (p<0.0001), and surgery for rupture (p=0.0005), but not gender (p=0.65) were significant risk factor for poor long term survival. SMR revealed increased risk for both sexes compared to the population with significantly higher values for women than men (2.26, CI 2.10–2.43 vs. 1.63, CI 1.57–1.68, p<0.0001). The higher risk for women could be explained by the higher risk for aneurysm related death (ie.thoracic or abdominal aorta) compared to men (Hazard ratio 1.57 vs. 1.0, p<0.0001).ConclusionWomen do not have an increased surgical risk compared to men, but treated women have an increased risk of premature death compared to men and women in the population. They also have a higher risk for aneurysm related death compared to men with AAA
Recommended from our members
Homicide in Finland, the Netherlands and Sweden: a first study on the European Homicide Monitor Data
Anharmonic softening of Raman active phonons in Iron-Pnictides; estimating the Fe isotope effect due to anharmonic expansion
We present Raman measurements on the iron-pnictide superconductors
CeFeAsO_{1-x}F_{x} and NdFeAsO{1-x}F_{x}. Modeling the Fe-As plane in terms of
harmonic and a cubic anharmonic Fe-As interaction we calculate the temperature
dependence of the energy and lifetime of the Raman active Fe B_{1g} mode and
fit to the observed energy shift. The shifts and lifetimes are in good
agreement with those measured also in other Raman studies which demonstrate
that the phonon spectrum is well represented by phonon-phonon interactions
without any significant electronic contribution. We also estimate the
anharmonic expansion from Fe (56->54) isotope substitution to \Delta a=5.1
10^{-4}\AA and \Delta d_{Fe-As}= 2.510^{-4}\AA and the shift of harmonic zero
point fluctuations of bond lengths <=3 10^{-5}\AA^2, giving a total
relative average decrease of electronic hopping integrals of |\delta t|/t<= 2.0
10^{-4}. The results poses a serious challenge for any theory of
superconductivity in the pnictides that does not include electron-phonon
interactions to produce a sizable Fe-isotope effect.Comment: 7 pages, 6 figure
Distributional exact diagonalization formalism for quantum impurity models
We develop a method for calculating the self-energy of a quantum impurity
coupled to a continuous bath by stochastically generating a distribution of
finite Anderson models that are solved by exact diagonalization, using the
noninteracting local spectral function as a probability distribution for the
sampling. The method enables calculation of the full analytic self-energy and
single-particle Green's function in the complex frequency plane, without
analytic continuation, and can be used for both finite and zero temperature at
arbitrary fillings. Results are in good agreement with imaginary frequency data
from continuous-time quantum Monte Carlo calculations for the single impurity
Anderson model and the two-orbital Hubbard model within dynamical mean field
theory (DMFT) as well as real frequency data for self energy of the single band
Hubbard model within DMFT using numerical renormalization group. The method
should be applicable to a wide range of quantum impurity models and
particularly useful when high-precision real frequency results are sought.Comment: Two band calculation updated, 4 pages, 4 figure
Fermi momentum resolved charge order for spin disordered stripes
For a doped antiferromagnet with short-range spin stripe correlations and
long-range charge stripe order we find that the manifestation of charge order
changes abruptly as a function of momentum along the Fermi surface. The
disorder averaged local density of states is almost perfectly homogeneous when
integrated only over states which contribute to the ``nodal'' spectral weight
whereas it displays long range charge stripe order when integrated only over
states which contribute to the ``antinodal'' spectral weight. An effectively
two dimensional nodal liquid can thus coexist with static charge stripes
provided there is no static spin order. We also study commensurate spin and
charge stripe ordered systems where the Fermi surface consists of a nodal hole
pocket and an open ``stripe band'' section. Due to the stripe order the
relation between hole density and size of a pocket will be reduced compared to
a paramagnet by a factor of two for even charge period and four for odd charge
period and we find an estimated upper limit on the area fraction of a hole
pocket of 1.6% for charge period four and 4% for charge period five. We also
discuss why electron pockets are not expected for a stripe ordered system and
show that the open Fermi surface section may be electron like with a negative
Hall coefficient.Comment: 9 pages, 5 figures, added references and extended discussion of Hall
