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

QCD interactions for equal-mass fermion ﬂavours are ﬂavour blind. This fact is often used to state that sea-quark loop contributions are equal for u and d quarks in the mass symmetric case and therefore these disconnected sea-quark loop contributions cannot contribute to the well-known ¯ d − ¯ u asymmetry in the proton. Instead, it is argued that one must look to the connected sector of lattice QCD correlation functions to ﬁnd this di ﬀ erence. In this presentation, we note that these statements are true only when one includes unphysical contributions in the sea-quark-loop sector, contributions from baryons that do not appear in the physical spectrum. Because these unphysical contributions must be eliminated from the sea-quark loop sector via the connected sector, the assertion that the ¯ d and ¯ u sea-quark loop contributions cancel in ¯ d − ¯ u is incorrect. Upon considering only physically observed baryons in the loop contributions, we illustrate an important contribution from the sea-quark loop sector to ¯ d − ¯ u .

Sea-quark loop contributions to the $\bar d$-$\bar u$ asymmetry in the proton

We determine the quark distributions and structure functions for both unpolarized and polarized DIS of leptons on nucleons and nuclei. The scalar and vector mean fields in the nucleus modify the motion of the quarks inside the nucleons. By taking into account this medium modification, we are able to reproduce the experimental data on the unpolarized EMC effect, and to make predictions for the polarized EMC effect. We discuss examples of nuclei where the polarized EMC effect could be measured. We finally present an extension of our model to describe fragmentation functions.

Polarized structure functions of nucleons and nuclei

Publisher Summary The Faddeev equations have had considerable success in describing three-body scattering data using simple two-body interactions. This chapter discusses low energy pion deuteron production in a three-body model. A bootstrap model of the nucleon was first used with the Faddeev equations in a successful discussion of pion–nucleon scattering. The idea was to treat the nucleon as a pion nucleon bound state. Apart from having a unitary model for the production process, π–d elastic scattering and the most peripheral aspects of nucleon–nucleon scattering can also be treated. The chapter also discusses two main reasons for investigating reaction. First, there is much interest in pions as probes for nuclear structure information via such reactions as (π,2Ν). The complicated nature of these calculations means that the actual absorption process can be treated only to second order in pion re-scattering. Secondly, there is a chance that pions may be useful probes of the free two-nucleon force, particularly off-shell effects.

Faddeev approach to pion production

The mass and decay width of the $\phi$ meson in cold nuclear matter are computed in an effective Lagrangian approach, with the medium dependence of these properties obtained by evaluating kaon-antikaon loop contributions to the $\phi$ self-energy. At normal nuclear matter density, we find a downward shift of the $\phi$ mass by a few percent, while the decay width is enhanced by an order of magnitude. We also present $\phi$--nucleus bound state energies and absorption widths for some selected nuclei, using complex optical potentials obtained in the local density approximation. Our results suggest that the $\phi$ should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.

$\phi$ meson in nuclear matter and nuclei

Using the quark-meson coupling (QMC) model, we study the density dependence of the quark and gluon condensates in nuclear matter. We show that the change of the quark condensate is mainly driven by the scalar field in the medium and that the reduction of the quark condensate is suppressed at high density, even in the mean-field approximation. The gluon condensate decreases by 4 - 6 % at nuclear saturation density. We also give a simple relationship between the change of the quark condensate and that of a hadron mass in the medium.

Anthony W. Thomas

Papers

Sea-quark loop contributions to the $\bar d$-$\bar u$ asymmetry in the proton

Polarized structure functions of nucleons and nuclei

Faddeev approach to pion production

$\phi$ meson in nuclear matter and nuclei

Quark and gluon condensates in the quark-meson coupling model