Potential-driven Galileon inflation
Potential-driven Galileon inflation
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DOI：
10.1088/1475-7516/2012/10/035
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发表时间：
2012-07
期刊：
影响因子：
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通讯作者：
Junko Ohashi;S. Tsujikawa
中科院分区：
文献类型：
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作者：
Junko Ohashi;S. Tsujikawa
对于由暴胀场的势能驱动的暴涨模型，协变伽利略拉格朗日$(Partial\Phi)^2盒Phi$一般起到减慢场演化的作用。另一方面，如果伽利略自相互作用相对于标准动量项占主导地位，我们证明了暴涨结束后不存在暴胀的振荡机制。这通常伴随着标量模的负传播速度平方c_S^2的出现，这导致了小尺度扰动的不稳定性。对于混沌暴涨和自然暴涨，我们阐明了暴胀在再热过程中相干振荡的参数空间。利用标量谱折射率和张量标量比的WMAP约束，我们发现势场$V(\Phi)=\lambda\Phi^4/4$的自耦合λ$被约束得非常小于1，并且自然暴涨的对称破缺标度$f$不能小于约化的普朗克质量$M\rmpl}$。我们还表明，在其他协变伽利略拉格朗日函数存在的情况下，即使对于0.1阶的自耦合因子，也存在膨胀子相干振荡的情况，但仍然普遍存在与负因子c_S^2因子相关的不稳定性。
For the models of inflation driven by the potential energy of an inflaton field $\phi$, the covariant Galileon Lagrangian $(\partial\phi)^2\Box \phi$ generally works to slow down the evolution of the field. On the other hand, if the Galileon self-interaction is dominant relative to the standard kinetic term, we show that there is no oscillatory regime of inflaton after the end of inflation. This is typically accompanied by the appearance of the negative propagation speed squared $c_s^2$ of a scalar mode, which leads to the instability of small-scale perturbations. For chaotic inflation and natural inflation we clarify the parameter space in which inflaton oscillates coherently during reheating. Using the WMAP constraints of the scalar spectral index and the tensor-to-scalar ratio as well, we find that the self coupling $\lambda$ of the potential $V(\phi)=\lambda \phi^4/4$ is constrained to be very much smaller than 1 and that the symmetry breaking scale $f$ of natural inflation cannot be less than the reduced Planck mass $M_{\rm pl}$. We also show that, in the presence of other covariant Galileon Lagrangians, there are some cases in which inflaton oscillates coherently even for the self coupling $\lambda$ of the order of 0.1, but still the instability associated with negative $c_s^2$ is generally present.