In a simple Higgs inflation model in metric-affine gravity, it is known that its UV cutoff is much smaller than the Planck scale. While it calls for UV completion, a concrete example has not yet been found, even with the large-N limit known as a successful technique to complete an original Higgs inflation defined on the Riemannian geometry. In this talk, after a review of the unitarity issue and previous attempts to complete Higgs inflation models, we investigate how small deformation of the simple Higgs inflation affects the emergence and properties of dynamical fields particularly in the large-N limit.

The quantisation of gravity is widely believed to result in gravitons - particles of discrete energy that form gravitational waves. But their detection has so far been considered impossible. Here we show that signatures of single gravitons can be observed in laboratory experiments. We show that stimulated and spontaneous single graviton processes can become relevant for massive quantum acoustic resonators and that stimulated absorption can be resolved through optomechanical read-out of single phonons of a multi-mode bar resonator. We analyse the feasibility of observing a signal from the inspiral, merger and post-merger phase of a compact binary inspiral. Our results show that single graviton signatures are within reach of experiments. In analogy to the discovery of the photoelectric effect for photons, such signatures can provide the first experimental evidence of the quantisation of gravity.

[1] G. Tobar, S. K. Manikandan, T. Beitel, and I. Pikovski, Nature Communications 15, 7229.
[2] G. Tobar, Igor Pikovski ,Michael E. Tobar, arXiv:2406.16898 (2024).

Abstract: Nontrivial topological defects such as knotted solitons called hopfions have been observed in a variety of materials including chiral magnets, nematic liquid crystals and even in ferroelectrics as well as studied in other physical contexts such as Bose-Einstein condensates. These topological entities can be modeled using the relevant physical variable, e.g., magnetization, polarization or the director field. Specifically, we find exact static soliton solutions for the unit spin vector field of an inhomogeneous, anisotropic three-dimensional (3D) Heisenberg ferromagnet and calculate the corresponding Hopf invariant H analytically and obtain an integer, demonstrating that these solitons are indeed hopfions [1]. H is a product of two integers, the first being the usual winding number of a skyrmion in two dimensions, while the second encodes the periodicity in the third dimension. We also study the underlying geometry of H, by mapping the 3D unit vector field to tangent vectors of three appropriately defined space curves. Our analysis shows that a certain intrinsic twist is necessary to yield a nontrivial topological invariant: linking number [2]. Finally, we focus on the formation energy of hopfions to study their properties for potential applications.

Short bio: Avadh Saxena is former Group Leader of the Condensed Matter and Complex Systems group (T-4) at Los Alamos National Lab, New Mexico, USA where he has been since 1990. He is also an affiliate of the Center for Nonlinear Studies at Los Alamos. His main research interests include phase transitions, optical, electronic, vibrational, transport and magnetic properties of functional materials, device physics, soft condensed matter, non-Hermitian quantum mechanics, geometry, topology and nonlinear phenomena & materials harboring topological defects such as solitons, polarons, excitons, breathers, skyrmions and hopfions. He recently completed a book on “Phase Transitions from a Materials Perspective” (Cambridge University Press, 2024). He is an Affiliate Professor at the Royal Institute of Technology (KTH), Stockholm, Sweden and holds adjunct professor positions at the University of Barcelona, Spain, University of Crete, Greece, Virginia Tech and the University of Arizona, Tucson. He is Scientific Advisor to National Institute for Materials Science (NIMS), Tsukuba, Japan. He is a Fellow of Los Alamos National Lab, a Fellow of the American Physical Society (APS), a Fellow of the Japan Society for the Promotion of Science (JSPS) and a member of the Sigma Xi Scientific Research Society, APS and American Ceramic Society (ACerS).

Emergence of space-time is a key concept in matrix models as a nonperturbative formulation of string theory. In this lecture, starting with a brief introduction to nonperturbative effects in string theory, I will review various aspects of emergence of space-time in matrix models. The topics I discuss include dynamical triangulation, double scaling limit, eigenvalue instanton, large-N reduction, T-duality for D-brane effective theories (orbifolding), noncommutative geometry and covariant derivative interpretation. Finally, I will introduce the type IIB matrix model.

(This is the 7th Intensive Lectures by Quantum Gravity Gatherings in iTHEMS. )

Program
December 17
10.15~10.30 Registration and Coffee
10.30~12.00 Lecture 1
12.00~13.30 Lunch
13.30~15.00 Lecture 2
15.00~16.00 Coffee break
16.00~17.00 Lecture 3
17.30~19.30 Banquet

December 18
10.15~11.45 Lecture 4
11.45~13.30 Lunch
13.30~15.00 Lecture 5
15.00~16.00 Coffee break
16.00~17.00 Lecture 6

December 19
10.15~11.45 Lecture 7
11.45~13.30 Lunch
13.30~15.00 Lecture 8
15.00~16.00 Coffee break
16.00~17.00 Lecture 9

