Trapping the Kaluza-Klein scalar

The Kaluza-Klein unified theory predicts the existence of a Brans-Dicke type scalar field with = 0. Solar system experiments do, however, imply that gravitational scalar fields must be suppressed either by a very weak coupling to matter ( > 500) or a self-interaction. Here the consequences of a self-interaction potential of the Kaluza-Klein scalar are investigated. By suppressing the scalar field in this way, the one-body metric reduces to the Schwarzschild solution. The cosmologies of the scalar-tensor model are, however, very different from cosmologies of Einstein's theory, since here the time evolution of the cosmic scale-factor is determined only by the initial conditions. These may be chosen so that the theory is compatible with the hypothesis of primordial nucleosynthesis.     

Trapping of frenkel excitons

We calculate the trapping rate of a Frenkel exciton in the presence of a low concentration of traps. The analysis is based on a second-order perturbation calculation which is applicable to three-dimensional systems when the exciton bandwidth is large in comparison with the maximum single donor-single trap transfer rate. The variation of the transfer rate with exciton wave vector is commented on. Possible experimental tests of the theory are discussed.     

Trapping leidenfrost drops with crenelations

Drops placed on very hot solids levitate on a cushion of their own vapor, as discovered by Leidenfrost. This confers to these drops a remarkable mobility, which makes problematic their control and manipulation. Here we show how crenelated surfaces can be used to increase the friction of Leidenfrost drops by a factor on the order of 100, making them decelerate and be trapped on centimetric distances instead of the usual metric ones. We measure and characterize the friction force as a function of the design of the crenelations.     

多极场的电子云俘获效应研究

电子云效应限制了几台加速器的高束流密度运行,例如SLAC和KEK的B工厂,CERN的SPS与PS.本文运用辛流形上的1-form李摄动法研究了2n多极场的电子云俘获效应,结果发现在多极磁铁(n>1)的绝热区存在电子俘获     

Optical Fiber Trapping in Space

A novel dual-beam trapping system was proposed and discussed for a three-dimensional optical trapping of an object with large relative refractive index. From theoretical studies, we confirmed that our system was useful for manipulating objects in cosmic space.     

Trapping aspects in enhanced diffusion

We study the superlinear diffusion x ²(t) t , > 1, in layered media containing random velocity fields. The superlinear behavior holds in the case of random velocities along thex direction accompanied by diffusional motion in the space transverse to it. The transverse space can be either Euclidean, fractal, or ultrametric. For a one-dimensional transverse space we derive exact expressions for the higher moments of the displacement. Furthermore, we investigate the propagatorP(x, t) along thex direction and establish its scaling behavior. Our analysis highlights the resemblance between the stretched-Gaussian behavior of the propagator and the stretched-exponential form of the survivial probability in the trapping problem; both show late crossover behavior.This work is dedicated to Prof. George H. Weiss.     

Trapping single molecules by dielectrophoresis

We have trapped single protein molecules of R-phycoerythrin in an aqueous solution by an alternating electric field. A radio frequency voltage is applied to sharp nanoelectrodes and hence produces a strong electric field gradient. The resulting dielectrophoretic forces attract freely diffusing protein molecules. Trapping takes place at the electrode tips. Switching off the field immediately releases the molecules. The electric field distribution is computed, and from this the dielectrophoretic response of the molecules is calculated using a standard polarization model. The resulting forces are compared to the impact of Brownian motion. Finally, we discuss the experimental observations on the basis of the model calculations.     

Trapping levels in PbI2

A first investigation on trapping levels in PbI₂, performed by the Thermally Stimulated Current (TSC) technique, is presented. Three hole trapping centers are evidenced at 0.12, 0.29 and 0.59 eV above the valence band, with densities ranging between 8 × 10¹⁴ and 5 × 10¹⁶ cm^?3 and capture cross-sections between 8 × 10^?21 and 3 × 10^?17 cm². The center at 0.59 eV is likely responsible for the relatively short trapping time in PbI₂, as determined with nuclear techniques. By using a particular method, the behaviour of hole drift mobility along the layers as a function of temperature is determined for the first time. Finally, the presence of a spurious peak, not sensitive to irradiation, is reported and discussed.     

Trapping Horizons in Sultana-Dyer Space-Time

The Sultana-Dyer space-time is suggested as a model describing a black hole embedded in an expanding universe. Recently, its global structure is analyzed and the trapping horizons are shown. In the paper, by directly calculating theexpansions of the radial null vector fields normal to the space-like two-spheres foliating the trapping horizons, we find that the trapping horizon outside the event horizon in the Sultana-Dyer space-time is a past trapping horizon. Further, we find that the past trapping horizon is an outer, instantaneously degenerate or inner trapping horizon accordingly when the radial coordinate isless than, equal to or greater than some value.     

