1,953 research outputs found
Renormalization flow of QED
We investigate textbook QED in the framework of the exact renormalization
group. In the strong-coupling region, we study the influence of
fluctuation-induced photonic and fermionic self-interactions on the
nonperturbative running of the gauge coupling. Our findings confirm the
triviality hypothesis of complete charge screening if the ultraviolet cutoff is
sent to infinity. Though the Landau pole does not belong to the physical
coupling domain owing to spontaneous chiral symmetry breaking (chiSB), the
theory predicts a scale of maximal UV extension of the same order as the Landau
pole scale. In addition, we verify that the chiSB phase of the theory which is
characterized by a light fermion and a Goldstone boson also has a trivial
Yukawa coupling.Comment: 4 pages, 1 figur
Critical interfaces in the random-bond Potts model
We study geometrical properties of interfaces in the random-temperature
q-states Potts model as an example of a conformal field theory weakly perturbed
by quenched disorder. Using conformal perturbation theory in q-2 we compute the
fractal dimension of Fortuin Kasteleyn domain walls. We also compute it
numerically both via the Wolff cluster algorithm for q=3 and via
transfer-matrix evaluations. We obtain numerical results for the fractal
dimension of spin cluster interfaces for q=3. These are found numerically
consistent with the duality kappa(spin) * kappa(FK)= 16 as expressed in
putative SLE parameters.Comment: 4 page
Lossless State Detection of Single Neutral Atoms
We introduce lossless state detection of trapped neutral atoms based on
cavity-enhanced fluorescence. In an experiment with a single 87-Rb atom, a
hyperfine-state-detection fidelity of 99.4% is achieved in 85 microseconds. The
quantum bit is interrogated many hundreds of times without loss of the atom
while a result is obtained in every readout attempt. The fidelity proves robust
against atomic frequency shifts induced by the trapping potential. Our scheme
does not require strong coupling between the atom and cavity and can be
generalized to other systems with an optically accessible quantum bit.Comment: 4 pages, 4 figure
Cosmic Structure Traced by Precision Measurements of the X-Ray Brightest Galaxy Clusters in the Sky
The current status of our efforts to trace cosmic structure with 10^6
galaxies (2MASS), 10^3 galaxy clusters (NORAS II cluster survey), and precision
measurements for 10^2 galaxy clusters (HIFLUGCS) is given. The latter is
illustrated in more detail with results on the gas temperature and metal
abundance structure for 10^0 cluster (A1644) obtained with XMM-Newton.Comment: 4 pages; to be published in the Proceedings of the Conference: The
Emergence of Cosmic Structure, College Park, MD (2002), editors: S.S. Holt
and C. Reynolds; also available at http://www.reiprich.ne
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