The MathNet Korea
Information Center for Mathematical Science

세미나

Information Center for Mathematical Science

세미나

한국고등과학원 세미나

The 1/2 BPS and regular LLM geometries are formed from the backreaction of a large number of D-branes on AdS_5 x S^5. The dual N=4 SYM operator to this configuration, and excitations thereof, thus lie outside of the planar limit of the theory. Explicitly the dual operators of these geometries are Schur polynomials labelled by a Young diagram with O(N^2) boxes and excitations of this configuration are restricted Schur polynomials obtained by adding boxes (and restriction labels) to this diagram. A special class of these backgrounds are labelled by Young diagrams with O(1) well separated corners. In the large N limit excitations localised at any one of these corners only mix with each other which gives rise to an emergent gauge theory. A recent proposal has argued that the planar limit of the emergent gauge theory is isomorphic to the planar limit of N=4 SYM and thus represents an integrable subsector of the theory. In this talk this proposal is reviewed and aspects of the weak and strong coupling evidence presented.

한국고등과학원 세미나

In the linear abelian Higgs model on a Riemann surface, vortices and antivortices attract one another and annihilate. By contrast, gauged nonlinear sigma models have vortices and antivortices which can coexist in stable equilibrium, at arbitrary positions. The moduli space of static k_+ vortex k_- antivortex solutions is noncompact even in the case when physical space is compact, since vortices and antivortices are forbidden to coincide, and is equipped with a natural Kaehler structure whose geodesics model low energy (anti)vortex scattering trajectories. I will describe a detailed study (joint with Nuno Romao) of this Kaehler geometry, concentrating on the case of vortex-antivortex pairs (k_+=k_-=1) on the plane and the sphere.

한국고등과학원 세미나

The composite Higgs models provide a natural solution to the Standard Model gauge hierarchy problem. In such models, the Higgs boson is a composite particle instead of an elementary one; it is identified as the pseudo Nambu-Goldstone boson of some strong dynamical new physics at scale O(TeV). In this talk, I will first review the motivations of the composite Higgs models, and then discuss their main phenomenological features, i.e. the existence of new vector and fermion resonances. I will take the Minimal Composite Higgs model as an example, to describe the strategies we use to search for the resonances at the LHC. Both current (Run II) and future (3000/fb) experimental reaches will be shown.

한국고등과학원 세미나

In this talk we study a finite horizon optimal contract problem with limited commitment in continuous time. We use the dual method and study the dual problem which is similar to an incremental irreversible investment problem. We transform the dual problem into an infinite series of optimal stopping problems, which essentially becomes a single optimal stopping problem. The optimal stopping problem has the same characteristics as that of finding the optimal exercise time of an American option, which has an integral equation representation. We recover the value function by establishing a duality relationship and provide some numerical results for optimal consumption strategies. This talk is based on a joint work with Hyeng Kuen Koo.

한국고등과학원 세미나

한국고등과학원 세미나

The inverse mean curvature flow (IMCF) has been extensively studied not only as a type of geometric flows, but also for its applications to geometric inequalities. The focus of this talk is primarily on homothetic solitons and translating solitons for the IMCF, which are special solutions deformed only for the homothety and the translation under the flow, respectively. One of the typical ways of constructing surfaces, and obtaining the rigidity and characterization of several surfaces is to build similar curves, for examples, a surface of revolution, a cyclic surface, a helicoidal surface, a ruled surface and a translation surface. In terms of such surfaces, we observe several examples for the homothetic and the translating solitons. In the last half, we classify the rotationally symmetric homothetic solitons and translating solitons, and show their asymptotic behavior.

한국고등과학원 세미나

The bilinear Bochner-Riesz operator is a bilinear multiplier operator related to convergence of the Fourier series. In this talk, we are concerned with boundedness of the bilinear Bochner-Riesz operator on Lebesgue spaces. Especially, we focus on our recent result for the bilinear operator, which is a joint work with Sanghyuk Lee and Ana Vargas. We make use of a decomposition which relates the estimate for the bilinear Bochner-Riesz operator to those of the square function for the classical Bochner-Riesz operator.

KAIST 수리과학과 세미나

It has been established now that long range dependence of stationary infinitely processes is strongly related to ergodic-theoretical properties of the shift operatior acting on its L'evy measure. We discuss one case in which these ideas can can be extended to stationary infinitely divisible random flelds.

