36,044 research outputs found
26Al/10Be Age of Peking Man
The chronological position of Peking Man, or Homo erectus pekinensis, has long been pursued, but has remained problematic due to lack of a suitable dating method^1-7^. Here we report cosmogenic ^26^Al/ ^10^Be burial dating of quartz sediments and artifacts from the lower strata of Zhoukoudian Locality 1 where the remains of early members of the Peking Man family were discovered. This study marks the first radioisotopic dating of any early hominin site in China beyond the range of mass spectrometric U-series dating. The weighted mean of six meaningful measurements, 0.75 +/-; 0.09 (0.11) Ma (million years), provides the best age estimate for lower cultural Layers ^7-10^. Together with previously reported U-series^3^ and paleomagnetic^4^ data, as well as sedimentological considerations^8, 9^ these layers may be further correlated to S6-S7 in Chinese loess stratigraphy or marine isotope stages 17-18, in the range of ~0.68-0.75 Ma. These ages are substantially older than previously supposed and may imply hominin presence in northern China throughout early Middle Pleistocene climate cycles
A Static Spherically Symmetric Solution of the Einstein-aether Theory
By using of the Euler-Lagrange equations, we find a static spherically
symmetric solution in the Einstein-aether theory with the coupling constants
restricted. The solution is similar to the Reissner-Nordstrom solution in that
it has an inner Cauchy horizon and an outer black hole event horizon. But a
remarkable difference from the Reissner-Nordstrom solution is that it is not
asymptotically flat but approaches a two dimensional sphere. The resulting
electric potential is regular in the whole spacetime except for the curvature
singularity. On the other hand, the magnetic potential is divergent on both
Cauchy horizon and the outer event horizon.Comment: 12 pages, 8 figures. To appear in PR
Cosmic evolution of scalar fields with multiple vacua: generalized DBI and quintessence
We find a method to rewrite the equations of motion of scalar fields,
generalized DBI field and quintessence, in the autonomous form
for\emph{arbitrary} scalar potentials. With the aid of this method, we explore
the cosmic evolution of generalized DBI field and quintessence with the
potential of multiple vacua. Then we find that the scalars are always frozen in
the false or true vacuum in the end. Compared to the evolution of quintessence,
the generalized DBI field has more times of oscillations around the vacuum of
the potential. The reason for this point is that, with the increasing of speed
, the friction term of generalized DBI field is greatly decreased.
Thus the generalized DBI field acquires more times of oscillations.Comment: 8 pages, 9 figures, accepted by IJTP. A number of typos correcte
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