ニュース
187件のニュース / 2020年
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2020-07-01
セミナーレポート
Math seminar by Dr. Ryusuke Hamazaki on Jun 24, 2020
The iTHEMS Math seminar entitled "Universal Error Bound for Constrained Quantum Dynamics" by Dr. Ryusuke Hamazaki, was held on 24 Jun. In the first part, the speaker first introduced two physical examples of constrained dynamics including Rydberg atoms. Then, he explained the motivation of his study: finding quantitative error estimates of constrained-dynamics in generic gapped quantum systems. He introduced his result about a universal and rigorous error bound for a constrained-dynamics approximation in generic gapped quantum systems. Then, he gave the outline of the proof of the error bound. The proof uses the Schrieffer-Wolf transformation (SWT) and Sylvester equation. In the second talk, he gave a more precise proof of the error bound. In the proof, several computational techniques are used.
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2020-06-29
お知らせ
Dr. Tetsuo Hatsuda supervised a book “The Usefulness of Useless Knowledge" will be released on July 22, 2020
“The Usefulness of Useless Knowledge" supervised by Dr. Tetsuo Hatsuda, will be released on July 22. Please check on the link for more information.
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2020-06-26
リサーチニュース
RIKEN Research: Light nucleus predicted to be stable despite having two strange quarks
Adding an exotic particle known as a Xi hyperon to a helium nucleus with three nucleons could produce a nucleus that is temporarily stable, calculations by RIKEN nuclear physicists have predicted1. This result will help experimentalists search for the nucleus and provide insights into both nuclear physics and the structure of neutron stars.
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2020-06-26
書籍
「役に立たない」科学が役に立つ（翻訳本）
エイブラハム・フレクスナー／ロベルト・ダイクラーフ [著] 初田 哲男 [監訳] 野中 香方子／西村 美佐子 [訳] Abraham Flexner (with a companion essay by Robbert Dijkgraaf), The Usefulness of Useless Knowledge (Princeton University Press, 2017)を翻訳
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2020-06-26
リサーチニュース
RIKEN Research: Modeling the insides of a neutron star
Astrophysicists at RIKEN have developed an improved model for the interior structure of neutron stars. It agrees well with obser-vations, and, unlike previous models, it can be extended to consider what happens when two neutron stars merge.Neutron stars are incred-ibly dense, being the size of a medium asteroid but having masses similar to that of the Sun. They have an onion-like structure, which theorists have been trying to model. To read more, please see the related link.
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2020-06-26
リサーチニュース
"Minute-to-minute weather prediction" article on RIKEN RESEARCH by Takemasa Miyoshi
Deputy Program Director at iTHEMS Dr. Takemasa Miyoshi talks about weather simulation using a supercomputer "Fugaku".
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2020-06-25
今週の論文Week 4 of June
Title: Physical Conditions and Particle Acceleration in the Kiloparsec Jet of Centaurus A Author: Takahiro Sudoh, Dmitry Khangulyan, Yoshiyuki Inoue arXiv: http://arxiv.org/abs/2006.12519v1
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2020-06-25
リサーチニュース
A Black Hole’s Lunch Provides a Treat for Astronomers
iTHEMS Senior visiting scientist, Gordon Baym, gave a comment on GW190814 in New York Times.
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2020-06-25
リサーチニュース
Is interdisciplinary research really the best way to tackle global challenges?
In this magazine article, various researchers include Dr. Tetsuo Hatsuda advocate for issues and opinions about interdisciplinary research. Please read it at the related link.
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2020-06-25
リサーチニュース
Neutron star particles go under the LHC microscope
This article form Symmetry contains an interview with Dr. Tetsuo Hatsuda, Program Director at iTHEMS . Please enjoy.
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2020-06-25
セミナーレポート
Dark Matter Working Group Seminar on June 22, 2020
Astrophysical observations are really important for understanding the nature of dark matter (DM) in multiple aspects. For example, the measurement of the temperature evolution of the neutron star (NS) provides us with new information about the properties of weakly interacting massive particle (WIMP). Since WIMP can interact with nucleon, of which scattering process is intensively searched in direct detection experiments, WIMP in our Universe should be captured by NSs. When the accumulated WIMPs annihilate inside the NS they heat up to modify the temperature evolution of the NS. Such a phenomenon is especially to probe the WIMP in the mass range of m
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2020-06-23
セミナーレポート
Math seminar by professor Tasuku Soma
In 17 June, professor Tasuku Soma (The university of Tokyo) gave a seminar on scaling problem and information geometry at the math seminar. In the first part he gave an introductory talk on scaling problem. Assume matrix A is given and each entry of A is positive. Matrix scaling problem is to find good matrix L,R with which LAR and (LAR)* has nice property. He then introduced Sinkhorn algorithm. This is an algorithm to calculate "LAR" in the above problem. He then explained operator scaling, which is quantum analogue of matrix scaling. He explained his recent result on the operator scaling and information geometry. It is known by Csizar that Sinkhorn algorithm for matrix scaling is actually an alternating e-projection, which appears in the information geometry. He then introduced his recent work with Takeru Matsuda. In that work, they proved that operator scaling is also an alternating e-projection.