서울대학교 지구환경과학부 세미나

최근 기후변화와 더불어 우리나라는 매년 해양위험기상(풍랑, 너울, 기상해일, 이안류, 해일 등)으로 인해 막대한 인명피해와 재산피해가 발생한다. 우리나라 뿐만 아니라 전 세계적으로 다양한 해양 위험기상의 피해를 최소화하고자 관측, 예측, 서비스 시스템을 구축하여 운영중이며, 시스템에서 생산된 정보를 이용하여 관계기관과 협조하여 해양 위험기상 재해에 대비하고 있다. 해양기상 관측망(해양기상부이, 파고부이, 등표기상관측장비, 연안방재관측장비, 항만기상관측장비, 기상관측선 및 해양기상기지)을 운영하고 있으며 점차 확대 계획을 가지고 있다. 또한, 해양위험기상, 해난사고, 수산업, 레저, 기후변화 등에 신속하고 효과적으로 대응할 수 있도록 광해역 뿐만 아니라 우리나라 연근해에 대한 상세한 해양 예측정보를 생산 제공하고 있다. 기상청에서는 다양한 현업 수치예보모델을 운영하고 있으며, 해양기상예보와 관련한 현업 파랑, 예측시스템뿐만 아니라 기상해일 예측시스템, 이안류 예측시스템, 총수위 예측시스템 등을 이용하여 해양재해를 줄이기 위한 정보들을 생산하고 있다. 다양한 해양기상 관측/예측자료를 통하여 일반 국민에게 정확한 해양기상 정보를 제공하기 위해서 무선 FAX 방송, 음성방송, 모바일 웹, 문자서비스를 시행중에 있다. 향후 해양기상정보의 고도화를 위해 항만, 항로, 레저 등의 기상정보를 확대 할 계획이다. 본 발표에서는 기상청과 유관기관의 관측, 예측자료 등을 포함한 해양기상정보를 실시간으로 수집, 분석, 통합하고 예보 및 감시 담당 업무에 활용할 수 있는 시스템을 소개하고, 그 현황 및 발전방향을 소개하고자 한다.

서울대학교 지구환경과학부 세미나

Studies using stable water vapor isotopes have been recently conducted over the past two decades because of difficulties in analysis and sample collection in the past. Stable water vapor isotope data provide information of the moisture transport from ocean to continent, which are also used to validate an isotope enabled general circulation model for paleoclimate reconstructions. The isotopic compositions of groundwater and water vapor also provide a clue to how moisture moves from soil to atmosphere by evapotranspiration. International Atomic Energy Agency designates the stations over the world to observe the water vapor isotopes. To analyze the water vapor isotopes, a cryogenic sampling method has been used over the past two decades. Recently, two types of laser-based spectroscopy have been developed and remotely sensed data from satellites have the global coverage. In this review, measurements of isotopic compositions of water vapor will be introduced and some studies using the water vapor isotopes will also be introduced. Finally, we will suggest the future study in Korea.

서울대학교 지구환경과학부 세미나

서울대학교 지구환경과학부 세미나

서울대학교 지구환경과학부 세미나

Disasters are increasing globally. The Asian region suffers the maximum impacts of the disasters in terms of the numbers of affected people as well as human and economic losses. The Sendai Framework for Disaster Risk Reduction 2015-2030 was adopted at the Third UN World Conference on Disaster Risk Reduction to prevent new, and reduce existing risk and to strengthen resilience to natural and man-made hazards, in order to achieve substantial reductions in disaster losses. This international commitment is also marked in both the Agenda 2030 for Sustainable Development and the Paris Agreement on climate change, thus disaster risk reduction has become an integral part of global effort to pursue sustainable development goals (SDGs). The Integrated Research on Disaster Risk programme (IRDR), co-sponsored by the International Science Council (ISC) and the United Nations Office for Disaster Risk Reduction (UNISDR) since 2010, is fully committed to advance the implementation of the Sendai Framework and contribute to the SDGs and Paris Agreement. IRDR’s mission is to develop trans-disciplinary, multi-sectorial alliances for in-depth, practical disaster risk reduction studies, and bridge among research communities and between research and relevant policy making and governance. Over the past 8 years, IRDR has made the guidance for forensic investigation of disasters, on standardising peril classification and the collection of comparable data on disaster losses, on governance in disaster risk management and on capacities building through development of national and thematic centres and young researchers. IRDR’s new effort is focusing on synthesis reporting, climate change adaption and cross-cutting projects such as DBAR.

