E ffective contact tracing is critical to controlling the spread of coronavirus disease (COVID-19) (1). South Korea adopted a rigorous contact-tracing program comprising traditional shoe-leather epidemiology and new methods to track contacts by linking large databases (global positioning system, credit card transactions, and closed-circuit television). We describe a nationwide COVID-19 contact tracing program in South Korea to guide evidence-based policy to mitigate the pandemic (2). The Study South Korea's public health system comprises a national-level governance (Korea Centers for Disease Control and Prevention), 17 regional governments, and 254 local public health centers. The first case of COVID-19 was identified on January 20, 2020; by May 13, a total of 10,962 cases had been reported.

Transport simulations are very valuable for extracting physics information from heavy-ion collision experiments. With the emergence of many different transport codes in recent years, it becomes important to estimate their robustness in extracting physics information from experiments. We report on the results of a transport code comparison project. 18 commonly used transport codes were included in this comparison: 9 Boltzmann-Uehling-Uhlenbeck-type codes and 9 Quantum-MolecularDynamics-type codes. These codes have been required to simulate Au+Au collisions using the same physics input for mean fields and for in-medium nucleon-nucleon cross sections, as well as the same initialization set-up, the impact parameter, and other calculational parameters at 100 and 400 AMeV incident energy. Among the codes we compare one-body observables such as rapidity and transverse flow distributions. We also monitor non-observables such as the initialization of the internal states of colliding nuclei and their stability, the collision rates and the Pauli blocking. We find that not completely identical initializations constitute partly for different evolutions. Different strategies to determine the collision probabilities, and to enforce the Pauli blocking, also produce considerably different results. There is a substantial spread in the predictions for the observables, which is much smaller at the higher incident energy. We quantify the uncertainties in the collective flow resulting from the simulation alone as about 30% at 100 AMeV and 13% at 400 AMeV, respectively. We propose further steps within the code comparison project to test the different aspects of transport simulations in a box calculation of infinite nuclear matter. This should, in particular, improve the robustness of transport model predictions at lower incident energies where abundant amounts of data are available.

We solve for properties of 6 Li in the ab initio No-Core Full Configuration approach and we separately solve for its ground state and J π = 2 + 2 resonance with the Gamow Shell Model in the Berggren basis. We employ both the JISP16 and chiral NNLOopt realistic nucleon-nucleon interactions and investigate the ground state energy, excitation energies, point proton root-meansquare radius and a suite of electroweak observables. We also extend and test methods to extrapolate the ground state energy, point proton root-mean-square radius, and electric quadrupole moment. We attain improved estimates of these observables in the No-Core Full Configuration approach by using basis spaces up through Nmax = 18 that enable more definitive comparisons with experiment. Using the Density Matrix Renormalization Group approach with the JISP16 interaction, we find that we can significantly improve the convergence of the Gamow Shell Model treatment of the 6 Li ground state and J π = 2 + 2 resonance by adopting a natural orbital single-particle basis.

Encouraged by recent developments in AdS/QCD models for light quark system, we study heavy quarkonium in the framework of the AdS/QCD models. We calculate the masses of $c\bar c$ vector meson states using the AdS/QCD models at zero and at finite temperature. Among the models adopted in this work, we find that the soft wall model describes the low-lying heavy quark meson states at zero temperature relatively well. At finite temperature, we observe that once the bound state is above $T_c$, its mass will increase with temperature until it dissociates at a temperature of around $494 {\rm MeV}$. It is shown that the dissociation temperature is fixed by the infrared cutoff of the models. The present model serves as a unified non perturbative model to investigate the properties of bound quarkonium states above $T_c$.Comment: 9 pages, 1 figure, minor revision, to appear in phys. Rev.

We perform the renormalization group analysis on the dynamical symmetry breaking under strong external magnetic field, studied recently by Gusynin, Miransky and Shovkovy. We find that any attractive four-Fermi interaction becomes strong in the low energy, thus leading to dynamical symmetry

