Connected Operators for the Totally Asymmetric Exclusion Process

We fully elucidate the structure of the hierarchy of the connected operators that commute with the Markov matrix of the Totally Asymmetric Exclusion Process (TASEP). We prove for the connected operators a combinatorial formula that was conjectured in a previous work. Our derivation is purely algebraic and relies on the algebra generated by the local jump operators involved in the TASEP. Keywords: Non-Equilibrium Statistical Mechanics, ASEP, Exact Results, Algebraic Bethe Ansatz.Comment: 10 page

A Monte-Carlo study of meanders

We study the statistics of meanders, i.e. configurations of a road crossing a river through "n" bridges, and possibly winding around the source, as a toy model for compact folding of polymers. We introduce a Monte-Carlo method which allows us to simulate large meanders up to n = 400. By performing large "n" extrapolations, we give asymptotic estimates of the connectivity per bridge R = 3.5018(3), the configuration exponent gamma = 2.056(10), the winding exponent nu = 0.518(2) and other quantities describing the shape of meanders. Keywords : folding, meanders, Monte-Carlo, treeComment: 12 pages, revtex, 11 eps figure

Random incidence matrices: moments of the spectral density

We study numerically and analytically the spectrum of incidence matrices of random labeled graphs on N vertices : any pair of vertices is connected by an edge with probability p. We give two algorithms to compute the moments of the eigenvalue distribution as explicit polynomials in N and p. For large N and fixed p the spectrum contains a large eigenvalue at Np and a semi-circle of "small" eigenvalues. For large N and fixed average connectivity pN (dilute or sparse random matrices limit), we show that the spectrum always contains a discrete component. An anomaly in the spectrum near eigenvalue 0 for connectivity close to e=2.72... is observed. We develop recursion relations to compute the moments as explicit polynomials in pN. Their growth is slow enough so that they determine the spectrum. The extension of our methods to the Laplacian matrix is given in Appendix. Keywords: random graphs, random matrices, sparse matrices, incidence matrices spectrum, momentsComment: 39 pages, 9 figures, Latex2e, [v2: ref. added, Sect. 4 modified

Family of Commuting Operators for the Totally Asymmetric Exclusion Process

The algebraic structure underlying the totally asymmetric exclusion process is studied by using the Bethe Ansatz technique. From the properties of the algebra generated by the local jump operators, we explicitly construct the hierarchy of operators (called generalized hamiltonians) that commute with the Markov operator. The transfer matrix, which is the generating function of these operators, is shown to represent a discrete Markov process with long-range jumps. We give a general combinatorial formula for the connected hamiltonians obtained by taking the logarithm of the transfer matrix. This formula is proved using a symbolic calculation program for the first ten connected operators. Keywords: ASEP, Algebraic Bethe Ansatz. Pacs numbers: 02.30.Ik, 02.50.-r, 75.10.Pq.Comment: 26 pages, 1 figure; v2: published version with minor changes, revised title, 4 refs adde

Core percolation in random graphs: a critical phenomena analysis

We study both numerically and analytically what happens to a random graph of average connectivity "alpha" when its leaves and their neighbors are removed iteratively up to the point when no leaf remains. The remnant is made of isolated vertices plus an induced subgraph we call the "core". In the thermodynamic limit of an infinite random graph, we compute analytically the dynamics of leaf removal, the number of isolated vertices and the number of vertices and edges in the core. We show that a second order phase transition occurs at "alpha = e = 2.718...": below the transition, the core is small but above the transition, it occupies a finite fraction of the initial graph. The finite size scaling properties are then studied numerically in detail in the critical region, and we propose a consistent set of critical exponents, which does not coincide with the set of standard percolation exponents for this model. We clarify several aspects in combinatorial optimization and spectral properties of the adjacency matrix of random graphs. Key words: random graphs, leaf removal, core percolation, critical exponents, combinatorial optimization, finite size scaling, Monte-Carlo.Comment: 15 pages, 9 figures (color eps) [v2: published text with a new Title and addition of an appendix, a ref. and a fig.

Did Growth and Reforms Increase Citizens’ Support for the Transition?

How did post-communist transformations affect people’s perceptions of their economic and political systems? We model a pseudo-panel with 89 country-year clusters, based on 13 countries observed between 1991 and 2004, to identify the macro and institutional drivers of the public opinion. Our main findings are: (i) When the economy is growing, on average people appreciate more extensive reforms; they dislike unbalanced reforms. (ii) Worsening of income distribution and higher inflation interact with an increasing share of the private sector in aggravating nostalgia for the past regime. (iii) Cross-country differences in the attitudes towards the present and future (both in the economic and political dimensions) are largely explained by differences in the institutional indicators for the rule of law and corruption. (iv) Cross-country differences in the extent of nostalgia towards the past are mainly related to differences in the deterioration of standards of living.

Real-time determinants of fiscal policies in the euro area: Fiscal rules, cyclical conditions and elections

We examine the impact of four factors on the fiscal policies of the euro-area countries over the last two decades: the state of public finances, the European fiscal rules, cyclical conditions and general elections. We rely on information actually available to policy-makers at the time of budgeting in constructing our explanatory variables. Our estimates indicate that policies have reacted to the state of public finances in a stabilizing manner. The European rules have significantly affected the behaviour of countries with excessive deficits. Apart from these cases, the rules appear to have reaffirmed existing preferences. We find a relatively large symmetrical counter-cyclical reaction of fiscal policy and strong evidence of a political budget cycle. The electoral manipulation of fiscal policy, however, occurs only if the macroeconomic context is favourable.fiscal policy, real-time information, euro-area countries, stabilisation policies, fiscal rules, political budget cycle

Did Growth and Reforms Increase Citizens' Support for the Transition?

How did post-communist transformations affect people's perceptions of their economic and political systems? We model a pseudo-panel with 89 country-year clusters, based on 13 countries observed between 1991 and 2004, to identify the macro and institutional drivers of the public opinion. Our main findings are: (i) When the economy is growing, on average people appreciate more extensive reforms; they dislike unbalanced reforms. (ii) Worsening of income distribution and higher inflation interact with an increasing share of the private sector in aggravating nostalgia for the past regime. (iii) Cross-country differences in the attitudes towards the present and future (both in the economic and political dimensions) are largely explained by differences in the institutional indicators for the rule of law and corruption. (iv) Cross-country differences in the extent of nostalgia towards the past are mainly related to differences in the deterioration of standards of living.economic performance, economic reforms, post-communist transition, political economy, support for reforms, public opinion