标题： 弦论第五元素模型中慢滚参数的渐近界 显示英文标题

标题： Asymptotic bound on slow-roll parameter in stringy quintessence model

摘要： 我们研究了弦论五重子模型中体积模和稀释子标量部分在晚期时间的行为，重点关注它们对直接测量时空几何偏离德西特空间的哈勃慢滚参数$\epsilon$的贡献。 当只允许一个模场移动时，$\epsilon$在晚期时间收敛到稳定的固定点。 该固定点值大于$1$，因此无法实现慢滚。 此外，如果五重子势的衰减率大于某个临界值，势的正性要求稳定固定点值仅由$3$给出，与模场动力学的细节无关。 否则，固定点值与势的慢滚参数一致。 当体积模和稀释子同时沿势能下降时，我们可以找到两个模场对$\epsilon$的贡献在固定点满足的关系。 在这种情况下，固定点值通常不是单场情况下的固定点值的简单和，并且不能大于$3$。 显示英文摘要

摘要： We study the late time behavior of the scalar part of the volume modulus and the dilaton in stringy quintessence model, focusing on their contributions to the Hubble slow-roll parameter $\epsilon$ which directly measures the deviation of the spacetime geometry from de Sitter space. When only one of the moduli is allowed to move, $\epsilon$ converges to the stable fixed point at late time. The fixed point value is larger than $1$, thus the slow-roll cannot be realized. Moreover, if the decay rate of the quintessence potential is larger than some critical value, the positivity of the potential imposes that the stable fixed point value is just given by $3$, independent of the details of the moduli dynamics. Otherwise, the fixed point value coincides with the potential slow-roll parameter. When both the volume modulus and the dilaton roll down the potential simultaneously, we can find the relation between the contributions of two moduli to $\epsilon$ satisfied at the fixed point. In this case, the fixed point value is not in general the simple sum of fixed point values in the single field case and cannot be larger than $3$.