Abstract: The common use of computational models, in combination with physical observations, has expanded our understanding and ability to anticipate behaviors in a variety of physical systems. With relevant physical observations, it is possible to calibrate a computational model, and even estimate systematic discrepancies between the model reality. Estimating and quantifying the uncertainty in this model discrepancy can lead to reliable prediction uncertainties - so long as this prediction is âsimilarâ to the available physical observations. Exactly how to define \"similar\" has proven difficult in many applications. Clearly it depends on how well the computational model captures the relevant physics in the system, as well as the portability of the model discrepancy in moving from the available physical data to the prediction. This talk will discuss these concepts using computational models ranging from simple to complex.
Abstract: The RIKEN Radioactive Isotope Beam Factory (RIBF) has been successfully operating for over ten years since the first beam at the end of 2006 with the aim of accessing the unexplored region on the nuclear chart, far from stability. The continuous efforts have improved the performance of the RIBF accelerator complex. We did a lot of things to upgrade accelerator performance, including construction a 28-GHz superconducting ECR ion source with a new injector linac and development of new types of charge strippers. This seminar focuses on the charge strippers. The RIBF accelerator complex uses the two charge strippers for effective acceleration of the uranium ions. These charge strippers could be a bottle-neck problem especially in high power operation. We carried out elaborating R&D works to replace the conventional carbon foils with the new types of the charge strippers which can survive irradiation of high intensity heavy ion beams, reaching to the solutions of helium gas stripping for the first stripper and rotating disks using highly oriented graphene sheet for the second one so far. This talk overviews R&D works for the charge strippers since 2008 and reports the present status of the charge strippers currently used for the operation with future prospect.
Abstract: I will review the ideas of large N and effective field theories. In the limit of a large number of colors an enhanced symmetry of QCD emerges. This symmetry has been used to understand properties of hadrons and nuclei. It has also been used to reduce the number of unknown parameters in effective field theories for few nucleon systems. I will discuss some of these applications and introduce an additional manifestation of the large N limit.
Abstract: Helium is the only element that remains liquid under normal pressure down to zero temperature. Below 2.17K, the bosonic isotope helium-4 undergoes a phase transition to a superfluid. Motivated by this intriguing bulk behavior, the properties of finite-sized helium droplets have been studied extensively over the past 25 years or so. A number of properties of liquid helium-4 droplets are, just as those of nuclei, well described by the liquid drop model. The existence of the extremely fragile helium dimer was proven experimentally in 1994 in diffraction grating experiments. Since then, appreciable effort has gone into creating and characterizing trimers, tetramers and larger clusters. The ground state and excited state of the helium trimer are particularly interesting since these systems are candidates for Efimov states. The existence of Efimov states, which are unique due to scale invariance and an associated limit cycle, was predicted in 1971. However, till recently, Efimov states had -- although their existence had been confirmed experimentally -- not been imaged directly. Recently, ingenious experimental advances made it possible to directly image the quantum mechanical density distribution of helium dimers and trimers. I will review some of these experiments and related theoretical calculations that led to the experimental detection of the excited helium trimer Efimov state.