We study the property of matter in equilibrium with a static, spherically symmetric black hole in D- dimensional spacetime. It requires that this kind of matter has an equation of state ω≡pr/ρ = -n/（n ＋ 2k）, k,...We study the property of matter in equilibrium with a static, spherically symmetric black hole in D- dimensional spacetime. It requires that this kind of matter has an equation of state ω≡pr/ρ = -n/（n ＋ 2k）, k, n ∈ N （where n 〉 1 corresponds to a mixture of vacuum matter and ＂hair＂ matter）, which seems to be independent of D. However, when we associate this result with specific models, we find that these hairy black holes can live only in some special dimensional spacetime： （i） D = 2 ＋ 2k/n while the black hole is surrounded by cosmic strings, which requires D is even or D ∈ N, depending on the value of n, this is consistent with some important results in superstring theory, it might reveal the relation between cosmic string and superstring in another aspect; （ii） the black hole can be surrounded by linear dilaton field only in 4-dimensional spacetime. In both cases, D = 4 is special. We also present some examples of such hairy black holes in higher dimensions, including a toy model with negative energy density.展开更多
The Management Regulations on Recallof Children's Toys is a recall system based onthe Management Regulations on Recall of MotorVehicles in China.During its two years,the children'stoy recall management system ...The Management Regulations on Recallof Children's Toys is a recall system based onthe Management Regulations on Recall of MotorVehicles in China.During its two years,the children'stoy recall management system has helped toprevent and eliminate damage caused by defectivechildren's toys.It has also helped to protect children'shealth and safety,safeguard public safetyand interest,and improve toy manufacturers' productquality and safety awareness.However,due tothe small scale of most Chinese toy manufacturers,and the low standard of management,more effort isneeded from government departments and thecommunity to improve the recall system.展开更多
基金Supported in part by the National Natural Science Foundation of China under Grant Nos. 90503009 and 10775116973 Program under Grant No. 2005CB724508
文摘We study the property of matter in equilibrium with a static, spherically symmetric black hole in D- dimensional spacetime. It requires that this kind of matter has an equation of state ω≡pr/ρ = -n/（n ＋ 2k）, k, n ∈ N （where n 〉 1 corresponds to a mixture of vacuum matter and ＂hair＂ matter）, which seems to be independent of D. However, when we associate this result with specific models, we find that these hairy black holes can live only in some special dimensional spacetime： （i） D = 2 ＋ 2k/n while the black hole is surrounded by cosmic strings, which requires D is even or D ∈ N, depending on the value of n, this is consistent with some important results in superstring theory, it might reveal the relation between cosmic string and superstring in another aspect; （ii） the black hole can be surrounded by linear dilaton field only in 4-dimensional spacetime. In both cases, D = 4 is special. We also present some examples of such hairy black holes in higher dimensions, including a toy model with negative energy density.
文摘The Management Regulations on Recallof Children's Toys is a recall system based onthe Management Regulations on Recall of MotorVehicles in China.During its two years,the children'stoy recall management system has helped toprevent and eliminate damage caused by defectivechildren's toys.It has also helped to protect children'shealth and safety,safeguard public safetyand interest,and improve toy manufacturers' productquality and safety awareness.However,due tothe small scale of most Chinese toy manufacturers,and the low standard of management,more effort isneeded from government departments and thecommunity to improve the recall system.
