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Abstract: In unparticle dark matter unmatter models the equation of state of theunmatter is given by $p= ho-2d U+1$, where $d U$ is the scaling factor.Unmatter with such equations of state would have a significant impact on theexpansion history of the universe. Using type Ia supernovae SNIa, the baryonacoustic oscillation BAO measurements and the shift parameter of the cosmicmicrowave background CMB to place constraints on such unmatter models we findthat if only the SNIa data is used the constraints are weak. However, with theBAO and CMB shift parameter data added strong constraints can be obtained. Forthe $\Lambda$UDM model, in which unmatter is the sole dark matter, we find that$d U > 60$ at 95% C.L. For comparison, in most unparticle physics models it isassumed $d U<2$. For the $\Lambda$CUDM model, in which unmatter co-exists withcold dark matter, we found that the unmatter can at most make up a few percentof the total cosmic density if $d U<10$, thus it can not be the major componentof dark matter.

Autor: Yan Gong, Xuelei Chen


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