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2020-06-19
セミナーレポート
Report on iTHEMS Intensive Course by Dr. Yoh Iwasa - Sex expression and sex allocation of marine organisms
This month, we hold 4-day intensive course of mathematical biology. This is especially for non-expert. On June 18th, Dr. Yoh Iwasa talked about various mysteries of sex. For instance, anemonefishes (kumanomi, in Japanese) are male when they are born. As they get bigger, they become female. Interestingly, some coral reef fishes are opposite. As they get bigger, they become male. Why do they show such sex expressions? Dr. Iwasa astonished us that various mysteries of sex can be resolved from the view point of game theory. According to him, “Anything related to sexual system can be quantified. In terms of the number of offspring, number of reproductive success, and other things. Success of the male depends on whether there are many more males or females. Obviously, this is the game theoretic view point.” During the lecture, the philosophy behind the mathematical modeling was explained in detail. The lecture on Thursday was attended by more than 160 people through Zoom and Youtube. Dr. Iwasa answered all the uncountable questions from the audience. The wonderful intensive course continues. - Gen Kurosawa
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2020-06-18
今週の論文Week 3 of June
Title: PT-symmetric non-Hermitian quantum many-body system using ultracold atoms in an optical lattice with controlled dissipation Author: Yosuke Takasu, Tomoya Yagami, Yuto Ashida, Ryusuke Hamazaki, Yoshihito Kuno, Yoshiro Takahashi arXiv: http://arxiv.org/abs/2004.05734v2
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2020-06-15
セミナーレポート
Biology Seminar by Dr. Martin Skrodzki on June 10, 2020
On 10th June, Martin Skrodzki talked about Turing models. Historically, Turing's models have been very successful to describe various pattern-formations on a two dimensional plane. He briefly introduced examples and then talked about three dimensional space, showing amazingly diverse patterns the model can cover. His talk generated stimulation discussion among the audience. Thank you so much for the great talk, Martin! -Ryosuke Iritani
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2020-06-15
セミナーレポート”Field theoretical approach to relativistic hydrodynamics" on June 12, 2020.
The iTHEMS Theoretical Physics Seminar is hold on June 12, 2020. The speaker is Masaru Hongo in University of Illinois at Chicago/RIKEN iTHEMS. The title is ”Field theoretical approach to relativistic hydrodynamics”. Hydrodynamics is a low-energy effective theory of a conserved charge density, which describes a long-distance and long-time behavior of many-body systems. It is applicable not only to a non-relativistic weakly-interacting dilute gas but also a relativistic strongly-interacting dense liquid like a quark-gluon plasma. The main purpose of this seminar is to explain how we can derive the hydrodynamic equation from the underlying field-theoretical description of systems [1-3]. The derivation is based on the recent development of non-equilibrium statistical mechanics, and they show that the procedure to derive hydrodynamic equations is similar to the so-called renormalized/optimized perturbation theory. Also, to describe transport phenomena in local thermal equilibrium, they give a path-integral formula for a thermodynamic functional, which results in the emergence of thermally induced curved spacetime [2]. These results enable us to derive hydrodynamic equation based on quantum field theories.
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2020-06-15
セミナーレポート
Dark Matter Working Group Seminar on June 12, 2020
Among the numbers of dark matter (DM) scenarios, Weakly Interacting Massive Particle (WIMP) is one of the best-studied particles. It attracts special attention because of its beautiful mechanism to achieve the relic abundance of dark matter which is referred to as the thermal freeze-out. In the early Universe, the annihilation of the WIMP into the standard model (SM) particles and its inverse process are frequent enough to sustain the thermal equilibrium. At a certain point, WIMP decouples from the thermal bath then its number density, which is directly related to the relic abundance, is fixed. The strength of the coupling between WIMP and the SM sector determines the annihilation frequency. The same coupling is also responsible for the energy transfer between the SM particles and WIMP. The constraints on that scattering cross-section (i.e., the energy transfer between two sectors) have already been severely constrained by direct detection experiments. This motivates us to consider such a model that the coupling is so small and the relic abundance is achieved by a resonant annihilation at a certain mass. In this way, we can satisfy the requirements from the results of direct detection experiments. The small coupling between the SM sector and WIMP could lead to a non-equilibrium between them around the freeze-out epoch. Such a situation is referred to as the kinetic decoupling. The kinetic decoupling before the freeze-out affects the calculation of the relic density, which is a crucial part of the WIMP scenario. In this talk, Dr. Abe clarified the effect of the kinetic decoupling in terms of the coupling constant taking two examples of fermionic and scalar DM in the Higgs portal scenario. He calculated the freeze-out process in detail and showed that the scattering cross-section, which is measured at direct detection experiments, should also be different from the case where assumes a complete thermal equilibrium. We could see the signature of such DM in near-future experiments. We should carefully work on the synergy between different types of experiments in this high-precision era of DM search.
