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Unified Dark Matter in Scalar Field Cosmologies

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 نشر من قبل Sabino Matarrese
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English
 تأليف Daniele Bertacca




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Considering the general Lagrangian of k-essence models, we study and classify them through variables connected to the fluid equation of state parameter w_kappa. This allows to find solutions around which the scalar field describes a mixture of dark matter and cosmological constant-like dark energy, an example being the purely kinetic model proposed by Scherrer. Making the stronger assumption that the scalar field Lagrangian is exactly constant along solutions of the equation of motion, we find a general class of k-essence models whose classical trajectories directly describe a unified dark matter/dark energy (cosmological constant) fluid. While the simplest case of a scalar field with canonical kinetic term unavoidably leads to an effective sound speed c_s=1, thereby inhibiting the growth of matter inhomogeneities, more general non-canonical k-essence models allow for the possibility that c_s << 1 whenever matter dominates.



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