coefficient for stripe ordered system; v3 final, improved figure
Residential movements in connection to renovation of rented multi-residential housing: A pilot study
Residential movement and displacement as an effect of renovation has earned attention and also affected renovation practices in Sweden. While statistical studies have linked deep renovation to residential movement and displacement, there are no recent studies that investigate why people move or remain in housing areas that are renovated, and if and how the relocation is determined by the renovation. A pilot study was initiated as a means to develop a methodology to study residential movement in connection to renovation. In this paper, methodological considerations are discussed based on 31 interviews (face-to-face and telephone) with movers related to 34 municipally owned rented housing areas about to undergo renovation, as well results from a questionnaire sent to two finalised renovation projects (N=113). So far, the pilot study indicate that few relocations can be linked to the up-coming or finalised renovation in the studies cases. The questionnaire that was sent out to remaining tenants had a low response rate of 29%, and the efficiency of using questionnaires is discussed
Potential savings without compromising the quality of care
SUMMARY Aims: This study was designed to analyse the association between adherence to guidelines for rational drug use and surrogate outcome markers for hypertension, diabetes and hypercholesterolaemia. Methods: The study used a cross-sectional ecological design. Data from dispensed prescriptions and medical records were analysed from 24 primary healthcare centres with a combined registered population of 330,000 patients in 2006. Guideline adherence was determined calculating the proportion of the prescribed volume of antidiabetic agents, antihypertensives and lipid-lowering agents representing the 14 different drugs included in the guidelines for these three areas. Patient outcome was assessed using surrogate marker data on HbA1C, blood pressure (BP) and s-cholesterol. The association between the guidelines adherence and outcomes measures was analysed by logistic regression. Results: The proportion of guideline antidiabetic drugs in relation to all antidiabetic drugs prescribed varied between 80% and 97% among the practices, the ratio of angiotensin converting enzyme (ACE)-inhibitors to all renin–angiotensin drugs 40–77% and the ratio of simvastatin to all statins 58–90%. The proportion of patients reaching targets for HbA1C, BP and s-cholesterol varied between 34% and 66%, 36% and 57% and 46% and 71% respectively. No significant associations were found between adherence to the guidelines and outcome. The expenditures for antihypertensives and lipid-lowering drugs could potentially be reduced by 10% and 50% respectively if all practices adhered to the guidelines as the top performing practices. Conclusion: A substantial amount of money can be saved in primary care without compromising the quality of care by using recommended first-line drugs for the treatment diabetes, hypertension and hypercholesterolaemia. What's known • There are substantial price differences between branded and off-patent drugs for the treatment of diabetes, hypertension and hypercholesterolaemia. • There is a wide variation in adherence to prescribe targets in primary healthcare. • There is a limited knowledge on the relation between adherence to prescribing targets or guidelines, patient outcomes and potential savings that could be achieved. What's new • No significant associations were found at a practice level between adherence to the guidelines and outcomes in terms of patients reaching target levels for surrogate markers. • A substantial amount of money can be saved in primary care without compromising the quality of care by using recommended off-patent drugs for the treatment of diabetes, hypertension and hypercholesterolaemia
Kondo effect in crossed Luttinger liquids
We study the Kondo effect in two crossed Luttinger liquids, using Boundary
Conformal Field Theory. We predict two types of critical behaviors: either a
two-channel Kondo fixed point with a nonuniversal Wilson ratio, or a new theory
with an anomalous response identical to that found by Furusaki and Nagaosa (for
the Kondo effect in a single Luttinger liquid). Moreover, we discuss the
relevance of perturbations like channel anisotropy, and we make links with the
Kondo effect in a two-band Hubbard system modeled by a channel-dependent
Luttinger Hamiltonian. The suppression of backscattering off the impurity
produces a model similar to the four-channel Kondo theory.Comment: 7 pages, RevteX, to be published in Physical Review
- …