서울대학교 지구환경과학부 세미나

The COMET Program has been providing educational resources to the geoscience community for over 28 years. A key strength of the program is the work of COMET instructional designers to craft training that meets the needs of the operational community to improve job performance. An additional application of these efforts is using the conceptual model animations and explanations in the classroom. The operational focus of COMET materials provides effective real-world examples that apply the scientific information being presented in universities. More recently, the program has expanded delivery of training to include educational videos through the COMET YouTube channel. New efforts to support the university community include the development of a lab packages for courses in synoptic meteorology and instrumentation. In the past two years, COMET has participated in international workshops to discuss how academic institutions can support national meteorological services by infusing operational applications of meteorology to better prepare graduates of their programs to work as weather forecasters. COMET’s training supports the forecasting competencies that have been developed by the World Meteorological Organization (WMO). COMET is part of the UCAR Community Programs (UCP), and this presentation is part of a UCP effort to connect with the universities to better understand how we can support their education and research efforts.

서울대학교 지구환경과학부 세미나

Cloud computing represents a fundamental change in the way IT services are developed, deployed, operated, and paid for, placing science communities in the middle of a major paradigm shift. There is also broad consensus that as data volumes grow rapidly, it is important to reduce data movement and bring processing and computations to the data. We need to give scientists an ecosystem that includes data, tools, models, and modern workflows, all residing in a cloud-like environment. Instead of moving data to users, data providers need to facilitate bringing analysis, visualization and other applications and tools to data – so called data proximate workflow capabilities. Unidata, a cyberinfrastructure facility, has been developing big-data infrastructure and data-driven scientific workflows using cloud computing technologies for accessing, analyzing, and visualizing geoscience data. Unidata has implemented the aforementioned services on the Unidata Science Gateway, hosted on the Jetstream cloud, a cloud facility funded by the U. S. National Science Foundation. Through the Unidata Science Gateway, researchers can gain access to an array of well-integrated resources. In this talk, we will present our work to date in developing the Unidata Science Gateway and the hosted services therein, as well as our future directions to benefit the atmospheric sciences community.

서울대학교 지구환경과학부 세미나

In this study we present a detailed analysis of the impact of GPS radio occultation (RO) data on the prediction of Typhoon Nuri (2008), which was observed during the field phase of T-PARC (THORPEX Pacific Asia Regional Campaign) over the western North Pacific. Typhoon Nuri was declared a tropical storm at 1800 UTC 16 August 2008, and its incipient disturbance can be tracked more than ten days prior to tropical storm formation. Nuri is a challenging case for numerical model prediction. The NCEP GFS model failed to predict the storm formation in operation. The WRF model, initialized with either the NCEP or ECMWF global analysis, also failed to predict its genesis. However, with the assimilation of GPS RO soundings obtained from COSMIC and other missions, using a two-dimensional observation operator, the moisture analysis was substantially improved. This enhanced moisture analysis led to a more accurate prediction of the convection associated with the incipient disturbance, which developed into a robust mid-level vortex. This mid-level vortex was responsible for the subsequent formation of Nuri through its interaction with convective and boundary layer processes. Without the assimilation of GPS RO data, the convection was suppressed and the mid-level vortex did not develop, and the model failed to predict the genesis of Nuri. Further experiments on nine additional typhoons over the western North Pacific between 2008-2010 showed that the assimilation of GPS RO data substantially improved the model’s ability to forecast tropical cyclogenesis.

서울대학교 지구환경과학부 세미나

During a major sudden stratospheric warming (SSW) event, the Northern Hemisphere wintertime polar vortex can split or become highly displaced off the pole. Stratospheric changes induced by SSW have been linked to near-surface meteorological conditions. With increasing high-altitude observations and modelling capabilities, the impact of SSW on the mesosphere and lower thermosphere is also evident. This talk will highlight some dynamical and tracer responses to SSW over the whole neutral atmosphere.

고려대학교 화학과 세미나

고려대학교 화학과 세미나

고려대학교 화학과 세미나