12.07.2015 Views

Ivancevic_Applied-Diff-Geom

Ivancevic_Applied-Diff-Geom

Ivancevic_Applied-Diff-Geom

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

1078 <strong>Applied</strong> <strong>Diff</strong>erential <strong>Geom</strong>etry: A Modern Introductionmanifold M is the configuration space R N and the natural choice for theMorse function is the potential V (q). Hence, one is lead to define the familyM v (6.114) of submanifolds of M.A full characterization of the topological properties of M v generallyrequires the critical points of V (q), which means solving the equations∂ q iV = 0, (i = 1, . . . , N). (6.123)Moreover, one has to calculate the indexes of all the critical points, thatis the number of negative eigenvalues of the Hessian ∂ 2 V/(∂q i ∂q j ). Thenthe Euler characteristic χ(M v ) can be computed by means of the formulaχ(M v ) =N∑(−1) k µ k (M v ), (6.124)k=0where µ k (M v ) is the total number of critical points of V (q) on M v whichhave index k, i.e., the so–called Morse numbers of a manifold M, whichhappen to be upper bounds of the Betti numbers,b k (M) ≤ µ k (M) (k = 0, . . . , n). (6.125)Among all the Morse functions on a manifold M, there is a special class,called perfect Morse functions, for which the Morse inequalities (6.125) holdas equalities. Perfect Morse functions characterize completely the topologyof a manifold.Now, we continue with our two examples started before.Peyrard–Bishop System. If applied to any generic model, calculationof (6.124) turns out to be quite formidable, but the exceptional simplicity ofthe Peyrard–Bishop model (6.119) makes it possible to carry on completelythe topological analysis without invoking equation (6.124).For the potential in exam, equation (6.123) results in the nonlinearsystemaR (qi+1 − 2q i + q i−1 ) = h − 2(e −2aqi − e −aqi ),where R = Da 2 /K is a dimensionless ratio.particular solution is given byIt is easy to verify that aq i = − 1 a ln 1 + √ 1 + 2h, (i = 1, . . . , N).2

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!