The effects of the N atom collective Lamb shift on single photon superradiance

The problem of single photon collective spontaneous emission, a.k.a. superradiance, from N atoms prepared by a single photon pulse of wave vector k₀ has been the subject of recent interest. It has been shown that a single photon absorbed uniformly by the N atoms will be followed by spontaneous emission in the same direction [M. Scully, E. Fry, C.H.R. Ooi, K. Wodkiewicz, Phys. Rev. Lett. 96 (2006) 010501; M. Scully, Laser Phys. 17 (2007) 635]; and in extensions of this work we have found a new kind of cavity QED in which the atomic cloud acts as a cavity containing the photon [A.A. Svidzinsky, J.T. Chang, M.O. Scully, Phys. Rev. Lett. 100 (2008) 160504]. In most of our studies, we have neglected virtual photon (“Lamb shift”) contributions. However, in a recent interesting paper, Friedberg and Mannassah [R. Friedberg, J.T. Manassah, Phys. Lett. A 372 (2008) 2514] study the effect of virtual photons investigating ways in which such effects can modify the time dependence and angular distributions of collective single photon emission. In the present Letter, we show that such virtual transitions play no essential role in our problem. The conclusions of [M. Scully, E. Fry, C.H.R. Ooi, K. Wodkiewicz, Phys. Rev. Lett. 96 (2006) 010501; M. Scully, Laser Phys. 17 (2007) 635; A.A. Svidzinsky, J.T. Chang, M.O. Scully, Phys. Rev. Lett. 100 (2008) 160504] stand as published. However, the N atom Lamb shift is an interesting problem in its own right and we here extend previous work both analytically and numerically.     

Top Quark Flavor Changing Decay t

[1]R. Casalbuoani, A. Deandrea, and M. Oertel, JHEP 032(2004) 0402. [2]G. Hooft, In Search of the Ultimate Building Blocks, Cambridge University Press, Cambridge (1997). [3]J. Belazey, Searches for New Physics at Hadron Coliders,Northern Illinois University (2005). [4]N. Arkani-hamed, A.G. Cohen, and H. Georgi, Phys. Lett.B 513 (2001) 232 [hep-ph/0105239]. [5]I. Low, W. Skiba, and D. Smith, Phys. Rev. D 66 (2002)072001 [hep-ph/0207243]. [6]N. Arkani-hamed, A.G. Cohen, E. Katz, and A.E. Nelson,JHEP 0207 (2002) 304 [hep-ph/0206021]. [7]N. Arkani-hamed, A.G. Cohen, E. Katz, A.E. Nelson, T.Gregoire, and J. G. Wacker, JHEP 0208 (2002) 021 [hepph/0206020]. [8]T. Gregoire and J.G. Wacker, JHEP 0208 (2002) 019[hep-ph/0206023]. [9]For a recent review, see e.g., M. Schmaltz, Nucl. Phys. B (Proc. Suppl.) 117 (2003) 40. [10]N. Arkani-hamed, A.G. Cohen, T. Gregoire, and J.G.Jacker, JHEP 0208 (2002) 020 [hep-ph/0202089]. [11]or a recent review, see e.g., M. Schmaltz, Nucl. Phys.Proc. Suppl. 117 (2003) 40 [hep-ph/0210415]. [12]E. Katz, J. Lee, A.E. Nelson, and D.G. Walker, hepph/0312287. [13]M. Beneke, I. Efthymiopoulos, M.L. Mangano, et al., hepph/0003033. [14]D.O. Carlson and C.-P. Yuan, hep-ph/9211289. [15]R. Frey, D. Gerdes, and J. Jaros, hep-ph/9704243. [16]G. Eilam, J.L. Hewett, and A. Soni, Phys. Rev. D 44(1991) 1473; W.S. Hou, Phys. Lett. B 296 (1992) 179; K.Agashe and M. Graesser, Phys. Rev. D 54 (1996) 4445;M. Hosch, K. Whisnant, and B.L. Young, Phys. Rev. D56 (1997) 5725. [17]C.S. Li, R.J. Oakes, and J.M. Yang, Phys. Rev. D 49(1994) 293, Erratum-ibid. D 56 (1997) 3156; G. Couture,C. Hamzaoui, and H. Koenig, Phys. Rev. D 52 (1995)1713; G. Couture, M. Frank, and H. Koenig, Phys. Rev.D 56 (1997) 4213; G.M. de Divitiis, et al., Nucl. Phys. B 504 (1997) 45. [18]B. Mele, S. Petrarca, and A. Soddu, Phys. Lett. B 435(1998) 401. [19]B. Mele, hep-ph/0003064. [20]J.M. Yang and C.S. Li, Phys. Rev. D 49 (1994) 3412,Erratum, ibid. D 51 (1995) 3974; J.G. Inglada, hepph/9906517. [21]L.R. Xing, W.G. Ma, R.Y. Zhang, Y.B. Sun, and H.S.Hou, Commun. Theor. Phys. (Beijing, China) 41 (2004)241. [22]L.R. Xing, W.G. Ma, R.Y. Zhang, Y.B. Sun, and H.S.Hou, Commun. Theor. Phys. (Beijing, China) 40 (2003)171. [23]T. Han, H.E. Logan, B. McElrath, and L.T. Wang, Phys.Rev. D 67 (2003) 095004. [24]I. Low, W. Skiba, and D. Smith, Phys. Rev. D 66 (2002)072001. [25]T. Han, H.E. Logan, B. McElrath, and L.T. Wang, hepph/0302188. [26]A.J. Buras, A. Poschenrieder, and S. Uhlig, hepph/0410309. [27]S. Eidelman, et al., Phys. Lett. B 592 (2004) 1. [28]F. Legerlehner, DESY 01-029, hep-ph/0105283.     

