22,503 research outputs found
Two-loop Improved Truncation of the Ghost-Gluon Dyson-Schwinger Equations: Multiplicatively Renormalizable Propagators and Nonperturbative Running Coupling
The coupled Dyson-Schwinger equations for the gluon and ghost propagators are
investigated in the Landau gauge using a two-loop improved truncation that
preserves the multiplicative renormalizability of the propagators. In this
truncation all diagrams contribute to the leading order infrared analysis. The
infrared contributions of the nonperturbative two-loop diagrams to the gluon
vacuum polarization are computed analytically, and this reveals that infrared
power behaved propagator solutions only exist when the squint diagram
contribution is taken into account. For small momenta the gluon and ghost
dressing functions behave respectively like (p^2)^{2\kappa} and
(p^2)^{-\kappa}, and the running coupling exhibits a fixed point. The values of
the infrared exponent and fixed point depend on the precise details of the
truncation. The coupled ghost-gluon system is solved numerically for all
momenta, and the solutions have infrared behaviors consistent with the
predictions of the infrared analysis. For truncation parameters chosen such
that \kappa=0.5, the two-loop improved truncation is able to produce solutions
for the propagators and running coupling which are in very good agreement with
recent lattice simulations.Comment: 41 pages, LateX; minor corrections; accepted for publication in
Few-Body System
Strong Coordination with Polar Codes
In this paper, we design explicit codes for strong coordination in two-node
networks. Specifically, we consider a two-node network in which the action
imposed by nature is binary and uniform, and the action to coordinate is
obtained via a symmetric discrete memoryless channel. By observing that polar
codes are useful for channel resolvability over binary symmetric channels, we
prove that nested polar codes achieve a subset of the strong coordination
capacity region, and therefore provide a constructive and low complexity
solution for strong coordination.Comment: 7 pages doublespaced, presented at the 50th Annual Allerton
Conference on Communication, Control and Computing 201
Secret key generation from Gaussian sources using lattice hashing
We propose a simple yet complete lattice-based scheme for secret key
generation from Gaussian sources in the presence of an eavesdropper, and show
that it achieves strong secret key rates up to 1/2 nat from the optimal in the
case of "degraded" source models. The novel ingredient of our scheme is a
lattice-hashing technique, based on the notions of flatness factor and channel
intrinsic randomness. The proposed scheme does not require dithering.Comment: 5 pages, Conference (ISIT 2013
Comment on "Nucleon form factors and a nonpointlike diquark"
Authors of Phys. Rev. C 60, 062201 (1999) presented a calculation of the
electromagnetic form factors of the nucleon using a diquark ansatz in the
relativistic three-quark Faddeev equations. In this Comment it is pointed out
that the calculations of these form factors stem from a three-quark bound state
current that contains overcounted contributions. The corrected expression for
the three-quark bound state current is derived.Comment: 6 pages, 1 figure, revtex, eps
- …