The Strong-Coupling Expansion in Simplicial Quantum Gravity

We construct the strong-coupling series in 4d simplicial quantum gravity up to volume 38. It is used to calculate estimates for the string susceptibility exponent gamma for various modifications of the theory. It provides a very efficient way to get a first view of the phase structure of the models.Comment: LATTICE98(surfaces), 3 pages, 4 eps figure

Stability of the Kauffman Model

Random Boolean networks, the Kauffman model, are revisited by means of a novel decimation algorithm, which reduces the networks to their dynamical cores. The average size of the removed part, the stable core, grows approximately linearly with N, the number of nodes in the original networks. We show that this can be understood as the percolation of the stability signal in the network. The stability of the dynamical core is investigated and it is shown that this core lacks the well known stability observed in full Kauffman networks. We conclude that, somewhat counter-intuitive, the remarkable stability of Kauffman networks is generated by the dynamics of the stable core. The decimation method is also used to simulate large critical Kauffman networks. For networks up to N=32 we perform full enumeration studies. Strong evidence is provided for that the number of limit cycles grows linearly with N. This result is in sharp contrast to the often cited $\sqrt{N}$ behavior.Comment: 12 pages, 4 figure

Break in the mean and persistence of inflation: a sectoral analysis of French CPI

This paper uses disaggregated CPI time series to show that a break in the mean of French inflation occurred in the mid-eighties and that the 1983 monetary policy shift mostly accounted for it. CPI average yearly growth declined from nearly 11% before the break date (May 1985) to 2.1% after. No other break in the 1973-2004 sample period can be found. Controlling for this mean break, both aggregate and sectoral inflation persistence are stable and low, with the unit root lying far in the tail of the persistence estimates. However, persistence differs dramatically across sectors. Finally, the duration between two price changes (at the firm level) appears positively related with inflation persistence (at the aggregate level). JEL Classification: E31, C12, C22Inflation persistence, monetary policy, multiple breaks test, sectoral prices

Random manifolds and quantum gravity

The non-perturbative, lattice field theory approach towards the quantization of Euclidean gravity is reviewed. Included is a tentative summary of the most significant results and a presentation of the current state of art.Comment: invited plenary talk at LATTICE '99 (Pisa), latex 5p

The Weak-Coupling Limit of 3D Simplicial Quantum Gravity

We investigate the weak-coupling limit, kappa going to infinity, of 3D simplicial gravity using Monte Carlo simulations and a Strong Coupling Expansion. With a suitable modification of the measure we observe a transition from a branched polymer to a crinkled phase. However, the intrinsic geometry of the latter appears similar to that of non-generic branched polymer, probable excluding the existence of a sensible continuum limit in this phase.Comment: 3 pages 4 figs. LATTICE99(Gravity

A persistence-weighted measure of core inflation in the euro area

We propose a new core inflation measure for the Euro area which places the emphasis on the more lasting, i.e. persistent, price developments at a disaggregated level. The importance of each component of the HICP is reweighted according to its relative persistence, as measured by the sum of the autoregressive coefficients or by an indicator of mean reversion. Unlike headline inflation, our baseline core inflation measure is highly correlated with ECB monetary policy decisions, which could mean that it contains ex ante (pre monetary policy) information on inflationary pressure. JEL Classification: E31core inflation, inflation persistence

Phase Transition of 4D Simplicial Quantum Gravity with U(1) Gauge Field

The phase transition of 4D simplicial quantum gravity coupled to U(1) gauge fields is studied using Monte-Carlo simulations. The phase transition of the dynamical triangulation model with vector field ($N_{V}=1$) is smooth as compared with the pure gravity($N_{V}=0$). The node susceptibility ($\chi$) is studied in the finite size scaling method. At the critical point, the node distribution has a sharp peak in contrast to the double peak in the pure gravity. From the numerical results, we expect that 4D simplicial quantum gravity with U(1) vector fields has higher order phase transition than 1st order, which means the possibility to take the continuum limit at the critical point.Comment: 3 pages, latex, 3 eps figures, uses espcrc2.sty. Talk presented at LATTICE99(gravity