Supermembranes

An example is given of the spontaneous breaking of D = 4, N = 2 global supersymmetry down to N = 1. The example is a four-dimensional membrane in a six-dimensional supersymmetric gauge theory. The effective low-energy action for the membrane is a generalization of the Green—Schwarz covariant action.     

Supermembranes on black holes

We report a new family of supermembrane vacua possesing the Siegel symmetry. This family consists of bosonic solutions of supermembrane field equations and describes static, toroidal membranes in d=11 black hole spacetimes. The black holes we consider are obtained by embedding the d=4 Reissner-Nordström solutions into d=11, N=1 supergravity. We show that supermembranes pick, as their backgrounds, only the extreme Reissner-Nordström black holes and require the d=4 magnetic charge to be non-zero. Moreover, the membranes on dyonic holes can be interpreted, at the linearized level, as fluctuations of the membranes on magnetically charged holes. The quantisation around the toroidal membranes on the magnetically charged, extreme black holes therefore poses itself as an interesting problem.     

Supermembranes and the signature of spacetime

We consider extended objects with s space and t time world-volume dimensions moving in a spacetime with S⩾ s space and T⩾t time dimensions. The requirements of spacetime supersymmetry and world-volume fermionic gauge invariance severely restrict the possible values of S and T. If we furthermore insist that the transverse group SO(S − s, T−t) be compact to avoid ghosts, then t=T. The results may be interpreted as a set of superconformal field theories with s+t⩽6 and N⩽8 whose superconformal groups are in one-to-one correspondence with those in Nahm's classification. Although the choice t = T = 1 is not uniquely singled out, it does seem to play a preferred role.     

非零色散位移光纤的改进设计及制造

介绍了一种新颖的非零色散位移光纤结构设计方法及其MCVD+OVD制造工艺,所制备的光纤有效面积达到71 μm2以上.采用关键结构区域精确微扰方法,改进了光纤的色散特性.1550 nm处色散斜率由0.0715 ps/(nm2·km),分别减小至0.0605 ps/(nm2·km),0.0466 ps/(nm2·km),零色散波长由1500 nm附近移至1450 nm以下.测量表明,所得光纤具有优越的光学传输特性、抗弯曲性能和熔接性能,适用于C+L和S+C+L工作波长的大容量高速率长距离密集波分复用系统.光纤关键结构区域精确微扰是改进光纤性能的一种有效方法,该方法不限于MCVD工艺和非零色散位移光纤,对新型光纤的设计和生产具有积极的指导意义.     

High-Energy Physics with Particles Carrying Non-Zero Orbital Angular Momentum

Thanks to progress in optics in the past two decades, it is possible to create photons carrying well-defined non-zero orbital angular momentum (OAM). Boosting these photons into high-energy range preserving their OAM seems feasible. Intermediate energy electrons with OAM have also been produced recently. One can, therefore, view OAM as a new degree of freedom in high-energy collisions and ask what novel insights it can bring. Here we discuss generic features of scattering processes involving twisted particles in the initial state. We show that they make it possible to perform a Fourier analysis of a plane wave cross section with respect to the azimuthal angles of the initial particles, and to probe the autocorrelation function of the amplitude, a quantity inaccessible in plane wave collisions.     

非零色散位移光纤的制造新工艺研究

介绍了一种新的改进化学气相沉积法(MCVD)+气相轴向沉积法(VAD)预制棒制备工艺,该工艺按照归一化波导结构进行工艺设计和参数控制,即采用MCVD法制备归一化结构参数轴向一致的芯棒,然后采用VAD法轴向沉积相应的外包层,从而得到波导结构轴向均匀一致的预制棒.采用新工艺实验研究了非零色散位移光纤的制造过程,成功制造了波...     

Chaotic Temperature Dependence at Zero Temperature

We present a class of examples of nearest-neighbour, bounded-spin models, in which the low-temperature Gibbs measures do not converge as the temperature is lowered to zero, in any dimension.     