Dark matter (DM), a mysterious non-luminous component of the universe, dominates the mass distribution in galaxies and clusters yet remains elusive in its interactions beyond gravity. Neutron stars (NSs), among the most compact objects in the universe, provide unique astrophysical laboratories to investigate the interplay between DM and extreme matter due to their immense densities and gravitational fields. In this talk, I will briefly outline the mechanisms through which DM could be gravitationally captured by NSs, including during their formation and evolution. The primary focus will then shift to the structural and observable implications of DM admixed NSs. I will discuss the theoretical frameworks used to model DM admixed NSs and how DM parameters, such as particle mass and density profiles, modify the equation of state and structural stability of these stars. Observational constraints from pulsars like PSR J0740+6620 and gravitational wave events such as GW170817 will be highlighted as critical tools for deducing DM characteristics and testing theoretical model predictions. By presenting insights from recent studies, including our own work, this talk aims to demonstrate how astrophysical observations can constrain DM parameters and provide a deeper understanding of DM’s role in dense astrophysical environments. I will conclude with a discussion of future prospects for advancing both theoretical models and observational strategies in this interdisciplinary field.

Normalizing Flows (NFs) are a class of deep generative models that have recently been proposed as efficient samplers for Lattice Field Theory. Although NFs have demonstrated impressive performance in toy models, their scalability to larger lattice volumes remains a significant challenge, limiting their application to state-of-the-art problems. A promising approach to overcoming these scaling limitations involves combining NFs with non-equilibrium Markov Chain Monte Carlo (NEMCMC) algorithms, resulting in Stochastic Normalizing Flows (SNFs). SNFs harness the scalability of MCMC samplers while preserving the expressiveness of NFs. In this seminar, I will introduce the concepts of NEMCMC and NFs, demonstrate their combination into SNFs, and outline their connections with non-equilibrium thermodynamics. I will conclude by discussing key aspects of SNFs through their application to Effective String Theory, SU(3) gauge theory, and conformal field theory.

I will explore the transformative role of genomic tools in understanding biological diversity across a range of organisms. By delving into the genetic blueprints of various species, we can unravel evolutionary histories, identify key traits for conservation, and develop strategies to preserve endangered ecosystems. Additionally, I will discuss practical applications of genomic data, such as enhancing agricultural biodiversity, improve traditional uses, and fostering sustainable development. Through case studies and recent advancements, this presentation highlights the critical intersection of genomics, biodiversity preservation, and its multifaceted uses in addressing global challenges.

Neutron stars - the densest stars in the Universe - cool down mainly by loss of neutrinos, emitted from the stars' interior due to particle reactions. By comparing cooling models with observed surface temperature or luminosity, one can probe the properties of high-density matter, such as what kind of particles and states exist inside neutron stars. In this presentation, I will first review cooling theory, focusing on the neutrino cooling processes. In particular, we focus on the equation of state (EOS) uncertainties, which significantly affect cooling curves. We discuss aspects such as the effect of including hyperons in our EOS. Using the updated cooling code, C-HERES, we calculate cooling curves with different EOS. Finally, we present the future prospects for this study.

For a given system, the structure of the minimal subspace where the state unfolds determines the static and dynamical properties of the state. The Krylov subspace method is a mathematical framework for constructing the space systematically and has been applied to a wide variety of problems. The method was applicable only for systems with time-indepedent generators. As applications to quantum dynamics with time-dependent Hamiltonians, we discuss the constrution of the adiabatic gauge potential and the generalization of the Krylov algorithm to time-dependent generators.

Light hypothetical particles with masses up to O(100) MeV can be produced in the core of supernovae. Their subsequent decays to neutrinos can produce a flux component with higher energies than the standard flux. We study the impact of heavy neutral leptons, Z′ bosons, in particular U(1)Lμ−Lτ and U(1)B−L gauge bosons, and majorons coupled to neutrinos flavor-dependently. We obtain new strong limits on these particles from no events of high-energy SN 1987A neutrinos and their future sensitivities from observations of galactic supernova neutrinos.

Anthropologists have long noted structural similarities among geographically distant societies. To investigate the origins of these patterns, I develop simple models of human interactions based on field observations, simulating the emergence of social structures. This talk focuses on two key topics. The first examines the evolution of kinship structures in clan societies [1, 2, 3]. By modeling kin and in-law cooperation alongside mating competition, I show how cultural groups with specific marriage rules spontaneously emerge. The second explores the transition of social organizations through competitive gift-giving [4, 5]. By modeling how gifts deliver material goods to recipients and confer social reputation upon donors, I demonstrate transitions across four phases—band, tribe, chiefdom, and kingdom—each characterized by distinct social networks and distributions of wealth and reputation. In both cases, I highlight the alignment between theoretical predictions and empirical observations, offering quantitative criteria and empirically measurable explanatory parameters for classifying social structures.

