In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U（1） gauge theories. This assumption is that the noneommutative effects start to be visible continuously...In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U（1） gauge theories. This assumption is that the noneommutative effects start to be visible continuously from a scale ANC and that below this scale the theory is a commutative one. Based on this assumption and using background field method and loop calculations, an effective action is derived for noncommutative U（1） gauge theory. It will be shown that the corresponding low energy effective theory is asymptotically free and that under this condition the noncommutative quadratic IR divergences will not appear. The effective theory contains higher dimensional terms, which become more important at high energies. These terms predict an elastic photon-photon scattering due to the noncommutativity of space. The coefficients of these higher dimensional terms also satisfy a positivity constraint indicating that in this theory the related diseases of superluminal signal propagating and bad analytic properties of S-matrix do not exist. In the last section, we will apply our method to the noncommutative extra dimension theories.展开更多
The synthetic jets generated by multiple-frequency actuating signals composed of a basic sinusoidal wave and a superposed high-frequency signal is investigated by two-dimensional simulation in the present study.The ef...The synthetic jets generated by multiple-frequency actuating signals composed of a basic sinusoidal wave and a superposed high-frequency signal is investigated by two-dimensional simulation in the present study.The effect of the frequency and amplitude of the high-frequency signal on the synthetic jet in the quiescent flow is investigated in detail with stroke length ratio L and Reynolds number Re_(U0)kept as constant.It is found that,with the high-frequency signal superposed,the vortex pairs induced by the synthetic jets are strengthened and accelerated.The distance that the vortex pairs can propagate downstream is also elongated.The entrainment of the synthetic jets is thus enhanced as well.The optimal design is reached when the frequency ratio,defined as the ratio between the superposed signal frequency and the basic signal frequency,is fixed at f^(+)=2.At this optimal frequency ratio,the jet entrainment increases monotonously with the amplitude of the high-frequency signal.展开更多
文摘In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U（1） gauge theories. This assumption is that the noneommutative effects start to be visible continuously from a scale ANC and that below this scale the theory is a commutative one. Based on this assumption and using background field method and loop calculations, an effective action is derived for noncommutative U（1） gauge theory. It will be shown that the corresponding low energy effective theory is asymptotically free and that under this condition the noncommutative quadratic IR divergences will not appear. The effective theory contains higher dimensional terms, which become more important at high energies. These terms predict an elastic photon-photon scattering due to the noncommutativity of space. The coefficients of these higher dimensional terms also satisfy a positivity constraint indicating that in this theory the related diseases of superluminal signal propagating and bad analytic properties of S-matrix do not exist. In the last section, we will apply our method to the noncommutative extra dimension theories.
基金the National Natural Science Foundation of China(Grant No.11721202).
文摘The synthetic jets generated by multiple-frequency actuating signals composed of a basic sinusoidal wave and a superposed high-frequency signal is investigated by two-dimensional simulation in the present study.The effect of the frequency and amplitude of the high-frequency signal on the synthetic jet in the quiescent flow is investigated in detail with stroke length ratio L and Reynolds number Re_(U0)kept as constant.It is found that,with the high-frequency signal superposed,the vortex pairs induced by the synthetic jets are strengthened and accelerated.The distance that the vortex pairs can propagate downstream is also elongated.The entrainment of the synthetic jets is thus enhanced as well.The optimal design is reached when the frequency ratio,defined as the ratio between the superposed signal frequency and the basic signal frequency,is fixed at f^(+)=2.At this optimal frequency ratio,the jet entrainment increases monotonously with the amplitude of the high-frequency signal.
