14:45-15:00 Teatime discussion
15:00-16:00 Talk by Prof. Satoshi Taguchi (Professor, Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University)
16:15-17:15 Talk by Prof. Yoshihiro Morishita (Professor, Division of Biological Sciences, Graduate School of Science, Kyoto University)
17:15-18:00 Discussion

The evolution of spiteful and altruistic behaviour remains a fascinating and somewhat puzzling phenomenon. In recent years there has been interest in examining how stochasticity arising from a finite population size might affect the evolution of these traits. Some results suggest that such stochasticity can reverse the direction of selection and promote the evolution of traits like altruism and spitefulness that are selected against in very large (deterministic) populations. However, other results seem to call this finding into question. In this talk I will consider a simple but quite general model of spite and of altruistic behaviour and examine how demographic stochasticity affects the evolution of these traits. I will show that stochasticity can indeed affect the direction of evolution but not in the way that previous studies have suggested. The results also help to clarify the broader issue of how and why stochasticity can sometimes reverse the direction of evolution.

We investigate tensionless (or null) bosonic string theory with a constant Kalb-Ramond
background turned on. In analogy with the tensile case, we find that the constant Kalb-Ramond field
has a non-trivial effect on the spectrum only when the theory is compactified on an S^1 ⊗d
background with d ≥ 2. We discuss the effect of this constant background field on the tensionless
spectrum constructed on three known consistent null string vacua. We elucidate further
on the intriguing fate of duality symmetries in these classes of string theories when the
background field is turned on. Based on: https://arxiv.org/abs/2404.01385

The problem of embedding abstract Riemannian manifolds isometrically (i.e. preserving the lengths) into Euclidean space stems from the conceptually fundamental question of whether abstract Riemannian manifolds and submanifolds of Euclidean space are the same. As it turns out, such embeddings have a drastically different behaviour at low regularity (i.e. C¹) than at high regularity (i.e. C²). For example, by the famous Nash--Kuiper theorem it is possible to find C1 isometric embeddings of the standard 2-sphere into arbitrarily small balls in R³, and yet, in the C² category there is (up to translation and rotation) just one isometric embedding, namely the standard inclusion. Analoguous to the Onsager conjecture in fluid dynamics, one might ask if there is a sharp regularity threshold in the Holder scale which distinguishes these flexible and rigid behaviours. In my talk I will review some known results and argue why the Holder exponent 1/2 can be seen as a critical exponent in the problem.

Quantum simulation is a novel method of simulation physical systems with quantum computers. Compared to conventional methods, quantum algorithms have various advantages in doing non-perturvative calculations and real-time evolutions, which makes it very promising to apply them in high energy nuclear physics. We propose a systematic quantum algorithm, which integrates both the hadronic state preparation and the evaluation of real-time light-front correlators. This algorithm can be applied to the calculation of a wide range of quantities in high energy nuclear physics. As a demonstration, we calculate the parton distribution functions, the light-cone distribution amplitudes and scattering amplitudes in the 1+1 dimensional NJL model. The results are qualitatively consistent with QCD calculations.

9:30-10:00 Keynote by Lucy Mcneill
10:00-10:30 Keynote by Jose Said Gutierrez Ortega
10:35-11:05 Keynote by Puttarak Jai-akson
11:05-11:35 Keynote by Kannaka Kazuki

11:35-12:30 Lunch Time Session

12:30-13:30 Working Group / Study Group Report

13:30-15:30 Flash Talk & Poster Presentation Part 1

15:30-17:30 Flash Talk & Poster Presentation Part2
17:30 Concluding Remarks by the Director

18:00 reception

Recently, the layered honeycomb material α-RuCl3 exhibits several anomalous features that are consistent with expectations of the Kitaev quantum spin liquid (KQSL) under in-plane magnetic field. Most remarkably, finite planar thermal Hall conductivity has been observed, whose magnitude is close to the half-integer quantization value expected for the chiral edge currents of Majorana fermions[1]. However, it has been reported that the thermal Hall conductivity shows strong sample dependence. Also, there are attempts to offer a different explanation by the bosonic edge excitations due to topological magnons or phonon. A key to distinguishing between fermionic and bosonic origins of unusual features in the high-field state of α-RuCl3 is the difference in the field angle dependence of the excitation gap.