Shape Coexistence for 179Hg in Relativistic Mean-Field Theory

[1]J.H. Hamilton,A. VRamayya, W.T. Pinkston, et al.,Phys. Rev. Lett. 32 (1974) 239. [2]R. Julin, K. Helariutta, and M. Muikku, J. Phys. G 27(2001) R109. [3]J.H. Hamilton, Nukleonika 24 (1979) 561. [4]W.C. Ma, et al., Phys. Lett. B 139 (1984) 276. [5]R. Bengtsson, et al., Phys. Lett. B 183 (1987) 1. [6]S. Yoshida and N. Takigawa, Phys. Rev. C 55 (1996)1255. [7]T. Niksic, D. Vretenar, P. Ring, et al., Phys. Rev. C 65(2002) 054320. [8]F.G. Condev, M.P. Carpenter, R.V.F. Janssens, et al.,Phys. Lett. B 528 (2002) 221. [9]D.G. Jenkins, A.N. Andreyev, R.D. Page, et al., Phys.Rev. C 66 (2002) 011301(R). [10]B.D. Serot and J.D. Walecka, Adv. Nuc]. Phys. 16 (1986)1. [11]P. Ring, Prog. Part. Nucl. Phys. 37 (1996) 193. [12]J. Meng and P. Ring, Phys. Rev. Lett. 77 (1996) 3963. [13]J. Meng and P. Ring, Phys. Rev. Lett. 80 (1998) 460. [14]S.K. Patra, S. Yoshida, N. Takigawa, and C.R. Praharaj,Phys. Rev. C 50 (1994) 1924. [15]S. Yoshida, S.K. Patra, N. Takigawa, and C.R. Praharaj,Phys. Rev. C 50 (1994) 1938. [16]G.A. Lalazissis and P. Ring, Phys. Lett. B 427 (1998)225. [17]Jun-Qing Li, Zhong-Yu Ma, Bao-Qiu Chen, and Yong Zhou, Phys. Rev. C 65 (2002) 064305. [18]G. Audi and A.H. Wapstra, Nucl. Phys. A 565 (1993) 1. [19]G. Audi and A.H. Wapstra, Nucl. Phys. A 595 (1995)409. [20]G. Audi and A.H. Wapstra, Nucl. Phys. A 624 (1997) 1. [21]P. MOller and J.R. Nix, Atom. Data and Nucl. Data Table 59 (1995) 307.     

