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2022 Fiscal Year Final Research Report

Phase diagram and superfluidity of two-color QCD in the low-temperature high-density regime

Research Project

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Project/Area Number 19K03875
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Review Section Basic Section 15010:Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
Research InstitutionInstitute of Physical and Chemical Research (2021-2022)
Kyoto University (2020)
Keio University (2019)

Principal Investigator

Itou Etsuko  国立研究開発法人理化学研究所, 数理創造プログラム, 上級研究員 (50432464)

Project Period (FY) 2019-04-01 – 2023-03-31
Keywords有限密度QCD / QCDの状態方程式 / QCD相図 / 第一原理計算
Outline of Final Research Achievements

We have investigated the finite-density regime of 2-color QCD using lattice simulations and discovered new phenomena in the finite-temperature regime of QCD-tlike theories. We focused on the challenging region of low-temperature and high-density and first examined its phase diagram. As the density increases, we found the existence of the hadron phase, hadronic-matter phase, and superfluid phase. Within the superfluid phase, we also identified the presence of the Bose-Einstein condensate phase and the BCS phase. Furthermore, by using the gradient flow method, we explored the topological charge and obtained novel results indicating a relatively large topological susceptibility even in high-density regions. Furthermore, we investigated the density dependence of thermodynamic quantities such as energy and pressure, revealing a new finding that the speed of sound exceeds the value of the conformal limit (c/sqrt(3)) in the BCS phase.

Free Research Field

素粒子理論

Academic Significance and Societal Importance of the Research Achievements

3カラーの低温高密度QCDは、中性子星の内部で実現されていると考えられており、その性質の解明は宇宙・原子核・素粒子分野において大きな課題となっている。また、そこではQCDの物質は、超流動状態になっていると考えられており、物性としても興味深い。しかしながら、理論的には格子QCDの第一原理計算が付合問題により実行不可能である。
我々は、カラーの自由度を一つ落として符号問題の生じない理論で第一原理計算をおこなった。2カラーQCDは少なくともゼロ密度で3カラーと同じ性質を持つ。我々のいくつかの新しい結果は3カラーの高密度現象にさまざまな制限を与え、その理解への足掛かりとなった。

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Published: 2024-01-30  

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