Rb原子的激光囚禁

用饱和吸收光谱法对二极管激光器进行稳频,使激光器的有效线宽小于１ＭＨｚ,并利用声光调制器使激光的频移量得到控制,满足了激光冷却与因禁原子对激光频率生和频 量的 Ｒｂ原子的激光囚禁。     

Trapping and spectroscopy of hydrogen

I review the results and techniques used by the MIT H↑ group to achieve a fractional resolution of 2 parts in 10¹² in the 1S–2S transition in hydrogen [Cesar, D. Fried, T. Killian, A. Polcyn, J. Sandberg, I.A. Yu, T. Greytak, D. Kleppner and J. Doyle, Two-photon spectroscopy of trapped atomic hydrogen, Phys. Rev. Lett. 77 (1996) 255.] With some improvements, this system should deliver 100 times higher resolution with an improved signal count rate getting us closer to an old advertised goal of a precision of 1 part in 10¹⁸. While these developments are very important for the proposed test of the CPT theorem through the comparison with anti-hydrogen, some of the techniques used with hydrogen are not applicable to anti-hydrogen and I discuss some difficulties and alternatives for the trapping and spectroscopy of anti-hydrogen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Trapping in the Random Conductance Model

We consider random walks on ? ^d among nearest-neighbor random conductances which are i.i.d., positive, bounded uniformly from above but whose support extends all the way to zero. Our focus is on the detailed properties of the paths of the random walk conditioned to return back to the starting point at time 2n. We show that in the situations when the heat kernel exhibits subdiffusive decay—which is known to occur in dimensions d≥4—the walk gets trapped for a time of order n in a small spatial region. This shows that the strategy used earlier to infer subdiffusive lower bounds on the heat kernel in specific examples is in fact dominant. In addition, we settle a conjecture concerning the worst possible subdiffusive decay in four dimensions.     

Resonance Trapping and Dynamical Phase Transitions

In the non-Hermitian quantum physics, resonance trapping occurs due to width bifurcation in the regime of overlapping resonances. It causes dynamical phase transitions in many-level quantum systems. In the present contribution, three different examples, observed experimentally, are considered. In any case, resonance trapping breaks the symmetry characteristic of the system at low level density due to the alignment of a few states with the scattering states of the environment.     

Trapping atoms in a gravitational cavity

This paper is devoted to the study of a new atomic cavity consisting of a single horizontal concave mirror placed in the earth gravitational field. Gravity, by bending the atomic trajectories, plays the role of a second mirror closing the cavity. We first discuss the stability criterion for this cavity, assuming that the mirror has a parabolic shape. We then derive the quantum mechanical modes of such a configuration, with particular emphasis on the paraxial (i.e., close to vertical) motion. Finally, we discuss the possibility of populating those modes from an initial cold atomic cloud dropped above the mirror.Laboratoire associé au CNRS et à l'Université Pierre et Marie Curie     

激光分离同位素过程中的布居囚禁

采用辍饰原子模型研究了四光子三步共振离化过程的布居囚禁，发现了一种与离化速率无关的布居囚禁。通过数值求解裸原子表象的含时薛定谔方程发现，适当选取激光频率与跃迁的失谐量，可以解除这种布居囚禁。     

Trapping of phase kinks in polyacetylene

Molecular orbital calculations with full geometry optimization using a semi-empirical tight-binding Hamiltonian for finite molecular models of phase kinks (solitons) in polyacetylene, (CH)_X′ were done. This bond alternation defect extends over many atoms from which only ～30 atoms are energetically important for stabilizing it. The neutral (spin-carying) phase kink is attracted by an energy on the meV scale to carbon atoms joining a non-hydrogen side-group, in contrast to charged phase kinks, where this attraction is estimated to be 100 to 1000 times larger.     

Optical Trapping with Focused Surface Waves

Near-field optical trapping can be realized with focused evanescent waves that are excited at the water–glass interface due to the total internal reflection, or with focused plasmonic waves excited on the water–gold interface. Herein, the performance of these two kinds of near-field optical trapping techniques is compared using the same optical microscope configuration. Experimental results show that only a single-micron polystyrene bead can be trapped by the focused evanescent waves, whereas many beads are simultaneously attracted to the center of the excited region by focused plasmonic waves. This difference in trapping behavior is analyzed from the electric field intensity distributions of these two kinds of focused surface waves and the difference in trapping behavior is attributed to photothermal effects due to the light absorption by the gold film.