13,194 research outputs found
On the algebraic Bethe ansatz: Periodic boundary conditions
In this paper, the algebraic Bethe ansatz with periodic boundary conditions
is used to investigate trigonometric vertex models associated with the
fundamental representations of the non-exceptional Lie algebras. This
formulation allow us to present explicit expressions for the eigenvectors and
eigenvalues of the respective transfer matrices.Comment: 36 pages, LaTex, Minor Revisio
Inflationary Models Driven by Adiabatic Matter Creation
The flat inflationary dust universe with matter creation proposed by
Prigogine and coworkers is generalized and its dynamical properties are
reexamined. It is shown that the starting point of these models depends
critically on a dimensionless parameter , closely related to the matter
creation rate . For bigger or smaller than unity flat universes
can emerge, respectively, either like a Big-Bang FRW singularity or as a
Minkowski space-time at . The case corresponds to a de
Sitter-type solution, a fixed point in the phase diagram of the system,
supported by the matter creation process. The curvature effects have also been
investigated. The inflating de Sitter is a universal attractor for all
expanding solutions regardless of the initial conditions as well as of the
curvature parameter.Comment: 25 pages, 2 figures(available from the authors), uses LATE
Exact Lyapunov Exponent for Infinite Products of Random Matrices
In this work, we give a rigorous explicit formula for the Lyapunov exponent
for some binary infinite products of random real matrices. All
these products are constructed using only two types of matrices, and ,
which are chosen according to a stochastic process. The matrix is singular,
namely its determinant is zero. This formula is derived by using a particular
decomposition for the matrix , which allows us to write the Lyapunov
exponent as a sum of convergent series. Finally, we show with an example that
the Lyapunov exponent is a discontinuous function of the given parameter.Comment: 1 pages, CPT-93/P.2974,late
Clustering, Angular Size and Dark Energy
The influence of dark matter inhomogeneities on the angular size-redshift
test is investigated for a large class of flat cosmological models driven by
dark energy plus a cold dark matter component (XCDM model). The results are
presented in two steps. First, the mass inhomogeneities are modeled by a
generalized Zeldovich-Kantowski-Dyer-Roeder (ZKDR) distance which is
characterized by a smoothness parameter and a power index ,
and, second, we provide a statistical analysis to angular size data for a large
sample of milliarcsecond compact radio sources. As a general result, we have
found that the parameter is totally unconstrained by this sample of
angular diameter data.Comment: 9 pages, 7 figures, accepted in Physical Review
Differences in the Prevalence of Non-Communicable Disease between Slum Dwellers and the General Population in a Large Urban Area in Brazil.
Residents of urban slums are at greater risk for disease than their non-slum dwelling urban counterparts. We sought to contrast the prevalences of selected non-communicable diseases (NCDs) between Brazilian adults living in a slum and the general population of the same city, by comparing the age and sex-standardized prevalences of selected NCDs from a 2010 survey in Pau da Lima, Salvador Brazil, with a 2010 national population-based telephone survey. NCD prevalences in both populations were similar for hypertension (23.6% (95% CI 20.9⁻26.4) and 22.9% (21.2⁻24.6), respectively) and for dyslipidemia (22.7% (19.8⁻25.5) and 21.5% (19.7⁻23.4)). Slum residents had higher prevalences of diabetes mellitus (10.1% (7.9⁻12.3)) and of overweight/obesity (46.5% (43.1⁻49.9)), compared to 5.2% (4.2⁻6.1) and 40.6% (38.5⁻42.8) of the general population in Salvador. Fourteen percent (14.5% (12.1⁻17.0)) of slum residents smoked cigarettes compared to 8.3% (7.1⁻9.5) of the general population in Salvador. The national telephone survey underestimated the prevalence of diabetes mellitus, overweight/obesity, and smoking in the slum population, likely in part due to differential sampling inside and outside of slums. Further research and targeted policies are needed to mitigate these inequalities, which could have significant economic and social impacts on slum residents and their communities
Exact Curie temperature for the Ising model on Archimedean and Laves lattices
Using the Feynman-Vdovichenko combinatorial approach to the two dimensional
Ising model, we determine the exact Curie temperature for all two dimensional
Archimedean lattices. By means of duality, we extend our results to cover all
two dimensional Laves lattices. For those lattices where the exact critical
temperatures are not exactly known yet, we compare them with Monte Carlo
simulations.Comment: 10 pages, 1 figures, 3 table
Gaudin model and its associated Knizhnik-Zamolodchikov equation
The semiclassical limit of the algebraic Bethe Ansatz for the Izergin-Korepin
19-vertex model is used to solve the theory of Gaudin models associated with
the twisted R-matrix. We find the spectra and eigenvectors of the
independents Gaudin Hamiltonians. We also use the off-shell Bethe Ansatz
method to show how the off-shell Gaudin equation solves the associated
trigonometric system of Knizhnik-Zamolodchikov equations.Comment: 20 pages,no figure, typos corrected, LaTe
- …