31 research outputs found
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]
VersiĂłn 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