2016年4月1日 | 新着情報
我々の研究グループに、研究員として植本さん、学振PD特別研究員として野村さんが着任し、物理学類4年生の堀川さんが新たに研究室配属となりました。また、齊藤さん、八百板さんは修士課程M1に進学し、博士号を取得した佐藤さんは学振PD特別研究員として在籍したままドイツのマックスプランク物質構造・ダイナミクス研究所に滞在する予定です。
寺崎さん（准教授）は、2016年4月1日よりチェコ工科大学プラハ実験応用物理学研究所に赴任しました。
2016年3月25日 | 新着情報
佐藤さんが博士(理学)、桑原さんと倪さんが修士(理学)を取得しました。
佐藤さんはD2での早期修了で、学長表彰を受けました。
学長表彰された佐藤さん(D2)
2016年3月8日 | 新着情報
2016年4月4日（月）に、マンチェスター大学のRaymond Bishop氏による結合クラスター法(Coupled Cluster Method)に関するセミナーを予定しています。本セミナーは、計算科学研究センターの計算科学コロキウムとして開催されます。以下と同様の内容ですが、計算科学研究センターのHPは、こちらをご覧ください。
Date/Time: April 4th (Mon), 15:00-
Place: Meeting Room A (1F), Center for Computational Sciences
Lecturer: Raymond Bishop (University of Manchester, UK)
Title: Highly Frustrated Spin-Lattice Models of Magnetism and Their Quantum Phase Transitions: A Microscopic Treatment via the Coupled Cluster Method
Abstract: The coupled cluster method1) (CCM) is one of the most pervasive, most powerful, and most successful of all ab initio formulations of quantum many-body theory. It has probably been applied to more systems in quantum field theory, quantum chemistry, nuclear, subnuclear, condensed matter and other areas of physics than any other competing method. The CCM has yielded numerical results which are among the most accurate available for an incredibly wide range of both finite and extended physical systems defined on a spatial continuum. These range from atoms and molecules of interest in quantum chemistry, where the method has long been the recognized “gold standard”, to atomic nuclei; from the electron gas to dense nuclear and baryonic matter; and from models in quantum optics, quantum electronics, and solid-state optoelectronics to field theories of strongly interacting nucleons and pions.
This widespread success for both finite and extended physical systems defined on a spatial continuum2) has led to recent applications to corresponding quantum-mechanical systems defined on an extended regular spatial lattice. Such lattice systems are nowadays the subject of intense theoretical study. They include many examples of systems characterised by novel ground states which display quantum order in some region of the Hamiltonian parameter space, delimited by critical values which mark the corresponding quantum phase transitions. The quantum critical phenomena often differ profoundly from their classical counterparts, and the subtle correlations present usually cannot easily be treated by standard many-body techniques (e.g., perturbation theory or mean-field approximations). A key challenge for modern quantum many-body theory has been to develop microscopic techniques capable of handling both these novel and more traditional systems. Our recent work shows that the CCM is capable of bridging this divide. We have shown how the systematic inclusion of multispin correlations for a wide variety of quantum spin-lattice problems can be efficiently implemented with the CCM3). The method is not restricted to bipartite lattices or to non-frustrated systems, and can thus deal with problems where most alternative techniques, e.g., exact diagonalisation of small lattices or quantum Monte Carlo (QMC) simulations, are faced with specific difficulties.
In this talk I describe our recent work that has applied the CCM to strongly interacting and highly frustrated spin-lattice models of interest in quantum magnetism, especially in two spatial dimensions. I show how the CCM may readily be implemented to high orders in systematically improvable hierarchies of approximations, e.g., in a localised lattice-animal-based subsystem (LSUBm) scheme, by the use of computer-algebraic techniques. Values for ground-state (and excited-state) properties are obtained which are fully competitive with those from other state-of-the-art methods, including the much more computationally intensive QMC techniques in the relatively rare (unfrustrated) cases where the latter can be readily applied. I describe the method itself, and illustrate its ability to give accurate descriptions of the ground-state phase diagrams of a wide variety of frustrated magnetic systems via a number of topical examples of its high-order implementations, from among a very large corpus of results for spin lattices. The raw LSUBm results are themselves generally excellent. I show explicitly both how they converge rapidly and can also be accurately extrapolated in the truncation index, m → ∞, to the exact limit.
