25 research outputs found
Quantitative predictions with detuned normal forms
The phase-space structure of two families of galactic potentials is
approximated with a resonant detuned normal form. The normal form series is
obtained by a Lie transform of the series expansion around the minimum of the
original Hamiltonian. Attention is focused on the quantitative predictive
ability of the normal form. We find analytical expressions for bifurcations of
periodic orbits and compare them with other analytical approaches and with
numerical results. The predictions are quite reliable even outside the
convergence radius of the perturbation and we analyze this result using
resummation techniques of asymptotic series.Comment: Accepted for publication on Celestial Mechanics and Dynamical
Astronom
Casimir Effect in 2D Stringy Black Hole Backgrounds
We consider the two-dimensional "Schwarzschild" and "Reissner-Nordstrom"
stringy black holes as systems of Casimir type. We explicitly calculate the
energy-momentum tensor of a massless scalar field satisfying Dirichlet boundary
conditions on two one-dimensional "walls". These results are obtained using the
Wald's axioms. Thermodynamical quantities such as pressure, specific heat,
isothermal compressibility and entropy of the two-dimensional stringy black
holes are calculated. A comparison is made between the obtained results and the
laws of thermodynamics. The results obtained for the extremal (Q=M) stringy
two-dimensional charged black hole are identical in all three different vacua
used; a fact that indicates its quantum stability.Comment: RevTeX, 27 pages, no figures, to appear in Phys.Rev. D, Vol 64 (Dec.
2001