Study of Strange Quark Mass in CFL Phase

[1]M.Alford,K.Rajagopal,and F.Wilczek,Phys.Lett.B 422 (1998) 247; Nucl.Phys.B 537 (1999) 443. [2]M.Gyulassy and L.McLerran,arXiv:nucl-th/0405013;E.V.Shuryak,arXiv:hep-ph/0405066. [3]K.Rajagopal and F.Wilczek,hep-ph/0011333. [4]M.Alford,Chris Kouvaris,and K.Rajagopal,hepph/0406137. [5]Y.Nambu and G.Jona-Lasinio,Phys.Rev.122 (1961)345. [6]R.T.Cahill and C.D.Roberts,Phys.Rev.D 32 (1985)2419. [7]R.T.Cahill and Susan M.Ganner,hep-ph/9812491. [8]A.W.Steiner,S.Reddy,and M.Prakash,Phys.Rev.D 66 (2002) 094007. [9]P.Amore,M.C.Birse,J.A.McGovern,and N.R.Walet,Phys.Rev.D 65 (2002) 074005. [10]M.Alford and K.Rajagopal,JHEP 0206 (2002) 031. [11]Xiao-Fu Li,Yu-Xin Liu,Hong-Shi Zong,and En-GuangZhao,Phys.Rev.C 58 (1998) 1195. [12]H.Reinhardt,Phys.Lett.B 244 (1990) 2. [13]Steven Weinberg,The Quantum Theory of Fields,Vol.2,Cambridge University Press,Cambridge (1996) p.348.     

Sigma Terms and Strangeness Contents of Baryon Octet in Modified Chiral Perturbation Theory

[1]J.Gasser,H.Leutwyler,and M.E.Sainio,Phys.Lett.B 253 (1991) 252. [2]John Ellis,Eur.Phys.J.A 24S2 (2005) 3,[arXive:hepph/0411369]. [3]T.Inoue,V.E.Lyubovitskij,Th.Gutsche,and Amand Faessler,Phys.Rev.C 69 (2004) 035207,[arXive:hepph/0311275]. [4]M.M.Pavan,I.I.Strakovsky,R.L.Workman,and R.A.Arndt,PiN Newslett.16 (2002) 110,[arXive:hepph/0111066]. [5]V.E.Lyubovitskij,Th.Gutsche,Amand Faessler,and E.G.Drukarev,Phys.Rev.D 63 (2001) 054026,[arXive:hep-ph/0009341]. [6]S.D.Bass,Phys.Lett.B 329 (1994) 358,[arXive:hepph/9404294]. [7]Marc Knecht,PiN Newslett.15 (1999) 108,[arXive:hepph/9912443]. [8]P.Schweitzer,Phys.Rev.D 69 (2004) 034003. [9]B.C.Lehnhart,J.Gegelia,and S.Scherer,J.Phys.G 31(2005) 89,[arXive:hep-ph/0412092]. [10]P.J.Ellis and K.Torikoshi,Phys.Rev.C 61 (1999)015205. [11]Gerald E.Hite,William B.Kaufmann,and Richard J.Jacob,Phys.Rev.C 71 (2005) 065201. [12]S.Weinberg,Physica A 96 (1979) 327. [13]J.Gasser and H.Leutwyler,Nucl.Phys.B 250 (1985)465. [14]J.Gasser,M.E.Sainio,and A.Svarc,Nucl.Phys.B 307(1988) 779. [15]P.Papazoglou,D.Zschiesche,S.Schramm,J.SchaffnerBielich,H.St(o)cker,and W.Greiner,Phys.Rev.C 59(1999) 411. [16]T.Fuchs and J.Gegelia,Phys.Rev.D 68 (2003) 056005.     

