다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Statistical physics has proven to be a fruitful framework to describe phenomena outside the realm of traditional physics. Recent years have witnessed an attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. A wide list of topics are reviewed ranging from opinion and cultural and language dynamics to crowd behavior, hierarchy formation, human dynamics, and social spreading. The connections between these problems and other, more traditional, topics of statistical physics are highlighted. Comparison of model results with empirical data from social systems are also emphasized.

Statistical physics of social dynamics

We have studied the three quark system in a relativized version of the quark potential model with chromodynamics. With parameters consistent with those of an analogous study of meson spectroscopy we obtain a successful description of the spectrum of baryons. The model naturally explains the apparent absence of spin‐orbit interactions in baryons.

Baryons in a relativized quark model with chromodynamics

Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Monthly Notices of the Royal Astronomical Society

We reexamine the effects of antisymmetry on the antiquarks in the nucleon sea arising from gluon exchange and pion exchange between confined quarks. While the effect is primarily to suppress down relative to up antiquarks, this is numerically insignificant for the pion terms. {copyright} {ital 1997} {ital The American Physical Society}

/pdf/flavor-asymmetry-of-the-nucleon-sea-jw16yr37yy.pdf

Flavor asymmetry of the nucleon sea

Rather than regarding the restriction of current lattice QCD simulations to quark masses that are 5--10 times larger than those observed, we note that this presents a wonderful opportunity to deepen our understanding of QCD. Just as it has been possible to learn a great deal about QCD by treating N{sub c} as a variable, so the study of hadron properties as a function of quark mass is leading us to a much deeper appreciation of hadron structure. As examples we cite recent progress in using the chiral properties of QCD to connect hadron masses, magnetic moments, charge radii and structure functions calculated at large quark masses within lattice QCD with the values observed physically.

/pdf/a-new-slant-on-hadron-structure-49cwsginjg.pdf

A New Slant on Hadron Structure

Using the resonance model, which was successfully applied for the study of the $pp{\to}p{\Lambda}K^+$ reaction, we investigate $NN{\to}N{\Sigma}K$ reactions that should provide cleaner information about resonance excitations and meson exchange contributions. For this purpose we demonstrate that the invariant mass distribution for the ${\Sigma}K$ system, as well as the Dalitz plot for the $NN{\to}N{\Sigma}K$ reaction, provide direct information about the ${\Sigma}K$ production mechanism, which can be tested in the near future by experiments at COSY.

The role of the $P_{11}(1710)$ in the $NN{\to}N{\Sigma}K$ reaction

Starting from a simple nonrelativistic field theory of pions and nucleons, we derive linear integral equations coupling amplitudes of baryon number equal two systems. These equations guarantee two- and three-body unitarity above the threshold for single pion production, and include explicitly the coupling of the NN to (e.g.) N..delta.. and ..pi..d channels. The relationship of this approach to earlier schemes is discussed.

Nucleon-nucleon scattering above the pion production threshold

We investigate the muonic hydrogen 2P{sub 3/2}{sup F=2} to 2S{sub 1/2}{sup F=1} transition through a precise, nonperturbative numerical solution of the Dirac equation including the finite-size Coulomb force and finite-size vacuum polarization. The results are compared with earlier perturbative calculations of (primarily) [E. Borie, Phys. Rev. A 71, 032508 (2005); E. Borie and G. A. Rinker, Rev. Mod. Phys. 54, 67 (1982); E. Borie, Z. Phys. A 275, 347 (1975) and A. P. Martynenko, Phys. Rev. A 71, 022506 (2005); A. Martynenko, Phys. At. Nucl. 71, 125 (2008), and K. Pachucki, Phys. Rev. A 53, 2092 (1996)] and experimental results recently presented by Pohl et al.[Nature (London) 466, 213 (2010)], in which this very comparison is interpreted as requiring a modification of the proton charge radius from that obtained in electron scattering and electronic hydrogen analyses. We find no significant discrepancy between the perturbative and nonperturbative calculations, and we present our results as confirmation of the perturbative methods.

/pdf/nonperturbative-relativistic-calculation-of-the-muonic-4qjmvykt1z.pdf

Anthony W. Thomas

Papers

Flavor asymmetry of the nucleon sea

A New Slant on Hadron Structure

The role of the $P_{11}(1710)$ in the $NN{\to}N{\Sigma}K$ reaction

Nucleon-nucleon scattering above the pion production threshold

Nonperturbative relativistic calculation of the muonic hydrogen spectrum