Application of Modular tensor category to Lattice gauge theory

December 29 (Fri) at 10:30 - 16:00, 2023

Tomoya Hayata (Assistant Professor, Faculty of Economics, Keio University)

Inspired by the recent development in quantum computers, much efforts have been devoted to exploring their potential applications in lattice gauge theories. However, in contrast to condensed matter systems, we face many challenges in applications of quantum computations to lattice gauge theories, where one of the major obstructions lies in implementation of gauge symmetries in quantum computations. In this seminar, I talk about a possible solution to the problem based on a unitary modular tensor category, expressing the Hamiltonian of lattice gauge theories in terms of the so called F moves, and implementing the F moves on quantum computers. References: TH, Y. Hidaka, JHEP 09 (2023) 126; JHEP 09 (2023) 123.

Venue: Seminar Room #359

Event Official Language: English

Introduction to Effective Field Theory and Many-Body Problems

December 27 (Wed) - 28 (Thu), 2023

Masaru Hongo (Assistant Professor, Department of Physics, Faculty of Science, Niigata University)

Quantum field theory (QFT) has been formulated as a theoretical tool to describe elementary particles and nuclei. However, after introducing the concept of "effective field theory," QFT has been providing a general and powerful theoretical framework for describing various universal phenomena in broader range of physical systems, including condensed matter physics and statistical physics. In this lecture, we will explore the basic aspects of field theory by employing it to address quantum many-body problems in simple nonrelativistic systems. The topics covered will include: Lecture 1: Low-energy scattering and renormalization in quantum mechanics Lecture 2: Effective field theory of low-energy scattering Lecture 3: Spontaneous symmetry breaking in weakly-interacting bose gas Lecture 4: Effective field theory of superfluid Lecture 5: Introduction to in-medium potential Lecture 6: Complex-valued in-medium potential between heavy impurities in ultracold atoms The aim is to provide an introductory overview and explanation of basics concepts in field theory. Schedule: Wed., Dec. 27 10:00 - 11:30: Lecture 1 13:00 - 14:30: Lecture 2 15:00 - 16:30: Lecture 3 Thur., Dec. 28 10:00 - 11:30: Lecture 4 13:00 - 14:30: Lecture 5 15:00 - 16:30: Lecture 6

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Oscillatory data analysis using the extended Hilbert transform method

December 26 (Tue) at 16:00 - 17:00, 2023

Akari Matsuki (Postdoctoral Researcher, Department of Advanced Transdisciplinary Sciences, Hokkaido University)

Oscillatory phenomena are observed in various biological systems, such as spinal nervous systems and circadian rhythms. These macroscopic oscillatory phenomena appear as a result of synchronization of microscopic oscillators, such as pacemaker cells. The first step in the analysis of synchronization is to reconstruct the "phase" from the observed signal. The Hilbert transform method is one of the popular methods for phase reconstruction, but it is known that it can only accurately reconstruct the phase from a limited class of signals such as narrowband signals. In this study, we show that the Hilbert transform method has a low-pass filter-like effect on the phase modulation and propose an "extended Hilbert transform method" that can be applied to a wider class of signals. In this talk, I will introduce the extended Hilbert transform method, and its application to phase shift detection and coupling network inference.

Venue: via Zoom

Event Official Language: English

Rapid development of cold-atom quantum computers and their prospect

December 26 (Tue) at 13:30 - 17:00, 2023

Takafumi Tomita (Assistant Professor, Photo-Molecular Science, Institute for Molecular Science)

Note for participants: For on-site participants, please register via the registration form. For online participants finding the Zoom link, you can get it after filling the registration form. Program: 13:30-15:00 Lecture 1 15:00-15:30 Coffee break 15:30-17:00 Lecture 2 Abstract: In this talk, I will give an overview of the recent rapid progress of cold-atom quantum computers. In a cold-atom quantum computer, a laser-cooled atomic gas in a vacuum chamber is captured with a two-dimensional trap array called an optical tweezers array, which is an array of tightly focused laser beams. An array of cold single atoms thus created is initialized, gate operated, and readout with other laser beams. Because of its controllability and scalability, the cold-atom quantum computer has been attracting much attention, as one of the most promising candidates in the race to develop quantum-computer hardware. I will describe the characteristics and development trends of the cold-atom hardware, as well as the development of a cold-atom quantum computer at Institute for Molecular Science including the realization of an ultrafast quantum gate using ultrashort laser pulses.

