28,044 research outputs found
Universal Boundary Entropies in Conformal Field Theory: A Quantum Monte Carlo Study
Recently, entropy corrections on nonorientable manifolds such as the Klein
bottle are proposed as a universal characterization of critical systems with an
emergent conformal field theory (CFT). We show that entropy correction on the
Klein bottle can be interpreted as a boundary effect via transforming the Klein
bottle into an orientable manifold with nonlocal boundary interactions. The
interpretation reveals the conceptual connection of the Klein bottle entropy
with the celebrated Affleck-Ludwig entropy in boundary CFT. We propose a
generic scheme to extract these universal boundary entropies from quantum Monte
Carlo calculation of partition function ratios in lattice models. Our numerical
results on the Affleck-Ludwig entropy and Klein bottle entropy for the
-state quantum Potts chains with show excellent agreement with the
CFT predictions. For the quantum Potts chain with , the Klein bottle
entropy slightly deviates from the CFT prediction, which is possibly due to
marginally irrelevant terms in the low-energy effective theory.Comment: 10 pages, 4 figures. Published versio
Hyper-accreting black hole as GRB central engine. I: Baryon loading in GRB jets
A hyper-accreting stellar-mass black hole has been long speculated as the
best candidate of central engine of gamma-ray bursts (GRBs). Recent rich
observations of GRBs by space missions such as Swift and Fermi pose new
constraints on GRB central engine models. In this paper, we study the baryon
loading processes of a GRB jet launched from a black hole central engine. We
consider a relativistic jet powered by -annihilation or by the
Blandford-Znajek (BZ) mechanism. We consider baryon loading from a
neutrino-driven wind from a neutrino-cooling-dominated accretion flow. For a
magnetically dominated BZ jet, we consider neutron-drifting from the magnetic
wall surrounding the jet and subsequent positron capture and proton-neutron
inelastic collisions. The minumim baryon loads in both types of jet are
calculated. We find that in both cases, a more luminous jet tends to be more
baryon poor. A neutrino-driven "fireball" is typically "dirtier" than a
magnetically dominated jet, while a magnetically dominated jet can be much
cleaner. Both models have the right scaling to interpret the empirical
relation discovered recently. Since some neutrino-driven
jets have too much baryon loading as compared with the data, we suggest that at
least a good fraction of GRBs should have a magnetically dominated central
engine.Comment: 9 pages, 2 figures; Accepted for publication in Ap
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