Results 1 - 10 of 23796
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[en] We discuss the factors which determine the strength of the excitonic coupling constant and show that, in general, it will be small. However, we show that by proper choice of the system and its energy levels, strong coupling should be possible. In this case superconductivity at higher temperatures should occur
[en] It is demonstrated, by using the proper renormalization procedure in the improved one-loop approximation, that the effective coupling constant approaches a constant nonzero value at very high temperature. Weldon's result, which shows that the coupling constant grows logarithmically with temperature, is unsatisfactory because of the presence of an arbitrary constant energy scale. (author)
[en] We investigate the finite and large N behaviors of independent-value O(N)-invariant matrix models. These are models defined with matrix-type fields and with no gradient term in their action. They are generically nonrenormalizable but can be handled by nonperturbative techniques. We find that the functional integral of any O(N) matrix trace invariant may be expressed in terms of an O(N)-invariant measure. Based on this result, we prove that, in the limit that all interaction coupling constants go to zero, any interacting theory is continuously connected to a pseudo-free theory. This theory differs radically from the familiar free theory consisting in putting the coupling constants to zero in the initial action. The proof is given for generic, finite-size matrix models, whereas, in the limiting case N → ∞, we succeed in showing this behavior for restricted types of actions using a particular scaling of the parameters
[en] Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb-1 of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the Standard Model-dark sector mixing angle and the dark sector coupling constant.
[en] Quantum coherence and non-Markovianity of an atom in a dissipative cavity under weak measurement are investigated in this work. We find that: the quantum coherence obviously depends on the initial atomic state, the strength of the weak measurement and its reversal, the atom–cavity coupling constant and the non-Markovian effect. It is obvious that the weak measurement effect protects the coherence better. The quantum coherence is preserved more efficiently for larger atom– cavity coupling. The stronger the non-Markovian effect is, the more slowly the coherence reduces. The quantum coherence can be effectively protected by means of controlling these physical parameters. (paper)