Keio University · 물리·천문학
나오키 ヤマモ토 교수의 연구실은 양자물리학과 고체물리학의 기초 원리에서 비롯되는 '키랄성' 현상에 초점을 맞추며, 특히 페르미온 시스템의 정상 상태에서의 전류 금지 원리인 블로흐 정리의 일반화를 통해 양자물리학적 현상이 거시적 현상으로 나타나는 메커니즘을 연구합니다. 주요 연구 분야는 양자색역학, 양자장론, 그리고 천체물리학에서의 키랄 운동량 및 전류 효과로, 핵심적으로는 초신성 폭발, 밀도 높은 핵물질, 중성자별 등 극한 조건에서의 키랄 수송 현상과 그 유체역학적 영향을 다룹니다. 특히 중성자별과 초신성에서의 자기장 생성, 편극화된 중성자기류, 그리고 초기우주의 입자 생성 메커니즘 등 천체물리학적 응용에 깊이 기여하고 있습니다.
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Bloch theorem states the impossibility of persistent electric currents in the ground state of nonrelativistic fermion systems. We extend this theorem to generic systems based on the gauged particle number symmetry and study its consequences on the example of chiral transport phenomena. We show that the chiral magnetic effect can be understood as a generalization of the Bloch theorem to a nonequilibrium steady state, similarly to the integer quantum Hall effect. On the other hand, persistent axia
Chirality of neutrinos modifies the conventional kinetic theory and hydrodynamics, leading to unusual chiral transport related to quantum anomalies in field theory. We argue that these corrections have new phenomenological consequences for hot and dense neutrino gases, especially in core-collapse supernovae. We find that the neutrino density can be converted to the fluid helicity through the chiral vortical effect. This fluid helicity effectively acts as a chiral chemical potential for electrons
Using a general Ginzburg-Landau effective Lagrangian, we study the topological structure and low-lying collective modes of dense QCD having both chiral and diquark condensates, for two and three massless flavors. As we found earlier, the QCD axial anomaly acts as an external field applied to the chiral condensate in a color superconductor and, as a new critical point emerges, leads to a crossover between the broken chiral symmetry and color superconducting phases. At intermediate densities where
We study the turbulent regime of chiral (magneto)hydrodynamics for charged and neutral matter with chirality imbalance. We find that the chiral magnetohydrodynamics for charged plasmas possesses a unique scaling symmetry, only without fluid helicity under the local charge neutrality. We also find a different type of unique scaling symmetry in the chiral hydrodynamics for neutral matter with fluid helicity in the inertial range. We show that these symmetries dictate the self-similar inverse casca
The microscopic quantum nature of elementary particles, chirality, leads to macroscopic phenomena like the chiral anomaly, chiral magnetic effect, and chiral plasma instability. We review recent progress of the studies of these chiral effects in high-energy astrophysics, such as pulsar kicks, magnetars, and core-collapse supernovae, and early Universe cosmology, such as the primordial magnetic field, baryogenesis, and chiral gravitational waves. We also provide a pedagogical introduction to the
We study the hydrodynamic regime of chiral plasmas at high temperature. We find a new type of gapless collective excitation induced by chiral effects in an external magnetic field. This is a transverse wave, and it is present even in incompressible fluids, unlike the chiral magnetic and chiral vortical waves. The velocity is proportional to the coefficient of the gravitational anomaly. We briefly discuss the possible relevance of this "chiral Alfvén wave" in physical systems.
Gravitons possess a Berry curvature due to their helicity. We derive the semiclassical equations of motion for gravitons taking into account the Berry curvature. We show that this quantum correction leads to the splitting of the trajectories of right- and left-handed gravitational waves in curved space, and that this correction can be understood as a topological phenomenon. This is the spin Hall effect (SHE) of gravitational waves. We find that the SHE of gravitational waves is twice as large as
Circularly polarized photons have the Berry curvature in the semiclassical regime. Based on the kinetic equation for such chiral photons, we derive the (non)equilibrium expression of the photon current in the direction of the vorticity. We briefly discuss the relevance of this ``photonic chiral vortical effect'' in pulsars and rotating massive stars and its possible realization in semiconductors.
We study the properties of QCD at high baryon density in a finite volume where color superconductivity occurs. We derive exact sum rules for complex eigenvalues of the Dirac operator at a finite chemical potential, and show that the Dirac spectrum is directly related to the color superconducting gap Delta. Also, we find a characteristic signature of color superconductivity: an X-shaped spectrum of partition function zeros in the complex quark mass plane near the origin, reflecting the Z(2)LxZ(2)
We argue that the effective theory for electromagnetic fields in spatially varying meson condensations in dense nuclear and quark matter is given by the axion electrodynamics. We show that one of the helicity states of photons there has the nonrelativistic gapless dispersion relation $\ensuremath{\omega}\ensuremath{\sim}{k}^{2}$ at small momentum, while the other is gapped. This ``nonrelativistic photon'' may also be realized at the interface between topological and trivial insulators in condens
In the presence of the fluid helicity $\mathbit{v}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{\ensuremath{\omega}}$, the magnetic field induces an electric current of the form $\mathbit{j}={C}_{\mathrm{HME}}(\mathbit{v}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{\ensuremath{\omega}})\mathbit{B}$. This is the helical magnetic effect (HME). We show that for massless Dirac fermions with charge $e=1$, the transport coefficient ${C}_{\mathrm{HME}}$ is fixed by the chiral anomaly coeffic
The local and slow dynamics of a colloidal particle dispersed in a hyperswollen lyotropic lamellar phase was studied by passive and active microrheological methods. According to observation by a particle-tracking video microscopy, the motion of a particle follows a normal diffusion process in a lamellar phase with a large interlayer distance. However, trap-diffusion motion was also observed for a small interlayer distance. This characteristic motion was discussed by consideration of the time evo
Bidirectional promoters are the major source of gene activation-associated noncoding RNA (ncRNA). PC12 cells offer an interesting model for understanding the mechanism underlying bidirectional promoter-mediated cell cycle control. Nerve growth factor (NGF)-stimulated PC12 cells elongate neurites, and are in a reversible cell-cycle-arrested state. In contrast, these cells irreversibly differentiate and cannot re-enter the normal cell cycle after NGF plus cAMP treatment. In this study, using direc