Non-Kaehler Heterotic String Compactifications with Non-Zero Fluxes and Constant Dilaton

We construct new explicit compact supersymmetric valid solutions with non-zero field strength, non-flat instanton and constant dilaton to the heterotic equations of motion in dimension six. We present balanced Hermitian structures on compact nilmanifolds in dimension six satisfying the heterotic supersymmetry equations with non-zero flux, non-flat instanton and constant dilaton which obey the three-form Bianchi identity with curvature term taken with respect to either the Levi-Civita, the (+)-connection or the Chern connection. Among them, all our solutions with respect to the (+)-connection on the compact nilmanifold M ₃ satisfy the heterotic equations of motion.     

Universal Physics of 2+1 Particles with Non-Zero Angular Momentum

The zero-energy universal properties of scattering between a particle and a dimer that involves an identical particle are investigated for arbitrary scattering angular momenta. For this purpose, we derive an integral equation that generalises the Skorniakov?CTer-Martirosian equation to the case of non-zero angular momentum. As the mass ratio between the particles is varied, we find various scattering resonances that can be attributed to the appearance of universal trimers and Efimov trimers at the collisional threshold.     

一种高温下高灵敏光纤光栅温度传感器的制作方法

提出一种充分利用光纤光栅所能承受的应变量, 显著提高了光纤光栅温度传感器在高温下的灵敏度的方法.在常温下制作传感器时, 根据传感器需要测量的温度设置光纤光栅的预松长度;当温度升高到需要测量的温度时, 光纤光栅才开始被拉紧, 传感器才开始以高灵敏度方式工作.分析了预松长度和工作温度之间的关系.实验中, 当预松长度分别为0.2 mm、0.5 mm、0.6 mm时, 工作温度分别上升了25 ℃、50 ℃、61 ℃, 并且灵敏度(约675 pm/℃)基本不变.实验结果和理论分析吻合, 较好地证实了该方法的有效性.     

Modelling Quasicrystals at Positive Temperature

We consider a two-dimensional lattice model of equilibrium statistical mechanics, using nearest neighbor interactions based on the matching conditions for an aperiodic set of 16 Wang tiles. This model has uncountably many ground state configurations, all of which are nonperiodic. The question addressed in this paper is whether nonperiodicity persists at low but positive temperature. We present arguments, mostly numerical, that this is indeed the case. In particular, we define an appropriate order parameter, prove that it is identically zero at high temperatures, and show by Monte Carlo simulation that it is nonzero at low temperatures.     

Activation-Like Processes at Zero Temperature

We examine the possibility that a metastable quantum state could experiment a phenomenon similar to thermal activation but at zero temperature. To do that we study the real-time dynamics of the reduced Wigner function in a simple open quantum system: an anharmonic oscillator with a cubic potential linearly interacting with an environment of harmonic oscillators. Our results suggest that this activation-like phenomenon exists indeed as a consequence of the fluctuations induced by the environment and that its associated decay rate is comparable to the tunneling rate as computed by the instanton method, at least for the particular potential of the system and the distribution of frequencies for the environment considered in this paper. However, we are not able to properly deal with the term which leads to tunneling in closed quantum systems, and a definite conclusion cannot be reached until tunneling and activation-like effects are considered simultaneously.     

Dirac Equation at Finite Temperature

In this paper, we propose finite temperature Dirac equation, which can describe the quantum systems in an arbitrary temperature for a relativistic particle of spin-1/2. When the temperature T=0, it become Dirac equation. With the equation, we can study the relativistic quantum systems in an arbitrary temperature.     

Ward-Takahashi Identity at Finite Temperature

A new real time formalism, based on the closed-time-path Green's function theory (CTPGF),is employed to obtain Ward-llfrkahashi identities of QED at finite temperature. It is shown that WT identity in coordinate space is of the same covariant form aa that in vacuum field theory. A perturbative check is provided to #how that in momentum spze, Takahashi's iden tities hold only in a weak sense.     

