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arXiv 1302.1044hep-ph
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电弱气泡速度的一种有效方法

An efficient approach to electroweak bubble velocities

Stephan J. Huber, Miguel Sopena

摘要:

扩展的标准模型被认为是可行的设置为一阶电弱相变满足萨哈罗夫的三个条件的产生重子不对称的宇宙。这些扩展提供了一个足够强的相变,并消除了标准模型中出现的主要障碍:希格斯质量的下限太高,新产生的重子不对称性立即消失,以及不充分的CP破坏。我们将宇宙流体动力学地描述为通过唯象摩擦项耦合到希格斯场的流体,并研究了在相变期间成核的气泡的时间演化。我们表示在流体动力学方程中的摩擦项的颗粒含量的模型,校准摩擦的基础上现有的计算的标准模型,并产生预测的速度膨胀的气泡壁在静止状态。通过这种方式,我们开发了一种非常有效的方法来计算气泡速度。作为一个例子,我们应用我们的形式主义的一阶相变的6维扩展的标准模型,在目前的范围内的希格斯质量,可以重现观察到的重子不对称的宇宙。取决于相变的强度,壁速度从约0.3变化到接近光速。我们的方法可以很容易地适用于计算壁面速度在其他有趣的扩展标准模型。

英文摘要:

Extensions of the Standard Model are being considered as viable settings for a first-order electroweak phase transition which satisfy Sakharov's three conditions for the generation of the baryon asymmetry of the Universe. These extensions provide a sufficiently strong phase transition and remove the main obstacles which appear in the context of the Standard Model: A far-too-high lower bound on the Higgs mass, immediate wipeout of the newly-created baryon asymmetry, and insufficient CP violation. We describe the Universe hydrodynamically as a fluid coupled to the Higgs field via a phenomenological friction term, and study the time evolution of bubbles nucleated during the phase transition. We express the friction term in the hydrodynamic equations in terms of the particle content of the model, calibrate the friction on the basis of existing calculations for the Standard Model, and produce predictions for the velocity of the expanding bubble wall in the stationary regime. This way we develop a very efficient approach to compute bubble velocities. As an example, we apply our formalism to the first-order phase transition of a dimension-6 extension of the Standard Model which, within the present bounds on the Higgs mass, can reproduce the observed baryon asymmetry of the Universe. Depending on the strength of the phase transition, the wall velocity varies from about 0.3 to approaching the speed of light. Our method can easily be adapted to compute wall velocities in other interesting extensions of the Standard Model.

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