Re-study of Nucleon Pole Contribution in J/

[1]V.D.Burkert,Phys.Lett.B 72 (1997) 109. [2]S.Capstick and W.Roberts,Prog.Part.Nucl.Phys.45 (2000) S241,and references therein. [3]B.S.Zou,Nucl.Phys.A 675 (2000) 167c; B.S.Zou,Nucl.Phys.A 684 (2001) 330; BES Collaboration (J.Z.Bai,et al.) Phys.Lett.B 510 (2001) 75; BES Collaboration (M.Ablikim,et al.),hep-ex/0405030. [4]R.Sinha and Susumu Okubo,Phys.Rev.D 30 (1984)2333. [5]W.H.Liang,P.N.Shen,B.S.Zou,and A.Faessler,Euro.Phys.J A 21 (2004) 487. [6]Particle Data Group,Euro.Phys.J.C 15 (2000) 1. [7]K.Tsushima,A.Sibrtsev,and A.W.Thomas,Phys.Lett.B 390 (1997) 29. [8]J.Kogut,Rev.Mod.Phys.51 (1979) 659; Rev.Mod.Phys.55 (1983) 775. [9]Q.Haider and L.C.Liu,J.Phys.G 22 (1996) 1187; L.C.Liu and W.X.Ma,J.Phys.G 26 (2000) L59. [10]V.G.J.Stoks,R.A.M.Klomp,C.P.F.Terheggen,and J.J.de Swart,Phys.Rev.C 49 (1994) 2950. [11]H.Haberzettl,C.Bennhold,T.Mart,and T.Feuster,Phys.Rev.C 58 (1998) R40. [12]Y.Oh,A.I.Titov,and T.-S.H.Lee,Phys.Rev.C 63(2001) 25201.     

Quantum Correlations in a Family of Two-Qubit Separable States

Quantum correlations in a family of two-qubit separable classical-quantum correlated states are intensively studied with four different approaches, namely, quantum discord [Phys. Rev. Lett. 88 (2002) 017901], measurement- induced disturbance (MID) [Phys. Rev. A 77 (2008) 022301], ameliorated MID [J. Phys. A: Math. Theor. 44 (2011) 352002] and quantum dissonance [Phys. Rev. Lett. 104 (2010) 080501]. Quantum correlations captured with different approaches are compared and discussed so that their three distinct features are exposed.     

Quantum Correlations in a Family of Two-Qubit Separable States

Quantum correlations in a family of two-qubit separable classical-quantum correlated states are intensively studied with four diferent approaches,namely,quantum discord[Phys.Rev.Lett.88(2002)017901],measurementinduced disturbance(MID)[Phys.Rev.A 77(2008)022301],ameliorated MID[J.Phys.A:Math.Theor.44(2011)352002]and quantum dissonance[Phys.Rev.Lett.104(2010)080501].Quantum correlations captured with diferent approaches are compared and discussed so that their three distinct features are exposed.     

Pair-Breaking Critical Current Density of Two-Band Superconductor MgB2

[1]J. Nagamatsu, N. Nakagava, T. Muranaka, Y. Zenitani,and J. Akimitsu, Nature 410 (2001) 63. [2]C. Buzea and T. Yamashita, Supercond. Sci. Techn. 14(2001) R115. [3]S. Budko, G. Lapertot, C. Petrovic, C.E. Gunningham, N.Anderson, and P.C. Canfield, Phys. Rev. Lett. 86 (2001)1877. [4]H. Kotegawa, K. Ishida, Y. Kitaoka, T. Muranaka, and J. Akimitsu, Phys. Rev. Lett. 87 (2001) 127001. [5]J. Kortus, I.I. Mazin, K.D. Belashchenko, V.P. Antropov,and L.L. Boyer, Phys. Rev. Lett. 87 (2001) 4656. [6]A. Liu, I.I. Mazin, and J. Kortus, Phys. Rev. Lett. 87(2001) 087005. [7]X.K. Chen, M.J. Konstantinovich, J.C. Irwin, D.D.Lawrie, and J.P. Frank, Phys. Rev. Lett. 87 (2001)157002. [8]H. Giublio, D. Roditchev, W. Sacks, R. Lamy, D.X.Thanh, J. Kleins, S. Miraglia, D. Fruchart, J. Markus,and P. Monod, Phys. Rev. Lett. 87 (2001) 177008. [9]F. Bouquet, R.A. Fisher, N.E. Phillips, D.G. Hinks, and J.D. Jorgensen, Phys. Rev. Lett. 87 (2001) 04700. [10]S.V. Shulga, S.-L. Drechsler, H. Echrig, H. Rosner, and W. Pickett, Cond-mat/0103154 (2001). [11]A.A. Golubov, J. Kortus, O.V. Dolgov, O. Jepsen, Y.Kong, O.K. Andersen, B.J. Gibson, K. Ahn, and R.K.Kremer, J. Phys. Condens. Matter 14 (2002) 1353. [12]H. Doh, M. Sigrist, B.K. Chao, and Sung-Ik Lee, Phys.Rev. Lett. 85 (1999) 5350. [13]I.N. Askerzade, N. Guclu, and A. Gencer, Supercond. Sci.Techn. 15 (2002) L13. [14]I.N. Askerzade, N. Guclu, A. Gencer, and A. Kiliq, Supercond. Sci. Techn. 15 (2002) L17. [15]I.N. Askerzade and A. Gencer, J. Phys. Soc. Jpn. 71(2002) 1637. [16]I.N. Askerzade, Physica C 397 (2003) 99. [17]V.V. Anshukova, B.M. Bulychev, A.I. Golovashkin, L.I.Ivanova, A.A. Minakov, and A.P. Rusakov, Phys. Solid State 45 (2003) 1207. [18]A.A. Abrikosov, Fundamentals of the Theory of Metals,North-Holland, Amsterdam (1988). [19]M.N. Kunchur, S.I. Lee, and W.N. Kang, Phys. Rev. B 68 (2003) 064516.     

