N-fold way simulated tempering for pairwise interaction point processes

Pairwise interaction point processes with strong interaction are usually difficult to sample. We discuss how Besag lattice processes can be used in a simulated tempering MCMC scheme to help with the simulation of such processes. We show how the N-fold way algorithm can be used to sample the lattice processes efficiently and introduce the N-fold way algorithm into our simulated tempering scheme. To calibrate the simulated tempering scheme we use the Wang-Landau algorithm

Spectrum of low-lying s3QQˉs^{3}Q\bar{Q} configurations with negative parity

Spectrum of low-lying five-quark configurations with strangeness quantum number $S=-3$ and negative parity is studied in three kinds of constituent quark models, namely the one gluon exchange, Goldstone Boson exchange, and instanton-induced hyperfine interaction models, respectively. Our numerical results show that the lowest energy states in all the three employed models are lying at $\sim$1800 MeV, about 200 MeV lower than predictions of various quenched three-quark models. In addition, it is very interesting that the state with the lowest energy in one gluon exchange model is with spin 3/2, but 1/2 in the other two models.Comment: Version published in Phys. Rev.

A Simplified Scheme of Estimation and Cancellation of Companding Noise for Companded Multicarrier Transmission Systems

Nonlinear companding transform is an efficient method to reduce the high peak-to-average power ratio (PAPR) of multicarrier transmission systems. However, the introduced companding noise greatly degrades the bit-error-rate (BER) performance of the companded multicarrier systems. In this paper, a simplified but effective scheme of estimation and cancellation of companding noise for the companded multicarrier transmission system is proposed. By expressing the companded signals as the summation of original signals added with a companding noise component, and subtracting this estimated companding noise from the received signals, the BER performance of the overall system can be significantly improved. Simulation results well confirm the great advantages of the proposed scheme over other conventional decompanding or no decompanding schemes under various situations

Vapor-liquid phase separator studies

A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters

Written in stone: a clinical case of compulsive note taking

Federal University of Pernambuco Neuropsychiatric DepartmentFederal University of São Paulo Department of PsychiatryHospital do Servidor Público Estadual de São PauloUNIFESP, Department of PsychiatrySciEL

Horizon Mass Theorem

A new theorem for black holes is found. It is called the horizon mass theorem. The horizon mass is the mass which cannot escape from the horizon of a black hole. For all black holes: neutral, charged or rotating, the horizon mass is always twice the irreducible mass observed at infinity. Previous theorems on black holes are: 1. the singularity theorem, 2. the area theorem, 3. the uniqueness theorem, 4. the positive energy theorem. The horizon mass theorem is possibly the last general theorem for classical black holes. It is crucial for understanding Hawking radiation and for investigating processes occurring near the horizon.Comment: A new theorem for black holes is establishe

XMM-Newton Observations of High Redshift Quasars

We report on our XMM observations of the high redshift quasars BR 2237--0607 (z=4.558) and BR 0351--1034 (z=4.351), together with 14 other z>4 objects found in the XMM public archive. Contrary to former reports, we do not find high redshift radio-loud quasars to be more absorbed than their radio-quiet counterparts. We find that the optical to X-ray spectral index alpha-ox is correlated with the luminosity density at 2500 A, but does not show a correlation with redshift. The mean 2-10 keV power-law slope of the 9 high redshift radio-quiet quasars in our sample for which a spectral analysis can be performed is alpha-x1.23+-0.48, similar to alpha-x=1.19 found from the ASCA observations of low redshift Narrow-Line Seyfert 1 galaxies (NLS1s), and significantly different from alpha-x=0.78 found for low redshift Broad-Line Seyfert galaxies. While the optical/UV spectra of low to high redshift quasars look remarkably similar, we find a first indication of a difference in their X-ray spectrum. The steep X-ray spectral index suggests high Eddington ratios L/L_Edd. These observations give credence to the hypothesis of Mathur (2000) that NLS1s are low luminosity cousins of high redshift quasars, both likely to be in their early evolutionary stage.Comment: 25 pages, AJ, in press (Jan 2006

Time-optimal synthesis of unitary transformations in coupled fast and slow qubit system

In this paper, we study time-optimal control problems related to system of two coupled qubits where the time scales involved in performing unitary transformations on each qubit are significantly different. In particular, we address the case where unitary transformations produced by evolutions of the coupling take much longer time as compared to the time required to produce unitary transformations on the first qubit but much shorter time as compared to the time to produce unitary transformations on the second qubit. We present a canonical decomposition of SU(4) in terms of the subgroup SU(2)xSU(2)xU(1), which is natural in understanding the time-optimal control problem of such a coupled qubit system with significantly different time scales. A typical setting involves dynamics of a coupled electron-nuclear spin system in pulsed electron paramagnetic resonance experiments at high fields. Using the proposed canonical decomposition, we give time-optimal control algorithms to synthesize various unitary transformations of interest in coherent spectroscopy and quantum information processing.Comment: 8 pages, 3 figure