Therefore, we distinguish these origins from combined low-temperature measurements of high-resolution specific heat and thermal Hall conductivity with rotating magnetic fields within the honeycomb plane. A distinct closure of the low-energy bulk gap is observed for the fields in the Ru-Ru bond direction, and the gap opens rapidly when the field is tilted. Notably, this change occurs concomitantly with the sign reversal of the Hall effect. General discussions of topological bands show that this is the hallmark of an angle rotation–induced topological transition of fermions, providing conclusive evidence for the Majorana-fermion origin of the thermal Hall effect in α-RuCl3[2].

Furthermore, to understand the nature of the high-field state, it is crucial to elucidate the effects of disorder, which inevitably exists in real materials. We artificially introduce point defects by electron irradiation and compare the low-energy excitations in the pristine and irradiated sample by high-resolution specific heat measurements. We observed an additional in-gap T-linear term in C/T, whose coefficient shows distinct field-sensitive behaviors suggestive of Majorana physics in the KSL. This can be interpreted by the weak localization of Majorana fermions, which is induced by the disorder[3]. Moreover, recently, we succeed in synthesizing very high-quality crystals of α-RuCl3[4].

The radiation-dominated universe is a key component of standard Big Bang cosmology. Radiation comprises numerous quantum elementary particles, and its macroscopic behavior is described by taking the quantum thermal average of its constituents. The dynamics of gravitational waves are considered in this smooth fluid. While interactions between individual particles and gravitational waves are often neglected in this context, it raises the question of whether such a hydrodynamical approximation is reasonable. To address this question, we explored the quantum mechanical aspects of gravitational waves in a universe dominated by a massless scalar field, whose averaged energy-momentum tensor serves as background radiation. We computed thermal loop corrections for the gravitational wave power spectrum using the Schwinger-Keldysh formalism. Interestingly, we found that the loop effect enhances the super-horizon primordial gravitational wave spectrum, indicating that the inflationary spectrum is not conserved, contrary to conventional wisdom. These findings have significant implications for our understanding of the early universe. In this talk, I will begin with the basics of cosmology and explain the significance of these results and their relevant observational consequences.

Humans and other organisms develop collective behaviors through interactions with diverse environments and various species. These behaviors are significant topics across multiple research fields, including evolutionary biology, behavioral ecology, and animal sociology. Unraveling the decision-making mechanisms of individuals in groups within cooperative and competitive contexts has captured the attention of many researchers but remains a complex challenge. This seminar will present research cases that employ multi-agent reinforcement learning, a machine learning technique, to investigate the decision-making processes underlying collective behavior. Through this approach, we aim to provide deeper insights into the dynamics and mechanisms that drive group behaviors in various biological systems.

In mathematics, contact geometry is a type of geometry describing a variety of dynamical systems. They are the phase spaces of systems arising in geometric optics, semi-classical quantum systems, classical dynamics, and control theory. On the mathematical side, contact geometry relates to a variety of other geometric structures, such as Kahler geometry, smooth topology, and foliation theory. It can be especially interesting to look at contact geometry in 3-dimensional space, because we can explicitly visualize the spaces. Additionally, by connecting contact geometry with our understanding of 3-D topology, mathematicians have the ability to understand the large-scale structure of these spaces like never before.
The talk will introduce the basics of contact geometry and its applications. We'll particularly focus on the 3-dimensional case, while also mentioning some of the unique properties of higher-dimensional spaces which are recently being explored.

Registration required: Register before Wednesday, July 24, 15:00.