1. I N T R O D U C T I O N (1.1) Cluster algebras are a class of commutative algebras defined by a three step process. The first step is to specify an initial seed s, that is some set of initial generators of an ambient field F . Second, a subset X of F is constructed by mutating the initial seed s, mutating the resulting seeds, mutating the result of those mutations, and so forth ad infinitum....

Deog Ki Hong and Stephen D.H. Hsu 1 Department of Physics, Pusan National University, Pusan 609-735, Korea [email protected] 2 Department of Physics, University of Oregon, Eugene OR 97403-5203 [email protected] (Dated: June 4, 2005) Abstract We elaborate on previous results concerning the positivity of the Euclidean path integral measure for low-energy modes in dense fermionic matter. We ...

The q-binomial coefficients [ n m ] = ∏m i=1(1 − qn−m+i)/(1 − q), for integers 0 ≤ m ≤ n, are known to be polynomials with non-negative integer coefficients. This readily follows from the q-binomial theorem, or the many combinatorial interpretations of [ n m ] . In this note we conjecture an arithmetically motivated generalisation of the non-negativity property for products of ratios of q-facto...

We study the modified dynamical evolution of the neutral kaon system under the condition of complete positivity. The accuracy of the data from planned future experiments is expected to be sufficiently precise to test such a hypothesis.

Positivity, or the experimental treatment assignment assumption, requires that there be both exposed and unexposed participants at every combination of the values of the observed confounders in the population under study. Positivity is essential for inference but is often overlooked in practice by epidemiologists. This issue of the Journal includes 2 articles featuring discussions related to po...

OBJECTIVE We examined the effects of control motivation on in-group positivity. Past research suggests that people compensate for low personal control by increasing support for social in-groups. We predicted that the effect of personal control on in-group positivity would depend on the type of in-group positivity. Low personal control should increase compensatory, narcissistic in-group positivi...

We construct a local Lax-Friedrichs type positivity-preserving flux for compressible Navier-Stokes equations, which can be easily extended to high dimensions for generic forms of equations of state, shear stress tensor and heat flux. With this positivity-preserving flux, any finite volume type schemes including discontinuous Galerkin (DG) schemes with strong stability preserving Runge-Kutta tim...