Extracting Atoms on Demand with Lasers

We propose a scheme that allows to coherently extract cold atoms from a reservoir in a deterministic way. The transfer is achieved by means of radiation pulses coupling two atomic states which are object to different trapping conditions. A particular realization is proposed, where one state has zero magnetic moment and is confined by a dipole trap, whereas the other state with non-vanishing magnetic moment is confined by a steep microtrap potential. We show that in this setup a predetermined number of atoms can be transferred from a reservoir, a Bose-Einstein condensate, into the collective quantum state of the steep trap with high efficiency in the parameter regime of present experiments.Comment: 11 pages, 8 figure

New mechanism for the production of the extremely fast light particles in heavy-ion collisions in the Fermi energy domain

Employing a four-body classical model, various mechanisms responsible for the production of fast light particles in heavy ion collisions at low and intermediate energies have been studied. It has been shown that at energies lower than 50 A MeV, light particles of velocities of more than two times higher than the projectile velocities are produced due to the acceleration of the target light-particles by the mean field of the incident nucleus. It has also been shown that precision experimental reaction research in normal and inverse kinematics is likely to provide vital information about which mechanism is dominant in the production of fast light particles.Comment: 4 pages, 3 figures, LaTeX, to be published in Proceedings of VII International School-Seminar on Heavy Ion Physics, May 27 - June 1, 2002, Dubna, Russi

The meeting problem in the quantum random walk

We study the motion of two non-interacting quantum particles performing a random walk on a line and analyze the probability that the two particles are detected at a particular position after a certain number of steps (meeting problem). The results are compared to the corresponding classical problem and differences are pointed out. Analytic formulas for the meeting probability and its asymptotic behavior are derived. The decay of the meeting probability for distinguishable particles is faster then in the classical case, but not quadratically faster. Entangled initial states and the bosonic or fermionic nature of the walkers are considered

Measurement induced quantum-classical transition

A model of an electrical point contact coupled to a mechanical system (oscillator) is studied to simulate the dephasing effect of measurement on a quantum system. The problem is solved at zero temperature under conditions of strong non-equilibrium in the measurement apparatus. For linear coupling between the oscillator and tunneling electrons, it is found that the oscillator dynamics becomes damped, with the effective temperature determined by the voltage drop across the junction. It is demonstrated that both the quantum heating and the quantum damping of the oscillator manifest themselves in the current-voltage characteristic of the point contact.Comment: in RevTex, 1 figure, corrected notatio

Measurement of the Proton's Neutral Weak Magnetic Form Factor

We report the first measurement of the parity-violating asymmetry in elastic electron scattering from the proton. The asymmetry depends on the neutral weak magnetic form factor of the proton which contains new information on the contribution of strange quark-antiquark pairs to the magnetic moment of the proton. We obtain the value $G_M^Z= 0.34 \pm 0.09 \pm 0.04 \pm 0.05$ n.m. at $Q^2=0.1$ (GeV/c)${}^2$.Comment: 4 pages TEX, text available at http://www.krl.caltech.edu/preprints/OAP.htm

Second best toll and capacity optimisation in network: solution algorithm and policy implications

This paper looks at the first and second-best jointly optimal toll and road capacity investment problems from both policy and technical oriented perspectives. On the technical side, the paper investigates the applicability of the constraint cutting algorithm for solving the second-best problem under elastic demand which is formulated as a bilevel programming problem. The approach is shown to perform well despite several problems encountered by our previous work in Shepherd and Sumalee (2004). The paper then applies the algorithm to a small sized network to investigate the policy implications of the first and second-best cases. This policy analysis demonstrates that the joint first best structure is to invest in the most direct routes while reducing capacities elsewhere. Whilst unrealistic this acts as a useful benchmark. The results also show that certain second best policies can achieve a high proportion of the first best benefits while in general generating a revenue surplus. We also show that unless costs of capacity are known to be low then second best tolls will be affected and so should be analysed in conjunction with investments in the network

The play's the thing

For very understandable reasons phenomenological approaches predominate in the field of sensory urbanism. This paper does not seek to add to that particular discourse. Rather it takes Rorty’s postmodernized Pragmatism as its starting point and develops a position on the role of multi-modal design representation in the design process as a means of admitting many voices and managing multidisciplinary collaboration. This paper will interrogate some of the concepts underpinning the Sensory Urbanism project to help define the scope of interest in multi-modal representations. It will then explore a range of techniques and approaches developed by artists and designers during the past fifty years or so and comment on how they might inform the question of multi-modal representation. In conclusion I will argue that we should develop a heterogeneous tool kit that adopts, adapts and re-invents existing methods because this will better serve our purposes during the exploratory phase(s) of any design project that deals with complexity

Comparative Analysis of the Mechanisms of Fast Light Particle Formation in Nucleus-Nucleus Collisions at Low and Intermediate Energies

The dynamics and the mechanisms of preequilibrium-light-particle formation in nucleus-nucleus collisions at low and intermediate energies are studied on the basis of a classical four-body model. The angular and energy distributions of light particles from such processes are calculated. It is found that, at energies below 50 MeV per nucleon, the hardest section of the energy spectrum is formed owing to the acceleration of light particles from the target by the mean field of the projectile nucleus. Good agreement with available experimental data is obtained.Comment: 23 pages, 10 figures, LaTeX, published in Physics of Atomic Nuclei v.65, No. 8, 2002, pp. 1459 - 1473 translated from Yadernaya Fizika v. 65, No. 8, 2002, pp. 1494 - 150