7,427 research outputs found
Asymptotic safety in the sine-Gordon model
In the framework of the functional renormalization group method it is shown
that the phase structure of the 2-dimensional sine-Gordon model possesses a
nontrivial UV fixed point which makes the model asymptotically safe. The fixed
point exhibits strong singularity similarly to the scaling found in the
vicinity of the infrared fixed point. The singularity signals the upper
energy-scale limit to the validity of the model. We argue that the sine-Gordon
model with a momentum-dependent wavefunction renormalization is in a dual
connection with the massive sine-Gordon model.Comment: 8 pages, 3 figure
Optimized regulator for the quantized anharmonic oscillator
The energy gap between the first excited state and the ground state is
calculated for the quantized anharmonic oscillator in the framework of the
functional renormalization group method. The compactly supported smooth
regulator is used which includes various types of regulators as limiting cases.
It was found that the value of the energy gap depends on the regulator
parameters. We argue that the optimization based on the disappearance of the
false, broken symmetric phase of the model leads to the Litim's regulator. The
least sensitivity on the regulator parameters leads however to an IR regulator
being somewhat different of the Litim's one, but it can be described as a
perturbatively improved, or generalized Litim's regulator and provides analytic
evolution equations, too.Comment: 8 pages, 4 figure
Quantum-classical transition in the Caldeira-Leggett model
The quantum-classical transition in the Caldeira-Leggett model is
investigated in the framework of the functional renormalization group method.
It is shown that a divergent quadratic term arises in the action due to the
heat bath in the model. By removing the divergence with a frequency cutoff we
considered the critical behavior of the model. The critical exponents belonging
to the susceptibility and the correlation length are determined and their
independence of the frequency cutoff and the renormalization scheme is shown.Comment: 8 pages, 4 figure
COMPARATIVE ANALYSIS OF THE CHANGES OF THE MASS MOMENTS OF INERTIA DURING A BREAST-STROKE
A new method of investigation of athletes' motion takes into consideration the changes of the principal moments of inertia and their directions during the interval of the motion, because these characterise the efficiency and the neuro-muscular regulation of the motion. This paper presents a comparative analysis of two top swimmers (Swl=Rozsa, Sw2=Guttler) and points out the significant difference caused by their alternate motion pattern
Interplay of fixed points in scalar models
We performed the renormalization group analysis of scalar models exhibiting
spontaneous symmetry breaking. It is shown that an infrared fixed point appears
in the broken symmetric phase of the models, which induces a dynamical scale,
that can be identified with the correlation length. This enables one to
identify the type of the phase transition which shows similarity to the one
appearing in the crossover scale. The critical exponent of the
correlation length also proved to be equal in the crossover and the infrared
scaling regimes.Comment: 11 pages, 4 figure
Fluctuations and the QCD phase diagram
In this contribution the role of quantum fluctuations for the QCD phase
diagram is discussed. This concerns in particular the importance of the matter
back-reaction to the gluonic sector. The impact of these fluctuations on the
location of the confinement/deconfinement and the chiral transition lines as
well as their interrelation are investigated. Consequences of our findings for
the size of a possible quarkyonic phase and location of a critical endpoint in
the phase diagram are drawn.Comment: 7 pages, 3 figures, to appear in Physics of Atomic Nucle
Clinical impact of double protease inhibitor boosting with Lopinavir/Ritonavir and Amprenavir as part of salvage antiretroviral therapy
Purpose: Double protease inhibitor (PI) boosting is being explored as a new strategy in salvage antiretroviral (ARV) therapy. However, if a negative drug interaction leads to decreased drug levels of either or both PIs, double PI boosting could lead to decreased virologic response. A negative drug interaction has been described between amprenavir (APV) and lopinavir/ritonavir (LPV/r). This observational cohort study assessed the virologic impact of the addition of APV to a salvage ARV regimen, which also contains LPV/r, compared to a regimen containing LPV/r alone. Method: Patients initiated on a salvage ARV regimen that included LPV/r obtained from the expanded access program in Toronto, Canada, were evaluated. APV (600-1,200 mg bid) was added at the discretion of the treating physician. Results: Using multivariate Cox proportional hazards models, we found that the addition of APV to a LPV/r-containing salvage regimen was not significantly associated with time to virologic suppression (< 50 copies/mL; adjusted hazard ratio [HR] = 0.75, p = .12) or with time to virologic rebound (adjusted HR = 1.46, p = .34). Those patients who received higher doses of APV had an increased chance of virologic suppression (p = .03). In a subset of 27 patients, the median LPV Ctrough was significantly lower in patients receiving APV (p = .04), and the median APV Ctrough was reduced compared to reported controls. Conclusion: Our data do not support an additional benefit in virologic reduction of double boosting with APV and LPV/r relative to LPV/r alone in salvage ARV therapy. Our study's limitations include its retrospective nature and the imbalance between the two groups potentially confounding the results. Although these factors were adjusted for in the multivariate analysis, a prospective randomized controlled trial is warranted to confirm our findings
The MACHO Project LMC Variable Star Inventory. IX. Frequency Analysis of the First Overtone RR Lyrae Stars and the Indication for Nonradial Pulsations
More than 1300 variables classified provisionally as first overtone RR Lyrae
pulsators in the MACHO variable star database of the Large Magellanic Cloud
(LMC) have been subjected to standard frequency analysis. Based on the remnant
power in the prewhitened spectra, we found 70% of the total population to be
monoperiodic. The remaining 30% (411 stars) are classified as one of 9 types
according to their frequency spectra. Several types of RR Lyrae pulsational
behavior are clearly identified here for the first time. Together with the
earlier discovered double-mode (fundamental & first overtone) variables this
study increased the number of the known double-mode stars in the LMC to 181.
During the total 6.5yr time span of the data, 10% of the stars show strong
period changes. We also discovered two additional types of multifrequency
pulsators with low occurrence rates of 2% for each. In the first type there
remains one closely spaced component after prewhitening by the main pulsation
frequency. In the second type the number of remnant components is two, they are
also closely spaced, and, in addition, they are symmetric in their frequency
spacing relative to the central component. This latter type of variables is
associated with their relatives among the fundamental pulsators, known as
Blazhko variables. Their high frequency (~20%) among the fundamental mode
variables versus the low occurrence rate of their first overtone counterparts
makes it more difficult to explain Blazhko phenomenon by any theory depending
mainly on the role of aspect angle or magnetic field. Current theoretical
models invoke nonradial pulsation components in these stars.Comment: 20 pages, 21 figures (bitmapped), 7 tables, to appear in Ap.
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