168,080 research outputs found
Generalized pulsating strings
In this paper we consider new solutions for pulsating strings. For this
purpose we use tha idea of the generalized ansatz for folded and circular
strings in hep-th/0311004. We find the solutions to the resulting
Neumann-Rosochatius integrable system and the corrections to the energy. To do
that we use the approach developed by Minahan in hep-th/0209047 and find that
the corrections are quite different from those obtained in that paper and
hep-th/0310188. We conclude with comments on our solutions and obtained
corrections to the energy, expanded to the leading order in lambda.Comment: v.2 references added, citations corrected, 18 page
Weakly-induced strong CP-violation
Weak interaction contributions to the strong theta parameter are revisited in
the frame of a large-Nc Chiral Perturbation Theory. Focusing on the hadronic
(eta,etaprime) \to pi pi amplitudes, we express these second-order corrections
in terms of the CP-violating parameter in K \to pi pi decays to obtain
Delta_w(theta) approx 10^{-17} at O(GF^2 epsilonprime).Comment: 11 pages, 1 figure. One reference and comments on electroweak
corrections added. Version published in Physics Letters
Infrared limit in external field scattering
Scattering of electrons/positrons by external classical electromagnetic wave
packet is considered in infrared limit. In this limit the scattering operator
exists and produces physical effects, although the scattering cross-section is
trivial.Comment: 12 pages; published version; minor corrections; comments adde
On higher-order corrections in a four-fermion Lifshitz model
We study a flavour-violating four-fermion interaction in the Lifshitz
context, in 3+1 dimensions and with a critical exponent z=3. This model is
renormalizable, and features dynamical mass generation, as well as asymptotic
freedom. At one-loop, it is only logarithmically divergent, but the superficial
degree of divergence of the two-point functions is 3. We calculate the two-loop
corrections to the propagators, and show that, at this order, the
Lorentz-violating corrections to the IR dispersion relation are quadratic in
the cut off. Furthermore, these corrections are too important to represent a
physical effect. As a consequence, the predictive power of the model in terms
of Lorentz-violating effects in the propagation of particles is limited.Comment: 20 pages, 3 figures, comments adde
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