scholarly journals Boson Expansion Method and the Coupling of Different Degrees of Freedom

1974 ◽  
Vol 52 (3) ◽  
pp. 903-927 ◽  
Author(s):  
V. Ceausescu ◽  
A. A. Raduta
Keyword(s):  
Degrees Of Freedom ◽  
Expansion Method ◽  
Boson Expansion

scholarly journals Complex Langevin calculations in QCD at finite density

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Yuta Ito ◽  
Hideo Matsufuru ◽  
Yusuke Namekawa ◽  
Jun Nishimura ◽  
Shinji Shimasaki ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Chemical Potential ◽  
Expansion Method ◽  
Finite Density ◽  
Fermi Sphere ◽  
Expectation Value ◽  
Sign Problem ◽  
Zero Momentum ◽  
Effective Theories ◽  
Severe Sign

Abstract We demonstrate that the complex Langevin method (CLM) enables calculations in QCD at finite density in a parameter regime in which conventional methods, such as the density of states method and the Taylor expansion method, are not applicable due to the severe sign problem. Here we use the plaquette gauge action with β = 5.7 and four-flavor staggered fermions with degenerate quark mass ma = 0.01 and nonzero quark chemical potential μ. We confirm that a sufficient condition for correct convergence is satisfied for μ/T = 5.2 − 7.2 on a 83 × 16 lattice and μ/T = 1.6 − 9.6 on a 163 × 32 lattice. In particular, the expectation value of the quark number is found to have a plateau with respect to μ with the height of 24 for both lattices. This plateau can be understood from the Fermi distribution of quarks, and its height coincides with the degrees of freedom of a single quark with zero momentum, which is 3 (color) × 4 (flavor) × 2 (spin) = 24. Our results may be viewed as the first step towards the formation of the Fermi sphere, which plays a crucial role in color superconductivity conjectured from effective theories.

scholarly journals Hybrid Numerical-Experimental Model Update Based on Correlation Approach for Turbine Components

2020 ◽  
Author(s):  
Zeeshan Saeed ◽  
Christian Maria Firrone ◽  
Teresa Maria Berruti
Keyword(s):  
Degrees Of Freedom ◽  
Expansion Method ◽  
Hybrid Models ◽  
Impact Testing ◽  
Equivalent Model ◽  
Correlated Channels ◽  
Model Update ◽  
Model Mixing ◽  
Fatigue Failures

Abstract Bladed-disks in turbo-machines experience high cycle fatigue failures due to high vibration amplitudes. Therefore, it is important to accurately predict their dynamic characteristics including the mechanical joints at blade-disk (root joint) or blade-blade (shroud) interfaces. These joints help in dampening the vibration amplitudes. Before the experimental identification of these joints, it is of paramount importance to accurately measure the interface degrees-of-freedom (DoF). However, they are largely inaccessible for the measurements. For this reason, expansion techniques are used in order to update the single components before their coupling. But the expansion can be affected adversely if the measurements are not properly correlated with the updated model or if they have significant errors. Therefore, a frequency domain expansion method called System Equivalent Model Mixing (SEMM) is used to expand a limited set of measurements to a larger set of numerical DoF. Different measured models — termed the overlay models — are taken from an impact testing campaign of a blade and a disk and coupled to the numerical model according to the SEMM. The expanded models — termed the hybrid models — are then correlated with the validation channels in a round-robin way by means of Frequency Response Assurance Criteria (FRAC). The global correlations depict whether or not a measurement and the respective expansion is properly correlated. By this approach, the least correlated channels can be done away with from the measurements to have a better updated hybrid model. The method is tested on both the structures (the blade and the disk) and it is successfully shown that removing the uncorrelated channels does improve the quality of the hybrid models.