We describe in-medium properties of hadrons in dense matter near chiral restoration using a Wilsonian matching to QCD of an effective field theory with hidden local symmetry at the chiral cutoff Λ. We find that chiral symmetry is restored in vector manifestationà la Harada and Yamawaki at a critical matter density nc. We express the critical density in terms of QCD correlators in dense matter at the matching scale. In a manner completely analogous to what happens at the critical N c f and at the critical temperature Tc, the vector meson mass is found to vanish (in the chiral limit) at chiral restoration. This result provides a support for Brown-Rho scaling predicted a decade ago.Following recent developments on hidden local symmetry [1] and color-flavor locking [2] in the hadronic sector, Brown and Rho proposed [3,4] that the vector manifestation (VM) scenario of Harada and Yamawaki [1] for the realization of chiral symmetry in strongly interacting systems which was shown to be valid for large number of flavors N f should be also applicable to high density (or high temperature) hadronic matter relevant to the interior of compact stars (or relativistic heavy-ion process) and that as a consequence, the scaling behavior of vector mesons in medium proposed by Brown and Rho [5] near chiral restoration critical density n c (or temperature T c ) follows from VM. That the vector meson mass vanishes in the chiral limit at the critical temperature T c in accordance with the VM mode was recently shown to hold by Harada and Sasaki [6]. In this paper, we supply the arguments to suggest that the same phenomenon occurs in density, namely that at n = n c , the vector meson mass vanishes in the chiral limit.We begin by giving a brief summary of the key arguments as to how VM figures in the properties of hadrons in medium.To study how hadrons behave in dense (hot) medium starting from normal conditions, one resorts to effective field theories with Lagrangians that have the assumed symmetry properties of QCD. Such Lagrangians are constructed so as to describe low-energy interactions of hadrons in medium-free vacuum. As one increases the density (temperature), that is, as the scale is changed, the flow of the given theory is not unique even though the symmetries remain unchanged. As shown by Harada and Yamawaki [7], the effective field theory with hidden local symmetry (HLS) [8,9] can flow to two or more different fixed points depending upon how the parameters of the Lagrangian are dialed. It turns out that if the bare parameters of the Lagrangian are matchedà la Wilson to QCD at the chiral scale Λ χ ∼ 4πf π (where f π is the pion decay constant) above the vector meson mass -based on the systematic chiral perturbation with HLS [10][11][12][13], then the flow comes out to be unique with the fixed point [7]. This implies that the different flows typically present in all effective field theories, even if consistent with the symmetries of QCD, may not correctly represent QCD dynamics unless the bare parameters of the effective Lagrangi...

The location of the neutron drip line, currently known for only the lightest elements, remains a fundamental question in nuclear physics. Its description is a challenge for microscopic nuclear energy density functionals, as it must take into account in a realistic way not only the nuclear potential, but also pairing correlations, deformation effects and coupling to the continuum. The recently developed deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) includes all three aforementioned effects in the description of nuclei throughout the nuclear chart. Here, the DRHBc with the successful density functional PC-PK1 is used to investigate whether and how deformation influences the prediction for the neutron drip-line location for even–even nuclei with [Formula: see text], where many isotopes are predicted deformed. The results are compared with those based on the spherical relativistic continuum Hartree–Bogoliubov (RCHB) theory and discussed in terms of shape evolution and the variational principle. It is found that the Ne and Ar drip-line nuclei are different after the deformation effect is included. The direction of the change is not necessarily towards an extended drip line, but rather depends on the evolution of the degree of deformation towards the drip line. Deformation effects as well as pairing and continuum effects treated in a consistent way can affect critically the theoretical description of the neutron drip-line location.

Tuberculosis (TB) in Korea remains a serious health problem with an estimated 77 per 100,000 incidence rate for 2016. This makes Korea as the only OECD country with high incidence of TB. The government has increased budgets and strengthened patient management policies since 2011. The management of latent tuberculosis was added to the response with strengthened and extensive contact investigations in the five-year tuberculosis control plan (2013–2017) and implementation was established in 2013. Due to these efforts Korea has achieved an average 5.2% reduction annually in tuberculosis incidence rate between 2011 and 2016. To further expedite the reduction of the TB burden the government has introduced additional measures including mandatory screening of latent tuberculosis infection for community workers in congregate settings including daycare centers for children, kindergarten, and teachers in schools and health care workers in clinics and hospitals to solve the problems identified through contact investigations in 2017.Providing high quality free diagnosis and treatment of active TB including for multidrug resistant TB combined with active contact investigations is the mainstay of the current programmatic response in Korea. However, the limitation of existing tools for LTBI pose challenge including absence of best mechanism for effective communication with professionals and the public, the need for at least 3 months of treatment and the risk of side effects. Developing effective tools will help to overcome these challenges.