Venue: #435-437, 4F, Main Research Building (Main Venue) / via Zoom

Event Official Language: English

A symmetry principle for gauge theories with fractons

December 22 (Fri) at 17:00 - 18:15, 2023

Yuji Hirono (Program-Specific Associate Professor, Department of Physics, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

Fractonic phases are emergent quantum phases of matter that host excitations with restricted mobility. Although these phases have been considered to be of “beyond Landau” order, we show that a certain class of gapless fractonic phases are realized as a result of spontaneous breaking of generalized symmetries. The corresponding symmetries are continuous higher-form symmetries whose conserved charges do not commute with spatial translations, and we refer to them as nonuniform higher-form symmetries. For a given set of nonuniform symmetries, the effective theory associated with the spontaneous breaking of them can be constructed. At low energies, the theories reduce to known higher-rank gauge theories such as scalar/vector charge gauge theories, and the gapless excitations in these theories are interpreted as Nambu–Goldstone modes for higher-form symmetries. Due to the nonuniformity of the symmetry, some of the modes acquire a gap, which is the higher-form analogue of the inverse Higgs mechanism of spacetime symmetries. In this formulation, the mobility restrictions are fully determined by the choice of the commutation relations of charges with translations. This approach allows us to view existing (gapless) fracton models such as the scalar/vector charge gauge theories and their variants from a unified perspective and enables us to engineer theories with desired mobility restrictions. Field: condensed matter physics Keywords: fractonic phases, higher-form symmetries, Nambu-Goldstone modes, Higgs mechanism, gauge theories

Venue: via Zoom

Event Official Language: English

Inflationary Cosmology with a scalar-curvature mixing term $\frac{1}{2} \xi R \phi^2$

December 20 (Wed) at 16:00 - 17:30, 2023

Payel Sarkar (Visiting Researcher, Kyoto University)

We use the PLANCK 2018 and the WMAP data to constraint inflation models driven by a scalar field $\phi$ in the presence of the non-minimal scalar-curvature mixing term $\frac{1}{2}\xi R \phi^2$. We consider four distinct scalar field potentials $\phi^p e^{-\lambda\phi},~(1 - \phi^{p})e^{-\lambda\phi},~(1-\lambda\phi)^p$ and $\frac{\alpha\phi^2}{1+\alpha\phi^2}$ to study inflation in the non-minimal gravity theory. We calculate the potential slow-roll parameters, predict the scalar spectral index $n_s$, tensor-to-scalar ratio $r$, leading and higher order non-Gaussianity parameters ($f_{NL},~\tau_{NL}$ and $g_{NL}$) and the amplitude of the scalar spectrum $A_s$ in the parameter ($\lambda, p, \alpha$) space of the potentials corresponding to different values of the non-minimal coupling parameter $\xi$. We have compared our results with the ones existing in the literature, and this indicates the present status of non-minimal inflation after the release of the PLANCK 2018 data.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building (Main Venue) / via Zoom

Event Official Language: English

Application of mathematical models to the COVID-19 cohort study

December 19 (Tue) at 16:00 - 17:00, 2023

Takara Nishiyama (Ph.D. Student, Graduate School of Science, Nagoya University)

The COVID-19 pandemic, which began in 2019, has caused widespread morbidity and mortality across the globe. In response, a multitude of studies focusing on SARS-CoV-2 have been undertaken. Among these, cohort studies have been particularly significant. These studies, as a key observational research method, play a crucial role in exploring the links between various factors and the onset of diseases, offering valuable insights for disease control. Mathematical model, applied within these studies, provide essential quantitative data. In my talk, I will introduce how mathematical models are instrumental in cohort studies, drawing on two of my own COVID-19 cohort studies as examples.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Energy spectrum and time evolution of a SU(2) pure gauge lattice theory on a quantum annealer

December 18 (Mon) at 14:00 - 15:00, 2023

Emanuele Mendicelli (Postdoctoral Research Associate, Department of Mathematical Sciences, University of Liverpool, UK)

