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S Puccetti - One of the best experts on this subject based on the ideXlab platform.
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the xmm newton wide field survey in the cosmos field v angular clustering of the x ray point sources
Astrophysical Journal Supplement Series, 2007Co-Authors: Takamitsu Miyaji, G Zamorani, N Cappelluti, R Gilli, R E Griffiths, A Comastri, Guenther Hasinger, M Brusa, F Fiore, S PuccettiAbstract:We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the ~2 deg2 COSMOS field (COSMOS XMM-Newton). Significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5'-24', while the positive signals were at the ~2 and ~3 σ levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands, respectively. Correctly taking integral Constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral Constraint Term, we find correlation lengths of θc = 1.9'' ± 0.3'', 0.8'' , and 6'' ± 2'' for the SFT, MED, and UHD bands, respectively, for γ = 1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are rc ≈ 9.8 ± 0.7, 5.8, and 12 ± 2 h-1 Mpc at the effective redshifts of eff ≈ 1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands, respectively. If we include the integral Constraint Term in the fitting process, assuming that the power law extends to the scale length of the entire COSMOS XMM-Newton field, the correlation lengths become larger by ~20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs σ8,AGN with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range bAGN = 1.5-4.
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the xmm newton wide field survey in the cosmos field v angular clustering of the x ray point sources
arXiv: Astrophysics, 2006Co-Authors: Takamitsu Miyaji, G Zamorani, N Cappelluti, R Gilli, R E Griffiths, A Comastri, Guenther Hasinger, M Brusa, F Fiore, S PuccettiAbstract:We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the 2 deg2 COSMOS field (XMM-COSMOS). A significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5-24 arcminutes, while the positive signals were at the 2 and 3 sigma levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands respectively. Correctly taking integral Constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral Constraint Term, we find correlation lengths of theta_c=1.9+-0.3, 0.8+0.5-0.4 and 6+-2 arcseconds for the SFT, MED, and UHD bands respectively for gamma=1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are 9.8+-0.7, 5.8+1.4-1.7 and 12+-2 h-1 Mpc at the effective redshifts of 1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands respectively. If we include the integral Constraint Term in the fitting process,assuming that the power-law extends to the scale length of the entire XMM-COSMOSfield, the correlation lengths become larger by 20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range b(AGN)=1.5-4. (Edited to simple ascii.)
Hidetoshi Nishimori - One of the best experts on this subject based on the ideXlab platform.
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performance enhancement of quantum annealing under the lechner hauke zoller scheme by non linear driving of the Constraint Term
Journal of the Physical Society of Japan, 2020Co-Authors: Yuki Susa, Hidetoshi NishimoriAbstract:We analyze the performance of quantum annealing as formulated by Lechner, Hauke, and Zoller (LHZ), by which a Hamiltonian with all-to-all two-body interactions is reduced to a corresponding Hamilto...
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performance enhancement of quantum annealing under the lechner hauke zoller scheme by non linear driving of the Constraint Term
arXiv: Quantum Physics, 2019Co-Authors: Yuki Susa, Hidetoshi NishimoriAbstract:We analyze the performance of quantum annealing as formulated by Lechner, Hauke, and Zoller (LHZ), by which a Hamiltonian with all-to-all two-body interactions is reduced to a corresponding Hamiltonian with local many-body interactions. Mean-field analyses show that problematic first-order quantum phase transitions that exist in the original LHZ formulation can be avoided, and thus an exponential speedup is achieved, if we drive the coefficient of the many-body Term, which represents the Constraint, non-linearly as a function of time. This result applies not only to a simple ferromagnetic model but also to the spin glass problem if a parameter in the spin glass model is chosen appropriately.
B M W Tsui - One of the best experts on this subject based on the ideXlab platform.