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2020-06-11
今週の論文Week 2 of June
Title: d∗(2380) dibaryon from lattice QCD Author: Shinya Gongyo, Kenji Sasaki, Takaya Miyamoto, Sinya Aoki, Takumi Doi, Tetsuo Hatsuda, Yoichi Ikeda, Takashi Inoue, Noriyoshi Ishii arXiv: http://arxiv.org/abs/2006.00856v1 Title: Universality classes of non-Hermitian random matrices Author: Ryusuke Hamazaki, Kohei Kawabata, Naoto Kura, Masahito Ueda arXiv: http://arxiv.org/abs/1904.13082v7
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2020-06-05
セミナーレポート
Biology Seminar by Dr. Hiroshi Yokota on June 3, 2020
In the 6th biology seminar, Hiroshi Yokota (iTHEMS fellow at Kyoto University) talked about his theoretical work on the energy of chromosome loop structure (collaborative work with Masashi Tachikawa). Through the modeling, he talked about the possibility that the chromosome loop structure may occur due to ATP hydrolysis. His work will stimulate future debate over the source of the energy needed for chromosome loops to occur. Great talk, Hiroshi! -Ryosuke Iritani
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2020-06-04
今週の論文Week 1 of June
Title: Probing the Universality of Topological Defect Formation in a Quantum Annealer: Kibble-Zurek Mechanism and Beyond Author: Yuki Bando, Yuki Susa, Hiroki Oshiyama, Naokazu Shibata, Masayuki Ohzeki, Fernando Javier Gómez-Ruiz, Daniel A. Lidar, Adolfo del Campo, Sei Suzuki, Hidetoshi Nishimori arXiv: http://arxiv.org/abs/2001.11637v3 Title: Effective quantum kinetic theory for spin transport of fermions with collsional effects Author: Di-Lun Yang, Koichi Hattori, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/2002.02612v2 Title: Entanglement of Local Operators and the Butterfly Effect Author: Jonah Kudler-Flam, Masahiro Nozaki, Shinsei Ryu, Mao Tian Tan arXiv: http://arxiv.org/abs/2005.14243v1 Title: Clustering of conditional mutual information for quantum Gibbs states above a threshold temperature Author: Tomotaka Kuwahara, Kohtaro Kato, Fernando G. S. L. Brandão arXiv: http://arxiv.org/abs/1910.09425v2
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2020-06-01
セミナーレポート
QFT-core Seminar by Dr. Ryusuke Hamazaki on May 29, 2020
The second QFT-core seminar entitled “Localization and universality in non-Hermitian many-body systems” given by Dr. Ryusuke Hamazaki (RIKEN Hakubi/iTHEMS) was held on May 29. Non-Hermitian physics is now one of the topics studied actively, and he is one of the world-leading physicists of this topic. In the seminar, first, he introduced the basic ideas of thermalization of the isolated quantum systems and non-Hermitian physics with simple examples. After that, some cutting-edge progress of non-Hermitian many-body localization, and universality of non-Hermitian random matrices were introduced. The seminar was held via the Zoom online conference system. Around 20 people participated in the seminar and joined the active discussion.
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2020-06-01
セミナーレポート
Biology Seminar on May 27, 2020
On 27 May, Ayaka Kato, The University of Tokyo, gave a talk at the 6th iTHEMS Biology Seminar. In this seminar, Ayaka talked about the results of the research on mathematical modeling of dopamine-related phenomena. It was not previously known how dopamine is involved in motivation, but in Ayaka's previous studies, the mathematical model from several previous experiments was proposed. In this seminar, Ayaka presented a new model that incorporates learning decay and successfully reproduces the real behavior on a computer simulation based on her new model. Since modeling the relationship between dopamine and motivation is very important both psychologically and medically, I felt that the results of these studies would not only benefit basic research but would also serve as a basis for general-purpose practical science and improve their research motivation.
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2020-05-29
セミナーレポート
Math Seminar by Dr. Masaki Taniguchi
The iTHEMS Math seminar entitled "Knotted 2-spheres in the 4-space and Yang-Mills gauge theory," by Dr. Masaki Taniguchi, was held on 27 May. In the first part, the speaker reviewed that classical knot theory and history of knot. Especially, he introduced that one and two dimensional knot theory, and gave many examples. For one dimensional knot theory, he explained the fundamental problem of knot theory, i.e., the problem of classifying 1-knots up to equivalent. As an example, he introduced a knot invariant coming from 3-colorings. For two dimensional knot theory, he explained the problem of how we write diagrams of 2-knots in four dimensional Euclidean space. Then he introduced the motion picture. In the second part, the speaker focuses on a problem considered in differential topology. First, he explained that the fundamental problem in differential topology. Next, he introduced gauge theory and some examples. Finally, as the main result of the talk, he explained his theorem about the difference between continuous and smooth two dimensional knots. He then introduced that the proof uses Yang-Mills gauge theory for 4-manifolds obtained by the surgery of 2-knots.
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2020-05-28
受賞情報
Dr. Shigenori Otsuka received 11th annual RIKEN Research Incentive Award (Ohbu Award)
Shigenori Otsuka received "FY2019 Researcher Incentive Award (桜舞賞)" on March 10, 2020 for his achievements in the "Development of a novel three-dimensional precipitation nowcast method and its real-time demonstration". Congratulations!
