Michio Kohno, RCNP, Osaka university
[EX] Baryon-baryon interactions in chiral effective field theory
Online (Zoom), indico page, slides (kek.jp only) Over the last two decades, the description of nucleon-nucleon (NN) interaction in chiral effective field theory has progressed. Based on the symmetry of QCD, together with the properties such as the precision equal to or better than other modern NN potentials for reproducing NN scattering data and the possibility of introducing more than three-body interactions in a systematic way, the ChEFT NN potentials now play a central role in the first-principle investigations of nuclear structure and reactions by using various methods of quantum many-body theory that have been developed around the same period. The ChEFT method is also applied to interactions in the strangeness sector. The seminar outlines the construction of the baryon-baryon interactions in chiral effective field theory.
Over the last two decades, the description of nucleon-nucleon (NN) interaction in chiral effective field theory has progressed. Based on the symmetry of QCD, together with the properties such as the precision equal to or better than other modern NN potentials for reproducing NN scattering data and the possibility of introducing more than three-body interactions in a systematic way, the ChEFT NN potentials now play a central role in the first-principle investigations of nuclear structure and reactions by using various methods of quantum many-body theory that have been developed around the same period. The ChEFT method is also applied to interactions in the strangeness sector. The seminar outlines the construction of the baryon-baryon interactions in chiral effective field theory.
・The idea of effective theory, and the general theory of effective interaction in a restricted space
・Chiral effective field theory (ChEFT)
・Parametrization of NN potentials in ChEFT
・Baryon-baryon potentials in the strangeness sector
・Comment: Present ChEFT NLO Xi-N interactions in view of the J-PARC E07 experiment
Sabyasachi Chakraborty, Florida State University
Heavy QCD axions in B decays
Online (Zoom)
We study B->Ka transition as a powerful probe of the heavy QCD axion (mass~GeV) by performing necessary 2-loop calculations for the first time. Such an axion is kinematically inaccessible or poorly constrained by most experimental probes. We will discuss some interesting subtleties of our calculation and present limits and projections on the axion parameter space using B-physics results.
Jay Armas, University of Amsterdam
Topological hydrodynamic modes on curved surfaces
Online (Zoom), indico page, slides (kek.jp only)
I will review the usage of topological methods in the case of the Dirac fermion and their role in predicting trapped edge modes. I will then show that these methods can be applied to classical systems, in particular to hydrodynamic systems that describe a broad range of phenomena, from geophysical waves to waves in topologically non-trivial soft matter experiments. Some of these system include activity (i.e. self-propelled organisms within the fluid). In particular, I will derive an index theorem that relates the topology of Fourier space determined by the underlying Hamiltonian with the real space topology of the surface in which the waves are hosted. At the end, I will give details about how the same methods can be applied to high energy physics, in particular to astrophysics and the AdS/CFT correspondence.
Noriyuki Sogabe, KEK / Institute of Moden Physics, CAS
Topological color-superconductivity in QCD with one flavor
Online (Zoom) https://kds.kek.jp/event/37256/ Superconductive gaps have topologically protected nodal structure if the fermions form the inter-chiral Cooper pair [1]. We generalize this Li and Haldane’s argument to the color superconductivity in QCD with one flavor. Among several order parameters with different spins and colors [ 2], we show that the nodes in the phases with a simple color-spin structure have the vortices characterized by the Berry monopoles, similarly to the previous literature. On the other hand, the paring function has no nodes if the color and spin degrees of freedom are entangled, such as in the ground state called the color-spin locking (CSL) phase. Even in this case, we find a non-trivial Berry curvature defined by the gap eigenvectors in the color-spin space. The CSL phase has an emergent Weyl fermion characterized by the doubled monopole charges as a quasi-particle. We discuss its possible relevance to the topological phase diagram of QCD with one flavor.
Superconductive gaps have topologically protected nodal structure if the fermions form the inter-chiral Cooper pair [1]. We generalize this Li and Haldane’s argument to the color superconductivity in QCD with one flavor. Among several order parameters with different spins and colors [ 2], we show that the nodes in the phases with a simple color-spin structure have the vortices characterized by the Berry monopoles, similarly to the previous literature. On the other hand, the paring function has no nodes if the color and spin degrees of freedom are entangled, such as in the ground state called the color-spin locking (CSL) phase. Even in this case, we find a non-trivial Berry curvature defined by the gap eigenvectors in the color-spin space. The CSL phase has an emergent Weyl fermion characterized by the doubled monopole charges as a quasi-particle. We discuss its possible relevance to the topological phase diagram of QCD with one flavor.
