251 research outputs found
Quasilinearization Method and Summation of the WKB Series
Solutions obtained by the quasilinearization method (QLM) are compared with
the WKB solutions. Expansion of the -th QLM iterate in powers of
reproduces the structure of the WKB series generating an infinite number of the
WKB terms with the first terms reproduced exactly. The QLM quantization
condition leads to exact energies for the P\"{o}schl-Teller, Hulthen,
Hylleraas, Morse, Eckart potentials etc. For other, more complicated potentials
the first QLM iterate, given by the closed analytic expression, is extremely
accurate. The iterates converge very fast. The sixth iterate of the energy for
the anharmonic oscillator and for the two-body Coulomb Dirac equation has an
accuracy of 20 significant figures
Covariant Hamiltonian Dynamics with Negative Energy States
A relativistic quantum mechanics is studied for bound hadronic systems in the
framework of the Point Form Relativistic Hamiltonian Dynamics. Negative energy
states are introduced taking into account the restrictions imposed by a correct
definition of the Poincar\'e group generators. We obtain nonpathological,
manifestly covariant wave equations that dynamically contain the contributions
of the negative energy states. Auxiliary negative energy states are also
introduced, specially for studying the interactions of the hadronic systems
with external probes.Comment: 42 pages, submitted to EPJ
Analytic calculation of energies and wave functions of the quartic and pure quartic oscillators
Ground state energies and wave functions of quartic and pure quartic
oscillators are calculated by first casting the Schr\"{o}dinger equation into a
nonlinear Riccati form and then solving that nonlinear equation analytically in
the first iteration of the quasilinearization method (QLM). In the QLM the
nonlinear differential equation is solved by approximating the nonlinear terms
by a sequence of linear expressions. The QLM is iterative but not perturbative
and gives stable solutions to nonlinear problems without depending on the
existence of a smallness parameter. Our explicit analytic results are then
compared with exact numerical and also with WKB solutions and it is found that
our ground state wave functions, using a range of small to large coupling
constants, yield a precision of between 0.1 and 1 percent and are more accurate
than WKB solutions by two to three orders of magnitude. In addition, our QLM
wave functions are devoid of unphysical turning point singularities and thus
allow one to make analytical estimates of how variation of the oscillator
parameters affects physical systems that can be described by the quartic and
pure quartic oscillators.Comment: 8 pages, 12 figures, 1 tabl
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