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2020-05-28
今週の論文Week 5 of May
Title: Revisiting relativistic magnetohydrodynamics from quantum electrodynamics Author: Masaru Hongo, Koichi Hattori arXiv: http://arxiv.org/abs/2005.10239v1 Title: Obtaining the sphaleron field configurations with gradient flow Author: Yu Hamada, Kengo Kikuchi arXiv: http://arxiv.org/abs/2003.02070v2 Title: The Cayley transform in complex, real and graded K-theory Author: Chris Bourne, Johannes Kellendonk, Adam Rennie arXiv: http://arxiv.org/abs/1912.07158v2 Title: Janus interface entropy and Calabi's diastasis in four-dimensional N=2 superconformal field theories Author: Kanato Goto, Lento Nagano, Tatsuma Nishioka, Takuya Okuda arXiv: http://arxiv.org/abs/2005.10833v1 Title: Low-Dimensional Fluctuations and Pseudogap in Gaudin-Yang Fermi Gases Author: Hiroyuki Tajima, Shoichiro Tsutsui, Takahiro M. Doi arXiv: http://arxiv.org/abs/2005.12124v1 Title: Topologies on schemes and modulus pairs Author: Bruno Kahn, Hiroyasu Miyazaki arXiv: http://arxiv.org/abs/1910.14595v2 Title: Goldstino spectrum in an ultracold Bose-Fermi mixture with explicitly broken supersymmetry Author: Hiroyuki Tajima, Yoshimasa Hidaka, Daisuke Satow arXiv: http://arxiv.org/abs/2001.08507v2
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2020-05-25
セミナーレポート
QFT-core Seminar “Gradient Flow Equation and Its Applications” on May 15, 2020
The QFT-core seminar series has been started from this fiscal year. The seminar series is hold under the theme of the Quantum Field Theory including elementary particle theory, nuclear theory and Condensed Matter physics. The First seminar in the series was given by Dr.Kengo Kikuchi from the Riken iTHEMS on May 15. The title is “Gradient Flow Equation and Its Applications”. The gradient flow is the one of the methods to suppress the ultraviolet divergence in gauge theories. The any correlation functions in terms of the flowed field, which is defined by the gradient flow equation, are finite without additional renormalizations. Because of this surprising property, the methods has been studied widely, especially in the lattice field theory. In this seminar, he introduce what the gradient flow is briefly, and show his work, “generalized gradient flow equation”, which is the gradient flow equation for field theories with nonlinearly realized symmetry. Applying the formalism to a supersymmetric theory and O(N) non linear sigma model, the SUSY gradient flow and the Large N gradient flow are obtained. He also refer to the current research, the gradient flow of the supersymmetric theory with the non-renormalization theorem and the new formalism to obtain the sphalerons, which is one of the static classical solutions, using gradient flow methods. The seminar was hold via Zoom. There were about 20 participants from iTHEMS and other university. The participants enjoyed meaningful discussions through the seminar.
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2020-05-21
今週の論文Week 4 of May
Title: Test of Eigenstate Thermalization Hypothesis Based on Local Random Matrix Theory Author: Shoki Sugimoto, Ryusuke Hamazaki, Masahito Ueda arXiv: http://arxiv.org/abs/2005.06379v1 Title: Black Hole as a Quantum Field Configuration Author: Hikaru Kawai, Yuki Yokokura arXiv: http://arxiv.org/abs/2002.10331v3 Title: F_K / F_π from Möbius Domain-Wall fermions solved on gradient-flowed HISQ ensembles Author: Nolan Miller, Henry Monge-Camacho, Chia Cheng Chang, Ben Hörz, Enrico Rinaldi, Dean Howarth, Evan Berkowitz, David A. Brantley, Arjun Singh Gambhir, Christopher Körber, Christopher J. Monahan, M. A. Clark, Bálint Joó, Thorsten Kurth, Amy Nicholson, Kostas Orginos, Pavlos Vranas, André Walker-Loud arXiv: http://arxiv.org/abs/2005.04795v2
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2020-05-20
セミナーレポート
First virtual Math Seminar on May 1, 2020
The first iTHEMS Math seminar of this academic year was held on May 1st on Zoom, inviting our colleague Keita Mikami. The title of the talk was “From Eigenvalues to Resonances”. The main topic was Resonance, which is one of the most studied objects in mathematical study of Schrödinger operators. In the first part, the speaker briefly reviewed spectral theory and how we use it in the study of Schrödinger operators, introducing some basic notions used in the study of Schrödinger operators. Especially, he explained that spectra can be classified into eigenvalues and continuous spectra. Then he introduced scattering theory, which can be used to analyze absolutely continuous spectra. One novelty is that generalized eigenfunction has a representation formula in terms of scattering matrices. In the second part, the speaker gave a brief introduction of resonances and its application to both mathematicians and researchers in other fields. After introducing mathematical definition of resonances, he explained its applications in the other fields. One example was the following experimental result; when one makes a wave with certain frequency in aquarium, there appears special pattern in the distribution of speed. This phenomena can be explained mathematically by considering resonance of pseudodifferential operator on torus.
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2020-05-18
リサーチニュース
Mesoscopic spin transport between strongly interacting Fermi gases
Understanding of physical properties for quantum many-body systems with strong interparticle interactions is one of key issues common to various subfields of physics. Such systems range from high-Tc superconductors in solid-state physics to neutron star interiors in nuclear physics. Among these systems, ultracold atoms are very pure atomic gases whose interactions can be tuned by optical and/or magnetic fields. The ultracold atoms thus provide an ideal platform to simulate the strongly interacting systems. Recently, quantum transport of ultracold atoms have been actively investigated in order to clarify how strong interactions affect their nonequilibrium properties. Motivated by this experimental situation, we theoretically study spin transport for strongly interacting Fermi gases in two-terminal setup where the gases in left and right reservoirs are connected via a narrow construction (see Figure). In particular, the spin current for normal Fermi gases in two situations are focused on. The first situation is the pseudogap region, where both gases have small spin polarizations and are above the superfluid transition temperature. In this case, spin-up and spin-down fermions in each reservoir prefer to form pairs (so-called preformed Cooper pairs) due to the strong attractive interaction. Because of this pairing effect, the spin degrees of freedom tend to be frozen and thus the spin current is largely suppressed. The other situation is a region where the gases in the left and right reservoirs have large spin polarizations with opposite sign. In this case, minority-spin particles behave as the “Fermi polarons,” which are quasiparticles consisting of minority-spin particles dressed by majority-spin ones. The appearance of the Fermi polarons results in the increase of the minority densities of states, leading to the enhancement of the spin current. Our results suggest that the spin transport measurement becomes a sensitive probe to experimentally examine pseudogap and polaron phenomena, which have attracted much attention not only in atomic physics but also in solid-state physics.