[1] Yi Li and F. D. M. Haldane, “Topological nodal Cooper pairing in doped Weyl metals,” Phys. Rev. Lett. 120, 067003 (2018).
[2] T. Sch?fer, “Quark hadron continuity in QCD with one flavor,” Phys. Rev. D 62, 094007 (2000).
Kazuki Ikeda, Osaka University / Kyocera
Real-time dynamics of Chern-Simons fluctuations near a critical point
Online (Zoom), indico page, slides (kek.jp only)
The real-time Chern-Simons diffusion rate is studied in (1+1)-dimensional massive Schwinger model with a ¥theta-term. We evaluate the real-time correlation function of electric field that represents the topological Chern-Pontryagin number density in (1+1) dimensions. Near the parity-breaking critical point located at ¥theta = ¥pi and fermion mass m to coupling g ratio of m/g ¥approx 0.33, we observe a sharp maximum in the Chern-Simons diffusion rate. We interpret this maximum in terms of the growth of critical fluctuations near the critical point, and draw analogies between the massive Schwinger model, QCD near the critical point, and ferroelectrics near the Curie point.
Anthony Ashmore, University of Chicago
Calabi-Yau metrics, machine learning, and the spectrum of the Laplace operator
Online (Zoom) https://kds.kek.jp/event/37101/
Calabi-Yau manifolds have played a role in advances in both mathematics and physics, and are particularly important for deriving realistic models of particle physics from string theory. Unfortunately, very little is known about the explicit metrics on these spaces, other than for tori, leaving us unable to compute particle masses or couplings in these models. In this talk I will discuss the numerical methods available for computing these metrics and review recent progress on using machine learning to find these metrics. Using this numerical ‘data’ of the metric, I will compute the spectrum of the Laplace operator acting on (p,q)-forms, taking a crucial step towards computing masses and couplings in physically relevant theories.
Tomas Brauner, University of Stavanger
Higher-group symmetry in (generalized) superfluid mixtures
Online (Zoom), slides (kek.jp only)
In recent years, the notion of global higher-group symmetry has emerged, which brings together ordinary (0-form) and higher-form global symmetries in a more general mathematical structure. Previously, it has been shown that a nontrivial higher-group structure can be triggered by an underlying mixed ’t Hooft anomaly or by a topological coupling of different sectors of the theory. Starting with an elementary review of higher-form symmetry, I will explain how this naturally leads to a new class of systems featuring higher-group symmetry. The niche in which such symmetries occur is that of multicomponent generalized p-form superfluids. The higher-group structure arises from the Grassmann algebra of topological currents of the superfluid.
Tadashi Takayanagi, YITP, Kyoto University
Path-Integral Optimization from Hartle-Hawking Wave Function
Online (Zoom) https://kds.kek.jp/event/37100/
We propose a gravity dual description of the path-integral optimization in conformal field theories arXiv:1703.00456, using Hartle-Hawking wave functions in anti-de Sitter spacetimes. We show that the maximization of the Hartle-Hawking wave function is equivalent to the path-integral optimization procedure. Namely, the variation of the wave function leads to a constraint, equivalent to the Neumann boundary condition on a bulk slice, whose classical solutions reproduce metrics from the path-integral optimization in conformal field theories. After taking the boundary limit of the semi-classical Hartle-Hawking wave function, we reproduce the path-integral complexity action in two dimensions as well as its higher and lower dimensional generalizations. We also discuss an emergence of holographic time from conformal field theory path-integrals.
Takahiko Matsubara, KEK
[Cosmophysics seminar] The Statistics of Peaks of Weakly Non-Gaussian Fields
Online (Zoom), slides (kek.jp only)
The peaks in the cosmic fields have been attracting a lot of interest in the analysis of cosmological fields. In this talk, analytic formulas for the abundance and correlation of peaks in the presence of weak non-Gaussianity are newly derived and presented in N dimensions with N=1,2,3. These formulas provide theoretical methods for the analysis of peak statistics in cosmological fields, such as the galaxy density field or the weak lensing field, etc.
Wen Yin, University of Tokyo
Messengers of reheating phase and their spectra
Online (Zoom), indico page, slides (kek.jp only) After inflation, the Universe presumably undergoes a phase of reheating which in effect starts the thermal big bang cosmology. However, so far we have very little direct experimental or observational evidence of this important phase of the Universe. I would like to argue that measuring the spectrum of freely propagating relativistic particles produced during reheating may provide us with powerful information on the reheating phase. To demonstrate this possibility, we first discuss which kind of (SM,BSM) particle can play the role of the messenger of reheating. Then we show that the spectrum crucially depends on whether the mother non-relativistic particle once dominated the Universe or not.
