EOS Dependence on Cooling of Isolated Neutron Stars

December 20 (Fri) at 14:00 - 15:15, 2024

Stavros Fakiolas (Ph.D. Student, University of Oxford, UK)

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.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Applied plant genomics for evolutionary history, agriculture, and conservation

December 19 (Thu) at 16:00 - 17:00, 2024

Antonio Hernández-López (Professor, National Autonomous University of Mexico, Mexico)

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.

Venue: via Zoom

Event Official Language: English

Stochastic Normalizing Flows for Lattice Field Theory

December 18 (Wed) at 15:30 - 16:30, 2024

Elia Cellini (PhD, Department of Physics, University of Turin, Italy)

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.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Dark Matter and Neutron Stars: A Gravitational Laboratory for the Unknown

December 18 (Wed) at 10:00 - 11:30, 2024

Ankit Kumar (Postdoctoral Fellow, Faculty of Science and Technology, Kochi University)

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.

Venue: via Zoom

Event Official Language: English

7th QGG Intensive Lectures: Emergence of space-time in matrix models

December 17 (Tue) - 19 (Thu), 2024

Asato Tsuchiya (Professor, Shizuoka University)

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

Venue: #435-437, 4F, Main Research Building

Event Official Language: English

Hopfions in Condensed Matter and Field Theory

December 16 (Mon) at 16:00 - 17:30, 2024

Avadh Saxena (Professor, Los Alamos National Laboratory, USA)

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).

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Detecting single gravitons with quantum controlled mechanical oscillators

December 16 (Mon) at 14:00 - 15:30, 2024

Germain Tobar (PhD Fellow, Stockholm University, Norway)

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).

Venue: #359, 3F, Seminar Room #359

Event Official Language: English

Matter-Wave Interferometry in the Limit of High Mass and Internal Complexity, and the Relevance of Optomechanical Sources

December 16 (Mon) at 10:00 - 11:00, 2024

Markus Arndt (Professor, University of Vienna, Austria)

The seminar will feature a lecture by Professor Markus Arndt from the University of Vienna. Following the lecture, starting at approximately 11:00 AM, Nobuyuki Matsumoto will give a brief introduction to his research and conduct a tour of his laboratory. Hosted by Gakushuin University Co-hosted by iTHEMS

Venue: Room 007, South Building 4, Gakushuin University

Event Official Language: English

Perturbative unitarity of Higgs inflation in the Riemannian and generalized geometry

December 13 (Fri) at 16:00 - 17:30, 2024

Yusuke Mikura (Ph.D. Student, C-Lab, Department of Physics, Institute for Advanced Research, Nagoya University)

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.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Particle acceleration in relativistic astrophysical plasmas

December 13 (Fri) at 14:00 - 15:15, 2024

Camilia Demidem (Research Scientist, iTHEMS)

Relativistic astrophysical objects often display evidence of very efficient particle acceleration, such as X-ray and gamma-ray nonthermal emission and are widely recognized as potential sources of cosmic rays. Elucidating the physical mechanisms that turn these environments into such formidable particle accelerators is a longstanding problem of high-energy astrophysics. In this talk, I will briefly explain why shocks and turbulence, naturally expected to occur in these environments, could play an essential role in the acceleration of particles. I will then discuss some of the challenges that poses the description of these nonlinear processes, especially in the context of high-energy astrophysical sources, which involve astronomical ranges of scales and physical conditions much more extreme than we can probe in our laboratories or in the Solar system. Finally, I will share some recent results from my simulations.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Recent Advances in the Spectral Geometry of Domains and Approaches with Computer-Assisted Proofs

December 12 (Thu) at 15:00 - 17:00, 2024

Ryoki Endo (Ph.D. Student, Fundamental Sciences, Graduate School of Science and Technology, Niigata University)

What can we determine about the shape of a drum from its sound?"—This inverse problem has given rise to spectral geometry and has attracted researchers for over 110 years. The first half of the talk explains recent advances in shape optimization problems for domains with respect to eigenvalues of the Laplacian and the inverse problem known as "hearing the shape of a drum," presented in an accessible manner for experts from other disciplines. The second half introduces verified computation methods for eigenvalues, eigenfunctions, and shape derivatives. As applications, it presents newly established computer-assisted proofs for the minimization problem of eigenvalues with non-homogeneous Neumann boundary conditions, and the conjecture on the simplicity of the second Dirichlet eigenvalues for non-equilateral triangles.

