71,971 research outputs found

    The relative dynamics of investment and the current account in the G-7 economies

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    This paper contributes to the empirics of the intertemporal approach to the current account. We use a cointegrated VAR framework to identify permanent and transitory components of country-specific and global shocks. Our approach allows us to empirically investigate the sensitivity to persistence implied by many forward-looking models and our results shed new light on the excess volatility of investment encountered by Glick and Rogoff (JME 1995). In G7 data, we find the relative current-account and investment response to be in line with the intertemporal approach

    q-Deformed Relativistic Wave Equations

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    Based on the representation theory of the qq-deformed Lorentz and Poincar\'e symmeties qq-deformed relativistic wave equation are constructed. The most important cases of the Dirac-, Proca-, Rarita-Schwinger- and Maxwell- equations are treated explicitly. The qq-deformed wave operators look structurally like the undeformed ones but they consist of the generators of a non-commu\-ta\-tive Minkowski space. The existence of the qq-deformed wave equations together with previous existence of the qq-deformed wave equations together with previous results on the representation theory of the qq-deformed Poincar\'e symmetry solve the qq-deformed relativistic one particle problem.Comment: 17 Page

    Strong characterizing sequences of countable groups

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    Andr\'as Bir\'o and Vera S\'os prove that for any subgroup GG of \T generated freely by finitely many generators there is a sequence ANA\subset \N such that for all \beta \in \T we have (.\|.\| denotes the distance to the nearest integer) βGnAnβ<,βGlim supnA,nnβ>0.\beta\in G \Rightarrow \sum_{n\in A} \| n \beta\| < \infty,\quad \quad \quad \beta\notin G \Rightarrow \limsup_{n\in A, n \to \infty} \|n \beta\| > 0. We extend this result to arbitrary countable subgroups of \T. We also show that not only the sum of norms but the sum of arbitrary small powers of these norms can be kept small. Our proof combines ideas from the above article with new methods, involving a filter characterization of subgroups of \T

    A NN-uniform quantitative Tanaka's theorem for the conservative Kac's NN-particle system with Maxwell molecules

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    This paper considers the space homogenous Boltzmann equation with Maxwell molecules and arbitrary angular distribution. Following Kac's program, emphasis is laid on the the associated conservative Kac's stochastic NN-particle system, a Markov process with binary collisions conserving energy and total momentum. An explicit Markov coupling (a probabilistic, Markovian coupling of two copies of the process) is constructed, using simultaneous collisions, and parallel coupling of each binary random collision on the sphere of collisional directions. The euclidean distance between the two coupled systems is almost surely decreasing with respect to time, and the associated quadratic coupling creation (the time variation of the averaged squared coupling distance) is computed explicitly. Then, a family (indexed by δ>0\delta > 0) of NN-uniform ''weak'' coupling / coupling creation inequalities are proven, that leads to a NN-uniform power law trend to equilibrium of order t+tδ{\sim}_{ t \to + \infty} t^{-\delta} , with constants depending on moments of the velocity distributions strictly greater than 2(1+δ)2(1 + \delta). The case of order 44 moment is treated explicitly, achieving Kac's program without any chaos propagation analysis. Finally, two counter-examples are suggested indicating that the method: (i) requires the dependance on >2>2-moments, and (ii) cannot provide contractivity in quadratic Wasserstein distance in any case.Comment: arXiv admin note: text overlap with arXiv:1312.225
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