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2020-05-15
セミナーレポート
Math Seminar by Dr. Yukimi Goto
Math seminar titled "How many electrons can atoms bind?" by Dr. Yukimi Goto was hold on 13 May. In the first part, the speaker started the talk by introducing many body Hamiltonian and Pauli principle. She then introduced the ionization conjecture. She also introduced some known results concerning about this conjecture. In the second part, the speaker introduced approximation methods and its relation to the ionization conjecture. She first introduced Thomas-Fermi theory and see TF functional appears as a leading term of grand state energy for large atom. She introduced Hartree-Fock theory next. She mentioned a variant of the ionization conjecture for HF theory was proven by Solovej, but original conjecture is still open. She then explained HF theory can be regarded as good approximation in terms of volume.
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2020-05-14
今週の論文Week 3 of May
Title: Cosmological Evolution of Flat-Spectrum Radio Quasars based on the {\it Swift}/BAT 105-month Catalog and Their Contribution to the Cosmic MeV Gamma-ray Background Radiation Author: Koyo Toda, Yasushi Fukazawa, Yoshiyuki Inoue arXiv: http://arxiv.org/abs/2005.02648v1 Title: Vector Fields and Paul Klee -- A Summer School Course for gifted High-School Students Author: Martin Skrodzki, Henriette Lipschütz arXiv: http://arxiv.org/abs/2005.01983v2 Title: Family-Vicsek Scaling of Roughness Growth in a Strongly Interacting Bose Gas Author: Kazuya Fujimoto, Ryusuke Hamazaki, Yuki Kawaguchi arXiv: http://arxiv.org/abs/1911.10707v2 Title: Partial Deconfinement at Strong Coupling on the Lattice Author: Hiromasa Watanabe, Georg Bergner, Norbert Bodendorfer, Shotaro Shiba Funai, Masanori Hanada, Enrico Rinaldi, Andreas Schäfer, Pavlos Vranas arXiv: http://arxiv.org/abs/2005.04103v1 Title: Firewall From Effective Field Theory Author: Pei-Ming Ho, Yuki Yokokura arXiv: http://arxiv.org/abs/2004.04956v2 Title: Link-homotopy classes of 4-component links and claspers Author: Yuka Kotorii, Atsuhiko Mizusawa arXiv: http://arxiv.org/abs/1910.08653v4 Title: F_K / F_π from Möbius Domain-Wall fermions solved on gradient-flowed HISQ ensembles Author: Nolan Miller, Henry Monge-Camacho, Chia Cheng Chang, Ben Hörz, Enrico Rinaldi, Dean Howarth, Evan Berkowitz, David A. Brantley, Arjun Singh Gambhir, Christopher Körber, Christopher J. Monahan, M. A. Clark, Bálint Joó, Thorsten Kurth, Amy Nicholson, Kostas Orginos, Pavlos Vranas, André Walker-Loud arXiv: http://arxiv.org/abs/2005.04795v1
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2020-05-13
セミナーレポート
Biology Seminar by Dr. Catherine Beauchemin on May 13, 2020
Catherine talked about her general approach for formalizing and quantifying the principle of virological dynamics, namely “virophysics.” She first presented compartmental models to generalize the probability distribution of sojourn time of cells being infective, with parameter estimation in flu data using MCMC, and then talked about COVID-19 modeling and its predictability. I was honestly surprised that increasing the number of compartments can readily change the distribution, and found it promising to apply her approach to not only virology but ecology and evolution as well. Thank you, Catherine, for the great talk! - Ryosuke Iritani
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2020-05-12
セミナーレポート
Totani’s Equation: Abiogenesis probability in an inflationary universe
Abiogenesis is the natural process by which life has arisen from non-living matter. Understanding of abiogenesis can tell us one of the most fundamental questions in natural science: “Why are we here?”. However, abiogenesis probability is believed very very low to have us, life, in the universe considering the formation of a long enough polymer having a correct nucleotide sequence by random reactions. Sometimes, this probability is quoted as “Can a monkey hitting a keyboard at random type a complete work of Shakespeare?”. On 11 May 2020, we had iTHEMS Colloquium inviting Prof. Tomonori Totani from the University of Tokyo, with the title of “Emergence of life in an inflationary universe.” Prof. Totani is a renowned professor in astrophysics working on high energy astrophysics and cosmology. As a cosmologist, he visited this abiogenesis issue. Cosmologists believe that the universe created by inflation should extend far beyond the observable universe (13.8 billion light-year radius). Combining the knowledge of this inflationary universe and the RNA formation processes, he provided a new equation describing the abiogenesis probability in an inflationary universe. This new equation showed that, as the inflationary universe contains a large number of stars, it may provide sufficiently many abiogenesis events, even if we consider only the basic random polymerization. However, following his equation, regrettably, we may expect no “aliens” in our universe. Let’s see the results of future telescopes’ search of a second Earth.