Lattice gauge theory is an indispensable tool for non-Abelian fields, such as those in quantum chromodynamics where lattice results have been of central importance for several decades. Recent studies suggest that quantum hardware could extend the reach of lattice gauge theory to inaccessible phenomena due to the need for an exponentially large amount of resources, the so-called sign problem. Among the available quantum hardware gate-based quantum computer are well know but less common quantum annealer can play a role too. In this talk we briefly report one of the first use of D-Wave quantum annealer to study the energy spectrum and the time evolution of a SU(2) pure gauge lattice theory in its Hamiltonian formulation. In particular we present how to extract the energy spectrum using the quantum Quantum Annealer Eigensolver algorithm and perform the time evolution using the Kitaev-Feynman clock states. Despite the nosy hardware, no error mitigation techniques were needed but the usability of the D-Wave hardware was extended by simply block-diagonalizing the Hamiltonian.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Plasticity in the endogenous rhythms and the adaptation to the tidal environment in a freshwater snail

December 14 (Thu) at 16:00 - 17:00, 2023

Takumi Yokomizo (JSPS Research Fellow PD, Graduate School of Science, Chiba University)

Organisms have diverse biological clocks synchronized with environmental cycles　depending on their habitats. The change in endogenous rhythms could contribute to range expansion in a novel rhythmic environment. For example, the Anticipation of tidal changes has driven the evolution of circatidal rhythms in some marine species. I am interested in the genetic and non-genetic changes in the biological rhythms and adaptation to tidal environments in the freshwater snail, Semisulcospira reiniana. Chronobiological analyses of behavior and gene expression revealed that snails had habitat-specific endogenous rhythms: individuals in a nontidal population showed the circadian rhythm while those in a tidal population showed the circadian and circatidal rhythms. The entrainment to the simulated tidal cycles increased the strength of circatidal activity only in snails in a tidal population. Although the circatidal rhythms in the transcriptome were clearer in individuals entrained to tidal cycles, the number of circatidal rhythmic transcripts was greater in a tidal population than in a nontidal population. These results suggest biological rhythms in the snails plastically change at the molecular level, but the strength of circatidal rhythm is different between populations. Finally, transcriptome-wide population genetic analysis revealed that these two populations can be clearly distinguished genetically, though the genetic distance was very small. Thus, genetic differentiation in biological rhythms could result from the evolution of a small number of genes. These findings suggest that adaptive plasticity and genetic changes in the biological rhythms play an important role in coping with tidal environments.

Venue: via Zoom

Event Official Language: English

Tropical geometry and period integrals

December 13 (Wed) at 14:00 - 16:30, 2023

Yuto Yamamoto (Special Postdoctoral Researcher, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))

Tropical geometry is a field of mathematics that naturally emerges when considering the limits of spaces with respect to some parameters. One of the motivations to study tropical geometry is to describe the behaviors of the spaces under the limit. In this math seminar, starting with a brief introduction to tropical geometry, we discuss its application to computation of period integrals, which are one of the most fundamental quantities of complex manifolds. The goal is to compute asymtptotics of period integrals for complex hypersurfaces in toric varieties using tropical geometry, and observe that the Riemann zeta values (or the gamma classes) appear in the result of the computation. The first half of the talk will be a brief introduction to tropical geometry for non-experts including those who are working outside mathematics, and everyone will be welcome.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Transforming Industries and Society: The Power of Advanced Math and AI Technologies

December 12 (Tue) at 16:30 - 18:00, 2023

Hirokazu Anai (Principal Research Director, FUJITSU RESEARCH, FUJITSU Ltd.)

In this talk, we will review the history and the latest trends in artificial intelligence (AI) and mathematical technologies in recent years. We will also introduce various real-world problem-solving efforts that utilize state-of-the-art mathematics and artificial intelligence technology. Additionally, we will explore the role of mathematical and AI technologies and the social value they bring, while providing examples of their applications in a wide range of fields, such as manufacturing, disaster prevention, medical care, and institutional design in society. Furthermore, we will consider the thinking and skills required to address industrial and social issues using mathematical and AI technologies. The technologies that will be discussed in this talk include the following keywords: mathematical modeling, simulation, optimization, deep learning, topological data analysis, causal discovery, game theory, matching theory, and social mathematics.