Angular Distributions for

[1]G.T.Bodwin,E.Braaten,and G.P.Lepage,Phys.Rev.D 51 (1995) 1125;[Erratum-ibid.D 55 (1997) 5853][arXiv:hep-ph/9407339]; J.Boltz,P.Kroll,and G.A.Schulre,Phys.Lett.B 392 (1997) 198; J.Boltz,P.Kroll,and G.A.Schulre,Phys.J.C 2 (1998) 705. [2]S.M.Wong,Nucl.Phys.A 674 (2000) 185; S.M.Wong,Eur.Phys.J.C 14 (2000) 643. [3]J.Z.Bai,Y.Ban,J.G.Bian,et al.,Phys.Rev.D 67 (2003)112001. [4]M.Jacob and G.C.Wick,Ann.Phys.7 (1959) 404. [5]S.U.Chung,Phys.Rev.D 48 (1993) 1225; S.U.Chung,Phys.Rev.D 57 (1998) 431; B.S.Zou and D.V.Bugg,Eur.Phys.J.A 16 (2003) 537. [6]Particle Data Group,Phys.Lett.B 592 (2004) pp.924-966. [7]M.A.Doncheski,et al.,Phys.Rev.D 42 (1990) 2293; E.Eichten,et al.,Phys.Rev.D 21 (1980) 203; K.J.Sebastian,Phys.Rev.D 26 (1982) 2295; G.Hardekopf and J.Sucher,Phys.Rev.D 25 (1982) 2938; R.McClary and N.Byers,Phys.Rev.D 28 (1983) 1692; P.Moxhay and J.L.Rosner,Phys.Rev.D 28 (1983) 1132. [8]B.S.Zou and F.Hussain,Phys.Rev.C 67 (2003) 015204.     

Mixing,ergodicity and slow relaxation phenomena

Investigations on diffusion in systems with memory [I.V.L. Costa, R. Morgado, M.V.B.T. Lima, F.A. Oliveira, Europhys. Lett. 63 (2003) 173] have established a hierarchical connection between mixing, ergodicity, and the fluctuation–dissipation theorem (FDT). This hierarchy means that ergodicity is a necessary condition for the validity of the FDT, and mixing is a necessary condition for ergodicity. In this work, we compare those results with recent investigations using the Lee recurrence relations method [M.H. Lee, Phys. Rev. B 26 (1982) 2547; M.H. Lee, Phys. Rev. Lett. 87 (2001) 250601; M.H. Lee, J. Phys. A: Math. Gen. 39 (2006) 4651]. Lee shows that ergodicity is violated in the dynamics of the electron gas [M.H. Lee, J. Phys. A: Math. Gen. 39 (2006) 4651]. This reinforces both works and implies that the results of [I.V.L. Costa, R. Morgado, M.V.B.T. Lima, F.A. Oliveira, Europhys. Lett. 63 (2003) 173] are more general than the framework in which they were obtained. Some applications to slow relaxation phenomena are discussed.     

