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 consider the capture of dark matter (DM) in neutron stars via scattering on hadronic targets, including neutrons, protons and hyperons. We extend previous analyses by including momentum dependent form factors, which account for hadronic structure, and incorporating the effect of baryon strong interactions in the dense neutron star interior, rather than modelling the baryons as a free Fermi gas. The combination of these effects suppresses the DM capture rate over a wide mass range, thus increasing the cross section for which the capture rate saturates the geometric limit. In addition, variation in the capture rate associated with the choice of neutron star equation of state is reduced. For proton targets, the use of the interacting baryon approach to obtain the correct Fermi energy is essential for an accurate evaluation of the capture rate in the Pauli-blocked regime. For heavy neutron stars, which are expected to contain exotic matter, we identify cases where DM scattering on hyperons contributes significantly to the total capture rate. Despite smaller neutron star capture rates, compared to existing analyses, we find that the projected DM-nucleon scattering sensitivity greatly exceeds that of nuclear recoil experiments for a wide DM mass range.

Improved Treatment of Dark Matter Capture in Neutron Stars III: Nucleon and Exotic Targets

We find that available data on $J/\Psi$ photoproduction at $|t|{\ge}$1 GeV are energy independent over the range $22{\le}\sqrt{s}{\le}170$ GeV and show a very soft $t$ dependence. Through a systematic analysis of the data we detect a new trajectory, which manifests itself at threshold and is energy independent. The trajectory couples to the axial form factor of the nucleon and can reproduce the $J/\Psi$ exclusive photoproduction data at large -$t$.

Indication of anomalous exchange in exclusive charmonium photoproduction

We present an elementary introduction to some of the quark models used to understand the properties of light mesons and baryons. These lectures are intended for both theoretical and experimental graduate students beginning their study of the strong interaction.

Classical Quark Models: An Introduction

We review the reasons why one might choose to seriously re-examine the traditional approach to nuclear theory where nucleons are treated as immutable. This examination leads us to argue that the modification of the structure of the nucleon when immersed in a nuclear medium is fundamental to how atomic nuclei are built. Consistent with this approach we suggest key experiments which should tell us unambiguously whether there is such a change in the structure of a bound nucleon. We also briefly report on extremely promising recent calculations of the structure of nuclei across the periodic table based upon this idea.

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QCD and a New Paradigm for Nuclear Structure

Although a great many innovative and exciting suggestions were made for physics investigations following the proposed 12 GeV upgrade, it was eventually necessary to focus on two main themes. We deal with these in turn below. The first is the possibility of unambiguously determining the valence u and d quark distributions of the free nucleon in the region of Bjorken x above 0.4 (and as close as possible to 1). In particular, while the valence u distribution is relatively well known, it has recently been realized that the d distribution is very poorly determined in this region – at least if one requires that the determination should be demonstrably model independent. For the polarized valence distributions, ∆u and ∆d, the situation is even worse, with no measurements at all for x above 0.5. Experiments with He and H targets, following the 12 GeV upgrade, could resolve the longstanding problem concerning the valence d distribution for x up to 0.85 – establishing finally whether or not the predictions of perturbative QCD are correct. As a by-product one would complete our knowledge of the EMC effect over the full range of nuclear mass number. Using polarized proton and He targets one could also complete the determination of the polarized distributions ∆u and ∆d over the same region of x. The result of this program would be a definitive picture of the valence structure of the nucleon, including its spin dependence.

Anthony W. Thomas

Papers

Improved Treatment of Dark Matter Capture in Neutron Stars III: Nucleon and Exotic Targets

Indication of anomalous exchange in exclusive charmonium photoproduction

Classical Quark Models: An Introduction

QCD and a New Paradigm for Nuclear Structure

Ju l 2 00 0 HiX 2000 : Theory Summary