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2020-05-08
セミナーレポート
Third virtual Biology Seminar on May 7, 2020
On 7 May, Dr. Tomohiko Sano, from École polytechnique fédérale de Lausanne in Switzerland, gave a talk at the 3rd iTHEMS Biology Seminar. In this seminar, Dr. Sano talked about the results of his research on how physical actions in knots occur. It has been empirically known that hitch knots and other knots cannot be untied, but how they work has not been well understood. Dr. Sano explained that he had clarified them through experiments and simulations. Since there are various knots in the three-dimensional structures of DNA and proteins in cells, We felt that Dr. Sano's research could be applied to various structural problems in molecular biology.
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2020-05-07
今週の論文Week 1 & 2 of May
Title: How the deprecation of Java applets affected online visualization frameworks -- a case study Author: Martin Skrodzki arXiv: http://arxiv.org/abs/2004.13254v2 Title: Universal Error Bound for Constrained Quantum Dynamics Author: Zongping Gong, Nobuyuki Yoshioka, Naoyuki Shibata, Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2001.03419v4 Title: Error bounds for constrained dynamics in gapped quantum systems: Rigorous results and generalizations Author: Zongping Gong, Nobuyuki Yoshioka, Naoyuki Shibata, Ryusuke Hamazaki arXiv: http://arxiv.org/abs/2001.03421v4 Title: Liouvillian Skin Effect: Slowing Down of Relaxation Processes without Gap Closing Author: Taiki Haga, Masaya Nakagawa, Ryusuke Hamazaki, Masahito Ueda arXiv: http://arxiv.org/abs/2005.00824v1 Title: Variational Shape Approximation of Point Set Surfaces Author: Martin Skrodzki, Eric Zimmermann, Konrad Polthier arXiv: http://arxiv.org/abs/2005.01003v1 Title: Vector Fields and Paul Klee -- A Summer School Course for gifted High-School Students Author: Martin Skrodzki, Henriette Lipschütz arXiv: http://arxiv.org/abs/2005.01983v1
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2020-05-07
セミナーレポート
Second iTHEMS Biology Seminar on April 30, 2020
On 30 April, Euki Yazaki, who joined iTHEMS in April, gave a talk at the second iTHEMS Biology Seminar. Euki's main research motivation is to understand the diversity and evolution of eukaryotes, especially by focusing on microorganisms called "protists". Most of you probably know nothing about protists. In fact, protist is not a proper phylogenetic group. It is "any eukaryotic organism that is not an animal, plant, or fungus" (from Wikipedia) - i.e. a category to dump all the eukaryotes that most people don't know about and don't care about. Yet, as Euki illustrated, they make up most of the phylogenetic diversity of eukaryotes, and there are still many many species that haven't been discovered. He described his previous research where he isolated an unknown protist from Palau which was different from any other protist that had been discovered, and determined its phylogenetic placement by large-scale DNA sequence data analyses. Euki and I believe that protists hold the key to understanding the origin of eukaryotes and to uncover some new exciting biology. Euki's talk also sparked interest from non-biologists to learn more about phylogenetics, a topic that involves lots of mathematics, which will hopefully be the topic of a seminar in the near future. - Jeffrey Fawcett
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2020-04-30
今週の論文Week 5 of April
Title: Resummation for the Field-theoretical Derivation of the Negative Magnetoresistance Author: Kenji Fukushima, Yoshimasa Hidaka arXiv: http://arxiv.org/abs/1906.02683v2 Title: The Gromov-Lawson codimension 2 obstruction to positive scalar curvature and the C*-index Author: Yosuke Kubota, Thomas Schick arXiv: http://arxiv.org/abs/1909.09584v2 Title: An Analytic Description of Semi-Classical Black-Hole Geometry Author: Pei-Ming Ho, Yoshinori Matsuo, Yuki Yokokura arXiv: http://arxiv.org/abs/1912.12855v3 Title: Partial wave decomposition on the lattice and its applications to the HAL QCD method Author: Takaya Miyamoto, Yutaro Akahoshi, Sinya Aoki, Tatsumi Aoyama, Takumi Doi, Shinya Gongyo, Kenji Sasaki arXiv: http://arxiv.org/abs/1906.01987v2 Title: How the deprecation of Java applets affected online visualization frameworks -- a case study Author: Martin Skrodzki arXiv: http://arxiv.org/abs/2004.13254v1
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2020-04-30
セミナーレポート
Nerd Night Tokyo: public talk by Don Warren
At Nerd Night Tokyo on April 22, Don Warren gave a public talk on "First stars". You can watch his superb lecture from YouTube. Enjoy!
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2020-04-30
セミナーレポート
Frontier Science Lecture by iTHEMS Researchers
Frontier Science Lecture by iTHEMS Researchers for undergraduate students in Univ. of Tokyo was started on April 22, 2020. This year, Yoshiyuki Inoue gave an online lecture on "the History of the Universe looking through the Black Holes". He started the lecture from ancient views of the Universe including the old Japanese tale that the Universe began from the Chaos. Then he moved on to the modern view of the Universe and Matter based on the theory of general relativity and also quantum mechanics. After explaining recent observations of the black holes, he ended his lecture by saying that we are now entering the era of black hole astronomy. On April 29 (although it was a national holiday), Yoshiyuki's lecture was followed by Yoshimasa Hidaka's lecture on "the Origin of Matter". His second lecture will be held on May 13. Frontier Science Lectures in 2018 and 2019 can be checked from the web site below. The 2018 lecture will be published from the Univ. of Tokyo Press in the summer of 2020.