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a new cardiac motion vector field estimation method based on the optical flow method with additional Constraint from motion of an anatomical feature in 4d cardiac pet
The Journal of Nuclear Medicine, 2016Co-Authors: Jizhe Wang, Tao Feng, B M W TsuiAbstract:148 Objectives The goal is to develop and evaluate a new cardiac motion vector field (MVF) estimation method based on the conventional optical-flow algorithm with an additional Constraint from the motion of an anatomical feature from 4D cardiac gated PET images to improve cardiac motion estimation accuracy. Methods Noisy cardiac-gated PET projection data were generated from the 4D XCAT phantom with realistic cardiac MVF model with 8 gated frames and reconstructed using the STIR package. A customized high-resolution PET scanner with a system resolution of 0.78 mm was used in the analytical simulation for accurate feature extraction and the iterative OS-EM algorithm was used in image reconstruction. The interventricular sulcus (IS) was extracted from 3D cardiac PET image at each gated frame, and the motion along its length was estimated and decomposed into the radial, circumferential, and longitudinal components. Similar to our previous implementation, a sulcus-based initial cardiac MVF estimate was extrapolated from the motion of extracted IS based on the a priori knowledge about the spatial variation of three cardiac motion components in myocardium. It was also used as an additional Constraint in the new optical-flow algorithm to enforce sulcus matching between two cardiac frames. The Constraint was assigned larger weight for voxels closer to the IS. The new motion estimation algorithm was combined with the S-initial, which was based on the extracted IS motion and cardiac motion model, for feature-based cardiac motion estimation. In comparison, the conventional optical flow algorithm was applied with initial estimates: 0-initial, where the initial cardiac MVF has zero values; T-initial, where the ‘true’ cardiac MVF of the 4D XCAT phantom was used; as well as the S-initial. The motion estimation results with four methods were compared to the true cardiac MVF of the 4D XCAT phantom for quantitative evaluation. Results In frames with significant cardiac motion, the cardiac MVF estimates using the conventional optical-flow algorithm and the S-initial were more accurate than that using the 0-initial, and were comparable to that using the T-initial. When the new motion estimation method with the additional Constraint Term and the S-initial were used, the accuracy of the cardiac MVF estimate is further improved, surpassing that of the conventional motion estimation method using the T-initial. Conclusions A cardiac MVF estimation method based on the conventional optical flow algorithm and an additional Constraint Term that incorporate the motion of the IS was developed and evaluated using analytically simulated 4D cardiac-gated MP PET data. The new motion estimation method provides improved estimate of the cardiac MVF, providing important additional diagnostic information from 4D MP PET studies.
Takamitsu Miyaji - One of the best experts on this subject based on the ideXlab platform.
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the xmm newton wide field survey in the cosmos field v angular clustering of the x ray point sources
Astrophysical Journal Supplement Series, 2007Co-Authors: Takamitsu Miyaji, G Zamorani, N Cappelluti, R Gilli, R E Griffiths, A Comastri, Guenther Hasinger, M Brusa, F Fiore, S PuccettiAbstract:We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the ~2 deg2 COSMOS field (COSMOS XMM-Newton). Significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5'-24', while the positive signals were at the ~2 and ~3 σ levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands, respectively. Correctly taking integral Constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral Constraint Term, we find correlation lengths of θc = 1.9'' ± 0.3'', 0.8'' , and 6'' ± 2'' for the SFT, MED, and UHD bands, respectively, for γ = 1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are rc ≈ 9.8 ± 0.7, 5.8, and 12 ± 2 h-1 Mpc at the effective redshifts of eff ≈ 1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands, respectively. If we include the integral Constraint Term in the fitting process, assuming that the power law extends to the scale length of the entire COSMOS XMM-Newton field, the correlation lengths become larger by ~20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs σ8,AGN with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range bAGN = 1.5-4.
