KEK Theory Workshop 2022

Session

Parallel session A

7 Dec 2022, 14:20

Online (Zoom)

Conveners

Parallel session A

• Kohtaro Miura (KEK)

Parallel session A

• Sota Nakajima (KEK)

Parallel session A

• Sota Nakajima (KEK)

Parallel session A

• Kohta Hatakeyama (KEK)

1. Solitonic symmetry beyond homotopy: invertibility from bordism and non-invertibility from TQFT

Mr Shi Chen (The University of Tokyo)

07/12/2022, 14:20

Solitonic symmetry is believed to follow the homotopy-group classification of topological solitons. Here, we point out a more sophisticated algebraic structure when solitons of different codimensions coexist in the spectrum. We uncover this phenomenon in a concrete quantum field theory, the $4$d $\mathbb{C}{P}^1$ model. This model has two kinds of solitonic excitations, vortices and hopfions,...

2. Unstable Nambu-Goldstone modes

Dr Ryo Yokokura (KEK)

07/12/2022, 14:40

Nambu-Goldstone (NG) modes for 0-form and higher-form symmetries can become unstable in the presence of background fields. The examples include the instability of a photon with a time-dependent axion background or with a chirality imbalance, known as the chiral plasma instability, and the instability of a dynamical axion with a background electric field. We show that all these phenomena can be...

3. Formation of chiral soliton lattice

Dr Kentaro Nishimura (KEK)

07/12/2022, 15:00

The Chiral Soliton Lattice (CSL) is a lattice structure composed of domain walls aligned in parallel at equal intervals, which is energetically stable in the presence of a background magnetic field and a finite (baryon) chemical potential due to the topological term originated from the chiral anomaly. We study its formation from the vacuum state, with describing the CSL as a layer of...

4. Boson-fermion duality with subsystem symmetry

Mr Weiguang Cao (Kavli IPMU, University of Tokyo)

07/12/2022, 15:20

In this talk, I will introduce an exact duality in (2 + 1)d between the fermionization of a bosonic theory with a $Z_2$ subsystem symmetry and a fermionic theory with a $Z_2$ subsystem fermion parity symmetry. A typical example is the duality between the fermionization of the plaquette Ising model and the plaquette fermion model. I will establish the exact duality on the lattice by using the...

5. Scalar, fermionic and supersymmetric field theories with subsystem symmetries

Mr Taiichi Nakanishi (YITP, Kyoto Univ.)

07/12/2022, 15:40

It is known that the field-theoretic model describing fractons, which have attracted much attention in condensed matter physics, is a theory with non-Lorentz covariant symmetry, called subsystem symmetry. More recently, a fermionic field theory that seems to be related to fractons has been constructed. In this presentation, we discuss detailed properties of these field theories.

12. The emergence of (3+1)-dimensional space-time in the type IIB matrix model

Dr Kohta Hatakeyama (KEK)

08/12/2022, 14:00

We perform numerical studies of the type IIB matrix model, which was proposed as a nonperturbative formulation of superstring theory in 1996. We overcome the sign problem by using the complex Langevin method and show that it is necessary to add a term corresponding to infrared regularization to the action of the original model. By these procedures, we find the (3+1)D expanding space-time in this model.

13. Bond-weighting method for the Grassmann tensor renormalization group

Prof. Shinichiro Akiyama (The University of Tokyo)

08/12/2022, 14:20

Recently, the tensor network description with bond weights on its edges has been proposed as a novel improvement for the tensor renormalization group (TRG). The bond weight is controlled by a single hyperparameter, whose optimal value is estimated in the original work via the numerical computation of the two-dimensional critical Ising model. We develop this bond-weighted TRG algorithm to make...

14. Path Integral and Phase Space Dynamics of U(1) Quantum Pendulum

Prof. Tetsuo Matsui (Kindai University)

08/12/2022, 14:40

We study the time dependent behavior of a quantum pendulum by path-integral and Wigner-Weyl phase space quantum mechanics. In both cases, we encounter a negative sign problem, and propose certain approximation similar to the truncated Wigner approximation, which sheds some light on the sign problem.

15. Bounds on expectation values in Quantum mechanics

Prof. Takeshi Morita (Shizuoka University)

08/12/2022, 15:00

The range of motion of a particle with certain energy $E$ confined in a potential is determined from the energy conservation law in classical mechanics. The counterpart of this question in quantum mechanics can be thought of as what the possible range of the expectation values of the position operator $⟨x⟩$ of a particle, which satisfies $E=⟨H⟩$. This range would change depending on the state...

