KEK Theory workshop 2020

Session

Invited talks

https://conference-indico.kek.jp/event/116/contributions/2520/

15 Dec 2020, 09:05

Online (Zoom)

Conveners

Invited talks: "Introduction to higher form symmetries", Yoshimasa Hidaka (KEK)

• Chair: Ryo Yokokura (KEK)

Invited talks: "Symmetry protected topological phases and generalized (co)homology theory", Ken Shiozaki (YITP)

• Chair: Ryo Yokokura (KEK)

Invited talks: "Higher-form symmetries and 3-group in axion electrodynamics", Ryo Yokokura (KEK)

• Chair: Naoki Yamamoto (Keio U.)

Invited talks: "Higher groups and topological phases of matter", Apoorv Tiwari (U. of Zurich)

• Chair: Ryo Yokokura (KEK)

Invited talks: "Dense QCD matter tackled by experiments, observations, and theory", Akira Ohnishi (YITP)

• Chair: Yoshio Kikukawa (U. of Tokyo)

Invited talks: "Exploring the QCD phase diagram with holographic models", Kouji Kashiwa (Fukuoka Inst. of Tech.)

• Chair: Yoshio Kikukawa (U. of Tokyo)

Invited talks: "Color superconductivity in lattice QCD", Jun Nishimura (KEK)

• Chair: Yoshio Kikukawa (U. of Tokyo)

Invited talks: "Universes as Bigdata: from Geometry, to Physics, to Machine-Learning", Yang-Hui He (Merton Coll., U. of Oxford)

• Chair: Koji Hashimoto (Osaka U.)

Invited talks: "The Topology of Data: from String Theory to Cosmology to Phases of Matter", Gary Shiu (U. of Wisconsin-Madison)

• Chair: Koji Hashimoto (Osaka U.)

Invited talks: "Hidden structures in the landscape of heterotic line bundle models", Hajime Otsuka (KEK)

• Chair: Koji Hashimoto (Osaka U.)

Invited talks: "Equivalence Principle, Decoupling Principle, and Information Loss Paradox", Pei-Ming Ho (NTU)

• Chair: Tamiaki Yoneya (U. of Tokyo)

Invited talks: "Black hole as a quantum field configuration", Yuki Yokokura (RIKEN)

• Chair: Nobuyoshi Ohta (Kindai U.)

Invited talks: "Entanglement between two disjoint universes", Tomonori Ugajin (YITP)

• Chair: Takeshi Morita (Shizuoka U.)

Invited talks: "What microstate geometries tell us", Masaki Shigemori (Nagoya U. & YITP)

• Chair: Yoshifumi Hyakutake (Ibaraki U.)

46. Introduction to higher form symmetries

Prof. Yoshimasa Hidaka (KEK)

15/12/2020, 09:05

I will review a basic notion of higher form symmetries, which are symmetries for extended objects such as vortices, and domain walls. As an application, we discuss spontaneous symmetry breaking of higher form symmetries, topological order, and symmetry-protected topological phases of matter.

48. Symmetry protected topological phases and generalized (co)homology theory

Prof. Ken Shiozaki (YITP)

15/12/2020, 10:50

It is discussed that the symmetry protected topological phase (SPT phase) is well described by generalized cohomology theory. Identifying the classification of SPT phases on a real-space manifold $X$ as a homology group on $X$ offers a unified understanding of SPT phenomena through the axioms and general properties of the generalized (co)homology. In this talk, I will give a brief review of...

49. Higher-form symmetries and 3-group in axion electrodynamics

Dr Ryo Yokokura (KEK)

15/12/2020, 14:30

We study higher-form symmetries in a low-energy effective theory of a massless axion coupled with a photon in $(3+1)$ dimensions. It is shown that the higher-form symmetries of this system are accompanied by a semistrict 3-group (2-crossed module) structure, which can be found by the correlation functions of symmetry generators of the higher-form symmetries. We argue that the Witten effect and...

50. Higher groups and topological phases of matter

Dr Apoorv Tiwari (U. of Zurich)

15/12/2020, 17:00

I will describe how symmetry structures appearing in quantum many-body systems can be understood within the framework of fusion categories. Quantum systems with ``higher symmetry" structures naturally appear by generalising or weakening certain axioms of these fusion categories. I will touch upon various topological aspects of higher group symmetries such as symmetry protected topological...