Slow Light Effect of Photonic Crystal Waveguides by Adjusting Parameters of Crescent Scatterers

2014 ◽  
Vol 926-930 ◽  
pp. 415-418
Author(s):  
Yong Wan ◽  
Yue Guo ◽  
Jing Gao ◽  
Ming Hui Jia
Keyword(s):  
Photonic Crystal ◽  
Degrees Of Freedom ◽  
Slow Light ◽  
Expansion Method ◽  
Photonic Crystal Waveguides ◽  
Light Effect ◽  
Plane Wave Expansion Method ◽  
Multiple Degrees Of Freedom ◽  
Low Dispersion ◽  
Center Distance

Crescent scatterers possess the properties of anisotropy and multiple degrees of freedom. With plane-wave expansion method (PWE), the slow light effect with high ngand low dispersion can be achieved by optimizing the structure parameters of photonic crystal waveguide with line defect, such as changing the radius of two circles and center distance. Slow light with low dispersion can be obtained by these methods, which implies that choosing suitable scatterers and adjusting their parameters can efficiently achieve slow light with high ng and low dispersion.

Application of the boson-expansion method to even Se and Ru isotopes

1975 ◽  
Vol 12 (3) ◽  
pp. 1035-1053 ◽  
Author(s):  
S. G. Lie ◽  
G. Holzwarth
Keyword(s):  
Expansion Method ◽  
Boson Expansion

Application of the Dyson boson expansion method to the treatment of the pairing force

2001 ◽  
Vol 11 (3) ◽  
pp. 263-270 ◽  
Author(s):  
O. Civitarese ◽  
F. Montani ◽  
M. Reboiro
Keyword(s):  
Expansion Method ◽  
Pairing Force ◽  
Boson Expansion

scholarly journals On a Boson Expansion Method with Two-Body Correlations

1992 ◽  
Vol 88 (1) ◽  
pp. 35-52
Author(s):  
T. Kishimoto ◽  
T. Kammuri ◽  
H. Sakamoto
Keyword(s):  
Expansion Method ◽  
Boson Expansion

Boson-Expansion Method and the Collective Negative-Parity States in Even-Even Spherical Nuclei

1973 ◽  
Vol 8 (4) ◽  
pp. 1525-1538 ◽  
Author(s):  
A. A. Rådutå ◽  
V. Ceausescu ◽  
G. Stratan ◽  
A. Såndulescu
Keyword(s):  
Expansion Method ◽  
Negative Parity ◽  
Boson Expansion ◽  
Spherical Nuclei

Hybrid Numerical-Experimental Model Update Based on Correlation Approach for Turbine Components

2021 ◽  
Author(s):  
Zeeshan Saeed ◽  
Christian M. Firrone ◽  
Teresa Berruti
Keyword(s):  
Degrees Of Freedom ◽  
Expansion Method ◽  
Hybrid Models ◽  
Impact Testing ◽  
Equivalent Model ◽  
Correlated Channels ◽  
Model Update ◽  
Model Mixing ◽  
Fatigue Failures

Abstract Bladed-disks in turbo-machines experience high cycle fatigue failures due to high vibration amplitudes. Therefore, it is important to accurately predict their dynamic characteristics including the mechanical joints at blade-disk interfaces. Before the experimental identification of these joints, it is of paramount importance to accurately measure the interface degrees-of-freedom (DoF). However, they are largely inaccessible for the measurements. For this reason, expansion techniques can be used in order to update the single components. But the expansion can be affected adversely if the measurements are not properly correlated with the updated model. Therefore, a frequency domain expansion method called System Equivalent Model Mixing (SEMM) is used to expand a limited set of measurements to a larger set of numerical DoF. Different measured models - termed the overlay models - are taken from an impact testing campaign of a blade and a disk and coupled to the numerical model according to the SEMM. The expanded models - termed the hybrid models - are then correlated with the validation channels in a round-robin way by means of Frequency Response Assurance Criteria (FRAC). The global correlations depict whether or not a measurement and the respective expansion is properly correlated. By this approach, the least correlated channels can be done away with from the measurements to have a better updated hybrid model. The method is tested on both the structures (the blade and the disk) and it is successfully shown that removing the uncorrelated channels does improve the quality of the hybrid models.

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