21,043 research outputs found
From the Dyson-Schwinger to the transport equation in the background field gauge of QCD.
The non-equilibrium quantum field dynamics is usually described in the closed-time-path formalism. The initial state correlations are introduced into the generating functional by non-local source terms. We propose a functional approach to the Dyson-Schwinger equation, which treats the non-local and local source terms in the same way. In this approach, the generating functional is formulated for the connected Green functions and one-particle-irreducible vertices. The great advantages of our approach over the widely used two-particle-irreducible method are that it is much simpler and that it is easy to implement the procedure in a computer program to automatically generate the Feynman diagrams for a given process. The method is then applied to a pure gluon plasma to derive the gauge-covariant transport equation from the Dyson-Schwinger equation in the background covariant gauge. We discuss the structure of the kinetic equation and show its relationship with the classical one. We derive the gauge-covariant collision part and present an approximation in the vicinity of equilibrium. The role of the non-local source kernel in the non-equilibrium system is discussed in the context of a free scalar field. PACS numbers: 12.38.Mh, 25.75.-q, 24.85.+p, 11.15.K
Holographic entropy inequalities and gapped phases of matter
We extend our studies of holographic entropy inequalities to gapped phases of
matter. For any number of regions, we determine the linear entropy inequalities
satisfied by systems in which the entanglement entropy satisfies an exact area
law. In particular, we find that all holographic entropy inequalities are valid
in such systems. In gapped systems with topological order, the "cyclic
inequalities" derived recently for the holographic entanglement entropy
generalize the Kitaev-Preskill formula for the topological entanglement
entropy. Finally, we propose a candidate linear inequality for general 4-party
quantum states.Comment: 20 pages, 4 figures. v2: section 4 rewritten, where all linear
entropy (in)equalities satisfied by area-law systems are derived and an error
in their relations to graph theory is correcte
Kinetic equation for gluons in the background gauge of QCD
We derive the quantum kinetic equation for a pure gluon plasma, applying the background field and closed-time-path method. The derivation is more general and transparent than earlier works. A term in the equation is found which, as in the classical case, corresponds to the color charge precession for partons moving in the gauge field. PACS numbers: 12.38.Mh, 25.75.-q, 24.85.+p, 11.15.K
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Structure of the AAA protein Msp1 reveals mechanism of mislocalized membrane protein extraction.
The AAA protein Msp1 extracts mislocalized tail-anchored membrane proteins and targets them for degradation, thus maintaining proper cell organization. How Msp1 selects its substrates and firmly engages them during the energetically unfavorable extraction process remains a mystery. To address this question, we solved cryo-EM structures of Msp1-substrate complexes at near-atomic resolution. Akin to other AAA proteins, Msp1 forms hexameric spirals that translocate substrates through a central pore. A singular hydrophobic substrate recruitment site is exposed at the spiral's seam, which we propose positions the substrate for entry into the pore. There, a tight web of aromatic amino acids grips the substrate in a sequence-promiscuous, hydrophobic milieu. Elements at the intersubunit interfaces coordinate ATP hydrolysis with the subunits' positions in the spiral. We present a comprehensive model of Msp1's mechanism, which follows general architectural principles established for other AAA proteins yet specializes Msp1 for its unique role in membrane protein extraction
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