The KdV equation and the Toda lattice are two central and widely studied examples of classical integrable systems, and many of their variations have been introduced to the present. In particular, the box-ball system (BBS) is a basic example of a discrete integrable system, which has been revealed to be an ultra-discrete version of the KdV equation and the Toda lattice. The BBS has been studied from various viewpoints such as tropical geometry, combinatorics, and cellular-automaton. As a new perspective, research on probabilistic approaches to this system has been rapidly expanding in recent years, including the application of the Pitman transform, analysis of invariant measures and its generalized hydrodynamics. More recently, we find that the application of the Pitman transform and the study of invariant measures of i.i.d.-type also work in the same manner for the discrete KdV equation and the discrete Toda lattice. Further research has begun on the relationship between the Yang-baxter maps and the existence of i.i.d.-type invariant measures for the discrete integrable systems. In this talk, I will introduce these new research topics that have been spreading over the past several years from the basics. This talk is based on several joint works with David Croydon, Tsuyoshi Kato, Satoshi Tsujimoto, Ryosuke Uozumi, Matteo Mucciconi, Tomohiro Sasamoto, Hayate Suda and Stefano Olla.

Note for participants:
For participants, please register from the above form. We may limit the number of participants due to the capacity of the lecture room.
For participants in RIKEN who have already answered a questionnaire on this lecture, you do not have to register.

Program:
Day 1 (Jan. 28th)
10:30-12:00 Lecture 1
12:00-13:30 Lunch time
13:30-15:00 Lecture 2
15:00-15:30 Coffee break
15:30-17:00 Lecture 3

Day 2 (Jan. 29th)
10:30-12:00 Lecture 4
12:00-13:30 Lunch time
13:30-15:00 Lecture 5
15:00-15:30 Coffee break
15:30-17:00 Lecture 6

Abstract:
Quantum Error Mitigation (QEM) offers a practical approach to reducing errors in noisy intermediate-scale quantum (NISQ) devices without requiring the encoding of qubits. In this seminar, I will begin by discussing the fundamentals of noise modeling in quantum systems, followed by an overview of QEM techniques, including extrapolation, probabilistic error cancellation (PEC), virtual distillation, quantum subspace expansion, and Clifford data regression. Next, I will present advanced QEM methods, such as the stochastic PEC approach, which mitigates the effects of Lindblad terms in Lindblad master equations and the generalized quantum subspace expansion, which is a unified framework of QEM. I will also explore recent research on the information-theoretic analysis of QEM, shedding light on its fundamental limits and connections to non-Markovian dynamics. Furthermore, I will discuss studies combining QEM with quantum error correction to enhance the reliability of computations in the early fault-tolerant quantum computing era. Lastly, I will highlight the relevance of hybrid tensor networks, particularly their connections to quantum subspace expansion techniques.

Research on planet formation involves various approaches, including explorations of small solar system bodies, observations of protoplanetary disks, dust experiments, simulations, and theoretical studies. One of the primary objectives in this field is to develop a comprehensive theory that explains how kilometer-sized planetesimals form from micrometer-sized dust grains, drawing upon findings from these diverse research methods.

This workshop will focus on the concept of pebbles, which play a crucial role in the planet formation process. Pebbles — typically defined as solids ranging from millimeter to centimeter in size — are intermediate building blocks in planet formation, though their definition varies depending on the context. Assuming pebbles has led to theoretical advances in mechanisms such as streaming instability and pebble accretion, which promote the formation and growth of planetesimals. Additionally, pebbles have been linked to barriers against dust growth, such as the bouncing barrier. Furthermore, observations of protoplanetary disks have revealed the size distribution and porosity of solids, while the strength and thermal conductivity of comets obtained by the Rosetta mission suggest the accumulation of pebbles due to disk instabilities. However, inconsistencies have been pointed out between pebble formation and theories of dust growth.

This workshop aims to revisit and refine our understanding of solid materials implicated in planet formation, particularly in light of findings from solar system explorations and protoplanetary disk observations. We aim to reevaluate the definition and role of pebbles in the broader context of planet formation, with a special focus on the current challenges and open questions in the field. The workshop will include discussions of experiments and simulations of dust growth and collisions, and planetesimal formation mechanisms such as streaming instability. The workshop features keynote talks from the perspectives of explorations, observations, experiments, simulations, and theories, and we also call for presentations on related topics.

The density functional theory (DFT) is one of the powerful methods to solve quantum many-body problems, which, in principle, gives the exact energy and density of the ground state. The accuracy of DFT is, in practice, determined by the accuracy of an energy density functional (EDF) since the exact EDF is still unknown. Currently, DFT has been used in many communities, including nuclear physics, quantum chemistry, and condensed matter physics, while the fundamental study of DFT, such as the first principle derivations of an accurate EDF and methods to calculate many observables from obtained densities and excited states, is still ongoing. However, there has been little opportunity to have interdisciplinary communication.

On December 2022, we had the first workshop on this series (DFT2022) at Yukawa Institute for Theoretical Physics, Kyoto University, and several interdisciplinary discussions and collaborations were started. On February 2024, we had the second workshop on this series (DFT2024) at RIKEN Kobe Campus, and more stimulated discussion occured. To keep and extend collaborations, we organize the third workshop. Since the third workshop, we extend the scope of the workshop to the development and application of DFT as well. In this workshop, the current status and issues of each discipline will be shared towards solving these problems by meeting together among researchers in mathematics, nuclear physics, quantum chemistry, and condensed matter physics.

This workshop mainly comprises lectures/seminars on cutting-edge topics and discussion, while sessions composed of contributed talks are also planned.