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

Event Official Language: English

Mechanism for Converting Temporal Rhythms into Spatial Patterns of Body Segment

December 12 (Thu) at 13:00 - 14:00, 2024

Koichiro Uriu (Associate Professor, School of Life Science and Technology, Institute of Science Tokyo)

In development, spatially periodic structures are spontaneously formed in various tissues. These developmental structures are also formed in a proper temporal order. How is such spatial and temporal coordination achieved in morphogenesis? In this presentation, we discuss the mechanism that translates temporal rhythms of gene expression into spatially periodic patterns in vertebrate body segment formation. Mechanisms for converting oscillatory signals into vertebrate body segments have been proposed previously. Cooke and Zeeman 1976 proposed the Clock and Wavefront model based on the concept of the catastrophe theory. Still, it remains unclear how this conceptual model actually works in embryos. Here we develop a mathematical model aided by recent imaging and molecular genetics data and reveal a spatiotemporal bifurcation structure for vertebrate segment formation by using the dynamical systems theory.

Venue: Seminar Room #359 / via Zoom

Event Official Language: English

How Neural Networks reduce the Fermionic Sign Problem and what we can learn from them

December 11 (Wed) at 15:30 - 16:30, 2024

Johann Ostmeyer (Post-doctoral Fellow, Helmholtz-Institut für Strahlen- und Kernphysik, University of Bonn, Germany)

When simulating fermionic quantum systems, non-perturbative Monte Carlo techniques are often the most efficient approach known to date. However, beyond half filling they suffer from the so-called sign problem, i.e. negative "probabilities", so that stochastic sampling becomes infeasible. Recently, considerable progress has been made in alleviating the sign problem by deforming the integration contour of the path integral into the complex plane and applying machine learning to find near-optimal alternative contours. In this talk, I am going to present a particularly successful architecture, based on complex-valued affine coupling layers. Furthermore, I will demonstrate how insight gained from the trained network can be used for simpler analytic approaches.

Venue: via Zoom / Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Simulating Parton Fragmentation on Quantum Computers

December 11 (Wed) at 13:30 - 15:00, 2024

Tianyin Li (Ph.D. Student, Institute of Quantum Matter, South China Normal University, China)

Parton fragmentation functions (FFs) are indispensable for understanding processes of hadron production ubiquitously existing in high-energy collisions, but their first principle determination has never been realized due to the insurmountable difficulties in encoding their operator definition using traditional lattice methodology. We propose a framework that makes a first step for evaluating FFs utilizing quantum computing methodology. The key element is to construct a semi-inclusive hadron operator for filtering out hadrons of desired types in a collection of particles encoded in the quantum state. We illustrate the framework by elaborating on the Nambu-Jona-Lasinio model with numeral simulations. Remarkably, We show that the semi-inclusive hadron operator can be constructed efficiently with a variational quantum algorithm. Moreover, we develop error mitigation techniques tailed for accurately calculating the FFs in the presence of quantum noises. Our work opens a new avenue for investigating QCD hadronization on near-term quantum computers.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Studying quark-gluon plasma with multi-stage dynamical models in relativistic nuclear collisions

December 10 (Tue) at 15:30 - 17:00, 2024

Yuuka Kanakubo (Postdoctoral Researcher, iTHEMS)

A collision of relativistically accelerated large nuclei creates the hottest matter on Earth — quark-gluon plasma (QGP). The properties of QGP have been studied through comparisons of final-state particle distributions between theoretical models and experimental data. To quantitatively constrain QGP properties, it is necessary to build Monte Carlo models that simulate the space-time evolution of the system throughout the entire collision process. This includes the initial matter production from the accelerated nuclei, the evolution of QGP, hadronisation, and the evolution of hadron gas. In this talk, I will first explain how theoretical models, based on relativistic hydrodynamics and hadronic transport, are conventionally built and how they successfully extract QGP properties. Next, I will discuss a hot topic: the possibility of finding QGP in proton-proton collisions, based on results from a state-of-the-art model that includes both equilibrated and non-equilibrated systems. Also, I will introduce a novel Monte Carlo initial state model based on perturbative QCD minijet production supplemented with a saturation picture. This Monte-Carlo EKRT model is one of the first initial state models for hydrodynamics to describe initial particle production from small to large momentum within a single framework, where total energy-momentum and charge conservations are imposed.

