Miguel Vazquez-Mozo, Universidad de Salamanca
Planar Zeros in Field and String Theory Amplitudes
Meeting room 3, Kenkyu honkan 1F, slides (kek.jp only)
Planar zeros are an interesting feature of certain scattering amplitudes with one or more gauge bosons radiated, consisting in the vanishing of the amplitude for configurations where all momenta lie on a single plane. In this talk I shall study these planar zeros in various field theories at tree-level. In the case of theories with gauge invariance, the zeros are determined by the vanishing of a homogeneous polynomial in the stereographic coordinates determining the direction of flight of the particles involved. This projective property is absent in pure scalar theories. In gravitational theories, on the other hand, amplitudes vanish whenever the scattering is planar. String theory corrections to the field theory amplitudes spoil the projective nature of gauge planar zeros, as well as the vanishing of gravitational planar amplitudes.
中村孝明, 高知工科大学
グラフ上の非線形シュレディンガー方程式
Seminar room, Kenkyu honkan 3F 非線形シュレディンガー方程式 (Nonlinear Schrödinger equation)は、ボーズ＝アインシュタイン凝縮系を記述すると同時に、渦糸、光ファイバー中パルス波等の様々な物理系にも現れる。近年、単純な系であるグラフ上での非線形シュレディンガー方程式の研究が盛んになっている。この講演では、非線形シュレディンガー方程式の基礎的性質の解説とともに、フロップ筒井型点欠陥を課したリング上での系の固有値の安定性の議論を紹介する。またこの系の数値的な解析から得られた、順位交差や反発、新奇量子ホロノミーやベリー位相の存在について論じ、さらには、線形系には見られないエネルギー準位の一部消滅といった現象についても解説する。
非線形シュレディンガー方程式 (Nonlinear Schrödinger equation)は、ボーズ＝アインシュタイン凝縮系を記述すると同時に、渦糸、光ファイバー中パルス波等の様々な物理系にも現れる。近年、単純な系であるグラフ上での非線形シュレディンガー方程式の研究が盛んになっている。この講演では、非線形シュレディンガー方程式の基礎的性質の解説とともに、フロップ筒井型点欠陥を課したリング上での系の固有値の安定性の議論を紹介する。またこの系の数値的な解析から得られた、順位交差や反発、新奇量子ホロノミーやベリー位相の存在について論じ、さらには、線形系には見られないエネルギー準位の一部消滅といった現象についても解説する。
References:T.Nakamura, T. Cheon, “Spectral properties of nonlinear Schro dinger equation on a ring” to be published in J. Phys. Soc. Jpn. (arXiv: 1706.08695)
Masazumi Honda, Weizmann Institute of Science
Recent progress on resurgence
Meeing room 1, Kenkyu honkan 1F I will review recent progress on a resummation technique called “resurgence”, which has received much attention in the past 5 years in the context of weak coupling perturbative series in quantum field theory. I will begin with general expectation on perturbative series in quantum field theory and explain an idea of resurgence with some simple examples. Then I will ask whether we can apply resurgence to interesting quantum field theories such as QCD.
I will review recent progress on a resummation technique called “resurgence”, which has received much attention in the past 5 years in the context of weak coupling perturbative series in quantum field theory. I will begin with general expectation on perturbative series in quantum field theory and explain an idea of resurgence with some simple examples. Then I will ask whether we can apply resurgence to interesting quantum field theories such as QCD.
Although this is still open question, I will discuss what should be done to answer this question and introduce recent ideas, which may be useful for this problem.