Venue: Okochi Hall (Main Venue) / via Zoom

Event Official Language: English

Exploring material strengths of dust aggregates in planet formation by numerical simulations

December 8 (Fri) at 14:00 - 15:15, 2023

Misako Tatsuuma (Research Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))

The planet formation process is the growth from sub-micrometer-sized cosmic dust grains to thousand-kilometer-sized planets. This growth process has broadly two phases: the growth from dust grains to kilometer-sized planetesimals, mainly driven by intermolecular forces like van der Waals forces and hydrogen bonds, and the subsequent growth from planetesimals to planets, governed by gravitational forces. However, the planetesimal formation process encounters various challenges, including fragmentation and bouncing resulting from collisions among dust aggregates. To gain insights into the planetesimal formation process and how to avoid these obstacles, I have been focused on measuring and formulating the material strengths of dust aggregates using grain simulations. In this talk, I will introduce my works on the material strengths of dust aggregates and their applications to kilometer-sized bodies in the solar system, such as comets and asteroids.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Gravitational Lensing in Black Hole Spacetimes of the Plebanski-Demianski Class

December 6 (Wed) at 16:00 - 17:30, 2023

Torben Christian Frost (Postdoctoral Researcher, Kavli Institute for Astronomy and Astrophysics, Peking University, China)

Einstein's field equations allow various different black hole solutions. Among these solutions, the most famous are most likely the Schwarzschild and the Kerr spacetimes, which are both special cases of the so-called Plebanski-Demianski spacetime. Besides the Schwarzschild and Kerr spacetimes, the Plebanski-Demianski spacetime also includes other solutions as special cases, among them the C-metric and the NUT metric. They describe a linearly accelerating black hole and a black hole with gravitomagnetic charge, respectively. The question is now how we can determine if an astrophysical black hole can be described by one of these spacetimes. We will address this question using gravitational lensing for the three spacetimes with the most salient lensing features, namely the C-metric, the NUT metric, and the Kerr metric. For this purpose, we will first outline how to solve the equations of motion analytically using elementary and Jacobi's elliptic functions as well as Legendre's elliptic integrals. Then we will fix an observer in the domain of outer communication and relate the constants of motion of the lightlike geodesics to latitude-longitude coordinates on the observer's celestial sphere. We will use the analytic solutions to write down the lens equations, calculate the redshift, and the travel time. Finally, we will discuss and compare the results and comment on how we can use them to place constraints on the spin parameter, the acceleration parameter, and the gravitomagnetic charge of a black hole.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Cosection localization via shifted symplectic geometry

December 6 (Wed) at 10:00 - 11:30, 2023

Young-Hoon Kiem (Professor, School of Mathematics, Korea Institute for Advanced Study (KIAS), Republic of Korea)

Modern enumerative invariants are defined as integrals of cohomology classes against virtual fundamental classes constructed by Li-Tian and Behrend-Fantechi. When the obstruction sheaf admits a cosection, the virtual fundamental class is localized to the zero locus of the cosection. When the cosection is furthermore enhanced to a (-1)-shifted closed 1-form, the zero locus admits a (-2)-shifted symplectic structure and thus we have another virtual fundamental class by the Oh-Thomas construction. An obvious question is whether these two virtual fundamental classes coincide or not. In this talk, we will see that (-1)-shifted closed 1-forms arise naturally as an analogue of the Lagrange multiplier method. Furthermore, a proof of the equality of the two virtual fundamental classes and its applications will be discussed. Based on a joint work with Hyeonjun Park.

Venue: Seminar Room #359

Event Official Language: English

Translating between evolutionary game theory and theoretical ecology

December 5 (Tue) at 16:30 - 17:30, 2023

Arne Traulsen (Director, Department for Theoretical Biology, Max Planck Institute for Evolutionary Biology, Germany)

Both theoretical ecology and evolutionary game theory describe the dynamics of interacting populations. More than 40 years ago, Hofbauer and Sigmund established a mathematical equivalence between the Lotka-Volterra equations and the replicator dynamics from evolutionary game theory. However, this equivalence has not been exploited by empiricists so far. One of the issues is dimensionality: An ecological interaction of two species corresponds to an evolutionary game between three types. Only when we focus on a special case with identical growth rates, it is possible to translate without this trick, leading to a more direct equivalence between the frameworks. Consequently, one has to be particularly careful how to classify interactions and how to assess dynamical outcomes. For example, a ‘Prisoner's Dilemma’ interaction where the `cooperators' have a higher intrinsic growth rate than `defectors' can result in stable coexistence of the two types and may ultimately not represent a social dilemma at all.

Venue: via Zoom

Event Official Language: English

Rotating discs on the Kerr black hole background

December 5 (Tue) at 15:00 - 16:30, 2023

David Kofroň (Postdoctoral Researcher, Institute of Theoretical Physics, Charles University, Czechia)

Analytical solution of a rotating black hole surrounded by accretion disc in full GR is, so far, unknown. The Ernst equation is nonlinear. In this talk, we will provide a framework in which the solutions of linearised Ernst equations can be obtained from the linear perturbations of Kerr black hole treated in the formalism of the Debye potentials. In this way, we recover all the metric perturbations in term of a single complex scalar function (which solves the Laplace equation).

