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

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

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Top Quark Flavor Changing Decay t

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Study of Strange Quark Mass in CFL Phase

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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.     

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.     

Dynamics of Two-Photon Lasers with

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Casimir interaction of dielectric gratings

We derive an exact solution for the Casimir force between two arbitrary periodic dielectric gratings and illustrate our method by applying it to two nanostructured silicon gratings. We also reproduce the Casimir force gradient measured recently [H. B. Chan, Y. Bao, J. Zou, R. A. Cirelli, F. Klemens, W. M. Mansfield, and C. S. Pai, Phys. Rev. Lett. 101, 030401 (2008)10.1103/PhysRevLett.101.030401] between a silicon grating and a gold sphere taking into account the material dependence of the force. We find good agreement between our theoretical results and the measured values both in absolute force values and the ratios between the exact force and proximity force approximation predictions.     

Comment on: “Globally exponential synchronization in array of asymmetric coupled neural networks” [Phys. Lett. A 369 (2007) 444]

In this Letter, we indicate that the proposed sufficient condition in Letter [J.Q. Lu, W.C. Ho, M. Liu, Phys. Lett. A 369 (2007) 444] does not hold when coupling matrix G satisfies Assumption 3 in Letter [J.Q. Lu, W.C. Ho, M. Liu, Phys. Lett. A 369 (2007) 444]. Besides, there are some mistakes in deducing Theorem 1. The mistakes have been corrected and a correct version is given in this Letter.     

On the geometry and homology of certain simple stratified varieties

We study certain mild degenerations of algebraic varieties which appear in the analysis of a large class of supersymmetric theories, including superstring theory. We analyze Witten’s σ-model [Nucl. Phys. B 403 (1993) 159] and find that the non-transversality of the superpotential induces additional singularities and a stratification of the ground state variety. This stratified variety admits certain homology groups such that ⊕_qH^2q satisfies the “Kähler package” of requirements [Ann. Math. Studies 102 (1982) 303]. Also, this ⊕_qH^2q extends the “flopped” pair of small resolutions [Nucl. Phys. B 416 (1994) 414; Nucl. Phys. B 330 (1990) 49; Commun. Math. Phys. 119 (1988) 431] to an “(exo)flopped” triple, and is compatible with both mirror symmetry [S.-T. Yau (Ed.), Mirror Manifolds, International Press, Hong Kong, 1990; B. Greene, S.-T. Yau (Eds.), Mirror Manifolds II, International Press, Hong Kong, 1996] and string theory [Mod. Phys. Lett. A 12 (1997) 521; Nucl. Phys. B 451 (1995) 96] results. Finally, we revisit the conifold transition [Nucl. Phys. B 330 (1990) 49] as it applies in our formalism.     

Topologically protected qubits as minimal Josephson junction arrays with non-trivial boundary conditions: A proposal

Recently a one-dimensional closed ladder of Josephson junctions has been studied [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Phys. Lett. A 372 (2008) 2464] within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. That led us to predict the emergence of a topological order in such a system [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter we analyze the ground states and the topological properties of fully frustrated Josephson junction arrays (JJA) arranged in a Corbino disk geometry for a variety of boundary conditions. In particular minimal configurations of fully frustrated JJA are considered and shown to exhibit the properties needed in order to build up a solid state qubit, protected from decoherence. The stability and transformation properties of the ground states of the JJA under adiabatic magnetic flux changes are analyzed in detail in order to provide a tool for the manipulation of the proposed qubit.     

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.     

Comment on “The Imbert-Fedorov shift of paraxial light beams”

Here I argue that Liu and Li [B.-Y. Liu, C.-F. Li, Opt. Commun. 281 (2008) 3427] reproduce calculations of the Imbert-Fedorov transverse shift previously made in a number of other works. However, it has recently been shown that these results are not valid for standard uniformly polarized beams. The corrected values of the Imbert-Fedorov shift were derived in papers [K.Y. Bliokh, Y.P. Bliokh, Phys. Rev. Lett. 96 (2006) 073903; Phys. Rev. E 75 (2007) 066609] and confirmed by recent measurements [O. Hosten, P. Kwiat, Science 319 (2008) 787] with a great accuracy.     

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Fully frustrated Josephson junction ladders with Mobius boundary conditions as topologically protected qubits

We show how to realize a “protected” qubit by using a fully frustrated Josephson junction ladder (JJL) with Mobius boundary conditions. Such a system has been recently studied within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. The relevance of a “closed” geometry has been fully exploited in relating the topological properties of the ground state of the system to the presence of half flux quanta and the emergence of a topological order has been predicted [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter the stability and transformation properties of the ground states under adiabatic magnetic flux change are analyzed and the deep consequences on the realization of a solid state qubit, protected from decoherence, are presented.     

Phase structure of four-dimensional gonihedric spin system

We perform Monte Carlo simulations of a gauge invariant spin system which describes random surfaces with gonihedric action in four dimensions. The Hamiltonian is a mixture of one-plaquette and additional two- and three-plaquette interaction terms with specially adjusted coupling constants [G.K. Savvidy, F.J. Wegner, Nucl. Phys. B 413 (1994) 605, G.K. Savvidy, K.G. Savvidy, Phys. Lett. B 324 (1994) 72] For the system with the large self-intersection coupling constant k we observe the second-order phase transition at temperature β_c - 1.75. The string tension is generated by quantum fluctuations as it was expected theoretically [G.K. Savvidy, K.G. Savvidy, Mod. Phys. Lett. A 8 (1993) 2963]. This result suggests the existence of a noncritical string in four dimensions. For smaller values of k the system undergoes the first order phase transition and for k close to zero exhibits a smooth crossover.     

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.     

Nonlinear diffusion of indirect excitons in an ideal bilayer with an in-plane harmonic trap

The nonlinear diffusion of the spatially indirect excitons in an ideal bilayer with an in-plane harmonic trap is investigated based on the theories developed by Ivanov [A.L. Ivanov, Europhys. Lett. 59 (2002) 586; A.L. Ivanov, J. Phys.: Condens. Matter 16 (2004) S3629] and Rapaport et al. [R. Rapaport, G. Chen, S. Simon, O. Mitrofanov, L. Pfeiffer, P.M. Platzman, Phys. Rev. B 72 (2005) 075428]. A nonlinear equation for the diffusion of the indirect excitons in this structure is established. The two-dimensional density of the indirect excitons in this structure is calculated. The calculations show that the density adjacent to the trap center for different exciton temperatures can remain very high even long after the photo-excitation because of the confinement of the in-plane harmonic trap, and that the indirect excitons gather several tens of μm away from the trap center. The calculations are in good agreement qualitatively with the experimental results of Voros et al. [Z. Voros, D.W. Snoke, L. Pfeiffer, K. West, Phys. Rev. Lett. 97 (2006) 016803] and prove that an in-plane harmonic trap can indeed keep an exciton gas dense near its center.