Asymptotic upper bounds for the coefficients

in the Chebyshev series expansion

for a general order integral of a function

Author:
Natasha Flyer

Journal:
Math. Comp. **67** (1998), 1601-1616

MSC (1991):
Primary 42C10

DOI:
https://doi.org/10.1090/S0025-5718-98-00976-4

MathSciNet review:
1474651

Full-text PDF

Abstract | References | Similar Articles | Additional Information

Abstract: The usual way to determine the asymptotic behavior of the Chebyshev coefficients for a function is to apply the method of steepest descent to the integral representation of the coefficients. However, the procedure is usually laborious. We prove an asymptotic upper bound on the Chebyshev coefficients for the integral of a function. The tightness of this upper bound is then analyzed for the case , the first integral of a function. It is shown that for geometrically converging Chebyshev series the theorem gives the tightest upper bound possible as . For functions that are singular at the endpoints of the Chebyshev interval, , the theorem is weakened. Two examples are given. In the first example, we apply the method of steepest descent to directly determine (laboriously!) the asymptotic Chebyshev coefficients for a function whose asymptotics have not been given previously in the literature: a Gaussian with a maximum at an endpoint of the expansion interval. We then easily obtain the asymptotic behavior of its first integral, the error function, through the application of the theorem. The second example shows the theorem is weakened for functions that are regular except at . We conjecture that it is only for this class of functions that the theorem gives a poor upper bound.

**1.**M. Abramowitz and I.A. Stegun*Handbook of Mathematical Functions*, Dover, New York, 1972. MR**94b:00012****2.**T.M. Apostol*Mathematical Analysis*, Addison-Wesley, Reading, Massachusetts, 1974. MR**49:9123****3.**C.M. Bender and S. Orszag,*Advanced Mathematical Methods for Scientists and Engineers*, McGraw-Hill, New York, 1978. MR**80d:00030****4.**J.P. Boyd,*The rate of convergence of Fourier coefficients for entire functions of infinite order with application to the Weideman-Cloot sinh-mapping for pseudospectral computations on an infinite interval*, J. Comp. Phys. vol. 110, 1994, pp. 360-375. CMP**94:10****5.**J.P. Boyd,*Asymptotic coefficients of Hermite Function Series*, J. Comp. Phys. vol. 54, 1984, pp. 382-410. MR**86c:41012****6.**J.P. Boyd,*Chebyshev and Fourier Spectral Methods*, Springer-Verlag, New York, 1989.**7.**D. Elliott and G. Szekeres,*Some estimates of the coefficients in the Chebyshev series expansion of a function*Math. Comp. vol. 19, 1965, pp. 25-32. MR**30:2666****8.**D. Elliott,*The evaluation and estimation of the coefficients in the Chebyshev series expansion of a function*Math. Comp. vol. 18, 1964, pp. 274-281. MR**29:4176****9.**L. Fox and I.B. Parker,*Chebyshev Polynomials in Numerical Analysis*, Oxford University Press, London, 1968. MR**37:3733**

Retrieve articles in *Mathematics of Computation of the American Mathematical Society*
with MSC (1991):
42C10

Retrieve articles in all journals with MSC (1991): 42C10

Additional Information

**Natasha Flyer**

Affiliation:
Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48105

Email:
nflyer@engin.umich.edu

DOI:
https://doi.org/10.1090/S0025-5718-98-00976-4

Keywords:
Chebyshev series

Received by editor(s):
September 20, 1996

Received by editor(s) in revised form:
March 3, 1997

Additional Notes:
The author would like to express her deep appreciation and gratitude for the valuable discussions and comments of Prof. John P. Boyd at the University of Michigan. This work was supported by NASA Grant NGT-51409.

Article copyright:
© Copyright 1998
American Mathematical Society