43. Dense QCD matter tackled by experiments, observations, and theory

Prof. Akira Ohnishi (YITP)

16/12/2020, 09:00

Dense QCD matter appears in compact astrophysical phenomena and heavy-ion collisions. Phenomenological EOS (equation of state) needs extrapolation or interpolation and has large uncertainty. Thus we need first-principles or model-independent theoretical studies, or experiments where dense QCD matter is directly probed. In this talk, I first review physics of finite density QCD from the...

44. Exploring the QCD phase diagram with holographic models

Prof. Kouji Kashiwa (Fukuoka Inst. of Tech.)

16/12/2020, 10:20

In this talk, I will explain the recent progress of understanding the QCD phase diagram based on the holographic models. Particularly, this talk concentrates on the treatment of the color superconductivity and the application of the imaginary chemical potential in the bottom-up approach. In addition, I will explain what interesting phenomena will be discussed via the bottom-up holographic models.

45. Color superconductivity in lattice QCD

Prof. Jun Nishimura (KEK)

16/12/2020, 11:20

Exploring the QCD phase diagram is known to be extremely difficult at finite density due to the sign problem, which occurs in lattice QCD calculations. We show that this problem can be overcome by the complex Langevin method in a certain parameter region at low temperature and high density. This, in particular, gives us a hope to investigate color superconductivity in lattice QCD by first...

40. Universes as Bigdata: from Geometry, to Physics, to Machine-Learning

Prof. Yang-Hui He (Merton Coll., U. of Oxford)

17/12/2020, 09:00

We briefly overview how historically string theory led theoretical physics first to algebraic/differential geometry, and then to computational geometry, and now to data science.
Using the Calabi-Yau landscape - accumulated by the collaboration of physicists, mathematicians and computer scientists over the last 4 decades - as a starting-point and concrete playground, we then launch to review...

41. The Topology of Data: from String Theory to Cosmology to Phases of Matter

Prof. Gary Shiu (U. of Wisconsin-Madison)

17/12/2020, 10:15

We are faced with an explosion of data in many areas of physics, but very so often, it is not the size but the complexity of the data that makes extracting physics from big datasets challenging. As I will discuss in this talk, data has shape and the shape of data encodes the underlying physics. Persistent homology is a tool in computational topology developed for quantifying the shape of data....

42. Hidden structures in the landscape of heterotic line bundle models

Dr Hajime Otsuka (KEK)

17/12/2020, 11:30

We show that neural networks can detect hidden structures in the string landscape, in particular, heterotic string theory on Calabi-Yau threefolds with line bundles. It turns out that three-generation models cluster in particular islands specified by deep autoencoder networks and k-means++ clustering.
Especially, we explore mutual relations between model parameters and the cluster with...

36. Equivalence Principle, Decoupling Principle, and Information Loss Paradox

Prof. Pei-Ming Ho (NTU)

18/12/2020, 09:00

We review the origin and basics of the black-hole information loss paradox, and comment on some of its potential resolutions.

37. Black hole as a quantum field configuration

Dr Yuki Yokokura (iTHEMS, RIKEN)

18/12/2020, 10:30

In quantum theory, black holes evaporate. We adopt this property as the 0th approximation and provide a field-theoretic description of black holes. To do that, we analyze time evolution of a spherical collapsing matter together with the back reaction of (pre)Hawking radiation by solving the semi-classical Einstein eq coupled with N massless scalar quantum fields. We find a 4D self-consistent...

38. Entanglement between two disjoint universes

Dr Tomonori Ugajin (YITP)

18/12/2020, 14:00

We use the replica method to compute the entanglement entropy of a universe without gravity entangled in a thermofield-double-like state with a disjoint gravitating universe. Including wormholes between replicas of the latter gives an entropy functional which includes an "island" on the gravitating universe. We solve the back-reaction equations when the cosmological constant is negative to...

57. What microstate geometries tell us

Prof. Masaki Shigemori (Nagoya U. & YITP)

18/12/2020, 15:30

Microstate geometries are smooth horizonless geometries that have the same mass and charge as a black hole. In this talk, I will review the current status of the research in microstate geometries, such as their construction, counting and lifting, and discuss their physical implications, such as evolution toward more typical microstates.