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2020-04-28
セミナーレポート
Searching the signature of the ultra-light axions using gravitational waves
As the first activity of the DM working group in the academic 2020, we have held an online seminar inviting Dr. Sylvia Zhu from DESY. She has introduced her recent work about the axion search using the continuous gravitational waves, which is a new connection between the particle and the gravitational-wave physics. Axions and axion-like particles are good candidates for dark matter, which could simultaneously solve the strong CP problem. When such particles exist around spinning black holes (BHs), they can extract the angular momentum of the BH through the so-called superradiance. In this mechanism, the amplitude of the axion oscillation increases because the wave is scattered off by the rotating BH. Especially for the case of the axion/axion-like particle, this scattering leads to the multiple particle production hence they form a cloud-like structure around the BH, which resembles the electron cloud of the atom. Such a BH-axion cloud object can be the source of the continuous gravitational wave since axions in the cloud are converted to gravitons when they pair-annihilate. The detection of the continuous gravitational wave is really difficult. The key quantities for the detectability are the strength of the gravitational wave and the duration. In addition, the cloud-formation condition has to be satisfied. The larger the mass of the axion as well as the BH is better to form such systems. Also, the strength of the gravitational wave increases along with the mass of the system and the spin of the central BH. On the other hand, the decaying timescale of the gravitational wave emission becomes shorter for heavier systems hence there is a competition between these effects. Combining the mass and spin distribution of the BHs in our Galaxy, we could expect about 100-1000 continuous gravitational-wave signals generated in the axion clouds. We can probe the axion/axion-like particle of which mass is 0.1-1 pico-eV using this method. The sensitivity with the LIGO-Virgo facilities peaks at ~0.5 pico-eV. We could see the signatures of the new physics and/or the hint of dark matter by conducting intensive analyses.
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2020-04-23
セミナーレポート
First virtual Biology Seminar on April 22, 2020
Though this fiscal year started with the confusion for COVID-19, we launched virtual, iTHEMS Biology Seminar. As the first speaker of the seminar series, Asher Leeks, who is appointed with the University of Oxford and visiting Japan as IPA student, gave a talk on his own work on virus-virus interactions. Viruses may disperse (or move) between cells in a group, forming a “collective infectious unit” (CIU). If viruses can interact positively (i.e., larger CIUs enable faster replication), then CIU, albeit physiologically costly, is likely to be favored by natural selection (i.e., evolutionarily advantageous), with the result that fewer but bigger CIUs may emerge. With negative interactions, in contrast, natural selection favors smaller CIUs/no CIUs at all. This is so because, under negative interactions, forming groups would not pay. These contrasting results, therefore, suggest that understanding viral interactions may be of pivotal importance, with potential implications for clinics. He then explained genomic data for comparison and finally talked about our current collaboration project at iTHEMS. Since more and more people are now interested in virology, his new theory may give insight into a wide range of fields, and we learned a lot about what is going on within patients' bodies. Thanks for the excellent talk, Asher! -Ryosuke Iritani (iTHEMS, Research Scientist)
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2020-04-23
今週の論文Week 4 of April
Title: Nonadiabatic Control of Geometric Pumping Author: Kazutaka Takahashi, Keisuke Fujii, Yuki Hino, Hisao Hayakawa arXiv: http://arxiv.org/abs/1909.02202v2 Title: EspressoDB: A scientific database for managing high-performance computing workflow Author: Chia Cheng Chang, Christopher Körber, André Walker-Loud arXiv: http://arxiv.org/abs/1912.03580v2 Title: Nisnevich topology with modulus Author: Hiroyasu Miyazaki arXiv: http://arxiv.org/abs/1910.14579v3 Title: Dimension dependence of numerical simulations on gravitational waves from protoneutron stars Author: Hajime Sotani, Tomoya Takiwaki arXiv: http://arxiv.org/abs/2004.09871v1
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2020-04-21
ホットトピック
iTHEMS x academist Online open to the public "Mathematical science world" on April 18, 2020
The open house for RIKEN was scheduled on April 18th, but it was cancelled due to the COVID-19 situation. But that did not stop Dr. Yokokura and the other lecturers, Dr. Iritani, Dr. Irie, Dr. Hiroshima, Dr. Miyazaki and Dr. Tanaka. In defiance of the difficulties, they gave the same public lecture on-line with the help by Academist. Dr. Yokokura and other lecturers worked very hard preparing the event; their effort was rewarded by the spectacular success, with as many as over 900 viewers. Some of the positive response can be seen on Twitter.
