2,078 research outputs found
Precise numerical results for limit cycles in the quantum three-body problem
The study of the three-body problem with short-range attractive two-body
forces has a rich history going back to the 1930's. Recent applications of
effective field theory methods to atomic and nuclear physics have produced a
much improved understanding of this problem, and we elucidate some of the
issues using renormalization group ideas applied to precise nonperturbative
calculations. These calculations provide 11-12 digits of precision for the
binding energies in the infinite cutoff limit. The method starts with this
limit as an approximation to an effective theory and allows cutoff dependence
to be systematically computed as an expansion in powers of inverse cutoffs and
logarithms of the cutoff. Renormalization of three-body bound states requires a
short range three-body interaction, with a coupling that is governed by a
precisely mapped limit cycle of the renormalization group. Additional
three-body irrelevant interactions must be determined to control subleading
dependence on the cutoff and this control is essential for an effective field
theory since the continuum limit is not likely to match physical systems ({\it
e.g.}, few-nucleon bound and scattering states at low energy). Leading order
calculations precise to 11-12 digits allow clear identification of subleading
corrections, but these corrections have not been computed.Comment: 37 pages, 8 figures, LaTeX, uses graphic
Few-Body Effects in Cold Atoms and Limit Cycles
Physical systems with a large scattering length have universal properties
independent of the details of the interaction at short distances. Such systems
can be realized in experiments with cold atoms close to a Feshbach resonance.
They also occur in many other areas of physics such as nuclear and particle
physics. The universal properties include a geometric spectrum of three-body
bound states (so-called Efimov states) and log-periodic dependence of
low-energy observables on the physical parameters of the system. This behavior
is characteristic of a renormalization group limit cycle. We discuss
universality in the three- and four-body sectors and give an overview of
applications in cold atoms.Comment: 7 pages, 3 figures, plenary talk at the 18th International IUPAP
Conference on Few-Body Problems in Physics (FB18), Santos, Brazil, August
200
Efimov physics in a finite volume
Three bosons with large scattering length show universal properties that do
not depend on the details of the interaction at short distances. In the
three-boson system, these properties include a geometric spectrum of shallow
three-body states called "Efimov states" and log-periodic dependence of
scattering observables on the scattering length. We investigate the
modification of the Efimov states in a finite cubic box and calculate the
dependence of their energies on the box size using effective field theory. We
explicitly verify the renormalization of the effective field theory in the
finite volume.Comment: 9 pages, 3 figures, sign error corrected, numerical results changed,
final versio
IMAGES I. Strong evolution of galaxy kinematics since z=1
(abbreviated) We present the first results of the ESO large program,
``IMAGES'' which aims at obtaining robust measurements of the kinematics of
distant galaxies using the multi-IFU mode of GIRAFFE on the VLT. 3D
spectroscopy is essential to robustly measure the often distorted kinematics of
distant galaxies (e.g., Flores et al. 2006). We derive the velocity fields and
-maps of 36 galaxies at 0.4<z<0.75 from the kinematics of the [OII]
emission line doublet, and generate a robust technique to identify the nature
of the velocity fields based on the pixels of the highest signal-to-noise
ratios (S/N). We have gathered a unique sample of 63 velocity fields of
emission line galaxies (W0([OII]) > 15 A) at z=0.4-0.75, which are a
representative subsample of the population of M_stellar>1.5x10^{10} M_sun
emission line galaxies in this redshift range, and are largely unaffected by
cosmic variance. Taking into account all galaxies -with or without emission
lines- in that redshift range, we find that at least 41+/-7% of them have
anomalous kinematics, i.e., they are not dynamically relaxed. This includes
26+/-7% of distant galaxies with complex kinematics, i.e., they are not simply
pressure or rotationally supported. Our result implies that galaxy kinematics
are among the most rapidly evolving properties, because locally, only a few
percent of the galaxies in this mass range have complex kinematics.Comment: 17 pages, 6 figures, Accepted by A&
Nonuniversal Effects in the Homogeneous Bose Gas
Effective field theory predicts that the leading nonuniversal effects in the
homogeneous Bose gas arise from the effective range for S-wave scattering and
from an effective three-body contact interaction. We calculate the leading
nonuniversal contributions to the energy density and condensate fraction and
compare the predictions with results from diffusion Monte Carlo calculations by
Giorgini, Boronat, and Casulleras. We give a crude determination of the
strength of the three-body contact interaction for various model potentials.
