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Abstract: Certain oscillatory features in the primordial scalar power spectrum areknown to provide a better fit to the outliers in the cosmic microwavebackground data near the multipole moments of $\ell=22$ and 40. These featuresare usually generated by introducing a step in the popular, quadratic potentialdescribing the canonical scalar field. Such a model will be ruled out, if thetensors remain undetected at a level corresponding to a tensor-to-scalar ratioof, say, $r\simeq 0.1$. In this work, in addition to the popular quadraticpotential, we investigate the effects of the step in a small field model and atachyon model. With possible applications to future datasets such as PLANCKin mind, we evaluate the tensor power spectrum exactly, and include itscontribution in our analysis. We compare the models with the WMAP five as wellas seven-year, the QUaD and the ACBAR data. As expected, a step at aparticular location and of a suitable magnitude and width is found to improvethe fit to the outliers near $\ell=22$ and 40 in all these cases. We pointout that, if the tensors prove to be small say, $r\lesssim 0.01$, thequadratic potential and the tachyon model will cease to be viable, and moreattention will need to be paid to examples such as the small field models.



Author: Dhiraj Kumar Hazra, Moumita Aich, Rajeev Kumar Jain, L. Sriramkumar, Tarun Souradeep

Source: https://arxiv.org/







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