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the xmm newton wide field survey in the cosmos field v angular clustering of the x ray point sources
arXiv: Astrophysics, 2006Co-Authors: Takamitsu Miyaji, G Zamorani, N Cappelluti, R Gilli, R E Griffiths, A Comastri, Guenther Hasinger, M Brusa, F Fiore, S PuccettiAbstract:We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the 2 deg2 COSMOS field (XMM-COSMOS). A significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5-24 arcminutes, while the positive signals were at the 2 and 3 sigma levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands respectively. Correctly taking integral Constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral Constraint Term, we find correlation lengths of theta_c=1.9+-0.3, 0.8+0.5-0.4 and 6+-2 arcseconds for the SFT, MED, and UHD bands respectively for gamma=1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are 9.8+-0.7, 5.8+1.4-1.7 and 12+-2 h-1 Mpc at the effective redshifts of 1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands respectively. If we include the integral Constraint Term in the fitting process,assuming that the power-law extends to the scale length of the entire XMM-COSMOSfield, the correlation lengths become larger by 20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range b(AGN)=1.5-4. (Edited to simple ascii.)
G Zamorani - One of the best experts on this subject based on the ideXlab platform.
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the xmm newton wide field survey in the cosmos field v angular clustering of the x ray point sources
Astrophysical Journal Supplement Series, 2007Co-Authors: Takamitsu Miyaji, G Zamorani, N Cappelluti, R Gilli, R E Griffiths, A Comastri, Guenther Hasinger, M Brusa, F Fiore, S PuccettiAbstract:We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the ~2 deg2 COSMOS field (COSMOS XMM-Newton). Significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5'-24', while the positive signals were at the ~2 and ~3 σ levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands, respectively. Correctly taking integral Constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral Constraint Term, we find correlation lengths of θc = 1.9'' ± 0.3'', 0.8'' , and 6'' ± 2'' for the SFT, MED, and UHD bands, respectively, for γ = 1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are rc ≈ 9.8 ± 0.7, 5.8, and 12 ± 2 h-1 Mpc at the effective redshifts of eff ≈ 1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands, respectively. If we include the integral Constraint Term in the fitting process, assuming that the power law extends to the scale length of the entire COSMOS XMM-Newton field, the correlation lengths become larger by ~20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs σ8,AGN with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range bAGN = 1.5-4.
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the xmm newton wide field survey in the cosmos field v angular clustering of the x ray point sources
arXiv: Astrophysics, 2006Co-Authors: Takamitsu Miyaji, G Zamorani, N Cappelluti, R Gilli, R E Griffiths, A Comastri, Guenther Hasinger, M Brusa, F Fiore, S PuccettiAbstract:We present the first results of the measurements of angular auto-correlation functions (ACFs) of X-ray point sources detected in the XMM-Newton observations of the 2 deg2 COSMOS field (XMM-COSMOS). A significant positive signals have been detected in the 0.5-2 (SFT) band, in the angle range of 0.5-24 arcminutes, while the positive signals were at the 2 and 3 sigma levels in the 2-4.5 (MED) and 4.5-10 (UHD) keV bands respectively. Correctly taking integral Constraints into account is a major limitation in interpreting our results. With power-law fits to the ACFs without the integral Constraint Term, we find correlation lengths of theta_c=1.9+-0.3, 0.8+0.5-0.4 and 6+-2 arcseconds for the SFT, MED, and UHD bands respectively for gamma=1.8. The inferred comoving correlation lengths, also taking into account the bias by the source merging due to XMM-Newton PSF, are 9.8+-0.7, 5.8+1.4-1.7 and 12+-2 h-1 Mpc at the effective redshifts of 1.1, 0.9, and 0.6 for the SFT, MED, and UHD bands respectively. If we include the integral Constraint Term in the fitting process,assuming that the power-law extends to the scale length of the entire XMM-COSMOSfield, the correlation lengths become larger by 20%-90%. Comparing the inferred rms fluctuations of the spatial distribution of AGNs with those of the underlying mass, the bias parameters of the X-ray source clustering at these effective redshifts are in the range b(AGN)=1.5-4. (Edited to simple ascii.)