Venue: #359 3F, Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Entanglement of astrophysical neutrinos

December 10 (Tue) at 13:30 - 15:00, 2024

Baha Balantekin (Eugene P. Wigner Professor, Department of Physics, University of Wisconsin-Madison, USA)

Collective oscillations of neutrinos represent emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. In this talk, after a brief introduction, it will be shown that neutrinos exhibit interesting entanglement behavior in simplified models of those oscillations. Attempts to study this behavior using classical and quantum computers will be described. An intriguing connection to the heavy-element nucleosynthesis, namely the possibility of neutrino entanglement driving a new kind of i-process nucleosynthesis, will be introduced,

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Dark matter from inflationary quantum fluctuations

December 9 (Mon) at 14:00 - 15:30, 2024

Mohammad Ali Gorji (Junior Faculty, Center for Theoretical Physics of the Universe, Institute for Basic Science, Republic of Korea)

We explore a scenario in which dark matter is a massive bosonic field, arising solely from quantum fluctuations generated during inflation. In this framework, dark matter exhibits primordial isocurvature perturbations with an amplitude of O(1) at small scales that are beyond the reach of current observations, such as those from the CMB and large-scale structure. Assuming a monochromatic initial power spectrum, we identify the viable parameter space defined by dark matter mass and the length scale of perturbations. A key prediction of this scenario is copious formation of subsolar dark matter halos at high redshifts.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

The second internal meeting of RIKEN Quantum

December 6 (Fri) at 16:00 - 19:30, 2024

Program: 16:00-16:05 Opening remarks --- Shinichiro Fujii (TRIP / iTHEMS) 16:05-16:35 Tensor network simulations of lattice gauge theory --- Yantao Wu (iTHEMS) 16:35-17:05 Quantum electrodynamics meets quantum chemistry: Theoretical foundations for polariton dynamics and control --- Himadri Pathak (iTHEMS / R-CCS) 17:05-17:35 Towards quantum advantage: imaginary Hamiltonian variational ansatz on the Schwinger model and the MaxCut problem --- Xiaoyang Wang (iTHEMS / R-CCS) 17:35-17:59 Researchers conducting collaborative research proposals (TRIP) --- 3 min.*8       Takaaki Kuwahara (Kyoto Univ.)       Maxime Medevielle (Univ. of Tokyo)       Tanay Pathak (Kyoto Univ.)       Koudai Sugimoto (Keio Univ.)       Takayuki Suzuki (NICT)       Hidetoshi Taya (Keio Univ.)       Takahiro Terada (Nagoya Univ.)       Tianchun Wang (Keio Univ.) 17:59-18:00 Closing remarks --- Seiji Yunoki (CPR / R-CCS / RQC) 18:10-19:30 Banquet at Cafeteria 1, Welfare and Conference Bldg (C61) 1F, RIKEN, Wako

Venue: #359, 3F, Seminar Room #359

Event Official Language: English

The Long Road towards Quantum Simulations of the Standard Model

December 6 (Fri) at 11:00 - 12:00, 2024

Dorota Grabowska (Research Assistant Professor, InQubator for Quantum Simulations (IQuS), University of Washington, USA)

The Standard Model of Particle Physics, encapsulating the vast majority of our understanding of the fundamental nature of our Universe, is at its core a gauge theory. Much of the richness of its phenomenology can be traced back to the complicated interplay of its various gauged interactions. While massive theoretical and algorithmic developments in classical computing have allowed us to probe many of these aspects, there remain a plethora of open questions that do not seem amenable to these methods. With a fundamentally different computational strategy, quantum computers hold the potential to address these open questions. However, a long road lies ahead of us before this potential may be realized. In this talk, I discuss a key step on this journey: constructing lattice gauge Hamiltonians that can be efficiently simulated on digital quantum devices. In particular, I focus on recent work that develops a fully gauge fixed Hamiltonian for SU(2) without fermions. Not only is this formulation well-suited for "close to continuum" simulations, it is also significantly less non-local than might be initially expected.

Venue: Hybrid Format (3F #359 and Zoom), Seminar Room #359

Event Official Language: English

Bacterial ecospecies and ecoclines

December 5 (Thu) at 16:00 - 17:00, 2024

Daniel Falush (Professor, Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, China)

All bacteria reproduce clonally but some species exchange DNA frequently enough that they have well mixed geographic gene pools, similar to those found in outbreeding animals and plants. Using data from multiple species we show that these “recombinogenic” bacteria also have genome-wide genetic structures generated by natural selection, including discrete “ecospecies” and continuous “ecoclines”. These structures reflect evolutionary strategies employed within natural populations, which can be dissected using the powerful techniques of molecular microbiology, providing a unique new view into the private lives of bacteria.

Venue: via Zoom / Seminar Room #359

Event Official Language: English