基于六粒子纠缠态和Bell态测量的量子信息分离

通过介绍六粒子纠缠态的新应用研究,提出了一个二粒子任意态的信息分离方案.在这个方案中,发送者Alice、控制者Charlie和接受者Bob共享一个六粒子纠缠态,发送者先执行两次Bell基测量|然后控制者执行一次Bell基测量|最后接受者根据发送者和控制者的测量结果,对自己拥有的粒子做适当的幺正变换,从而能够重建要发送的二粒子任意态.这个信息分离方案是决定性的,即成功概率为100%.与使用相同的量子信道进行二粒子任意态的信息分离方案相比,本文提出的方案只需要进行Bell基测量而不需要执行多粒子的联合测量,从而使得这个方案更简单、更容易,并且在目前的实验室技术条件下是能够实现的.     

Nanoscale oscillatory fracture propagation in metallic glasses

We describe the oscillatory crack propagation for small propagation velocities at the atomistic scale that was recently observed for brittle metallic glasses [G. Wang, Y.T. Wang, Y.H. Liu, M.X. Pan, D.Q. Zhao, W.H. Wang, Appl. Lett. 89 (2006) 121909; G. Wang, D.Q. Zhao, H.Y. Bai, M.X. Pan, A.L. Xia, B.S. Han, X.K. Xi, Y. Wu, W.H. Wang, Phys. Rev. Lett. 98 (2007) 235501]. Based on a simple model of crack propagation [Y. Braiman, T. Egami, Phys. Rev. E, 77 (2008) 065101(R)], we derived and analyzed expressions for the feature size, oscillation period, and maximum strain accumulated in the material.     

Some remarks on finite-gap solutions of the Ernst equation

The relationship between the class of algebro-geometrical (finite-gap) solutions of the Ernst equation constructed by Korotkin and Matveev [Theor. Math. Phys. 77 (1989) 1018; St. Petersburg Math. J. 1 (1990) 379] and the solutions recently constructed by Meinel and Neugebauer [Phys. Lett. A 210 (1996) 160] is discussed. A new formula for the general algebro-geometrical solution is obtained.     

Velocity selection for ultracold atoms using mazer action in a bimodal cavity

In this paper, we discuss the velocity selection of ultracold three-level atoms in Λ configuration using a mazer. Our model is the same as discussed by Arun et al. [R. Arun, G.S. Agarwal, M.O. Scully, H. Walther, Phys. Rev. A 62 (2000) 023809] for mazer action in a bimodal cavity. We show that the initial Maxwellian velocity distribution of ultracold atoms can be narrowed due to the presence of resonances in the transmission through dressed-state potential. When the atoms are initially prepared in one of the two lower atomic states then significantly better velocity selectivity is obtained due to the presence of dark states.     

Comment on “Computer Algebra and Solutions to the Karamoto-Sivashinsky Equation” [Commun. Theor. Phys. （Beijing, China） 43 （2005） 39]

In a recent article [Commun. Theor. Phys. （Beijing, China） 43 （2005） 39], Xie et al. improved the extended tanh function method by introducing a generalized Riccati equation and its new solutions. Then they choose the Karamoto-Sivashinsky （KS） equation to illustrate their approach and obtain many exact solutions of the KS equation. So they claim that, by using their method, one not only can successfully recover the previously known formal solutions but also construct new and more general formal solutions for some nonlinear evolution equations. In this comment, we will show that the claim is incorrect.     