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Gravity of Accretion Discs and Black Holes

December 5 (Tue) at 14:00 - 15:00, 2023

Petr Kotlařík (Ph.D. Student, Institute of Theoretical Physics, Charles University, Czechia)

The typical black hole solutions describe only isolated black holes. However, in astrophysics, such a condition is never strictly satisfied. As matter accretes onto the black hole, disc structures are often formed. In this talk, I will summarize our recent attempts to find the gravitational field of such a nonisolated black hole. We start from the simplest case of static and axially symmetric metric. Although it is a somewhat "rough" approximation in the astrophysical context, this idealization may already help us to understand some interesting implications of the disc's gravity. Moreover, with such a simplification, we can obtain exact analytical "superpositions" of the Schwarzchild black hole and a disc. When some rotation is present, dragging effects complicate the situation dramatically. Then, one typically has to resort to numerical relativity or some approximate methods, e.g., perturbations. In the talk, I also address the stationary case and demonstrate what we can do on the level of the direct metric perturbation.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Breaking down the magnonic Wiedemann-Franz law in the hydrodynamic regime

December 4 (Mon) at 15:00 - 16:30, 2023

Ryotaro Sano (Ph.D. Student, Division of Physics and Astronomy, Graduate School of Science, Kyoto University)

Quantum transport has attracted a profound growth of interest owing to its fundamental importance and many applications in condensed matter physics. Recent significant developments in experimental techniques have further boosted the study of quantum transport. Notably in ultraclean systems, strong interactions between quasi-particles drastically affect the transport properties, resulting in an emergent hydrodynamic behavior. Recent experiments on ultrapure ferromagnetic insulators have opened up new pathways for magnon hydrodynamics. Hydrodynamic magnon transport implies exhibiting extraordinary features and has a potential for innovative functionalities beyond the conventional non-interacting magnon picture. However, the direct observation of magnon fluids remains an open issue due to the lack of probes to access the time and length scales characteristics of this regime. In this work, we derive a set of coupled hydrodynamic equations for a magnon fluid and study the spin and thermal conductivities by focusing on the most dominant time scales [1]. As a hallmark of the hydrodynamic regime, we reveal that the ratio between the two conductivities shows a large deviation from the so-called magnonic WF law. We also identify an origin of the drastic breakdown of the magnonic WF law as the difference in relaxation processes between spin and heat currents, which is unique to the hydrodynamic regime. Therefore, our results will become key evidence for an emergent hydrodynamic magnon behavior and lead to the direct observation of magnon fluids.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Evolution by gene and genome duplications

November 28 (Tue) at 16:00 - 17:00, 2023

Jeffrey Fawcett (Senior Research Scientist, RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS))

Each organism typically has (tens of) thousands of genes in its genome that perform various molecular and cellular functions, but how did these genes originate? The answer for most genes is by the duplication of another gene. In fact, all the genes (the entire genome) can get duplicated simultaneously on some instances. Thus, gene and genome duplications are considered key driving forces of evolution and are one of the most important topics in molecular evolutionary biology. In this talk, I will introduce the background and basic concepts related to gene and genome duplications. The talk will be aimed at non-experts so non-biologists are also welcome to attend.

Venue: via Zoom

Event Official Language: English

Joint RIKEN/N3AS Workshop on Multi-Messenger Astrophysics

November 26 (Sun) at 9:00 - 19:00, 2023

RIKEN iTHEMS and NSF Physics Frontier Center N3AS will jointly organize a workshop on "Multi-Messenger Astrophysics" on Sunday, November 26, at the Hilton Waikoloa Village, in conjunction with the JPS/ APS DNP meeting. For the program and registration form, please visit the workshop website at the related links. The workshop is open to all and there is no registration fee. However, we ask those wishing to attend to register, to help us plan. The workshop will conclude with an early evening poster session that will combine science with an opportunity for JPS and APS participants to socialize. Organizers: Tetsuo Hatsuda（RIKEN iTHEMS) Wick Haxton (UC Berkaley, N3AS) Baha Balentekin (UW-Madison, N3AS)

Venue: Hilton Waikoloa Village, Waikoloa, Hawaii

Event Official Language: English