Quantization of poisson pairs: the R-matrix approach

We suggest an approach to the quantization problem of two compatible Poisson brackets in the case when one of them is associated with a solution of the classical Yang-Baxter equation. We show that the quantization scheme (a Poisson bracket → an associate algebra, quantizing this bracket in the spirit of the Berezin-Lichnerovicz deformation quantization → its representation in a Hilbert space) has to be enlarged. We represent the deformation algebras, quantizing the "R-matrix" brackets, in a space with an S-symmetric pairing, where S is a solution of the corresponding quantum Yang-Baxter equation. An example of quantization of an "exotic" harmonic oscillator is discussed. © 1992

On the injectivity of the circular Radon transform arising in thermoacoustic tomography

The circular Radon transform integrates a function over the set of all spheres with a given set of centers. The problem of injectivity of this transform (as well as inversion formulas, range descriptions, etc.) arises in many fields from approximation theory to integral geometry, to inverse problems for PDEs, and recently to newly developing types of tomography. The article discusses known and provides new results that one can obtain by methods that essentially involve only the finite speed of propagation and domain dependence for the wave equation.Comment: To appear in Inverse Problem

Adaptive cluster expansion for the inverse Ising problem: convergence, algorithm and tests

We present a procedure to solve the inverse Ising problem, that is to find the interactions between a set of binary variables from the measure of their equilibrium correlations. The method consists in constructing and selecting specific clusters of variables, based on their contributions to the cross-entropy of the Ising model. Small contributions are discarded to avoid overfitting and to make the computation tractable. The properties of the cluster expansion and its performances on synthetic data are studied. To make the implementation easier we give the pseudo-code of the algorithm.Comment: Paper submitted to Journal of Statistical Physic

Comment on "Evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of El Hierro (Canary Islands, Spain)" by Pérez NM, Somoza L, Hernández PA, González de Vallejo L, León R, Sagiya T, Biain A, González FJ, Medialdea T, Barrancos J, Ibáñez J, Sumino H, Nogami K and Romero C [Bull Volcanol (2014) 76:882-896]

Versión del editor2,205

Noncommutative Gauge Theory without Lorentz Violation

The most popular noncommutative field theories are characterized by a matrix parameter theta^(mu,nu) that violates Lorentz invariance. We consider the simplest algebra in which the theta-parameter is promoted to an operator and Lorentz invariance is preserved. This algebra arises through the contraction of a larger one for which explicit representations are already known. We formulate a star product and construct the gauge-invariant Lagrangian for Lorentz-conserving noncommutative QED. Three-photon vertices are absent in the theory, while a four-photon coupling exists and leads to a distinctive phenomenology.Comment: 19 pages, 3 figures, revtex 4 (Version to appear in PRD

Towards evidence-based ICT policy and regulation

Meeting: Development of an Equitable Information Society : the Role of African Parliaments; international conference, Kigali, Rwanda, 4th-5th March 2009PowerPoint presentationIn the absence of data and analysis required for evidence-based policy, Research ICT Africa (RIA) is a network of researchers conducting ICT policy and regulatory research in 20 African countries across the continent. The presentation gives an overview of current conditions for research, and the context for development of ICT policy and regulation. It provides country statistics and analyses on customer expenditures and willingness to pay, as well as mobile pricing, Internet access and usage. Recommendations include development of institutional arrangements and transparent administrative procedures that allow for clear division of policy, regulatory and operational function

Quantization of poisson pairs: the R-matrix approach

We suggest an approach to the quantization problem of two compatible Poisson brackets in the case when one of them is associated with a solution of the classical Yang-Baxter equation. We show that the quantization scheme (a Poisson bracket → an associate algebra, quantizing this bracket in the spirit of the Berezin-Lichnerovicz deformation quantization → its representation in a Hilbert space) has to be enlarged. We represent the deformation algebras, quantizing the "R-matrix" brackets, in a space with an S-symmetric pairing, where S is a solution of the corresponding quantum Yang-Baxter equation. An example of quantization of an "exotic" harmonic oscillator is discussed. © 1992