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2020-04-20
今週の注目論文
Paper: Black Hole as a Quantum Field Configuration
What's going on inside black holes? The observations to date have taught us the nature of black holes outside and around it, but it does not tell us anything about the inside yet. This is because black holes are "almost" black: gravity is so strong that physical signals from the inside "almost" never come out. So, how can we search for the interior of black holes? It is necessary to return to the basic principles of physics and reconsider what a black hole is. In this paper, we succeeded in describing the inside of black holes based on general relativity and quantum mechanics (quantum field theory). What is important here is a fact that black holes evaporate: According to quantum mechanics, black holes emit weak light, slowly lose energy, and eventually evaporate (Hawking radiation). By taking in this effect from the beginning and analyzing the collapsing process of stars, we obtained the following result: The black hole is a compact object with a surface (instead of horizon) that looks like a conventional black hole from the outside and eventually evaporates without a singularity. (See figure.) Indeed, we explained why this picture can be achieved in quantum field theory. In addition, we investigated how much information is contained inside and showed that the amount (entropy) is given by the surface area. We also described how the energy decreases. This work provides the first field-theoretical formulation of the black hole, and I think it will be the basis for investigating how the information that enters the black hole will go out.
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2020-04-16
今週の論文Week 3 of April
Title: Hybrid Quantum Annealing via Molecular Dynamics Author: Hirotaka Irie, Haozhao Liang, Takumi Doi, Shinya Gongyo, Tetsuo Hatsuda arXiv: http://arxiv.org/abs/2004.03972v1 Title: Firewall From Effective Field Theory Author: Pei-Ming Ho, Yuki Yokokura arXiv: http://arxiv.org/abs/2004.04956v1
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2020-04-14
今週の注目人物
Self-introduction: Kengo Kikuchi
I’m Kengo Kikuchi, a special postdoctoral researcher in iTHEMS. I’m studying the theoretical physics, elementally particle physics and quantum field theory, especially, gradient flow equation. I’d like to take the opportunity working in iTHEMS to broaden research fields, and it would lead to the new interaction with various study regions.
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2020-04-13
今週の注目人物
Self-introduction: Naomi Tsuji
I am Naomi Tsuji, a postdoctoral researcher at RIKEN/iTHEMS. My major is observational studies of high energy astrophysical phenomena. I have been working on particle acceleration and nonthermal radiation in shock waves of supernova remnants by using X-ray observations. I also analyze TeV gamma-ray data, as a member of H.E.S.S. (High Energy Spectroscopic System) collaboration.
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2020-04-13
今週の注目人物
Self-introduction: Hui Tong
My name is Hui Tong, a PhD student from School of Physics, Peking University. My main research topic is nuclear theory, including the interactions between nucleons and using the ab-initio nuclear many-body theory to study nuclear matter and neutron star. Now I am studying on how to extract hadron interactions from lattice QCD calculations. In the iTHEMS, I hope to learn more about theoretical, mathematical and computational sciences, this will be a great opportunity to broaden my horizons.
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2020-04-09
今週の注目人物
Self-introduction: Yukimi Goto
I am Yukimi Goto, a special postdoctoral researcher of iTHEMS. I have been interested in the mathematical study of physical models. For example, I have investigated the following question in my research: How many electrons can an atom bind? This is a fascinating open problem in mathematical physics. Intuitively, this question is related to the size of the system, e.g., the question: Why are the radii of atoms more or less independent of their nuclear charge? Although one might think these are simple consequences of electrostatics alone, the Pauli exclusion principle plays an essential role. My hope is to understand physics. However, to be honest, I’m not a physicist but an applied mathematician. So, I’m happy if you tell me physics.
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2020-04-09
今週の論文Week 1 & 2 of April
Title: Nisnevich topology with modulus Author: Hiroyasu Miyazaki arXiv: http://arxiv.org/abs/1910.14579v2 Title: Categorical polynomial entropy Author: Yu-Wei Fan, Lie Fu, Genki Ouchi arXiv: http://arxiv.org/abs/2003.14224v1 Title: ΛΛ and NΞ interactions from Lattice QCD near the physical point Author: Kenji Sasaki, Sinya Aoki, Takumi Doi, Shinya Gongyo, Tetsuo Hatsuda, Yoichi Ikeda, Takashi Inoue, Takumi Iritani, Noriyoshi Ishii, Keiko Murano, Takaya Miyamoto arXiv: http://arxiv.org/abs/1912.08630v2 Title: MeV-scale reheating temperature and cosmological production of light sterile neutrinos Author: Takuya Hasegawa, Nagisa Hiroshima, Kazunori Kohri, Rasmus S. L. Hansen, Thomas Tram, Steen Hannestad arXiv: http://arxiv.org/abs/2003.13302v1 Title: The HAL QCD potential in I=1 ππ system with the ρ meson bound state Author: Yutaro Akahoshi, Sinya Aoki, Tatsumi Aoyama, Takumi Doi, Takaya Miyamoto, Kenji Sasaki arXiv: http://arxiv.org/abs/2004.01356v1 Title: The KO-valued spectral flow for skew-adjoint Fredholm operators Author: Chris Bourne, Alan L. Carey, Matthias Lesch, Adam Rennie arXiv: http://arxiv.org/abs/1907.04981v2 Title: Analysis for Lorentzian conformal field theories through sine-square deformation Author: Xun Liu, Tsukasa Tada arXiv: http://arxiv.org/abs/2004.01930v1 Title: Semi-Dirac transport and anisotropic localization in polariton honeycomb lattices Author: B. Real, O. Jamadi, M. Milićević, N. Perent, P. St-Jean, T. Ozawa, G. Montambaux, I. Sagnes, A. Lemaître, L. Le Gratiet, A. Harouri, S. Ravets, J. Bloch, A. Amo arXiv: https://arxiv.org/abs/2004.03478
187件のニュース / 2020年