Masaru Hongo, RIKEN
Relativistic hydrodynamics from quantum field theory
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only) Hydrodynamics is a low-energy effective theory which describes a long-distance and long-time behavior of many-body systems. It is applicable not only to a non-relativistic weakly-interacting dilute gas but also a relativistic strongly-interacting dense liquid such as the quark-gluon plasma created in ultra relativistic heavy-ion collision experiments. Although relativistic hydrodynamics itself is well-established formalism, its foundation from underlying microscopic theories, or quantum field theories, remains unclear. In this study, based on the recent development of non-equilibrium statistical mechanics, we provide the field-theoretical derivation of the relativistic Navier-Stokes equation [1]. We show that the procedure to derive hydrodynamic equations is similar to the so-called renormalized/optimized perturbation theory. Furthermore, we give a path-integral formula for local thermal equilibrium which results in the emergence of thermally induced curved spacetime [2]. Based on these results, we perform the derivative expansion and derive the first-order hydrodynamic equation (the Navier-Stokes equation) with the Green-Kubo formulas for transport coefficients.
Hydrodynamics is a low-energy effective theory which describes a long-distance and long-time behavior of many-body systems. It is applicable not only to a non-relativistic weakly-interacting dilute gas but also a relativistic strongly-interacting dense liquid such as the quark-gluon plasma created in ultra relativistic heavy-ion collision experiments. Although relativistic hydrodynamics itself is well-established formalism, its foundation from underlying microscopic theories, or quantum field theories, remains unclear. In this study, based on the recent development of non-equilibrium statistical mechanics, we provide the field-theoretical derivation of the relativistic Navier-Stokes equation [1]. We show that the procedure to derive hydrodynamic equations is similar to the so-called renormalized/optimized perturbation theory. Furthermore, we give a path-integral formula for local thermal equilibrium which results in the emergence of thermally induced curved spacetime [2]. Based on these results, we perform the derivative expansion and derive the first-order hydrodynamic equation (the Navier-Stokes equation) with the Green-Kubo formulas for transport coefficients.
References:
[1] T. Hayata, Y. Hidaka, M. Hongo, and T. Noumi, Phys. Rev. D 92, 065008 (2015)
[1] M. Hongo, Annals of Physics, 383, 1 (2017)
Ippei Danshita, YITP Kyoto University
A proposal for experimental realization of the Sachdev-Ye-Kitaev model with ultracold gases
Seminar room, Kenkyu honkan 3F The Sachdev-Ye-Kitaev (SYK) model consists of Q fermions with an all-to-all random two-body hopping [1,2]. Its static state is a non-Fermi liquid with nonzero entropy at vanishing temperature, which is called the Sachdev-Ye (SY) state [3]. Since the SY state has been conjectured to be holographically dual to charged black holes with two-dimensional anti-de Sitter horizons, the SYK model has attracted much attention as a new theoretical tool for studying quantum gravity (see, e.g., Ref. [4]). In this work, we propose a possible route for realizing the SYK model experimentally with use of ultracold gases in optical lattices [5]. We also show how to measure out-of-time-order correlators of the SYK model, which may allow for capturing one of the most crucial characteristics of a black hole, namely maximally chaotic property.
The Sachdev-Ye-Kitaev (SYK) model consists of Q fermions with an all-to-all random two-body hopping [1,2]. Its static state is a non-Fermi liquid with nonzero entropy at vanishing temperature, which is called the Sachdev-Ye (SY) state [3]. Since the SY state has been conjectured to be holographically dual to charged black holes with two-dimensional anti-de Sitter horizons, the SYK model has attracted much attention as a new theoretical tool for studying quantum gravity (see, e.g., Ref. [4]). In this work, we propose a possible route for realizing the SYK model experimentally with use of ultracold gases in optical lattices [5]. We also show how to measure out-of-time-order correlators of the SYK model, which may allow for capturing one of the most crucial characteristics of a black hole, namely maximally chaotic property.
[1] A. Y. Kitaev, “A simple model of quantum holograpy”, KITP string seminar and Entanglement 2015 program (Feb. 12, April 7, and May 27, 2015). http://online.kitp.ucsb.edu/online/entangled15/.
[2] S. Sachdev, Phys. Rev. X 5, 041025 (2015).
[3] S. Sachdev and J. Ye, Phys. Rev. Lett. 70, 3339 (1993).
[4] J. Maldacena and D. Stanford, Phys. Rev. D 94, 106002 (2016).
