Dimensional Reduction via Noncommutative Spacetime: Bootstrap and Holography

Unlike noncommutative space, when space and time are noncommutative, it seems necessary to modify the usual scheme of quantum mechanics. We propose in this paper a simple generalization of the time evolution equation in quantum mechanics to incorporate the feature of a noncommutative spacetime. This equation is much more constraining than the usual Schr\"odinger equation in that the spatial dimension noncommuting with time is effectively reduced to a point in low energy. We thus call the new evolution equation the spacetime bootstrap equation, the dimensional reduction called for by this evolution seems close to what is required by the holographic principle. We will discuss several examples to demonstrate this point.Comment: 15 pages, harvmac. v2: typos corrected and some changes mad

Measuring CP Violating Phases at a Future Linear Collider

At a future Linear Collider one will be able to determine the masses of charginos and neutralinos and their pair production cross sections to high accuracies. We show how systematically including the cross sections into the analysis improves the measurement of the underlying mass parameters, including potential CP violating phases. In addition, we investigate how experimental errors will affect the determination of these parameters. We present a first estimate on the lower limit of observable small phases and on the accuracy in determining large phases.Comment: 10 pages, 6 figures, RevTeX3.1, Version to be published in Physics Letters B, physics setup improved, figures added, conclusions unchange

Associated Charmonium Production in Low Energy p-pbar Annihilation

The QCD mechanisms underlying the exclusive strong decays and hadronic production amplitudes of charmonium remain poorly understood, despite decades of study and an increasingly detaled body of experimental information. One set of hadronic channels of special interest are those that include baryon-antibaryon states. These are being investigated experimentally at BES and CLEO-c in terms of their baryon resonance content, and are also of interest for the future PANDA experiment, in which charmonium and charmonium hybrids will be produced in p-pbar annihilation in association with light mesons. In this paper we develop a simple initial-state light meson emission model of the near-threshold associated charmonium production processes p pbar -> pi0 ccbar, and evaluate the differential and total cross sections for these reactions in this model. (Here we consider the ccbar states eta_c, J/psi, psi', chi_0 and chi_1.) The predicted near-threshold cross section for p pbar -> pi0 J/psi is found to be numerically similar to two previous theoretical estimates, and is roughly comparable to the (sparse) existing data for this process. The theoretical charmonium angular distributions predicted by this model are far from isotropic, which may be of interest for PANDA detector design studies.Comment: 6 pages, 4 figures, uses graphicx and feynm

Production and rescattering of strange baryons at SPS energies in a transport model with hadron potentials

A mean-field potential version of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is used to investigate the production of strange baryons, especially the $\Lambda$s and $\overline{\Lambda}$s, from heavy ion collisions at SPS energies. It is found that, with the consideration of both formed and pre-formed hadron potentials in UrQMD, the transverse mass and longitudinal rapidity distributions of experimental data of both $\Lambda$s and $\overline{\Lambda}$s can be quantitatively explained fairly well. Our investigation also shows that both the production mechanism and the rescattering process of hadrons play important roles in the final yield of strange baryons.Comment: 15 pages, 7 figure

Performance analysis of the IEEE 802.11e block ACK scheme in a noisy channel

A block ACK (BTA) scheme has been proposed in IEEE 802.11e to improve medium access control (MAC) layer performance. It is also a promising technique for next-generation high-speed wireless LANs (WLANs) such as IEEE 802.11n. We present a theoretical model to evaluate MAC saturation throughput of this scheme. This model takes into account the effects of both collisions and transmission errors in a noisy channel. The accuracy of this model is validated by NS-2 simulations