Laszlo Feher, Szeged University

Bi-Hamiltonian structures of integrable many-body models

Seminar room, Kenkyu Honkan 3F

The evolution equations of several exactly solvable dynamical systems can be written in Hamiltonian form in two distinct manners, using two different Poisson bracket structures and corresponding Hamiltonians. Such bi Hamiltonian structures lead to the existence of conserved quantities associated with the integrability of the pertinent systems. In this talk we review our results on bi-Hamiltonian structures of integrable many-body models of point particles moving along one dimension, which are also coupled to internal `spin’ degrees of freedom. The models of our interest belong to the celebrated family of Calogero–Moser–Sutherland and Toda type systems. They will be viewed as shadows (alias Poisson reductions) of simple higher dimensional bi-Hamiltonian systems having large symmetry groups.

Kohei Fujikura, Univ of Tokyo

Cosmological Phase Transitions in Composite Higgs Models

Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom

Composite Higgs models consist of four-dimensional asymptotically-free gauge field theories. Each model may lead to a confinement-deconfinement transition and a phase transition associated with the spontaneous breaking of a global symmetry that realizes the standard model Higgs field as a pseudo-Nambu-Goldstone boson. In this talk, I will discuss order of thermal phase transitions in various composite Higgs models based on the argument of universality. In particular, we focus on phase transitions associated with the global symmetry breaking by studying the renormalization group flow using the ϵ-expansion at the one-loop order.
We find that first-order phase transitions are favored in some of composite Higgs models. If I have a time, I would like to discuss the confinement-deconfinement transition in a UV-completed composite Higgs model based on a Sp(2Nc) gauge theory.

Jesse Thaler, MIT

[IPNS Physics and Theory Joint Seminar] Quarks and Gluons through the Lens of Machine Learning

Hybrid On-site: Bldg 4 Seminar Hall Online: Zoom


Tomohiro Matsuda, Saitama Institute of Technology

The Exact WKB for particle production: from baryogenesis to Hawking radiation

Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Most particle production can be solved by approximate methods, but some problems cannot be solved without serious consideration of the Stokes phenomenon. One such particle production is baryon number production from rotating fields. Processes such as particle-antiparticle mixing increase the order of the differential equations to be solved, so new knowledge of ExactWKB, including Virtual Turning Point, is required. The other is particle production from a steady state. This problem includes the Schwinger effect, the Unruh effect and Hawking radiation. In particular, the Stokes phenomenon of the Unruh effect has been unsolved for 50 years. This talk shows how the Exact WKB can be used to solve these problems clearly.

Katsuki Aoki, YITP

Towards S-matrix theory of unstable particles

Online (Zoom)
The S-matrix is one of the central objects in quantum field theory and has gained renewed interest recently to better understand the possible structures of low-energy effective field theories, strongly-coupled systems, quantum gravity, etc. However, most of the particles have finite decay widths and thus do not appear in asymptotic states. Therefore, the standard S-matrix arguments may not be directly applied to scatterings of such unstable particles and we need to formulate “the S-matrix theory of unstable particles” to properly understand the availability of the S-matrix arguments in realistic systems. In this talk, I will talk about some progress towards this goal. In particular, I will discuss non-perturbative consequences of unitarity in scattering amplitudes of unstable particles and their analytic properties.

Philipp Gubler, JAEA

[QCD theory seminar] The phi meson in-medium polarization modes from theory and experiment

Online (Zoom)

While the phi meson vacuum properties, such as mass and width, are well known, it is not clear how these properties will change once it is put in a dense environment such as nuclear matter. To study how the phi meson behaves at finite density has been the goal of several past and near future experiments at KEK, COSY-ANKE and J-PARC. Recently, ALICE has also obtained novel experimental data constraining the phi-N interaction. In this talk, I will focus on the in-medium properties of the longitudinal and transverse polarization modes of the phi meson, which due to the breaking of Lorentz symmetry in nuclear matter, can be modified differently. I will review theoretical predictions for these modifications and discuss how the different modes could be measured at the future J-PARC E16 and E88 experiments.

William DeRocco, UC Santa Cruz

Searching for Gravitational Waves Below a Nanohertz

Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Gravitational waves with frequencies below 1 nHz are notoriously difficult to detect and fall below the typical cutoff frequency for conventional pulsar timing analyses. In this talk, I will present a new means of probing this regime through the correlation of secular drifts in pulsar timing parameters. I will show the results of searches for both continuous and stochastic signals in this regime and will discuss what future observations using this methodology may reveal about the signal recently discovered by pulsar timing collaborations at frequencies above a nanohertz.

Jochen Heitger, Westfaelische Wilhelms-Universitaet Muenster

Precision heavy flavour physics through lattice QCD with Wilson quarks.

Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
In heavy flavour physics, the D- and B-meson sectors continue to be promising realms for precision tests of the Standard Model,where evidence of New Physics can be expected. Lattice QCD offers a powerful ab initio framework to reliably calculate the low-energy hadronic amplitudes, which are crucial for the determination of CKM matrix elements, and thus to significantly reduce the uncertainties of the theory inputs to such tests. This talk presents results on the leptonic D-meson decay constants obtained from a large number of (2+1)-flavour ensembles with O(a) improved Wilson quarks by CLS (including two ensembles at the physical point), spanning 6 lattice spacings down to 0.039 fm and lying on 3 trajectories in the quark mass plane. This allows achieving a phenomenologically relevant precision, while demonstrating control over important sources of systematic uncertainties such as discretisation effects and the quark mass dependence. The second part discusses a strategy how to combine interpolations between relativistic and static computations with a step scaling approach, in order to extract heavy-light B-physics observables in the continuum. We report first numerical results for the b-quark mass and leptonic decay constants from a subset of CLS ensembles and outline how this strategy also applies to semi-leptonic form factors.

大谷将士, KEK

[金茶会] 第4回 ミューオン冷却・加速技術の現在と展望

東海:AQBRC2階会議室 (リモート会場:小林ホール)


Okuto Morikawa, Osaka University

Lattice description of generalized symmetries and topological phenomena

Hybrid On-site: Kenkyu Honkan Seminar room 321, 322 Online: Zoom
Recently, the notion of symmetry is generalized so that we can get further information on low-energy dynamics in strongly coupled field theories. This is described in terms of topological operators and also category. It would be crucial that topology of gauge fields is nontrivial in a fully regularized framework; e.g., continuity appears to be lost under lattice regularization. L¥”uscher addressed this issue for $SU(2)$ gauge fields and defined the topological charge on a lattice explicitly. We apply L¥”uscher’s construction to generalized symmetries. We consider lattice $SU(N)$ gauge theories coupled with $¥mathbb{Z}_N$ $ 2$-form gauge fields, and show the fractionality of the topological charge on $SU(N)/¥mathbb{Z}_N$ principal bundle. Also the mixed ‘t Hooft anomaly and higher-group structure are realized. We become interested in monopole physics as a topological phenomenon on the lattice.

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