16. Real-time evolution of quantum tunneling via the thimble approach

Dr Atis Yosprakob (Niigata University)

08/12/2022, 15:40

Quantum tunneling has been playing an important role in various fields of theoretical physics. So far, the only way for us to gain insights into the mechanism is to use the instanton method, which is based on imaginary-time formalism. However, to study its dynamics, it is essential to use real-time formalism, whose path integral is highly oscillatory. Fortunately, Picard-Lefschetz theory can...

17. Exact solution of the finite Grosse-Wulkenhaar model

Mr Naoyuki Kanomata (Tokyo University of Science)

08/12/2022, 16:00

We find the exact solutions of the ${\mathrm{\Phi }}_2^3$ finite matrix model (Grosse-Wulkenhaar model). In the ${\mathrm{\Phi }}_2^3$ finite matrix model, multipoint correlation functions are expressed as $G_{|a_1^1\dots a_{N_1}^1|\dots |a_1^B\dots a_{N_B}^B|}$. The $\sum _{i=1}^B{N}_i$-point function denoted by $G_{|a_1^1\dots a_{N_1}^1|\dots |a_1^B\dots a_{N_B}^B|}$ is...

18. Nucleon D-term in holographic QCD

Dr Mitsutoshi Fujita (Sun Yat-Sen University)

08/12/2022, 16:20

The D-term is one of the conserved charges of hadrons defined as the forward limit of the gravitational form factor D(t). We calculate the nucleon’s D-term in a holographic QCD model in which the nucleon is described as a soliton in five dimensions. We show that the form factor D(t) is saturated by the exchanges of infinitely many 0++ and 2++ glueballs dual to transverse-traceless metric...

26. Entropy and its conservation in expanding Universe

Prof. Shinya Aoki (Yukawa Institute for Theoretical Physics, Kyoto University)

09/12/2022, 14:00

We investigate properties of the conserved charge in general relativity, recently proposed by one of the present authors with his collaborators, in the inflation era, the matter dominated era and the radiation dominated era of the expanding Universe. We show that the conserved charge becomes the Bekenstein-Hawking entropy in the inflation era, and it becomes the matter entropy and the...

27. Entropy constraints on effective field theory

Dr Daiki Ueda (Peking University)

09/12/2022, 14:20

In effective field theory, the positivity bounds of higher derivative operators are derived from analyticity, causality, and unitarity. We show that the positivity bounds on a class of effective field theories, e.g., dimension-eight term of a single massless scalar field, the Standard Model Effective Field Theory dimension-eight $SU(N)$ gauge bosonic operators, and Einstein-Maxwell theory with...

28. No Smooth Beginning for The Universe and Trans-Planckian Physics

Dr Hiroki Matsui (Yukawa Institute for Theoretical Physics, Kyoto University)

09/12/2022, 14:40

In minisuperspace quantum cosmology, the Lorentzian path integral formulations of the no-boundary and tunneling proposals have recently been analyzed, but it has been pointed out that the wave function of linearized perturbations around a homogeneous and isotropic background is of an inverse Gaussian form and thus that their correlation functions are divergent. In this talk, I will discuss the...

29. Numerical study of quantum cosmology by the generalized Lefschetz thimble method

Mr Chien Yu Chou (SOKENDAI)

09/12/2022, 15:00

Quantum cosmology is established as a way to understand the beginning of universe. Picard-Lefschetz theory has raised recent interest on the “tunneling from nothing” proposal by Vilenkin and the “no boundary” proposal by Hartle-Hawking. The two proposals can be closely related through analysis on saddle points and boundary conditions. In this work, we demonstrate a first principle calculation...

30. Path integrals of perturbative strings on all the curved backgrounds from string geometry theory and a potential energy of the backgrounds

Prof. Matsuo Sato (Hirosaki University)

09/12/2022, 15:20

One perturbative string theory is defined on one fixed background. On the other hand, it is necessary that a non-perturbative formulation of string theory includes all the perturbatively stable vacua and perturbative string theories on various curved backgrounds are derived from the single theory. In this talk, we derive perturbative string theories on all the curved backgrounds from the...