Accurate determinations could be obtained from diffusion Monte Carlo
calculations of the energy density with higher statistics.Comment: 24 pages, RevTex, 5 ps figures, included with epsf.te
The elementary excitations of the exactly solvable Russian doll BCS model of superconductivity
The recently proposed Russian doll BCS model provides a simple example of a
many body system whose renormalization group analysis reveals the existence of
limit cycles in the running coupling constants of the model. The model was
first studied using RG, mean field and numerical methods showing the Russian
doll scaling of the spectrum, E(n) ~ E0 exp(-l n}, where l is the RG period. In
this paper we use the recently discovered exact solution of this model to study
the low energy spectrum. We find that, in addition to the standard
quasiparticles, the electrons can bind into Cooper pairs that are different
from those forming the condensate and with higher energy. These excited Cooper
pairs can be described by a quantum number Q which appears in the Bethe ansatz
equation and has a RG interpretation.Comment: 36 pages, 12 figure
More on the infrared renormalization group limit cycle in QCD
We present a detailed study of the recently conjectured infrared
renormalization group limit cycle in QCD using chiral effective field theory.
It was conjectured that small increases in the up and down quark masses can
move QCD to the critical trajectory for an infrared limit cycle in the
three-nucleon system. At the critical quark masses, the binding energies of the
deuteron and its spin-singlet partner are tuned to zero and the triton has
infinitely many excited states with an accumulation point at the three-nucleon
threshold. We exemplify three parameter sets where this effect occurs at
next-to-leading order in the chiral counting. For one of them, we study the
structure of the three-nucleon system in detail using both chiral and contact
effective field theories. Furthermore, we investigate the matching of the
chiral and contact theories in the critical region and calculate the influence
of the limit cycle on three-nucleon scattering observables.Comment: 17 pages, 7 figures, discussion improved, results unchanged, version
to appear in EPJ
Vitamin D deficiency is associated with IL-6 levels and monocyte activation in HIV-infected persons
Immune activation plays a key role in HIV pathogenesis. Markers of inflammation have been associated with vitamin D deficiency in the general population. Studies have also demonstrated associations of vitamin D deficiency with increased risk of HIV progression and death. The relationship between persistent inflammation and immune activation during chronic HIV infection and vitamin D deficiency remains unclear.Cryopreserved specimens were analyzed from 663 participants at the time of enrollment from the Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy (SUN Study) from 2004 to 2006. Biomarkers of inflammation, atherosclerosis, and coagulation were measured using enzyme-linked immunosorbent assays (ELISAs) and electrochemiluminescence. 25(OH)D, the stable precursor form of vitamin D, was measured using a radioimmunoassay with levels defined as: normal (≥30ng/mL), insufficient (20-29 ng/mL) and deficient (<20 ng/mL). Monocyte phenotypes were assessed by flow cytometry. Linear and logistic regression models were used to determine statistical associations between biomarkers and vitamin D deficiency.25(OH)D levels were deficient in 251 (38%) participants, insufficient in 222 (34%), and normal in 190 (29%). Patients with vitamin D deficiency, when compared to those with insufficient or normal vitamin D levels, had increased levels of IL-6 (23%; p<0.01), TNF-α (21%, p = 0.03), D-dimer (24%, p = 0.01), higher proportions of CD14dimCD16+ (22%, p<0.01) and CX3CR1+ monocytes (48%; p<0.001) and decreased frequency of CCR2+ monocytes (-3.4%, p<0.001). In fully adjusted models, vitamin D associations with abnormal biomarker levels persisted for IL-6 levels and CX3CR1+ and CCR2+ phenotypes.Vitamin D deficiency is associated with greater inflammation and activated monocyte phenotypes. The role of vitamin D deficiency in persistent immune activation and associated complications during chronic HIV disease should be further evaluated as a possible target for intervention
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