Asymptotic structure of Einstein-Gauss-Bonnet theory in lower dimensions

Recently,an action principle for the D→4 limit of Einstein-Gauss-Bonnet gravity has been proposed.It is a special scalar-tensor theory that belongs to the family of Horndeski gravity.It also has well defined D→3 and D→2 limits.In this work,we examine this theory in three and four dimensions in the Bondi-Sachs framework.In both three and four dimensions,we find that there is no news function associated with the scalar field,which means that there is no scalar propagating degree of freedom in the theory.In four dimensions,the mass-loss formula is not affected by the Gauss-Bonnet term.This is consistent with the fact that there is no scalar radiation.However,the effects of the Gauss-Bonnet term are quite significant in the sense that they arise just one order after the integration constants and also arise in the quadrupole of the gravitational source.     

The band structures of some transition metals and their NaCl-type compounds

The band structures of Group IVB (Ti,Zr,Hf),VB (V,Nb,Ta) and VIB (Cr,Mo,W) transition metals and some of their carbides and nitrides (TiN,ZrN,HfN,VC,NbC,TaC,VN,NbN,TaN) with NaCl-type (Bl-type) structure have been calculated by using the tight-binding method within the Extended Hiickel approximation (EHT).The energy bands,densities of states and crystal orbital overlap populations are given.The relationship between the bonding properties and the superconducting transition temperatures (Tc) of them is discussed.The influences of various kinds of metallic atoms and changes of bond lengths on Tc are also discussed.     

Localized molecular orbital studies on B_4C1_4,1,5-C_2B_3H_5 and B_nH_n~(2-)(n = 6-10, 12)

The wave functions, level energies and Mulliken population analysis of localized molecular orbitals (LMO's) for B4Cl4, 1,5-C2B3H5 and the closo-BnHn2- (n = 6-10, 12) are calculated by using the Edmiston-Reudenberg energy localization scheme under the CNDO/2 approximation in order to reveal the nature of quasi-aromaticity of the closo-BnHn2- (n > 5). It has been found that all the B-H or B-Cl LMO's are highly localized between the B and H (or Cl) atoms, corresponding to B-H or B-Cl o-bond, while the Bn framework bonding is formed mainly by the three-centered two-electron B-B-B bonds on the polyhedral faces. In the cases of B4Cl4 and 1,5-C2B3H5, these three-centered B-B-B bonds just fill their polyhedral faces; however, for the framework bonding of the closo-BnHn2- (n > 5), the valence electron deficiency leads to the delocalization of their three-centered B-B-B bonds, and as delocalizability of this three-centered B-B-B bond increases, some three-centered B-B-B bonds are further delocalized to become a f     

Ab initio band structure calculations on polymers (C5H3X)n (X=CH,N,P,As)

The ab initio crystal orbital calculations on conjugated aromatic six-membered rings polymers,namely,poly(p-phenylene) (PPP),poly(2,5-pyridinediyl) (PPD),poly(2,5-phosphabenzene) (PPB) and ploy(2,5-arsabenzene) (PAB) are reported.The comparison of the important electronic properties of these polymers,such as band gap,bandwidth,ionization potential and electron affinity,indicates that PPP is the best intrinsic semiconductor,and PPD has the best prospects for forming n-doped conducting materials.     

T(2,2,2,2)型tubular代数的合成代数

设A为有限域上的T(2,2,2,2)型tubular代数,它是tame遗传代数A0的单点扩张,也是tame遗传代数A∞的单点余扩张．记P0为预投射A0-模集合,L∞是预内射A∞-模集合,则P0,L∞(?)mod A记T=mod A＼(P0∪L∞)．本文证明A的合成代数C(A)具有形为P0·J·L∞的三角分解．