[5] I. Danshita, M. Hanada, and M. Tezuka, arXiv:1606.02454v2 [cond-mat.quant-gas], to appear in PTEP.
Jianwei Qiu, Jefferson Lab
Explore hadron structure from the first principle lattice QCD calculations
Seminar room, Kenkyu honkan 3F
Parton distribution and correlation functions describe the relation between a hadron and the quarks and gluons (or partons) within it, and carry rich information on hadron’s partonic structure. They cannot be calculated by QCD perturbation theory, and have been extracted from experimental data of high energy scattering cross sections with the aid of QCD factorization. Parton distribution functions are the simplest of all correlation functions. Without them, we would not be able to understand the hard probes in hadronic collisions, including the Higgs discovery at the LHC. In this talk, I will discuss how can the QCD factorization help extract the same parton distribution and correlation functions from various “lattice cross sections” – hadron matrix elements that can be systematically calculated by using lattice QCD techniques. With the ab initio lattice QCD calculations, complementary to the experimental measurements, I argue that we are entering a new era of exploring hadron’s internal structure in terms of the dynamics of quarks and gluons.
Heng-Yu Chen, National Taiwan University
Aspects of Spinning CFT correlators and Witten Diagrams
Seminar room, Kenkyu honkan 3F
In this talk, we begin by reviewing the basic of CFT correlation functions for operators with spins and the structures of their holographic duals: Spinning Witten Diagrams. I will then talk about so-called “Spinning Geodesic Witten Diagrams” (SGWDs), proposed to be the holographic dual configuration of spinning conformal partial waves, from the perspectives of CFT operator product expansions. To this end, we explicitly consider three point SGWDs which are natural building blocks of all possible four point SGWDs, discuss their gluing procedure through integration over spectral parameter, and this leads us to a direct identification with the integral representation of CFT conformal partial waves. If the time allows, I will also wrap up the seminar with some on-going work for construct so-called Mellin amplitudes for spinning fields. The contents of this talk will be based on work collaborated with En-Jui Kuo and Hideki Kyono.
Masahito Yamazaki, Kavli IPMU
From 4d Yang-Mills to 2d CP^{N−1} model: IR problem and confinement at weak coupling
Seminar room, Kenkyu honkan 3F
It has been a long-standing problem to analytically prove confinement of pure Yang-Mills theory. One possible scenario is to start with the weakly-coupled region, obtain the trans-series expansion with respect to gauge coupling constant, and then continue back to the strongly-coupled region, with the help of mathematics of “resurgence”. The program has been pursued mostly on the geometry R^3 x S^1, however there the trans-series expansion could be spoiled by IR divergences. In this talk we discuss 4d SU(N) Yang-Mills theory on R×T^3, with twisted boundary condition eliminating IR zero modes. By connecting the 4d Yang-Mills theory to 2d CP^{N-1}-model, we find that the fractional instantons connecting N vacua of the CP^{N-1}-model dynamically restores center symmetry. This talk is based on arXiv:1704.05852, in collaboration with Kazuya Yonekura.
Takayuki Saito, ICRR, The University of Tokyo
[Cosmophysics group seminar] γ-ray pulsar
Meeting room1, Kenkyu honkan 1F, slides (kek.jp only)
Thanks to the successful operations of Fermi-LAT and MAGIC telescopes, the emission mechanism of gamma-ray pulsars has been getting clearer in the last 10 years. The number of detecter pulsars has increased from less than 10 to more than 200, and those emission can be basically explained as the Curvature radiation from the Outer Gap. On the other hand, new problems have also been found. For example, very high energy emission from the Crab pulsar could not be explained by the Curvature radiation. In this seminar, I will talk about the basic models of gamma-ray pulsar and observational and theoretical progress in the last 10 years, together with the future prospect of CTA observations.
Zhi-zhong Xing, IHEP Beijing
On the neutrino mass ordering and mu-tau reflection symmetry breaking
Meeting room 1, Kenkyu honkan 1F
