Bounds for the expected value of one-step processes

Mean-field models are often used to approximate Markov processes with large state-spaces. One-step processes, also known as birth-death processes, are an important class of such processes and are processes with state space $\{0,1,\ldots,N\}$ and where each transition is of size one. We derive explicit bounds on the expected value of such a process, bracketing it between the mean-field model and another simple ODE. Our bounds require that the Markov transition rates are density dependent polynomials that satisfy a sign condition. We illustrate the tightness of our bounds on the SIS epidemic process and the voter model.Comment: 14 pages, 4 figures, revise

Isotopic and velocity distributions of Bi produced in charge-pickup reactions of 208Pb at 1 A GeV

Isotopically resolved cross sections and velocity distributions have been measured in charge-pickup reactions of 1 A GeV 208Pb with proton, deuterium and titanium target. The total and partial charge-pickup cross sections in the reactions 208Pb + 1H and 208Pb + 2H are measured to be the same in the limits of the error bars. A weak increase in the total charge-pickup cross section is seen in the reaction of 208Pb with the titanium target. The measured velocity distributions show different contributions - quasi-elastic scattering and Delta-resonance excitation - to the charge-pickup production. Data on total and partial charge-pickup cross sections from these three reactions are compared with other existing data and also with model calculations based on the coupling of different intra-nuclear cascade codes and an evaporation code.Comment: 20 pages, 12 figures, background information on http://www-w2k.gsi.de/kschmidt

Sensitivity to the KARMEN Timing Anomaly at MiniBooNE

We present sensitivities for the MiniBooNE experiment to a rare exotic pion decay producing a massive particle, Q^0. This type of decay represents one possible explanation for the timing anomaly reported by the KARMEN collaboration. MiniBooNE will be able to explore an area of the KARMEN signal that has not yet been investigated

Measurement of the complete nuclide production and kinetic energies of the system 136Xe + hydrogen at 1 GeV per nucleon

We present an extensive overview of production cross sections and kinetic energies for the complete set of nuclides formed in the spallation of 136Xe by protons at the incident energy of 1 GeV per nucleon. The measurement was performed in inverse kinematics at the FRagment Separator (GSI, Darmstadt). Slightly below the Businaro-Gallone point, 136Xe is the stable nuclide with the largest neutron excess. The kinematic data and cross sections collected in this work for the full nuclide production are a general benchmark for modelling the spallation process in a neutron-rich nuclear system, where fission is characterised by predominantly mass-asymmetric splits.Comment: 18 pages, 14 figure

Seismicity and fault interaction, Southern San Jacinto Fault Zone and adjacent faults, southern California: Implications for seismic hazard

The southern San Jacinto fault zone is characterized by high seismicity and a complex fault pattern that offers an excellent setting for investigating interactions between distinct faults. This fault zone is roughly outlined by two subparallel master fault strands, the Coyote Creek and Clark-San Felipe Hills faults, that are located 2 to 10 km apart and are intersected by a series of secondary cross faults. Seismicity is intense on both master faults and secondary cross faults in the southern San Jacinto fault zone. The seismicity on the two master strands occurs primarily below 10 km; the upper 10 km of the master faults are now mostly quiescent and appear to rupture mainly or solely in large earthquakes. Our results also indicate that a considerable portion of recent background activity near the April 9, 1968, Borrego Mountain rupture zone (M_L=6.4) is located on secondary faults outside the fault zone. We name and describe the Palm Wash fault, a very active secondary structure located about 25 km northeast of Borrego Mountain that is oriented subparallel to the San Jacinto fault system, dips approximately 70° to the northeast, and accommodates right-lateral shear motion. The Vallecito Mountain cluster is another secondary feature delineated by the recent seismicity and is characterized by swarming activity prior to nearby large events on the master strand. The 1968 Borrego Mountain and the April 28, 1969, Coyote Mountain (M_L=5.8) events are examples of earthquakes with aftershocks and subevents on these secondary and master faults. Mechanisms from those earthquakes and recent seismic data for the period 1981 to 1986 are not simply restricted to strike-slip motion; dipslip motion is also indicated. Teleseismic body waves (long-period P and SH) of the 1968 and 1969 earthquakes were inverted simultaneously for source mechanism, seismic moment, rupture history, and centroid depth. The complicated waveforms of the 1968 event (M_o=1.2 × 10^(19) Nm) are interpreted in terms of two subevents; the first caused by right-lateral strike-slip motion in the mainshock along the Coyote Creek fault and the second by a rupture located about 25 km away from the master fault. Our waveform inversion of the 1969 event indicates that strike-slip motion predominated, releasing a seismic moment of 2.5 × 10^(17) Nm. Nevertheless, the right-lateral nodal plane of the focal mechanism is significantly misoriented (20°) with respect to the master fault, and hence the event is not likely to be associated with a rupture on that fault. From this and other examples in southern California, we conclude that cross faults may contribute significantly to seismic hazard and that interaction between faults has important implications for earthquake prediction

Transport and dynamical properties of inertial ratchets

In this paper we discuss the dynamics and transport properties of a massive particle, in a time dependent periodic potential of the ratchet type, with a dissipative environment. The directional currents and characteristics of the motion are studied as the specific frictional coefficient varies, finding that the stationary regime is strongly dependent on this parameter. The maximal Lyapunov exponent and the current show large fluctuations and inversions, therefore for some range of the control parameter, this inertial ratchet could originate a mass separation device. Also an exploration of the effect of a random force on the system is performed.Comment: PDF, 16 pages, 7 figure

Scaling Laws and Transient Times in 3He Induced Nuclear Fission

Fission excitation functions of compound nuclei in a mass region where shell effects are expected to be very strong are shown to scale exactly according to the transition state prediction once these shell effects are accounted for. The fact that no deviations from the transition state method have been observed within the experimentally investigated excitation energy regime allows one to assign an upper limit for the transient time of 10 zs.Comment: 7 pages, TeX type, psfig, submitted to Phys. Rev. C, also available at http://csa5.lbl.gov/moretto/ps/he3_paper.p