有限温度下的Casimir效应

利用路径积分量子化方法,计算出两个平行的、理想的金属板之间,在有限温度下自由的量子电磁场和内部费米子单圈图对Casimir力的贡献.     

Asymptotic Entanglement Sudden Death in Two Atoms with Dipole–Dipole and Ising Interactions Coupled to a Radiation Field at Non-Zero Detuning

We investigate the time evolution and asymptotic behavior of a system of two two-level atoms (qubits) interacting off-resonance with a single mode radiation field. The two atoms are coupled to each other through dipole–dipole as well as Ising interactions. An exact analytic solution for the system dynamics that spans the entire phase space is provided. We focus on initial states that cause the system to evolve to entanglement sudden death (ESD) between the two atoms. We find that combining the Ising and dipole–dipole interactions is very powerful in controlling the entanglement dynamics and ESD compared with either one of them separately. Their effects on eliminating ESD may add up constructively or destructively depending on the type of Ising interaction (Ferromagnetic or anti-Ferromagnetic), the detuning parameter value, and the initial state of the system. The asymptotic behavior of the ESD is found to depend substantially on the initial state of the system, where ESD can be entirely eliminated by tuning the system parameters except in the case of an initial correlated Bell state. Interestingly, the entanglement, atomic population and quantum correlation between the two atoms and the field synchronize and reach asymptotically quasi-steady dynamic states. Each one of them ends up as a continuous irregular oscillation, where the collapse periods vanish, with a limited amplitude and an approximately constant mean value that depend on the initial state and the system parameters choice. This indicates an asymptotic continuous exchange of energy (and strong quantum correlation) between the atoms and the field takes place, accompanied by diminished ESD for these chosen setups of the system. This system can be realized in spin states of quantum dots or Rydberg atoms in optical cavities, and superconducting or hybrid qubits in linear resonators.     

The Scattering Length at Positive Temperature

A positive temperature analogue of the scattering length of a potential V can be defined via integrating the difference of the heat kernels of ??? and ${-\Delta + \frac{1}{2}V}$ , with ?? the Laplacian. An upper bound on this quantity is a crucial input in the derivation of a bound on the critical temperature of a dilute Bose gas (Seiringer and Ueltschi in Phys Rev B 80:014502, 2009). In (Seiringer and Ueltschi in Phys Rev B 80:014502, 2009), a bound was given in the case of finite range potentials and sufficiently low temperature. In this paper, we improve the bound and extend it to potentials of infinite range.     

Chiral Bag Model at Finite Temperature

By taking the thermodynamical contributions of the pion mesons cloud outside the bag into account,the chiral bag model is extended to finite temperature.The temperature dependence of the radius of the chiral bag and the critical temperature of quark deconfinement are given.     

Non-relativistic Quantum Theory at Finite Temperature

We propose the non-relativistic finite temperature quantum wave equations for a single particle and multiple particles. We give the relation between energy eigenvalues, eigenfunctions, transition frequency and temperature, and obtain some results: (1) when the degeneracies of two energy levels are same, the transition frequency between the two energy levels is unchanged when the temperature is changed. (2) When the degeneracies of two energy levels are different, the variance of transition frequency at two energy levels is direct proportion to temperature difference.     

The Cavity Method at Zero Temperature

In this note we explain the use of the cavity method directly at zero temperature, in the case of the spin glass on a lattice with a local tree like structure, which is the proper generalization of the usual Bethe lattice to frustrated problems. The computation is done explicitly in the formalism equivalent to one step replica symmetry breaking; we compute the energy of the global ground state, as well as the complexity of equilibrium states at a given energy. Full results are presented for a Bethe lattice with connectivity equal to three. The main assumptions underlying the one step cavity approach, namely the existence of many local ground states, are explicitely stated and discussed: some of the main obstacles towards a rigorous study of the problem with the cavity method are outlined.