_____________________________________________________________
2016年1月25日 | 新着情報
当研究室の大学院生である佐藤駿丞さんの博士学位論文審査・公聴会が以下のように開催予定です。
2016年1月13日 | 新着情報
2016年2月5日(金)に、オーストラリア国立大学のCedric Simenel氏のセミナーを以下の通り行います。また、Simenel氏は2/3-10の間、筑波大学の原子核理論研究室に滞在予定です。
Date/Time: February 5th (Fri), 13:45-
Place: D312, Institute for Natural Sciences (自然学系D棟)
Lecturer: Cedric Simenel (Australian National University, Canberra, Australia)
Title: Counting particles in microscopic systems
Abstract: Simple observables such as the number of particles might be difficult to descrybe when a quantum composite system encounters a violent perturbation, for instance in collisions of atomic nuclei. It requires a predictive many-body theory to describe the time evolution of the system accounting for indiscernibility of identical particles. Our goal is rather simple: predicting the probability for a number of transferred particles in such a collision. To keep the amount of work for the physicist and his/her computer to a reasonable level, approximations are considered rather than solving the full Schrödinger equation. The Balian-Veneroni variational principle provides a useful theoretical framework to build dynamical microscopic models. To solve this variational principle, one has to choose one particular type of observable of interest. For expectation values of one-body operators, like the average number of transferred particles, this leads to the time-dependent Hartree-Fock (TDHF) theory. For their fluctuations, the Balian-Vénéroni variational principle leads to an equation equivalent to the time-dependent Random Phase Approximation. Examples of applications will be taken within the nuclear physics context.
2015年12月15日 | 新着情報
第35回つくば不安定核セミナーを東京理科大・野田キャンパスで開催します。また、セミナーに先立ち、10:00-12:00, 13:10-15:10には学部生・修士以上を対象とした講義を行います。
講師: 藤田 佳孝
所属:大阪大学 核物理研究センター/理学研究科物理学専攻
日時: 2016年1月21日(木)16:00‒17:30 場所:東京理科大学 野田キャンパス 4号館4階 演習室1(44S11)
題目：ガモフ・テラー遷移の研究から見える原子核物理
(Nuclear Physics Revealed by the Study of Gamow-Teller Transitions)
| 新着情報
Dec.18, 2015, 13:45 at D312 (自然学系D棟)
Speaker: Das Pemmaraju (The Molecular Foundry and Chemical Sciences
Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA)
Title: First-principles interpretation of attosecond time-resolved XUV absorption spectroscopy of laser excited Silicon
Abstract: The availability of ultrafast x-ray pulses both from powerfulfree electron laser light-sources as well as table top high-harmonicgeneration, has significantly enhanced the utility of core-levelspectroscopies as probes for investigating dynamical processes infunctional materials. Theoretical approaches to complement these time-domain experiments are therefore actively being developed. In this context, I will discuss recent efforts that employ a combination of real-time time-dependent density functional theory (TDDFT), occupancy-constrained density functional theory and many-body perturbation theory approaches to help interpret spectral signatures in attosecond time-resolved core-level spectroscopic measurements on laser-excited silicon. Out-of-equilibrium electron-hole densities obtained from real-time TDDFT simulations of the valence electron dynamics are used to estimate the transient modulation of L-edge absorption in femtosecond infrared pump – attosecond XUV probe experiments. Furthermore, the contribution of electron-phonon and electron-electron scattering mechanisms to the lifetime broadening observed in measured L-edge spectra is estimated using occupation-constrained density functional theory and GW calculations respectively.
2015年12月9日 | 新着情報
筑波大学計算科学研究センター研究員公募
Theoretical Nuclear Physics Division in Center for Computational Sciences, University of Tsukuba anticipates an opening for a postdoctoral researcher in nuclear theory beginning in April of 2016. Current research efforts by Profs. Nakatsukasa, Yabana, Hashimoto, and Hinohara include works on applications of density functional theory, theories of large amplitude collective motion, and cluster/few-body models, to problems of nuclear structure and reaction. Applicants abroad should send the application materials, both by postal mail and by email with attached PDF files.
Prof. T. NakatsukasaCenter for Computational Sciences, University of Tsukuba1-1-1 Tennodai, Tsukuba 305-8577, Japan
2015年10月10日 | 新着情報
2015年10月16日（金）13:00より、ワシントン大学 Institute for Nuclear Theory のGeorge Bertsch氏によるセミナーを予定しています。
