3,190 research outputs found
Thermodynamics in the universe described by the emergence of the space and the energy balance relation
It has previously been shown that it is more general to describe the
evolution of the universe based on the emergence of the space and the energy
balance relation. Here we investigate the thermodynamic properties of the
universe described by such a model. We show that the first law of
thermodynamics and the generalized second law of thermodynamics (GSLT) are both
satisfied and the weak energy condition are also fulfilled for two typical
examples. Finally we examine the physical consistency for the present model.Comment: 9 pages, 2 figure
Quasilocal Center-of-Mass for Teleparallel Gravity
Asymptotically flat gravitating systems have 10 conserved quantities, which
lack proper local densities. It has been hoped that the teleparallel equivalent
of Einstein's GR (TEGR, aka GR) could solve this gravitational
energy-momentum localization problem. Meanwhile a new idea: quasilocal
quantities, has come into favor. The earlier quasilocal investigations focused
on energy-momentum. Recently we considered quasilocal angular momentum for the
teleparallel theory and found that the popular expression (unlike our
``covariant-symplectic'' one) gives the correct result only in a certain frame.
We now report that the center-of-mass moment, which has largely been neglected,
gives an even stronger requirement. We found (independent of the frame gauge)
that our ``covariant symplectic'' Hamiltonian-boundary-term quasilocal
expression succeeds for all the quasilocal quantities, while the usual
expression cannot give the desired center-of-mass moment. We also conclude,
contrary to hopes, that the teleparallel formulation appears to have no
advantage over GR with regard to localization.Comment: 12 pages, to appear in the proceedings of the 10th Marcel Grossman
meeting (Rio de Janeiro, 2003
Production of proton-rich nuclei around Z=84-90 in fusion-evaporation reactions
Within the framework of the dinuclear system model, production cross sections
of proton-rich nuclei with charged numbers of Z=84-90 are investigated
systematically. Possible combinations with the Si, S, Ar
bombarding the target nuclides Ho, Tm, Yb,
Lu, Hf and Ta are analyzed thoroughly. The
optimal excitation energies and evaporation channels are proposed to produce
the proton-rich nuclei. The systems are feasible to be constructed in
experiments. It is found that the neutron shell closure of N=126 is of
importance during the evaporation of neutrons. The experimental excitation
functions in the Ar induced reactions can be nicely reproduced. The
charged particle evaporation is comparable with neutrons in cooling the excited
proton-rich nuclei, in particular for the channels with and proton
evaporation. The production cross section increases with the mass asymmetry of
colliding systems because of the decrease of the inner fusion barrier. The
channels with pure neutron evaporation depend on the isotopic targets. But it
is different for the channels with charged particles and more sensitive to the
odd-even effect.Comment: 15 pages, 10 figures. arXiv admin note: text overlap with
arXiv:0803.1117, arXiv:0707.258
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