Bouncing branes

We investigate (4+1)- and (5+0)-dimensional gravity coupled to a non-compact scalar field sigma-model in the context of a single-brane-world scenario with separable metric and a bulk fluid. We briefly discuss the standard cosmological solutions and the family of warp factors (which includes both the original Randall–Sundrum [Phys. Rev. Lett. 83 (1999) 3370, hep-ph/9905221; Phys. Rev. Lett. 83 (1999) 4690, hep-th/9906064] solution and the solution of Kachru, Schulz and Silverstein [H.A. Chamblin, H.S. Reall, Nucl. Phys. B 562 (1999) 133, hep-th/9903225; S. Kachru, M. Schulz, E. Silverstein, Phys. Rev. D 62 (2000) 045021, hep-th/0001206]) for the case of a rolling fifth radius [C. Kennedy, E.M. Prodanov, Phys. Lett. B 488 (2000) 11, hep-th/0003299]. We show how this model can be adjusted so that it describes the standard cosmology on a self-tuning domain wall (with static fifth radius) [C. Kennedy, E.M. Prodanov, hep-th/0010202] and we discuss the solutions. Searching for a possible relation to the negative Euclidean stress energy, appearing in the Giddings and Strominger's axion induced topology change in quantum gravity and string theory [S.B. Giddings, A. Strominger, Nucl. Phys. B 306 (1988) 890], we modify the non-compact sigma-model into a single-field model (with a rolling fifth radius, separable metric, and no bulk fluid) for the more general case of a brane with non-zero curvature parameter. We find a solution (with a Kachru–Schulz–Silverstein warp factor [Phys. Rev. D 62 (2000) 045021, hep-th/0001206]), representing a Tolman wormhole for a brane with Lorentz metric and for a brane with positive definite metric.     

Study on electron scattering in solid targets using accurate transport cross-sections

The Vicanek and Urbassek theory [M. Vicanek, H.M. Urbassek, Phys. Rev. B 44 (1991) 7234] combined with a Monte Carlo simulation are used to investigate the transport of 0.5-4 keV electrons in solid targets. The cross-sections used to describe the electron transport have been calculated via a new improved version of the approximate analytical expression given by Jablonski [A. Jablonski, Phys. Rev. B 58 (1998) 16470]. Some applications are presented here for the calculation of electron backscattering coefficient in semi-infinite Al and Cu targets. The obtained results accord with success with the experiment and clearly represent an improvement with respect to previous theoretical calculations.     

Structure of the hydrogen stabilized MgO(1 1 1)-(1 × 1) surface from low energy electron diffraction (LEED)

A structural study has been performed on the MgO(1 1 1)-(1 × 1) surface by low energy electron diffraction (LEED) using experimental data obtained with a delay-line-detector LEED (DLD-LEED) system to minimize electron damage. It was found that the surface is terminated by a hydroxide layer with the top O-Mg interlayer spacing equal to 1.02 Å, which is close to the spacings between Mg and O planes in bulk brucite crystals (Mg(OH)₂). This is in good agreement with a recent study using photoelectron diffraction (PhD) spectroscopy and density functional theory calculation (DFT) [V.K. Lazarov, R. Plass, H.-C. Poon, D.K. Saldin, M. Weinert, S.A. Chambers, M. Gajdardziska-Josifovska, Phys. Rev. B 71 (2005) 115434]. The second interlayer spacing shows a small expansion of 3% and the third is bulk-like, while the DFT calculation predicted that the spacings below the top one are all bulk-like. This result clearly favors hydroxylation [K. Refson, R.A. Wogelius, D.G. Fraser, M.C. Payne, M.H. Lee, V. Milman, Phys. Rev. B 52 (1995) 10823] as a way of stabilizing the MgO(1 1 1) surface at low temperature over metallization, which has a top layer spacing of 0.86 Å for O termination and 1.25 Å for Mg termination [Lazarov et al. 2005; T. Tsukada, T. Hoshino, Phys. Soc. Jpn. 51 (1982) 2562, J. Goniakowski, C. Noguera, Phys. Rev. B 60 (1999) 16120].     

Improvement on Quantum Secure Direct Communication with W State in Noisy Channel

An improvement （Y-protocol） [Commun. Theor. Phys. 49 （2008） 103] on the quantum secure direct communication with W state （C-protocol） [Chin. Phys. Lett. 23 （2006） 290] is proposed by Yuan et al. The quantum bit error rate induced by eavesdropper is 4.17% in C-protocol and 6.25% in Y-protocoL In this paper, another improvement on C-protocol is given. The quantum bit error rate of the eavesdropping will increase to 8.75%, which is 1.1 times larger than that in C-protocol and 0.4 times larger than that in Y-protocol.